Monday Afternoon Technical Discussion

Synopsis:

A few showers (mostly of the "rain" variety) will cross the state overnight, most of them remaining west of I-99. Skies will clear out on Tuesday, setting up a rather pleasant week, weather wise, with the exception of a system that may or may not drop some rain on the state on Friday.

Short-Term:

Some scattered showers are likely to pass through the area as we go through the overnight hours. The current satellite imagery shows rather thick cloud cover across the state, while radar images show a few showers already working across the western half of PA. These showers are likely to only remain in that part of the state, as the moisture will likely diminish as the piece of energy moves farther east overnight. Thus, the greatest chance for showers (likely rain showers in most locations, though a few of the higher ridges could drop off enough to see a few snow flurries) will be west of I-99.

Conditions should improve by Tuesday morning, with the state primarily under the influence of high pressure off to the east. Clouds will be on the decrease as we go throughout the day.

Long-Term:

The pleasant weather conditions will continue on Wednesday, as high pressure continues to hang around the Northeast. Most models are in agreement that skies will be clear through Thursday morning at the earliest. These clear skies should also allow temperatures to moderate to near-normal or slightly above-normal ranges. Disagreement between the WRF and some of the longer-range models, specifically the GFS and ECMWF, begins on Thursday and last into the weekend (or at least the end of the WRF's forecast period) over a vort. max setting up off to the west beginning on Thursday. The GFS and European models both show the vort. max diving to the south and keeping Pennsylvania dry on Friday, but do bring a few clouds in along a diagonal line on Thursday. The WRF, on the other hand, keeps Pennsylvania more clear on Thursday, but does look likely to drop rainfall across the state on Friday. Analysis of future runs will be necessary to make a more confident decision, but at this point, we sided with the longer-term models. The weekend appears to be shaping up nicely, with mostly clear skies as we avoid a trough which will cross New England early Saturday.

-Devin Boyer

Sunday Afternoon Technical Discussion

Synopsis: High pressure for tonight through early tomorrow. Cold front affecting Wrn PA on Mon. night. Nor'easter passing well offshore Tues. AM. High pressure in control from Tues. evening through Wed. at 2400 local time. Weak cold front moving through on Thursday.

Short-term: The 12Z WRF-NAM and 12Z GFS agree that the cold front will pas through PA but will dry out. Cloud cover will be the main story with this. The same models also agree that the nor'easter's moisture will stay in NJ. A sprinkle is possible in Philly but mostly cloud cover to the east. All this because the cold front is pushing the system out to sea.

Long-range: The GFS says that we will be between high pressure systems on Thursday. We will probably see rain with this system but not amounting to much (so far).

Other notes: We looked at the 3Z & 9Z SREF panels and the timing of the first front is not too compatible with the GFS. There will be no wind <15 mph or wintry precipitation according to the SREFs... not even in the higher elevations. Thursday's front, given that is is about 4 days away, will need to be watched.

-Jaron Breen

Thursday Evening Technical Discussion

Synopsis

High pressure will build into the area from the west and dominate our weather through Friday evening. An area of low pressure over the Southeast will begin to move northeast and eventually off the southeast coast and strengthen as it moves north along the east coast. This will bring precipitation, possibly in the form heavy wet snow to most of the southeastern areas of Pennsylvania. Behind this low pressure, high pressure will build northeast from the Tennessee Valley for Sunday with clearing skies. Another shortwave associated with clouds approached on Monday into Tuesday before high pressure builds in mid-week.

Short Term (Through Saturday morning)

Cold air will continue seep down into the area overnight as evidenced by some higher elevations near Bradford and Dubois reporting snow throughout the day.  As skies continue to clear out tonight due to dry northwesterly flow, temperatures will fall below freezing with some location reporting lows in the upper 20's. There are already many frost advisories out for parts of the commonwealth and the potential for fog in many of the central PA valley. Friday is going to be very chilly as skies remain mostly cloud which will limit solar heating potential. As a low pressure system over Virginia begins to move northwards, skies will become cloudy overnight into Saturday morning.

Mid-Term (Saturday morning –Sunday evening)

This low pressure will rapidly strengthen once it makes it way off the coast of Delaware. Precipitation associated with this low pressure will begin to spread into the southeastern regions of PA earl Saturday morning. The initial precipitation will begin as rain, but as we go later in Saturday, the rain will change to heavy wet snow. The heaviest precipitation will occur during the day Saturday as the 850 mb low strengthens off the Delaware coast. There is definitely the potential for some significant snow accumulations in the eastern regions of PA particularly in the Lehigh valley and southeast toward Philly. The GFS, Euro, and SREF's have reached a decent consensus that this low will take a track that is conducive to heavy wintry precipitation over these regions of PA. However, there will be a particularly sharp gradient in the precipitation amounts with places near State College receiving only flurries Saturday afternoon. Precipitation will generally increase as one moves toward the PA/NJ border. Precipitation will continue to fall Saturday night in to Sunday morning before tapering off on Sunday. In the end, there is still some uncertainty with regards to the exact track of this system, so I will hold out on specific snowfall amounts.

Long Term (Sunday-Wednesday)

Sunday will remain cloudy and cold as the low pressure moves off to the northeast and we are dominated by cold air advection. High pressure will build in on Sunday and promote clearing skies and allow our temperatures to moderate. However, late Monday, another shortwave approaching from the northwest will bring increased cloud cover and the chance for some precipitation. Behind this shortwave, another ridge of high pressure will build and allow our temperatures to approach normal again before a cold front approaches late in the period.

-Matt Mehallow

Wednesday Night

Synopsis: A much cooler weather pattern is in store for us over the next few days. A disturbance will move through the region tonight and tomorrow bringing a round of showers with a possible snow shower or two. Much cooler temperatuers will follow this system. A relatively strong system will track along the East Coast this weekend, showers may be possible in the very eastern parts of the state. As we are caught in between systems conditions will be generally cool and cloudy. 

 

Short term: The low pressure system to our west will continue to trek east bringing the Commonwealth a round of showers. A cold front associated with this system will move through the region during the day tomorrow. As this front passes a brief changeover to snow can be expected Thursday evening, especially in the mountains.  Precipitation should clear out by Friday allowing for the sun to briefly peak out. A northwesterly flow will dominate the weather pattern, filtering in much cooler air from the north. Besides a brief stint at sun on Friday, cloudy skies should be dominant this weekend. On Saturday a shortwave will move across the Great Lakes, producing some potential snow showers in the northwestern regions of the state.

 

Long term: Mainly dry and cool conditions will dominate the forecast later this weekend and early next week. Winds will be generally coming out of northwest during this time period. This will produce generally cloudy conditions, as well as a possible lake effect snow shower.

 

Dakota Smith

Wednesday Midday

Synopsis:  The calm before the storms…  Three waves will affect the region through Saturday night.  The first wave will pass through the commonwealth on Wednesday, the second will push through on Thursday then finally the last one will affect the region on Saturday.  The last two events look to be more of a wintry event, the last one still up in air, as the models are not in agreement.

Short-term:  Looking at what the 15z GFS and NAM have to say and comparing it to current radar and metar data, the models are slow by 3 hours.  Therefore we went with scattered showers during the day, as this quick system makes a drive through the region.  Both models show precipitation increasing overnight, as the second wave makes its way up the Ohio River Valley.  The low looks to be traveling south of the state.  While this happens, the "540" line and the 0 degree 850 line will dive through the state.  This will set up the chance of snow for Northern parts of the state.  The SREF starts showing a 30% chance of snow for North Central by 15z, increases to 55% for 18z, and 100% for 21z and 0z.  State College, Northern Susquehanna, and Northeast chances for snow increase by mid afternoon from around 30% to 100% for the evening.  Then looking at snowfall probabilities from the SREF, it shows 100% for 1-4" of North Central for the afternoon and evening time frame, while the other three zones saw between 70 and 100% for the evening.  Went with the following snowfall totals: North Central: up to 4", State College/NSQ/NE: up to 2".

Long-term:  Friday will warm up to the 40's under mostly to partly sunny conditions, as we await the system to the south.  A wave will be rolling through the Lower Mississippi Valley and Southeast, then will turn to the NE, as its shortwave becomes amplified by a trough becoming negative.  This is where the uncertainty becomes very unclear.  The EURO for the past several days, has this shortwave moving up the coast, having cyclogenesis occurring, and a big snowstorm will occur for the Central and Eastern PA.  This solution has shifted a little to the east according to the 0z EURO run.  While the polar opposite is the solution for the GFS.  The GFS has been taking this storm right out to sea from the Southeast. But as of 0z the GFS has made a shift to the west, and now has a similar track (still east of the EURO).  Going with more of a EURO solution as suggested by the HPC Model Diagnostic Discussion (http://www.hpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdhmd).  Due to this, temperatures for Saturday are similar to EURO, still encompassing what the GFS has forecasted.  This situation will likely change over the next several shifts, so this is still leaning on the side of caution that this could be a dud for Saturday.  Sunday we clear out and mostly sunny skies rule the world.

Kept temperatures near previous shift, with the exception to NE and for Saturday.

--
Tyler B. Roys

Vice President of Campus Weather Service

(www.campusweatherservice.com)

The Pennsylvania State University

Meteorology Class of 2012

Tuesday Night Technical Discussion

Week after week it seems that we are looking at the same old, the pleasant weather earlier in the week will soon give away to yet another storm system, or maybe even two more by the end of the weekend. The cold front sitting over the Great Lakes right now will continue to push further south with the shortwave associated with the cold front approaching Pennsylvania by late in the day on Wednesday. This will allow for more warm air advection Wednesday, which will bring 60 degree temperatures to much of the state. The shortwave will also bring a few showers, especially in the northern regions of the state on Wednesday. As we move towards Thursday, the cold front and associated shortwave will arrive in Pennsylvania bringing periods of rain for the majority of the day, as well as cold air advection which will lead to much cooler temperatures as we move later in the day on Thursday. The shortwave will slide out to sea Thursday night, leaving behind much cooler temperatures and uncertainty heading into the weekend. Friday will remain cool and dry, but things get complicated as we move later in the day on Friday. It seems most of the models develop a second storm later this week after the first shortwave leaves. The issue with the models seems to be the timing and location of the storm. The NAM and GFS models wait to develop the storm when it is well out to sea. This scenario would keep the entire east coast dry with well below average temperatures for the weekend. The other side of things is the European model which develops the storm right on the coast and allows for enough tilt in the jet stream that the storm just rides up along the coast. This scenario would lead to a snowstorm for some areas of Pennsylvania depending on how close the storm was to the coast. A storm closer to the coast could bring significant snowfall to western and central Pennsylvania with a large rainstorm in eastern Pennsylvania. If the storm were to be a little further off the coast, the area of snow could shift more towards eastern and central regions of the state. So with much uncertainty in the forecast this weekend, right now all that can be guaranteed is a chilly weekend with the chance for some snow or rain.

Zachary Fasnacht

Tuesday 4:00PM technical discussion

Synopsis

A ridge is currently in place over the mid-Atlantic region of the country. This is providing generally rain free conditions for much of Pennsylvania. Areas up north in the keystone state are experiencing some precipitation and clouds associated with a frontal boundary. This should continue to impact our area into tomorrow. A trough will bring rain followed by snow showers in some places especially to our north Thursday and into Friday.

Short term

This boundary should keep clouds and precipitation around our area and especially in northern sections of the state over the next day or so.  The NAM brings in rain showers across the west early tomorrow and has them lingering across the state as the day continues on. A low pressure system will follow in late Wednesday into Thursday bringing rain to much of our state.

Long term

Unsettled weather will be the story for Thursday. Much of PA will find some rain during the day. Temperatures should remain above freezing throughout much of the time period until late Friday. The SREF has a fairly high chance of snow showers developing late in the north central region once the frigid air builds in with the passing of the front.  It doesn't appear to be anything substantial accumulation wise. All precipitation should exit by Friday morning leaving cold air behind. The 12 km NAM keeps high temperatures across the state in the 30's and 40's over the weekend. The European currently brings in a system which could produce a fair amount of snow on Saturday. There is little consensus pointing to this happening at this point. Time will tell.

-Doc Ray

Synopsis

As the ridge of high pressure moves out a fast moving Alberta clipper will be over the area Monday bring some showers and a possible thunderstorm during the day.  There is a trough brewing towards the middle of the week that may spawn a storm during the week. 

Short term

Currently the low-pressure system stationed over the Great Lakes will push a weak front through the state on Monday.   Around sunrise we will start to see precipitation staying below 1 inch.   By 0Z all areas should be dry.

Long term

A brief period of pleasant weather in store for Monday evening and Tuesday before more moisture associated with a front pushes in Tuesday night,.  More moisture towards the end of the week with colder temperatures also. 

-Tom Lutz

Sunday Afternoon Technical Discussion

Synopsis:

High pressure moves out tonight. A cold front coming in from the western Great Lakes will move through Monday, giving us periods of showers, perhaps a few rumbles of thunder. High pressure slides through on Tuesday and Wednesday before another cold front (currently north of Montana) rolls on through for the end of the work week.

Models used: 9Z-15Z SREF (plumes, PoP, models), 12Z NAM, 12Z ECMWF, & 12Z GFS

Short-term:

The SREF shows only 0.02-0.07" of precip for Monday as the front passes through. Parts of PA may get 0.15". There are a few others that suggest <(1/3)". The SPC Day 2 Convective Outlook suggests thunder possible. Temperatures will be in the upper 50s/ low 60s.

Long-range:

The SREF and GFS confirm rain occurring on Thursday. This could possibly be heavier than what will probably fall on Monday.

-Jaron Breen

Thursday Evening Technical Discussion

Synopsis

As the upper low in Southern Canada continues to move to the north, it will produce widespread clouds and rain showers into Friday. Once the low departs, an area of high pressure will build into the northeast which will promote milder temperatures.  The next system will be a surface low moving southeast into the area with a chance of showers Monday. Another ridge of high pressure will provide better, more fall-like weather for Tuesday. However, a deep trough over the Midwest will help an area of low pressure form and it will eventually move toward the east mid-week.

Short Term

Currently, the low pressure system over the great lakes is weakening and has occluded. Skies conditions will remain cloudy and temperatures will be steady in the low 40's.  There is the possibility for showers over the western locations in Pa and amounts should range from about .1 to .3 inches. There will not be much change on Friday as we still are under mostly cloudy skies due to this 500 mb low. This will cause the diurnal range to be relatively small tomorrow. The 00z NAM and 21z SREF maintain the strong southwesterly winds due to the pressure gradient remaining tight. Saturday will be nicer as the low moves off to the north and skies become partly cloudy. This will allow area to warm up in to upper 50's with lighter winds.

 

Long Term

On Monday, a surface low will create a chance for showers and bring cloudy skies. This will be short-lived as an area of high pressure builds in behind it on Tuesday bringing more pleasant weather. There will be another weather maker as an area of low pressure forms over the upper Great Lakes and begins to move toward the commonwealth.

-Matt Mehallow

Thursday Afternoon Technical Discussion

Synopsis

The same weather pattern that we saw last week has repeated itself this week. An anomalous cutoff upper level low is sitting over the great lakes region bringing much unsettled weather. It will weaken and begin to push north over the next couple of days. A broad area of higher pressures will slowly build in behind it providing calm weather for the weekend. By the middle of next week it appears there will be more troughiness in the eastern half of the country.

Short term

A large cutoff low with accompanying surface low have provided the environment for yet another substantial rain event for the parts of the state. The low has now been well occluded and is pushing into Canada so; as a result, the steady rain has given way to wrap around clouds and drizzle. Slightly more precipitation may in the mountainous regions of western Pa due to orographic enhancement. Clouds will be slow to clear on Friday as anticyclonic flow remains aloft. By Saturday though, the area of high pressure should gain enough influence to clear out the sky. Expect temperatures to remain slightly below normal.

Long term

During the second half of the weekend into the beginning of next week, expect a broad surface high to keep the weather tranquil for the entire state of Pennsylvania. The east remains under a weak trough in the upper levels which will keep temperatures from rebounding too much. Yet another piece of energy comes through the flow towards the middle of next week, which will provide the trigger for the next chance of rain.  

Steven Fuhrman

Wednesday Night Discussion

Synopsis: A larger scale weather system pounding the eastern portion of the country with rain and wind will begin to move out of the picture. Cooler temperatures and breezy conditions can be expected in the wake of the storm. A ridge will build in Saturday, bringing slightly warmer temperatures and dry conditions for the weekend.

 

Short Term: Showers and batches of heavier rain can be expected overnight due to the passing of an occluded front, extending from the strong surface low in the ohio valley out towards the D.C. area. Embedded thunder is not out of the question. As the low begins to weaken and depart on Thursday, cold air advection will bring cooler temperatures. Strato form clouds will envelop the state, with eastern zones seeing frequent showers. Showers may persist into Friday with the possibility of a rain snow mix in the higher elevations of southwest PA.

 

Long Term: High pressure will move in behind the system, bringing dry conditions and a slight moderation in temperatures for the weekend. The Commonwealth will not see perfectly sunny skies, as there will be more of a mix of stratocumulous clouds and sun. Forecast confidence leading into next week is not very high. However, there seems to be a chance of showers with the passage of some energy on Monday.

Technical Discussion Wednesday October 18th, 2011

Synopsis:

A center of low pressure to our west will continue to move northward, bringing with it lots of showers and breezy conditions. It should clear out by Friday, leading up to a sunny and dry weekend.

Short Term:

Showers look to continue into the overnight hours and into Thursday morning in parts of the eastern Commonwealth. Skies will remain mostly cloudy through Thursday until dry air forces the low to dissipate, leaving us with partly sunny skies Friday. We can expect windy conditions as this system continues to move northward Thursday into Friday. As cloud coverage begins to dissipate we can anticipate temperatures dropping into the 30s leading into the weekend.

Long Term:

Partly sunny skies and dry conditions are in store for Saturday. As the upper level trough associated with the low pressure moves its way off to the north, clouds will dissipate leaving us with sunny skies and temperatures in the 50s for Sunday. Overnight temperatures continue to remain in the high 30s. 

Forecaster: Meredith Nichols

Technical Discussion Tuesday 10/18/11

Synopsis...

A very potent center of low pressure will make its way toward the commonwealth Wednesday, bringing lots of rain with it. This low pressure will hand around through early Friday, making way for a great weekend.

Short Term...

Based on current observations and a blend of the GFS/NAM model runs, the remainder of the overnight period and the early part of the day Wednesday looks like it will remain very comfortable with some passing clouds. The first batch of rain should make its way into the southeastern part of the commonwealth by early Wednesday morning, with the rest of the state seeing their first raindrops by 2pm. Most of this rain looks to fall during the day on Wednesday, with some lingering showers lasting through the overnight into Thursday. Beyond the morning hours, Thursday does not look to be a complete washout, with several model runs pointing toward some leftover shower activity confined to the eastern regions of the commonwealth. Regardless, the residing low will keep skies mostly cloudy to cloudy for the day on Thursday. The cloud cover should diminish later in the day Thursday into Friday as dry air "fills" the low pressure, weakening it significantly. Also, the upper-level trough associated with it will move its way off to the north, promoting partly to mostly cloudy skies.

Long Term...

Saturday looks to be a gorgeous day with partly cloudy skies and typical fall-like high temperatures. Both the GFS and ECMWF models show very dry conditions at 700mb with the trough well off to the north, and spotty areas of higher relative humidity. Though conditions will be much drier, a weaker trough will promote surface convergence and likely produce partly to mostly cloudy skies over the commonwealth for the weekend. Our next system, though not very significant, appears to roll in later in the day on Sunday, which will be something the next shift will have to take a good look over.


Andrew Dzambo

We Are... Penn State Meteorology

10-19-2011 Technical Discussion

Technical Discussion

Synopsis:

A large early season storm will affect the region starting Wednesday morning. Expect showers to develop early Wednesday morning and continue throughout the day. The western and extreme eastern part of the state may see some steadier rains. Some isolated showers will linger into Wednesday night and the winds will start to pick up. Thursday looks to be a blustery day with mostly cloudy skies and possible light showers. Things should calm down on Friday as the storm system departs the region.

Short-term (Tuesday night-Wednesday night):

A sharp deep in the jet stream has spun a low pressure over Tennessee Valley tracking northeast toward the Commonwealth. This low is expected to intensify even further as the 500mb trough becomes negatively tilted and cuts-off over Ohio-Tennessee Valley, down to approximately 988mb by late Wednesday night. Meanwhile, a second low pressure will develop off Florida Panhandle Tuesday evening in response to the strong positive vorticity advection brought forth by the deepening trough. The water vapor imagery is already showing a robust system forming at the time of this writing. This second low is expected to track north-north-eastward along the southeast coast Tuesday night and Wednesday morning and tap in tropical moisture from remnants of tropical disturbance 95L. As it does so, parts of the southeastern states will see much needed rain to fall Tuesday night. However, the rain is not expected to reach the northeast later Tuesday night or early Wednesday morning. The commonwealth should see the first drops from this coastal storm to fall sometime early Wednesday morning, especially over the eastern half of the state. However, the aforementioned primary low over the Ohio Valley will also intensify rapidly as the upper-level trough occludes. This storm is expected to bring rain showers to the western parts of the state late Wednesday night. For the central portion of the state there is a concern that a dry slot developing behind the upper-level trough may significantly cut down the precipitation amount on Wednesday. As Wednesday night approaches, most of the rains should have moved out of the region except for the western half of the states as the Ohio low brings more moisture into the region. The winds are also expected to intensify behind the storm system.

Mid-term (Thursday-Friday)

Blustery conditions will linger into Thursday as the winds pick up behind the passage of the storm. Expect mostly cloudy skies with some possible showers on Thursday, especially over the western half of the state on the windward side of the storm, where some orographically lifted precipitations are possible. However, the eastern half of the state should only see isolated showers, otherwise, partly to mostly cloudy skies with windy conditions. The winds should gradually calm down across the state on Friday as the storm weakens over Canada.

Long-term (Saturday)

Despite the 500mb low lingering over the eastern half of the nation, the upper-levels of the atmosphere should start to dry up as the day progresses. Expect partly cloudy skies for most parts of the state. Some counties near the lake may see more clouds and possible light drizzles.

Written-by

David Wang

Afternoon Technical Discussion - 10/17/11

CWS Tech Disco – 10/17/11 Afternoon

Synopsis:

Clear skies will remain overnight and into early Tuesday, with temperatures again remaining mild. A strong area of low pressure will move into the region Wednesday, bringing significant rainfall to the state through the middle part of the week. Temperatures will fall ahead of clearing skies as we move into the next weekend.

Short-Term (Overnight-Tuesday Afternoon):

A weak area of high pressure over the region has provided mostly sunny skies and mild temperatures reaching into the 60s for this afternoon. These mostly clear conditions should continue overnight, with only a few high cirrus clouds to content with. Temperatures will likely fall to near-normal levels, reaching the low 40s in most areas. Finally, winds should continue to die down overnight as the large area of low pressure that gave us strong winds over the weekend continues to move away.

Tuesday will not be a bad day, weather wise, with temperatures reaching back towards the 60 degree mark again. Clouds will thicken during the course of the day, however, with skies mostly cloudy in many regions by nightfall. Tuesday should be dry, in accordance with American operational and ensemble models. The 12z ECMWF has a small chance for precip banding across the state, but we feel this chance will be minimized.

Long Term (Tuesday Evening – beyond):                      

The whole story changes by Wednesday morning, however, as a powerful synoptic storm sets up shop across the area. This system will strengthen as it is drawn up the coast, pushed by a strong upper-level trough. All regions of Pennsylvania will see rain on Wednesday, with the east and west edges of the state likely to pick up the greatest amounts over the course of this storm. Models largely agree with rainfall entering the state very early Wednesday morning. While the exact strength and track of the storm's center are not certain yet, its size will mean that will likely not matter. Rainfall amount forecasts are still rather variable, but according to SREF plumes, expect near an inch of rain in the W and NW regions and near 1.5" in Philadelphia.

Meanwhile, SREF plumes forecast accumulated rain of near three-quarters of an inch in State College.

The bulk of the rain should clear the state throughout Thursday, especially Thursday morning. There will likely be a few remaining lake effect rain showers in the NW lasting into early Friday, but these should be nothing more than a nuisance shower. Expect skies to clear dramatically behind the system as another area of high pressure builds for the weekend, albeit bringing with it colder temperatures.

Synopsis: A ridge of high pressure will move over the state on Monday and bring fair and dry weather to the areas. A weak warm front could bring light showers to some areas on Tuesday. A significant low-pressure system will ride up the coast and impact the state from Wednesday through Friday and bring significant rainfall for those three days. Strong Northwest winds will keep temperatures below normal for Thursday and Friday behind the system.

The ridge of high pressure moving into the area on monday will bring dry area to the mid and upper levels of the atmosphere and keep the atmosphere relatively dry, causing plenty of sunshine for Monday. The models are in agreement about the timing of the low-pressure system that moves in on Wednesday. 

Sunday Afternoon Technical Discussion

Synopsis:

A weak cold front will move through overnight, producing showers. Behind it, an area of high pressure will build in early Monday but pull out on Tuesday. Meanwhile, a developing tropical system currently located near the southern Yucatan peninsula will move up the East coast during the early part of the week. Its moisture is anticipated to arrive in PA around midnight Tuesday (0400Z Wed. 19 Oct. 2011) and pull out of PA sometime on Thursday. High pressure will build in behind the system on Friday.

 

Cold front moving through the northeast today:

The 09Z SREF members and 12Z GFS are in agreement with timing. Expect isolated showers with total amounts no greater than a quarter of an inch.

 

High pressure for Monday PM through Tuesday:

The 09Z SREF members and 12Z GFS are in agreement with timing. Expect partly cloudy skies and comfortable temperatures.

 

Tropical system heading up the coast:

At the suggestion of the HPC, we used the 12Z ECMWF. Other models are not handling this well, but they will get better with this as the system gets closer. The NHC is monitoring this system. Regardless of whatever time it arrives, expect 1.5" of rain and a few isolated thunderstorms east of US-220 and about half as much rain west of the highway. This will change with the projected path. The SPC (see Day 4-8 Outlook) is also monitoring this system. Remember: "the trend is your friend."

 

High pressure building in behind the system:

I used the GFS to see what will build in behind it. When it builds in will depend on when the tropical system exits.

 

-Jaron Breen

Thursday Evening Technical Discussion

Synopsis

The upper level trough currently over the eastern United States will begin to slowly lift to the north over the next couple of days. As a result, this will decrease the shower activity and bring more seasonable and brisk conditions. Early next week, another trough will develop over the eastern United States bring more unseasonably cool weather and a chance for a storm later in the week.

 

Short Term

 

 Currently, there are bands of showers that will continue to move to the north across Pennsylvania overnight. As we approach the morning hours on Friday, there is the chance of fog developing as there is lots of moisture in the air just above the ground. The main weather maker on Friday is the cold frontal passage that is progged to pass through the PA between about 10 am and 3pm. Behind this front, temperatures begin to fall as there is strong cold air advection from the west as well as gusty winds. Temperatures will fall to mid-40'a over most of commonwealth Friday night as the northwesterly flow continues.

 Mid Term

 On Saturday, the closed low over the great lakes will move into Canada. Both the 21z SREF and 00z NAM indicate the possibility of winds of 20-25 knots with gusts approaching 30 knots on Saturday. Drier air will also work into the area due to the strong northwesterly flow and substantially decrease the chances of showers over the commonwealth. This strong low will create quite a pressure gradient which will result in strong westerly winds again during the day on Saturday. Temperatures will rebound to near normal on Sunday. However, the winds will remain through Sunday and make it feel much colder.

 Long Term

 Winds will gradually slacken on Monday as the pressure gradient relaxes and allows temperatures to moderate. However, the trough over the southeast Canada will remain entrenched and gradually move back south into the central United States. This will keep us in a pattern with temperatures near average to just below. Mid-next week there is a chance that a low pressure system could form in the Ohio River Valley and track up across the forecast area Tuesday into Wednesday bringing a chance for precipitation.

-Matt Mehallow