Technical Discussion

Synopsis...

Low pressure over Lake Superior will be the cause of unsettled weather over the region today and tomorrow.  Heavy rain expected tonight with snow showers behind the system tomorrow.  Some minor accumulations are possible.  Typical westerly/northwesterly flow lake effect regime will set-up Thurs-Fri.  Slightly better day possible on Saturday before pattern becomes active again next week.  Temperatures will remain below average throughout the period.

Short Term (Tue-Wed)...

Temperatures in 40s and 50s across the state this morning with rain in most places.  Winds becoming gusty (35kts in ERI) across the Commonwealth and will continue to do so throughout the day.  Deep trough at 500mb promoting PVA ahead of it will help enhance precipitation across the Commonwealth today.  One slug of precip currently making its way northeastward.  Slight dry slot behind it in eastern Ohio should allow a break in the rain later this afternoon.  This will not last long though as secondary low pressure forms off the eastern seaboard allowing, enhancing precip tonight across the state.  Narrow cold frontal rain band tomorrow morning could bring a rumble of thunder and gusty winds (40-60mph) mainly in eastern half of state as front pushes eastward.  Nonetheless, very heavy rain 1-2"+ expected by the time the storm moves out tomorrow.  Cold air will immediately rush in behind the system. High temperatures will occur near daybreak in western zones on Wed and no later than noon across the east.  Winds stay gusty behind the front and shift to the west with temperatures falling to freezing by evening.

Long Term (Wed Night-Sat)...

Typical northwest flow regime sets up for Thurs-Fri with better chance of lake effect of snow on Friday as winds go more northwesterly rather than WSW.  Temperatures in the 30s which will be well below average.  Less chance of snow for Saturday but the next shortwave is not far away and could bring a swath of light snow for Sunday night.  Next week promises to be active with the possibility of the first major storm of the season.

-ddpdtdt

Forecast Discussion

Synopsis...

Rainy day in store for Tuesday and the first half of Wednesday. temperatures will cool down significantly behind the occluding front associated with this rain. Cold and cloudy conditions will persist behind this front, and will make the forecast period beyond Wednesday a rather boring one...

Short Term...

A fast moving and strengthening frontal system will bring moderately heavy rain to the commonwealth for Tuesday. Based on the recent RADAR, the WRF and HRRR models are too slow with this system as the outer edge of the warm front associated with this system has already made it to the extreme southwest tip of the state. This isn't the strongest rain associated with this system, but most areas in the west and central parts will see at least a light rain through sunrise. The WRF shows the warm front slowing down, and given that this system is still funneling a large amount of moisture from the Gulf of Mexico, a steady rain will persist through Tuesday especially the west and central regions. At some point late Tuesday night, the cold and warm fronts will occlude. The heaviest rains will come at this time, and the eastern regions of the state will see the heaviest rains. Most of the commonwealth will experience heavy rain Tuesday night through Wednesday morning, but starting Wednesday morning, the occluded front will begin to exit and the commonwealth will be clear of rain by the early evening.

Long Term...

Once the occluded front passes, MOS shows temperatures drops as much as 15-20 degrees compared to what they will be on Tuesday. This cold trend will continue through the weekend as a steady westerly flow builds in. The WRF shows nothing beyond Wednesday in terms of another possible weather maker, but high humidity at 700mb and 850mb through the end of the week should allow for cloudy skies to remain through then. Given this trend, most areas will not reach the 40s for their highs.


Andrew Dzambo


We Are... Penn State Meteorology

Technical Discussion (Monday Afternoon Shift)

Synopsis:

 

The high pressure system that has controlled the region over the past few days is going to get the crap kicked out of it by a huge low pressure system gaining strength over the central plains. The combination of PVA, being on the eastern side of a large 500mb trough, and being the left exit region of a Jet Streak will strengthen this storm system that after tapping into the Gulf of Mexico's moisture will have enough energy to cause widespread flooding across the Allegheny Plateau. Behind this system it gets really dry and the coldest air of the season will move in for the weekend.

 

Short Term: Tonight

 

Increasing cloudiness from west to east as this storm approaches. Winds will also begin to pick up. Also I expect rain to begin falling in the westernmost portions of the state by daybreak.

 

Mid Term: Tuesday and Wednesday

 

This storm will track along the Allegheny Mountains causing the heaviest of rain to fall the central mountains of Pennsylvania. The rain will come in two waves; the first, which is associated with the warm front, will move through the state Tuesday morning and bring scattered showers to the western half of the state. The HRRR doesn't appear to have too much energy associated with this front so the rain will probably be quite scattered tomorrow morning. However, in the afternoon the second wave that is associated with the cold front will begin to move through the state. The cold front will also cause very gusty winds with some areas seeing gusts over 40 mph. Behind the cold front, the rain will end and move out of the region. I expect most of the heavy rain to be over by Thursday morning however, the damage will have been done with most of the state seeing anywhere between 2 and 3 inches of rain with locally heavier amounts possible.

 

Long Term: End of week

 

Behind this system, a northwestern flow will cause lake effect snow showers, predominantly on Thursday. Accumulations are expected to be minimal however; the extreme Northwestern part of the state could pick up a few inches. The lake effect will diminish on Friday as this storm system slides off to sea. A polar high pressure system will develop behind this storm causing the coldest weather yet this fall with some portions of the states reaching into the upper teens Friday or Saturday night.

RJ Patrizio

11-29-2010 Technical Forecast Discussion

Technical Discussion

Synopsis:

A ridge of high pressure will remain above eastern 1/3 of the United States on Monday, keeping the weather calm for the majority of the Northeast. Some clouds will move into the region Monday night as a strong mid-latitude disturbance rolls across the Midwest. Some scattered showers will ensue Tuesday morning as the storm system approaches. The rain will become steady towards Tuesday evening as storm's cold front draws in a lot of moisture from the Gulf of Mexico. The rain will continue on Wednesday but gradually tapering off from east to west in the afternoon. Some lingering showers and snow showers are also possible in northwestern part of the state Wednesday night. Clouds should start to break up and give way to a fairly nice end to the week with cooler temperatures.

Short-term (Monday – Monday night)

A ridge of high pressure will continue to dominate the region, providing us minimal rising motion, and thus not very supportive of cloud developments. The skies should remain mostly sunny throughout the day on Monday. However as we progress into the evening hours, some high clouds associated with a Midwest cyclone will begin to move into the region. The clouds will gradually thicken as the night grows and expect mostly cloudy skies by Tuesday morning.

Mid-term (Tuesday – Wednesday night)

Most of the models have reached a consensus that some rain showers will develop across the Commonwealth as early as Tuesday morning. There could be a brief period of light rain and drizzle Tuesday morning as the warm air coming from the south overruns the cold air sitting over our region. However, the main bulk of the precipitation will arrive late Tuesday afternoon ahead of the approaching cold front.  For western half of Pennsylvania, the rain will become heavy at times Tuesday night as the strong cold front will generate a line of heavy showers. The predicted CAPE value doesn't look too good for thunderstorm development once again this time. However with strong upper-level winds, the conditions may just be favorable enough for a  chance of thunderstorms in western Pennsylvania. The chance of thunderstorms increases toward the eastern half of the state as warm air advection ahead of the cold front will also support convective showers.  Most of the state will see a brief period of heavy rain as the line of showers and thunderstorms pass through the region, though still cannot rule out the probability for some isolated cells to reach the severe limit as they will likely be accompanied with localized downdrafts. Rain will continue on Wednesday, but gradually tapering off from east to west in the afternoon as the cold front sweeps through Pennsylvania. Some backend snow showers will also be possible for western half of the state as the temperatures drop quickly behind the cold front.

Long-term (Thursday – Friday)

Yeah, I know this technical discussion is pretty long already, but the week just doesn't end Wednesday night. Clouds will break up late Wednesday night and sunshine will prevail on Thursday. The temperatures will be much cooler comparing to what we will see on Tuesday ahead of the cold front. The weather conditions will remain calm for the rest of the week as another high pressure system builds back in from our west.

David Wang

Technical Discussion

Synopsis:

A significant system will bring heavy rain to much if not all of Pennsylvania.  A semi-stationary cold front will act as the track for a second wave of energy and moisture from the Gulf of Mexico, making this a multi-day event. 

Short-term:

High clouds will build across the state today, and in some parts in the west, will almost completely diffuse the sunshine.  Temperatures will be warmer today than previous days due to sunshine and southerly flow ahead of the front.

Medium-term:

The attempt at consistency between forecast zones was to put in place these guidelines: looking at the 12-hour SREF probability of .5 inches or greater of precip – if it was yellow or greater, forecast for "heavy rain" – if it was between blue and yellow, forecast for "rain, heavy at times."  Rainfall amounts were determined with SREF plumes.

There appears to be some effect by Lake Erie on rainfall amounts as seen especially in SREF probability maps, which reduces rainfall amounts over and just south of the lake.  While no one could explain why this could be, the striking and apparent anomaly was respected in the forecast for Erie.

There are some regions where wind could be significant, even for just a 6 hour period.

Temperatures fall during the day on Wednesday in many locations, especially in western and central PA.  This is important to point out in the remarks, especially as there could be a transition to snow in the precip.

Long-term:

Snow showers develop behind this system.  I believe I was appropriately liberal with extending snow showers or flurries across much of western PA, as well as indications of accumulations where appropriate.  If anything, State College is not snowy enough.

Technical Discussion

Synopsis…

Lingering high pressure over the region will allow for lots of sunshine on Monday.  An approaching disturbance and associated cold front will move through the state Tuesday into Wednesday, bringing with it scattered showers, possibly moderate to heavy at times.  Colder air will build into the state after the passage of the front for the remainder of the week.

Short-Term….

The models all agree that lingering high pressure over the state from the system that will be progressing towards the New England region will keep conditions dry and relatively cloud-free on Monday.

Long-Term….

Some slight uncertainties begin to arise with the timing and extent of precipitation in association with the low pressure system currently developing over the Rocky Mountains region.  A well-defined frontal system is projected to form as this low tracks across the US in a northeasterly fashion. The center of the low pressure system itself will pass well to our north north-east later in the week, but the cold front will pass through the state as Wednesday progresses.  The 1200 UTC runs of both the WRF and GFS models show the swath of precipitation associated with the cold front entering western regions of Pennsylvania by Tuesday morning.  The 900 UTC SREF precipitation ensemble mean shows the main swath of lighter precipitation encroaching upon western Pennsylvania zones by Tuesday morning as well, but has some smaller, spottier bands of showers actually affecting central Pennsylvania hours earlier.  We forecasted accordingly.  The WRF and the GFS both show more significant bands of precipitation affecting the state beginning Tuesday night, with the heaviest bands passing throughout the day on Wednesday, with the eastern regions experiencing this more towards Wednesday night.   The SREF precipitation ensemble mean shows a slightly more organized band of heavier showers charging through the state as Wednesday progresses.  We were not afraid to use phrases such as 'rain, heavy at times' for our forecasts, especially on Wednesday.  One additional uncertainty was the potential for spotty snow showers mixing in, especially in the more northern or higher elevation regions Tuesday night into Wednesday.  This is highly dependent upon how much cold air builds in behind the frontal passage, so we were quite conservative in this respect.

Sunday Discussion

Synopsis:   Cold front moves through the state late Saturday night, making sunny but below normal Sunday.  Clouds will move on in as a warm front from storm #1 pushes northeast.  Warm front moves in on Monday, while the cold front pushes through on Tuesday.  Wednesday is best out of the forecast, as partly cloudy skies will dominate.  Storm #2 comes in from the Northern Plains for Thanksgiving, in the terms of scattered showers.  The center will relocate on the Atlantic Ocean at the New Jersey coast; wintry mix might appear for western half.

Short term:  Going off of previous trends, the NAM is the outlier here, relying on the GFS and EURO.  The NAM seems to be playing catch up to the GFS/Euro, while the GFS is playing the same game with the EURO.  GFS shows the clouds move in associated with a warm front from a low pressure system that is riding a trough that is over the Mid-west, moving in late Sunday.  These clouds will remain for all day on Monday with showers entering the region by dawn on Tuesday.

Long-term:  Showers associated with the cold front from the storm mentioned in the short-term forecast will slowly move across the state on Tuesday.  Immediately after the showers pass through the GFS signals clearing for Tuesday night, this sets up for the partly cloudy skies for Wednesday.  Storm number 2 will streak across the Northern Plains before trying to relocate off the coast of New Jersey. This will give the Commonwealth showers for Thanksgiving Day.  This seems to be not a fast mover, as fresh Canadian cold air is following it, and this will last majority of Thanksgiving Day and into Black Friday.  When the low relocates to the shore of New Jersey, cold air will enter the western half of the Commonwealth, this might set up for wintry mix in the hills.

Technical Discussion

Short Term/Long Term...

Patchy clouds across state as weak back door cold front drifts eastward.  This will allow places in the east to be cooler tomorrow while an approaching warm front and accompanied southerly flow will make tomorrow warmer across western zones.  Sensible weather will be in the form of partly cloudy skies today and increasing clouds through Monday as the warm front lifts northward head of approaching disturbance.  Models in fairly good agreement with timing of CFROPA on Tuesday morning/midday.  Mentioned cooling at night on Tuesday and cooler on Wed behind initial front passage.  Weather really gets interesting on Thurs-Sat as another shortwave ejects from the trough diving into the SW.  Depending on how much cold air drifts in Wed behind front, and track of system on Thurs/Fri, we could be dealing with some wintry precip for portions of Thanksgiving.  Nonetheless, it looks colder after Thanksgiving as heights fall to near 510 dm.  

ddpdtdt

11/19 Technical Discussion

Synopsis:

A ridge of high pressure settled over Pennsylvania brings fairly boring weather conditions for the weekend into early next week. We expect mostly sunny conditions across the Commonwealth, with a few passing clouds here and there, especially today. A warm-up is predicted for Monday and Tuesday, and our first chance of precip comes at the end of the forecast period as a very slight chance of showers.

Short-term:

Beautiful fall weather is expected, as the ridge of high pressure establishes itself to our South. Any lingering showers have just ended across Pennsylvania and sunny skies are in store for the remainder of the weekend. Temperatures look to be seasonable, although we found the WRF to be a bit extreme for its temperature predictions on both the highs and the lows, so we forecasted more conservatively. Overall the weather is fairly consistent through the short-term.

Long-term:

After a relatively quiet weekend, clouds and the chance of precipitation will work its way back into the forecast according to the WRF and NAM models starting Monday night.  A low pressure off to the northwest will enhance these clouds.  Also associated with this pressure system are gusty winds especially in the western portions of the state.  A warm air mass will encompass the state during this time, which will push temperatures well above average for Monday and Tuesday. The next major storm system to affect us looks to bring us interesting weather, although the timing and even the type of precipitation are at the moment questionable. Current model runs show arrival around Wednesday night, and affecting us through the Thanksgiving holiday. The only certainty with this next system is that it will bring an end to our above-average temperatures.

Burkely Twiest and Patrick Ritsko

22z Technical Discussion - 11/18/10

Synopsis…

Another shortwave will continue to pass through the area this evening, bringing with it a few scattered showers. Areas closer to the lakes will likely see the most precip due to lake enhancement through Friday morning, and some of the coldest locations may experience a little frozen precip mixed in. Following this round of dreary weather, the pattern will become more tranquil, with dry weather expected through the weekend, before the first in a series of potent storms advances from the west.

 

Near/Short Term…

Spotty showers continue across much of the state. With very cold air aloft, the typically cooler spots have already reported snowflakes, especially across the N-Central Zone. As the showers continue in these areas, we kept flakes in the forecast through tonight. Trough appears to have just enough oomph to keep squeezing out showers as it crosses PA, so we left in the chance of showers, even across SE PA to play it safe. By Friday morning, precip should only be bugging the Big Apple as PA enjoys clearing skies and moderating temps under a decent-sized ridge.

 

Long Term…

Ridge will dominate the pattern over PA through the WKND with SCT/BKN clouds being most common. Temps should remain seasonable, but winds will pick up as dry shortwave passes thru and be gusty for the college games on Saturday. Models agree on a general warming trend into the beginning of next week ahead of a developing storm system. Went conservative with high on Monday; with stronger thermal advection, could see even higher temps. We kept MON night dry as most models keep the leading edge of the precip out until Tues, but following shifts will have to watch the timing. Probably no dust storms. Jamba

 

Forecaster: Matt Mahalik

Technical Discussion

Synopsis..

A shortwave moving into the state from the Great Lakes region will bring a chance of showers for this evening across the entire commonwealth, although southeast regions may dodge most of the shower activity.  Snow will mix in after sunset across the northern portions of the state and across the Laurel Highlands.  Some lake effect activity may stir up at times over the weekend over far northwestern sections of the state (Erie/Meadville areas).  Beyond the northwest region, most of the rest of the state will see mostly clear skies and fairly seasonable temperatures for the weekend.  A cold front approaches toward the beginning of next week bringing a chance of showers back into the forecast for Monday.

Short Term...

As stated in the synopsis, a 500mb shortwave is approaching the region from the Great Lakes and brings a threat of showers across most of the state as indicated by the GFS and NAM.  Southeast sections of the state will be in the "iffy" zone for any sort of precipitation.  Decreasing 1000-500mb thicknesses throughout the day indicate that northern/higher elevation regions could see some snow mixing in at times with the rain showers.  After the short wave moves away later this evening and tomorrow, a slight chance of some lake effect may bring some rain/snow showers to Erie and Crawford counties early on in the weekend.

Long Term..

The weekend looks mostly clear for the rest of the state, with seasonable temps as a ridge of high pressure builds in to our south.  However, an approaching cold front will bring a chance of showers to the region sometime Monday or early Tuesday.  Details on timing will have to be determined by later shifts.  Have a good Thanksgiving break all!

Forecaster: Kyle Imhoff

Forecast Discussion

Synopsis...

Cloudy skies in store for Thursday, with a chance of an isolated shower later in the day for regions in the N-NE. Once Friday breaks, expect clearing conditions and abundant sunshine through the end of the weekend. Temperatures will trend cooler through this forecasting period, with some warming expected on Monday.

Short Term...

A weak upper-level shortwave indicated by the WRF model will bring generally cloudy skies into the commonwealth for tomorrow, along with a slight chance of showers to the north and northeast in the evening. Once this disturbance passes, skies will clear out by Friday morning and should give way to abundant sunshine for the rest of this forecast period. MOS has temperatures through Monday trending cooler, with most regions maxing out in the upper 40s.

Long Term...

The next system to watch may come on Monday, as the WRF develops a fairly healthy cold front. Temperatures will warm up Monday and beyond ahead of this front. Initially, this system appears to prolong somewhat through the beginning of the week next week. Thanksgiving, at this point, looks to be at least cloudy if there isn't any rain. Regardless, the forecasting period through Sunday night lacks excitement but should leave students optimistic as they head home for break.


Andrew Dzambo


We Are... Penn State Meteorology

                                                                                                         Technical Discussion

Synopsis:

A low pressure will move out of the region and take the windy conditions with it. A trough will dig into the region keeping the state cloudy for Thursday, but a high pressure system will move in for Friday and the weekend bringing sunshine and helping temperatures get back into the 50s.

Short-term(Thurs-Fri)

A weak trough will move into the state for the day on Thursday. This will keep the clouds around and keep around the possibility for isolated showers. There is a slight chance for lake-effect snow or rain showers as the GFS and the NAM are showing. A high pressure system will move in for the day on Friday and should bring drier air which should bring sunshine as the 750mb heights show drier air.

Long-term (Sat-Sun)

The high pressure system will stick around the area and warm temperatures up to the 50 degree mark. Saturday night could be the coldest night and I went a little lower for the overnight than the MOS.