Thursday Afternoon Technical Discussion

Synopsis:  As we wind down from another beautiful day, expect some increasing clouds overnight with a chance for showers. Tomorrow will be beautiful yet again with mostly sunny skies, but high temperatures will remain well below normal. As we head into the weekend, a gradual warming will occur bringing temperatures back to normal, if not slightly above. For next week, temperatures will continue to hover around normal with some potential for cloudy and rainy conditions, especially in western Pennsylvania.

Short Term:  As the low pressure system swings north into Canada and its associated cold front moves off the coast, a strong area of high pressure will build over the mid-Atlantic.  This high will sit on top of PA bringing gorgeous weather to the area with high temperatures soaring into the 60's.

Long Term:  As next week begins, the high will move out of the area on Sunday night as a weak, slow-moving low pushes through the area.  This disturbance will induce building clouds and some scattered showers throughout Monday and Tuesday.

Michael DiDomizio

Thursday Morning Forecast

Synopsis:  We are starting off today with bright sun, clear skies, and cool temperatures. We can expect tomorrow to be similar today with temperatures starting to moderate a bit. As we head into next week it looks like the current pattern in going to hold steady. Skies should generally remain clear and temperatures will rise a few degrees each day as we head into next week. There are also no real storm threats over the next week, so just expect sun, dry weather, and comfortable temperatures as we head into finals week!

Short Term:  As the low pressure system swings north into Canada and its associated cold front moves off the coast, a strong area of high pressure will build over the mid-Atlantic.  This high will move in from the southwest and induce a southwesterly isallobaric wind, which will keep temperatures from dropping too much in the wake of the cold front.  The high will park itself right over PA for most of the weekend, keeping temps seasonal and skies partly clear.

Long Term:  The high will move out of the area on Sunday night as a weak, slow-moving low pushes through the area.  This disturbance will induce building clouds and some scattered showers throughout Monday and Tuesday.

Monday Night Technical Discussion

Synopsis

 

High pressure will continue to build over the state leading to a stronger southerly flow and warmer temperatures across the state. A low pressure system will pass north of PA on Wednesday and it's associated cold front will cross the state Wednesday afternoon bringing scattered rain showers and potential for storms across the region. High pressure will begin to build over the state behind the cold front for the end of the week resulting in clear skies for much of the state. As the high pressure begins to move off shore Saturday and Sunday a slight chance for scattered rain showers statewide will be present for the weekend.

 

Short Term (Monday night thru Wednesday Night)

 

A mean easterly flow off the Atlantic will provide a chance for increasing clouds overnight for the southern half of the state, thus keeping low temperatures near the mid 30's. Skies should remain clear for the northern counties allowing temperatures to drop into the upper 20's overnight. Clouds will stick around for the eastern and central portions of the state for the beginning of the day keeping temperatures in the mid to upper 50's but high temperatures could reach the upper 60's in western PA. Clouds will once again increase overnight keeping low temperatures in the 40's across the state. The 18Z GFS is a little quicker than the 18Z NAM, as the GFS has the precipitation reaching northwestern PA by 12Z, while the NAM has the bulk of the precipitation reaching the state by 15Z. This leads to a large difference in the high temperature as the GFS keeps most areas in the 60's, while the NAM gets central and eastern PA into the 70's. Given ensemble guidance, am currently favoring a mean of the solutions at the moment with some areas possibly reaching 70 on Wednesday. A chance for thunderstorm development looks unlikely, especially for western and central PA due to the clouds ahead of the precipitation cutting off the potential for convection and minimal CAPE. Low temperatures in the lower 30's will follow the passing of the cold front Wednesday night.

 

Long Term (Thursday into the weekend)

 

High pressure will begin to build over the state Thursday morning and continue to do so through Friday allowing temperatures to approach near normal values. There will be a chance for a scattered rain shower across northern portions of the state Thursday night due to a westerly flow off the lakes. As the high pressure begins to move east of the region Saturday afternoon and Sunday, the 18Z GFS has scattered rain showers across the state Saturday afternoon through Sunday, but confidence remains low. Otherwise, conditions look dry for the weekend. 

~Aaron Herbert

Monday Disco Pm 4-22-2013- Cool with a Climax

Synopsis

Cold air damming has served as the main coolant across the Northeast and Mid-Atlantic states, keeping most areas at least 10 degrees below normal.  Damming will stick around until Tuesday prior to a cold frontal passage Wednesday, followed by a return to normal as the weekend approaches. The Wednesday cold front is the hot button here, for it could bring severe storms into Happy Valley.

Short Term (Now until Wednesday night)

A high off the coast of Maine has created a rige that has been sitting along the eastern U.S. border throughout today. This has remained stagnant due to a block setup via negative NAO. This block will keep the high in place, prolonging CAD until Tuesday night when a 500mb trough will create a dent in the block. Of course, with CAD, temperatures will remain below average throughout the period, even later this week (indirectly dammed). Besides this, the next big thing will be the cold front set to strike Wednesday. Here, there is a discrepancy in which the 12z NAM and GFS  time the front differently, with the NAM at 18z and the GFS at 15z(supported by 12z EURO). The GFS also implies the front falling apart  over central PA, whereas the NAM intensifies a squall line overtop central PA. the 15z SREFs dance around those times, with the mean aligned with the GFS solution, yet the intensity falls near the NAM solution. The Nam though, after reviewing soundings, implies a 40ish knot 0-6km shear with minimal CAPE, showing little convective potential yet a possibly potent storm, but nothing like a tornado watch like last week as of now.

Long Term (Thursday and Friday)

Little to discuss here, after the front passes, the state will return to the below average conditions like today, only a receding 540 line will imply warming to normal conditions Thursday and Friday, yet Thursday will yield a well below average high due to the front, but a high will be moving in from the west, adding a solar component to weekend warming,  the GFS and Nam are showing a weak clipper passing to our north, which could spell light showers along the northern counties. The NAM soundings imply dry conditions during the time in which showers pass, so this seems iffy, yet the 540 line being south of the precip implies a shot for mixed precip, yet the sounding's busting it. Besides this, the weekend looks dry.

Sun. Eve: Warmer, then Cooler with Mid-Week Storms

Synopsis

High pressure just north of the US-Canadian Border and an upper-level trough have helped usher in some cooler air to start the work week. Pretty soon the high pressure will head eastward and set-up a southerly flow which will allow warmer air to move in on Tuesday and Wednesday. A cold front over the northern Mississippi & Lower Missouri River Valleys will slide on through Wednesday, which will touch off showers and thunderstorms throughout the day. The front is offshore by Thursday morning, so clearing and cooler conditions will return to the state. A weak upper-level disturbance could touch off a rain or snow shower overnight while high pressure passes to our south. Then, another system from the Southern Plains heads in for the weekend.

Models Used: 00z NAM & Hi-Res NAM, 18z GFS, 12z ECMWF; glanced at 12z UKMET & CMC and 18z NAMs for Wednesday

Short-Term – Monday and Tuesday

The high pressure system is actually allowing cold-air damming to take place, albeit with temperatures well above freezing. This will help keep temperatures in the 50s for Monday across the northern highlands. The high pressure system will exit eastward and the southerly flow will be able to overcome the cold-air damming that set up over the weekend. Temperatures on Tuesday will be near 70 in parts of the State – possibly near Philadelphia and Pittsburgh with 60s for almost ALL of PA.

Be aware that MOS will have trouble with the temperatures once the southerly flow starts-up. Use the 850-mb/ mixing method plus de-bias the cooler MOS temperatures.

Medium-Range – Wednesday

This was the toughest part of the forecast because while most of the guidance put the would-be squall-line in Ohio on Wednesday AM, the 00z Hi-Res NAM had it in while the European & Canadian model had it in western/ northwestern Ohio around the same time. We put it in West-Central Ohio at 12z Wednesday… pretty similar to the WPC discussion. The set-up and timeline of the front will be almost identical to Friday, with possibly less cloud-cover during the day. There's still uncertainty with 60 hours to go, so we stayed with the possibility of a strong storm. The SPC's Day 3 Outlook should be consulted before proceeding with the forecast for strong storms.

Longer Range – Thursday through early Saturday

The upper-level trough will be slower, which actually could hamper severe weather on Wednesday (less shear than on the 19^th). The 850-mb temps will decrease dramatically, so cooler air at the surface on Thursday is very likely. The upper-level trough will move through overnight which could touch off a rain or graupel shower. Friday will be sunny as high pressure passes to our south. A cut-off low will approach on Friday night, which could touch off a shower in Pittsburgh as the sun rises on Saturday.

-Jaron Breen

Thursday Afternoon Discussion

Thursday Afternoon Discussion

Synopsis: An approaching warm disturbance will trek to our north and bring a cold front through the area on Friday.  As the disturbance departs, cooler air will usher in from the north.  The weekend is looking dry and sunny as high pressure takes control through Monday.  Another disturbance will begin to develop across the central U.S. early next week bringing warmer temperatures back into the region.

Short Term: A marine layer has stuck around all day across the central and eastern portion of the state. This has created low cloud decks and has moderated temperatures.  Locations in the western portion of the state however have had plenty of sun throughout the day and a passing warm front has allowed temperatures to soar into the 80s.  As the warm front approaches the rest of the state, the marine layer will likely deteriorate.  A cold front will move through tomorrow bringing a line of showers and even some thunder and lightning.  This will clear out as Saturday approaches.

Long Term: The weekend and into early next week is looking cool but pleasant.  A northerly flow will develop Saturday bringing in cooler air from the north. High pressure will keep things dry for the weekend. Another disturbance develops in the central plains early in the week and will usher in warmer air.

Thursday Morning Discussion

Thursday Morning Discussion

Synopsis: For the next couple days we will be experiencing mild, muggy conditions as a cold front approaches from the west.  Temperatures will be around 70 with dewpoints around 60 and overnight lows around 60.  We should expect the showers and thunderstorms associated with the cold front to move in around dinner time tomorrow and continue late into the very early morning hours of Saturday.  After the passage of the frontal boundary we should expect cool, clear conditions persisting until the middle of next week.

Short Term: This morning we are experiencing relatively mild, muggy conditions and cloudy skies.  There shouldn't be much precipitation today, but we can't rule out a little drizzle or a light shower.  Tomorrow will start out mild and then turn wet and storming in the evening as the cold front enters our region.  The NAM has us receiving about 0.5 if an inch of rain, so it could rain hard at time tomorrow evening.

Long Term: The passage of the cold front will usher in cool, dry conditions as we head into Saturday.  These cool dry conditions will continue until the middle of the week.  The EURO has the next storm system approaching the region around Wednesday next week.  At this time, it appears that this storm system will just bring a brief period of rain with it.  

Monday Night Technical Discussion

Synopsis

 

A cold front will move southeasterly across the state tomorrow afternoon with scattered showers and thunderstorms ahead of the front. The front will move back to the north Wednesday night and a southerly flow will return and warm temperatures back up Thursday. A cold front will move east across the state Friday evening along with scattered showers and storms bringing cooler temperatures for the weekend.

 

Short Term (Monday night thru Wednesday)

 

A few light showers are possible overnight tonight and tomorrow due to the upslope component of the southerly flow. The southerly flow we currently have will help temperatures warm tonight and Tuesday before a cold front moves across the state from the northwest Tuesday afternoon. Ahead of the cold front will be scattered showers and storms that will linger into Tuesday morning. The 0-6 km wind shear is significant and the convergence of winds near the surface along the front could lead to strong storms. Both the 12Z GFS and NAM agree with precipitation ahead of the cold front moving in to the northwestern counties by 15Z Tuesday and lingering until about 06Z Wednesday. As the front sits to our south Wednesday temperatures will cool, especially for the northern counties with high temperatures in the 50's.  

 

Long Term (Wednesday night into the weekend)

 

The cold front to our south will move back north across the state and a southerly flow will return late Wednesday night and provide warmer temperatures for Thursday with high temperatures near 80 for extreme southwestern PA. As a trough of low pressure approaches the region Friday afternoon, a cold front will move east across the state with scattered storms and showers ahead of the front. We will need to keep an eye on the passage of this front, as the wind fields are strong and upsloping will be present. Showers will linger into Saturday morning and temperatures will be cooler for the weekend.  

~AJ Herbert

Monday PM Disco 4-15-2013 - Blue and White Washout!?

Synopsis

Instead of being "stuck in a rut", we'll be "stuck in a trough" for the next few days. The tail end of a cold front will sweep across the stte tomorrow afternoon, yet its home trough will oscillate through the midweek before converting into a warm front later on. Expect dramatic warmups prior to the cold fronts in question, for a strong stream of warm advection will preced the cold fronts for Tuesday afternoon and Friday night, we definitely had to emphasize a warm deviation from MOS for the contest.

Short-Term (now through Wednesday)

Firstly, the consistency in timing and intensity displayed by the 12z NAM, GFS, and EURO is stunning, it's a rarity to see all 3 with near exact similar solutions for precipitation this weekl. Essentially, the remainder of today will be influence by gravity wave cloud formation in addition to upsloping showers.  Tuesday, the upsloping will be key to the formation of showers across the ridges and valleys of the Apps,  for the cold front carrying the synoptic lift will be falling apart prior to its traversal of the mountain range. Showers will remain scattered on the far lee side out by the Delaware River, and there will be little in the way of post frontal clearing as itas trough will affix itself to the certral area of the state, and rotate clockwise until a new warm front forms within the trough as midweek moves along

Long Term (Wednesday evening into the weekend)

As the trough realigns itself for the warm front's formation, Thursday will feature a steady increase to the southerly component of the wind(15 panel NAM shows this well) this will lead to a steady warm conveyor that will setup along the eastern U.S., giving potential for near 80 degree temperatures despite the GFSX MOS output. This will conflict, however, with  upsloping ahead of the main frontal  bands, scattered storm activity will be prevalent Friday afternoon. the potent front will combine with upsloping to produce some thunderstorms for Friday evening, however there has been nothing to suggest that model timing is off, for distinguishing features have yet to form.  

Thursday Afternoon Technical Discussion

Synopsis:

After experiencing early summer-like weather during the first half of the week, temperatures will now continue to settle at or slightly below normal. Cloudy and dreary conditions will continue into the evening before a cold front brings showers and thunderstorms overnight into Friday. High temperatures will differ throughout the Commonwealth as we saw today with southern portions reaching the mid-60's, western regions remaining in the mid-50's, and eastern areas flirting with the 50 degree mark. Saturday will be beautiful, but chilly for most of the state with a few scattered showers. On Sunday, expect mostly sunny skies with temperatures staying in the mid 50's. As we roll into next week, a warming trend will set in as well as some unsettling weather.

Short-Term:

The cold front that's been almost stationary will begin to trek northward as a low-pressure system over Ohio will move north northeastward. A secondary low pressure will develop off the Delaware coastline Friday night that may create some extra energy to any precipitation along the eastward moving cold front. Areas in SE PA may see higher amounts of rain due to this secondary low development. By Saturday, temperatures will be below normal as a trough moves over the area.

Long-Term:

As a short-wave trough creates a low-pressure system over the central plains, a weak ridge east of the system will bring a brief period of above normal temperatures beginning late Sunday night into Monday as this ridge causes warm air advection from the south. By the middle of next week, temperature should stay around average along with unsettling conditions due to a stationary front north of the area.

Michael DiDomizio
The Pennsylvania State University | Class of 2013
B.S. Meteorology | Forecasting and Communications Option
Minor | Climatology

Thursday Morning Forecast

Synopsis: 

After experiencing several strong thunderstorms roll through the region yesterday, we can expect cooler, cloudier day today. Temperatures will remain in the upper 50s today with cloudy, dreary conditions and a slight chance of thunderstorms. There will be a continued chance of showers as we head into Friday and Saturday with temperatures around 60 on Friday and around 50 on Saturday. We will then begin to clear out as we begin to head into the beginning of next week. Temperatures will also begin to rise to near 70 by Tuesday.

Short Term: 

The system that spawned the severe storms we saw yesterday will continue its ENE trek through today and tomorrow as it moves just south of the Great Lakes. The low has closed off at 500 mb, which will inhibit deepening of the surface low today. Tomorrow, though, a small kink in the upper-level trough will boost divergence and help the system regain its strength as it moves over NY and into New England Friday afternoon. High temps are up in the air (pun intended) today due to the stationary front in PA. Areas south of this front will see highs in the 70's, while areas to the north will likely not rise past the mid-50's.

Long Term: 

On Saturday, the surface low will have fully occluded as it weakens and moves northward. Due to the cold occlusion, most of the precipitation associated with this dying low will be located to the north of the warm front in upstate NY. Current model analysis, though, shows a secondary low developing at the triple point around 06Z Saturday morning. This low will spin up just off the coast of Cape Cod and, located in the right entrance region of a 250 mb jet streak and aided by 500 mb PVA, strengthen a bit as it moves northeastward up the coast. Expect cooler temperatures and lake-enhanced clouds in the wake of the low on Sunday and a bit of warming on Monday as our next system develops over the northern Plains.

Monday Night Technical Discussion

Synopsis

 

A weak cold front will push southeast across the state overnight and bring a chance for some showers and thunderstorms for western and northern counties. Warmer air will push back in Tuesday with another chance for scattered showers and thunderstorms across the northern and northwestern portions of the state during the afternoon and overnight. This pattern will persist through Thursday, as a cold front passes through Thursday night bringing scattered showers and storms across the entire state lasting into early Friday afternoon. Cooler air and drier conditions will follow for the end of the weekend in the wake of the cold front.

 

Short Term (Monday night thru Wednesday night)

 

A cold front will push southeast across the state overnight tonight enhancing instability and increasing potential for scattered rain showers and thunderstorms for northwestern counties. The 12Z NAM has the precipitation sticking around the mountains to the west overnight as the 12Z GFS has the precipitation falling across much of the state. Warmer air to the southwest will push into the state Tuesday and bring a chance for scattered showers and storms for western and northern counties during the afternoon and overnight. This pattern of warm air and scattered showers and storms during the evening will persist through Thursday.

 

Long Term (Thursday into the weekend)

 

Thursday will be the last day of warm temperatures, as a cold front will push across the state Thursday night bringing widespread rain showers and thunderstorms across the state lasting into early Friday afternoon. Both 12Z GFS and NAM agree with showers beginning in western PA around 00Z Friday. Cooler air and drier conditions will follow in the wake of the cold front for the end of the week and temperatures will moderate for the beginning of next week.

 

~ Aaron Herbert

Monday PM Disco- a week of Warmth 4-8-2013

Synopsis

Upon the arrival of a warm air mass to kick off the week's summer preview, a few thunderstorms rolled through the valleys. Expect to see more of that to our north as the week progresses, but the main issue is the bulky ridge that has positive 500mb height anomalies over the state, giving us temperatures well in the 70s for the week. Many bands of precip will pass to our north, and those will be associated with a front that will lag in movement until the ridge recededs and ushers in the system for Friday. Beyond that, expect a return to normal

Short Term (Now through Wednesday)

The outlook for this week will feature clouds and sun with sporadic showers, primarily to the west. The 12z Nam implied scattered showers along the western areas related to the stream of positive vorticity that the NAM throws in for Tuesday and Wednesday, as these bands appear to miss the state and join the northern cluster. The 15z SREF shows two small low pressure cells that pass along the northern border overnight, which isn't well agreed with the NAM and GFS runs from 12z. this is based on the overall descrpancy tat many of the models face in these types of patterns. Nonetheless, there is an agreement on cloud cover and temperature ontasts, the only issue is how the NAM build convective precip.

 

Long Term (Thursday onward)

Thursday will serve as the transition day in which a cold front ill prepare to hit Thursday night into Friday. The models generally agree on front timing, with the rain initiating in the west before 0z, starting as light shoers, turning to heavier rain and thunderstorms by around 4z. topographic lift would develop more of the tormy activity, yet, lack of  a westerly component to the wind could prevent significant buildup. Beyond this, MOS temperature outputs for Friday keep the state warm, yet the presence of rain should begin more of a noticeable drop in tempertures, and with the dryslot projected to affect the state by mid afternoon Friday, the night to follow will most likely be drier and cooler than modeled.