Synopsis:

Winter is back in full force with snow squalls and chillier temperature across the state.  Bands have been persistent through the western half of the state all day.  Snow showers will taper off  overnight except in the northwestern portion of the state where lake effect snow bands will be in full force through Saturday morning.  The weekend and early next week will feature a few clipper systems and below average temperatures.  Snowfall as of right now looks to be on the light side with only a few inches possible away from the lake. 

Short Term:

Snow squalls are still persistent across much of the western portion of the state.  These bands will likely taper off overnight across much of the state except near the lake shore of Erie.  Accumulations in the snowbelt in Erie and Crawford counties could reach a foot by Friday night.  Winds will be strong which will create blustery and white out conditions.  A weak clipper disturbance will move through Saturday bringing light snow showers across much of the commonwealth.

Long Term:

Models in agreement that temperatures will remain below average heading into Sunday and early part of next week.  Temperatures won't be quite as cold on Sunday as a weak disturbance moves through allowing minor warm air advection.  As that system moves out another clipper from Canada will filter back in bringing light snow showers.  No large systems expected in the forecasting period as well as extreme chill or warmth.

Thursday Morning Discussion

Synopsis:

After record breaking warmth, thunderstorms, and heavy rain yesterday, we have turned back into a much more wintry pattern.  Temperatures are currently down into the low 30s across the commonwealth with numerous snow squalls.  We can expect these much colder, wintry conditions to persist for the foreseeable future.  Although there are no major storms in sight,  we may experience a couple small clipper systems that could drop a small accumulation.

Short Term:

Presently, there are numerous snow squalls across the region.  Expect these snow squalls to persist for the majority of the day across the eastern half of the region.  Temperatures will remain steady or possibly fall a bit throughout the day as cold, dry air rushes in.  Areas in lake-effect snow belts such as Erie, PA should expect bouts of very heavy snowfall resulting in significant accumulations.  Winds will also be very strong across the region with gusts up to 50 mph.

Long Term:

The long term forecast looks seasonably cold with chances for light snow or snow showers almost every couple days.  There are no real threats for any large weather systems to affect the region over at least the next week.  The latest runs of both the GFS and the ECMWF both show a couple clippers coming over the region with some light snow and possible a light accumulation.  The first one of these clippers is expected to cross the region sometime around Saturday night. 

Wednesday Night Discussion

 

Synopsis:

Currently, the commonwealth is dealing with the latter part of the low pressure system that has been producing severe storms from the Mid-Atlantic all the way down to the Gulf of Mexico. As the cold front finally makes its way through, we will see colder temperatures make their return to the region. These colder temperatures will remain until early to mid-next week as we run into a snowy pattern the next few days.

 

Short Term:

Presently, rain showers cover the entire commonwealth while most spots have recorded at least an inch or two of precipitation. Heading into Thursday, temperatures will make their way back to average as parts of the region will be affected by snow showers. These lake effect snow showers will predominately remain in Northwest PA, however some strands could stretch their way further across the commonwealth. Snow showers will continue into the evening and overnight with moderate winds.

 

Long Term:

Besides some lake effect snow showers, our next chance for some accumulating snowfall will be on Saturday late afternoon into the evening. Light accumulations are only expected from this clipper system as it moves on out fairly quickly. However, on the 0z GFS we can see that another system comes right behind the first giving Sunday the possibility for more snow showers. Even though this system shouldn't produce excessive snowfall, this situation should be monitored by upcoming forecast shifts. A similar pattern sets itself up for early to mid-next week with more chances of precipitation, most likely snow.   

Tuesday Night Discussion

Synopsis: Currently a stationary front is draped across the commonwealth bringing stagnant clouds and humid conditions. A quite powerful cold front will sweep across Pennsylvania tomorrow, as a low pressure system marches northeast into eastern Canada. This will set the stage for generally a colder and snowier pattern, that has been the norm for the latter half of this month. 

Short term: Currently flood watches are in effect across the southeast third of the state. The ground is already fairly saturated and with new rainfall amounts in excess of an inch expected over the course of tomorrow, local flooding may become an issue. Heaviest precipitation, however, may occur in the southwestern portions of the state, where thunderstorms may produce locally heavy rains. Thunderstorms are likely to be most severe in the southwest, where conditions will be most unstable. Although, a rumble of thunder can be expected across the commonwealth. After the cold front passes through, a strong northwesterly flow will set into place.

Long term: The lake effect machine will set up and produce accumulating snow across most of the northwestern portions of the state. This will linger into early this weekend. Colder conditions will stay in place through the weekend and into early next week. A weak clipper system will pass through early Friday dropping a few snow showers across the region. As of now, it appears the system should slide just south of the Mason-Dixon line, however; it should be monitored in the upcoming forecasts. Throughout the forecast period, weak continental systems will sweep by the Mid-Atlantic, as we are in a fairly progressive pattern. 

Dakota

Monday Night Technical Discussion

Synopsis

 

Warmer weather will continue to make its way into the state for the beginning of the week. A strong cold front will follow closely behind bringing a chance for some severe weather ahead of the front Wednesday. As the cold front moves through, arctic air will return for the weekend.

 

Short Term: (Now thru Tuesday Night)

 

Showers will diminish across the state overnight as the area of low pressure moves into New England. As seen on the 500mb GFS/NAM models, a strong ridge will pass over us on Tuesday as a trough down-stream to the southwest approaches. The ridge will bring warm air advection and temperatures in the 40's for most of the state with 50's possible for southern and western portions of the state.

 

Long Term: (Wednesday thru the weekend)

 

Increased pre frontal advection will lead to temperatures in the upper 50's statewide on Wednesday. Models such as the GFS and NAM have been trending warmer, so would not be surprised to see some areas reach 60 degrees. The NAM has the cold front moving through slightly quicker than the GFS, but both models agree on rain entering the western portions of the state around 15Z on Wednesday. Warm temperatures during the day on Wednesday will lead to instability, allowing for widespread showers and thunderstorms as a strong cold front pushes through. Some of the thunderstorms could contain gusty winds and heavy downpours as high CAPE is expected with the low level warm air advection. As the rain exits the state Wednesday night, cold air advection from a northwesterly flow behind the front will bring cold air back for Thursday along with a chance for some lake effect snow for much of northwestern Pennsylvania. The arctic air will keep high temperatures in the 20's for the weekend and a system moving to the south of us could provide another chance for some snow on Sunday.  

A.J. Herbert

Monday Afternoon Disco Fever 1-28-2013

Synopsis

Mild weather is on tap for us midweek this week, but a strong cold front hints at some severe weather Wednesday along the strong cold front that will bring us back into reality Thursday. The ride will be breezy and muggy, but afterwards we'll be stuck with mid-teen wind chills   

Short Term (Now thru Tuesday Night w/hints at Wednesday)

The line of showers that is crossing through now will be officially out of the state in a couple hours, but the ridges and valleys will see some topographic enhancement with spotty, light showers overnight. On Tuesday,  a 500mb ridge will pass over, helping to set up a mean southerly flow throughout the 1000mb-500mb layer. At the surface, the tip of a warm front will graze across the state delivering a light shower or two across the ridges and valleys north of the PA turnpike. Over time, warmn air willadvect helping to kick up the highs into the 40s and 50s for Tuesday, then into the 50s and low 60s Wednesday (this is based on a combo of MOS and DMO, so keep an eye on how these temps fluctuate, its all relative to the frontal organization.

Long Term (Wednesday thru the weekend)

Things get dicey Wednesday as strong OVA helps develop the low that  stems the intense cold front that will be on our doorstep. The tough part here is the timing. The 12z NAM lags the GFS, with the NAM moving the front through an hour or two ahead of the GFS,  though the GFS rushes rain into the state 3 hours faster than the NAM. Nonetheless, both show heavy precip, and the forecasted soundings imply Cb, which imply thunderstorms during the front's passage, so keep an eye on this indeed as the event draws near. The rain essentially  sticks around for the entire day, with the later day heavy rain impacting the Eastern areas the most with up to 2" when it's all over Thursday morning. Beyond this, the strong cold front will put the state highs back below the freezing mark, but we won't see the deep chills that we saw last week. Thursday, the wind chill will be a must to observe, currently, with temps and winds, looks like single digit to low teen wind chills Thursday, moving more into the teens  Friday

Tech Disco 1/28/13

Synopsis:

Freezing rain will change over to rain later this afternoon as temperatures moderate at the beginning of this week. Another strong cold front will bring more snow showers and arctic air after Wednesday. A weak disturbance or clipper provides the state with a chance of more snow on Saturday, but temperatures moderate over the weekend and into the later part of the forecast period.

Short Term:

12Z Hi-res NAM forecasting mixed precipitation throughout this afternoon and changing over to rain around 20Z today. Scattered rain showers, especially along the ridges of central PA, will linger throughout the night and continue into Tuesday where the threat remains. 0Z MOS products bring temperatures near 60 degrees, but combination of fog in the morning and snow cover will keep temperatures closer to 50 degrees Tuesday and Wednesday.

Long Term:

Wednesday night approach of a front will bring more arctic air to PA.  Ahead of the front on Wednesday, winds could blow up to 25 knots. Post front, cold air rapidly arrives from the west and northwest over the lake and will bring moisture to much of the state Thursday and Friday. Uncertain, but a disturbance could affect the state, especially the higher terrain, on Saturday with models in agreement that temperatures hover around the freezing mark for the rest of the weekend and early next week.

Dillon Durinick

Sun. Evening - Big Changes

Synopsis:

A warm front will bring in the wintry mix tonight into tomorrow. A warm-up will commence for Tuesday before an arctic front brings rain and perhaps a few strong thunderstorms on Wednesday afternoon. A rapid cool-down will follow for the end of the work week into the weekend bringing lake-effect snow to the northwestern parts before another storm threatens for the weekend.

Models Used: 18Z GFS, 00Z NAM & Hi-Res NAM, 01Z HRRR

Monday - Wintry Mix:

The 546-DM 500-1000-mb thickness line looks to be the snow-to-freezing-rain line, and the 32°F isotherm will be the rain-to-freezing-rain line. The freezing line will arrive a few hours after the 546-line arrives, and those times are:

Pittsburgh around 2:30 (546) & 5:00 (32F) AM
State College around 8:00 (546) & 11:00 (32F) AM
Scranton around 11:00 AM (546) & 2:30 PM (32F).

The precipitation will last about eight hours for most locations, but a little longer for the Laurel Highlands. Accumulations of snow & sleet will be around one or two inches (locally 3") with ice accumulations of a coating to 1/10" in most of PA (except for interior parts of the northwest and north-central zones where they'll see 1/4" of ice!). Travel will be VERY treacherous.

Tuesday - Warm-Up:

Temperatures at 850-mb will be 8°C, which is about 25-30 degrees Celsius higher than they were on Tuesday. For State College, the surface temperature using the DALR (9.8°C per km) translates to about 65-66 degrees Fahrenheit at the surface. Nice! But there are consequences to the warm-up: a cold front will not only bring rain, but also thunderstorms (some strong) to many areas on Wednesday. Models are also hinting at scattered shower activity for the day on Tuesday due to some instability.

Wednesday - Thunderstorms:

The cold front will arrive in Western PA for the early afternoon hours, and have passed through the Commonwealth around midnight. As the front passes, temperatures at 850 mb will drop as much as 1°C per hour! With those temperature profiles occurring at the peak heating of the day, most of southern and western PA will see intense thunderstorms with heavy rain and gusty winds.

End of Week - Cool-Down & Lake-Effect Snow:

The northwest flow and temperatures at 850 mb returning to the -15 to -20 degree Celsius mark will lead to lake-effect snows across the northern and western areas of the state.

-Jaron Breen

Friday Technical Discussion

Synopsis:

Some light snow on Friday will signal the ends of the Arctic air mass that has been sitting over the state this week.  Behind the snow we will have a shot of cool air for the weekend, but will stay warmer than the past few days. Another stronger system will approach the state on Monday and bring a wintry mix before changing over to plain rain.

 

Short Term (Fri-Sun):

A clipper system is phasing with a southern piece of energy to provide a light to moderate snowfall to much of the mid-Atlantic region. Precipitation is moving in faster today than the models had predicted. Most models expect precipitation to begin around noon in western Pennsylvania, but as of 10:00AM snow is moving into the state.  So snow should begin 2-3 hours earlier than previously expected. Banding will move into southwestern Pennsylvania, leading to a moderate snowfall in that region. Areas of southern Pennsylvania near the Mason-Dixon Line may also see some moderate snow as a vorticity maximum swings along the PA-MD border later this afternoon. Total accumulations are expected to be 2-4" across the state with lesser amounts in the northeast and higher in the southwest where 4-6" is possible in higher elevations. A weak cold front will push through behind the snowfall with a reinforcing shot of cool air. This air will not be as cold as this past week, but will keep temperatures in the 20's for Saturday and Sunday statewide. A strong high pressure system at 1034mb will move in for the weekend leading to sunny skies Saturday and Sunday.

 

Long Term (Mon-Tue)

Models show a system moving up from the south on Monday into the cold air in the mid-Atlantic. This will lead to a CAD situation with many areas of the state seeing precipitation starting as snow, sleet, or freezing rain. As the system continues to push north, it will bring up some warmer air from the south that will eventually overtake the cold air damming and change precipitation over to rain. The southerly flow from this system will bring much warmer air for early next week and by Tuesday some areas may find themselves in the upper 50's. 

Thursday Evening Technical Discussion

 Synopsis

High pressure will slowly weaken during the evening as it moves off to the southeast. It will make romm for a weak clipper system that will cross the commonwealth tomorrow and strengthen as it approaches the Atlantic Ocean.  The clipper should deliver a wide swath of 1-3" of snow across the state. During the weekend, scattered snow showers will continue before temperatures begin to moderate as we approach the start of next week.

Short Term (Friday morning through Saturday evening)
A weak low pressure system moving through the northern plains tonight will scoot off the east bringing snowy conditions for the Commonwealth Friday. During the morning, skies will become cloudy and the snow will start falling across western areas around midday. This will keep temperatures on the cool side as maximum temperatures struggle to reach the mid-to-upper teens. The majority of the state will see around a QPF of 0.1-0.2 inches. Due to temperatures in the teens, there will be very high snow to liquid ratios which may reach 15:1 to 20:1. These high snow ratios will allow 1-3" of snow with localized amounts of up to 4". As the upper-level trough weakens and moves off to the northeast, temperatures will increase on Saturday as highs reach the mid-to-upper 20's. A decent northwesterly flow will allow more lake-effect snow showers to affect the central and western areas of the state Saturday.

Long Term (Sunday to Tuesday)

Behind this low pressure, a ridge of high pressure will control our weather pattern and give us clear skies Sunday. Under these clear skies, high temperatures will reach the mid-to-upper 20's with a few southeast areas approaching 30 degrees Fahrenheit. By Sunday, the upper level trough will retreat and the ridge will build in from the west. Ahead of a low pressure system, warm air advection will commence and cause lows to only reach the upper teens and lower 20s. As clouds increase, the cold air will begin to erode. How long the cold air will remain is yet to be determined which means there is the chance for a smorgasbord of precipitation. If the cold air is stubborn enough, it could lead to mixed precipitation with wet snow, sleet and freezing rain. High temperatures will reach the mid 30's across the much of state Monday. As the warm air advection increases Monday night, low temperatures won't fall much and with Tuesday's high temperatures approaching the mid 40s, all the mixed precipitation will turn to rain.

CWS Technical Discussion

Technical Discussion

Synopsis…
High pressure will continue into this evening, but will quickly retreat to the southeast as a 500mb short-wave trough surges in from the northwest. A weak and disorganized clipper system will sweep by tomorrow and will gain strength once it reaches the Atlantic. A wide swath of 1-3" of snow is expected by this system. Scattered snow showers will continue into Saturday and temperatures will slowly begin to rise heading towards next week.
Short Term (through Saturday)…
A weak low pressure system currently in the northern plains will quickly move east southeast causing unstable conditions for the Commonwealth on Friday. Clouds will thicken and snow will begin to fall starting from the west around 1 p.m. High temperatures remain chilly only reaching the mid-to-upper teens. The majority of the state is only looking at a QPF of .1-.25 inches. With temperatures in the teens, snow to liquid ratios may exceed 15:1. A total of 1-3" of snow is expected with local amounts up to 4". As the upper-level trough that has been sitting over the eastern United States begins to weaken, temperatures will slowly being to rise into Saturday as highs will peak into the mid-20's. A northwesterly wind will enhance some more lake-effect snow and many of the squalls may scatter throughout the state on Saturday.
Long Term (Sun-Tues)…
High pressure will dominate a large portion of the northeast on Sunday giving way to an abundance of sun. High temperatures will be in the mid-to-upper 20's with some areas hugging 30 degrees Fahrenheit. As Sunday evening approaches, the trough will begin to retreat as a weak ridge moves in from the west. Warm air advection is expected to keep lows on Monday morning to be in the upper-teens, but quickly rise into the 20's. Clouds will begin to increase as a system from the west approaches. The cold air may stick around longer than the models predict, so forecasting this storm may be a little uncertain this far away. Overall, the outcome may lead to mixed precipitation along the lines of wet snow, sleet and freezing rain. High temperatures will sit around the freezing mark of 32 degrees. Warm air advection will continue into Monday night and Tuesday so any mixed precipitation will turn to all rain. High temperatures on Tuesday are expected to be in the mid-40's. 

Thursday Morning Forecast

Synopsis: 

For the past couple days we have experienced the coldest weather of the season across the region. This frigid weather will continue through tonight when temperatures will approach zero degrees. Tomorrow afternoon light snow will break out across the region and continue through the evening. Accumulation will be light, on the order of 1 to 3 inches. Heading into next week temperatures will begin to rise with the approach of a new weather system. Expect temperatures to be in the mid 40's with a chance of rain by Tuesday and and Wednesday.

Short-Term:

Models are trending towards a less-significant snow event across the commonwealth with the approach of Friday's system. Expect 3-4" in areas to the south, 2-3" in central PA, and around 1" across the northern tier, with the exception of locations to the NW, where lake-effect snow showers will bring an additional inch or two to the area.

Long-Term:

After the storm, a general warming process builds in with temps rising to the upper 30's by Monday. These temps will be warm enough to bring the chance of mixed precipitation as our next system rumbles through on Monday with its associated warm front swinging through our region.  Conditions brought about by this mixed precipitation (rain, snow, freezing rain, and ice) can be more dangerous than either rain or snow showers. This system is definitely one to keep watch on.

Monday Evening Technical Discussion

Synopsis:

                A cold Arctic air mass has overspread the state and will continue to provide cold air for the next few days. Lake effect snow showers should continue for northwest portions of the state with a couple more feet possible over the next two days. Expect a weak clipper to move north of the region Wednesday afternoon, allowing for some light snow in northern Pennsylvania. A stronger system should move through on Friday possibly providing a moderate to heavy snowfall for the state.

Short Term: Tue-Thu

                Cold air has overtaken the state of Pennsylvania as an Arctic front passed through the state on Monday. The northwest breeze and warm lakes have created lake effect snow for northwestern Pennsylvania where as much as 15" has fallen by Monday evening. Models show the lake effect continuing through Tuesday with a much as 2' of additional snow possible. The models also show extreme cold moving into the state with surface temperatures stuck in single digits and teens, while 850mb temperatures fall below -10^oF. Breezy northwest winds will lead to wind chills below zero at times. This is a true Arctic air mass that Jack Frost has sent down to the state of Pennsylvania. A weak clipper system should push north of the state on Wednesday bringing a touch of light snow to northern Pennsylvania. Cloud will move back in later Thursday ahead of our next system for Friday.

Long Term: Fri-Sun

                Yet another snowstorm will be pushing through the state on Friday. A clipper dropping in from Canada will phase with energy in the south to provide a storm for the mid-Atlantic. Models are in disagreement of the timing as the NAM brings the snow as early as 12z Friday and the EURO/GFS hold off until around 18z Friday. The models also disagree with the precipitation amounts as the NAM gives much of the state 0.5"+ of liquid precipitation. The GFS/EURO are much drier with an average of 0.25"-0.5" liquid across the state. The EURO/GFS is favored at this time as the NAM is in its long range right now and seems to be phasing the northern and southern branches of the jet stream too late. One thing that the models are agreeing on is that temperatures will remain cool in the teens to lower twenties. This will allow for higher than normal snowfall ratios of possibly 20:1. Once the storm passes through, high pressure will move in and provide a reinforcing shot of cold air for the weekend.

Zachary Fasnacht 

MLK day Afternoon Disco

Synopsis

The mnst bitter cold of the season is on its way. The artic flow will be most intense tomorrow with subzero wind chills, yet the rest of the week will just remain frigid while a grey sky looms overhead for the bulk of the week, leading to a dreary few days of arctic-esque cold. A Nor'easter will pose a threat later in the week, so this should be on watch as the week progresses.

Short Term (Now through Wednesday night)

As the arctic front moves through the Northeast, light snow showers will begin to dissipate throughout the state overnight, leaving Erie with its own confined Lake effect setup.  The front will surpass the far eastern boundaries overnight, taking with it an intensifying pressure gradient that will help kick off 20mph winds for Tuesday. these surface winds will bring forth the subzero/nearzero wind chills for tomorrow afternoon.  at this time, in the upper levels. The flow will be depositing air out of the Yukon, and the 500mb longwave trough will help keep the cold air in plavce for the next week as it continues to dip further south. High pressure will start to build in overnight Tuesday, helping to calm, the winds, but keeping lows within the single digits statewide.  The dipping trough will progressively push this high pressure into the Southeast U.S., leaving us with a mean westerly influence for the day.

During this time, the WNW winds out over Lake Erie will intensify their ;ake effect snowbands, yet the models downplay the extent of the areal coverage. The SREFs indicate about 6 to 9 inches of new snowcover between now and Wednesday night, and the lake effect snow will not die out until Thursday afternoon. The NAM and other hi-res models keep the most intense snowfall confined to Erie and areas about 20 to 40 miles from the lakeshore.

Long Term (Thursday and Friday)

Here's where things get tricky, starting around 0z Thursday, the 12z NAM and GFS solutions begin to differ immensely.  By 18z Thursday, they both agree on a rather clear and Sunny Thursday, but around 0 to 6z Thursday, the solutions feature thick clouds blanketing the state with the GFS, and patchy clouds with the NAM. The NAM is colder during these days as well, by about 4 degrees on the low and high for both days. On Friday, the zoomed out GFS implies a strong Nor'easter over PA at 12z, but at 0z the GFS shopws no signs of the system, with it still developing in the Central U.S. at this time. Conversely, the Nam shows a semi-organized, intensifying cyclone around Chicago. His implies that the NAM will be faster than the GFS on this system, but it should be monitored more closely s the week progresses.

As far as Erie's concerned, between now and 0z Friday, the SREF ensemble mean gives them a foot of snow, with the members ranging from about 10 to 16 inches by that time.

Submitted by Steve Engblom Dos