Saturday morning forecast discussion

Synopsis:

A high pressure area will set up over the Commonwealth today, which will lead to mostly sunny conditions with warm temperatures and light winds.  A warm front will approach Sunday morning, giving areas a possibility of rain.  The warm front is expected to move through Sunday night.  Once this happens, an approaching cold front will become stationary.  As a result, rain will spread across the Commonwealth Monday and Tuesday.  The cold front will then pass through Tuesday night into early Wednesday morning. Once the front passes, we will see a couple of dry days with at least some sunshine before our next chance of precipitation on Saturday.

 

Short term:

Rain is definitely in the forecast.  A weak warm front will move through around Sunday evening, bringing a few showers.  The WRF models have the rain first arriving between 12z and 18z Sunday.  A cold front will then stall out over the Ohio River Valley (right where they don't need it) and bring us a two-day period of rain Monday and Tuesday.  The WRF and GFS models are also consistent in that the first band of rain moves through the Western part of the Commonwealth between 15z and 18z Monday.  Another band comes through at 12z Tuesday. These will be the main bands forming along the stationary front, but overall, there will be a persistent pattern of rain before the front finally moves through Tuesday night. Rainfall amounts can be expected to be between one and a half and two inches from this cold front. Once the front passes, we will see calmer weather move in.

Long term:

After the cold front finally passes through early Wednesday, high pressure will begin to build. Both the 0Z and 6Z GFS shows much improving conditions for the state on Wednesday, as high pressure will cause the 540 line to move well northward by 18Z. Both the 0Z and 6Z GFS runs show high pressure over the state for Thursday into early Friday.  The 6Z GFS shows rain arriving by Saturday at 0Z, while the 0Z GFS run shows the rain arriving between 6Z and 12Z the same day. The 6Z run shows the main low pressure system associated with the cold front moving through the Commonwealth by Saturday, while the 0Z run has the same low drifting through the UP (upper peninsula) of Michigan. The 6Z run shows the low pressure system moving eastward more quickly than the 0Z run, which will probably lead to less rain across the Commonwealth.

Wednesday Evening Technical Discussion

Synopsis

Temperatures will remain warm until a cold front passes through the area Thursday afternoon.  This cold front will bring colder temperatures and wetter weather for the next couple of days. After this low pressure system and cold front moves through, skies will remain cloudy and there may be a few rain showers for most of the state. Once this area of low pressure system heads off to the northeast, high pressure will begin to dominate the weather by Saturday. This should allow for less cloudiness and increasing temperatures for the weekend.

Short Term (Thursday morning to Friday evening

Temperatures will remain very warm throughout the state as we still are in the warm sector.  This will end when a cold front will move from west to east across the state during the day Thursday. Showers will be associated with this front as well. Temperatures will drop steadily behind the front and will be chilly overnight Thursday. Friday will remain cloudy and below normal as a shortwave moving over the area promotes clouds. Once this shortwave leaves the area, high pressure will gain control and give us better weather heading into the weekend. 

Midterm (Saturday morning to Sunday Night

As high pressure builds in Saturday morning, skies will become clearer and temperatures will moderate as well.  Heading into Sunday, the weather will remain pleasant with temperatures around normal.

Long Term (Sunday night into Tuesday morning

Another front will move through the area Sunday. This will bring some cooler temperatures Sunday into Monday. Skies will remain mostly clear and temperatures will be moderating Monday into Tuesday.

-Matthew Mehallow

Wednesday Afternoon Technical Discussion

Synopsis:

The stationary front that has been strewn across the heartland of America over the past few days will remain in place tonight. This frontal boundary will continue to pump energy up into Pennsylvania and keep conditions ripe for convective development. This will cause warm and humid conditions tonight with the possibility of thunderstorms especially in the western portions of the state as a low pressure system slides northward along the front and into Canada. This system will finally break down tomorrow and a cold front will propagate west to east through the day. Heavy rain will be associated with this cold front and thunderstorms will again be a possibility in the eastern half of the state. Behind this system a shortwave will swing through the state on Friday keeping the skies cloudy and even bringing a few rain showers to the state. High pressure will take control of the eastern seaboard by Saturday allowing for decreasing cloudiness and moderating temperatures to dominate the weekend. Our next system will approach the state on Sunday evening bringing another shot of wet weather for the beginning of the next work week.

Short Term (Tonight):

The atmosphere is ripe for convective initiation as the stationary front that has caused numerous severe weather reports this week remains mired in the Mississippi River Valley and Northward into the Great Lakes region. Although, the WRF and GFS don't show exceptionally strong storms developing this evening; the National Weather Service in State College has issued a Tornado Watch until 10pm. There is a substantial amount of CAPE this evening and correct amount of wind shear for vertical cumulonimbus cloud development. Both the High Resolution Rapid Refresh and the experimental 4km WRF models show a line of storms firing west of the Alleghenies, rapidly intensifying and then pushing eastward. The radar is beginning to pick up on this line however, the satellite imagery still doesn't look too impressive (Texture isn't impressive and cloud anvils have yet to glaciate.) But, I feel that this line will rapidly develop over the next few hours and produce some severe weather. (Although, probably not a tornado).

Mid-Term (Tomorrow):

The persistent weather pattern will finally break down tomorrow and the final cold front will move west to east through the state. Rain should begin by the morning in the west and will slowly propagate eastward. Current model guidance suggests that the system should be through the state by tomorrow night; however, the guidance hasn't been perfectly consistent so keep an eye out at later shifts. The timing is important because the later in the day the front passes through, the warmer it will get. And due to the instability of the atmosphere, warmer conditions will correlate to a higher probability of severe weather as opposed to the synoptic thundershowers which are currently being modeled.

Long Term:

On Friday a shortwave will swing through and cause cooler conditions and rain showers. High pressure will take over for the weekend before the next storm system approaches on Monday.

RJ Patrizio

technical discussion

Synopsis

A series of low pressure system will ride up through the ohio valley and great lakes over the next several days. This will lead to continued unsettled weather. The pattern remains in place until about Friday when the thunderstorm activity should diminish as the last low pressure moves up into Canada and its cold front pushes through.

Short term

The train of lows into the great lakes region will cause unsettled weather over all of Pennsylvania. A strong southerly flow between the lows to our west and a large high off the coast in the Atlantic will advect in plenty of warm moist air. As a consequence, our temperatures should be well above average through Wednesday and then seasonal on Thursday. The warm moist air (high theta e) and lifting from the areas of low pressure put us in a very favorable environment for widespread thunderstorm activity. Some of these storms could turn severe. On Thursday the cold front should pass, shutting of the thunderstorm activity.  

Long term

The cold front will usher in a quick shot of below average temperatures for the day on Friday. The cloudy skies should also slowly clear out of the state as a high moves in. The high pressure should bring about some very nice weather on Saturday with seasonable temperatures and mostly sunny skies.
Steven Fuhrman

4-26-2011 Technical Discussion

Technical Forecast Discussion

Synopsis:

Scattered showers and thunderstorms will continue to affect our region. Large and vigorous low pressure systems situated over the lower Midwest will continue to provide the necessary instability for convective rain developments. The high pressure ridge located over the Atlantic Ocean will also continue to pump in moist air from the south. Expect scattered or isolated thunderstorms to develop later in the day on Tuesday and continue into Tuesday night, some of the storms could be on the strong side. Expect a similar weather pattern for Wednesday. However as the low pressure's cold front approaches, the showers and thunderstorms will gradually organize into lines late Wednesday night. The line of showers and thunderstorms should sweep through some time Thursday morning. Behind the cold front, the skies will gradually clear and temperatures will fall back to seasonal. Expect sunny skies on Friday and a nice weather to start the weekend.

Short-term (Tuesday – Wednesday):

The short-term synoptic setup favors the development of scattered showers and thunderstorms over the region, especially in the afternoon hours when day-time heating provides the atmosphere some extra instability. A vigorous low pressure system will continue to strengthen over the Midwest as a very strong jet-stream pushes eastward across the Rockies. Ahead of the storm system, high octane moist air will overspread the Midwest, Southeast, and Northeast. Combined with very strong jet-stream and high CAPE instability, severe thunderstorms will continue to develop across the Midwest on Tuesday just like past couple of days.  Also expect some scattered showers and thunderstorms to develop here in the Northeast as day-time heating combined with high dewpoint temperatures, will create some instability in the atmosphere. We still can't rule out the possibility for severe thunderstorms as the CAPE will be marginal for supercell developments.

Looking elsewhere in the nation, the aforementioned low pressure system will spin northward into upper-Midwest. The 500-mb low will cut itself off from the main jet-stream. However, another area of PVA and jet-streak will cross the Rockies early Wednesday morning; these will generate another strong low pressure over lower-Midwest. Unlike the first low pressure system, this new storm system will slowly push towards the northeast. Its associated cold front will finally sweep the moisture eastward. Expect lines of showers and thunderstorms to slowly migrate eastward on Wednesday. However here in the Northeast, we are still going to see scattered showers and storms to develop later in the day on Wednesday.

Mid-term (Wednesday night – Thursday night):

The lines of showers and thunderstorms will finally approach the state late Wednesday night as the cold front nears. The timing of this frontal passage differs among the model guidance. The GFS, ETA, and RSM are all on the faster side of the spread, suggesting the cold front should sweep through the western and central portions of the state sometime early Thursday morning. On the other hand, the WRF is delays the progression of the jet-streak crossing the Rockies, thus suggesting the lines of storms should pass later in the day on Thursday. If the front shall pass the central portions early in the day, only expect the possibly of some strong thunderstorms for eastern PA as day-time heating initiates. However if the storms shall pass later in the day as the WRF suggests, central and eastern PA may see some strong storms in the afternoon. The skies should gradually clear out Thursday night across the state after the front passes through.

Long-term (Friday – Saturday):

After the front sweeps through, some much needed drier air will finally filter into the region. The temperatures will fall back down to seasonal. However, the winds will also quiet strong behind the storm system. Expect partly cloudy skies and breeze conditions on Friday. As the storm system pulls away, the winds will gradually die down. Overall, it looks like we will have a nice start to the weekend.

 

David Wang

TECHNICAL DISCUSSION

…Synopsis….

A stationary front covering a lot of the northeast will be turning into a warm front as it moves its way eastward. The front appears to be moving faster than normal as a lot of places in PA including State College, PA busted by over 10 degrees today. The warm sector of the warm front will stay over most of PA and for the remaining part of the week triggering thunderstorms across PA. An extensive amount of precipitation is expected over PA again as it may rain every day this week.

…Short Term…

The next few days should be mild and muggy. Temperatures will be in the 70s and could hit 80 in some places. Thunderstorms may be severe at the beginning of the week in some places. The 12z runs of the UK, Canadian, GFS, and WRF all agree on a large wave of positive vorticity advection occurring in the mid-west. By Thursday, the system looks developed, but the WRF model has it developing more towards Friday. Precipitation is expected every day this week according to the European model, which holds true to the rainy trend PA has been experiencing the past few weeks.

…Long Term…

After the next few days of warm weather, a developing low could head towards PA or slightly north of PA. The path the low takes will decide the potential for thunderstorms later in the week and the amount of precipitation. The warm sector of the warm front will leave around Thursday, so temperatures will drop substantially after Wednesday, but temperatures will still be relatively mild. Rain weather is still expected at the end of the week.

 

Stephen Quinn

Technical Forecast 4-25-11

Synopsis...

Unsettled weather will continue over much of the eastern US as a slow moving trough keeps the stationary frontal zone set up from Texas through the Ohio River Valley from moving very much throughout the week. Not until Friday will the final low pressure system depart into eastern Canada to allow a high pressure system to move into the eastern US.

 

Short Term...

Today and tomorrow looks to be wet, warm, and humid, but the exact timing and location of the rain and thunderstorms, but both the GFS and WRF models generally show an increased chance of rain over the western part of PA. A slight break in the precip may occur tuesday morning and early afternoon, but then will pick up overnight. The Storm Prediction Center has issued a slight risk for severe thunderstorm potential over western and central PA for the next couple days as warm weather and plenty of moisture will be pumped into the area.

 

Long Term...

The wet weather will continue, but the GFS and WRF models slightly disagree on the timing of when the low will depart towards the end of the week and the amount of precip behind the cold front. The GFS model shows the low pressure system spinning up and kicking the cold front through PA sometime midday on thursday, but the WRF model shows it passing through towards the evening. The WRF model shows a lot more precipitation wrapping around the low over the Great Lakes compared to the GFS model, so we could expect to see a few showers following the cold frontal passage on thursday and friday. We should at least see a glimpse of sunshine finally sometime on friday and most likely for saturday.

 

Josh Aikins

Sunday Afternoon Tech Disco

Synopsis:

A stationary front currently sitting across the central part of the state will keep clouds and showers around over the next day or so. It will eventually transition into a warm front and move northwards on Tuesday, bringing above average temperatures, along with a continued chance of showers through Wednesday. A cold front will sweep through Wednesday night bringing an end to the very warm temperatures but also a decreased chance of precipitation.

Short Term:

The stationary front currently draped across the state is creating a large north-south temperature gradient, with temperatures hovering around 50 in the northwest and into the low 80's in southeast sections. Thick cloud cover along with intermittent showers across the northern half of the state is also aiding in keeping temperatures down. Some breaks in the clouds is allowing the southeast the really warm up. These warm temperatures and relatively high dewpoints (upper 50's to low 60's) are creating some instability (CAPES of over 1000J/kg) and t'storms are beginning to pop up in southeastern counties as we speak. Scattered showers and t'storms will continue through tomorrow along with the impressive north-south temperature gradient. The front will slowly lift north as a warm front tomorrow night, resulting in well above average temperatures tomorrow night.

Long Term:

As the warm front continues to push northwards on Tuesday, strong warm air advection will allow for temperatures to really warm up, with all areas easily reaching the low to mid 70's, with 80's possible in many areas that see more sun. Wednesday will see more of the same, with very warm temperatures and the chance for scattered showers and t'storms. A storm system moving by to our northwest overnight on Wednesday will drag a cold front through the state, putting an end to the much above average temperatures starting on Thursday. The cooler air will, however, be accompanied by drier conditions, especially as we move into Friday.

Sunday Technical Discussion

Synopsis:

The surprise Saturday sunshine will not occur today as a stationary front sets up over us, becomes a warm front on Tuesday, leading towards a cold front for Wednesday evening.  Temperatures though will be running above average for this time of year.  Thursday looks to be the coolest day of the week.

Short-term:

The GFS and NAM both correctly have showers occurring in the western half of the state for 12z, as shown by radar.  The showers are scattered in nature, and has been taken into account into the forecast.  Also looking at visible satellite, there is a chance for some breaks in the skies later this afternoon.  Clouds will increase for the sunny eastern half as the morning progresses, with showers in the afternoon for them.  The NAM continues the showers in a continuous line into Monday, while the GFS shows more scattered showers.  Going to go with the scattered shower theory and looking at the RH, only at 850 mb is RH higher than 70% for the showers, therefore, for Monday, mostly cloudy conditions when it is raining, but the chance of partly cloudy skies in areas with no rain.

Long-term:

The GFS and NAM both show a warm front pushing through the state as indicated by the isobars but also by the very scattered showers.  This warm front is associated with a storm system that is rounding a very deep trough in the Midwest.  So went with scattered showers under partly cloudy skies, with partial clearing overnight.  Wednesday and into Thursday, I believe the GFS is hogwash, it pushes the cold front way too slow.  The GFS has the cold front pushing though the state beginning on the Western state line about 0z Thursday (8pm Wednesday), and taking all day long on Thursday to push through.  Not going to by it.  Instead, sunshine will come out for Wednesday with a line of thunderstorms pushing through the state during the evening hours.  We clear out for Thursday, but run the risk of sprinkles as the winds will be coming off of the lakes.

For Tuesday & Wednesday, I did not run above 82 for high temperatures, therefore the highest middle temperature I went with for most places across the state was 80, based on the fact I have more sunshine than the GFS and NAM do.

Saturday morning forecast discussion

Synopsis:

 

A series of bands of precipitation (showers and embedded thunderstorms) will make their way through the Commonwealth over the next several days. A stalled cold front is expected to park itself over the state through Monday, and then lift up northwards Monday night, paving the way for summerlike warmth across many areas on Tuesday and Wednesday. This will break, however, with the passage of a cold front during the day on Thursday. After that, we may see calmer weather for a few days.

 

Short-term:

 

Today, a warm front will make its' way across the Commonwealth, enabling temperatures to rise much more than they did yesterday. We saw a few showers earlier ahead of this warm front, but that will be the bulk of the precipitation for today. However, another band of showers will move in for tonight, and then more showers will be had for tomorrow. The cold front will sag slightly south, giving about half of the Commonwealth (the northern half) a break in precipitation. It will be a little cooler temperature-wise, but not much. Then, by Monday, as we start the work-week, the front lifts to the north, which will be the enabling mechanism for warmer air making its' way from the south. There could be some showers and thunderstorms on Monday, particularly in the northwestern areas of Pennsylvania, but it will be a little nicer. Tuesday and Wednesday will be the warmest days, as the 570-mb. height line makes its' approach towards the state. Temperatures in many areas will reach well into the 80s on Tuesday and Wednesday, making it feel more like July than April.

 

Long-term:

 

The end to this unstable weather pattern appears to come on Thursday, when a cold front is expected to pass through the state earlier in the day. This will break the summer-like warmth, and also put an end to the showers and thunderstorms, at least for a few days. The next chance of showers looks to come the following Sunday.

 

Gregory Woloszyn

Saturday morning shift manager

Technical Discussion

Synopsis:

High pressure will build across the region tonight, allowing winds to gradually diminish. Light winds and mostly clear skies tonight will allow temperatures to dip into the 30's across much of the state. A frost advisory is currently in place for Southeastern PA through tonight. The next storm looks to move into Western counties early Friday, bringing the possibility of snow showers across the central and northern mountains. Clouds, rain, and above average temperatures look to remain in the forecast through the weekend and into the early part of the next work week.

Short Term:

Building ridge of high pressure across the region tonight will gradually suppress gusty winds. The combination of light winds, dry air mass, and mostly clear skies tonight will allow temps to dip into the 30's across much of the state. NWS has issued a Frost Advisory for SE counties through the overnight. The next system looks to move into western zones by 15z Friday morning. CAD in northern and eastern counties may allow precipitation to begin as snow before changing over to all rain. 0900 UTC SREF's indicate that the bulk of this precipitation Friday will hug the Mason Dixon line. We can't rule out the chance for stray thunderstorm, especially in the western half of the state. A second, heavier batch of precipitation will move across the state early Saturday.

Long Term:

One storm after another will continue to eject out of the Great Plains through the weekend. Clouds accompanied with rain showers will remain in the forecast into the next work week. Total QPF for the 5-day forecast period ranges from ~1" in SE counties while locales in the NW may receive over 3" of rainfall. Temps look to continue to hang in the 60's over the weekend, with milder air working in by Monday when many locations will be looking at highs in the 70's.

 

Christopher Cornwell