Technical Discussion

Synopsis:

A ridge of high pressure will build over the region through Wednesday.  Expect sunny skies, dry conditions, and slightly below seasonable temperatures every day.  A disturbance is projected to potentially affect the state later in the week, bringing the possibility for showers.

Short-Term:

There were minimal uncertainties in the forecast for Monday through at least Wednesday.  The relatively strong and large upper-level high dominates the weather patterns throughout the state.  Both the WRF and GFS 1200 UTC runs show a nice slot of dry air over the Commonwealth at both the 700 mb and 850 mb levels and no precipitation in the forecast until at least late Wednesday night. Along with other model indications, we forecast lots of sunshine and clear nights through Wednesday.  Temperature projections were consistent, slightly below seasonable across the board with very chilly nights.

Long-Term:

The most uncertainty in the models this week is with regards to the track and extent of the low pressure system encroaching upon the region late Wednesday into Thursday.  Currently, the 1200 UTC run of the GFS projects a trough developing, deepening, and progressing from the northwest towards the Mid-Atlantic as the week progresses, with a cutoff upper level low developing over the Texas/Gulf region by late Wednesday.  The GFS has a larger swath of precipitation accompanying the disturbance than the WRF does, and also has the precipitation reaching Pennsylvania earlier than the WRF.  The SREF precipitation ensemble members relatively consistently project the precipitation entering western portions of the state by late Wednesday night, as well as some wrap-around precipitation in eastern portions a little later.  We were conservative in the forecasting of precipitation late Wednesday night into Thursday night, though, because of some of model uncertainties and inconsistencies.  We forecasted 'scattered showers' for much of the state and didn't get overly dramatic, as this synoptic event is still almost four days out into the future.  However, we are pretty certain that most portions of the state will at least experience some precipitation from this low pressure system.

-Alicia Klees

Sunday Techincal Discussion

Synopsis:  75% of the Commonwealth is under cloud coverage from Low pressure system in Northern New England at the moment of this writing.  Clouds will begin to fade, leading to a wonderful start to the work week as sunshine reigns until Wednesday afternoon.  A cold front pushes through the region Wednesday night setting up for a cooler Thursday and Lake Effect showers.

Short-term:  Clouds will be progressing across the state during the day on Sunday as GFS & NAM are In agreement.  They are also in agreement of the high pressure working building in from the North in Canada for Monday which sets us up for an excellent week of sunshine.

Long-term: The models remain in agreement because of the lack of "weather" until Wednesday might when a cold front from a low in Canada moves into the region.  GFS shows Lake effect showers and clouds for Thursday, and hence the forecast for western PA includes this.  Otherwise sunshine prevails.

10/29 Technical Discussion

Synopsis:

The forecast period appears to be a quiet one, with a very little chance of precipitation today. After that, the main story will be the temperatures returning to seasonable values as compared with the past week. Things don't get really interesting until the end of the next work week, when the GFS shows the potential for an interesting storm.

Short-term:

Mostly sunny skies look to be the rule for our forecast period, except for today with clouds and the possibility of showers due to the last of the low pressure system that has been in the area for a few days. Models have shifted the clipper system mentioned by the previous forecasting shift even further north, meaning that we forecasted only the chance of cloudiness on Sunday for the Commonwealth as a whole and no precipitation.

Long-term:

Winds from the north will keep our temperatures low on Monday. The latest GFS run has moved the coastal low that could have affected us early next week further up the coast. We are not even anticipating significant cloud cover from that system. Our next weathermaker looks to be a system that would dive down from Canada toward the end of next week. Models are currently showing the 540 line for that potential system as far south as the Carolinas. Could this storm be our first chance for frozen precipitation?

Burkely Twiest

Technical Discussion

Synopsis:

A generally quiet pattern is setting up through the weekend with only a couple small systems at most skirting PA.  Temperatures are cooler.  Uncertainty spikes higher at the 5-7 day outlook.

Short-term:

Showers are ongoing in these overnight hours around and south of Erie and Bradford and will likely continue through the day tomorrow.  Showers may continue during the day as far south as Johnstown, but as a forecasting group we weren't convinced.  An Alberta-clipper-like system will likely move to our north across Canada, but showers cannot be ruled out in the northern counties.  The model trend however has been to take this farther and farther north.

Long-term (next work week):

The GFS has a cut-off low far to the south and quite calm conditions in the northeast; the trend has been for the low to cut-off later in the week and to end up farther to the west and south.  The CMC has a small shortwave on Monday, and then a coastal low.  As a group we discussed thoroughly how to forecast this and decided to simply just go with the GFS solution.  We didn't like the messy set-up for the coastal low, with 3 or 4 different short waves getting all mixed together.  To forecast for a change of rain (or rain/snow in the mnts.) would be equally valid meteorologically, but would be the result of a different interpretation of the risk and uncertainty.

Scott Sieron

21Z Discussion - 10/28

Synopsis...

The "Upper Midwest Superstorm" and its associated cold front are pulling away from Pennsylvania this afternoon as winds pick up and temperatures fall gradually from west to east. A completely different air mass will cause much cooler conditions for the next few days. Scattered rain and snow showers are possible near the lakes, but otherwise, conditions should remain mostly dry over the weekend.

 

Short Term…

Current observations show temperatures have steadily dropped about 20 degrees behind the cold front in western PA, where wind gusts are approaching 30 mph. This pattern will overtake the entire state by tonight, and guidance shows the region will be under the influence of a cool northwesterly flow throughout the forecast period. Scattered showers (mixing with snow in the coolest areas) will continue through Friday morning in the NW with the cool flow over the lakes. Elsewhere, skies will remain partly to mostly cloudy. Wind gusts over 30 mph are possible throughout the state overnight.

 

Long Term…

PA will be under the control of a strong upper-level circulation for the weekend, with lobes of energy trying to occasionally pinwheel down. A surface ridge tries to build in during the day Saturday, raising temperatures back to near average, but another front approaches the region late Sunday. Models disagree a little on the timing and intensity; we went with a mean result with timing in NW and NC. Consensus was that front will be too weak to produce much precip outside these zones, so we kept it dry. Scattered clouds will be the rule throughout the period as cool air remains perched aloft. Latest MOS runs seem to like the calm wind/dry air solution and potentially colder temps Monday night...later shifts may want to monitor this, along with a potential late-week storm.

 

Forecaster: Matt Mahalik

Technical Discussion

Synopsis...

A weak cold front will pass through the state this afternoon and evening, bringing with it a slight chance of showers to western portions of the region.  The only chance of any precipitation after today for the forecast period is in the northwest region where some lake effect rain showers may persist into later Friday afternoon. A few snow flakes may even show up around Bradford tonight.  After today, a westerly flow will persist for the remainder of the forecast period with breezy conditions into Saturday and clear skies into Monday.

Short Term...(today - noon Friday)

Aforementioned weak fropa will cross the western part of the state this afternoon and evening.  The 540-thickness line makes its appearance as far south as the Mason-Dixon line according to NAM and GFS later tonight into early tomorrow morning, thus a chance of snow seems prudent in the northwest mountains overnight with the lake-enhanced precipitation.  After tomorrow morning, skies begin to clear across the state as a high pressure sets up to the southwest of the region.  A fairly tight pressure gradient will create breezy conditions from tonight into tomorrow.

Long Term...(noon Friday - Monday)

Not a whole lot going on in the long term.  A persistent westerly flow and clear skies will create some pretty seasonable conditions for the weekend and early next week.  Looking into the even longer term, the GFS, DGEX, and ECMWF are all hinting at a possible storm system moving up the east coast in the middle part of next week.  Based on the current track and surface temperatures, there will be no shot for snow anywhere near PA but it is something to keep an eye on as far as some potential significant rainfall.

Forecaster: Kyle Imhoff

Forecast Discussion

Synopsis...

A weak cold front will be passing through the state early Tuesday morning and afternoon. A cold air mass will build in behind it, keeping temperatures steady and seasonable through the beginning of next week. Aside from that, the most exciting thing to forecast for is the amount of cloud cover each day, with every day pretty much being somewhere between partly cloudy and mostly clear skies. All in all, a very boring forecast.

Short Term...

The WRF shows a weak cold front moving through the state early Thursday morning. The latest run (0Z) has the front moving much faster during the morning, so it should be clear of the eastern regions by noon. From this, the afternoon temperatures should be about 2 or 3 degrees cooler than originally anticipated. Behind this front, a steady westerly flow will build in, helping to keep temperatures mild and seasonable for this time of year basically through the rest of the forecast period. Vertical stacking of winds will allow for somewhat breezy conditions tomorrow and on into Saturday.

Long Term...

Little changes from the short term forecast... Seasonable temperatures and partly cloudy to mostly clear skies will persist through the end of the weekend and on into Monday. The WRF shows a developing shortwave late Monday night on into Tuesday morning. This may be our next rainmaker. Overall, enjoy the rest of the week and the coming Halloween weekend, because we are in for some Spook-tacular weather!


Andrew Dzambo


We Are... Penn State Meteorology

                                                                                                       Technical Discussion

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Synopsis:

A cold front will completely move out of the state by tonight and an area of high pressure will build in for the weekend.

Short term(Thurs-Fri)

The cold front that brought showers to the area will completely move out of the state by early Thursday. Cooler temperatures and windy conditions will move in behind the front for Thursday and Friday. The NAM shows clouds for Friday before dry air moves in for the weekend. The cold Canadian air will keep temperatures in the 50s and even in the 40s for Thursday and Friday. The GFS shows some lake effect snow for Thursday night into Friday. With temperatures in the 30s, the ridges could see some flurries.

Long term(Sat-Sun)

A ridge of high pressure will build south of the state and temperatures will be in the 50s and some southeast regions will get into the lower 60s. Most of the weekend should be sunny, but some clouds will sneak into the region for Sunday. While temperatures will stay in the 50s.