Forecast Discussion

Synopsis...

High pressure will remain in control through Friday, keeping temperatures 10-15 degrees above normal.  A shortwave 500mb trough will bring a cold front through the region Friday night and early Saturday, ushering in refreshingly cooler temperatures.  Earl looks to remain off shore but bring some clouds for the early part of the weekend and breezy conditions.

Short Term (through Wednesday)...

Dewpoints will remain in the 60s and 70s today which will create hot and humid conditions throughout the state.  We expect fog in the morning in some locations this week as well.  Persistence looks like the best forecast through Friday with temperatures reaching into the upper 80s and mid 90s.  Nighttime lows will be in the upper 50s and low to mid 60s.  GFS and NAM MOS guidance looks fairly accurate through the week.

Long Term (Thurs-Sat)

Continued hot and humid temperatures on Thurs/Fri with a few more clouds by Friday due to Earl.  A cold front will sweep through the region on Friday night/Saturday.  Although we will see a drop in temperatures behind the front on a brisk northwesterly flow, the precipitation and RH values associated with the FROPA (frontal passage) do not look very impressive.  Therefore, we have kept the state dry on Saturday with the exception of Northwest/North Central.  Orographic lift along with cold air aloft should create sufficient instability for a few showers in these regions.  Saturday's temperatures are the most interesting during the period and should be monitored closely over subsequent shifts.  GFS MOS had Bradford only getting to 57 on Saturday!  In general, it seems like the eastern half of the state will be warmer than the western half of the state where the cold front will have already passed through earlier in the morning on Saturday.  One potential wrinkle however is the proximity of Earl to the coast.  A closer track would promote more clouds in eastern zones and keep temperatures cooler.

-Dan DePodwin

Head of Forecasting Operations

Forecast Discussion

Synopsis....

The next 4 days look to be about the same - very warm temperatures with high pressure aloft keeping the air dry. Any chance of precipitation holds off until at least Saturday.

Short Term...

Expect temperatures across the state to remain in the upper 80s to low 90s through Thursday and Friday. Raw MOS and GFS outputs are consistent with these temperatures, and should be reliable with a very strong ridge in place and a potent dry air pocket between 700mb and 850mb.

Long Term...

Friday should still remain very warm, but temperatures should start to drop off overnight as a front moves through. WRF and GFS are in fairly good agreement that it will pass through at that time. Behind the front are much milder temperatures. MOS predicts drops as much as 15-20 degrees, from the upper 90s as it will have been in the previous days. This front looks to be a relatively short lived event, with dry air and high pressure rebuilding again behind it early on into next week.

Andrew Dzambo


We are... Penn State Meteorology

technical discussion 8-30

Forecast discussion

A strong ridge of high pressure will continue to dominate the state of Pennsylvania up until Thursday, bringing in cloudless skies for the state of Pennsylvania. The MOS 1200 UTC run indicates warm temperatures near 90 degrees for the state until Thursday, with lows staying in the mid to upper 50's. On Friday, the GFS is indicating that a cold front from the west will pass through the Southwestern and Northwestern part of Pennsylvania bringing in rain showers for the day and colder temperatures to occur Friday into Saturday dropping into the mid to lower 70's. In addition on Friday, the GFS model predicts hurricane Earl to hit the coast of New Jersey, which will bring in rain showers to Southeastern and Northeastern Pennsylvania regions. The cold front from the west will make its way out of the state of Pennsylvania by Saturday, pushing hurricane Earl up the eastern coast, allowing mostly cloudy skies to occur throughout the state of Pennsylvania with temperatures in the mid 70's.

Liz Cosgrove

The ridge of high pressure continues to dominate the region through Wednesday, and models still indicate it beginning to break down on Thursday.  Upper-level moisture can be found in the GFS 12z in the eastern parts of the state on Thursday, perhaps outflow from Hurricane Earl.  By Friday morning, the western parts have moistened up (in the GFS 12z) through much of the atmosphere ahead of a cold front. 

As I write, the GFS 0Z is updating and has Earl much closer and the cold front dryer.  Still shows a chance of lingering showers Saturday maybe even into Sunday.

Scott Sieron

Technical Discussion

Synopsis…

All models have the ridge of high pressure remaining stationed over the state through the latter part of this week.  Dry and unseasonably warm conditions will prevail, with mostly sunny to sunny skies every day.

Short term...

The models are consistent with high temperatures in the upper 80s through low 90s across the state for Monday and Tuesday.

Long term...

Both the GFS and the WRF are in agreement that there will be little upper or lower level moisture in the atmosphere during most of the forecasting period.  AVN, NAM, and MRF have slightly inconsistent temperature projections as the week progresses, but that is to be expected.  The possible effects of Hurricane Earl on the region by the end of the week are debatable.  Currently, the models differ in how quickly and how far westward Hurricane Earl will progress up the East Coast.