Synopsis: The state of Pennsylvania has seen two different stories as far as the weather goes today. Eastern Pennsylvania saw an easterly flow at lower levels near the surface last night which brought their dewpoints up and created a thick layer of fog up to about 950mb. This fog had a difficult time burning of during the day as a continued easterly flow brought more moist air. For this reason, many places across eastern Pennsylvania stayed foggy all day leading to temperatures only in the upper 50's to lower 60's in some places. The western half of Pennsylvania was able to stay mainly clear today with a southerly wind and so they got their temperatures well into the upper 70's and some in the lower 80's. As we move towards the weekend the easterly flow will continue to lead to showers and cloudiness across eastern Pennsylvania while a cold front approaches from the west. As the cold front does so, Hurricane Sandy will phase with the cold front and make landfall somewhere in the Mid-Atlantic or Northeast early next week.
Short Term: (Friday – Saturday) As we look at the forecast it will be broken down into two parts. The first is eastern Pennsylvania which will again see moist easterly flow off the Atlantic Friday. This will cause yet another round of fog and keep temperatures down some. As the day goes on and the high pressure moves off the coast, the winds at the surface will start turning more southerly which will help to eat away the fog as warmer air is advected. Winds aloft will turn more easterly however, so we will see the fog burn off some but mid-level clouds will take its place. The moist air aloft may even help to create a few showers across eastern Pennsylvania Friday. As Saturday approached across eastern Pennsylvania, clouds from Hurricane Sandy will begin wrapping in as Sandy is a large Hurricane around 2000 miles wide. There may be a few showers from these wrap around clouds Saturday but it will be cloudy for the most part. Western Pennsylvania will see some more sunny skies on Friday and temperatures again in the mid 70's. Some clouds may move in during the afternoon from the approaching cold front which will stop western Pennsylvania from getting as warm as they were on Thursday. As Saturday approaches, western portions of the state will see clouds on the increase with some showers possible early as the cold front pushes through the state. The showers should last for most of the day, and cooler weather will accompany them leading to temperatures in the mid 50's. Portions of central Pennsylvania will see a mix of the two extremes with some fog possible early Friday which will burn off allowing for temperatures in the 60. Clouds will increase during the day on Saturday as the cold front approaches. Showers will begin in central Pennsylvania in the late afternoon and continue overnight.
Long term: (Sunday – Monday) At this point the forecast gets somewhat difficult as there is great spread in the models still. The European model has Sandy phasing with the cold front on Sunday and bringing rain and wind to Pennsylvania as early as Sunday. If this were to happen, eastern portions of Pennsylvania should expect periods of rain Sunday which will become heavier on Monday. Winds will also pick up in these areas as we head towards Monday with some areas likely seeing gusts between 50-70 mph. Heavy rain is also likely with areas possible seeing 1-3in of rain by Monday. Western portions of the commonwealth would see scattered showers with more steady periods of rain moving in Monday. As Sandy makes landfall in this case, the storm would wrap around colder air to western Pennsylvania and so some mountains have a chance of mixing with some snow by Monday. If the GFS were correct, the cold front would stall over Pennsylvania and Sandy would not phase with the cold front until late Monday into Tuesday. This would lead to scattered showers across the state Sunday and Monday. Since the NWS required balloons launched every across the United States every 6 hours starting 18z Thursday, the model runs from here on will likely have a better handle on what will actually occur.
Zachary Fasnacht
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