Phillyweather.net: The Delaware Valley's Weather Center

Thursday, November 26, 2009

Taste of Winter Tomorrow

As countless folks trek out to malls and stores tomorrow, a taste of winter may accompany the aftertaste of leftover turkey and stuffing. The combination of an upper level low over the Great Lakes tracking towards us and its interaction with a coastal low off of the Carolinas will increase winds around here tomorrow, decrease temperatures, and bring about some atmospheric irritation in the form of showers tonight and also tomorrow.

With the upper low moving over the region there is some potential for snow to mix in with those rain showers, especially north of Philadelphia over higher elevations, where temperatures at the surface and aloft will be a bit colder. Accumulations don't seem likely unless you are in the Poconos or in the Central Pennsylvania mountains and accumulations in those areas appear to be on the order of a coating or dusting on grassy surfaces.

Winds will increase tomorrow from the west and northwest, becoming rather gusty in the afternoon with sustained winds around 20 mph and gusts to over 30. Temperatures will drop from today's mid and upper 50's to the 40's tomorrow, with wind chills in the 30's during the day. While not "bitter" it will certainly be a day of bluster with a taste of early December in the atmosphere.

Check out the current wx wall for progress of precipitation, as well as current temperatures, over Thanksgiving and Friday.

Wednesday, November 25, 2009

Going To Be A Dreary Time To Travel

While precipitation around here is modest, the presence of a heaping of low level moisture and low clouds is hindering air travel around the region this afternoon. As you can see below, much of the Mid Atlantic is dealing with high humidity levels (the numbers on the map below). Low level moisture in the form of drizzle, fog, and passing showers is making things quite London-like or Seattle-like outside.

Drier air is back across Ohio and parts of West Virginia (where the hue of green on the above map is not as bright, indicating some drying at the surface), probably around 18-24 hours away from us. While we won't see a ton of clearing tomorrow, I do think traveling on Thanksgiving will be a bit better than it will be this afternoon (especially on the flying side of things). Ground travel will have fog as the biggest impacts around here this afternoon and tonight, with visibilities reduced to under a mile in locations. We should see those visibilities improve tomorrow as the day progresses.

Thanksgiving and Black Friday 2009 Forecast

Thanksgiving is upon us and with it all of the various travels and hustle and bustle of the beginning of the holiday season. The weather will be a small factor in our travels on Wednesday, a greater impact on Friday, but weather should not play a significant role in our Thanksgiving travels around the region as we will be sandwiched between two storm systems.

Tonight: As a weak disturbance tracks to our north some showers will continue into this evening, with drizzle and fog being more likely overnight as low level moisture continues to hang over the region. It'll be a Londonesque night as low temperatures will drop into the mid 40's across much of the region overnight with light and variable winds.

Thanksgiving: Temperatures will be relatively mild and the weather should be relatively dry during the day...hopefully drier than your turkey dinner. Morning fog will lift, leaving a mostly cloudy sky. If we get enough sunshine, we could hit 60 in a few spots but I think we'll see mid and upper 50's with only a few glimmers of afternoon sunshine. Showers may begin to approach late in the day in advance of a change in the weather for the weekend.

Thursday Night: Skies will cloud back over and period or two of light rain will move through overnight as a cold front crosses in association with an upper level low that will move in on Friday. Temperatures will drop off to the low and mid 40's by morning with winds increasing late at night from the west.

Friday: Morning rain will end, with scattered showers possible through the afternoon. To the north and west, some showers may mix with snow as an upper level low works through but little accumulation should be expected (as of this point). It will be blustery with winds increasing to 15-25 mph from the west and northwest. Temperatures will generally be steady through the day, likely bouncing up into the mid and upper 40's for daytime highs. It is quite possible our high temperature on Friday is at midnight.

Weekend Sneak Peek: Breezy conditions will continue into Saturday before winds diminish late in the day as high pressure builds in. Sunday looks like a much nicer day as sunshine builds in and temperatures bounce into the mid 50's. For late November, it's not a bad weekend at all if you can deal with a bit of wind on Saturday!

Coming Thanksgiving: We'll briefly update Friday's weather impacts.

Tuesday, November 24, 2009

2009-2010 Philadelphia Winter Forecasts

Winter forecast time is upon us...for some it is the most wonderful time of the year as snow hopes are rising and wishes for snow days are here. The various local TV outlets are issuing their winter forecasts over the coming days and as always, we'll let you know what the forecasts are and how much snow the local meteorologists are thinking is in the cards for Philadelphia this winter.

CBS 3 (November 16th): Average temperatures in December, with below average temperatures in January and February are in the cards according to Kathy Orr and CBS 3. They are forecasting above average snowfall, 26-33" for the season in Philadelphia. You can check out the video of her forecast here.

NBC 10 (November 18th): Hurricane Schwartz's winter forecast on NBC 10 is calling for a winter that on paper looks like a snowier version of 2006-2007 and 1994-1995, with a warm start and a colder finish. Hurricane is projecting 18-24" of snow for Philadelphia, which is right around average.

6 ABC (November 18th): 6 ABC is going with colder than average (one to three degrees below average for the winter) and snowier than average (30" for Philadelphia, 45" for the Lehigh Valley) in their winter outlook.

Fox 29 (November 24th): Fox 29 is calling for 22.7" of snow this winter. John Bolaris' forecast is averaging the impacts of four different Nino winters (1957-58, 1986-87, 1994-95, and 2006-07 -- all of which produced different results) together to call for a slightly-snowier than average winter in Philadelphia. Unfortunately, John Bolaris did not make a temperature call in his winter outlook.

Blustery Friday & Saturday On The Way

It's been damp the past couple of days and it will continue to be damp for the next few, with some showers and drizzle tomorrow. Thanksgiving may actually turn out to be decent for a time as we will be sandwiched between two systems. The first, a coastal low that is riding along southern stream energy, will track out to sea to our east. However, this southern stream of energy will interact with an upper level low that will be rambling in from the west. The combination of these two features will allow the coastal to intensify on Friday.

As the upper low begins to work through, the surface low will intensify and draw colder air southeast. The intensifying low will also allow for additional precip to break out (see the map below). For a good chunk of the region rain looks to be the precipitation type of preference from Ma Nature; however, with colder air working in aloft and with an upper level low working through snow may mix in or change over completely in areas where precipitation is a bit heavier. The best chances for this would be north and west of Philadelphia, especially over the mountains and hills of Pennsylvania. However, some snow could mix in on Friday even down to Reading, Allentown, or the outer suburbs of Philadelphia depending on precipitation intensity and upper low track.

The GFS is hinting at 1-3" accumulations over the higher terrain in Central and Northern Pennsylvania on Friday and Friday evening, with the NAM holding snow accumulations only to higher terrain in far northern parts of New York and Vermont.

Temperatures will take a bit of a tumble from near 60 on Thursday to the 40's on Friday and Saturday. With gusty northwest winds (intensifying storm) it will feel a good bit cooler as you are out shopping on Friday. The weather aims to improve as we go into Saturday although breezes will continue. Sunday will arguably be the nicest day of the weekend as winds will be light and sunshine will be in control.