Saturday, January 14, 2012

Forecast for Sunday, January 15, 2012

A secondary cold front will push more Arctic Air southward into Philadelphia tonight. This secondary front will be accompanied by snow flurries and isolated snow showers which could dust a few areas (a few tenths of snow). Mostly Cloudy skies will clear eventually toward daybreak. Despite the breezy conditions and increasing cloudiness, forecasted lows get down into the single digits at Mount Pocono to lower twenties in the city. Wind chill factors will be in the single digits and lower teens this evening, colder in the higher terrain.

Sunday looks to be influenced by high pressure in the area and thus I am forecasting mostly sunny skies. A stray flurry in the Poconos cannot be ruled out. It will be a bitterly cold day with breezy, northerly winds and temperatures struggling to make it into the thirties. Bundle up!

Monday starts off mostly clear, but clouds will overspread the region. By Monday Night, a warm front is on our doorstep. Model guidance continues to indicate a surge of warm air aloft, limiting the chance for snow for just about everywhere except the Poconos and perhaps higher terrain of the Lehigh Valley. This system is currently scheduled to arrive on the heels of daytime heating. Daytime heating may push temperatures above freezing at the surface for most places which eliminates the potential for freezing rain when it begins to precipitate; but this isn’t in stone and there is chance that despite the heating, it won’t push temperatures high enough. It also has to be considered that should this system be delayed some, some early evening breaks in the clouds could allow temperatures to fall back below freezing.

With this said, I believe there is an opportunity for a period of rain, mixed with sleet for a good portion of the area. North and West of Philadelphia, it may start out as mainly sleet and gradually transition to rain…and if the surface is below freezing in spots…there could be a period of freezing rain.

Model guidance will have a better handle of the placement of the high pressure area and the extent of the Arctic air across area after the frontal boundary moves through tonight. It is possible that later model runs may turn out colder at the surface and develop cold air damming…which would increase the chance for icing.

I am expecting high temperatures to push greater than 50 degrees along the coastal plain inside the warm sector on Tuesday. Rain may turn showery once the warm front moves northward. This front may hang up in the far northwestern counties and Mount Pocono may deal with freezing rain in the early morning and temperatures barely making it above freezing for several hours.

A cold front pushes through on Tuesday Evening and Night. Again, there could be some gusty winds ahead of it and a squall line of showers, heavy at times with embedded thunderstorms. It will turn windy on Wednesday with a possible snow flurry in the Poconos.

A weak little system may clip us Thursday Night into Friday Morning with a round of snow showers. It doesn’t appear this will be significant, but it may dust or coat the ground. The best chances of this happening are in the northern areas.

There have been some indications of a mild stretch developing in the long range. There have been times where temperatures have spiked to 70 degrees, followed by snowstorms, slizzards, and ice storms.