Friday Morning Technical Discussion

Synopsis:

A major winter storm should affect New England later Friday, but before it does so expect some wintry precipitation across Pennsylvania. High pressure moves in for the weekend providing some drier conditions and some warmer temperatures for the second half of the weekend. Another system moves through Sunday night behind a warm front, but cold air damming will cause the precipitation to start as a wintry mix for many areas.

 

Short Term (Fri-Sat):

A clipper system moving through the Ohio Valley and a storm along the coast will phase Friday to provide a major winter storm across New England. Earlier predictions were that Pennsylvania would receive a moderate snowfall with heavy accumulations likely in northeast Pennsylvania. These predictions look to bust now as the storms are taking longer to phase than models had shown. Some light wintry precipitation was falling in southeast Pennsylvania Friday morning. This precipitation should end around midday as the coastal storm lifts NE. Precipitation will then fill in from the west as the clipper moves through Pennsylvania and begins to phase with the coastal system. As of Friday morning, rain was falling across southwest Pennsylvania where warm air advection was present south of the low pressure center. The line of precipitation will move east providing a several hour period of precipitation across the state. Most areas should see snow from it, with the exception being southwest Pennsylvania. As the clipper reaches eastern portions of the state later today, it will phase with the coastal storm. As the phasing occurs and the storm stalls and turns back towards the New England coast, some extra wrap around snow is possible in eastern Pennsylvania. Expecting all snow to end Saturday morning with only a leftover snow shower or two possible in northeast Pennsylvania. Snowfall accumulations of 1-3" are expected across central Pennsylvania, 3-6" across eastern Pennsylvania, and 3-6" in northwest Pennsylvania as there will be some lake enhancement for northwest Pennsylvania. Some gusty winds are possible overnight Friday as the coastal storm wraps around some northwest winds. High pressure will move in behind this system bringing a northwest flow to the state and keeping temperatures slightly below normal on Saturday.

 

Long Range (Sunday-Monday):

High pressure should slide east of the state on Sunday, bringing a southwesterly flow to the state and warmer temperatures in the mid to upper 30's. The pleasant weather will be short lived as a storm system will move up through the Great Lakes Sunday night. Precipitation will fall as rain across southwest Pennsylvania, but as it reaches central Pennsylvania expect freezing rain and sleet as the warm air will advect up over the mountains. The wintry mix will be possible early Monday across the eastern half of the state before warmer air erodes the cold air and a changeover to rain occurs. Up to .1" of ice is likely across eastern Pennsylvania with .1"-.25" possible across central Pennsylvania. The rain showers will end Monday evening followed by a return to northwesterly flow. The flow will be weak so do not expect very strong cold air advection into Tuesday.