Synopsis:

A low pressure system will make its way NE along the Eastern Seaboard over the next 36 hours. The event will bring significant snow accumulation to southeast Pennsylvania, the Mid-Atlantic States, and the Tri-State area before making through southern New England on Thursday afternoon. After the system exits on Thursday afternoon, another disturbance will make its way through the Commonwealth on Friday and lasting into Saturday. Moderate to heavy snowfall can be expected across the state.

 

Short Term (Through Thursday Afternoon):

The low pressure system can be expected to affect Pennsylvania between Wednesday (0z) and Thursday (700z). Warm air advection can be expected prior to the arrival of the storm. This will allow for temperatures in the southeastern and south central areas of the state to rise slightly above 0®C for a short period of time. This will bring in the possibility of a wintry mix ahead of the warm front. However the temperature will quickly drop below zero. Moderate snowfall can be expected across the state. Heavier snowfall amounts are expected in the southeast and southwest sectors. We chose to utilize the WRF model due to its accuracy over the past season. The conditions at t=0 were similar to the current conditions throughout the state as well. The HRRR and WRF simulated radars were also utilized to gain a better perspective on the amount and location of precipitation. The center of the system will take a more northeastern vector path than had been previously predicted. This will carry the bulk of the precipitation through Pennsylvania, which is contrary to model predictions late last week. The storm will make its way off the US coast come Thursday afternoon, leaving significant snowfall and breezy winds.

 

Long Term (Thursday Afternoon to Sunday)

Although it goes against the hopes of most Pennsylvanians, more snow lies in the long term forecast. After the passing of the low pressure system on Thursday morning, it appears that two additional (but smaller) disturbances will pass through the state before the weekend is over. The first disturbance will move into the state on Friday morning, bringing mostly light snowfall with it. Behind the disturbance, a brief period of lake effect snow can be expected in the Northwest sector. The next disturbance will
"clip" through the Commonwealth on Saturday, exiting Sunday morning. It will bring light snowfall to most of the state, but areas of moderate snowfall can be expected in the Northwestern and North central areas of the state. Cold air advection and a wind from the Northwest following the disturbance will bring isolated lake effect snow showers to the Laurel Highlands and the Northwest sector. The WRF and GFS models were used in combination for this forecast. The WRF has provided very accurate precipitation predictions, but is often too overzealous when forecasting for larger, weaker systems.

Forecaster: Tom Bedard