Wednesday 8 a.m.
A major storm is likely to develop just off the Middle Atlantic coast on Friday then track northeastward. Most of the computer models show that development, but the details are different. For example, the GFS shows mild air sweeping westward from the Atlantic to hold temperatures above freezing in New York Friday when most of the precipitation is falling. There would be some snow as cold air floods in at the end of the storm. That model also suggests a heavy, wet snow or a snow/rain mix from Providence to Boston. The ECMWF (the European model) looks colder and suggests a mix of rain and snow in NYC changing to snow with more than a foot on Friday night. For Boston, that model suggests an all-out blizzard with 2 feet of snow! This video shows the GFS solution from its 1 a.m. EST run. That does not mean I favor that solution but rather offer a platform for discussing the possibilities.
Here is our preliminary snow accumulation map for the Friday/Friday night storm:
Yesterday, there was a sharp boundary between air that was cool and dry enough to suppress thunderstorms and air that was warm and humid enough to support them. This map shows the lightning strikes from 8 a.m. ET yesterday to (almost) the same time today.
As the second low pressure area develops off the East coast, it will work in concert with a high pressure area from Canada to orchestrate cooler-than-usual conditions with showers in the Middle and North Atlantic states Thursday.
Looking ahead to <strong>next</strong> weekend, the Mothers Day Weekend, we see quite a difference between the GFS model and European models on where cold Canadian air is heading at 2 a.m. Sunday.
Rain is spreading across the Middle Atlantic states today. Dampness will linger from southern New York state to Virginia tomorrow even as the main rain area moves offshore.
For the rest of the week and this weekend, the upper-air "steering winds" will be arranged in two separate streams. The northern branch will send air from central Canada toward New England.
In the Northeast today, the low pressure area shown on this map will move to the East Coast today, pulling the front south as a cold front. Showers and gusty thunderstorm will affect areas south of the front while steady rain and gray skies are common to the north...