Thursday 9 a.m.
A major snowstorm is crossing the Plains today. The storm has been quite strong, and there were more than 8,000 lightning strikes between 5 a.m. and 9 a.m. Central Time from Texas to Missouri. As the jet stream structure changes between now and tomorrow, the storm should weaken and cause less precipitation than previously. Some freezing rain may affect the upper Ohio Valley tomorrow with some snow moving across the middle of Pennsylvania (with rain/sleet south and light snow to the north) tomorrow afternoon. Spotty snow and rain can affect Philadelphia and NYC tomorrow night. During the day Saturday, moisture from the South Atlantic states should stream up along the coast and the storm system may strengthen off the Middle Atlantic. This growing storm should cause rain in Philadelphia and New York City on Saturday, then transition into what could be a major snow storm from Providence or Boston on north. This video shows how all of this could transpire.
One other feature for today is an upper-air trough swinging south then southeast through New England. That system may sponsor scattered snow showers later this afternoon from Connecticut to Massachusetts.
Often, computer models are in disagreement about storm locations and effects three to four days or more in advance. However, last night's runs from the JMA (Japanese Meteorological Agency model), the ECMWF (European Model) and GFS (National Weather Service Global Forecast System) all showed the Sunday storm for New England in pretty much the same place. This storm could bring 6 -12 inches of snow from near Providence and Boston on past Portland. However, agreement is not equal to accuracy.
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...