Tuesday, 11:55 a.m.
The first storm of the week is long gone. Colder air has bled southward into northern Virginia, but its progress has come to a halt. The storm developing in the southern Plains is already sending a lot of high-level moisture across the Ohio and Tennessee valleys into the mid-Atlantic states, and precipitation has been rapidly expanding across the central Plains to the mid-Mississippi Valley. A look at satellite-radar composite as of 11 a.m.:
There is no downstream blocking over the Atlantic, so this storm will do its best to cut toward the Great Lakes, and it will have modest success. The surface low center won't make it all the way to Lake Erie in the end, but the low aloft will get awfully close. Look at the 12z Feb. 4 NAM 850mb forecast of heights and temperatures for tomorrow morning:
The warmth aloft will follow the low center aloft. In fact, if you were to more closely examine the thermal structure of the atmosphere tonight into tomorrow morning, the warmest level will actually be higher up than the 850mb level, and it will be plenty warm enough to change snow to sleet deep into the heart of Pennsylvania as well as across southern New England. This will limit snow accumulations across the southern half of Pennsylvania, the lower Hudson Valley and much of Connecticut, Rhode Island and southeastern Massachusetts, perhaps all the way up to the Mass Pike.
Therefore, the heaviest snow will likely be in the northern tier of Pennsylvania and the southern tier of New York over to much of Massachusetts, southern Vermont, southern New Hampshire and coastal Maine, where a solid 6-12 inches will accumulate, with locally 15 inches.
Once this storm is gone, cold air will dominate the middle of the country the rest of the week, and we'll begin to brace for storm three, due sometime this weekend. More on that storm tomorrow.
A building upper-level ridge of high pressure in the West will promote hot, dry weather in the Northwest, while a downstream trough brings cooling through the Midwest into the Great Lakes and Ohio Valley.
A pattern more typical of late July and early August is shaping up around the country, one with heat and humidity, but with fewer incidents of severe thunderstorms and flooding.
There will be plenty of heat and humidity from the southern Plains to the East Coast this week while much cooler air prevails for a time over the Northwest to the northern Plains.
Severe thunderstorms raked across the Midwest and Ohio Valley in the past 24 hours, with more on the way this afternoon. The pattern will repeat itself over the next week.