Wintry cold to hit the Northeast late this week
1. A storm that brought half a foot of wet snow on Chicago caused a snow-rain mix in New York City and enough snow to instigate morning commute accidents in Providence and Boston. It was the first accumulation of the season in those cities, and some people need a refresher on proper winter weather driving techniques. (I have heard, however, that 80% of us think we are above-average drivers.) This map shows the weather systems affecting the nation at 8 a.m. ET.
2. A large area of rain from the western Gulf states will advance northeastward to reach the Middle Atlantic states then southern New England tomorrow afternoon and night. From about the middle of Pennsylvania on northward, there could be an accumulation of wet snow, and some of the higher terrain could get 6 inches. The low pressure area supporting this precipitation is in turn related to a trough aloft coming out of the Rio Grande Valley. (I said related to, but in reality the trough aloft and the storm at the surface are both parts of the same weather feature.) This map shows the 500 MB flow as of 7 a.m. ET.
On this map, "a" is the trough that supported the now-leaving storm and "b" is supporting the rain in western Gulf states. It is being ejected northeastward by the action of trough "c."
3. Another trough that will be in the Pacific Northwest tomorrow will approach the East Coast on Thursday. Its associated cold front will usher the coldest air so far this season into the Great Lakes then the Northeast at the end of the week. Widespread snow flurries and squalls will develop downwind from the Great Lakes into the Appalachians. This is what the surface map should look like Friday morning with cold wintry winds affecting the northeast quarter of the country:
