3:00 PM | *Impressive cold shot coming by the middle of next week and it could be preceded by a significant rain event*
Paul Dorian
12Z GEFS forecast map of 850 temperature anomalies for next Wednesday with well below normal conditions across the Midwest, Deep South and eastern US (blue, purple); courtesy tropicaltidbits.com
Overview
The coldest air so far this season pushed into the Mid-Atlantic region on Monday and this morning brought many areas their first frost of the season. After another chilly night with frost possible in many areas, temperatures will modify as we progress through the week and into the weekend. There are, however, signs for another cold shot in the East and Midwest by the middle of next week and this next one could be even colder than the current outbreak. In addition to the upcoming chill, there are signs that the mid-week cold shot could be preceded by a significant rain event in the eastern US.
12Z GEFS forecast map of 500 height anomalies for next Wednesday with well below normal conditions across the Midwest, Deep South and eastern US (blue, purple); courtesy tropicaltidbits.com
Discussion
Strong high pressure has settled into the eastern US and it will stay relatively stationary over the next several days. As a result, it should stay generally rain-free in the DC-to-Philly-to-NYC corridor through the upcoming weekend with chilly temperatures tonight and tomorrow, but then rather comfortable for the rest of the week. By early next week, attention will turn to a strong cold front that should be dropping southeastward across the Upper Midwest early in the week.
As this cold front approaches the eastern states, moisture may feed into the frontal boundary zone from the southern states and the result could be a significant rain event around Tuesday of next week for the Mid-Atlantic region. Once the front passes, colder air is likely to pour into the Mid-Atlantic region around Wednesday of next week and it could very well be the coldest air of the season so far. The mid-week cold shot is likely to result in the first “lake-effect” type snow shower activity across the Great Lakes and interior Northeast US and could reach as close by as the higher elevations of West Virginia, western Virginia/Maryland and upstate Pennsylvania. It looks like the mid-week cold shot will be part of a rapidly changing weather pattern in which air masses will be quick to come and go. By late next week, the chill is likely to give way to a warm up which may then be quickly followed by another cold shot. The notion of a cold air outbreaks later next week and weekend in the eastern US is supported by the most recent computer model forecasts of the Arctic and North Atlantic Oscillation indices. These indices are forecasted to drop sharply into negative territory next week and this often signals just such an outbreak of cold air for the Midwest and eastern US.
12Z Euro forecast map for next Tuesday afternoon with heavy rainfall amounts in the eastern US ahead of a charging cold front: courtesy WSI, Inc.
The latest run of the GFS ensembles features a deep trough of low pressure in the Midwest and eastern US by the middle of next week and corresponding 850 mb temperature anomalies that are well below normal. The 12Z Euro forecast map for Tuesday afternoon features an area of very high precipitation amounts that lie just ahead of the southeastward charging cold front.
Meteorologist Paul Dorian
Vencore, Inc.
vencoreweather.com