12:30 PM | **Storm threats loom for next week with the biggest potential impact at mid-week**

“High-latitude blocking” is likely to setup by the middle of next week at the same time waves of energy will cross the central part of the US and move into the eastern states. Strong high pressure is likely to build into the southeastern part of Canada and it’ll act as a cold air source during these potential multiple storm events. Map courtesy NOAA, tropicaltidbits.com

Overview

The interesting and active weather pattern of recent weeks will continue into at least the middle of the month with multiple storm threats on the table for next week in the central and eastern US. The first storm threat for the Mid-Atlantic/Northeast US will come during the early part of next week and perhaps the bigger threat comes at mid-week. The weather turns milder over the next few days in much of the eastern half of the nation, but a colder air mass is likely to arrive in the northeastern quadrant during the early part of next week following the late weekend passage of a cold front. Teleconnection indices such as the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) are supporting the idea of “high-latitude blocking” to get established by the middle of next week which, in turn, supports the idea for high pressure to build across southeastern Canada.  At this same time, two separate waves of energy are likely to cross the southern states and move northeastward towards the eastern seaboard. With a cold air source building to the north across southeastern part of Canada, this type of pattern could result in accumulating snow in at least part of the Mid-Atlantic/Northeast US.

Teleconnection indices known as Arctic Oscillation (AO, top) and North Atlantic Oscillation (NAO, bottom) are in “negative” territory and are forecasted to remain there next week which often is correlated with “high-latitude blocking” and cold air outbreaks into the central and eastern US. Plots courtesy NOAA

Details

High pressure will shift off the east coast over the next 24 hours and milder air will push northeastward into the Mid-Atlantic/Northeast US as we head into the upcoming weekend.  In fact, temperatures should rise well into the 50’s this weekend in much of the I-95 corridor from Philly-to-Boston and could surpass the 60 degree mark for highs in the DC metro region.  As a cold front slowly pushes to the east this weekend from the Midwest, there can be some rain shower activity in the Northeast US/Mid-Atlantic, but very likely not a significant rain event.  In fact, this weekend’s cold frontal passage will be rather uneventful; however, it may set off an important chain of events potentially leading to a cold and snowy middle of next week in at least parts of the interior Mid-Atlantic/Northeast US.

There will be a storm threat early next week for the Mid-Atlantic/Northeast US, but a bigger threat may come at mid-week….stay tuned. Map courtesy NOAA, tropicaltidbits.com

Behind the late weekend cold frontal passage, colder air will begin to filter into the Mid-Atlantic/Northeast US early next week as cold high pressure builds into southeastern Canada.  This type of atmospheric pattern in which high pressure builds across southeastern Canada is supported by the expectation that the AO and NAO teleconnection indices will be in “negative” territory.  This high pressure system to the north may very well become an important cold air source for the Mid-Atlantic/Northeast US; especially, by the middle of next week.

Strong, cold high pressure will be well-established across SE Canada by the middle of next week. Map courtesy NOAA, tropicaltidbits.com

At the same time the high pressure builds across SE Canada, two separate waves of upper-level energy will push across the southern states and then they’ll likely take a turn to the northeast and heads towards the eastern seaboard. The first system may stay just to the south of the Mid-Atlantic/Northeast US as it perhaps ends up near the Carolina coastline on Monday. This will be a close call and there is plenty of time for the early week threat to push to the north in coming days. Following on its heels, another system is likely to cross the southern states and head towards the eastern seaboard by the middle of next week. This system will be able to gather plenty of moisture from the Atlantic Ocean and Gulf of Mexico as it approaches the eastern seaboard.  With the cold air source possibly well-established by this time across southeastern Canada, this potential mid-week setup could result in accumulating snow for parts of the Mid-Atlantic/Northeast US. 

The middle of next week could feature strong high pressure across southeastern Canada and a strong storm system near the east coast. Map courtesy NOAA, tropicaltidbits.com

One final note, “climatology” suggests that it is quite difficult to get accumulating snow in the immediate I-95 corridor region and points to the coast in the middle of December with still relatively-warm sea surface temperatures in the western Atlantic. However, it is certainly way too early to dismiss that possibility; especially, with the potential of “high-latitude blocking” to the north.

Stay tuned…certainly an interesting weather pattern as we head to the middle part of the month.

Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com

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