12:20 PM | **Cold pattern continues for much of the US with the next impressive Arctic blast arriving late in the week in the Mid-Atlantic/NE US and another one early next week**

12Z GFS forecast maps of 500 mb height anomalies show strong ridging from Alaska to the west coasts of Canada and the US both late this week (left) and early next week (right). This type of upper-level air flow will allow for the transport of these next couple of Arctic air masses from northern Canada into the central and eastern US. Maps courtesy NOAA, tropicaltidbits.com

Overview

November has started off much colder-than-normal across the nation and there won’t be any let up for the eastern 2/3rds of the nation into at least the middle part of the month. The cold start to the month follows a colder-than-normal October across the CONUS with more than twelve-hundred sites experiencing the lowest temperature ever in the month of October and, even-more impressive, many locations set their monthly record for the month as a whole.  Multiple cold air outbreaks will ride along the polar jet stream during the next couple of weeks from the northern part of Canada to the Mid-Atlantic/NE US with the first one arriving in the Thursday night/Friday time frame and another next Monday.  The late week cold blast will also feature rain-changing-to-snow in parts of the interior Mid-Atlantic and NE US and several inches can accumulate from western New York State to upstate Maine. 

The nation as a whole was colder-than-normal during the month of October (left) and has started well below-normal in November (right). Maps courtesy Weather Bell Analytics, NOAA

Recap of the October cold

A few of the standout new monthly lows (data courtesy of NOAA, “electroverse.net”):

·         Eureka, NV‘s reading of 2°F on October 30 broke the previous monthly record of 3°F set back 1971, and is now the town’s lowest-ever October temperature in 131 years of data.

·         McDermitt, NV set a new cold-record in books dating back 127 years — last month’s -10°F busted the previous record October-low of -6°F set in 2002.

·         Lamar, CO‘s Halloween low of 1°F is now the coldest October temperature since records began some 126 years ago, smashing 1991’s previous record of 8°F.

·         Haskell, TX surpassed its previous monthly low from way back in 1917 — the 18°F observed on the 31st is now the city’s lowest-October temperature in the record books dating back to 1893.

In terms of monthly temperature records, a few of the noteworthy highlights included Spokane, WA which suffered its coldest October-ever in the record books dating back to 1881. The National Weather Service data confirms the average temperature of 42.3°F observed last month broke the city’s all-time record of 42.8°F set way back in October 1905 (the Centennial Minimum). Also worth nothing is that three out of four of Spokane’s coldest Octobers ever (in 138 years of records) have occurred this century — including 2002 and 2009. Another example included Rapid City, SD — the NWS reports that the average temp of 38.1°F registered at Rapid City Airport was the coldest-ever for the month of October in books going back 100+ years, beating out the old record of 38.7°F from 2009. 

Finally, the coldest temperature ever recorded in the continental US during the month of October was likely set in Peter Sinks, Utah.  Peter Sinks is a natural sinkhole in the northern part of Utah at an elevation of around 8000 feet and is known for its highly localized effects.  Nonetheless, the unofficial overnight low temperature there of -43.6°F on 30 October was pretty amazing. Nearby Salt Lake City, Utah provided some supporting evidence of the extreme cold on that day as it set a low temperature record of 14°F for 30 October and records there go all the way back to 1874.

These “backward trajectory” plots display movement of air parcels from way up in Canada to Atlanta, Georgia (left) and New York City (right) for the late week Arctic blast. Maps courtesy NOAA

Late week cold blast

A significant cold air outbreak is headed to the Mid-Atlantic/NE US from the northern part of Canada at the end of the work week. As high pressure ridging intensifies across Alaska and western Canada, the upper-level air flow will develop in a manner which allows for the transport of air from way up in Canada to the central and eastern US.  In fact, forecast maps of “backward-trajectories” ending on Saturday morning depict air movement from northern Canada into places like New York City and even into the Southeast US. 

As the cold air pushes to the southeast late this week, moisture will push northeast along the advancing frontal boundary zone.  This should result in a rain-changing-to-snow scenario in much of the interior Mid-Atlantic and NE US with several inches of accumulating snow possible from western NY to upstate Maine by Friday morning.  In addition, the Great Lakes “snow machine” will get turned on late in the week as the unusually cold air crosses over the still relatively warm waters causing instability in the lower part of the atmosphere and snow squalls for downstream locations. While there can be some snow shower activity in the DC-to-Philly-to-NYC corridor before the precipitation ends late Thursday night or early Friday morning, the bigger story in these areas will be the cold blast.

The colder-than-normal pattern continues for the eastern 2/3rds of the nation through mid-month with average 850 mb temperature anomalies for days 6-10 (left) and days 11-15 (right). Maps courtesy NOAA, tropicaltidbits.com

Cold blast early next week

All signs point to another cold air outbreak for the central and eastern US early next week and this too can feature snow in interior sections of the Mid-Atlantic/NE US and Great Lakes as the cold air arrives.  Much like the late week cold air outbreak, this next air mass will drop southeastward across Canada and then push through the Great Lakes to the eastern seaboard.  Once the cold air is established, we’ll have to watch for a possible wave of energy to rotate through the upper-level trough which could result in snowfall for the Mid-Atlantic/NE US by the middle of next week. Looking even farther ahead, it appears this colder-than-normal weather pattern that began in the eastern US on the very first day of the month may very well continue for much of the remainder of November.

Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com

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