WINTER WEATHER BRIEF…ISSUED DEC. 13, 2017…3:25 P.M. EST

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(T. F. “Storm” Walsh III)

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Good day everyone!

Most of the U.S. will see minimum temperatures of freezing to below freezing over the next few days.  Analysis of the global models indicates minimum temperatures should begin to modify in about 5 days (120 hours) and day 6 (144 hours), with a decent warm up for the Florida Peninsula.  During the next 48 hours, Florida will be experiencing milder minimum temperatures.  By day 5, minimum temperatures should be in the 50’s-60’s in the deep south.  Temperatures will fluctuate by days 7 – 10 with cooler min. temps reaching further south by day 7, and retreat somewhat by day 10.

GFS 120 AND 144 HOUR MINIMUM TEMPERATURES FORECAST

ECMWF MINIMUM TEMPERATURES 120-144 HOURS


Albeit in the longer range, based on my analysis of the global models another Arctic blast appears to be on tap, at around days 13-14 in the forecast period.  This again will be attributed to stratospheric warming at 50-30 mb, with an increase in 50-30 mb pressure anomalies.  This indicates another negative phase of the Arctic Oscillation (AO).  This is shown to begin occurring around 23 Dec.  Based on the current forecast minimum temperatures by the GFS at days 13, the negative AO should reach its max. around 26-28 Dec.

GFS 50 MB PRESSURE AND TEMPERATURE ANOMALIES


ARCTIC OSCILLATION FORECAST

This phenomenon pretty much goes hand in hand with the PNA (Pacific/North American Pattern) going into a positive phase, which indicates lower pressure anomalies over the eastern U.S.,  indicating troughing.  Both models show the PNA going negative, which coincides with the milder temperatures that are forecast.

PNA FORECAST

The following link is a good article on the PNA:
https://climate.ncsu.edu/climate/patterns/PNA.html

The GFS is indicating a coastal storm along the NE coast around day 7, with the ECMWF indicating the low to be further east and earlier in the forecast, but still affecting the eastern portion of the U.S.  This may bring Lake Effect snow to portions of the Great Lakes region, and New England.  I cannot rule out the slight possibility of blizzard conditions SE of the Great Lakes, over western portions of NY state, and PA.

GFS

ECMWF

The following are projected snowfall accumulation amounts for days 5 and 7 from the GFS and the ECMWF.

GFS

ECMWF


The following are the forecast dominant precipitation types for days 5 and 7 from the GFS.

GFS PRECIPITATION TYPE

For local NWS for your area, please click on the following map, then click on your area when the warnings map pops up.

NWS WARNING AND HAZARDS DISPLAY

INTELLICAST 24 HOUR FROST/FREEZE OUTLOOK (LINKED)

As a reminder, during cold and frigid spells, bring your pets indoors, and take care of your plants.

I should be able to issue another update regarding the Arctic air forecast near month’s end, next week around this same time.

Have a blessed day!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
CoCoRAHS OBSERVER

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