JANUARY 2025 IS PROVING TO END UP A COLDER THAN NORMAL MONTH AS NEGATIVE DEPARTURES GROW!

The switch from unseasonably warm month in November (and resulting fall) to a mixed cold and mild December to a colder than on average first half of January. The worst is yet to come as us meteorologists look at the waves of Arctic cold projected possibly into the end of the month. This jives well with the Stratospheric moderation-warming at 30-10mb mentioned here days ago.

While cold looks more & more likely with brief moderations between, no clear-cut storm system has been ginned-up by models with any certainly. More light snow is expected this weekend as temperatures moderate to the lower 30s (a veritable heat-wave) before plummeting back down into the deep bone-chilling, wind-chilling cold later in the weekend into next week! Later in the month into early February is beginning to look interesting but as for the next couple of weeks…

 

This was written Tue afternoon /14th/ by extended forecasters in Maryland and still looks good…

 

Prognostic Discussions

Valid: Jan 20 - 24, 2025 (6-10 Day Outlook)

Valid: Jan 22 - 28, 2025 (8-14 Day Outlook)

Issued: Jan 14, 2025

 

Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks

NWS Climate Prediction Center College Park, MD

300 PM EST Tue January 14 2025

 

6-10 DAY OUTLOOK FOR JAN 20 - 24 2025

A highly amplified 500-hPa height pattern is forecast across the forecast domain during the 6-10 day period, with ridging over western North America and strong troughing downstream east of the Rockies. The 0z ECENS and CMCE are quicker to lift the troughing out in the East by day-10 while the 0z GEFS maintains stronger negative height anomalies. The manual height blend indicates above-normal heights west of the Rockies and extending northward through Alaska. A +210 meter positive height anomaly center is noted just to the west of British Columbia. Below normal heights are predicted for most of the CONUS east of the Rockies, with the strongest negative anomalies (-150 meters) to the north of the Great Lakes.

 

A major Arctic air outbreak is forecast to be ongoing across the central and eastern CONUS at the start of the period. The 0z ECENS and GEFS indicate widespread daily temperature anomalies exceeding -20 deg F on days 6 and 7,corresponding with subzero temperatures across the Northern and Central Plains, Midwest, and possibly into the Interior Northeast, and minimum temperatures in the 20s deg F possibly reaching the Gulf of Mexico coast. The re-forecast and uncalibrated tools all support elevated probabilities for below-normal temperatures across nearly all of the CONUS, with the highest chances (greater than 80 percent) across the Southern Plains and much of the East. Probabilities for below-normal temperatures are reduced across the Northern Plains due to the possibility of quickly moderating temperatures as the trough lifts out, with the ECENS depicting a flip to above-normal temperatures at the end of the period.

 

Below is the CFS run (1/13/12Z) from the same period starting at Wed 1/15/25 @ 48hs. Surges of Arctic air backed by large, High Pressures /blue H's/ stacked up across the North Pole into northern Canada sliding SE from the far north

 

 

Next we'll look at which analogues actually accurately projected the first half of the winter's trend /Dec-Jan/ and what happened then - and what is more likely to occur for the winter period Feb-Mar '2025.

Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian

 

 

With The First Week of a New Year Comes a Change in the Weather

The first official month of the Winter 2024-25 season brought a notable change in the prevailing unseasonably warm fall weather. For the most part; the month of December contained equal amounts of below normal temperatures and above until the end; when a quick mild spell boosted the monthly average to above normal at 33.3/+2.0. All in all; December was a fairly "snowless"  month with below average snowfall at 3.6" /normal  8.9"/ through the 31st but with above normal precipitation with 3.27". Thus far; only half our normal amount of snow has fallen this winter with 5.4" /Norm -10.8"/

The outlook for January 2025 keeps the declining temperature trend in vogue for now with a predominantly colder than normal January in store for the early - mid month period. Latest indications are a gradual stratospheric warming trend (not official SSW) far aloft over Siberia toward the North Pole will help elongate the Polar Vortex (and some of the brutal cold at the surface) and push it south (blue/purple) into the mid latitudes, including North America with some moderation. Coldest air at the surface would concentrate over the eastern two-thirds of the nation and deep into the south!

 

Projected 500 MB upper air pattern for all of January shows the elongated trough over eastern Canada into the eastern U.S.

 

With the ridging/upper high pressure building over the eastern Pacific and western U.S at times and blocking in Greenland, this will enable the delivery of Polar/Arctic air south into the U.S.

Low pressure will move along the Polar front early in the new week but at this time it appears much of the snow will stay south in the Ohio Valley. Models have had a terrible time with this system varying from a snowstorm for the southern Great Lakes to nothing, keeping it south. The dynamics and upper air pattern won't be sampled better until Friday. Any significant changes will be blogged.

Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian