{ "number": 808, "headline": "December 5, 2025 Friday Evening Weather", "standfirst": "Huge cold pool forms in western Canada and Alaska with ridging across Western US", "desk": "winter", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2025-12-06", "published": "2025-12-06T01:14:43.449000Z", "updated": null, "access": "free", "body_html": "
\"\"

This is post number 806 \u2026 evening update [just maps + headlines] to keep the ball rolling into the wild winter ahead | Author: Dr. Ryan Maue (X @RyanMaue X @weathertrader)

\"\"

Moisture plume with subtropical jet continues across the Southern U.S. but really only keeping Florida warm this weekend

Temperature Anomaly | Next 15-days

\"\"

Flagship European model ensemble solution for temperature anomaly next 15-days shows the cold pool formation and intensification over Alaska and Western Canada \u2014 a more typical Polar Vortex dump with strong surface high pressure blasting southward along and east of the Rockies into the central U.S. in the 2-week time frame \u2014> remnants of our recent/ongoing stratospheric warming event \u2014> and then another one in the coming 10-12 days!

Note, there are fast moving disturbances or short-waves riding along the polar front from the Gulf of Alaska through the Pacific Northwest and then in the Midwest and Great Lakes. These features are spaced out in time \u2014 so the ensemble mean blends or smooths out 51 solutions that ALL have cold blasts but intermixed with warm periods. The end result is a rather smoothed continuous blob of cold connecting Alaska with the Northeast U.S.

This STILL has potential for VERY cold Arctic blast outbreaks! Example from ECMWF Control (12z)

Massive ridge across the western U.S. \u2014> surface high pressure over central U.S. and a dip in the jet stream w/mid-level trough (associated with tropospheric polar vortex) bringing a chunk of the Alaska/Western Canada cold pool into the Midwest/Great Lakes and then Northeast.

HRRR 18z | Next 48-Hours into Sunday Early Afternoon

\"\"

Precipitation Type | Weather Next 6-days | ECMWF 18z

\"\"

Boatloads of moisture coming into the Pacific Northwest with 2 major atmospheric river events in next 6-days \u2026 and Alberta Clippers pick up whatever makes it through the Rockies to take into the Midwest and Great Lakes with weak storm system snow events \u2014 eventually these start adding up!

Headlines Friday Evening

  1. Still not seeing any strong systems across the Eastern U.S. but quick moving \u201ccutter\u201d or Clipper Systems could provide wintry precipitation especially with the cold air in place \u2014> typical with negative AO/negative NAO with help from the Pacific moisture smashing into Northwest

  2. Massive ridging across the Western U.S. will completely block any systems from pushing through the central Rockies \u2014 instead everything must go up and over including potential shortwave disturbances that will grab lobes of the polar vortex to bring brief but intense cold shots through the northern tier.

Please share \u2014 spread the word about my publication here in Substack! This post is public so feel free to share it.

Share

Weather Trader is an entirely subscriber-supported publication [sweat equity] from Dr. Ryan Maue. To receive all new posts, consider becoming a free or paid subscriber, and please LIKE and SHARE posts. Coupon codes at end of post (if you need them)

ECMWF 18z Precipitable Water Next 6-days | My favorite parameter

\"\"

Atmospheric river systems into the Pacific Northwest \u2014 narrow at first, and then quite a wide swath by next Tues/Wed \u2014 see how shortwave disturbances along the polar front (polar vortex edge) pick up the moisture = Alberta clipper systems

White colored precipitable water = absence of moisture = cold/polar air mass

Get 7 day free trial

Temperature Analysis | 7:45 PM ET

\"\"

Temperature Anomaly | 7:45 PM ET

\"\"

Lower 48 Temperature Anomaly was -2.5\u00b0F below normal

NWS Precipitation Next 72-hours

\"\"

NWS Snowfall Next 72-hours

\"\"

Blend of Models | 10 Days Precipitation Total (includes liq from snow)

\"\"
\"\"

Enormous precipitation totals in the Cascades \u2026 upwards of 20\u201d of QPF or more would translate into outrageous snowfall totals

Give a gift subscription

Blend of Models | Total Snowfall Next 10-Days

\"\"

Saturday Morning Low Temperatures

\"\"

172 million below freezing (Lower 48 average low is 27.6\u00b0F)

Saturday High Temperatures

\"\"

Still 14 million at/above 80\u00b0F in Florida! 36 million don\u2019t get above freezing!

Sunday Morning Low Temperatures

\"\"

176 million below freezing (Lower 48 average low is 26.9\u00b0F)

Sunday High Temperatures

\"\"

The same 14 million at/above 80\u00b0F in Florida! 49 million don\u2019t get above freezing!

AI-GFS 18z | 500 mb Temperatures | Polar Vortex Watch Next 10-days

\"\"

Fancy new tool from NOAA (AI-GFS) shows the reorientation of the tropospheric polar vortex to ditch the cold pool over Hudson Bay \u2014 and instead dip/focus across Western Canada

ECMWF AIFS-Single 18z | Height Anomaly (500 hPa) Next 10-days

\"\"

Enormous ridge formation across the Western U.S. \u2014> will it build eastward and block off the Siberian / Arctic express? AIFS-Single seems to have a strong ridge bias, but we\u2019ll check back tomorrow.

Integrated Vapor Transport Next 10-days | North America

\"\"

Parameter used for monitoring \u201catmospheric rivers\u201d usually along the U.S. west coast, but the idea works well for many other areas \u2014 highlighting midlatitude storm systems with warm conveyor belts (moisture plumes)

ECMWF 18z | Snowfall | Next 6-days

\"\"

ECMWF EPS 12z | Ensemble Median Snowfall Next 15-days

\"\"

Instead of just the median \u2014 let\u2019s look at the 90th Percentile \u2014 if the model ensemble was operating in the 1 in 10 worst snowfall category \u2026 most places it\u2019s not a major difference BUT it can be \u2014> ECMWF EPS 12z | Ensemble 90th Percentile Snowfall Next 15-days

\"\"

The difference between the 75th and 25th Percentiles is the interquartile range (IQ) and shows the ensemble spread to a good approximation! Even when we show the median snowfall amounts, there is a +/- range of sometimes a similar magnitude of the median/mean \u2026 and that\u2019s why ensemble means of precipitation into the medium range can be misleading during storm events where 100 miles makes the difference between yes/no snowfall/rain \u2014 the average is not really a solution

\"\"

ECMWF EPS 12z | Ensemble Snowfall Probability > 1\u201d | Next 15-days

\"\"

We\u2019ll be monitoring the 1\u201d chance of snowfall for a \u201cWhite Christmas\u201d in the coming weeks. This map is through late December 20th.

ECMWF EPS 12z | Ensemble Snowfall Probability > 6\u201d | Next 15-days

\"\"

6-inches is sufficient for a \u201cbig storm\u201d and Lake Effect machine diagnostic but 12\u201d is even better \u2014>

ECMWF EPS 12z | Ensemble Snowfall Probability > 12\u201d | Next 15-days

\"\"

Next 15-days Temperature Anomaly | Ensemble Mean to December 19

\"\"

The western ridge is STRONG \u2026 and should provide enough Pacific moisture and moderating mild air to temper the longevity and intensity of any Arctic blasts that sink from the massive cold pool over Western Canada.

Temperature Anomaly | Next 15-days | ECMWF EPS 12z

5-Day Chunk #1 | Temperature Anomaly | Dec 5 - Dec 9

\"\"

5-Day Chunk #2 | Temperature Anomaly | Dec 10 - Dec 14

\"\"

5-Day Chunk #3 | Temperature Anomaly | Dec 15 - Dec 19

\"\"

Share Weather Trader

Maps sourced from weathermodels.com designed and innovated by yours truly! Please subscribe there for real-time access to the newest maps, charts from all of the weather models including ECMWF and AIFS, NOAA AI-GFS/AI-GEFS

Active coupon codes:

Group subscription discount > 2 memberships (25% off)

Get 25% off a group subscription

Upgrade to yearly membership (25% off)

Give a gift subscription

", "body_key": null, "teaser_html": "

Moisture plume with subtropical jet continues across the Southern U.S. but really only keeping Florida warm this weekend

Flagship European model ensemble solution for temperature anomaly next 15-days shows the cold pool formation and intensification over Alaska and Western Canada \u2014 a more typical Polar Vortex dump with strong surface high pressure blasting southward along and east of the Rockies into the central U.S. in the 2-week time frame \u2014> remnants of our recent/ongoing stratospheric warming event \u2014> and then another one in the coming 10-12 days!

", "claims": [], "assets": [], "provenance": { "built_at": "2026-09-10T14:46:14Z", "model": null, "cycle": null, "stores": [ "https://weather.substack.com/p/december-5-2025-friday-evening-weather" ], "mint_sha256": null, "pairing_rule": null, "detector": null, "detector_version": null, "inputs": { "substack_post_id": "180849035.december-5-2025-friday-evening-weather", "audience": "everyone", "type": "newsletter", "imported_from": "substack export" } }, "strength": 0.0, "tags": [ "archive", "everyone" ], "supersedes": null, "superseded_by": null, "source": "substack", "canonical": "https://weather.substack.com/p/december-5-2025-friday-evening-weather", "slug": "december-5-2025-friday-evening-weather", "path": "/mp/808/", "url": "https://forecastpost.com/mp/808/", "desk_label": "Winter", "digest": "78b049d53af64372b71f032995852ef33d05e36400889a2ebbea5171c8c3f00d" }