{ "number": 802, "headline": "December 1, 2025 Monday Winter Weather", "standfirst": "Meteorological winter starts quite cold across the eastern U.S. with an Arctic blast", "desk": "winter", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2025-12-01", "published": "2025-12-01T23:44:47.921000Z", "updated": null, "access": "free", "body_html": "
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Welcome to new and current subscribers and visitors! I am very appreciative for your continuing support heading into this crazy winter. This is post number 801 to start meteorological winter.

Author: Dr. Ryan Maue (X @RyanMaue X @weathertrader)

Yet another Sudden Warming event in the stratosphere (SSW #2)

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This will be a major story in the coming days as the magnitude of the second SSW event comes closer into view.

Why Do SSWs Happen? (with help from Grok)

The polar vortex in winter is normally a strong, cold, cyclonic circulation isolated from the troposphere. Currently distorted / split:

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10 mb Winds

SSW events are triggered from from below

SSWs are triggered when huge planetary-scale Rossby waves (wavenumber 1 or 2) generated in the troposphere (from mountains, land\u2013sea contrasts, and strong jet streams) propagate upward into the stratosphere and break there, just like ocean waves breaking on a beach. When these waves break:

Think of it as the troposphere \u201cpunching\u201d the stratosphere so hard that the entire polar vortex collapses or splits.

The signal can lag for weeks \u2026 we don\u2019t see too many major SSW events \u2014and now we\u2019ll have two in a month!

The stratosphere and troposphere are normally only weakly coupled in winter, but a major SSW creates a strong downward-propagating signal that reaches the surface in \u22481\u20133 weeks and can persist for 4\u20138 weeks (sometimes longer).

  1. Days 0\u20137 after central date: Polar vortex weakens/splits/displaces in the stratosphere.

  2. Days 7\u201320: The negative Northern Annular Mode (NAM) or Arctic Oscillation (AO) signal propagates downward through the stratosphere.

  3. Lag \u2248 2\u20136 weeks: At the surface \u2192 negative AO/NAO pattern dominates:

Okay, now we have two of these SSW events \u2014 perhaps different flavors or magnitude of stretch/split \u2014 but the end result could be compounding with stronger negative AO and NAO patterns = cold air \u201cdumps\u201d out of the Arctic into the middle latitudes with a weaker jet stream.

Hard to bet against continued colder than normal across Lower 48 for the rest of December \u2014> into January with effects of both SSW events lingering into the New Year.

Next 15-days Temperature Anomaly | Ensemble Mean

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The coldest air in the 15-day mean is centered over the Great Lakes including Chicago, Detroit, and into New England \u2014 enhanced with snow cover/depth remaining for the next 1-2 weeks.

Headlines Monday Evening

  1. Nor\u2019easter does develop but far enough inland with warm air to spare the immediate I-95 corridor from obliteration (instead rain and some mixture)

  2. Evergreen analysis: Next 2-weeks remain stuck with well-below normal temperatures across the Eastern U.S. as the mega-load of \u201cPolar Vortex\u201d cold pool wobbles around Hudson/James Bay waiting for any shortwave out of the Pacific to capture a lobe.

  3. Sudden Stratospheric Warming event #2

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Temperature Analysis | 5:15 PM ET

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Subzero air in Montana with teens and lower 20s into Minneapolis. Near freezing in Chicago and Detroit

Temperature Anomaly | 5:15 PM ET

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Lower 48 Temperature Anomaly was -5.9\u00b0F below normal

HRRR 18z | Simulated Radar Next 48-hours into Wednesday Afternoon

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Total Snowfall From HRRR Next 48-hours | 18z \u2014> Wed 1 PM ET

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Like taking a paint brush and coloring the canvas with beautiful hues of blue and pink, my favorite maps (aside from precipitable water)

Lower 48 | Weather into Tuesday Morning

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NWS Precipitation Next 72-hours

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Heavy rainfall along the Gulf coast from Houston to New Orleans \u2026 maybe 1-2\u201d into Atlanta, as well, then up the Eastern Seaboard. Lots of moisture with this system.

NWS Snowfall Next 72-hours

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Boston escapes the major snow storm \u2014> right on the edge of major accumulations.

RRFS-A through 84-hours (Friday 1 AM ET) | Snowfall totals

These maps are beautiful \u2026 RRFS-A is a 3-km resolution model and my color table is dazzling, but it would be even better as part of a \u201cblack\u201d mapping scheme with more transparency and \u201cheads up display\u201d features.

Blend of Models | 7 Days Precipitation Total (includes liquid from snow)

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Total Snowfall Next 7-Days

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Tuesday Morning Low Temperatures

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187 million below freezing (Lower 48 average low is 24.6\u00b0F)

Tuesday High Temperatures + Anomaly from Climatology

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Wednesday Low Temperatures

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211 million below freezing (Lower 48 average low is 24.1\u00b0F)

Thursday Low Temperatures

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194 million below freezing (Lower 48 average low is 21.0\u00b0F)

Friday Low Temperatures

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195 million below freezing (Lower 48 average low is 23.5\u00b0F)

NWS NDFD | Chicago just dipped to -1\u00b0F for Friday morning (Dec 5)

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

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ECMWF EPS 12z | 15-day Ensemble Mean Temperature Anomaly

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Alaska goes into the deep freeze \u2014 but also the Great Lakes, too

ECMWF AIFS 12z | Height Anomaly (500 hPa) Next 10-days

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More central U.S. ridging from AIFS (12z) but that seems like an outlier with too much Pacific influence compared to other models (full physics ensembles)

Integrated Vapor Transport Next 10-days

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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 12z | Snowfall | Next 7-days

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ECMWF EPS 12z | Ensemble Median Snowfall Next 14-days

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ECMWF EPS 12z | Ensemble Snowfall Probability > 1\u201d | Next 10-days

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We\u2019ll be monitoring the 1\u201d chance of snowfall for a \u201cWhite Christmas\u201d in the coming weeks.

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Need to look at the snowfall margin again in the Southeast \u2014 thankfully only 2% chance in Atlanta for next 14-days, but this is an impressive cold pattern + snow for early December.

ECMWF EPS 12z | Ensemble Snowfall Probability > 6\u201d | Next 14-days

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6-inches is sufficient for a \u201cbig storm\u201d and Lake Effect machine diagnostic

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

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

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5-Day Chunk #2 | Temperature Anomaly | Dec 6 - Dec 10

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5-Day Chunk #3 | Temperature Anomaly | Dec 11 - Dec 15

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Snowfall Analysis | October 2025 - today

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Snowfall Analysis | Last 7-days

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This will be a major story in the coming days as the magnitude of the second SSW event comes closer into view.

The polar vortex in winter is normally a strong, cold, cyclonic circulation isolated from the troposphere. Currently distorted / split:

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