{ "number": 440, "headline": "November 21, 2024 Thursday Winter Weather Update", "standfirst": "Much colder air on the way into December", "desk": "winter", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2024-11-22", "published": "2024-11-22T00:56:07.897000Z", "updated": null, "access": "free", "body_html": "
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Thursday Headlines

  1. Thursday \u2014 Friday: 2 ongoing storms on each coast: (a) atmospheric river w/yet another bomb cyclone in California/Oregon/Washington (b) Mid-Atlantic and Northeast low pressure looping with significant snowfall.

  2. We are flipping to full-tilt winter = much colder conditions across the Lower 48 with significant snowfall threats. I am watching various ensemble and A.I. models to determine how cold it could get in early December.

Thursday Evening Across the Lower 48

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Ongoing storm has lowered temperatures dynamically into the 20s and lower-30s across the eastern Great Lakes and Ohio Valley. You can see the cold pool in the anomaly map \u2014 plenty cold enough for snowfall.

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HRRR over next 18-hours into early afternoon on Friday shows heavy snowfall continuing to wrap around the center of low pressure just west of New York City.

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Day 10 Upper Level Pattern

Main question is how much Arctic air can dump onto the Lower 48 east of the Rockies to spur heating demand. LNG markets are betting on the outcome of various forecasts over the next few days.

ECMWF AIFS 12z

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EPS Ensemble Mean 12z

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Comparing the AIFS and ensemble mean just with a quick eyeball glance suggests that sure, the AIFS could be a member of the ensemble mean, just washed out or smoothed.

Looking at the ECMWF HRES 12z, similar story as AIFS with more highly detailed trough. That\u2019s typical of looking at the ensemble means vs. the individual members or a deterministic forecast.

The ensemble mean is averaging 51 similar forecasts at Day 10 but small deviations in time and space reduce the amplitude of the upper-level wave pattern and therefore reduce / spread out the lowest geopotential height centers.

ECMWF 12z HRES

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Finally as an independent option, we can look at the GFS 12z deterministic and see a similar pattern. That should indicate agreement in the general \u201ccold shot\u201d thesis.

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Turns out that 5-day skill is insanely high right now. That doesn\u2019t mean that Day 7 or 10 is also high, but it could \u2014 more on that later.

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ECMWF HRES 12z at 0.98 is outrageous, some of the best forecasts ever produced.

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ECMWF 18z | 48-Hour Precipitation Type

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Bomb cyclone #2 is looping its way into the Pacific Northwest offshore Washington with continued \u201catmospheric river\u201d flood of moisture on shore, eventually extending southward into Central California, and even SoCal.

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Not a bomb cyclone, but plenty of moisture with a low that drops into the mid-980s doing a counter-clockwise track loop around New York City.

In another few weeks, the cold air in place north of the system in Canada would be blockbuster snowfall amounts for all of New England. Is this a sign of what\u2019s to come this winter?

Precipitation Totals From NWS | Next 60-hours

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Snowfall from NWS next 30-hours

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Low Temperatures on Friday

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High Temperatures on Friday

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Snowfall Forecasts

ECMWF 12z | 10-day Ensemble Median Snowfall

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NOAA Blend of Models 7-day Snowfall Accumulation

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Quick peek at the Blend of Models showing the \u201censemble\u201d smoothing.

Total Precipitation next 3-7-Days | NOAA WPC

Next 72-hours

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Day 4 | Monday November 25

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Day 5 | Tuesday November 26

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Day 6 | Wednesday November 27

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Day 7 | Thursday November 28 | Thanksgiving

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EPS | 5-day Temperature Anomaly

Days 1-5: November 21 - November 25

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Days 6-10: November 26 - November 30

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Days 11-15: December 1 - December 5

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Maps sourced from weathermodels.com designed and innovated by yours truly! I actually create all of my content from scratch.

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

Thursday Headlines

Thursday \u2014 Friday: 2 ongoing storms on each coast: (a) atmospheric river w/yet another bomb cyclone in California/Oregon/Washington (b) Mid-Atlantic and Northeast low pressure looping with significant snowfall.

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