Precipitation Type | Weather Next 6-days | ECMWF 06z

Headlines Friday Morning

1. Strong low pressure in the 950s mb still intensifying over Quebec will move into the Atlantic by Sunday, but rain/snow will finish up today across the Northeast

2. A weaker Clipper system will follow through the Midwest and Great Lakes this weekend.

3. West Coast US: A complex of storm systems within an upper-level cut-off trough (from a lobe of the Polar Vortex) = multiple atmospheric rivers & powerful low pressure surface cyclones over next week

4. Christmas looks very warm for almost the entire Lower 48 relative to normal for December 25th. This is great for travelers and the economy (much less heating)

West Coast Atmospheric Rivers | Precipitable Water Next 6-days

Atmospheric river with firehose of moisture streams in West Coast from north to south through Monday — then a powerful cyclone (surface low pressure) forms along the boundary w/assistance from the “polar vortex” lobe dropping southward … the clash of air masses = series of storm systems can landfall California —> enormous rainfall totals at lower elevations and heavy snow in the mountains

Precipitation Type and Intensity | Next 6-days

Precipitation through 10-days is Insane | Blend of Models

10” to 15” along the coast including the Monterey Bay to San Francisco Bay areas — and 20”+ in the Sierra —> this is LIQUID equivalent so anything that falls as snowfall will = roughly 10x that as frozen precipitation.

Today’s Weather | Frontal Boundaries

Northeast Storm System Today

Pacific Northwest Storm System Today

Coast to Coast Extreme Wind Gusts from Storms — actually centered in Southern Canada but Jet Stream is to the south through the Lower 48

NWS Maximum Wind Gusts Next 3-days

HRRR 06z | Next 48-Hours Sim Radar through Sunday 1 AM ET

RRFS-A Total Precipitation Through 84-hours —> Monday 2 PM ET

Northern and Central California precipitation through early Monday — just getting started with the deluge

NWS Precipitation Next 72-hours

NWS Snowfall Next 72-hours

RTMA | Current Temperature Analysis | 8:00 AM ET

Average Lower 48 temperature was 34.4°F with 87 million below freezing.

Temperature Anomaly | 8:00 AM ET

Lower 48 Temperature Anomaly was a 5.1°F ABOVE normal

Friday High Temperatures

51 million below freezing in the Great Lakes vs. 54 million at least 70°F with 80s in Florida and Arizona and Southern California

Saturday Morning Low Temperatures

More than 175 million below freezing

Christmas Day Temperatures | Morning Lows

Only 64 million below freezing for low temperatures

Christmas Day Temperatures | Daily Highs

Almost 104 million now at/above 70°F on Christmas Day!

ECMWF 06z Precipitable Water Next 6-days | My favorite parameter

• White/gray/black colored precipitable water = absence of moisture = cold/polar air masses rotate through the Midwest and Great Lakes around the “still potent” polar vortex anchored over Canada through this weekend.

• Parade of “atmospheric rivers” continue for the West Coast — and sink a bit further south across Oregon then into Northern California by the weekend with major impacts likely. Then, surface cyclones form along the AR boundary and organize even more moisture to landfall California.

850 mb Winds Next 6-days | Powerful Storm Systems

ECMWF 06z | Next 6-days Temperature Anomaly

Chunks of the Western Canada cold pool break off with the passing storm systems — and sweep eastward to be replaced much warmer air from the south into early next week for a very warm Christmas across much of the Lower 48 — but not Alaska.

ECMWF 00z EPS | Temperature Anomaly | Next 15-days

The Lower 48 settles into a MUCH ABOVE NORMAL temperature pattern — eventually — once we can finally block off the “polar vortex” by the weekend.

Temperatures surge to well above normal for much/all of the Lower 48 by Christmas but Alaska goes into the VERY deep freeze

Blend of Models | 10 Days Precipitation Total

Even more enormous rainfall totals across the Pacific Northwest continue into California

Blend of Models | Total Snowfall Next 10-Days

ECMWF AIFS-Single 06z | Height Anomaly (500 hPa) Next 10-days

ECMWF AIFS-Single 06z | Temperature (500 hPa) Next 10-days

Polar Vortex (tropospheric) monitor —> the pink = coldest at 500 mb and we see the arrival of some cold air from Siberia over the pole into the New Year to reinforce the PV over Alaska and Canadian Arctic.

ECMWF 00z | Integrated Vapor Transport Next 10-days

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

ECMWF 06z | Snowfall | Next 6-days

ECMWF EPS 00z | Ensemble Median Snowfall Next 10-days

Probability of 1-inch or more Snowfall in the next 10-days

Probability of 6-inches or more Snowfall in the next 10-days

Temperature Anomaly | Next 15-days | ECMWF EPS 00z

5-Day Chunk #1 | Temperature Anomaly | Dec 19 - Dec 23

5-Day Chunk #2 | Temperature Anomaly | Dec 24 - Dec 28

5-Day Chunk #3 | Temperature Anomaly | Dec 29 - Jan 2

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