Enormous Rainfall Totals for the West Coast — 20”+ of precipitation

HRRR 00z | Next 48-Hours through Thursday 7 PM ET

Simulated Radar —> Pacific Northwest storm system —> Great Lakes over next 2-days

Wind Gusts —> hurricane force — upwards of 80-100 mph maximum gusts as powerful low pressure systems move eastward through Southern Canada

Storm System Parade Across Canada | Next 6-days | MSLP

Sequence of 3 powerful storm systems measured by central pressure in the 970s in an unlikely location over land in southern Canada. These mobile cycles quickly track east over the next 6-days … each time providing a “clash of air masses” between warmer Pacific origin air to the south and the Alaska/Canadian cold pool to the north.

Next 6-days | 850 mb Winds

Lower atmosphere level winds show plenty of energy with these storm systems sweeping across the Midwest, Great Lakes, and Northeast into next weekend. Thankfully, much warmer across the Lower 48 so we’re NOT looking at a trio of crippling blizzards.

Next 6-days | Jet Stream Winds at 250 mb

Very strong jet stream across the Western U.S. providing huge baroclinic energy resource for the mid-latitude storms + wind energy to power the near-surface gusts especially in the Rockies and then Plains.

Maximum Wind Gusts from NWS Next 72-hours —> Holy Moly!

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

Headlines Tuesday Evening

1. Significant warming trend into next week for Christmas but we need to deal with the Canadian cold pool that gets pulled into the Midwest and Great Lakes behind these powerful storm systems tracking through Southern Canada.

2. Powerful storm systems with pressure in the 970s mb track from the Pacific through British Columbia into the Prairie provinces. Very gusty winds!

3. One of these storms intensifies in Quebec to 950s mb and will usher in a polar vortex lobe and colder air behind it on Friday.

4. And, another quick blast of cold air from that replenished Western Canada “cold pool” for the Midwest and Great Lakes this weekend.

5. Christmas looks quite warm for almost the entire Lower 48 relative to normal for December 25th.

Next 6-days Temperature Anomaly

Pattern looks more like early March than mid-December with these strong storm systems … thankfully not looking at severe weather. Instead, we’ll see windy and wet conditions in the Great Lakes and Northeast, but unlikely to see much in the way of snow accumulations in the Lower 48. Canada will be further buried in snow.

High Temperatures Next 8-days | Until Thursday Dec 25th

The temperature pattern sees some “amplification” with the brief cold snaps on Friday and Sunday … but the cold retracts northward as strong, warm zonal flow dominates the Lower 48 with a strong/honking ridge.

Christmas Day Temperatures | Morning Lows

104 million below freezing for low temperatures — but that’s still not too bad for December 25th.

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Christmas Day Temperatures | Daily Highs

Almost 75 million at/above 70°F on Christmas Day! Only 8% of the Lower 48 by area will be freezing on Christmas Day — according to Blend of Models (v4.3)

ECMWF 18z 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.

• Parade of “atmospheric rivers” continue for the West Coast — and sink a bit further south across Oregon into even Central California by next weekend with major impacts likely. HUGE atmospheric river into California this weekend.

• “Arctic blast” scheduled for Friday — not as a severe — and brief as the warmer westerly flow from the Pacific wins the battle with the parade of southern Canada storm systems.

ECMWF 12z 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 by Christmas — BUT the Northeast could see normal or colder air, especially with proximity to the “Polar Vortex” and any lobes that may be dragged south by passing storm systems.

The Alaska / Western Canada cold pool replenishes strongly into the New Year, but the Lower 48 blocking ridge remains firmly in charge — at least for now!

RTMA | Current Temperature Analysis | 9:30 PM ET

Average Lower 48 temperature was 42°F with about 82 million below freezing.

Temperature Anomaly | 9:30 PM ET

Lower 48 Temperature Anomaly was 7.4°F ABOVE normal

Wednesday Low Temperatures

160 million below freezing but not seeing any subzero readings.

Wednesday High Temperatures

54 million at least 70°F

NWS Precipitation Next 72-hours

NWS Snowfall Next 72-hours

Blend of Models | 10 Days Precipitation Total

Massive amount of rain into California over the next 10-days

Enormous rainfall totals across the Pacific Northwest continue

Blend of Models | Total Snowfall Next 10-Days

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

One more “polar vortex” trough into this weekend … and then the ridge builds across the Rocky Mountains and forms a long-lasting block. However, we’re seeing little disturbances riding the crest of the ridge and dipping through the Great Lakes in to the Northeast as part of the giant pinwheeling Polar Vortex anchored over Hudson Bay.

The ridge will break down eventually — and might need a strong digging trough over the West Coast coming out of the Gulf of Alaska to do it into the New Year.

ECMWF 12z | 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 18z | Snowfall | Next 6-days

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

Probability of 1-inch or more Snowfall in the next 15-days

Probability of 6-inches or more Snowfall in the next 15-days

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

5-Day Chunk #1 | Temperature Anomaly | Dec 17 - Dec 21

5-Day Chunk #2 | Temperature Anomaly | Dec 22 - Dec 26

5-Day Chunk #3 | Temperature Anomaly | Dec 27 - Dec 31

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