White Christmas & The 12 Model Runs of Christmas

Probablility of a White Christmas in Casper & Lander

A Christmas is defined as being white if at least one inch of snow is on the ground at 5 AM that morning. Since official records began in 1948, Christmas has been white 22 times in Casper and 39 times in Lander. Thus, the probability of a white Christmas is 37% in Casper and 66% in Lander.

Casper's Whitest Christmases (Snow Depth):

18" 1982
5" 2009, 1987, 1983
4" 1967

Lander's Whitest Christmases (Snow Depth):

15" 1985
13" 2007, 1979
11" 1983
10" 1992

The probability of receiving an inch or more of snow is much less on Christmas. Since official records began in 1948. One or more inches of snow has fallen 4 times in Casper and 3 times in Lander. Thus, the probability of receiving an inch or more of snow on Christmas is 7% in Casper and 5% in Lander.

 Casper's Snowiest Christmases (Snowfall):

5.6" 1988
2.2" 2009, 1973
1.4" 2007

Lander's Snowiest Christmases (Snowfall):

5.5" 2007
3.1" 1988
1.5" 2003


12 Model Runs of Christmas

Interested in what models are predicting for Christmas morning? For the next few days leading up until Christmas this page will be updated with the latest 12 UTC (5 AM) graphics from the GFS model. NOTE: These are raw model graphics and do NOT reflect the official forecast from the National Weather Service.

This will also show how models can change from run to run, and why forecasting out several days can be extremely challenging!

GFS Model Run at 5:00 AM on: Upper level Flow
5:00 AM Christmas Morning

Surface Pressure & Precipitation
5:00 AM Christmas Morning

December 13th

(288 hr forecast)

Ridge along the west coast. Cold northwest flow across Wyoming with mostly dry conditions.

December 14th

(264 hr forecast)

Ridge across the Pacific Northwest, with a cut-off low over southern California. Weak northwest flow across Wyoming, with mostly dry conditions.

December 15th

(240 hr forecast)

Ridge across the Rockies, with a trough off the coast of North America. High pressure dominates across Wyoming, with dry and weak west northwest flow.

December 16th

(216 hr forecast)

Ridge along the Pacific Coast into the Canadian Rockies, as a closed low moves over the Four Corners.

December 17th

(192 hr forecast)

Ridge over the Pacific Northwest into the Yukon Territory, with a cut-off low over Baja California.

December 18th

(168 hr forecast)

Ridge over the Pacific Northwest, as cold Canadian high pressure settles over the state.

December 19th

(144 hr forecast)

Ridge over the Great Basin and Northern Rockies, as a storm system moves onshore in British Columbia. Cold high pressure remains centered over the Central Rockies.

December 20th

(120 hr forecast)

Ridge over the Northern Rockies, as a storm system moves onshore in Bristish Columbia. A cut off low will spin over northern Mexico.

December 21st

(96 hr forecast)

Models have begun to come into agreement on the forecast for this weekend. With a ridge over the area and relatively mild temperatures aloft. Much of the region could be under strong inversions, keeping colder temperatures at the surface.

December 22nd

(72 hr forecast)

Differences from run to run have decreased significantly and agree that a ridge of high pressure will be in place across the state Christmas morning. Lows will likely be in the single digits and teens. With highs warming into the upper 20's and 30's across the state in the afternoon.

December 23rd

(48 hr forecast)

A ridge of high pressure will be in place across the region Christmas morning, keeping conditions dry and mostly clear except for maybe a few areas of fog. Lows that morning will be in the single digits and teens. Winds will increase along the eastern mountain slopes and across the wind corridor from Rock Springs to Casper in the afternoon.

December 24th

(24 hr forecast)

A ridge of high pressure will be in place across Wyoming Christmas morning, keeping conditions dry and mostly clear, except in some valley and basin locations where fog may hang around in the morning. Winds will increase during the day and help scour out the inversions in a few areas. This will lead to a wide array of temperatures from the upper 20's to the low 40's across the state.



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