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Forecast Discussion:
Winds roared up in the 70 mph range in the mountain passes Wednesday as clouds of dust kicked up on the Plains. It was chilly and wild. Today we turn calm again and tomorrow (Friday) we approach record high temperatures along I-25. The surface map (Figure 1) shows high pressure in place again as our 'Saturday' storm comes ashore in the Pacific northwest.
The first couple of days on Figure 2 and Figure 3 shows how utterly dry and abnormally warm we'll get (we don't even go below freezing Thursday night!). That storm arrives Saturday with most model runs giving us a chance of precipitation with temperatures at or just below freezing. We should see a coating of snow Saturday AM (the red trough in Figure 4). More below...
The longer range forecast:
Even if the official definition of a White Christmas seems to be 1" of snow on the ground Christmas morning - I grew up in Phoenix, AZ - if there is something frozen and white in the shadow of a bush on Christmas morning, I'll be happy. With Sunday and Monday highs climbing above freezing (red circles on Figure 2) - my definition may be all that works this year.
The GFS ensemble (that creates Figure 2) doesn't see much of a storm on Christmas day (but it does the day after Christmas). The operational version of the model does bring snow in. Figure 5 is for Christmas morning - the mountains have new snow right down, almost to, Boulder. The weatherunderground model (Figure 6) shows 1-3 inches of snow falling later on Christmas day. The GFS (Figure 7) gives us 1/10th to 1 inch of snow into the evening.
Does that count as a White Christmas - Christmas night snow?
The big pattern change after Christmas (seen later in Figure 2) does spell more snow and more long-lasting snow. Figure 8 paints Longmont with 6 inches or more snow over the total of the next 10 days. Wow! More later...
