Cold Air on the Way

The winter doldrums are almost over.  Good riddance I say!  Monday's "storm" is close enough now that we can look at some of the details.  I put storm in quotes because it is probably not going to be a big storm  for the Cottonwoods (the NWS is presently calling for an inch Sunday night and 3–5" more on Monday), but it is going to come in with a whopper of a temperature change.

The 1200 UTC NAM pretty much tells the tale.  The forecast for 5PM MST tomorrow afternoon calls for a 15ºC 700-mb temperature contrast across the front between northern Utah and the Pacific Northwest.  Yes, that's -20C air at 700 mb, something I don't think we've seen this year.  700 mb is located near 10,000 feet.

By 11 AM MST Monday, the front is through northern Utah, where 700-mb temperatures have fallen to about -21C.

That's bloody cold air.  We don't see many days in Salt Lake City with 700 mb temperatures above 20ºC or below -20ºC.  I jokingly refer to this as my 20/20 rule.  The GFS is a couple degrees warmer than the NAM, but even still, it appears we will see ridge-top temperatures falling to near or below zero fahrenheit on Monday.

The cold air will be here briefly.  As we discussed yesterday, the forecast models are still calling for a shift to a wet, windy, and warm pattern later next week.