Morning Arctic Update

Lots to talk about this morning.  We'll start with the temperatures.  The big "winners" in the northwest US at 1500 UTC (0800 MST) this morning are Jordan and Havre, MT, with temperatures of -40F and -38F, respectively.

Image credit: NCAR/RAL

It's been a remarkable two days in Jordan.  Temperatures have fallen from 4F to -40F.

The conduit for Arctic air between the Wind River and the Uinta Mountains shows up quite nicely in the surface plot above.  Note the strong easterly flow at Rock Springs (RKS), Evanston (EVW), and Ogden (OGD).

The Mesowest surface plot shows -8F or so air penetrating westward along the I-80 corridor into Utah.  Easterly "canyon winds" are observed along the east bench of the Wasatch Front from roughly Mill Creek Canyon north.  West of the east bench, the flow is northerly and northwesterly and quite strong.

A closeup shows evidence of the Sandy Eddy.  Note the easterly flow at the University of Utah and Parley's Canyon, northwesterly flow near Midvale, and southwesterly flow near Draper.

Looking at meteograms, it's difficult to find a bonafide back-door Arctic Front passage as suggested yesterday by the WRF model.  Nevertheless, the onset of easterly flow is quite abrupt at several stations.  For example, at the Mouth of Parleys, the wind shifts to northeasterly at about 0400 MST.  This was accompanied by a 4F drop in temperature, and followed by a gradual decline to 10F this morning.  Thus, the Arctic air is here.  Winds are also gusting to 36 mph.

It's not unusual for the Mouth of Parley's to observe strong morning easterly flow, so let's have a look at Ogden-Hinkley Airport.  Here, winds were northerly for much of the night, but have recently shifted to east-northeast with a gust to 37 mph.

Here at the U we're presently 10F with winds 18 mph gusting to 24.