Wednesday, March 16, 2011

Front Today, First Tracks Tomorrow

Things are coming together for what should be a nice dump for the Wasatch and a great day for first tracks tomorrow.

As suggested by the forecast models yesterday, a strong cold front is developing over northern Utah today.  Presently it is in the high 50s over the Salt Lake Valley, but 30s and low 40s over southern Idaho.  Precipitation is falling along the Idaho/Utah border, with scattered snow and rain showers over the Wasatch Mountains and high terrain to the east.

MesoWest plot at 1440 UTC 16 March
The temperature contrast presently north of Salt Lake will concentrate during the day today and a strong precipitation band will develop along and north of the developing cold front.  The NAM model calls for precipitation rates to increase today and this evening over the Wasatch, beginning to the north over the Ogden-area mountains and then sliding southward into the Cottonwoods.   Precipitation then persists through the night as the front moves slowly southward and orographic precipitation develops in its wake.

This will be a warm storm to start.  The 700 mb (10,000 ft) temperature this morning (1200 UTC/0600 MST) was an incredible 3C in the upper-air sounding from the SLC airport, and it is currently in the low-mid 40s at the base of Alta.  Precipitation this morning will be of the liquid or mixed variety below about 9000 feet.  Check out the drops on the camera lens at Alta.

Temperatures will fall, however, during the storm, so we'll see the snow level lowering and the water content of the snow decreasing over time.  Our snow water content algorithm for Alta is going for 15% for this afternoon, 9% by 11 PM, and 5% by 8 AM tomorrow.  So, although the average water content of the storm may be high, it will have the right density profile for ski floatation, which should make for fun skiing tomorrow in the backcountry or if you get first tracks at the resorts, especially since much of this snow will fall overnight when the lifts are closed.  Altitude may be important for the best skiing given the initially high snow level and higher temperatures.

No comments:

Post a Comment