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Area forecast discussion 
National Weather Service Salt Lake City Utah
935 am MST Sat Dec 20 2014

Synopsis...a very moist northwest flow is developing over the
area today and will continue into Monday. The airmass will cool
and dry from the north on Monday afternoon.


Discussion...a multi day precipitation event is getting started over
northern Utah this morning. A very moist northwest flow is
punching into the northwest corner of the state this morning. The
strenght of the flow and moisture content of the airmass will
gradually increase through the next two days before decreasing
Monday afternoon.

Latest hrrr shows light precipitation spreading into most of Wasatch
front by 18z and covering all over northwest Utah this afternoon
from about Nephi northward. 12z NAM and 12z GFS also show light
quantitative precipitation forecast over the area this afternoon. Have updated forecast to show
likely probability of precipitation in northern mountains with an inch or two of snow and
have increased probability of precipitation along the Wasatch front to about 50-60 percent
as lowest levels of the atmosphere might take some time to
saturate. No changes to the forecast at this time beyond the afternoon

Quick look at 12z GFS/NAM show similar storm total quantitative precipitation forecast through
Monday as previous runs so current forecasts of 1-3 inches of snow
water equivalent in the mountains still looks good. Snow levels
may climb as high as 8k Sunday afternoon per GFS/NAM...a bit lower
in 00z ec. Winds aloft remain moderate through sunrise Sunday and
then increase through the day Sunday. Have been coordinating with
uafc on progression of avalanche watch to warning.

Latest 12z GFS also trending back towards a stronger storm xmas
evening more like 00z ec...more on this topic in this afternoon's
discussion after the rest of the model arrives and we get a look
at 12z ec.


Aviation...ceilings at the slc terminal are expected to remain at
or below 7000 feet above ground level through the morning...with VFR conditions and
isolated light rain showers. By afternoon there will be a 30 percent
chance of MVFR conditions due to lowering ceilings in heavier rain
showers continuing into the evening. Generally light southerly
surface winds are expected to prevail.


Slc watches/warnings/advisories...
Utah...Winter Storm Warning from midnight tonight to 6 PM MST Monday
for utz007>010.




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