Area forecast discussion
National Weather Service Salt Lake City Utah
915 am MDT Wednesday may 22 2013
Synopsis...a low pressure system will remain over the Pacific
northwest through this week...keeping most of Utah and southwest
Wyoming in a dry southwest flow. Several weak cold fronts will
enter northwest Utah through the end of the week but will tend to
dissipate before reaching central Utah.
&&
Discussion...cold frontal timing is the big question mark this
morning for the County Warning Area. A prefontal trough is currently located
across far northwestern Utah. A stronger cold front is located
from roughly Elko to southwestern Nevada. Models vary quite a bit
on the timing of this front as it crosses the Salt Lake City area.
The 12z NAM brings the cold front through Salt Lake City around
18-19z and stalls the front in central Utah. The 06z GFS brings
the front through around 21z and stalls the front a bit further
north than the NAM. The latest rap run brings the front through
around 00-01z this evening. Given the current trends...expect a
mainly dry cold front to cross the Wasatch front between 20-22z
and stall south of Utah County. The main impact from this front
will be cooler temperatures.
A large upper level low is currently located near the Pacific
northwest coastal area. Very cold midlevel temperatures are noted
with this low based on the 12z sounding data...with temperatures
near -30c at 500 mb along the Oregon coast. This is quite cold for
middle to late may. This storm will essentially remain near the same
area the remainder of the week.
Several impulses will rotate off this low...bringing dry cold
fronts through mainly northern Utah. This will help keep
temperatures closer to seasonal norms through Friday.
Will update wind grids to match current trends with the
front...otherwise current forecast is on track and no other
updates are needed.
&&
Aviation...the slc terminal will see VFR conditions throughout the
day with some high and middle level clouds. Southerly winds will be
gusty through the morning before shifting to the northwest with the
passage of a cold front between 20z and 21z. There is a 30 percent
chance the frontal passage will occur earlier than expected if the
front moves more quickly across the Great Salt Lake.
&&
Fire weather...the dry cold front moving east across Nevada this
morning will be the driving force behind the increasing southerly
winds today. The strongest winds this afternoon through early
evening will concentrate over the western valleys where gusts will
easily exceed 25 miles per hour. Lowering relative humidity values will also take min
humidities down into the single digits through mid-teens. Pockets of
critical fire weather conditions exist due to the combination of low
relative humidity and winds. However...fuels remain just moist enough that fire
weather highlights are not necessary at this time.
Similar wind and relative humidity conditions will exist across southern...central
and eastern Utah again Thursday. Up north slightly cooler temperatures and
less wind are expected behind the dry front that will pass through
this afternoon and evening.
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Slc watches/warnings/advisories...
Utah...none.
Wyoming...none.
&&
$$
Kruse/Conger/verzella
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