Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 140300
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
900 PM MDT Fri Oct 13 2017

.SYNOPSIS...A strong but largely dry cold front will cross Utah
tonight. A colder northerly flow will follow the front on
Saturday. Dry high pressure will build into the region for the
first part of next week bringing a warming trend.

&&

.DISCUSSION...Surface cold front is currently near a KENV-KEVW
line this evening and will continue to track southeast through
much of the forecast area through the overnight hours. The
associated upper trough is nosing into northwest Utah, though
precip over that corner of the state is spotty at best. More
widespread precip has developed over Idaho, where there is better
upper level support.

The trough will continue to slide across northern Utah and
southwest Wyoming tonight into tomorrow morning, remaining
moisture starved as it does so. As a result, associated precip
will be light and primarily confined to locations closer to the
Idaho border. The airmass behind the front will be quite cold,
with 700 mb temps dropping to as low as -11C over northern Utah by
tomorrow morning, easily cold enough to support flakes down to
valley floors there, but no accumulation expected due to the lack
of moisture. With this colder air in place, maxes tomorrow are
expected to run at least 10-15F below climo across most locations,
with better cooling across northern portions of the forecast area.

Northwest winds behind the front will become gusty and will be on
the strong side for areas in Castle Country prone to such
downslope winds, as 700mb flow is expected to get as high as
50kts. Going wind advisory covers this threat well. 700mb flow is
not as favorable in other areas that do well in northwest flow so
have not added any additional headlines. Flow becomes more
northerly by Saturday afternoon as the trough exits, which is the
favored direction for Washington county gap winds. However,
associated flow and cold air advection does not seem to be strong
enough for a significant event.

High pressure is progged to rebuild for early next week resulting
in strong drying and warming aloft. However, with mixing becoming
more limited the warm up for most valleys will be slower, though
maxes should be at or above seasonal normals by the middle of the
next week.

No updates expected to the forecast this evening.


&&

.AVIATION...Light but prevailing southeasterly winds at the SLC
terminal are expected to shift to the north and increase between
04Z and 06Z with the passage of a cold front. There is a 30
percent chance this shift will occur an hour or two later than
expected. Showers are expected to increase in the vicinity of the
terminal overnight, and it is likely that cigs will drop to or
below 6000 feet AGL for a time in association with these showers.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from midnight tonight to 9 AM MDT Saturday for
     UTZ012.

WY...None.
&&

$$

Traphagan

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