Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 182123
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
323 PM MDT Wed Oct 18 2017

.SYNOPSIS...A warm airmass will remain in place through tomorrow.
A weak disturbance will lift across Utah late tonight into
tomorrow, followed by a stronger and colder storm system for
Friday afternoon into Saturday.

&&

.SHORT TERM (Through 00Z Sunday)...A warm zonal flow is in place
over the forecast area this afternoon. Temperatures are quite mild
across the higher terrain and also for most valleys due to
improved mixing. Currently seeing maxes up to 5F above seasonal
normals for valley locations.

Clouds are continuing to increase over southern Utah as a weak
weather disturbance approaches from southern Nevada. This wave is
progged to cross southern Utah tonight into tomorrow morning
before lifting northward as it weakens. Little moisture is
associated with the wave, but it brings enough instability for the
possibility of a few showers over the higher terrain tonight
through tomorrow afternoon.

Southerly flow will start to pick up during the day Thursday as a
larger storm system approaches the Pacific coast. The better
mixing that comes from this flow will allow for a bit more warming
of temperatures tomorrow, with maxes running up to 10F above
seasonal normals. Winds will become quite breezy on Friday as the
storm system moves closer, though at this time it appears the
winds will not be strong enough to warrant any highlights.

The storm system is progged to track across the forecast area
Friday afternoon through Saturday morning, bringing a cold front
through as it does so. Moisture still does not look particularly
impressive with this system, but current model runs look a bit
better than in days past, particularly over northern Utah Friday
afternoon/evening with the leading wave. As a result, have bumped
POPs up somewhat during that period. Looking at snow levels around
6000 feet with the best chance of precip, though 700mb temps
should drop as low as -8C by Saturday morning, so cannot rule out
a few valley flakes. Main impact, however, will be cooler
temperatures with maxes running up to 10F below seasonal normals
on Saturday over northern Utah and southwest Wyoming, a 20F change
from highs anticipated on Thursday.

&&

.LONG TERM (After 00z Sunday)...A well defined warm front on nw
flow is forecast to begin crossing UT at the start of the long
term period. There is considerable low level moisture in the
models with this feature as it crosses nrn UT overnight. However,
these warm fronts are often just clouds and the models do not spit
out any precip in our CWA, so have kept clouds in the grids but
have pops pretty much below 15 pct for Sat night.

Short wave ridging noses in on Sun bringing warming temps and
clearing skies to the north. A very weak wave clips nrn UT on Mon
with a slightly cooler airmass, an increase in winds and clouds,
but no precip. The good mixing however should allow temps to
remain mild.

Strong ridging then dominates the Great Basin thru day 7 with a
mild dry airmass over the CWA. Increasing valley inversions will
tend to hold temps back across the nrn and eastern basins but they
should still warm above normal.

&&

.AVIATION...Northwest winds at the KSLC terminal will shift back
to the southeast around 04z this evening.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

SHORT TERM...Traphagan
LONG TERM/AVIATION...Wilensky

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php


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