Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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367
FXUS65 KSLC 270932
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
332 AM MDT Mon Mar 27 2017

.SYNOPSIS...The next cool and wet storm will impact the region
through tomorrow. A second storm is expected late Thursday into
Saturday.

&&

.SHORT TERM (THROUGH 00Z THURSDAY)...
Ridge axis has shifted across the Rockies, with the approaching
trough making its way inland. A shortwave is making its way across
Idaho and northern Nevada, with reinforcing energy sliding down
the Pacific Northwest coast. A tropical airmass has nosed into the
Great Basin.

The approaching disturbance already firing off showers and
thunderstorms across Nevada and portions of Northern Utah. The
cold front is currently making its way across Northern Utah,
progressing into south central Utah through the morning, and
across the remainder of the state by evening. Models are in good
agreement with widespread precipitation developing along the
frontal zone this morning. This is supported by increasing
diffluence aloft, PVA and the arrival of the exit region of a
cyclonically curved upper level jet.

700mb cold advection is maximized overnight tonight, with the
cold pool aloft dragging across the region through the morning
hours. 850-700mb flow veers from Northwest this afternoon and
evening to North-Northwest tonight. The combination of instability
generated by the cold advection and orographics will continue to
support precipitation especially in the mountains into tomorrow
morning.

A Winter Weather Advisory has been issued for most of Utahs
mountains through 10am Tuesday. These areas can expect between
9-18" of snowfall, though higher totals likely to be spotty due to
the convective nature of the event. Could see a bit of blowing
snow near exposed ridgelines tonight as the colder air arrives.

Precipitation wanes tomorrow afternoon and night with rising
heights, warming aloft and building anticyclonic flow.

Gust northwest winds expected across the desert this afternoon,
but likely under advisory criteria. As the event continues
advisory gusts may materialize in Castle Country (specifically
Fremont Junction) and near canyons in Washington County late
tonight and tomorrow. Will allow day shift to make final call with
wind headlines.

.LONG TERM (AFTER 00Z THURSDAY)...
The wave train of trough/ridge continues through the long term
period, though models continue to hold onto their run to run ideas
making details in the long term forecast challenging for some
areas of the CWA. This specifically holds true to the set up
evolution of the next open wave as it transitions into a close low
over the desert southwest during the late Thursday/Friday
timeframe.

Model solutions regarding this trough continue to diverge in detail
regarding where this low decides to close off, and just how much
cold air aloft it will tap whilst doing so. The 00z GFS continues to
close this off a little further north/west allowing a colder tap to
develop over northern Utah, while the 00z EC is holding steady
closing it off a little further south with the coldest air
dynamically cooled beneath the cold core across the southwest. At
this time, highest confidence for precip falling in the frozen form
to the lower elevations would occur over the southern half of the
area, especially the SW...but can not rule out some of the recent
success of the GFS pulling that zone further north into the central
Wasatch Front Friday. Have not strayed much from a blend (if not
leaning slightly on the colder side) this package but confidence in
detail is low attm.

Moving forward, will have to continue to monitor evolution of the
upper low not only for P-type, but for strong wind potential as
well. Feel moderately confident high wind potential will exist for a
period Friday night into Saturday for both the northern Wasatch
Front and gaps across Dixie. Better model consistency will promote
more detail moving forward.

With differences apparent regarding this first trough, confidence in
large scale pattern evolution thereafter remains low. Have in
general blended potential outcomes and/or trended grids towards
climo regarding evolution and timing of the next upstream trough
early next week.

&&

.AVIATION...
Southerly winds are expected to prevail at the KSLC terminal this
morning beneath thickening clouds and increasing shower potential.
Northwest winds are expected to develop between 19- 21z this
afternoon coincident with increasing rainfall which most likely
will produce mvfr cigs and or visibility at times into this
evening.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory from 9 AM this morning to 10 AM MDT
     Tuesday for UTZ008>010-517.

WY...None.
&&

$$

SHORT TERM...Rogowski
LONG TERM/AVIATION...Merrill

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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