Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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839
FXUS65 KSLC 231626
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
926 AM MST Thu Feb 23 2017

.SYNOPSIS...A cold upper trough over the area today will shift
east on Friday. The next system will cross the area Saturday
afternoon and night, with yet another cold storm on tap for the
first part of next week.

&&

.DISCUSSION...
Water Vapor Satellite a closed low over southwest Wyoming.
400-200mb MDCARS wind observations place a 115-145kt westerly jet
from southern California into New Mexico. GOES/SLC 12Z RAOB/HRRR
indicate that precipitable water values vary from 0.05"-0.10"
Idaho border to 0.15"-0.25" southern valleys.

Going forecast in good shape. Just a few tweaks to PoPs.
Instability showers will persist through the afternoon with the
cold core moving into Northern Utah. While valleys will generally
see 1-4" have seen numerous impacts to travel, closing parts of
I-80 and I-15. This is likely due to the fact that we have not
seen winter driving conditions for a while. Also the showery
nature will spread in heavy snowfall with very low visibility.
Road temperatures near freezing should aid in improvement during
the daytime in between showers.

Have increased gusty westerly winds for the downslope areas of the
Uinta Basin and Castle country this afternoon but kept it just
below advisory criteria. There is a 8mb westerly pressure gradient
across Utah, with 700mb flow 30-35kts.

Updated temperature/RH curve based on observations and latest
model guidance. Rest unchanged.

.PREVIOUS DISCUSSION...
A cold upper trof is centered over nrn UT early this morning
while the associated cold front has moved off to the east. Snow
has ended across most of srn and ern UT with instability showers
redeveloping over the north.

Expect the snow showers to increase over the north thru at least
midday and continue at times into Fri under the deeply cold and
unstable airmass with the upper trof. Greatest impact for the
northern valleys looks to be this morning as highs today are
forecast to reach the mid 30s and valley roads will tend to run
just wet by midday. The advisory for the Wasatch Front and Back
ends at noon and altho it is possible that snow could impact
travel again tonight into early Fri, will leave the existing
advisory unchanged.

The instability snow showers will extend swd thru the day into
tonight but do not expect any significant impact from these
outside of the central mtns.

The trof finally shifts east Fri aftn with short wave ridging
bringing an end to any lingering snow showers. The next trof is
forecast to be a positive tilt feature that drops south thru the
wrn states Sat into Sat night and will be over srn UT by late in
the night. Weak forcing with this trof will result in spotty
mostly light precip with the best chance over the south but the
airmass stays cold enough for it to fall as snow in all areas
outside of the lowest portions of Washington county.

The trough continues to exit the area to the southeast on Sunday
morning, with the possibility of some lingering showers,
particularly in far southern Utah. Otherwise, a short-lived break
between storms is possible through the day Sunday.

The next storm system is right on the heels of the last one,
dropping into the Great Basin Sunday night and Monday. There is a
little uncertainty about the timing and structure of this storm,
but in general it looks to have a decent moisture tap, with low
level cold advection WNW flow developing by Monday afternoon. Have
generally increased POPs Sunday night through Monday night,
especially across the north. With persistent WNW flow, northern
mountain snowfall will likely linger through Tuesday as well.

In addition to keeping POPs high, have also lowered temperatures a
bit for much of the extended forecast, as 700mb temps generally
stay in the -10C to -16C range late Sunday through late Wednesday.
The coldest day could be Tuesday, with high temperatures currently
forecast to be about 10 degrees below climatological normals for
the last day of February.

Drying and modest warming finally look to be on tap for the end of
next week, as a ridge builds over the west coast late Wednesday
through Friday. With better than usual agreement for days 7-10, a
quiet beginning to the month of March looks likely.

&&

.AVIATION...
VFR conditions will generally prevail at the SLC terminal through
the TAF period. Periodic snow showers will briefly lower
conditions to MVFR with a 20 percent chance of IFR which if occurs
will be less than 15 min in duration. Any accumulation will be
brief and less than a 1/4 of an inch. Winds will be west northwest
through about 00-01Z before becoming variable.


&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until 4 AM MST Friday for UTZ007>010-517.

     Winter Weather Advisory until noon MST today for UTZ001>004-006.

WY...Winter Weather Advisory until noon MST today for WYZ021.

&&

$$

PUBLIC...Rogowski/Wilensky/Schoening
AVIATION...Struthwolf

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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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