Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 232256
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
356 PM 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.

&&

.SHORT TERM (THROUGH 00Z MONDAY)...
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.

The cold pool aloft will continue to cool through tomorrow
morning, before warming from southwest to northeast. This cooling
will continue to support instability showers mainly across the
north and as far south as the Central Mountains. Winter Weather
advisories have been re-issued through tomorrow morning for many
northern Utah valleys, and through the afternoon for the adjacent
mountains.

The 700-500mb circulation favors wrap-around precipitation across
far northern Utah, especially north of Odgen. Westerly low level
flow will continue to pile the snow into the Wasatch through much
of tomorrow.

The Great Salt Lake may make some contributions tonight into
tomorrow. With a lake temperatures of 42F, adjusted BUFKIT
forecast soundings suggest Lake Induced CAPE of 500-800 j/kg with
an equilibrium level between 15-20kft, plenty of added instability
to intensify showers. Current thinking is the Davis/Weber County
areas will likely see locally higher totals, however the east side
of the Salt Lake Valley has not been ruled out should flow begin
to veer a little more out of the northwest at times. Later shifts
may have to monitor for an upgrade in some of these areas.

With air temperatures near freezing, and road temperatures warmer,
the impacts this afternoon have tended to abate. With the loss of
daylight the heavier showers will likely begin to impact travel
once again with areas of road covered snow and sudden reduction in
visibility to near zero in the heaviest showers. Showers will
end tomorrow night with warming aloft and as heights rise.

A baroclinic zones lays out across central Utah Saturday afternoon
with precipitation re-developing along and behind this boundary
with a positively tilted trough crossing the region. This boundary
should progress out of the forecast area Saturday night into
Sunday morning.

There remains considerable uncertainty with regard to the area
most likely to be affected by this precipitation. As such, decided
to keep PoPs lower until guidance begins to align.

.LONG TERM (AFTER 00Z MONDAY)...
The next storm system is expected to move into the forecast area
beginning Sunday night. EC is noticeably slower bringing in the
initial boundary compared to the GFS (Monday afternoon/evening
versus Sunday night/Monday morning) as it splits the system into
two waves before bringing it through. Regardless, both are showing
a good burst of precip, especially for northern and central Utah,
during the day Monday.

The associated front will bring a reinforcing shot of cold air, with
700mb temps dropping back down to the -14C to -16C range behind the
front. On and off showers and expected to continue through Tuesday
for northern and central Utah with the back edge of the trough
moving through. Have adjusted POPs up slightly with increasing
confidence and also decreased temperatures some in the wake of this
cold airmass.

EC/GFS indicate northwest flow persisting on the front edge of a
ridge off the California coast beginning midweek. This will result
in dry and stable conditions with a warming trend through day seven.

&&

.AVIATION...
VFR conditions will generally prevail at the SLC terminal through
about 09-11Z, although 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. After 11Z snow showers will
increase with prevalent MVFR conditions through about 16Z.
Accumulation of up to 2 inches is possible. Winds will be west
through 02-03Z before becoming northwest.

&&

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

     Winter Weather Advisory until noon MST Friday for UTZ001>003-006.

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

&&

$$

SHORT TERM...Rogowski
LONG TERM...Traphagan
AVIATION...Struthwolf

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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