Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 161054
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
454 AM MDT Mon Apr 16 2018

.SYNOPSIS...A cold trough along the West Coast will move in across
the western Great Basin today and across Utah tonight through
Tuesday. The associated cold front will reach northwest Utah late this
afternoon, then track across the area tonight through early
Tuesday. High pressure will return Tuesday night through midweek,
followed by the next storm system late in the week.

&&

.SHORT TERM (Through 00Z Thursday)...Satellite imagery showing
cold trough along the West Coast with the associated cold front
across central Nevada. This front is running out ahead of the
support aloft so even though it will reach northwest Utah this
afternoon, only the northwest portion of Box Elder County has a
threat of showers today. The remainder of the CWA will have breezy
to windy and warm conditions today as the surface gradient and
winds aloft combine. Deep mixing will create wind gusts in excess
of 60 mph in local areas of the Great Salt Lake Desert and Tooele
Valley. The Wind Advisory for this area has been upgraded to a
High Wind Warning. Also added a Wind Advisory for the Northern
Wasatch Front as the southern portion should easily see wind gusts
near 50 mph this afternoon. Winds already exceeding 60 mph at the
northern end of the Oquirrh Mountains along I-80. All other Wind
Advisories look valid and remain in effect.

Moisture is somewhat limited with the cold front itself as the
best cooling aloft does reach most of Utah until after midnight
tonight. Therefore, backed off on the PoPs for this evening over
eastern and southern portions of the CWA. As the cold air aloft
and the jet dynamics combine after midnight the precipitation
threat will increase. The lapse rate between 700 and 500mb
increases to about 18 degrees C over the CWA by 12Z Tuesday. While
the lapse rate remains the same across the north through midday
Tuesday the lapse rate decreases to 13-15 degrees C over the
southern half of the area. Therefore have increased the PoPs to
categorical over much of the north through midday. Although have
some categorical PoPs in the south, they will be mainly associated
with high elevations and short lived. After midday, only a slight
chance will remain in the southern mountains. However, farther
north, the 500mb cold core and moisture at 700mb will combine to
keep snow showers likely in the mountains.

Windy conditions are expected to continue across the south and
eastern portions through Tuesday. May need to extend the wind
advisory into Tuesday for these locations as the 700mb winds are
near 50 kts with a favorable surface gradient at 12Z near Lake
Powell in particular.

The ridge will move in rapidly Tuesday night with 500mb temps
warming and the air mass stabilizing. Dry conditions with a
warming trend is expected Wednesday under the high pressure.

.LONG TERM (After 00z Thursday)...Higher than normal confidence in
the medium range continues as run-to-run and model-to-model
consistency remains above par. Continue to focus in on the next
trough of the series that will impact the area Thursday-Friday.

Globals are in near lockstep regarding upstream trough evolution,
depicting this trough will close off over the western Great Basin
Wed night, with evolution and track thereafter deepening into the
lower Colorado River basin by midday Thursday. Subtle timing
differences noted 24 hours ago have largely been ironed out.
Continue to foresee areal extent of precip will be more focused over
central/southern portions of the area Thursday night and Friday tied
closer to the H5 cold pool placement, and as such PoPs remain most
elevated across those areas. Return flow about the northern flank of
the mid level circulation may enhance precip along the north slope
of the Uintas/Wasatch Back Friday as well, as a combination of
orographic lift beneath mid level warm advection should promote
broad lift across those areas. The Wasatch Front however, is not
expected to be favored this round. H7 temps only bottom out in the
-5 to -6C range, so snow levels will likely remain above the 5500-
6000ft range limiting impact.

Heights will rebound rapidly by early next weekend allowing temps to
rebound to or above seasonal norms. Tranquil weather on tap to end
the period, sensibly.

&&

.AVIATION...Southerly winds at the KSLC terminal have already been
gusting periodically over 30 mph this morning, and expect speeds
will only increase through the afternoon. South winds are expected
to peak midday into the afternoon, with a 40% chance of speeds
reaching the low to mid 50+ mph range. Additionally, with passage of
the dry cold front between 23-01z, blowing dust has a 30% chance of
lowering visibilities into the high end IFR range briefly. A rapid
switch to northwest winds is expected with frontal passage. Precip
(largely snow) is expected to hold off until after 04-06Z Tuesday.


&&

$$

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from noon today to 10 PM MDT this evening for
     UTZ013-014-019>021.

     High Wind Warning until 10 PM MDT this evening for UTZ003-005-
     015-016.

     Wind Advisory until 10 PM MDT this evening for UTZ002-004.

WY...None.
&&

$$

SHORT TERM...Struthwolf
LONG TERM...Merrill
AVIATION...Merrill

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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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