Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 232251
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
351 PM MST Thu Nov 23 2017

.SYNOPSIS...A weak weather disturbance will move east across the
northern Rockies tonight which will flatten the strong ridge
across northern Utah. Strong high pressure aloft will return this
weekend, followed by a storm system early next week.

&&

.SHORT TERM (Through 00Z Monday)...Strong ridge of high pressure
will temporarily flatten tonight into early Friday as a weak
disturbance from the Pacific NW moves across the northern Rockies.
This system has tapped moisture from the sub tropics which is
enough of a concern to increase PoPs some for the northern portion
of the CWA for tonight into early Friday. Probably just for the
mountains, but it didn`t hurt to throw some northern valleys in as
well as the GFS shows a significant 300mb jet overhead early
Friday. The broken high clouds associated with this system have
been shielding the sun across most of the CWA today and will
thicken tonight across the north but should thin some across the
south.

Temperatures therefore will be a little milder across the north
tonight due to the cloud cover but be somewhat similar to last
night across the south.

The ridge rebounds in earnest across the region Saturday through
Sunday with amazingly warm 700mb temperatures. This will set the
stage for temperatures to be 10-15 degrees above normal Saturday
and 15-20 degrees or warmer Sunday which means record challenging
warmth.

.LONG TERM (After 00Z Monday)...The forecast area is under a mild
southwest flow at the start of the long term period as the deep cold
trof approaches the coast. The 12z guidance suite remained
significantly at odds on the evolution of this trof as it moves into
the western states with the EC indicating a strongly split system
with a closed low tracking across central NV into srn UT.
Meanwhile, the GFS had trended towards a slower more split
system, but was still about 12hrs faster and much colder.

Often, when a model first indicates a trof will split coming into
the west, that is indeed what ends up happening, and the 18z GFS
came in looking very much like the 12z EC lending additional
confidence to the EC solution.

The forecast however was completed before the 18z GFS came in but
it was trended towards the EC, which ended up as basically a
compromise between the 12z runs. If subsequent runs continue this
trend, there will be a much lower chance of precip for the north,
a better chance of precip for the south, and little if any chance
of valley snow for the north.

Models agree once the low moves east Tue night, ridging will
briefly move in but solutions diverge again towards the end of the
week on how the models handle the next trof and the forecast for
now is dry with temps near normal.

&&

.AVIATION...VFR conditions will prevail at KSLC throughout the
remainder of the day. Light and variable or light
westerly/northwesterly winds are expected to shift to
southeasterly around 02-03Z.

&&

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

$$

SHORT TERM...Struthwolf
LONG TERM...Wilensky
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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