Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 142216

Area Forecast Discussion
National Weather Service Salt Lake City UT
316 PM MST Sun Jan 14 2018

.SYNOPSIS...Strong high pressure centered to our west will start
to weaken on Monday. A weak system will cross the area late
Tuesday through early Wednesday. A colder and wetter weather
pattern will develop starting Friday.


.SHORT TERM (Through 00Z Thursday)...Mid level ridging centered
over the Great Basin continues to maintain dry and very mild
conditions across the forecast area. This ridge will weaken a bit
Monday, in response to an upper trough encroaching on the Pacific
Northwest coast, and a downstream trough digging into the Plains
region. As a result the airmass aloft will cool slightly, and
coupled with increasing high clouds should allow temps to run a
couple degrees lower across most locations, with the exception of
northern valleys where weak inversions remain in place. Temps
Monday may run closer to persistence in these locations.

The models continue to eject a splitting shortwave inland Tuesday,
with the bulk of the dynamic lift passing well north of the
forecast area, with only a trailing and weakening mid level
moisture axis reaching the eastern Great Basin Tuesday afternoon
into Tuesday evening. The EC is a little more aggressive with the
southern portion of this split, and would result in a better
chance of showers across the south Tuesday afternoon/evening.
Increased PoPs a bit for this area, however all in all this will
be a very low QPF event regardless. Left the north relatively
unchanged with chance PoPs Tuesday evening/night, but did remove a
mention of precip on Wednesday given the faster and weaker trend
in the models.

.LONG TERM (After 00Z Thursday)...The ridge over the western Great
Basin shifts overhead through Wednesday night and Thursday morning,
as a stronger trough pushes into the Pacific Northwest. Winds across
Utah and southwest Wyoming begin to increase Thursday
afternoon/night ahead of this storm, with the strongest winds
expected across southern Utah Friday morning and/or afternoon,
depending on the timing of the storm. Have increased wind speeds in
the forecast through this period.

Models continue to push the associated cold front through northern
and western Utah through the day Friday, with rain likely switching
to snow in most northern valleys. There is still some uncertainty
about the structure of this storm, notably how much energy digs
south, and whether it does so to the west of Utah. However,
confidence still remains fairly high for a widespread precipitation
event Friday into Friday night, with a cold airmass pushing into the
entire state by Saturday morning. It also looks likely that moist
northwesterly flow will keep snow going in the mountains through
Friday night and potentially into Saturday, with significant
accumulations possible. Despite some lingering questions, this
currently looks like one of the better storms the area has seen in a
while. (Forecaster waives all liability if the previous sentence
serves as a powerful jinx against the storm.)

The storm likely exits through the day Saturday, with a cold airmass
remaining over the area. Weak ridging looks to build over the Desert
Southwest heading into Sunday/Monday, with a possibility of some
warm advection precipitation in the westerly flow across far
northern Utah, depending on how far north the next storm track sets


.AVIATION...Operational weather concerns will remain minimal at the
KSLC terminal through the valid TAF period. Light and variable or
light northwest winds will remain in place through 03-04z before
returning to a light southeast for the overnight hours. VFR
conditions will be maintained under largely clear skies.





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