Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 202317

Area Forecast Discussion
National Weather Service Salt Lake City UT
416 PM MST Tue Feb 20 2018

.SYNOPSIS...A winter storm that impacted much of Utah will finally
exit the area this evening. A series of weather disturbances
trailing this storm will impact the area for the middle to latter
part of the work week.


.LONG TERM (THROUGH 00Z SATURDAY)...The upper trough over the area
will continue to slowly shift east out of the area through this
evening. Enough instability remains in place to produce a few weak
snow showers over/near the higher terrain, but drier and more stable
air will continue to gradually work its way into the area.

With a clearing trend this evening, the cold airmass with H7
temperatures ranging from -14 to -20C across the forecast area
tonight, and snow on the ground, expect temperatures to plummet
fairly rapidly with the loss of daytime heating. Needless to say, a
very cold night is in store ahead. However, clouds will be working
their way in late tonight, which would help to counteract some to
the cooling, albeit only slightly, as much of the temperature drop
will likely take place this evening. Patchy fog will also be
possible in a few valleys such as the Cache and perhaps west-central
Utah tonight due in part to the significant snow cover, but for the
most part the drying trend should be significant enough that this
should not become widespread.

A weak trough will cross the area late tomorrow through tomorrow
night. It will be loosely organized, with the best dynamics swinging
well south of the area. Some very light snow may be possible in the
mountains, but otherwise the main impact with this trough will be to
keep the airmass on the cold side.

The next trough on Friday has the potential to produce more
significant snow, at least for central and southern Utah. Have
increased PoPs across this area given good model run-to-run
consistency. However, it remains to be seen how far north the more
significant snow will occur. Both the GFS and NAM are more
enthusiastic with snow across the northeastern zones owing to a
shortwave disturbance ejecting out of the main trough.

.LONG TERM (After 00Z Saturday)...A relatively cold trough will
continue to pull away from the area at the start of the long term
forecast...with remnant snow showers continuing across at least the
southern Utah mountains. The pattern will remain active with a
series of waves riding down the eastern side of the Pacific High.
The next system is expected to impact Utah Saturday into Sunday,
though global models vary on the exact track of this system and the
resulting coverage of precipitation across the state.

While much of the global model guidance indicates the pattern will
stay relatively active and cold next week, the details are
inconsistent at this point. Kept pops above climo for much of the
extended forecast period across at least northern Utah as confidence
in timing is quite low at this time.


.AVIATION...Periodic cigs at or below 6000ft AGL will remain a
potential at the KSLC terminal through sunset, but as a whole
continued improvement is expected. Northwest winds are expected to
switch to the southeast around 03z per norm.





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