Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 051100
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
400 AM MST Tue Dec 5 2017

.SYNOPSIS...Strong high pressure centered to the west of Utah
will maintain a stable northerly flow across the Great Basin
through the end of the week.

&&

.SHORT TERM (THROUGH 12Z FRIDAY)...Many northern valley areas
finally saw the first accumulating snowfall of the year with the
cold storm system than just exited the area. Now that we got that
out of the way, it`s time for that other part of winter in Utah, an
extended period of valley inversions, because that cold air in the
valleys ain`t going anywhere anytime soon, as strong high pressure
builds into the western CONUS.

Inversions will not be too bad initially. Mountains start to warm
today so we`re just getting going. Then, a trough diving south along
the Rockies tomorrow is progged by the models to carve a bit farther
back towards Utah. Although this will not bring any significant
moisture to the area, a few degrees of midlevel cooling and a
tighter surface pressure gradient can be expected. This should
weaken the lid on the inversions, and although winds will likely not
be strong enough to mix out the lower valleys, there should be
improvement in higher valleys. Inversion conditions worsen again on
Thursday as the ridge settles more firmly into the area.

Besides the inversions, the only other thing of note would be gap
winds in Washington County given persistent north-northeasterly flow
as Utah remains east of the ridge axis. These winds will remain
locally gusty through this morning, relax a bit tomorrow, then
increase again Wednesday through Wednesday night with the
aforementioned trough and associated tightening of the pressure
gradient.

LONG TERM (After 12Z Friday)...A strong blocking pattern will
continue to dominate the western CONUS through the extended period
as a very strong ridge will remain persistent along the Pac coast.
Primary impact from this locally will be very stable conditions
owing to a further enhancement of valley/basin inversions and the
side effects of those.

Have continued a trend of lowering valley/basin temps slightly,
largely maintaining near status quo temp conditions whilst WAA
occurs aloft. Anticipate inversion conditions to become fairly
strong through the period, especially for the valleys that maintain
light snow cover through late this week (the Cache stands out).

&&

.AVIATION...Light southeasterly winds currently in place at the KSLC
terminal are expected to switch to the northwest earlier than normal
today, most likely in the 15-16z window. A 30 percent chance winds
will switch after 16z. VFR conditions will be maintained under
clearing skies.

&&

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

$$

Cheng/Merrill

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