Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 291043
Area Forecast Discussion
National Weather Service Salt Lake City UT
343 AM MST Tue Nov 29 2016
.SYNOPSIS...A trailing cold northerly flow will continue through
midweek. The next storm system will arrive over the Great Basin
late in the week.
.SHORT TERM (THROUGH 00Z FRIDAY)...
Water Vapor Satellite shows the wave which had reinforced the
trough has now progressed into the four corners, with ridging
building along the west coast. 400-200mb MDCARS wind observations
place a 135-175kt cyclonic jet from British Columbia into the
Southwest CONUS and Plains. GOES/SLC 00Z RAOB/HRRR indicate that
precipitable water values vary from 0.05"-0.10" mountains to
Drier airmass is moving in behind the storm. Warming aloft, along
with rising heights and increasingly anticyclonic flow should
continue to diminish the intensity and coverage of snow showers.
Nevertheless, BUFKIT forecast soundings adjusted for a lake
temperature of 44F yields about 500j/kg lake induced CAPE and
with an equilibrium level near 15kft. Thus, periods of snow,
possibly with brief periods of impacts are possible across the far
western Salt Lake valley and Tooele valley today.
Gusty winds will continue today for portions of the west desert,
near Castle Country, and into the southern Utah canyons through
the morning hours. 700mb flow of 30kts, a northwesterly pressure
gradient of 6 mb across Utah, and pressure rises of 4-6mb are
driving the pockets of gusty winds. This afternoon these factors
Tomorrow night into Wednesday morning a dry stable airmass will
be in place. Cant rule out light high elevation snowfall near the
Idaho border with warm advection developing ahead of the next
storm. In fact went a bit more aggressive with guidance with PoPs
with such a strong warm front pushing eastward across the state.
Of course low level moisture will be the final ingredient needed
for the re-development of snow. During the same time cloud cover
should be increasing over northern Utah which should help mitigate
the threat of fog.
Next system drops into Utah Thursday with 700mb cold advection
affecting northern and eventually central Utah through the day.
This is another quite cold storm system which despite the expected
light qpf could create an impact on roads for the afternoon
commute. Have raised PoPs about 10 percent across the board, and
if models continue to present good agreement, PoPs will have to
continue to be raised at a modest clip each shift.
.LONG TERM (AFTER 00Z FRIDAY)...
This next upper trough will continue to amplify south across the
eastern Great Basin into the desert southwest Friday, with the
associated trough axis passing southwest across the state by 18z
Fri. Still expect light snow through this trough axis passage, and
although accums will remain on the light side, some localized
impacts may continue through midday prior to diminishing. These,
most likely, would occur along the I-15 corridor and surrounding
Globals continue to suggest the upper low of this system will settle
over the desert southwest by Saturday, though downstream
translation/progression differences exists regarding its evolution.
Regardless, expecting a window of moderate to strong NE winds to
develop across the southwestern portions of the CWA Friday night as
both the MSLP gradient and H7 winds support gusty winds, especially
in the gaps of Washington County.
Thereafter globals are trending towards a slightly more active
solution across northern/central Utah early next week. Rapid
amplification of the upstream pattern is advertised in both the
GFS/ECMWF, this driving a long wave trough into the intermountain
region early next week. Will have to continue to monitor this, but
for now a largely continental track would limit moisture and
associated precip potential somewhat.
Northwesterly surface winds will continue at the KSLC terminal
through this evening. Though low/mid level cloud cover is thinning
this morning, do expect periodic cigs at or below 6000ft through
18z. This said, these lower clouds should remain more tied to the
local terrain creating localized mountain obscuration than over
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