Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 231131
Area Forecast Discussion
National Weather Service Salt Lake City UT
530 AM MDT Thu Mar 23 2017
.SYNOPSIS...A Pacific storm system will continue to move east across
the Great Basin today. High pressure will return for Friday,
followed by another storm system this weekend.
.SHORT TERM (Through 12Z Sunday)...An upper trough remains
over the Great Basin this morning with a closed circulation spinning
up across eastern Nevada. The upper jet has slid east across the
Four Corners region and extends into southwest Colorado. The trough
and associated closed circulation will continue to cross Utah today
and exit the region this evening.
An area of heavier precipitation overnight across southern Utah
associated with the diffluent flow along the left exit region of the
jet has now shifted to the far eastern portions of the forecast area
and will gradually move into Colorado this morning. Meanwhile, a dry
slot has worked its way into southwest Utah ahead of the closed low.
Precipitation has filled in across portions of northern Utah over
the past few hours near the trough axis which extends from near Bear
Lake to Callao. This axis will serve as a focus for precipitation
today. As a result, expect periods of heavy precipitation to
continue across northeast Utah/southwest Wyoming through west-
central Utah this morning, then spreading into southwest Utah by
late this morning. This entire swath of precipitation will then
continue to shift east through the afternoon hours before exiting
the area this evening.
Locally heavy rain can be expected to continue across some valley
areas. Snow levels should fall to the vicinity of 6000ft with heavy
snow across the higher terrain, especially above 8000ft. A Winter
Weather Advisory remains in effect through this morning for the
mountains, but it may need to be extended through this afternoon if
snow intensities warrant it. Otherwise, keeping an eye on northern
Utah rivers. Because precipitation was more spotty for much of the
night, rivers have not had a particularly huge response and have
mostly trended lower than previously forecast. Hi-res models are
indicating significant amounts of QPF (over an inch in some areas)
today across portions of Weber and Cache counties, but current radar
trends suggest that this may be overdone across the far north, and
the GFS/NAM agree, coming in with much smaller amounts. The near
6000ft snow levels today should also help limit runoff.
A shortwave ridge will briefly build into the area tomorrow,
resulting in warmer and drier conditions. However, another trough
will be crossing the West Coast tomorrow and will continue through
Utah late tomorrow night through Saturday. Widespread precipitation
can be expected once again with this storm with snow levels falling
to near 6000ft. This will be a faster-moving system and storm totals
will not be as large as this current storm, but brief heavy
precipitation can be expected.
.LONG TERM (After 12Z Sunday)...The active weather pattern looks to
continue through the long term period, though the latter half of the
weekend begins with high pressure over the forecast area. This ridge
shifts east Monday ahead of the next approaching Pacific storm
system, which consolidates into a closed low before tracking along
the UT/AZ border beginning Monday night. EC is a bit faster with
this storm, moving it through the Four Corners by Tuesday night. In
the latest GFS, the system drifts over Arizona through Wednesday
before tracking east of the area Wednesday night/Thursday morning.
Regardless, both models bring another round of solid precip to the
entire forecast area as the system passes.
Brief ridging is expected early Thursday in between systems, but
models are in good agreement that a colder Pacific Northwest system
moves through beginning Thursday, likely remaining over the area
well past day seven. Have bumped up POPs at the end of the forecast
period to account for this system.
.AVIATION...VFR conditions are expected to prevail at the SLC
terminal this morning, but there will be periods of MVFR conditions
in heavier rain, primarily through 16Z. West to northwest winds are
expected throughout the day.
UT...Winter Weather Advisory until 11 AM MDT this morning for
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