Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 180349

Area Forecast Discussion
National Weather Service Salt Lake City UT
949 PM MDT Wed May 17 2017

.SYNOPSIS...An unseasonably cold upper level storm system will
remain across the region through early Friday. This low will move
east into the northern and central plains by Friday night,
followed by high pressure aloft developing over Utah for the
first half of the weekend.


.SHORT TERM (Through 00Z Saturday)...The center of the very cold
upper low sits along the Utah/Idaho border this evening. Animation
of water vapor imagery shows a slow but steady southward movement
of the low in line with current global model guidance this
evening. This low should continue south through northern Utah
overnight through early Thursday, then turning to the southeast
and moving into western Colorado by Thursday evening.

Convection remains fairly active along the periphery of the upper
this evening. The best organize convection remains well south and
eats of the center along the near 700mb baroclinic from extreme
southern Utah northeast through western Colorado. A second area of
scattered convection associated with a vorticity max rotating
through the western flank of the low underneath the coldest air
aloft associated with this low. This second area of convective
precip will likely expand south through western Utah overnight,
then turn eats with the low Thursday.

Organized precip will continue to focus along any vorticity lobes
rotating around the upper low through Thursday night. The air mass
will remain very cold, moist and unstable through Thursday evening,
then gradually warm as the low center begins to accelerate east
away from the area late Thursday night/Friday.

.PREVIOUS LONG TERM (After 00z Saturday)...On the backside of the
departing upper level low, a moderate 75 kt jet slides south
through eastern Nevada and western Utah with ridging building in
from the west into the weekend.

A rather weak and short-lived ridge becomes flattened by a
shortwave sliding into the Great Basin from the north Saturday
night into Sunday. Somewhat weak, this shortwave doesn`t seem to
have much moisture associated with it or energy to create a
prolonged or widespread precipitation event across much of Utah.
700mb temperature trend with this feature are very minimally
changed with the shortwave that passes through, keeping temps
around 2-4C going into Monday. Daytime temperatures will result in
a gradual warming trend through mid-week as most valley locations
inch towards the 80 degree mark with the exception of far
southwest Utah which will head into the low 90s.

The extended forecast already in place looked good, so made very
minor changes regarding potential for precip in the extended, as
latest model guidance didn`t seem to change much in the most
recent run. Largely, the northern portion of the CWA will be the
main areas impacted by any precip that develops through midweek
next week. The GFS and EC appear to be in decent agreement through
the weekend before diverging on solutions come Monday, with the
GFS eager to kick the shortwave to the south and east quicker than
the EC and building a more amplified ridge over the west coast
into mid week.


.AVIATION... Scattered showers will likely pass in the vicinity of
KSLC during the overnight period. However, there is about a 30
percent chance of these showers directly impacting the terminal
and bringing brief periods of rain or rain/snow mix. Winds will
generally be southeasterly overnight, however erratic winds will
be possible in the vicinity of showers.


UT...Hard Freeze Warning until 9 AM MDT Thursday for UTZ001-006-011-




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