Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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472
FXUS65 KSLC 182223
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
423 PM MDT Thu May 18 2017

.SYNOPSIS...A cold upper low centered over the region will slowly
move east into Colorado tonight. High pressure will temporarily
build into the area later Friday into Saturday, before another,
weaker trough clips northern Utah on Sunday.

&&

.SHORT TERM (Through 00z Sunday)...A somewhat moist easterly flow
will wrap around the strong low pressure system now over Colorado
and spread light precipitation across southwest Wyoming and northern
Utah this evening. This precipitation will be in the form of snow
above about 5500-6000 feet with little if any accumulation above
7000 ft. Showers associated with this feature will decrease later
this evening and become isolated along the Wasatch Front while
remain scattered over the mountains and SW Wyoming.

Easterly downslope winds will increase to 20-30 mph with local gusts
near 40 mph possible along the northern and central Wasatch Front
this evening as a east to west surface gradient combines with 20-25
kt 700 mb easterly winds. These winds will also help keep minimum
temperatures up overnight so not expecting any freezing conditions
along the immediate east bench locations but areas removed from the
winds; i.e. west of I-15 may have some pockets of frost by morning.

Farther south, the 500 mb trough will continue to rotate
southeastward across southwest Utah this afternoon into this evening
bringing scattered rain and snow showers the higher elevations and
isolated rain showers to the southern tier from Dixie to Lake
Powell. This trough will move southeast of the 4 corners region by
midnight allowing precip to end and skies to clear. Temperatures in
the normally colder portions of southwest valleys, west central Utah
and the Sevier and Sanpete Valleys will fall into the mid to upper
20s late tonight. Have issued a Hard Freeze Warning for these areas.

Temperatures are expected to moderate by 6-12 degrees Friday but
this will still be below normal. A few showers are still expected
over the central and northern mountains where cold temperatures
aloft will remain. Drier conditions will move in Friday night
through early Saturday, but isolated showers are not out of the
question for the northern mountains Saturday afternoon. Temperatures
will be closer to average by Saturday afternoon across the CWA.

.LONG TERM (After 00Z Sunday)...Under northwest flow aloft, an
overall drying and warming trend will settle in through the
extended period. To start off during the weekend, a shortwave
trough slides southward through the Great Basin to bring just
enough instability and moisture to warrant precip across the
northern locations of Utah, both the mountains and valley
locations, and areas of southwest Wyoming into Sunday and Monday.
A weak PVA associated with this feature seems to be the driving
force for any precipitation development, as there isn`t much of a
baroclinic zone or front associated with this.

Northwest flow again pushes eastward Monday with forecast models
beginning to differ. Models have a ridge of high pressure building
along the West Coast to start the work week, however depending
which model solution is analyzed the ridge will either be further
strengthened and move east or another shortwave will drop south
from the Gulf of Alaska. While different solutions are present,
the overall trend for our forecast area will be near normal
precipitation chances and near normal forecast temperatures. That
said, the warming and drying trend that has been seen the last
several runs still seems like a decent solution. 700mb
temperatures are forecast to warm to near 8-10C by mid-late next
week, and as such temperatures area wide should result in above
seasonal normal values.

&&

.AVIATION...The SLC terminal will see northerly winds prevail
through about 04Z then shift to the southeast. Ceilings should
remain between 4000 - 5000 feet AGL through about 02z before
lifting near 5000 feet AGL. There is a 30 percent chance MVFR cigs
develop near showers through 06z.

&&

.FIRE WEATHER...The cold and wet conditions of the last few days will
begin to moderate beginning Friday as an upper-level low pressure
system moves east of the area. Near-normal temperatures and
humidities are expected by Saturday. A few weak disturbances are
expected from Sunday through the middle of next week. These will
result in breezy afternoon winds at times and a chance of showers
over the higher terrain. Temperatures through the period will be
near to slightly below normal, with the warmest temperatures
possible towards the end of next week..

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Hard Freeze Warning from midnight tonight to 9 AM MDT Friday for
     UTZ014>016.

WY...None.
&&

$$

SHORT TERM/FIRE WEATHER...Struthwolf/Van Cleave
LONG TERM/AVIATION...Dewey

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php



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