Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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623
FXUS65 KSLC 150938
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
338 AM MDT Tue Oct 15 2019

.SYNOPSIS...
High pressure aloft will dominate through midweek, bringing
slightly above average temperatures to the region. Cooler
temperatures and a more active weather pattern will develop by
late in the week, with much cooler temperatures and even a chance
of snow for northern Utah by Saturday night into Sunday.

&&

.SHORT TERM (THROUGH 00Z SATURDAY)...
Strong height rises and warming aloft today indicative of a
stable airmass. Mild and dry, though inverted northern valleys
likely to remain cooler with higher RH with high pressure in
control at the surface.

A warming trend tomorrow with increasing south winds as strong
height falls develop along the West Coast, associated with the
next storm system.

Strong height falls arrive by Thursday, supporting increasingly
gusty south winds. Increasing mid-level moisture ahead of the
trough will promote weak instability by afternoon. A few mountain
showers and rouge thunderstorm cannot be ruled out. The bulk of
the precipitation potential looks to be Thursday night with the
arrival of cold advection. The amount of cooling at 700mb looks
to be more significant than at 500mb, which may limit QPF.

Utilizing GOES-16/17 Great Salt Lake temperature remote sensing,
the lake temperature should be near 50F during the 09Z-15Z
climatological peak lake effect time period Thursday night into
Friday morning. The adjusted GFS BUFKIT forecast sounding only
shows shallow and weak instability generated by the Great Salt
Lake. What seems most likely at this point is for some lake
generated showers to persist a bit longer southeast of the lake.

The associated cold front is expected to cross the West Desert
Thursday afternoon, then the rest of the state Thursday night.
This makes way for a significant temperature drop with rising RH
levels Thursday night and Friday. Northwest winds will gusty in
typical downslope areas during this period.

Its noteworthy that the height rises behind this trough are quite
subtle Friday due to upstream activity.

.LONG TERM (AFTER 00Z SATURDAY)...
The EC and GFS deterministic and ensemble members are in good
agreement until about Sunday when the EC has the coldest 700mb
temps into northern Utah at 18Z Sunday, while the GFS is slower
with the trough and brings the coldest 700mb temps in by 18Z
Monday. Since the EC ensemble mean has hedged towards a slower and
deeper solution have leaned toward a GFS deterministic/EC
ensemble solution.

All models are in pretty good agreement that the surface cold front
will move into northwest Utah Saturday evening with the 700 mb temp
near -8C as far south as the central portion of the Great Salt Lake.
It is after this point that the GFS continues to bring cold air into
Utah as it builds the Pacific ridge more strongly along the Pac NW
coast into British Columbia while the EC deterministic shifts the
trough father east due to a less amplified ridge along the west
coast. The best threat of rain and snow will be Saturday night from
about Provo northward. The combination of good jet dynamics, good
500 mb thermal advection and moist low level northwest flow is
figured to bring about 0.25 to 0.50 of an inch of precipitation
along the Wasatch Front and slightly more in the mountains.

PoPs should linger into Monday evening across northern Utah and
southwest Wyoming before clearing out by Tuesday based on the GFS
deterministic which is also supported by the EC ensemble mean.

&&

.AVIATION...
No meteorological concerns at the SLC terminal through the TAF
period. Light southeast winds this morning will shift to northwest
about 18-19Z and then back to southeast at about 03Z this
evening.

&&

.FIRE WEATHER...
Dry conditions with increasingly warmer temperatures and gusty
south winds are expected to develop through mid-week ahead of a
sharp cold front.

Many areas south of I-80 will likely see critical fire weather
conditions Thursday due to the combination of strong gusty south
winds along with low RH.

Cooler with higher RH and a chance for showers Thursday night as
winds become breezy out of the northwest with the passage of the
cold front.

&&

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

$$

SHORT TERM/FIRE WEATHER...10
LONG TERM/AVIATION...Struthwolf

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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