Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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522
FXUS65 KSLC 112142
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
342 PM MDT Fri Aug 11 2017

.SYNOPSIS...Moisture will continue to spread north across
southern Utah and into central Utah through Saturday. A drier
airmass is forecast for much of next week.

&&

.SHORT TERM (Through 12z Monday)...Deeper moisture over southern
Utah is spreading northward into central Utah this afternoon, with
satellite derived PWs as high as 1.2 inch observed as far north as
Green River. Utah and southwest Wyoming are under southerly flow
aloft, so this moisture will continue to slowly spread northward
over the weekend.

The moisture combined with shortwave energy moving through southern
Utah is allowing for good coverage of convection there. Over
northern Utah, showers and thunderstorms are more sparse and
primarily confined to the higher terrain. Coverage of storms will
continue to increase into the evening, with some continuing through
the overnight hours. Little change in temperatures has been observed
between yesterday and today, with maxes running near or slightly
above seasonal normals over northern Utah and perhaps a bit below
climo over southern Utah.

With the trough that was over California lifting north of the area,
a ridge axis is expected to redevelop over the Great Basin Saturday
before shifting overhead Sunday as another trough approaches the
Pacific coast. Flow aloft will initially stay more southerly,
allowing the moisture to continue to move northward on Saturday.
Best convection will again be with the deeper moisture over southern
Utah, but weak shortwave energy moving into northern Utah and
southwest Wyoming Saturday night into early Sunday will enhance
convection for those locations.

On Sunday, the flow aloft is expected to turn more westerly as the
trough slides east and starts to flatten the ridge. This will allow
drier air to move in from west to east. With the initial
introduction of drier air on Sunday, have decreased POPs for western
Utah while keeping them isolated/widely scattered over the eastern
two-thirds of the forecast area. Little change in the temperature of
the airmass is expected through the weekend, so temperature grids
are near persistence.

.LONG TERM (After 12z Monday)...As the pattern transitions from a
flat ridge and zonal flow late in the weekend, an upper level
trough feature digs into the Pacific Northwest and is progged to
dive southeast through the Great Basin early in the week. Global
forecast models had previously been out of step with resolving
this feature and are becoming better in agreement. Moisture
remains pretty stable and unchanged going into the early part of
next week, with better moisture across the eastern half of Utah
and portions of southeast Utah. As the trough swings through Utah
and southwest Wyoming Monday, the best dynamics seem to lie across
the northern half of Utah. The latest EC is trending more north
with the trough while the GFS is a bit farther south. Went with a
blend of both since the agreement was much better than previous
runs.

The trough quickly ejects to the east by late Wednesday when a
drier airmass pushes in from the west and a more zonal flow sets
up to end the week with high pressure developing off the
California coast. Global models are actually in decent agreement
through the start of next weekend, when a monsoonal moisture push
northward shows up in the models, granted this is 8 days out.
Temperatures will not change much day to day with the synoptic
scale pattern, and should continue to run about seasonal normal.

&&

.AVIATION...Outflow from showers passing south of the KSLC terminal
will likely maintain southerly winds through the remainder of the
afternoon and evening, however there is a 40 percent chance of a
return of northwest winds between 22-02Z. VFR conditions are
expected to prevail through the TAF period with only a 10 percent
chance of a shower or thunderstorm directly impacting the
terminal.

&&

.FIRE WEATHER...Moisture pooled over southern Utah will continue to
spread northward over the rest of the district through the weekend.
As a result, showers and thunderstorms will continue to be a threat,
with wetting rains possible. Locally heavy rainfall and gusty winds
will also be possible with some of the stronger storms. Through
tomorrow afternoon, the best coverage will be over southern Utah but
a weather disturbance moving through Saturday night into Sunday will
increase coverage over northern Utah as well. Drier air will start
to move into far western Utah as early as Sunday before gradually
spreading eastward through midweek.

&&

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

$$

SHORT TERM/FIRE WEATHER...Traphagan
LONG TERM...Dewey
AVIATION...Seaman

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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