Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 272117
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
317 PM MDT Thu Jul 27 2017

.SYNOPSIS...Monsoonal moisture will remain in place across the
region today. A slight drying trend is expected through the
weekend for most of the area while deeper moisture remains over
southeast Utah through at least the beginning of next week. A
ridge will build near the area by mid-week resulting in a warming
and drying trend.


&&

.SHORT TERM(Through 12Z Sunday)...Short wave moving across Idaho
has brought dry air in across most of nrn Utah this afternoon.
However, right along the Idaho border there remains enough moisture
and dynamics to create convection today. This should continue into
this evening before dissipating. The rest of northern Utah and
southwest Wyoming should see a quiet night with the dry slot well
entrenched. The exception would be across the southern Wasatch
Front and Wasatch Mountains where there is a very slight threat of
showers or thunderstorms reaching that area after midnight before
dissipating.

A subtle shortwave moving northward from the Lower Colorado River
along with a more distinct shortwave over central California will
combine to likely develop a weak deformation zone across southwest
to west central Utah this evening. Have gone with general isolated
thunderstorms there which is very similar to what the HRRR and GFS
would suggest.

Another feature exiting the overall troughiness over northern
California will brush by northwest Utah Friday evening so kept
minimal PoPs there. Otherwise, terrain driven isolated showers and
thunderstorms will occur over the central and southern mountains.

By Saturday, moisture is expected to increase slightly over the
southern half of the CWA as the ridge reforms over New Mexico
importing moisture northward. Temperatures will increase a little
over the north but remain nearly the same or drop a couple of
degrees across the south due to more clouds and more showers.

.LONG TERM(After 12Z Sunday)...The long term period begins with an
inverted trough or potentially a closed low centered over
Northern Arizona and a building ridge over Nevada. This pattern
would place the southeastern corner of the fcst area under deep
southerly/southeasterly flow. This flow would favor deep moisture
transport (perhaps tapping into the tropical moisture associated
with the train of EPAC tropical cyclones) and would aid in the
development of at least scattered convection over south-
central/southeastern Utah Sunday and Monday afternoons. The rest
of the area would be under a more northerly flow regime and
without any obvious dynamical forcing features should remain dry
outside of favored high terrain areas such as the Uintas.

By Tuesday the Nevada ridge is firmly established placing the
area under drier northerly flow on its western periphery. Enough
residual moisture should remain over the southeast to support
terrain- driven convection there Tues afternoon, but the north
will likely remain dry. The H5 ridge continues to amplify over
Nevada on Wed/Thurs (The 600 dam contour makes an appearance in
the GFS), further drying the area and squashing convection outside
of the most favored high terrain locations (such as Boulder
Mountain and the high peaks of the Uintas). Temps will also rise
midweek... likely making a run at triple digits over Northern Utah
on Thursday.

&&

.AVIATION...There is a 10 percent chance that the SLC terminal could
be impacted by showers/thunderstorms between 23Z and 04Z, with gusty
erratic winds as the most likely impact. Otherwise, winds should
switch back to the southeast between 04Z and 06Z, though a slight
chance exists that northerlies persist past 06Z.

&&

.FIRE WEATHER...Isolated showers are expected in three main areas this
evening. The first area will be along the Idaho border, the second
area over west central Utah from Juab County southward to Iron County,
and the third area over the southern mountains. Isolated showers and
thunderstorms will continue over mainly the southern half of the
CWA through the weekend, but will trend downward early next week.
Recent minimum RH values across the valleys have been in the 25-40%
range but will lower to between 15 and 25% through the weekend
but lower into the middle to upper teens by middle of next week
as a strong ridge builds over the region with above normal temperatures
returning.

&&

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

$$

SHORT TERM...Struthwolf
LONG TERM...Carr
AVIATION...Schoening
FIRE WEATHER...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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