Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 221043
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
443 AM MDT Sat Jul 22 2017

.SYNOPSIS...Drier air will gradually spread back into the area
from the northwest through Sunday. Deeper moisture will return to
Utah Sunday night and Monday.

&&

.SHORT TERM (Through 12Z Monday)...Partly cloudy skies are in
place across much of Utah and southwest Wyoming this morning, with
clear skies in northwest Utah where drier air has been pushing
into the state with a west-northwest flow aloft. This drying trend
will continue through the day, with precipitable water values
falling significantly in all but the Utah/Arizona border area.
This should largely confine convective activity today to the
southern half of the forecast area, with the possible exception of
initiation off the Uinta Mountains. In addition, storms should
generally be less efficient with regards to heavy rain today,
except near the Arizona border.

A northern trough currently over the Great Plains, which helped
establish the zonal flow over northern Utah, will exit further
east through the day, allowing a ridge to amplify over the
Intermountain West by late today. This will yield hot afternoon
temperatures across the area both today and Sunday, with highs
about 5 degrees above climatological normals in many locations.

As the ridge center slowly shifts eastward, the deeper moisture
that had been sitting over Arizona looks to begin moving north
into Utah starting Sunday afternoon/evening, though the best push
will likely hold off until Monday morning.

.LONG TERM (After 12Z Monday)...The broad upper level ridge will
shift slightly eastward beginning in the extended period as a trough
meanders up the Pacific Coast through the first half of the week.
The cyclonic flow will pull moisture from the Gulf into southern
Utah and the southern Great Basin Monday into Tuesday. Forecast
precipitable water across southern Utah (the more favored moisture
rich environment) soars from 0.8 inch to 1.0 inch previously, to
near 1.5 inch by Tuesday. The 1.0 inch contour shifts northward
across western and northern Utah. The mid-level steering flow
becomes unsettled and disturbed Tuesday, lending to an active storm
day across the area. Trended PoPs upward late Monday through early
Wednesday for this pattern shift. Mid level mixing ratios jump to 12
- 14 g/kg across southern and eastern Utah through Wednesday,
pointing to a very moist environment with rather weak steering flow
This should point to an enhanced threat for flooding concerns
Tuesday into Wednesday. The timing of the moisture surge may play a
part into diurnal heating and storm evolution, but the ingredients
are in place. Will have to keep an eye on how this pattern evolves.

As the trough feature shifts inland and through the Northern Rockies
late in the week, the high shifts eastward with the best moisture
also moving east and a drying (subtle) moving in from the west.
Perhaps a brief break in the thunderstorm and rain shower activity
to end the week. Temperatures aloft change very little day to day,
and suspect the moisture and cloud cover will play a bigger role in
how the temperatures react. Have kept a pretty minimally changing
day to day temperature trend through the going week ahead.

&&

.AVIATION...Southeasterly winds at the KSLC terminal will persist
until a switch to the northwest sets in between 18z and 19z. Skies
should remain mostly clear and winds are expected to switch back to
the southeast after 03z this evening.


&&

.FIRE WEATHER...A drying trend from the northwest is continuing across
Utah today, with mostly sunny skies expected across much of the
north. In the southern half of the state, isolated to widely
scattered showers and thunderstorms will again be possible, but
only locations near the Arizona border will have a great chance
for wetting rain. Storms will be fairly similar on Sunday, before
deeper moisture returns to the entire state Sunday night through
Monday. Apart from storms, winds in most locations will remain
fairly light through the weekend and into the beginning of next
week.

&&

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

$$

SHORT TERM/FIRE WEATHER...Schoening
LONG TERM/AVIATION...Dewey

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