Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 120429 AAA

Area Forecast Discussion...UPDATED
National Weather Service Salt Lake City UT
1029 PM MDT Fri Aug 11 2017

.UPDATE...Updated aviation discussion. See below.


.SYNOPSIS...Moisture will continue to spread north across southern
and central Utah this weekend. A drier airmass will working into
the area beginning early next week.


.SHORT TERM (Through 12z Monday)... The deep layer moisture (PWAT
values >1.00") from Arizona now cover southern Utah this evening.
This moisture will continue north across central/eastern Utah,
with a secondary push across western Utah Saturday.

Scattered convection across southern Utah has largely ended this
evening. A lingering cluster of thunderstorms entering southwest
Utah from Nevada at time may have enough dynamic and jet support
to persist for a couple more hours as it tracks east into the

Up north convection dies off early this evening, with the only
active area remaining over southern Wasatch county heading for the
Uinta Basin. AN outflow boundary from convection over southern
Idaho has reach the central portion of the GSL, and will continue
south but weakening over the next 2-3 hours. One lone
thunderstorms did develop along this boundary over central Box
Elder county. Doubt this storm will persist much longer, nor will
it strengthen any further than it already has.

Scattered convection should fire up again across southern Utah
Saturday, with scattered convection reaching into central and
eastern Utah during the day. This convection will remain active
across those areas through the balance of the weekend.

Across western Utah suspect the areal coverage of showers/storms
will remain somewhat limited until the higher PWAT values arrive
late in the day Saturday. Convection may become more active
Saturday night/Sunday as deep layer moisture becomes established
and subtle dynamic features trigger stronger convection.

.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

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...A thunderstorm outflow boundaries, one moving rapidly
north from earlier convection near KPVU and the second moving
south from convection across southern Idaho will collide just
north of the terminal around 0430Z. Based on the strengthen and
depth of the outflows, beginning to think the southern outflow
will prevail through the balance of the evening. These winds will
eventually drop off around midnight, with a turn to the north
possible between 06z and 08z.

Cloud cover for the most part will remain scattered around 9 kft
overnight through Saturday morning. Convective buildups over the
surrounding higher terrain during the afternoon are not expected
to impact the terminal during the TAF period.





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