222 
FXUS65 KSLC 080921
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
321 AM MDT Wed May 8 2019

.SYNOPSIS...Cool and unsettled weather conditions will persist
today over Utah and southwest Wyoming. The focus of showers and
thunderstorms will shift into southern Utah beginning Thursday as
northern portions of the forecast area see a drying and warming
trend into the upcoming weekend. 

&&

.SHORT TERM (Through 00Z Sunday)...The California storm system
that moved across Arizona yesterday continues to weaken as it
passes through New Mexico. A second weak Pacific Northwest storm
system is currently making its way through northern and central
Utah. The combined efforts of these storm systems are producing a
few areas of generally light showers across portions of the state
in a relatively cool and unsettled airmass. Coverage of showers 
is anticipated to increase again by this afternoon with daytime 
heating, as well as additional instability provided by another 
Pacific Northwest wave moving into northern Utah late this 
afternoon/early this evening. 

This second Pacific Northwest storm system is progged to slide
into Nevada tonight before moving into California Thursday
evening. The location of this system is progged to shift the flow
aloft over the forecast area to a more E/NEly direction, with a
favorable gradient allowing for good cold advection from southwest
Wyoming. These ingredients will result in conditions favorable for
downslope/canyon winds over prone areas of northern Utah. Overall,
flow aloft in the overnight model runs is looking more northerly,
which is not quite as favorable, but still think the potential
exists for some marginally advisory level winds tonight. However,
confidence is not high enough to issue any headlines at this time. 

As the storm system makes its way into California, the focus of
moisture and instability over the forecast area will shift to
southern Utah, keeping relatively cool conditions and the threat
of showers and thunderstorms there as northern Utah and southwest
Wyoming see a general warming and drying trend into the weekend. 

.LONG TERM (After 00Z Sunday)...Ridging slowly builds across the 
northern Rockies late week, then into the Great Basin early next 
week. An anticyclonic drying/stable airmass builds in from north 
to south. This suppresses convective development across the north,
shunting deep layer moisture south toward the Arizona border next
weekend. 

Main uncertainty during the extended forecast, is how quickly enough 
moisture builds north within potential return flow early next week, 
to support convective development along the spine of the mountains. 
Some guidance develops a deep eastern Pacific trough mid-week which 
may add additional moisture and lift across the region supportive of 
more widespread convective activity.

The building ridge will support warm temperatures through the 
extended forecast period.

&&

.AVIATION...Light southeast drainage winds at the KSLC terminal 
early this morning will likely switch to out of the northwest 
around sunrise and become gusty for the afternoon. Mountains will 
likely remain obscured due to low ceilings through much of the 
day. Shower activity is most likely during the afternoon, and 
these may lower ceilings further, and may restrict visibilities as
well. Strong gusty/erratic microburst winds look to be a lower 
probability today compared to the past 2 days.

Downslope/Canyon wind event likely to occur to the north of the KSLC 
terminal this evening, persisting at times into Friday morning. This 
usually causes variable but impactful winds at KSLC due to eddies 
off the terrain, as well as the potential for low level wind shear 
north of the airfield.

&&

.FIRE WEATHER...A series of storm systems impacting the district
will keep relatively cool and unsettled conditions in place
through much of the remainder of the work week. Showers and
thunderstorms will be most widespread across Utah today before the
precipitation focus shifts to southern Utah beginning Thursday,
with the threat of showers lasting through the upcoming weekend.
Temperatures will steadily warm over northern portions of the
district beginning Friday, with showers acting to limit warming
over southern Utah. 

&&

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

$$

SHORT TERM/FIRE WEATHER...Traphagan
LONG TERM/AVIATION...Rogowski

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