Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 212223

Area Forecast Discussion
National Weather Service Salt Lake City UT
423 PM MDT Mon May 21 2018

.SYNOPSIS...A large storm system will enter the area beginning
tonight, bringing unsettled weather through Tuesday and
Wednesday. A ridge will build in for the end of the week.


.SHORT TERM (Through 00Z Friday)...A large closed upper low
continues to spin over southern portions of California and Nevada
this afternoon, with associated cloud cover and instability
spreading into Utah and southwest Wyoming. The best shower and
thunderstorm activity has been across the northern half of the
forecast area this afternoon, as somewhat drier low level air has
spread into south- central and southeast Utah ahead of the low.

Increased moisture and cloud cover will spread into virtually the
entire state tonight through Tuesday, as the low continues its
slow progression across the Desert Southwest. This widespread
cloud cover should lead to a warm night tonight and a cooler day
tomorrow in most locations.

Also of minor note tonight through Tuesday morning- a weak-ish
easterly gradient develops across northern Utah as the surface low
passes through the southern half of the state. This could create
some breezy conditions in typically prone canyon and downslope
areas across the Cache Valley and northern Wasatch Front, but any
gusts will likely remain in the 20-35 mph range.

The widespread cloud cover on Tuesday may also serve to limit
some convection on Tuesday, but there should still be enough
synoptic- scale forcing to allow for scattered showers and
thunderstorms. Activity shifts to the northern half of the CWA on
Wednesday, as the disturbance begins to exit to the northeast and
drier southerly flow returns to southern Utah.

Ridging re-builds over the region Thursday, kicking off a warming
and drying trend for the end of the week.

.LONG TERM (After 00z Friday)...An upper level low will slowly cut
off from the mean flow across the West and gradually fill through
the long term portion of the forecast.  Shortwave ridging will be in
place to Thursday evening into Friday.  As the upper level low
continues to slowly push eastward Saturday, expect enough forcing
for at least high elevation convection by Saturday afternoon and

Global model guidance indicates the upper level low will remain
nearly stationary overhead Sunday into early next week.  This will
likely keep the region unsettled through this period. Started
increasing pops at or above climo.  While the global models have
trended in this direction, would like to see another run or two with
this solution before going too high.

The current outlook for Memorial Day Weekend would be very warm with
a few showers/thunderstorms Saturday, followed by more widespread
showers/thunderstorms Sunday into Monday, especially across the
northern half of Utah.


.AVIATION...The SLC terminal will see VFR conditions throughout the
TAF period with any cigs remaining above 6000 feet AGL. Winds will
generally be northerly through about 04Z then shift to the
southeast. There is a 30 percent chance that passing thunderstorms
over the Wasatch Mtns will cause easterly winds up to 20 mph through




SHORT TERM...Schoening

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