Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 210404

Area Forecast Discussion
National Weather Service Salt Lake City UT
1004 PM MDT Tue Mar 20 2018

.SYNOPSIS...A moist storm system off the California coast will
weaken as it moves inland across the Great Basin Thursday into
Friday. Another trough moving southward along the British
Columbia coast will impact the region Saturday into Monday.


.DISCUSSION...Satellite imagery showing the moist sub tropical
plume moving northward across central California into western
Nevada ahead of the nearly stationary circulation near 35N and
135W. A lobe of energy rotating NE around this circulation can be
seen as the inflection point in the cloud shield near 30N and
130W. This feature will help pull the ridge farther west and in
doing so cause the sub tropical moisture hose to expand northward
up the California coast. As a result, an even weaker disturbance
near San Francisco will peel off in a more east northeast
direction toward northern Utah late tonight into Wednesday
morning. Although there is good high level moisture associated
with this feature, the low level moisture is being blocked by the
Sierras. Therefore, the threat of showers across Utah Wednesday
morning will be likely be minimal with slight chance in the
northern valleys and chance in the northern mountains. The current
PoP looks to be on the high side. PoP forecast across the central
mountains and eastern valleys appears overdone at this time. Will
let the mid crew make the decision to drop mention of PoPs as
more model forecasts become available.

Across southwest Utah, the 18Z GFS/NAM indicated showers to
develop after midnight. However, the HRRR has been backing off
from this solution past several hours and now the 00Z GFS has only
a few speckles of PoPs. The EC was dry too, so the forecast of
keeping the southwest dry late tonight and early Wednesday looks
reasonable as latest radar shows most echoes dissolving as they
reach the Cal/Nev border. In addition the surface RHs across
southern Nevada are currently generally in the 20-30% range,
therefore any showers should evaporate before reaching the

Cloud cover currently holding temperatures up some, but any breaks
in the clouds could allow the temps to fall to near forecast
values. Therefore, no updates needed at this time.


.AVIATION...Light northwest winds at the KSLC terminal will shift to
the southeast around 05z this evening. Increasing clouds
filtering in from the west will gradually lower ceilings overnight
but remain above 7000 feet.


UT...High Wind Watch from Thursday morning through Thursday evening
     for UTZ015-016.




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