Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 231030

Area Forecast Discussion
National Weather Service Salt Lake City UT
430 AM MDT Sun Oct 23 2016

.SYNOPSIS...An unseasonably warm southwest flow will remain over
the area today. Moisture will be drawn north into southwest Utah
late today, and then spread across the remainder of the state for
early in the upcoming week. Drier conditions will return for the
middle of the week.


.SHORT TERM (Until 00z Thursday)...The rather warm southwest flow
aloft across the Great Basin will bring one more day of breezy and
unseasonably warm conditions to the state.

Looking at a significant change for the early portion of the
upcoming week. A weak shortwave advancing northeast towards
southern California will tap into moisture pooled off the Baja
coast. This moisture will be drawn quickly north into southwest
Utah by late this afternoon or early this evening. Could see a few
showers reaching into the southern mountains late this afternoon
or early this evening. Not anticipating much in the way of precip
as the dynamic and thermal support for lift will be quite weak
with the advancing shortwave and the lower level of the atmosphere
will initially be on the dry side.

Continued advection of moisture across Utah will leave much of the
state with PWAT values between .75 and .95 inches early in the
upcoming week. Dynamic and thermal support for lift will also
improve as a series of shortwaves ejecting northeast out of the
upper trough off the Pacific Northwest coast will cut across the
northern Great Basin/northern Rockies. Cooler air nudged into Utah
by the passing shortwaves will create a modestly more unstable air
mass to go along with the increasing dynamic support and abundant
moisture. Widespread precipitation should form across the western
half of the forecast area on Monday, with the heaviest precip
concentrated across central and northeast Utah. This precip should
continue throughout Monday night, then decrease from the west
Tuesday as heights begin to rise across the interior west. Strong
ridging across the Great Basin Wednesday will end any chance at
precip, with temps climbing once again to seasonal norms or

.LONG TERM (After 00z Thursday)...Persistent upper level ridging
will continue across much of the region. An upper level trough
digging down the off the eastern Pacific coast will help to shift
the mean ridge eastward by Thursday. This trough is expected to
move onshore across central California coast later Thursday. Given
the ridge location, this trough will split as it moves eastward
into the Great Basin.

The 00Z GFS came in with a much harsher split, which would
dramatically lower the chances of a widespread precipitation event
across the state Friday. The 00Z EC persisted, however, with a more
favorable split for at least a 12-18 hour period of fairly
widespread precipitation across the state Friday.

Given this model to model and run to run disparity, the forecast
continues to be a blend of the much drier GFS and the wetter EC,
especially from Friday morning into Saturday. Hopefully future runs
will come into better agreement, but a combination of model issues
in the shoulder season combined with the difficulty of forecasting
the location of the split will hamper higher confidence in this
portion of the forecast.


.AVIATION...Light southerly and at times variable winds will
continue through the early morning at the SLC terminal. Stronger
southerly winds will develop after 15Z and continue until winds
shift northwesterly between 21-23Z. There is a 20 percent chance
winds will remain southerly all day.





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