Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 160242

Area Forecast Discussion
National Weather Service Salt Lake City UT
842 PM MDT Sun Oct 15 2017

.SYNOPSIS...High pressure will build into the region for the
first part of the week, bringing a warming trend. The high breaks
down for the latter part of the week with the next storm system
forecast to cross the area Friday into the weekend.


.DISCUSSION...Another quiet night weather-wise is on tap for Utah
and southwest Wyoming, with high pressure building over the Desert
Southwest. On the north end of this high, a westerly flow at jet
stream level is pushing some cirrus clouds across the Great Basin
this evening. These high clouds will continue off and on through
Tuesday, and will be basically the only cloud cover to speak of
through the first half of the week.

Most of the work week will be categorized by dry weather with a
warming trend. Winds will be relatively light for the most part,
though southerlies will begin to increase on Thursday ahead of an
approaching Pacific trough, which will slide across the
Intermountain West Friday and Saturday.

The forecast for tonight looks fine and no changes are planned.
The previous long term discussion follows.

.LONG TERM (After 00z Thursday)...A shortwave trough will move
through the southern part of the fcst area early Thursday ahead of a
larger trough centered over the Pacific Ocean. The passage of the
shortwave will have little impact on sensible weather, but it will a
cause the flow to back to a southwesterly direction. With improved
mixing due to the increasing southwesterly flow and fairly warm
temperatures aloft, Thurs will likely be the warmest day in the
extended for most of the fcst area as maxes run 5-10 degrees above

The large trough over the Pacific will move inland and amplify
during the day on Friday. With the approach of the trough gusty
southwest winds will overspread much of the area particularly in the
west desert. The trough will tap into some subtropical moisture and
this additional moisture combined with modest low lvl isentropic
upglide will result in elevated precip chances Friday afternoon over
the western 2/3rds of the forecast area. This initial precip will
likely fall primarily as rain as snow levels look to be in the 9-10k
foot range. The trough will push a cold front through the area late
Friday into early Saturday. This front looks to be quite active from
a precipitation standpoint, but not particularly cold as snow levels
will only drop to around 6500-7000 feet after the passage of the

The trough moves east of the area Saturday and building heights will
put an end to any lingering orographic showers. Although guidance is
in general agreement that ridging will build over the Western US
early next week there are some discrepancies over how quickly this
occurs. The GFS operational closes off a piece of the passing trough
southeast of the fcst area on Sunday which puts the area under a
cooler northerly flow before the ridge axis starts to push overhead
on Monday. Meanwhile the EC, Canadian, and the GFS ensemble mean
quickly build the Pacific ridge eastward putting the area under a
warmer westerly flow. Leaned towards the latter scenario this
forecast package and raised Sunday maxes a few degrees. Regardless
the building ridge should kick off a general warming trend and the
beginning of next week looks dry with temps running a few degrees
over climo for most of the area.


Little operational concerns at KSLC with VFR conditions and clear
skies prevailing through the TAF period. Mainly northerly winds
will shift to the southeast between 02 and 04Z.





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