Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 111130

Area Forecast Discussion
National Weather Service Salt Lake City UT
430 AM MST Sat Nov 11 2017

.SYNOPSIS...A weakening upper level trough will graze far northern
Utah through mid-afternoon today. High pressure aloft will return
tonight, followed by a warm and dry southwest flow aloft to begin
the new week.


.SHORT TERM (THROUGH 12Z TUESDAY)...A shortwave trough currently
crossing the PacNW states will continue to track east and graze
northern Utah later this morning. This trough will bring a
reinforcing, but still mostly shallow, cold front into the area
which will push into southern Utah by this evening. Patchy midlevel
clouds are noted on satellite imagery upstream with the approach of
the trough, and some weak disorganized showers are evident on radar
imagery across far northern Utah. With weak 700mb cold advection
across a diffuse thermal gradient and a lack of upper support,
expect the trend to continue with just some weak showers through the
early afternoon hours, producing very minor snow accumulation in the
northern Utah mountains, adjacent higher valleys, and potentially the
Cache Valley.

High pressure will build back into the region this evening as the
trough translates east out of the area. With clearing skies and a
cooler airmass in place, radiational cooling will be effective in
bringing near to below freezing temperature to most valleys tonight.
The ridge axis will quickly shift east of the area tomorrow, with
southwesterly flow aloft starting to increase once again. However,
the winds tomorrow are not expected to mix down to most lower
valleys, so although temperatures in general will trend warmer, this
may not be the case for some of the valleys of northwest and eastern

Temperatures should warm a bit more on Monday as southwesterly flow
continues. This warming trend will have less to do with winds, since
the southwesterlies will again have a difficult time mixing into the
lower valleys, but rather high clouds tomorrow night keeping
overnight mins from plummeting as much.

.LONG TERM (After 12z Tuesday)...A fairly progressive fall pattern
will remain in place through the long term portion of the forecast
period. Tuesday morning will begin with a 110kt+ jet streak crossing
northern Utah attendant with PVA across northern Utah. Much of the
global model guidance indicates enough forcing/moisture will be
available with the passing of this feature to produce at least a
short burst of precipitation for primarily the mountains of northern
Utah Tuesday afternoon into Tuesday evening.

Zonal flow will remain in place behind this feature across Utah as
the next upper level low nears the Pacific Northwest Wednesday.
Global models are inconsistent with the development, timing and
strength of this feature. The 00Z GFS brings a consolidated trough
through the CWA Thursday, with a strong cold front with well
established baroclinicity. 700mb temperatures behind the
least in the GFS version...fall to near -12C across northern Utah.
This system would bring at least a brief burst of snow to much of
northern Utah including the valleys.

The 00Z EC on the other hand, maintains a weaker system with limited
baroclinicity with the front. With an north-south temperature
gradient at 700mb, the coldest temps and thus lower snow levels
remain along the Utah/Idaho border. The 00Z Canadian is closer to
the EC solution.

For now, increased pops a bit across northern Utah to nudge toward
the wetter GFS and GEFS solutions. Held off on introducing low snow
levels like the GFS/GEFS solutions would represent, rather leaning
toward a compromise between the better front in the GFS solution and
the weaker front in the EC/Canadian solutions. As has been the case
most of the fall, confidence in any particular solution for this
system is lower than average.


.AVIATION...Southerly winds will continue at the SLC terminal into
the morning. Expect winds to shift to the northwest as a cold front
passes through the area between 16-18Z.





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