Area Forecast Discussion
Issued by NWS Grand Junction, CO

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796
FXUS65 KGJT 091728
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1028 AM MST Sat Dec 9 2017

.SHORT TERM...(Today through Sunday)
Issued at 415 AM MST Sat Dec 9 2017

Classic Rex block setting up today along the Left Coast today
which will persist through the weekend. Another effective pattern
for keeping moisture out in the Pacific. So with no precipitation
to worry about the challenge turn to temperatures. This appears
simple enough with mainly clear skies and a big ridge in place
however confidence is getting a bit bruised by the strengthening
inversion. Looking at 24hr temperature change much of the higher
terrain is a good 5 to 15 degrees warmer this morning than last
and the valleys are generally cooler. Craig 15 degrees and Cortez
20 degrees cooler. Model sounding suggests the mid levels
continuing to warm while the PBL is showing a widening dew point
depression. Warmer air over cooler and drier air suggests valleys
and basins will struggle. The lack of snow cover is only making
coming up with a good temperature forecast more difficult.
Strategy for now is to build temperature forecast off persistence
then try and pinpoint areas where confidence is high enough that
the inversions will make a difference.

.LONG TERM...(Sunday night through Friday)
Issued at 415 AM MST Sat Dec 9 2017

All the midrange models show the strong Great Basin ridge
continuing to dominate weather across the western U.S. Dry and
stable conditions with north-northwest winds aloft are expected
through the weekend plus next Monday and Tuesday. On Tuesday night
and Wednesday a minor shortwave drops into NW Colorado and the
ridge is pushed west. This trough is projected to be dry so little
or no precipitation is expected. The dry NW flow aloft will
continue through Friday along with a gradual warming trend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1028 AM MST Sat Dec 9 2017

Northerly flow under building high pressure will result in mostly
clear skies for the next 24 hour period with VFR conditions
prevailing and light terrain-driven winds. Some patchy, localized
fog may develop near KEGE after 14Z through late Sunday morning as
seen the previous two days as valley inversions strengthen
overnight.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...15
LONG TERM...CC
AVIATION...MDA



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