Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 172330
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
530 PM MDT Tue Oct 17 2017

.SHORT TERM...(Tonight through Wednesday night)
Issued at 159 PM MDT Tue Oct 17 2017

Water vapor imagery across the CONUS today shows a somewhat active
pattern with a substantial trough moving over the Pacific
Northwest, a ridge over northern Mexico and the Desert Southwest,
and several smaller vortices embedded in northwesterly flow.
Skies are mostly sunny with a few high thin cirrus moving in from
the west southwest. Not much change is expected today and into
Wednesday as the ridge strengthens. Temperatures will be on a
warming trend through Wednesday with daytime highs running about 5
degrees above average. Precip chances are very low through the
period with a lack of moisture and forcing.

.LONG TERM...(Thursday through Tuesday)
Issued at 159 PM MDT Tue Oct 17 2017

The long term period starts with the aforementioned Mexican ridge
weakening and shifting to the west under the influence of the
Pacific Northwest trough digging in from the north. As it does
so, a vort max of sub tropical origin, evident as an enhanced
pwat anomaly will rotate clockwise around the ridge moving into
the area Thursday afternoon. NAM and GFS show some strengthening
of the vort max into an open wave ahead of the larger trough due
to strengthening PVA and divergence aloft associated with the
enhanced 300 mb jet to the west. Cloud cover and isolated mountain
showers, with a ruble of thunder or two possible, should develop
Thursday afternoon and exit the area by early Friday. Skies will
clear as the wave ejects into the Central plains and transient
ridging takes hold ahead of the NW trough. Will see an increase in
winds Friday afternoon as the gradient aloft tightens and the jet
moves overhead.

By late Friday and early Saturday the NW trough pushes through
the Northern half of the CWA dragging a cold front along with it.
700 mb temps in the northern Uintas will fall well below -9C
dropping snow levels to just above the surface across much of
Northern Colorado and Utah. Moisture is a bit lacking with this
system as 700 mb mixing ratio struggles to get above 2.5 g/kg.
The lack of moisture and glancing blow from the main forcing
should keep scattered showers and high mountain snow focused on
the northern portions of the CWA. Brought pops up slightly to
highlight the Elk and Gore ranges for some light snowfall.

By Saturday afternoon, the main trough ejects acorss the Northern
Plains placing us in dry cool west northwesterly flow. Global
models agree we will remain in NW flow behind the trough for the
rest of the forecast period. Temperatures will recover behind this
system with mostly sunny and dry skies to start the new week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 530 PM MDT Tue Oct 17 2017

The next 24hrs...VFR. High cloudiness will continue to drift with
no cigs expected. Winds remain terrain dependent and should follow
the typical diurnal directions.

&&

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

$$

SHORT TERM...MAC/ADL
LONG TERM...MAC/ADL
AVIATION...TGJT



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