Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 201746
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1146 AM MDT Wed Sep 20 2017

.SHORT TERM...(Today through Thursday)
Issued at 248 AM MDT Wed Sep 20 2017

Drier, cooler and breezy to windy conditions will continue today
through Thursday as a strong trough over the Pacific Northwest
moves southeast into the western Great Basin. Winds at the surface
and aloft will gradually shift from west to southwest. The winds
will be a concern for fire weather as discussed in the fire
weather section below. The 100 to 120 kt jet stream core will
be over central Wyoming today but by Thursday afternoon will
pivot to a more southwesterly direction and shift west and south
over western Utah.

.LONG TERM...(Thursday night through Tuesday)
Issued at 248 AM MDT Wed Sep 20 2017

A strong upper level trough is still on track to strengthen and
drop a -25C closed low and cold front into the northern US
Rockies by the weekend. Though we have already had some valleys in
western Colorado drop below the freezing mark, this cold air mass
heading toward the region is going to bring the typically cooler
valleys in northwestern Colorado to near or below freezing min
temperatures for days early next week.

But first, winds will peak Friday as a 110 to 120 kt polar jet
undercuts the closed low and stalls over western Colorado into
Saturday. The first chance of precipitation in this forecast
period is on Friday just ahead of the cold front. Models are
indicating precip will pick up in the San Juans first, then
increase in coverage across the region throughout the day.
Temperatures across the San Juan mountains will be too warm for
snow, but as cold air leaks into NE Utah and NW Colorado, the
eastern Uintas ought to see some high mountain snow and then into
the Elkhead/Park/Gore/Flattop Ranges on Saturday.

Confidence decreases over the weekend as the long range models
have different solutions with what happens to the closed low after
this time period, which will make a substantial difference in how
long precipitation will linger. The GFS is more consistent with
recent model runs and brings minimal precipitation in CAA on
Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1140 AM MDT Wed Sep 20 2017

A few clouds expected today but won`t pose any aviation threats.
The biggest concern will be some gusty winds up to 35 MPH at
times. Winds will start gusting in the next hour and should
subside after 6 PM. Sky clear expected overnight.

&&

.FIRE WEATHER...
Issued at 248 AM MDT Wed Sep 20 2017

Strong winds will continue today through Thursday. Critical
conditions will be avoided over western CO and northeast UT because
the humidity will not be low enough. Southeast UT will avoid
critical conditions due to non-critical fuel condition. Still,
with such strong winds some control problems are anticipated on
any existing or new fires.

&&

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

$$

SHORT TERM...CC
LONG TERM...JAM
AVIATION...TGR
FIRE WEATHER...CC


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