Area Forecast Discussion
Issued by NWS Grand Junction, CO

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541
FXUS65 KGJT 211748
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1148 AM MDT Wed Jun 21 2017

Updated aviation discussion

.SHORT TERM...(Today through Thursday)
Issued at 305 AM MDT Wed Jun 21 2017

High pressure centered over AZ and NM will continue to control the
dry and hot weather over the area today and tonight, though mid
level moisture is gradually increasing under the high. There will
be a slight chance of convective development over the northern
mountains late this afternoon.

On Thursday a weak disturbance will pass over the northern
portion of the forecast area from mid afternoon until about
sunset. Moisture will increase slightly bringing the possibility
of isolated dry thunderstorms over the northern mountains. The
pressure gradient will also tighten causing winds to increase.
This increase in forecast wind speed is less than seen in previous
model runs which makes critical fire weather conditions less
likely. See fire weather discussion below.

.LONG TERM...(Thursday night through Tuesday)
Issued at 305 AM MDT Wed Jun 21 2017

The weak cold front associated with the above mentioned
disturbance will pass through the area early Friday morning, with
slightly cooler are behind it that should ease the heat wave a
bit. Northwest winds aloft and lowering heights will help lessen
the severity of the current heat wave through the weekend.
Temperatures should be only about 5 degrees above average. This NW
flow aloft will continue through Saturday.

Midrange models remain in good agreement that the SW U.S. ridge
with build back over the area late Sunday through Tuesday.
Eastern Utah and western Colorado will be on the eastern fringes
of this ridge, and forecast models indicate a bit of lingering
mid-level moisture backing up against the Continental Divide from
the east early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1148 AM MDT Wed Jun 21 2017

VFR conditions will prevail over the next 24 hours. Occasional
afternoon gusts to 20 mph will be possible at many TAF sites due
to mixing and nearby high-based convection. Otherwise, another hot
day on tap.

&&

.FIRE WEATHER...
Issued at 305 AM MDT Wed Jun 21 2017

Dry weather will continue over the forecast area with only a
small chance of thunderstorm development over the northern
mountains. Only trace amounts of precipitation are expected out
of any development today and Thursday. A low chance of some
lightning does exist with any shower that develops. Winds will
increase slightly during the afternoon on Thursday as a weak mid-
level jet moves overhead. Under full mixing, some of these winds
may translate to the surface resulting in near-critical fire
weather conditions Thursday afternoon. Confidence remains to low
on this borderline event and will not issue headlines at this
time.

&&

.HYDROLOGY...
Issued at 305 AM MDT Wed Jun 21 2017

A flood advisory has been issued for the Roaring Fork River in
Aspen as snowmelt and tunnel closures upstream have caused the
river to reach bankfull. This advisory will run through Friday
evening.

A number of streams and creeks also continue to run strong, cold,
and high and will continue to do so through the week. Where water
is running high, river banks may become saturated and unstable.
Lowlands along the rivers may also become inundated with water.
Remember if you are going to raft, kayak or tube on the rivers be
sure to always wear a life jacket.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Heat Advisory until 10 PM MDT Thursday for COZ006.

UT...Heat Advisory until 10 PM MDT Thursday for UTZ022-027-029.

&&

$$

SHORT TERM...CJC
LONG TERM....CJC
AVIATION...JAM
FIRE WEATHER...CJC
HYDROLOGY...TGJT



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