Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 210550
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1150 PM MDT Thu Jul 20 2017

.UPDATE...
Issued at 1150 PM MDT Thu Jul 20 2017

As was the case yesterday, showers and thunderstorms have
decreased significantly in coverage over the past few hours with
the loss of daytime heating. Some isolated showers will continue
overnight but the threat for flash flooding has ended. Therefore,
the Flash Flood Watch will be allowed to expire at midnight.

&&

.SHORT TERM...(Tonight through Friday night)
Issued at 302 PM MDT Thu Jul 20 2017

Showers and thunderstorms, some producing small hail and heavy rain
started to develop late this morning and early this afternoon.
Better instability, a weak disturbance, and boundaries left from
yesterday all contributed to better and sooner development this
afternoon. Expect showers and thunderstorms to continue through the
evening producing small hail and heavy rain. The heavy rain will
cause flash flooding. This trend will continue through Friday
although the moisture plume will be shifted slightly to the east
with the deepest moisture extending from the four corners through
northwest CO. Precipitable water values remain over an inch. Will
let the current hilites play out and let next shift analysis
models and cloud cover for placement for possible flash flood
hilites.

.LONG TERM...(Saturday through Thursday)
Issued at 302 PM MDT Thu Jul 20 2017

Drier air moves over into the area from the north affecting
northeast UT and northwest CO first. Expect a downturn in
convective activity over the north. The south should also see less
activity although deeper moisture will linger longer. Current
model runs focus showers and thunderstorms from lingering moisture
mainly over the divide and associated higher terrain. The slight
down trend in storms continues for Sunday. The ridge builds back
over the Great Basin starting this weekend and strengthens into
early next week. The ridge starts to slide east as a trof enters
the moves inland over OR and northern CA allowing an opening for
another surge of moisture to move toward eastern UT and western
CO. Differences in models means confidence is lower with timing
and placement of the moisture plume. Temperatures will increase
again as the ridge builds.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1150 PM MDT Thu Jul 20 2017

A few showers will continue overnight but will not pose a threat
to any of the TAF sites. Another active day is anticipated for
Friday as scattered to numerous showers and thunderstorms act on
an abundance of moisture. Convection will fire off after 15Z and
steadily increase in coverage after 18Z. Heavy rain, small hail,
gusty winds, and local MVFR cigs/vis will again be the primary
threats with storms. Mountain tops may be obscured at times. Away
from showers and thunderstorms, VFR conditions will be present.

&&

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

&&

$$

UPDATE...MMS
SHORT TERM...AS
LONG TERM...AS
AVIATION...TGJT



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