Area Forecast Discussion
Issued by NWS Grand Junction, CO

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229
FXUS65 KGJT 181705
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1105 AM MDT MON JUL 18 2016

.SHORT TERM...(Today through Tuesday)
Issued at 349 AM MDT Mon Jul 18 2016

Water vapor imagery and underlying derived satellite products
suggest the leading edge of monsoon moisture has pushed across the
4 Corners region into our southern CWA early this morning. PWAT on
the 00Z KGJT sounding was sitting just slightly below normal but
expect this to move above normal by the 12Z flight and pushing
into the 90th percentile by this evening as PWAT pushes near an
inch. It is obvious to say shower and thunderstorm chances will
be on the increase today through Tuesday with this moisture in
place. Not so obvious is the triggers beyond orographics that will
be sparking these storms. Speaking of sparks...lightning this
afternoon after the prolonged hot and dry period will be
especially troublesome for fire starts. Initially the storms will
contain more wind than rain and this could lead to rapid fire
spreads. Storms by late this afternoon should be organized enough
that moderate to heavy rainfall become more of a threat along with
the outflow winds. Do expect a downturn in the convection with
sunset but in this flow showers and isolated storms are likely to
continue somewhere in our area overnight. Confidence low on finer
details but with the jet to our northwest and some upper
divergence projected near the CO/UT border overnight...placed the
higher pops in our western CWA. This is a first guess only and
outflow boundaries and mesoscale features will play a bigger role
on nocturnal thunderstorms. Temperatures will cool back to more
normal mid July readings with the added moisture and associated
cloud cover and passing precipitation.

.LONG TERM...(Tuesday Night through Sunday)
Issued at 329 PM MDT Sun Jul 17 2016

High Pressure centered over the High Plains will continue to
drive monsoonal moisture northward across the forecast area
through the end of the week. Expect little change to the daily
forecast with scattered showers and thunderstorms each day, favoring
the afternoon and evening hours. Locally heavy rainfall will be
possible with precipitable water values holding over an inch. The
ridge starts shifting west across New Mexico and into the Four
Corners region by the weekend cutting off the deeper tap of
moisture. So expect a decrease in activity by next weekend and
much drier weather pushing back in by early next week. Both the
GFS and ECMWF advertising a strengthening ridge over the Great
Basin, basically shutting down the round of monsoonal moisture.

Max temps will be cooler throughout the week with higher humidity
values and more cloud cover in place.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1102 AM MDT Mon Jul 18 2016

Moisture continues to spread north across the region today. Ceilings
remain aoa 10kft agl with this initial push but will be lowering
through the this afternoon as thunderstorm activity becomes more
organized. Gusty outflow winds expected near storms through 21Z
with moderate to heavy rainfall developing through the latter
hours of the day. This may bring temporary mvfr conditions in
rainfall to some forecast terminal sites. KASE and KTEX should
have the highest probability of this occurring but all sites can
not be ruled out. The period of highest confidence in storm
development will be from 18/19Z through 19/03Z.

&&

.GJT Watches/Warnings/Advisories...
CO...Red Flag Warning until 10 PM MDT this evening for COZ200>203-205-
     207-290>295.

UT...Red Flag Warning until 10 PM MDT this evening for UTZ486-487-490-
     491.

&&

$$

SHORT TERM...15
LONG TERM...JDC
AVIATION...JDC



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