Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 042257
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
457 PM MDT Tue Aug 4 2020

.SHORT TERM...(Tonight through Wednesday night)
Issued at 252 PM MDT Tue Aug 4 2020

Satellite imagery shows scattered cumulus favoring the high terrain
across the northern 1/2 of forecast area. Radar returns show a
couple areas of weak convection generally east of Glenwood Springs
and northeast of Vernal.  Outside of those areas, hot and dry
conditions persist across much of the CWA.  The influence of high
pressure remains over much of the forecast area but that`ll be
changing in near future.  A trough just off the California coast
will move eastward...pushing the axis onshore overnight.  This will
push our high pressure slightly eastward and force us into southwest
flow starting tomorrow.  Winds will increase slightly tomorrow in
this pattern.  However, the strongest winds will remain further west
on Wednesday...not arriving in our area until Thursday.  As this
system approaches, precipitation chances increase in the highest
terrain along the Continental Divide.  However, with what little
residual moisture remains, accumulating rains will be few and far
between.

High temperatures remain at or near record values for this time of
year through the next couple days.  The good news is that (thanks to
the dry air) lows continue to bottom out near (or just slightly
above) normals...giving most areas a temporary reprieve.

.LONG TERM...(Thursday through Tuesday)
Issued at 252 PM MDT Tue Aug 4 2020

High pressure to our southeast and a trough along the West Coast
will continue to influence our weather at the start of the long term.
Flow around the high and coming out of the base of the trough will
keep broad southwesterly flow across the region and with a weak jet
streak aloft, some gusty winds can be expected at the surface. These
winds and continued dry conditions will keep fire weather a concern
as discussed in the fire weather discussion below. As far as
moisture is concerned, forecast PWATs do show values between .5 to
.75 inches Thursday and Friday for the Four Corners and southern
valleys but values for the rest of the CWA look to vary between .25
to .5 inches.  In other words, little change from what we`re seeing
now so the monsoonal push we were hoping for doesn`t really look
like it`ll materialize. A passing disturbance along the CA/US border
will flatten the high pressure and shift it eastward which will
cause the plume of moisture to also lean more to the east allowing
New Mexico and the CO Plains to see some precip while we stay
generally dry. Of note, the EC does keep a bit of precip in the
forecast as it doesn`t flatten/move the area of high pressure as
much as the GFS. Unfortunately, the EC has also been trending
downward so less precip looks to be the rule Thursday and Friday.

By Saturday, a weak, cutoff low forms off the Pacific coast and
meanders around that area through Tuesday and beyond while the high
pressure does the same over west Texas and New Mexico. This will
keep us in a holding patter with generally southwest flow over the
area. Temperatures will remain warm...running several degrees above
seasonal norms...with no widespread or wetting rains expected.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 452 PM MDT Tue Aug 4 2020

Haze and smoke from local and regional fires may occur at KGJT,
KRIL, KTEX, KMTJ, and KDRO but do not expect these TAF sites to
drop below 6SM. Some gusty afternoon winds of 20 to 25kts are
possible again tomorrow afternoon. Otherwise VFR conditions are
expected.

&&

.FIRE WEATHER...
Issued at 252 PM MDT Tue Aug 4 2020

While some spotty critical fire weather conditions are possible
tomorrow for UT fire zone 490, coverage just doesn`t look to be
enough. Winds also look to be weaker so with that, dropped the
Watch for that zone for tomorrow.

No changes, however, to southwest flow setting up as a trough moves
into the West Coast. This trough, and weak upper level support, will
allow stronger winds to reach the surface Thursday and possibly
again on Friday. Dry conditions remain in place so went ahead and
upgraded the Fire Weather Watches to Red Flag Warnings on Thursday.
CO Zone 203 is very borderline on reaching criteria Thursday but
confidence just not enough to pull the trigger, so issued a Fire
Weather Watch for that zone to see another model run or two before
pulling the trigger.  Similar conditions are possible on Friday
though coverage looks to be a bit less.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from 11 AM to 8 PM MDT Thursday for COZ200-202.

     Fire Weather Watch from Thursday afternoon through Thursday
     evening for COZ203.

UT...Red Flag Warning from 11 AM to 8 PM MDT Thursday for UTZ486-487-
     490.

&&

$$

SHORT TERM...SS
LONG TERM...TGR
AVIATION...TGJT
FIRE WEATHER...TGR


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