Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 260543
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1143 PM MDT Tue Jul 25 2017

Updated aviation section

.UPDATE...
Issued at 638 PM MDT Tue Jul 25 2017

Increased PoPs and expanded coverage for higher PoPs down into
southeast Utah, as storms are developing most intensely in
southeast Utah into southwest Colorado on the axis of deepest
moisture. Threat for heavy rain is high with these storms and
should continue well into the evening hours as this area
propagates to the northeast. SPC mesoanalysis indicates 1.5 inch
precipitable water in this region as well as CAPE values up to
3000 J/kg which is quite impressive and being realized as
preliminary and non-operational GOES-16 IR showing cloud tops as
low as -75 degrees C in the strongest overshooting tops indicating
persistent strong updrafts.

&&

.SHORT TERM...(Tonight through Wednesday night)
Issued at 302 PM MDT Tue Jul 25 2017

PWAT is climatologically maxed out this afternoon across the
Utah/Colorado border. We had one batch of rain move north out of
the cwa by noon with some clearing across the SW in the wake of
this rainfall. This heating...and stronger winds aloft associated
with an organized wave moving northward across Central Utah is
creating conditions favorable for stronger storms. Small
hail...heavy rainfall and possibly some gusty winds will be
possible with these storms as they move northward out of Southeast
Utah into West Central and NW Colorado through the evening.
Widespread showers and storms will also continue over the
remainder of the region through the early morning hours this wave
moves through and forces the main moisture plume eastward. Do
expect a decent downturn in the precipitation by sunrise as
subsidence behind this wave kick. Some drier air will be advecting
in from the west on Wednesday but deeper moisture remains over
our southern mountains and when combined with a bit more
sunshine...showers and storms should become likely over the hills
by early afternoon. The eastern valleys should see some storms
drift in through the late afternoon...with drier air and less
focus limiting the storms in the western valleys. Temperatures
will bump up a bit on Wednesday with less cloud cover but still
remain slightly below normal.

.LONG TERM...(Thursday through Tuesday)
Issued at 302 PM MDT Tue Jul 25 2017

By Thursday the upper high will begin to migrate back to the West
as energy digs across eastern CONUS. This will reduce the
northward extent of the monsoonal plume but keep it located to the
south of our border.  We will keep afternoon storms in the
forecast but with a gradual downturn Thursday into Friday. The
models have changed due to a stronger trough located over the Left
Coast going into this late week period. Earlier trends had the
high reforming back over the Great Basin. However now this high
is centered back over our CWA by Saturday and suppressed a bit to
the south due to stronger westerly flow across the US/Canada
border. This seems to allow a bit more monsoonal moisture to seep
under the ridge and begin and upward trend to storms going into
the weekend and early next week. Expect seasonal temperatures
through the long term period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1143 PM MDT Tue Jul 25 2017

Showers and a few thunderstorms will continue through 09z before
moving out of the area or dissipating. High pressure attempts to
build back into the region, and no discernible weather
disturbance passes through eastern UT/western CO Wednesday. Plenty
of moisture will still be around for afternoon thunderstorm
development...but storms will likely fire over higher terrain
then head eastward. Therefore...most TAF sites Wed afternoon
should be missed by any weather with the exception of KTEX, KASE,
KEGE and KRIL.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Flash Flood Watch until midnight MDT tonight for COZ001>014-
     017>023.

UT...Flash Flood Watch until midnight MDT tonight for UTZ022>025-
     027>029.

&&

$$

UPDATE...MDA
SHORT TERM...15
LONG TERM...15
AVIATION...JAM



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