Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 271138
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
538 AM MDT Thu Jul 27 2017

.SHORT TERM...(Today through Friday)
Issued at 355 AM MDT Thu Jul 27 2017

Diurnal cooling brought an end to lingering showers over the
forecast area late in the evening and skies had become mostly
clear overnight.

As mentioned in the previous discussion, high pressure expanded
westward early this week breaking off the direct flow of monsoon
moisture into the region. The resultant west to northwest flow was
indicated to bring additional modest drying to the region today
with precipitable water values falling just below 1 inch at most
locations. GFS was a bit more aggressive with the drying but not
markedly. Even at reduced levels there remains more than enough
moisture to fuel scattered afternoon showers and thunderstorms,
mainly over higher terrain from late morning into the evening with
the southern mountains favored. Morning sunshine will help drive
temperatures to levels triggering moist convection. Locally heavy
rain is likely.

Showers and thunderstorms should largely diminish during the
latter part of the evening and overnight, however both NAM and GFS
suggest showers may linger over the San Juans and lower elevations
to the south so will leave some chances across those areas. More
of the same expected Friday, though models were consistent in
boosting moisture levels a bit which should translate into
increased shower/thunderstorm coverage with both the southern and
central mountains favored.

.LONG TERM...(Friday night through Wednesday)
Issued at 355 AM MDT Thu Jul 27 2017

Latest models appeared to be picking up on a disturbance
approaching the Four Corners late Friday night with divergence
aloft beneath the right entrance region of a 55 kt jet to the
north. Nocturnal showers and embedded thunderstorms appear a
strong possibility for all but the northernmost areas of eastern
Utah and western Colorado. Heightened chances will continue during
the day as the destabilizing effects of surface warming combine
with the disturbance moving slowly northeastward across southwest
Colorado. GFS suggests a bit of a downturn in moist convective
activity on Sunday and Monday while the ECMWF was more generous
with QPF across the region. The EC solution appeared most
reasonable as PW values will remain at or a little above an inch
across the forecast area during the latter part of the weekend
into early next week. High pressure realigns back to the west
Tuesday and Wednesday as the low pressure trough over the eastern
U.S. deepens. As a result, the region will see a trend toward
drying through Wednesday with afternoon/evening storm coverage and
heavy rain potential declining each day as temperatures recover to
near normal levels.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 538 AM MDT Thu Jul 27 2017

Scattered showers and thunderstorms are expected to develop over
the mountains late this morning and continue into the early
evening. This activity will be most prevalent over the San Juan
Mountains. TAF sites face little chance of having thunderstorms
move overhead, though storms in the vicinity of KASE, KTEX and
KDRO will likely generate outflow winds to 30 MPH. Otherwise, look
for VFR conditions at TAF sites to continue over the next 24
hours.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...NL
LONG TERM...NL
AVIATION...NL



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