Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 271620
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1020 AM MDT SAT AUG 27 2016

.SHORT TERM...(Today through Sunday)
Issued at 306 AM MDT Sat Aug 27 2016

The trough that has persisted over the Great Basin the last few
days will lift and in its wake, a closed low will form over the
four corners region. As the low slowly moves east-northeast, our
CWA will remain in a deformation zone which will allow more
showers and thunderstorms to form this afternoon and evening.
Models in good agreement that most convection will take place from
the Roan/Tavaputs/Bookcliffs southward where the best forcing will
take place. Speaking of forcing, a weak 50kt jet will move over
southern areas along with plenty of upper level divergence so the
ingredients do look to be in place for a rather active day. Again,
biggest concerns will be heavy rainers and gusty outflow winds of
40 to 50 MPH under the strongest storms. Some small hail is also
possible.

Before that happens though, the HRRR and RAP are indicating some
precip starting over southeastern Utah as early as daybreak this
morning which does match up with a rather potent vort max that is
progged to move over the same region. Morning shift will need to
keep an eye on this possible development especially considering
the convective activity currently occurring over southwestern
Utah. As has been the case over the last few nights, some
overnight showers and storms will persist but coverage will be
minimal. Temperatures will continue to run a bit below normal.

Sunday, the closed low will move across southern portions of our
CWA. The difference from Saturday will be that the upper level
support will have shifted well to our east which will keep forcing
in check. The models still indicate convection but coverage will
be less as will storm intensity. Favored areas will be the
Continental Divide and the San Juans.

.LONG TERM...(Sunday night through Friday)
Issued at 235 PM MDT Fri Aug 26 2016

Latest model runs are painting a different picture than 24 hours
ago. What appeared to be a mostly dry week is now looking wetter
as a low pressure trough deepens over the western states, pushing
the ridge of high pressure eastward over the central Plains
states. This will allow for a more favorable southerly flow of
moisture, with PW values increasing to 0.75 and above on Tuesday
and over an inch values by Thursday through the end of the week.
This plume looks to remain over us with our CWA in the favored
right entrance region of the upper level jet. Some embedded
shortwaves move through the base of the trough from time to time,
with the strongest shortwave on Thursday, coinciding with the
better push of moisture. Expect storm activity to increase through
the middle to latter half of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1020 AM MDT Sat Aug 27 2016

Showers and thunderstorms will again develop over the area today
ahead of an upper level disturbance that will shift over the four
corners by this evening. Southwest CO and southeast UT will be
favored for the most extensive coverage of convection. However all
areas, and especially the mountains, may also see storms this
afternoon/evening. VFR will be the rule but some storms may drop
flight conditions to MVFR briefly. Expect convection to fire from
18Z onwards with most coverage from 21Z through 03Z as has been
the case over the last few days. A few showers and storms will
persist overnight but shouldn`t pose any threats to TAF sites.

&&

.GJT Watches/Warnings/Advisories...
CO...None.
UT...None.
&&

$$

SHORT TERM...TGR
LONG TERM...MDA
AVIATION...EH


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