Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 210500
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1100 PM MDT WED JUL 20 2016

.SHORT TERM...(Tonight through Thursday night)
Issued at 315 PM MDT Wed Jul 20 2016

SPC mesoscale analysis shows 1.1 inches of precipitable water over
southeast Utah this afternoon, and this looks to remain in place.
But instability is only weak to moderate and shear is weak.
Therefore storms will remain disorganized and short lived this
afternoon and evening. Still an occasional storm will be able to
tap into this deep moisture. For instance, Meeker received 0.32
inches in less than 30 minutes this early afternoon, and
mudslides were reported along Highway 145 between Placerville and
Telluride due to locally heavy rains.

A disturbance we have been watching was over southern Utah this
afternoon but has not yet interacted with the deeper moisture in
SE Utah. This is still be expected to have better storm coverage
into the evening. The other area is in NW Colorado where there is
some favored precipitable water gradient (diminishing towards the
Wyoming border). Synoptic models are not picking up on this so
have raised POPs there this afternoon and evening. Storm
environment: storm motion is to the NE at 10-15 mph, >= 50 dBZ may
produce small hail in higher elevations. Training of storms can
potentially lead to localized flooding issues.

Tonight no forcing is seen so storms should be isolated or less in
coverage later midnight. Thursday and Thursday night should be a
general repeat of scattered mountain and isolated valley storms
centered on the afternoon and evening.

.LONG TERM...(Friday through Wednesday)
Issued at 330 PM MDT Wed Jul 20 2016

Friday, the moist SW flow continues with precipitable water
values remaining around 1.1 inches in the lower elevations of
southeastern Utah and far western Colorado. A persistent forecast
continues for now.

By Saturday, the large scale pattern change begins. The Pacific
NW upper Low ejects through the northern Rockies. This turns the
upper flow from SW to a drier west. The subtropical High also
expands across the southern tier of states into the SE Pacific.
All of this brings a drying and warming trend to the forecast area
that continues into at least next Wednesday. The latest trend is
for marginal moisture to linger over the southern and central
zones for some late-day, mainly-mountain storms. The northern
zones see a return to dry and breezy conditions that may raise
fire weather concerns.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1100 PM MDT Wed Jul 20 2016

Thunderstorms have diminished over most of the forecast area this
evening. However, at 05Z scattered storms were still persisting
over the San Juan and Abajo mountains and southward, and in the
north from far northeast UT to the Flat Tops mountains and
northward. These storms are also expected to diminish during the
next couple of hours, but isolated late night and early morning
will be possible. Thunderstorms will again increase in coverage
and intensity after 18z Thursday...initially over the higher
terrain. Local MVFR/IFR will be possible in the heavier showers. A
decreasing trend will again take place after 03Z Thu evening.

&&

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

$$

SHORT TERM...Joe
LONG TERM...Joe
AVIATION...EH


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