Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 230539
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1139 PM MDT Sat Jul 22 2017

Updated aviation section

.UPDATE...
Issued at 831 PM MDT Sat Jul 22 2017

Made some slight changes to the SW Colorado and SE Utah
precipitation forecast...bringing probability of precipitation
down during the overnight hours on Sunday night.

&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 323 PM MDT Sat Jul 22 2017

Drier air continues to move over eastern UT and western CO from the
north. Deepest moisture is over far southeastern UT and southwestern
CO. A weak shear axis over southwestern CO along with heating and
orographics have produced slow moving showers and thunderstorms over
and near the southwestern San Juan Mountains. Some of theses
storms could produce heavy rainfall.

The dry air continues to push south and should reach the southern
border of our forecast area by mid evening. Expect a downturn in
activity compared to the last few days as this drier mid level air
moves overhead. For Sunday afternoon and early evening isolated
showers and thunderstorms over the higher terrain will be possible
due to the lingering moisture and day time heating.

.LONG TERM...(Monday through Saturday)
Issued at 323 PM MDT Sat Jul 22 2017

The upper ridge axis starts to slide east Monday. The latest
models have a weak disturbance moving into the Four Corners during
the afternoon or evening. This could open the door for deeper
moisture and upper level support for development of storms with
heavy rainfall. Will have to watch for this feature in the next
few model runs for consistency. The ridge continues east into the
plains and allows the next moisture surge to push northward. After
only a day to day and a half the models now want to build the
ridge back over the Four Corners which would allow convective
activity from lingering moisture but keep the tap to the deeper
moisture south and east. If this scenario develops there would be
another down turn in thunderstorm activity the end of next week.
Would like to see a few more model runs to gain better confidence.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1139 PM MDT Sat Jul 22 2017

Conditions will dry overnight and bring downslope/upslope winds
over the next 24 hours. Showers and tstorms will develop again
over the San Juans around 18z Sunday...confined mainly to the San
Juans and Four Corners regions.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

UPDATE...JAM
SHORT TERM...AS
LONG TERM...AS
AVIATION...JAM



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