Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 230231

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

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 00Z TAFS through 00Z Sunday evening)
Issued at 546 PM MDT Sat Jul 22 2017

Moisture staying confined to SE Utah and SW Colorado this evening
as expected. A couple more hours of tstorms before convection
stratifies out to some lingering showers. KTEX and KDRO the only
TAF sites expected to potentially receive some showers/tstorms
over the next few hours...and thus the only sites that may
possibly reach ILS breakpoints. 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.




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