Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 222135

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

.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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1153 AM MDT Sat Jul 22 2017

Moisture was being driven to the south today confining showers and
thunderstorms to the central and southern mountains of Colorado
primarily. Consequently, expect all TAF sites with the exception
of KTEX and KDRO will have CIGS above ILS breakpoints and VFR
conditions. Thunderstorms already starting over the San Juan
Mountains and it`s likely the KTEX will experience thunderstorms
with heavy rain resulting in brief MVFR visibility. There is a
good chance that northerly flow will carry cells from the San
Juans over KDRO later this afternoon into early evening. Quiet
weather will return after 03Z and will continue through noon


CO...Flash Flood Watch until 9 PM MDT this evening for COZ019.



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