Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 212141

Area Forecast Discussion
National Weather Service Grand Junction CO
341 PM MDT Mon May 21 2018

.SHORT TERM...(Tonight through Tuesday night)
Issued at 342 PM MDT Mon May 21 2018

Satellite imagery and 12Z H500 hand analysis show a well defined
circulation in the vicinity of the southern CA/NV interface. A
southerly mid level jet induced by height falls ahead of this
system has transported a decent amount of return moisture
northward...arcing across W.New Mexico into the central High
Plains. The mid level and upper level winds are also proving to be
favorable for strong to severe storm development just to the
south of our CWA. Storms will continue to drift northward in this
moisture belt through the evening with gusty winds and lightning
the main threats...though small hail is also likely in the
stronger cells as the the -20C height is hoovering around 20kft
AGL. Expect majority of the storms to drop off the radar by
midnight as we lose most convectively driven ascent. Downvalley
winds look to be enhanced again tonight with a defined area of low
pressure over SE.Utah...this will keep temperatures on the warmer
side. The Western circulation will begin to accelerate northeast
across Nevada after sunrise tomorrow. This will nudge the
cyclonically curved jet core across our western CWA on Tuesday and
provide some good upper level ascent. Isentropic moisture
transport continues along the divide region and will aid in
reducing stability over our eastern CWA mountains through the
afternoon. Farther west there are indications of dry air aloft
limiting storm coverage. The interaction of the upper jet with the
surface low should focus some better storm coverage but models
have this coupling of features just to the west of our CWA...a
trend to watch over the next 12 to 18 hours. Storms may survive
later into Tuesday night as the jet core moves over the heart of
the CWA and lingering energy in the back of the trough filter

.LONG TERM...(Wednesday through Monday)
Issued at 342 PM MDT Mon May 21 2018

The flow aloft will dry out by mid week as the winds back a bit to
the west. Heights will be rising along with the temperature
Wednesday through the end of the week. There will be some limited shower
and storm activity popping during the heating of the day on
Wednesday but beyond this more stable conditions should leave
mainly clear skies in place to end out the week. The next upstream
system takes up a familiar location in the Intermountain West by
Saturday. This system is hung out to dry just off to our West
through early next week as a strong blocking pattern develops
downstream. Very little confidence by Day 7 but there could be
some small precipitation chances being introduced as this system
stalls to West.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1200 PM MDT Mon May 21 2018

Showers and thunderstorms will develop over the higher terrain
early this afternoon and will continue into the evening with the
San Juan Mountains and adjacent valleys favored. Showers and/or
thunderstorms are likely to impact KDRO, KGUC after 20Z,
continuing through 02Z. Those sites can expect outflow winds up
to 40 MPH, but visibility and ceilings are expected to remain in
the VFR range. Showers/thunderstorms in the vicinity of KEGE,
KRIL, KASE and KTEX may see similarly strong outflow winds as
those mentioned previously. Elsewhere, VFR conditions will
continue through the next 24 hours with no threat of CIGS falling
below ILS breakpoints.




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