Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 250810

Area Forecast Discussion
National Weather Service Grand Junction CO
210 AM MDT MON JUL 25 2016

.SHORT TERM...(Today through Tuesday)
Issued at 210 AM MDT Mon Jul 25 2016

High pressure will continue to slowly shift westward with drier
air continuing to infiltrate from the northwest as indicated by
SPC mesoanalysis precipitable water (PW) progs. A 55 kt jet
streak will remain positioned across northeast Utah and northwest
Colorado, providing some support for storm development for areas
along the bookcliffs and south of I-70 this afternoon and evening.
Enough moisture remains with PW values above 0.75 inches across
southeast Utah and southwest Colorado. Expect storms to develop
mainly over the higher terrain with some isolated coverage into
adjacent valleys. Models show a weak shortwave moving through
which may provide needed forcing to keep activity going overnight.
Expect this overnight activity to be fairly isolated in coverage
however given the trend of the last couple days. PW values are
less than 0.5 inches north of the bookcliffs so not expecting much
storm activity in this area. Storms will be capable of gusty
outflow winds to 25 mph, frequent lightning and brief heavy rain.

On Tuesday, the upper level trough responsible for the jet streak
over NE Utah and NW Colorado the last few days finally moves
across the region. This will allow for storms to develop Tuesday
afternoon once again over areas mainly south of I-70 with
sufficient PW values around 0.75 inches and near an inch nosing
into the Four Corners region but largely staying south of the
border in Arizona and New Mexico. The GFS is drier than the NAM
which makes sense given the much drier northwest flow moving in
behind the trough with the high pressure center shifting further
westward over the Great Basin. This should help put an end to
storm activity shortly after sunset as drier air and subsidence
move in behind the upper level shortwave trough.

.LONG TERM...(Tuesday night through Sunday)
Issued at 210 AM MDT Mon Jul 25 2016

High pressure will gradually shift westward over the Great Basin
over the next week with some deviations in the flow. Weak waves
will pass at times as the upper level jet fluctuates. Drier
conditions are expected to develop Wednesday through Friday with
temperatures increasing to about 10 degrees above normal during
this time. 100 degrees will not be uncommon across the desert
valleys with mountain locations pushing into the upper 70s and low
80s for max temps. The threat of afternoon storm development should
be mainly in the San Juans and across the central Divide from
Wednesday onward but remain very isolated in coverage.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 210 AM MDT Mon Jul 25 2016

VFR conditions will prevail at all TAF sites for the next 24
hours as drier air moving into the region brings a downturn in
thunderstorm coverage. Storms are expected to develop after 18z
Monday with gusty erratic outflow winds the primary concern. Some
brief heavy rain may occur with the stronger storms but not
expected to have a big impact on TAF sites. Some isolated storms
could persist beyond sunset.


.GJT Watches/Warnings/Advisories...


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