Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 280519
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1119 PM MDT Mon Jun 27 2022

.SHORT TERM...(Tonight through Tuesday night)
Issued at 248 PM MDT Mon Jun 27 2022

Satellite imagery is indicative of the environment and pattern
that we are currently under as storms were quick to fire shortly
after noon across most higher terrain, particularly the Tavaputs
and Roan Plateau as well as the La Sals and Uncompahgre Plateau.
The San Juans were a bit late to fire but storms are firing on the
southern slopes there as well. Storm motion appears light but
overall trajectory is northwest to southeast, indicative of the
high pressure ridge positioned to our west over the Great Basin.
PWAT on the 12Z morning GJT sounding is a respectable 0.82 inches
with about 850 J/kg of DCAPE. There is still plenty of moisture to
work with so anticipate some of these storms to be capable of some
brief moderate to heavy rain. Storms will largely favor the high
terrain as storm motion is weak but slowly drift off the high
terrain into adjacent lower valleys to the southeast of those
buildups by late afternoon into the evening, capable of gusty
outflow winds in addition to brief moderate rain. There is less
moisture than last few days though, as the monsoonal tap has been
cut off with the westward movement of the ridge. Most favorable
location for heavy rain appears to be the southern mountains and
valleys though today where the best moisture remains as models
indicate PWAT near or slightly above an inch. Otherwise, partly
sunny skies will result with warm temperatures near or slightly
below normal today.

Conditions dry out even further on Tuesday for more of a downturn
in afternoon convection as PWATS lower to 0.7 inches or less
across much of the area, especially the northern and central
portions. The best moisture still remains to the south across the
Four Corners with PWAT in that 0.8 to 1.0 inch range. A low
pressure trough does move into the Pacific Northwest on Tuesday,
trying to help force this ridge further east, so the ridge of high
pressure will essentially flatten and move overhead, resulting in
this downturn in convection with exception of southwest Colorado.
Enough nudging will take place though with several shortwaves
ejecting from this Pacific NW trough, for a more favorable return
to monsoonal moisture mid to late week. More details on this in
the Long Term discussion below. Temperatures on Tuesday look to
stay warm with highs bumping up to a few degrees above normal.

.LONG TERM...(Wednesday through Monday)
Issued at 248 PM MDT Mon Jun 27 2022

High pressure sets up over the Four Corners early Wednesday which is
effective in drawing up low level moisture off the Gulf of
California and the Sonoran Desert into Arizona, Utah and finally the
central and northern parts of Western Colorado. It may seem a
roundabout route, but it is the path of least resistance to move
this low level moisture in north of the San Juans. This deeper
moisture is key to increasing the PWAT and developing more wide
spread storm coverage producing heavy rain. Look for widely
scattered showers and thunderstorms over the higher terrain of
eastern Utah and Western Colorado with isolated storms drifting
over the lower valleys. These storms will last into the evening
with some, mostly over the higher terrain to lasting overnight
into Thursday.

The high will slowly drift southeast across New Mexico toward West
Texas Thursday continuing to pull the deep moisture up through
Arizona into eastern Utah and western Colorado to increase the
coverage to widespread showers and thunderstorms over the higher
terrain and scattered storms in the lower valleys. By Friday, a
trough starts descending south along the Pacific Coast, increasing
the southwest flow into the region and entraining dryer air into
flow in the western half of the region. This will decrease the
convective activity from west to east across the region with
isolated storm to the west, scattered storms over the higher
terrain from the Park Range to the north to the Uncompahgre
Plateau and western San Juans to the south, and widespread storms
along the Divide and to the east.

Beyond Friday and Saturday, forecast confidence fall significantly in
that model solutions tend to diverge, and that we`re talking about
Summer weather patterns that tend to be nominally weak leading to
significant impacts due to the slightest perturbation. That being
said, in the longer range, the models are tending to stall the
trough off the coast setting up a fairly stable pressure gradient
pointing at a high parked over the Southern Plains States, thereby
producing a strong southerly monsoonal flow of moisture up through
Arizona and New Mexico into the region Sunday and into the next
week. This could lead to a period of possible heavy rain showers and
strong thunderstorms across the region, definitely something to keep
an eye on.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1118 PM MDT Mon Jun 27 2022

VFR conditions will prevail through the period. Some scattered
showers will develop over the southern mountains again this
afternoon. Gusty winds, lightning and ILS ceilings can be expected
within showers at some of the sites. Brief MVFR could be possible.

&&

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

$$

SHORT TERM...MDA
LONG TERM...DB
AVIATION...TGJT


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