Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 302048
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
248 PM MDT Thu Jun 30 2022

.SHORT TERM...(Tonight through Friday night)
Issued at 248 PM MDT Thu Jun 30 2022

We are currently under a substantial Southwest Monsoon fetch of
moisture, with precipitable water values 0.80 to 1.00 inch, or
around 200 percent of normal, and lower elevation surface
dewpoints in the mid 40s to mid 50s. The clouds and showers that
moved across the I-70 corridor through early afternoon have
stabilized that region, but to the north, south and west, MUCAPES
of 500-1000 J/kg and ample deep layer shear have resulted in
conditions favorable for deep and organized convection. We`ve
already had a strong to potentially severe thunderstorm near
Flaming Gorge in northeast UT. Weak shortwaves in the
southwesterly flow aloft and effects of being under the right
entrance of a strong jet aloft over northern high plains will help
to sustain afternoon convection well into the overnight hours.
However, as these features loose their influence on the region
overnight, shower activity is expected to diminish quite a bit.

The upper level pattern changes little Friday with a flat
Southern Plains ridge and an upper level trough off the West Coast
continuing to feed subtropical moisture over our region.
Precipitable water values do decrease a notch, but fairly good
coverage of showers and thunderstorms is expected again,
especially over the mountains. Steering flow is high enough to
decrease the likelihood of flash flooding, but we will still
remain vigilant for training storms or any direct impact on burn
scars from high rainfall rates. The usual decrease in coverage is
expected Friday night. Temperatures Friday will be near to
slightly below normal.

.LONG TERM...(Saturday through Thursday)
Issued at 248 PM MDT Thu Jun 30 2022

A strong upper level trough will move over the West Coast this
weekend and temporarily shift the southern U.S. upper level ridge
eastward. Long range ensemble models agree on that trough
weakening early next week and retrograding as heights rise across
the the Four Corners. There is also agreement in the precipitable
water remaining well above normal over the entire region through
the weekend, then drying out to near normal across northeast UT
and northwest CO from early to the middle of next week. Southern
areas look to remain under above normal moisture through the
coming week. The result is a continuation of daily shower and
thunderstorm activity, favoring the higher terrain and especially
the central and southern mountains. Daily details will have to be
resolved closer in time as we decipher the mesoscale features
embedded in the synoptic flow. Temperatures near normal this
weekend will slowly climb above normal next week.

Ensemble model agreement of a large 597 to 600 DAM upper level
ridge building directly over CO next weekend increases confidence
in a period of a drier regime and well-above normal temperatures
(triple digits for lower elevations).

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1115 AM MDT Thu Jun 30 2022

Deep monsoonal moisture combined with instability and shear create
an environment favorable for thunderstorms this afternoon.
Lightning activity near and south of the I-70 corridor is expected
to become widespread, with VCTS at nearly every TAF site through
this evening. Strong cells may result in brief MVFR visibility,
with ceilings below ILS breakpoints for some TAF sites. In
addition, expect strong gusts 20 to 30 kts near passing storms.
Conditions improve after 0600 UTC tonight, however, another round
of isolated to scattered convection is expected to redevelop
Friday afternoon.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Flash Flood Watch until 8 PM MDT this evening for COZ008-010-013.

UT...Flood Watch until 10 PM MDT this evening for UTZ022-027>029.

&&

$$

SHORT TERM...BM
LONG TERM...BM
AVIATION...ERW/TGJT


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