Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 032102

Area Forecast Discussion
National Weather Service Grand Junction CO
302 PM MDT Sat Jun 3 2023

.SHORT TERM...(Tonight through Sunday night)
Issued at 157 PM MDT Sat Jun 3 2023

The forecast area is currently sitting in between two weak low
pressure systems. One is over southeast CO and the other northern
UT. They are not close enough to provide any extra lift, but since
they have blocked the flow moisture remains in place. Terrain driven
storms have already developed over the higher elevations and are
drifting to the southeast. Persistent cloud cover across the
northeast third of the area will limit storms there. The sounding
this morning revealed weak midlevel lapse rates that most likely
limited the instability as well. Moisture values are sufficient
for some brief moderate to heavy rainfall, although the lack of
shear is causing storms to quickly dissipate. Outflows will try to
focus development over some of the adjacent valleys, but overall
they may struggle to do that. Given the moisture outflows should
not be particularly strong. Most of the convection should
dissipate around sunset. Conditions tonight will be similar to
last night but a little warmer.

Tomorrow overall there is not much change. There will be some subtle
difference in the wind patterns due to minor movement of these two
systems. Flow over the Divide becomes easterly which does try to
send more moisture towards the western slope. This may result in
more convection along the Divide in the afternoon. The remainder of
the CWA will see scattered convection over the higher terrain much
like today.

.LONG TERM...(Monday through Saturday)
Issued at 157 PM MDT Sat Jun 3 2023

Forecast expectations for the long term have yielded little change
in the most recent model runs. A stubborn ridge of high pressure
forming an omega block over the Central U.S. will impose its will on
weather for most of the work week here in western Colorado and
eastern Utah. A trapped low  off southern California will continue
to supply upper level moisture to the Great Basin and weak return
moisture will likely sneak in from the Gulf of Mexico during the
period. This should produce a pattern like we`ve seen the past week
or so with daily showers and thunderstorms possible along the high
terrain, with some spilling into adjacent valleys.

Deterministic models are attempting to chip away at the blocking
high by Thursday with the SOCAL low working its way across the Great
Basin and potentially drying out the southern half of the CWA under
the southwesterly flow that will shunt the Gulf moisture eastward.
This sets up a potential wraparound regime Thursday afternoon on the
northwest side of the low, keeping much of the active weather north
of I-70 and along the Continental Divide Thursday afternoon, should
this solution hold together. Unfortunately, the stubborn blocking
high is showing some signs of halting the low in its tracks.
Spaghetti plots are inconsistent Friday, onward. A persistence
approach seems best for next weekend, as no signs of a sincere
drying of the atmosphere are coming through the models today.

Cloud cover and shower activity across the region this coming week
will spell out a general cool trend with temperatures around 5
degrees under early June normals. Shower activity will remain
scattered enough to see a few sunny areas open up long enough to
warm a few locales closer to their expected climatology. Likewise,
overnight lows will get a bump upward with higher dewpoints and
insulating cloud cover overhead.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1154 AM MDT Sat Jun 3 2023

Persistent cloudiness will continue along the continental divide
today with scattered showers and thunderstorms developing on the
high terrain of western Colorado. Gusty outflow winds, small hail,
and visibility reductions from these showers will pose aviation
challenges at mountain terminals. Valleys will likely see a few
short lived storms drift off of the terrain. Gusty outflows will
be the concern with any of these valley showers.




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