Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 271748

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1148 AM MDT Sat May 27 2017

Issued at 1148 AM MDT Sat May 27 2017

Quick update to PoPs to account for drier air this afternoon.
Convection has begun and expect a strike or two of lightning to
begin at any point along the Gunnison to Aspen corridor just ahead
of where the front is located. A few isolated showers and tstorms
are possible behind the front, but much drier air will be moving
into the region and allow for shallow cumulus development.


.SHORT TERM...(Today through Sunday)
Issued at 332 AM MDT Sat May 27 2017

Interesting morning on satellite with southward propagating
outflow along the southern Front Range and tightly wound
shortwave over southern Wyoming near Rock Springs. Baroclinic band
south of the wave dropping south as main h5 trough axis
progresses through the area today and tonight. This will result in
another active day in regards to the convection department. Expect
scattered to numerous showers across the northern two-thirds of
the forecast area into the early evening hours with storms capable
of producing locally heavy rainfall (with some snow possible over
the higher peaks), small hail and gusty outflow winds to 45 mph.
Cloud cover and cooler surface temps will limit deep mixing and
help to keep winds more in check near thunderstorms. Do
anticipated a little more southward progression of convection than
current models are showing with activity getting down into the
San Juans. Latest radar trends seem to support that thinking and
this could hamper some outdoor activities for a bit.

Convection is expected to diminish after sunset this evening with
drier and warmer weather moving back in on Sunday as we see
heights jump up a bit in response to the western ridge sliding
eastward behind exiting long wave trough. Temperatures will be
down a good 5 to 10 degrees across most of the forecast area today
due to cloud cover and cooler conditions aloft moving through.
Exception will be over the far southern zones where passing trough
axis will be delayed until later in the afternoon. Temps moderate
back toward normal on Sunday.

.LONG TERM...(Sunday night through Friday)
Issued at 332 AM MDT Sat May 27 2017

Rising heights in response to the western ridge of high pressure
sliding eastward will usher in a period of warmer and drier
conditions to the forecast area as we start off the new work week.
Still expected to see diurnally driven mountain convection through
Tuesday although coverage will be more isolated in nature. Big
question looms around midweek with the models still not in
agreement with approaching negatively tilted trough that swings
across the western U.S. Wednesday and Thursday. The GFS is coming
in deeper and drawing moisture back northward by mid-week,
resulting in more widespread showers and thunderstorms. The EC is
showing this trough deflecting northward and weakening as it moves
across the western U.S. with brief surge of moisture Wednesday,
with drying already moving back in by the end of the week. Leaning
toward the drier EC solution attm as we are pushing into June and
the ridge will take out some energy as the Pacific system moves
onshore. So basically, scattered mountain and isolated valley
convection for Thursday and Friday with a slight uptick around
Wednesday as both models are trying to draw moisture northward.

Temperatures will be running near seasonal normals for much of the


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1148 AM MDT Sat May 27 2017

Front is passing through the region and firing off some showers
and a few strikes of lightning. MVFR conditions possible with
heavier showers at ASE for the next hour but otherwise TAF sites
will only see a passing shower or two today. Drier air will move
in from the northwest by 00z allowing for clearing conditions
across the region.




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