Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 261630

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1030 AM MDT Tue Sep 26 2017

.SHORT TERM...(Today through Wednesday)
Issued at 433 AM MDT Tue Sep 26 2017

Today, some changes are expected as the jet stream rounds the
base of the trough that has remained to our west over the last few
days. As the jet drops down, it`ll form a closed low over
southeastern NV, northeastern AZ and southeastern CA. Cyclonic
flow around this newly formed low will allow moisture to start
streaming into the area as indicated by increased PWATs and specific
humidities. The EC and GFS bring in some showers and storms over
the San Juans and along the Continental Divide for the central
mountains this afternoon (maybe even some light snow above 11,500
feet). Of course, the NAM is downplaying any precipitation until a
more potent shortwave moves through this evening. Following the
EC/GFS`s lead with the forecast with best chances for any precip
over the southern valleys and San Juans. Precipitation chances
will increase from south to north as the evening wears on but will
remain south of the I-70 corridor.

By daybreak Wednesday, the low pressure will be over central
Arizona as the next shortwave rotates around the parent low.
Showers are expected over the San Juans in the morning with a
noticeable uptick in precipitation noon onwards. As the low
continues to move to the northeast, heavier precipitation will
start moving northward also. The heaviest precipitation looks to
fall from noon Wednesday through Thursday morning with showers and
thunderstorms possible across the southern half of the CWA before
overspreading north of I-70 in the evening. Snow levels look to
be around 11K feet or so with accumulating snow possible above
that level. In fact, three to six inches of new snow is in the
forecast with locally higher amounts possible. Will hold off
issuing any highlights for now to get another model run in before
making any decisions.

.LONG TERM...(Wednesday night through Monday)
Issued at 433 AM MDT Tue Sep 26 2017

The cutoff low over the Great Basin will be lifting slowly NNE
over eastern Utah Thursday and Friday with deep southerly flow
across most of our forecast area. This will bring widespread
showers and a few thunderstorms to the region with activity
peaking through the on Thursday. System is coming in warm with 00Z
GFS showing H7 temps climbing to +8C by 00Z Friday. However, the
NAM is coming in several degrees cooler which could lead to some
high elevation snow. Will work on those details as we get closer
to the event. This low will finally kick out over the weekend with
drier and more zonal pattern setting up.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1030 AM MDT Tue Sep 26 2017

VFR conditions are expected to remain in place over the forecast
area with some mid and high level clouds increasing this
afternoon. Some scattered showers with isolated thunderstorms are
possible over the southern mountains this afternoon with showers
becoming more widespread and spreading northward after 03Z
Wednesday through Wednesday afternoon. Light snow is possible over
the southern mountains above 11,000 feet so peaks may be obscured
at times. Showers will mainly affect KTEX and KDRO.




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