Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 121750

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1150 AM MDT Sat Aug 12 2017

Updated aviation section

.SHORT TERM...(Today through Sunday)
Issued at 314 AM MDT Sat Aug 12 2017

IR satellite showing some clouds hanging around this morning with
a few showers noticed on radar but nothing too impressive. Not
much change to going forecast as PWATs remain between .75 to 1
inch and a weak upper level jet remains above us. Some turning of
the winds can be seen at 700mb later on this afternoon indicating
a weak wave will move through the area, looking to favor northern
portions of the CWA. However, in this moist, fairly unstable
regime, convection could fire just about anywhere or form over
mountains and drift into adjacent valleys. Convection will fire
around noon with coverage increasing though the afternoon and
evening hours. Biggest concerns are the usual: dangerous lighting,
wind gusts of 40 to 50 mph, small hail, and heavy downpours from
time to time. Temps will remain right where they should be this
time of year.

Overnight, the GFS keeps our area quite active while the NAM just
about shuts all convection down. As the GFS tends to overdo
convection, started dropping PoPs after midnight through Sunday

More of the same on Sunday as another wave moves over Utah and
Colorado allowing another round of convection to fire. This trend
looks to continue through midweek before some drying kicks in as
described below.

.LONG TERM...(Sunday night through Friday)
Issued at 314 AM MDT Sat Aug 12 2017

Longwave trough digging across the western U.S. will drive the
upper level ridge over the region eastward with southwest flow
becoming established early in the week. Moisture surging northward
along the leading edge will provide the fuel for more widespread
showers and thunderstorms. Activity peaks on Monday with slow
drying trend into midweek and beyond. Should see a few stronger
storms on Tuesday as moisture gradient presses eastward and trough
moves in. Convection will be diminished beyond Tuesday with only
isolated mountain storms anticipated. Temperatures will be running
near normal through Tuesday with slowly warming expected through
the end of the week.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1150 AM MDT Sat Aug 12 2017

Afternoon thunderstorms are starting to develop over higher
terrain, and over NW Colorado. This trend will continue as storms
move west to east. An area of showers and tstorms is expected to
move from central Utah eastward this evening, bringing a
continuation of convection through the overnight hours. ILS
breakpoints will be reached at times, and potentially MVFR
temporarily in stronger storms if they target the airports.




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