Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 171118
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
418 AM MST Fri Nov 17 2017

.SHORT TERM...(Today through Saturday)
Issued at 417 AM MST Fri Nov 17 2017

The storm is underway this morning but overall it seem to be
under- performing in the snowfall production so far. PWAT has
almost doubled since 24 hours ago...but most of this moisture is
aoa 650mb...so top down saturation still need a bit more ascent.
That should be occurring with the jet streams merging overhead.
Models still favoring the central mountains for the highest QPF
and forecast is still built that way. Two things are troublesome
this morning however. Very warm temperatures...due in some part to
the second challenge...wind. Mixing has kept lows from dipping
below 50 over many areas including the NW plateau country and the
Colorado and lower Gunnison River Valleys. Gusts to 40 mph already
occurring in some areas and though this may relax a bit through
the morning...it should pick up as the upstream cold front
approaches. Guidance also suggest very windy conditions with the
fropa as winds turn west then northwest. Short term models show a
very distinct pressure gradient couplet by late afternoon with
strong CAA to our west and warm temperatures overhead. As for
precipitation a passing wave with the jet couplet aloft should
lead to the anticipated uptick through the morning...then we see
some of a downturn with convection driving much of the action. One
of the reason thunder has been added to the forecast. The front
should reach roll through NE Utah by mid day with cold air
spilling into NW Colorado by mid afternoon before accelerating
southward by sunset. Expect strong gusts and some organized storms
along the front late this afternoon and evening. Should get
exciting. Cold air and the forcing with the fropa should also help
some for some better snow accumulation before the drier air eats
away and the dendritic layer and we clear out by sunrise. Much
cooler conditions move in for Saturday with highs some 15 to 25
degrees cooler.

.LONG TERM...(Saturday night through Thursday)
Issued at 417 AM MST Fri Nov 17 2017

By sunset Saturday a ridge building over the Great Basin will be
in controll of the weather over the forecast area. Dry northwest
flow aloft will dominate and the clear skies at night will produce
cold lows 3 to 6 degrees below normal and cool daytime highs near
or just below normal. A slow warming trend will continue Sunday.

A minor shortwave trough will cut through the northern half of the
area Monday night and early Tuesday morning. Then a stronger
ridge will keep the weather dry through Thursday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 417 AM MST Fri Nov 17 2017

Winds will be one of the major concerns to aviation today as
strong southerly winds with gusts over 40 mph occur ahead of an
approaching cold front. Winds could gust 50 to 60 with the passing
front as winds turn northwest. Lightning and some sleet or small
hail may also accompany the frontal passage. Strong winds aloft
will also lead to turbulence along the ridgetops. VFR conditions
will gradually deteriorate at the mountain terminals as the
precipitation becomes more widespread. MVFR to IFR can be expected
at times in the heavier showers due to low cigs and vsby. The
worse conditions will be near the front with rapid improvement
expected behind the front through the late evening to early
morning hours. VFR should dominate the forecast by sunrise.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Wind Advisory until 9 PM MST this evening for COZ001-002.

     Winter Weather Advisory until 5 AM MST Saturday for COZ018-019.

     Winter Storm Warning until 5 AM MST Saturday for COZ004-009-010-
     012-013.

     Wind Advisory from 10 AM this morning to 9 PM MST this evening
     for COZ006>008-011-014.

UT...Wind Advisory until 9 PM MST this evening for UTZ022-027-029.

&&

$$

SHORT TERM...15
LONG TERM...CC
AVIATION...TGJT



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