Area Forecast Discussion
Issued by NWS Grand Junction, CO

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323
FXUS65 KGJT 300058
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
658 PM MDT Sat Apr 29 2017

.UPDATE...
Issued at 650 PM MDT Sat Apr 29 2017

Clouds are slowly fading across western portions of the CWA this
evening and temperatures are beginning to slowly decrease. Once
the sun goes down and more of the clouds dissipate temperatures
should begin to fall more rapidly over eastern Utah and western
Colorado. High resolution short range forecast models are
indicating that temperatures will indeed fall to near freezing in
the Grand Valley overnight, with the coldest temperatures
occurring at or around sunrise Sunday morning. Therefore, we have
upgraded the Freeze Watch for Colorado zone 6 to a Freeze Warning
which is in effect through 9 am MDT Sunday morning. For more
information please visit our web page at www.weather.gov/gjt or
see the Freeze Warning message DENNPWGJT.


&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 231 PM MDT Sat Apr 29 2017

An upper-level low pressure system continues to drift slowly south
and east through the southern Rockies this Saturday afternoon.
While much of the precipitation associated with this system has
remained east of the Continental Divide, some mid-level moisture
has managed to drain west of the Front Range. Light stratiform
snowfall continues over the Gore, Sawatch, and Elk Ranges, with a
more showery convective snowfall occasionally falling across
higher elevations on the Grand Mesa, Uncompahgre, and San Juans.
Occasional breaks in cloud cover will continue to fuel these light
snow showers through the afternoon and evening before surface
heating and resultant shallow instability rapidly diminishes after
sunset. Combined with a continued southward drift of the overall
storm system, cloud cover is expected to decrease from west to
east overnight. Freeze warning has been issued for the Delta-
Montrose corridor where confidence is high in sub-freezing
temperatures for several hours overnight. Farther north in the
Grand Valley, early evening cloud cover may hold temperatures high
enough to avoid a hard freeze. Will monitor cloud cover and
temperature trends for a possible Freeze Warning in this zone as
well.

Sunday will feature rising heights with light northerly flow
across eastern Utah and western Colorado. Guidance dries out the
mountains pretty well - however can not entirely rule out a stray
snow shower especially in central Colorado ranges. Afternoon high
temperatures will run 5 to 10 degrees below normal across the
western slope.

By Sunday night, a weak disturbance will round the eastern side of
a ridge of high pressure centered over the west coast. The main
impact for our region will be an uptick in cloud cover on Sunday
night into Monday morning. While lower levels will remain dry, an
increase in mid and upper-level moisture will result in some light
snow for the northern mountains starting before midnight Monday.

.LONG TERM...(Monday through Saturday)
Issued at 231 PM MDT Sat Apr 29 2017

Light snow will linger through the day on Monday in the mountains
along and north of I-70 as a subtle trough dives southward through
the Rockies. Once again, precipitation will fall only in the
higher elevations with a partly cloudy day expected elsewhere.
Another shortwave will pass late on Tuesday into Wednesday.
Forecast guidance has trended a bit stronger with this system in
today`s 12z runs, and some higher PoPs have been added to much of
central and northern Colorado and eastern Utah. Exact QPF totals
still vary greatly, but a mean of available guidance suggests
possible advisory-level snows at least for the Flat Tops and Park
Range by Wednesday morning.

This storm system exits the region quickly Wednesday afternoon and
evening with high pressure building in from the west. The second
half of the week will feature a return of springtime warmth as a
large upper-level ridge builds in from the west. Ensemble guidance
has been in good agreement over the past few days showing this
ridge moving in, and today`s GEFS and EPS solutions are no
exception showing +1 to +2 sigma h5 heights by Friday morning.
Valley temperatures in eastern Utah and western Colorado will
return to near the 80 degree mark by Thursday and Friday. Dry
weather is expected from Wednesday night through the first half of
next weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 554 PM MDT Sat Apr 29 2017

Mid and high clouds continue to wrap into the Western Slope as a
low pressure system centered over Northeast New Mexico continues
to slowly slide east. Primarily VFR cigs between 5,000 and 10,000
feet will prevail through midnight before clearing out. MVFR-IFR
conditions are anticipated in the vicinity of Telluride with
periods of snow possible through the overnight hours and possible
thundersnow through the next 2 hours. Dry northerly flow is
beginning to work its way into Eastern Utah providing the Uintah
Basin Grand Flat areas with VFR conditions through the next 24
hours.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Freeze Warning until 9 AM MDT Sunday for COZ006-011.

UT...None.
&&

$$

UPDATE...Larry
SHORT TERM...MAC
LONG TERM...MAC
AVIATION...Larry



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