Area Forecast Discussion
Issued by NWS Grand Junction, CO

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763
FXUS65 KGJT 111113
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
413 AM MST Sun Dec 11 2016

.SHORT TERM...(Today through Monday)
Issued at 413 AM MST Sun Dec 11 2016

Active morning underway with widespread rain and snow rolling
through the region. Heavy snow observed on area webcams along and
north of Interstate 70 with the heaviest snow falling in the
vicinity of Rabbit Ears Pass near Steamboat Springs.

Deep plume of Pacific moisture riding nose of strong h3 jet
pushing through this morning just a tad bit slower than earlier
thinking. However, radar is very active with cells moving rapidly
east at 30 to 40 mph. Mild nature of the system keeping temps
fairly uniform with most areas running in the 25 to 35 degree F
range. As a result, still dealing with some rain issues up to as
high as 7000 feet with Eagle still sitting in the mid 30s and
flipping between rain and snow. Column will continue to cool and
still anticipate Eagle flipping over to all snow this morning with
several inches of snow still possible. Impacts along the
Interstate 70 corridor are expected from the Glenwood Canyon
eastward and current winter weather advisory will remain in
effect. Craig and Meeker have remained all snow overnight with
a few inches of wet snow on the ground. Also seeing a bit more
activity across our southern zones this morning, although
accumulations have been light so far per webcams and spotter
reports. Overall, storm remains on track with earlier thinking and
will keep all highlights as is.

HiRes models in good agreement with the rain and snow ending by
midday over all but the northern mountains in western Colorado
where favorable orographics will continue. This correlates well
with the drying in water vapor that will be working across
northern utah and into our region by midday. Partial clearing
overnight will allow some valley fog to develop by Monday morning
with a few snow showers lingering over the northern mountains.
Monday is expected to be a slower weather day as we wait for the
next system, due in sometime Tuesday.

Temperatures will remain on the "mild" side for this time of year
or near normal through Monday.

.LONG TERM...(Monday night through Saturday)
Issued at 413 AM MST Sun Dec 11 2016

Our next significant weather-maker for eastern Utah and Western
Colorado comes later on Tuesday. Medium-range guidance is in good
agreement on a closed low at 500mb diving south off the coast of
British Columbia on Tuesday afternoon. As it does so, renewed
Pacific moisture will surge east along the California coast and
into the central Rockies. The central and northern mountains
should see another round of snowfall from early Wednesday morning
through Thursday morning. Given the Pacific airmass in place and
west to southwesterly flow ahead of this system, the Wednesday
event will share some similarities to the current weekend storm
with regard to concerns over snow level and precipitation type in
valley locations.

Beyond the Wednesday system, substantial differences in medium-
range guidance evolve. The ECMWF merges the closed-low at 500mb
into the mean western longwave trough, resulting in a quick-moving
shortwave traversing the Four-Corners region on Friday. The GFS
keeps the 500mb low cut-off and digs a much deeper trough into the
California coast. As a result a much slower solution is depicted
with warm southwest flow overspreading the region Friday morning,
and significant precipitation lingering through the first half of
next weekend. With such dramatic differences in the evolution of
the western trough, confidence remains quite low in the forecast
after midweek.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 413 AM MST Sun Dec 11 2016

Widespread rain and snow will continue this morning with showers
tapering off from west to east this afternoon. CIGS will remain at
or below ILS break points at most sites with areas of mvfr and ifr
CIGS/VSBY associated with the rain and snow. Conditions slowly
improve after 19z with VFR conds returning to the lower valley sites,
spreading into the central and eastern sites by this evening. VFR
conditions expected overnight at all sites, although patchy valley
fog may develop in valleys that experienced widespread
precipitation. Mountains will remain obscured through 20z this
afternoon, before CIGS start lifting. &&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Storm Warning until 6 PM MST this evening for COZ004-009-
     010-012-013.

     Winter Weather Advisory until noon MST today for COZ002-003-005-
     008.

UT...None.
&&

$$

SHORT TERM...JDC
LONG TERM...MAC/JDC
AVIATION...JDC



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