Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 241443

Area Forecast Discussion
National Weather Service Grand Junction CO
843 AM MDT SAT SEP 24 2016

Issued at 842 AM MDT Sat Sep 24 2016

Looking at webcams, Highway 65 over the Grand Mesa near Skyway
showing snow accumulating on the roads with snow continuing to
fall. Radar and IR Satellite indicate enhancement and snow bands
over this area moving southeastward. This looks to continue over
the next couple hours so decided to include COZ009 in the Winter
Weather Advisory until 11 am. Independence Pass and Vail Pass
currently look dry with rain and wet roads at Aspen and Vail. Will
continue to monitor this area for potential inclusion but
thinking that roads will remain wet with little impact by the time
these showers arrive to the central mountains along the divide.

UPDATE Issued at 741 AM MDT Sat Sep 24 2016

Lowered max temps for today as guidance has come in much cooler
than forecast. This seems reasonable given the precipitation and
clouds associated with the low pressure system spinning over
south-central Wyoming, bringing a colder air mass into the region.
Light snow was seen falling on webcams over the eastern Uintas in
northeast Utah as well as over Rabbit Ears Pass in northwest
Colorado. A couple inches look to have accumulated on the grass
near Rabbit Ears Pass with a dusting in northeast Utah. Not too
much impact on the roads as they remain fairly wet with maybe a
few slick spots over Rabbit Ears. Mountain snotel observation
sites are not indicating too much snow accumulation with maybe a
couple inches at a few of the sites in the northern mountains
where temps are below freezing. Otherwise temps seem to be
hovering right around or slightly above freezing at most snotel
sites. Will let current advisories continue this morning as the
low continues to make its push eastward. Radar and IR satellite
this morning is showing enhancement over northeast Utah and
northwest Colorado, extending into west central Colorado along the
I-70 corridor. Rain is occurring underneath this area of
enhancement with snow limited to the mountain passes and higher
peaks. Increased and expanded area of cloud cover and pops this
morning through early afternoon as a result.


.SHORT TERM...(Tonight through Sunday night)
Issued at 314 AM MDT Sat Sep 24 2016

The current satellite water vapor image continues to show a strong
storm system centered over Southwestern Wyoming this morning. This
storm system is still supporting showers over portions of Eastern
Utah and Western Colorado. The current IR satellite image is
showing enhanced cloud activity entering Eastern Utah and
Northwestern Colorado as a portion of the jet stream begins to
pass over the area.

The 0000Z runs of the NAM12, GFS20 and ECMWF have initialized well
with this storm system and slowly slide it to the east northeast
today with the center reaching Southwestern North Dakota by this
evening. High pressure will then begin to build in over the Great
Basin and Rocky Mountain states on Sunday.

In the meantime the lingering storm system will provide showers
across the area this morning with potential thunderstorms this
afternoon as the low ejects to the northeast. Cold air filling
into the area has also lowered snow levels down to between 8000
and 9000 feet which will support high elevation snow. An early
season Winter Weather Advisory is in place for portions of
Northeastern Utah and Northwestern Colorado through this morning.
Additionally, today will be chilly with afternoon high
temperatures only reaching into the mid 60s to lower 70s in the
valleys and low to mid 40s in the mountains.

.LONG TERM...(Sunday through Friday)
Issued at 324 PM MDT Fri Sep 23 2016

Dry weather is expected to return to the forecast area Sunday and
Monday. The storm which brought wind, heavy rain, and mountain
snow splits Saturday night with the bulk of the energy moving to
the northeast. However, a portion of the jet digs southward
carving out a closed low over central New Mexico. The moisture
wrapped system to the south will retrograde west-southwestward
across northern Mexico to the Gulf of California by Monday
evening. During this period, a dry northeast flow Sunday will
give way to dry easterlies on Monday. Forecast highs Sunday will
remain below average, though temperate in the valleys with cool,
crisp fall conditions in the mountains. Continued sunshine on
Monday will bring afternoon temperatures back to near normal

From Monday night into Tuesday the closed low will move from the
northern Baja region to southwest Arizona. Models indicated a
weak lobe of vorticity moving northward along the eastern edge of
the low could bring some light showers to the San Juan Mountains
during the afternoon/early evening. Chances improve Tuesday and
Tuesday night as the low lifts across Arizona and becomes
entrained in the prevailing continental flow. Confidence is very
good up to this point as both the ECMWF and GFS were in solid
agreement. However, Thursday`s weather is less clear as the GFS
becomes more progressive and dryer, in stark contrast to the ECMWF
which indicated showery and cool conditions will persist. Given
model differences am forced to accept the blended solution which
features a little of both. By Friday however, both models were
back in agreement over eastern Utah and western Colorado with
moisture in southwest flow feeding localized moist convection
during the afternoon. Except for some cooling Wednesday resulting
from cloudy/showery conditions in response to the passage of the
low, temperatures are expected to hover right around normal for
the last days of September.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 524 AM MDT Sat Sep 24 2016

A strong storm system remains centered over southern Wyoming this
morning, supporting showers from roughly Montrose and north.
Expect light rain to transition to showers later this morning in
the Vernal area. Less active weather is expected in southern
portions of the forecast area with Canyon lands and Durango
expected to have fair weather all day.


.GJT Watches/Warnings/Advisories...
CO...Winter Weather Advisory until 11 AM MDT this morning for COZ004-

UT...Winter Weather Advisory until 9 AM MDT this morning for UTZ023.



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