Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 272156
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
356 PM MDT Thu Apr 27 2017

.SHORT TERM...(Tonight through Friday night)
Issued at 356 PM MDT Thu Apr 27 2017

A broad upper level trough remains situated over the Rocky
Mountain region this afternoon which has kept plenty of clouds and
showers hanging around the area. The cold front is almost
entirely out of our forecast area with a cold air mass settling in
its wake. The current winter highlights remain on track at the
moment with an additional few inches possible for the northern and
central mountains through this evening. While roads appear to be
just wet on webcams heavier snow showers will still have the
potential to produce blowing snow and periods of reduced
visibility.

On Friday, the amplification of a ridge of high pressure off the
west coast will finally swing the base of the trough through our
CWA. This will keep showers falling over the mountains with some
spilling into the valleys, generally for areas north of I-70.
Snowfall amounts remain below advisory criteria so will not issue
any highlights with the last leg of this storm.

In response to the cold front, overnight lows tonight will be
quite chilly with many locations dropping below freezing. The
Freeze Watches were previously upgraded to Freeze Warnings for the
central valleys where sensitive vegetation has already begun to
bloom. Freezing temperatures are again quite possible on both
Friday and Saturday night for these same locations. However,
models are not handling this series of storms well in that while
guidance shows temperatures continuing to drop, the cloud cover
is a bit trickier. If too many clouds hang around then
temperatures will moderate and perhaps not produce subfreezing
values. Therefore, will hold off on issuing any freeze highlights
for Friday night but definitely encourage later shifts to re-
evaluate.


.LONG TERM...(Saturday through Thursday)
Issued at 356 PM MDT Thu Apr 27 2017

On Saturday the storm, by now a closed upper level low, will drop
into the southern Plains, shifting shower activity to the San
Juans and along the Divide. Northwesterly flow will set up behind
the departing system and finally allow the clouds to part as we
go into the second half of the weekend and into early next week.
An exception to this will be up north where lingering moisture and
instability will keep orographic showers in the forecast through
as late as midweek.

Wednesday and beyond, high pressure will build in from the west
bringing a return to drier conditions and also near seasonal
temperatures. Extended models differ on strength and duration of
this ridge with the ECMWF being much more optimistic than the GFS
which quickly shifts the ridge east by the end of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1149 AM MDT Thu Apr 27 2017

Moisture and instability will continue to pop showers over most of
the region this afternoon. The instability will also allow
stronger winds to mix down creating gusts over 25 mph and may
impact landing and takeoff operations. VFR conditions are forecast
to prevail but the showers could quickly drop the mountain
forecast terminal conditions down to LIFR under brief moderate to
heavy precipitation snow rates. Northwest flow into the Rockies
will keep ILS conditions in place in many areas.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 6 PM MDT this evening for COZ012.

     Freeze Warning from midnight tonight to 9 AM MDT Friday for
     COZ006-011.

     Winter Storm Warning until midnight MDT tonight for COZ004-013.

     Winter Weather Advisory until midnight MDT tonight for COZ010.

UT...None.
&&

$$

SHORT TERM...MMS
LONG TERM...MMS
AVIATION...TGJT


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