Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 272356
AFDGJT

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

UPDATE...
Issued at 550 PM MDT Thu Apr 27 2017

A quick burst of some snow and rain will occur over the central
mountains over the next hour or two as a line moves through. After
this happens, a downturn is expected with a few stray showers
possible. Outside of this line, significant accumulation looks to
have ended so will allow the West Elks to expire and will cancel
zone 10. Roads look wet all the way up to Vail Pass so do not
anticipate many impacts there. Will keep the northern mountains
going as favorable orographics are still in place.

.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 00Z TAFS through 00Z Friday evening)
Issued at 544 PM MDT Thu Apr 27 2017

Some rain and snow showers continue at this hour but should
lighten up as the night progresses. A few stray showers are
possible but coverage should be much less than seen this
afternoon. The gusty winds of 30 to 40 mph will also lessen over
the next few hours as the atmosphere decouples. Broken to overcast
ceilings will be common for the next 24 hours though VFR should
remain predominant. Some brief MVFR is still possible, especially
for the mountain TAF sites, but expect most ceilings to remain
just above 3K feet there.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

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

UT...None. &&

$$

SHORT TERM...MMS
LONG TERM...MMS
AVIATION...TGR



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