Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 220255
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
755 PM MST Sat Jan 21 2017

.UPDATE...
Issued at 749 PM MST Sat Jan 21 2017

Current radar imagery shows snow moving from the northwest to
southeast this evening and continuing for the 550 corridor over
the San Juans. The warnings for those areas were supposed to fall
off at 8PM but decided to extend through midnight to account for
an additional 2 to 5 inches.

Winter Storm Watches have also been issued for the next storm that
will begin tomorrow afternoon and continue through Tuesday
morning. Another 10 to 20 inches is possible for the mountains
when all is said and done. The southern valleys also have another
chance for some good snow accumulation. Expect hazardous travel
again over mountain passes through the Sunday night through
Tuesday morning timeframe.

UPDATE Issued at 520 PM MST Sat Jan 21 2017

Still plenty of snow ongoing for much of the CWA though satellite
does show some breaking out over southeastern Utah and southern
Colorado. The warnings/advisories for those areas have been
allowed to expire. Remaining highlights continue. Next forecast
challenge turns to the next storm that looks to begin as early as
tomorrow afternoon/evening.  More to come...

&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 233 PM MST Sat Jan 21 2017

Have removed several lower elevation zones from the winter storm
products including most of SE Utah, the Paradox Valley area and
the Colorado river valley from Grand Junction to Avon as the best
push of precipitation moves northeast of these areas and temps
have risen to or above freezing, changing much of the precip to
rain. Also included with the winter storm warning all elevations
of the La Sal and Abajo mountains zone in SE Utah due to snow
reports. Satellite imagery and upper analysis show the 500 mb
trough to be splitting as it moves over northern Colorado. The
southern portion of the split will travel into New Mexico this
evening and most of the energy and moisture over western CO and
eastern UT will erode to the south and east. Current winter
weather highlights appear well timed to drop off in the south this
evening and then over the northern and central mountains
overnight.

The break between storms is well defined with dry ridging
developing over the western Great Basin. This will bring clearing
skies Sunday, then the next significant storm is developing off
the west coast. Warm advection clouds and precipitation is
projected to spread over the area late Sunday afternoon and
overnight.

.LONG TERM...(Monday through Saturday)
Issued at 233 PM MST Sat Jan 21 2017

The overall pattern Monday will shift from the warm advection
overrunning early in the day as the ridge slides east of the area.
This will be followed by cold advection aloft and at lower
levels. It appears an embedded shortwave trough will move
overhead about midday Monday, starting the transition to the next
storm, then a somewhat weak cold front is projected to slowly
drag through the area Monday afternoon. Cold advection behind the
front should kick in about 3 pm Monday afternoon behind the front.
700 mb temps in the GFS drop from around -4 to -6 C in the
Morning to -8 to -10 at sunset. Overnight 7000 mb temps lower to
-10 to -14. Precipitable water is projected to be high again with
this system. It all points to and early morning rain and snow mix
at lower elevations early Monday, transitioning to all snow by
late Monday afternoon.

The cold front should clear the forecast area to the east Monday
night, then another trough will dive into the northern Great
Basin from the north Tuesday. A cold and snowy pattern with 700 mb
temps below -15 Thru Wednesday. Anticipate more widespread winter
weather highlights for the first part of next week.

The overall pattern from Wednesday night through Saturday will
include a longwave trough over the midwest and eastern U.S. and a
strong ridge over the west coast and the Rockies.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 233 PM MST Sat Jan 21 2017

Mountains will remain obscured through tonight with some clearing
Sunday. Expect ILS cigs at all TAF sites through 12z, with periods
of MVFR and IFR in precipitation. VEL will be the first to see VFR
conditions by midnight tonight, with the other TAF sites will not
see VFR until after 18z Sunday.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until midnight MST tonight for COZ003-
     014.

     Winter Storm Warning until 6 AM MST Sunday for COZ009-010-012-
     013.

     Winter Storm Watch from Sunday evening through Tuesday morning
     for COZ003-004-009-010-012-013-017>019-022-023.

     Winter Storm Warning until midnight MST tonight for COZ017>019.

     Winter Weather Advisory until 6 AM MST Sunday for COZ004.

UT...Winter Weather Advisory until midnight MST tonight for UTZ025.

     Winter Storm Watch from Sunday afternoon through Monday evening
     for UTZ023-025-028.

&&

$$

UPDATE...TGR
SHORT TERM...CC
LONG TERM...CC
AVIATION...CC


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