Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181010

Area Forecast Discussion
National Weather Service Grand Junction CO
310 AM MST Sat Feb 18 2017

Issued at 310 AM MST Sat Feb 18 2017

Expanded the Winter Weather Advisory into the La Sal and Abajo
mountains as well as the northwest San Juan Mountains. In
addition, extended these highlights through 01Z/Sunday. Look for a
more in depth discussion within the hour.

UPDATE Issued at 931 PM MST Fri Feb 17 2017

A storm system is beginning to impact Eastern Utah and Western
Colorado this evening. This storm system is warm and will result
in a possibility of rain for most area. However, snow is expected
to impact the San Juan Mountains with 5 to 10 inches possible
above 9500 feet. Therefore have issued a Winter Weather Advisory
for forecast zone 19 above 9500 feet, valid through 1100 PM
Saturday night.


.SHORT TERM...(Tonight through Saturday night)
Issued at 229 PM MST Fri Feb 17 2017

The next Pacific shortwave trough will move across the area
tonight and Saturday from southwest to northeast. This is a warm
system so snow levels should remain relatively high tonight, 6500
to 7000 ft north of the Bookcliffs, and and 7000 to 7500 feet
from the Bookcliffs south. Light accumulations are expected in the
mountains, generally less than 3 inches.

There will be a break in the precipitations Saturday that will
travel from SW to NE as well, then another slightly stronger
trough will move in from the SW Saturday afternoon and overnight.
Again conditions will be warm, so the snowfall will accumulate
best in the mountains. Anywhere from 2 to 6 inches is expected
above about 7500 ft in the San Juan mts and the highest peaks of
the La Sals.

.LONG TERM...(Sunday through Friday)
Issued at 229 PM MST Fri Feb 17 2017

Sunday a stronger trough rounds the bottom of the longwave trough
over the western U.S. At 12z Sunday the NAM12 shows a close 500 mb
low over central AZ with will lift NE through the day. The low
center should travel through the southern half of CO by sunset
Sunday. Widespread warm sector precipitation is expected
throughout the day, then after the trough passes the flow aloft
will shift to the NW late Sunday afternoon and Sunday evening.
Cold advection behind the trough should lower the snow level to
5000 to 5500 feet by Monday morning. Several inches of snow area
possible in the mountains, with a few inches expected in the
higher valleys and four corners.

After a break in the unsettled weather late Sunday night through
Monday night, another Pacific system will approach the area from
the west and northwest. This system will bring colder air and a
better chance of snow to the forecast area Tuesday through Friday,
with northwest facing slopes and northwest Colorado more favored.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1153 PM MST Fri Feb 17 2017

A strong storm system sliding down the California coast is placing
Eastern Utah and Western Colorado in warm moist southwesterly
flow. This is resulting in a mix of MVFR and VFR conditions at the
terminals. As the system works its way closer to the area expect
precipitation to become wide spread by tomorrow morning. A break
in the precipitation will be possible Saturday night before the
next portion of the weather system arrives on Sunday morning.

Overall forecast confidence is moderate.



CO...Winter Weather Advisory until 6 PM MST Sunday for COZ018-019.

UT...Winter Weather Advisory until 6 PM MST Sunday for UTZ028.



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