Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 222329
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
429 PM MST Sun Jan 22 2017

.SHORT TERM...(Tonight through Monday night)
Issued at 305 PM MST Sun Jan 22 2017

The well deserved break today from the unsettled weather of the past
several days will end this evening as the third in a trio of winter
storms begins to impact the region. Latest satellite imagery this
afternoon shows the next surge of Pacific moisture infiltrating
the forecast area with some light showers popping up on radar.
Coverage of clouds and showers will increase from west to east
overnight with numerous to widespread precipitation occurring by
Monday morning when the greatest push of moisture arrives.
Precipitable water will range from 0.30 to 0.50 inches by this
time - 125 to 208% above the climatological norm! As the previous
shift mentioned, a powerful +160kt jet moving overhead Monday
morning will add substantial upper-level support throughout the
day, as well as generate areas of blowing snow and produce heavier
snowfall rates. This will especially be prevalent across the San
Juan Mountains with gusts exceeding 50kts at times.

Temperatures ahead of this system will be right around or slightly
above normal with a mild night on tap tonight as a result of
increased cloud cover. As mentioned in the Winter Weather Highlights
hoisted earlier today, temperatures greatly influenced the type and
wording of highlights, especially for the southern valleys. Areas
like Durango and Cortez, which were upgraded from Winter Storm
Watches to Warnings, will see periods of rain mixed with snow, or
even brief periods of all rain, during the day on Monday. However,
forecast soundings for these areas show plenty of cold air remaining
aloft, so do not anticipate the mixed precipitation during the day
on Monday will greatly alter accumulations or impacts. A weak cold
front will push across the area Monday afternoon, and cold air
filling in behind the front will aid in switching most valley
locations back over to all snow for Monday night.

Elaborating on accumulations, the southern and central mountains
will be favored throughout this storm, as a result of southwesterly
flow. The San Juans can expect to see amounts ranging from 10 to 20
inches with some areas above 10kft exceeding 2 feet through Tuesday.
The central Colorado mountains, as well as the Eastern Uinta
Mountains and Tavaputs Plateau in Utah, will see 6 to 12 inches
with locally higher amounts. The northern Colorado mountains,
which were upgraded from a Winter Storm Watch to a Winter Weather
Advisory, will see also see 6 to 12 inches. Generally 3 to 6 inches
will fall in the northern valleys, where additional advisories
were added. Down south, aforementioned areas including Durango
and Cortez look to see 6 to 12 inches through Tuesday. The
abundance of warm air advection ahead of the storm in southeast
Utah should prevent significant snow accumulations in areas such
as Mexican Hat and Bluff. Keep in mind, these snowfall amounts are
subject to change. Familiar factors that plague most all winter
storms, including the intensity of warm air advection,
overshadowing from terrain, or the development of heavy snow
bands, will again be in play with this storm. Regardless, major
impacts to travel will result from this storm, and drivers should
take caution and be prepared for delays or to make alternate
routes.

Coverage of precipitation will become more scattered across the
north on Monday night as the center of the main storm moves east,
but embedded waves in the flow and lingering moisture will keep
snow falling over most mountain areas through the night.

.LONG TERM...(Tuesday through Sunday)
Issued at 305 PM MST Sun Jan 22 2017

Models are in fairly good agreement as the center of the main storm
system moves east to a location over Nebraska before closing off
during the day. This storm system will move slowly east through the
remainder of the week. Snow intensity will decrease and become less
widespread in this wraparound moisture with best focus over the
northern mountains and northern San Juan mountains Tuesday and
Tuesday night. A relatively weak east/west oriented shortwave will
slowly drop south across the Great Basin Wednesday into early
Friday. This system will bring an unsettled period of snow showers
across mainly mountain locations with light accumulations expected.
Confidence is lower with this storm system. Temperatures are
expected to remain well-below normal through the work week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 424 PM MST Sun Jan 22 2017

Clouds and showers are quickly moving into eastern Utah and the
higher elevations of Colorado at this hour. Mid level ceilings
will continue to lower and reach near MVFR conditions or below
overnight. All TAF sites will see snow generally starting between 3
to 09Z though KCNY has just started reporting -SN at this hour.
IFR will be common tomorrow across the forecast area. Another
concern will be gusty winds of 20 to 30kts in the noon to
afternoon time frame. This will cause visibilities to drop and
also bring some wind shear to the airports. Included wind shear in
TAFs for KASE and KTEX though some may also occur at KEGE and
KMTJ. Confidence not high enough to include for now. Snow will
continue for much of the day on Monday with ILS breakpoints being
met early and staying down through 00Z though occasional breaks
may bring conditions briefly above these breakpoints. All
mountains will be obscured.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory from midnight tonight to 9 AM MST
     Tuesday for COZ001-002-005-014-020.

     Winter Storm Warning until 9 AM MST Tuesday for COZ009-012-
     017>019-021>023.

     Winter Weather Advisory until noon MST Tuesday for COZ003-004-
     010-013.

UT...Winter Weather Advisory until midnight MST Monday night for
     UTZ023-025.

     Winter Weather Advisory until midnight MST Monday night for
     UTZ022-024-029.

     Winter Storm Warning until midnight MST Monday night for UTZ028.

&&

$$

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


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