Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 191031
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
331 AM MST Mon Feb 19 2018

.SHORT TERM...(Today through Tuesday)
Issued at 331 AM MST Mon Feb 19 2018

Can`t really say this storm is starting off with a bang...unless
it is your screen door getting torn of the hinges because of the
wind. GOES16 water vapor products showed the narrow fire hose of
Pacific moisture spreading across the 4 Corners earlier when the
San Juans started to pick up some snow showers. Now this imagery
is showing the dry conveyor belt rounding the trough and extending
from SoCal into SoUtah with convection blossoming on the nose of
this over western Colorado. Not only will this feature associated
with the jet core help instability through the day...models
continue to indicate a fairly distance dry slot from SE.Utah into
NW.Colorado. Showers likely to pop in this area but more concerned
with the instability helping to tap into the stronger winds aloft
and decided to expand our wind advisory. The cold (arctic) front
has dropped into NE.Utah far NW.Colorado where it is producing
light snow at Craig this morning. With the strong southerly flow
in place model want to stall or even retreat this front back
northward today before it rushes southward overnight as the upper
trough approaches. This feature will be important to watch as
this should be where heavier precipitation will focus. The
southerly flow will be good for orographics but instability will
win again today. Models are favoring the E.San Juans for capturing
the best precipitation the next 24 hours though any south facing
higher slope could do well. The streaky convective precipitation
pattern expected today will be hard to pinpoint other areas that
will do well. Therefore no confidence in changing winter
highlights just yet but can`t help but feel this storm will be
under performing earlier expectations. Convection has proven me
wrong many times though. Moisture is all but erased by late
tonight as the trough moves overhead and we are left with
orographics...instability and cold advection. Still a good combo
for making some decent snow but trends have really dropped off for
widespread precipitation lasting through tomorrow. Many spots may
have seen their high early this morning as we remain mild with
the winds. Cooler air moving in this afternoon should hold things
fairly steady. Much colder air filters in tonight and highs
tomorrow will feel more like winter.

.LONG TERM...(Tuesday night through Sunday)
Issued at 331 AM MST Mon Feb 19 2018

The large trough over the western US will leave temperatures about
10 degrees below normal for this time of year throughout the week
after the strong cold front comes through tomorrow. These cooler
temperatures will be more noticeable during the nighttime hours,
as bright sunshine will accompany this cooler airmass until the
latter part of the week. The first post- cold front disturbance is
still progged late Wednesday night in southwesterly flow bringing
moisture in WAA to southwest facing slopes through Thursday.
Precipitable water values don`t get much higher than two tenths of
an inch in this southwest flow, so this is not anticipated to be
a big precipitation maker. This system Wednesday night through
Thursday is a precursor to a much larger trough moving into the
Great Basin late next week in the Thursday/Friday timeframe. This
late week trough is on track to move through the UT/CO border late
Friday through Saturday - similar timing as previous forecast
runs.

The progressive pattern anticipated over the next week looks to
continue in the longer term, with the 8-14 day outlook indicating
odds of slightly wetter than usual conditions across the Great
Basin into early March.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 331 AM MST Mon Feb 19 2018

Expect a busy day amending TAFs as winds...clouds and
precipitation all combine to create variable flight conditions.
The precipitation will be very showery which means VFR conditions
could quickly become LIFR as snow showers pass by or settle in.
Winds will be impacting not only landing and takeoff operations
but mountain turbulence should again be present. Expect widespread
terrain obscuration as well. Conditions not likely to improve
until later in the day on Tuesday as this storm winds down.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 8 AM MST Tuesday for COZ001>005-
     010-017.

     Wind Advisory until 5 PM MST this afternoon for COZ006-007-011-
     020-021.

     Winter Storm Warning until 8 AM MST Tuesday for COZ009-012-013-
     018-019.

UT...Winter Weather Advisory until 8 AM MST Tuesday for UTZ023-025-
     028.

     Wind Advisory until 5 PM MST this afternoon for UTZ022-027>029.

&&

$$

SHORT TERM...15
LONG TERM...JAM
AVIATION...TGJT



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