Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 201812
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1112 AM MST Sat Jan 20 2018

.UPDATE...
Issued at 1111 AM MST Sat Jan 20 2018

Snow already an issue from the Uinta Basin into NW Colorado this
morning and will be changing some of the advisories to earlier
start times as a result and adding more of the Yampa Valley. The
heaviest precipitation remains off to our West where the front is
hung up on the Wasatch as anticipated. However the atmosphere has
a spring like feel with plenty of instability around and as a
result expect the radar to continue to blossom through the
afternoon. Could see a strike of lightning as well. Front still
expected to break loose from the terrain later this afternoon and
begin to push eastward through the evening. Expect heavy burst of
precipitation as this occurs.

UPDATE Issued at 1102 AM MST Sat Jan 20 2018

Snow already an issue from the Uinta Basin into NW Colorado this
morning and will be changing some of the advisories to earlier
start times as a result and adding more of the Yampa Valley. The
heaviest precipitation remains off to our West where the front is
hung up on the Wasatch as anticipated. However the atmosphere has
a spring like feel with plenty of instability around and as a
result expect the radar to continue to blossom through the
afternoon. Could see a strike of lightning as well. Front still
expected to break loose from the terrain later this afternoon and
begin to push eastward through the evening. Expect heavy burst of
precipitation as this occurs.

&&

.SHORT TERM...(Today through Sunday)
Issued at 436 AM MST Sat Jan 20 2018

Very little change to forecast thinking as models remain fairly
consistent. The front remains to our west, running from north of
Salt Lake City southwestward to south central Nevada. Satellite
clearly showing a baroclinic leaf over Utah and Arizona while our
radar has started picking up on some higher clouds. Some snow can
be seen over the Uintas at this hour so the warning for that area
looks to be on track. For the rest of today, strong southwesterly
flow will continue to keep warm temperatures in place. The cold
front will be just west of the Colorado/Utah border towards the
evening hours so expect rain for the valleys through the day with
snow above 8 to 8.5K feet (maybe a bit higher). As has been noted
over the last few days, the front has slowed down which has also
slowed down the onset of precipitation. Things will get going from
about 2PM onwards with the heaviest rain/snow to occur from the
early evening hours to early Sunday morning. Current advisories
and amounts look good, though might need to add zone 2 (Craig,
Meeker) later this evening for a quick 2 to 3 inches of snow
though confidence just not there at the moment to issue anything
right now. Later shifts can keep an eye on temps and evolution of
the front. Once the cold front moves through, temperatures will
start dropping and snow levels will reach valley floors. Central
and southern valleys may see some light snow accumulation, around
an inch, though higher elevations along 160 west of Durango
towards Mancos may see higher amounts as they tend to do.

By daybreak Sunday morning, colder air will continue to move in
causing plenty of showers across the entire forecast area. By
about noon these should wane except along the Continental Divide
where they should continue for through the afternoon. Outside of
the showers, expect a mostly cloudy day with cooler temperatures
across the region.

.LONG TERM...(Sunday night through Friday)
Issued at 436 AM MST Sat Jan 20 2018

A few snow showers will linger near the Divide Sunday evening as
the main upper level low pulls out into the plains, being
replaced by short-wave ridging sliding over from the west. Ridge
flattens out Monday afternoon with just enough mid-level moisture
dragging along to help squeeze out a few showers across the
northern mountains in favorable orographics. Weak wave enhances
the potential for snow showers Monday night and Tuesday with focus
on the northern mountains once again, generally from Vail Pass
northward to the Wyoming state line. This system has been trending
weaker over the past several model runs and will keep
accumulations on the low side for now. Remainder of the forecast
area will be on the dry side for much of the week as another
transitory ridge slides over around mid-week. Pattern breaks again
by late in the week with a stronger longwave trough moving
onshore. This system will arrive over our region late Thursday and
Friday, bringing more widespread and welcomed rain and snow.
Expect a much cooler weak in the temperature department as we see
readings dropping back to more normal values for this time of the
year.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1102 AM MST Sat Jan 20 2018

Unstable...moist southerly flow allowing showers to increase late
this morning and trend should continue this afternoon. Hit or miss
nature over many sites makes for a difficult forecast with quickly
changing conditions possible due to precipitation type in some
areas. KVEL at IFR conditions and this expected to continue well
into the evening as the system to west lifts across the Rockies.
Expect downward trend over remainder of the TAF sites as this
occurs and this should be indicated in 18Z issuance. Expect many
amendments through the evening as snow increases with a frontal
passage then lets up behind it. Widespread lower flight criteria
expected through much of the night into Sunday morning.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 10 AM MST Sunday for COZ001-002.

     Winter Weather Advisory until 2 PM MST Sunday for COZ009-012-018-
     019.

     Winter Weather Advisory until 2 PM MST Sunday for COZ003-017.

     Winter Weather Advisory from 6 PM this evening to 9 PM MST
     Sunday for COZ004-010-013.

UT...Winter Weather Advisory until 10 AM MST Sunday for UTZ025-028.

     Winter Storm Warning until 6 AM MST Sunday for UTZ023.

&&

$$

UPDATE...TGJT
SHORT TERM...TGR
LONG TERM...JDC
AVIATION...TGJT



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