Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 282342
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
442 PM MST Fri Feb 28 2020

.SHORT TERM...(Tonight through Saturday night)
Issued at 253 PM MST Fri Feb 28 2020

Mostly sunny skies and milder temperatures abound this afternoon
as warm air advection takes hold as the ridge of high pressure is
beginning to shift over the forecast area. Some high clouds are
encroaching upon the Four Corners region associated with a weak
low over SoCal resulting in slightly lower temps but still mild.
Temperatures tonight are not expected to be as chilly as recent
nights due to the presence of increasing high clouds but they will
still be below freezing. Mild conditions continue on Saturday with
temperatures reaching above normal levels under southwest flow
ahead of a positively tilted trough approaching from the PacNW. We
will see periods of filtered sun as high clouds will remain
present. The southern branch of a 180 kt upper level jet will move
in off the Pacific over SoCal, Arizona and New Mexico bringing in
some mid and high level moisture. Some mid level clouds may enter
by Saturday evening as this trough draws nearer with light
orographic showers possible over the eastern Uintas Saturday
evening.

.LONG TERM...(Sunday through Friday)
Issued at 253 PM MST Fri Feb 28 2020

As the positively tilted trough moves southeastward, the strength
of the southern jet will cause the trough to split with a closed
low forming over SoCal by Sunday evening, while the northern
branch of the upper level trough moves across the northern Rockies
and into the central high plains by Monday morning. We will see
some orographic showers with still mild air on Sunday, with the
colder air parked north of the border in Wyoming. This split
really prevents the colder air from entering our CWA with H7 temps
getting as low as -7C to -10C Sunday night across the northwest
Colorado mountains. The best forcing looks to occur Sunday evening
through Monday morning, where the best chance for accumulating
snow in the mountains looks to occur when looking at time heights.
As this trough continues to split, this leaves our CWA mainly in
the deformation area late Monday morning through the day on
Monday. A quick cross section through this area shows a bit of
CSI Monday morning through the afternoon, which would be
indicative of mesoscale banding and scattered convective
precipitation. Drier air is moving in from the northwest at this
time also, so hard to pinpoint which areas would see the best
snowfall. At this time, it is looking like a low end advisory
event for the western Colorado mountains with about 4 to 8 inches
possible and locally higher amounts dependent on convective
banding. Will not be issuing any winter weather highlites at this
time. The valleys appear to be too warm to see any appreciable
accumulation if that, while the lower valleys may end up being
primarily rain due to lack of cold air.

Beyond Monday, forecast confidence decreases as the models are not
in great agreement. The GFS is showing a couple trailing
shortwaves in northwest flow as this trough moves out and high
pressure builds in from the west through Wednesday. The EC on the
other hand is dry. These clipper like systems only appear to
impact the northwest Colorado mountains, particularly the Park
Range and Elkheads, maybe the Gore mountains down to Vail Pass.
Otherwise, temperatures will be slowly warming back up near normal
by mid-week and above normal to end the week under influence of
high pressure. Dry weather looks to prevail for areas outside of
the northwest Colorado mountains mentioned above Tuesday through
Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 442 PM MST Fri Feb 28 2020

Just cirrus clouds moving overhead tonight with some mid-level
moisture arriving during the afternoon Saturday. Regardless,
expect VFR conditions with CIGS above ILS breakpoints at all TAF
sites through the next 24 hours. Winds will be light and terrain
driven.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...MDA
LONG TERM...MDA
AVIATION...NL



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