Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 100839

Area Forecast Discussion
National Weather Service Grand Junction CO
139 AM MST Tue Dec 10 2019

Issued at 139 AM MST Tue Dec 10 2019

Dense fog has formed across portions of the eastern Uinta Basin
early this morning. A sampling of webcams and the observation from
KVEL indicated dense fog was mainly south of Vernal proper, but is
likely to spread outward as temperatures continue to fall during
the night. Therefore, have issued a Dense Fog Advisory for the
eastern Uinta basin through 11 AM MST.


.SHORT TERM...(Tonight through Tuesday night)
Issued at 312 PM MST Mon Dec 9 2019

Light convective showers are still occurring in northwest flow
behind the departing trough as one last piece of energy moves
through. Not much evidence of anything reaching the ground in the
lower central valleys but the higher peaks appear to still be
seeing some light snowfall. The higher passes remain wet with some
patchy fog up high. Skies are improving from the northwest as
drier air moves in with high pressure building to the west. Light
snowfall may continue over the northern Park and Gore range
through the overnight into Tuesday morning due to weak orographic
flow but do not anticipate any significant accumulations.
Temperatures tonight will be much colder than last night due to
less cloud cover. Some patchy fog is possible in some areas that
have seen recent moisture. In terms of a repeat performance in the
Grand Valley as was seen last night into this morning, confidence
is low as any lingering low level moisture will have been vacated.
Dense fog is more common the night after a recent rain or
snowfall, due to evaporation of moisture off the surface and
advection of cooler air aloft. The ground has had sufficient time
to dry, lessening the chance of this occurring. Tuesday
afternoon will be met with dry conditions and mostly sunny skies,
although some thin high cloud cover will be present. Temperatures
should stay near to slightly above normal.

.LONG TERM...(Wednesday through Monday)
Issued at 312 PM MST Mon Dec 9 2019

A weak shortwave trough looks to move across the region on
Wednesday but this is not bringing much moisture with it. Most
models indicate very little to no precipitation but an increase in
mid and high cloud cover. Some light snowfall is possible over the
higher terrain, but chances are pretty low. Mostly dry conditions
are expected through Thursday with temperatures staying near
normal for daytime highs and overnight lows staying cold but
above normal due to increased cloud cover. Westerly flow will set
up Thursday into Friday as a 160 kt jet sets up over the northern
California and southern Oregon coast, advecting in some Pacific
moisture. This moisture will slam into the northern and central
mountains as the jet shifts southward, with snow beginning
Thursday night into Friday morning. This moist pattern will remain
through the weekend as the upper level trough associated with
this upper level jet moves through the region Saturday into
Sunday, finally bringing much colder air with it as H7 temps drop
into the -10C to -16C range by Sunday morning. Until then, snow
levels appear higher where the high elevations in the northern and
central mountains could see decent snowfall Friday into Saturday,
spreading into the southern mountains late Saturday into Sunday.
Snow levels appear to lower to all valley floors Saturday night
into Sunday as this colder air advects in with cold front and
trough passage. Hard to pinpoint amounts at this time but this is
the next best chance for widespread precipitation and accumulating
snowfall. Drier air moves in from the north on Monday but chances
are some snow will be lingering behind this trough as orographics
and lingering moisture take over with temperatures in that sweet
dendritic zone. As expected, temperatures take a dive to below
normal levels Sunday through early next week.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1058 PM MST Mon Dec 9 2019

Some high clouds will move overhead tonight but any ceilings will
be at or above 20K feet. Having said that, KHDN, KASE and KVEL are
sitting at MVFR and IFR due to some low clouds that have formed
over the last few minutes. Will need to keep an eye on things over
the next few hours to see if they hang around. Next concern is fog
for KVEL and KGJT. Expect some patch spots for the Grand Valley
but a better chance for KVEL. With those high clouds though, might
keep fog at bay. Again, later shifts will need to keep an eye out.
Tomorrow, VFR conditions under mostly sunny skies.



UT...Dense Fog Advisory until 11 AM MST this morning for UTZ024.



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