Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 121002
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
402 AM MDT Tue Mar 12 2024

.KEY MESSAGES...

- Clouds increase this afternoon ahead of a strong cold front.
  The cold front will move through Wednesday and Thursday
  bringing widespread precipitation to Utah and Colorado.

- Winter Weather Advisories remain in effect for 6 to 12 inches
  over the Colorado mountains beginning this evening through
  Thursday.

- Precipitation will shift to southern regions Thursday and
  Friday as a closed low affects the region. The finer details
  are still uncertain though another round of winter highlights
  for the San Juan mountains is becoming more likely.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 241 AM MDT Tue Mar 12 2024

As expected, some light snow is falling along the I-70 corridor
from Debeque Canyon up to Vail Pass. The good news is that warm
temperatures today are melting the snow as it hits
roads/pavement. Can`t find any accumulations on local webcams or
any CDOT cameras though if snow is sticking anywhere, it`ll be
heading up to Vail Pass. If it is, it`ll melt very quickly after
daybreak...most places will just have to contend with some wet
roads. The shortwave responsible for this precip will have moved
over to eastern CO shortly after daybreak with a few, very
isolated, showers lingering along the Divide. If you have a
chance to do something outside today, suggest getting out there
and doing it as the next system is just on our doorstep and will
bring unsettled weather for the rest of the week, especially
down south. For the rest of today, variable cloudiness will be
the rule this morning with clouds increasing in the afternoon
ahead of the next system. Highs today will be similar to
yesterday, maybe a wee bit cooler but still quite warm.

The upper level trough to our northwest, and flow around the
trough, will pump plenty of moisture into the region and
favorable orographics will allow some light precip over the
higher terrain this evening. The trough will support a cold
front at the surface and as it approaches, an uptick in coverage
and precip is expected. The front looks to be fairly slow moving
so we can expect precip across the region for much of the day
Wednesday. Guidance continues to show some banded precip with
some healthy QPF amounts in those bands on Wednesday. The
question is always where those bands will setup. For now, just
ahead of and along the cold front are the best locations. Either
way, snowfall amounts remain in the 6 to 12 inch range for the
mountains though latest runs did bump up amounts a bit. For
now, the going winter weather advisories look good and will
remain in effect. Kept the eastern Uintas out of the advisories
because 6 hr snowfall amounts are an inch or less and do not
expect much in the way of impacts from such tepid snowfall
rates.

As Wednesday progresses, the upper level trough will transition
into a closed low and start digging southward over far western
Utah. This is the really tricky part with regards to the
forecast. Lots of questions remain and we`re only a few days
out.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 241 AM MDT Tue Mar 12 2024

Unsettled weather conditions are expected to continue late into the
week, as models grapple with a developing winter storm here in the
mountain west. Rather than attempt to describe what models are
trying to resolve (with a level of uncertainty), it is probably
best to stick with a broad brush outcome. Wednesday night and
Thursday will see light mountain snow showers and occasional
valley rain continue under a trough of low pressure hanging over
the Rockies. A cutoff low is expected to develop in the
Southwest late Thursday and early Friday morning. This low is
expected to entrain a healthy plume of Pacific moisture. Current
expectations are for a round of snow showers early Friday
morning to deliver significant accumulations of snow to the La
Sals and Abajos, as well as across the San Juans. Uncertainty
with the track of the low is casting some doubt on winter
highlights this morning. Waiting for another forecast package to
potentially shed some light on finer details. It looks like
winter highlight potential is there for our southern mountains.
Deterministic models are attempting to strand the low under a
ridge building into the Pacific Northwest by the weekend. This
could keep some remnant moisture and mountain snow showers in
the picture through the weekend, as it blocks any intrusion of a
drier air mass. If we can count on the model outputs, it looks
like much of this activity will favor the Four Corners region,
including our southern mountains, whereas the northern half of
our CWA could remain cold and dry next weekend. Afternoon highs
will trend below climatology and morning lows will trend at or
above normal, thanks to cloud cover and persistent precipitation
throughout the extended forecast period. Mountain travel will
continue to demand a vigilant eye on the local forecast this
week and next weekend, as this will be an evolving forecast with
the late week winter storm.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1138 PM MDT Mon Mar 11 2024

A few scattered showers are falling overnight thanks to a weak
shortwave disturbance tracking across the mountains. Ceilings
will come down temporarily with these showers, but VFR
conditions are expected to return before daybreak. Winds will
pick up out of the southwest Tuesday afternoon and remain breezy
towards sunset, when they will sit back down. Cloud cover is
expected to begin returning late in this TAF period ahead of the
approaching storm Tuesday evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory from 6 PM this evening to midnight MDT
     Wednesday night for COZ004-013-017.

     Winter Weather Advisory from 6 PM this evening to 6 AM MDT
     Thursday for COZ009-010-012.

     Winter Weather Advisory from midnight tonight to midnight MDT
     Wednesday night for COZ018-019.

UT...Winter Weather Advisory from 6 PM this evening to midnight MDT
     Wednesday night for UTZ028.

&&

$$

SHORT TERM...TGR
LONG TERM...LTB
AVIATION...TGJT


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