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000
FXUS65 KGJT 161807
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1207 PM MDT Tue Apr 16 2024

.KEY MESSAGES...

- Significant snowfall continues through this morning impacting
  the northern and central Colorado mountains, including Vail
  and Rabbit Ears passes. Look for these showers to decrease
  through the afternoon.

- Breezy, milder, and unsettled conditions linger through the
  end of the week.

&&

.UPDATE...
Issued at 1146 AM MDT Tue Apr 16 2024

Will allow the winter weather advisories expire on time.
Orographic snow will linger through the next several hours but
be offset by increased insolation allowing roads to melt in most
locations.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 345 AM MDT Tue Apr 16 2024

Satellite imagery shows the low is just now pushing out onto
the front range with the H500 low centered just north of the
Palmer Divide, farther north than all the models predicted, and
the lower level, H700 low emerging east of Boulder, well south
of the model predictions near Cheyenne. That the low is more
vertically stacked indicates the more barotropic nature of the
low having left the frontal boundary hung up in the mountains.
This would also explain the low moving much slower, six hours or
more behind the model predictions. Look for strong
frontogenesis once the low moves out onto the Plains this
morning and picks up steam ejecting to the east- northeast. That
the motions of the low is running behind the models may
indicate the wrap-around moisture will be a little slower to
move east of the Divide allowing showers to hang on into the
afternoon hours in the northern and central Colorado mountains,
though with daytime heating, few if any impacts will come of the
extended showers. A weak ridge is moving into the region behind
the low with subsidence curbing the stronger convection we saw
overnight and limiting showers to lighter, orographic driven
activity from here on out.

Look for an additional few inches snow possible in the central
and northern Colorado mountains generally above 8,000 feet with
local accumulations of up to ten inches possible on the Park
Range above 10,000 feet. Thus the Winter Weather Advisory for
the Elkhead/Park Mountains to the north, and the Gore/Elk
Mountains and Flat Tops to the south continues until noon today.
Be aware that there are currently winter driving conditions on
Vail and Rabbit Ears Passes that may continue through the
morning hours, and that east-bound Vail Pass is closed for
safety concerns. These conditions should rapidly improve through
the day as temperatures warm.

As the ridge moves in this afternoon, temperatures will warm to
near normal in the mountains and to about five degrees above
normal in the lower valleys with the clouds scattering out from
southwest to northeast across the region. The ridge will transit
the region overnight as the next trough system to the northwest
drops southeast into Idaho and Wyoming. Satellite imagery shows
the frontal boundary just moving into northern Washington in
good agreement with the models. This boundary will push south to
about the Colorado/Wyoming Border where it will tend to stall
out for the next few days, but more on that below. There is a
weak AR associated with this system with IVT`s running 100-200
kg/m/s. This isn`t so much a lot of moisture in the AR, but more
a result of the strong zonal flow aloft with H500 winds running
60 to 75 kts advecting a light stream of moisture off the
Pacific through Oregon and into the northern areas of eastern
Utah and Western Colorado by Wednesday morning. Though the
moisture is limited, it will still be enough to produce light
orographic showers again Wednesday with showers pushing south to
the Flat Tops in the afternoon. The will produce little if any
snow accumulations over the higher elevations. Clouds will
generally stay north of the I-70 Corridor Wednesday with skies
being mostly sunny to the south. Temperatures will remain near
normal across the northern areas with the clouds and showers,
but will warm to about ten degrees above normal along and south
of I-70 tomorrow afternoon.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 345 AM MDT Tue Apr 16 2024

Primarily zonal flow will remain across the Western Slope from
mid to late this week with a large low pressure trough situated
to our north and high pressure to our south. This will create a
tight thermal gradient with moisture and overrunning
precipitation across the north and drier conditions across much
of the central and southern areas. Westerly orographics should
keep snow falling in the mountains, especially over the Park
Range, with the best potential through Wednesday evening. From
Wednesday through Saturday, the Park Range stands the best
chance to see some accumulating snowfall. However, each 24 hr
period during this time really doesn`t amount to all that much
with maybe 1 to 3 inches each day across the higher elevations
of the northern Colorado mountains and potentially extending
down into the central mountains by Friday and Saturday as
shortwave moving around this large trough swings southward and
helps drive this moisture east with high pressure ridging and
drier air replacing it by Sunday into early next week. So, even
though light orographic snow will continue in this westerly flow
across the northern and eventually central mountains, snow
levels will remain fairly high with minimal impacts. Some
showers may even exhibit virga, resulting in gustier winds
rather than precipitation reaching the ground as low levels
continue to dry.

Temperatures across the northern mountains and adjacent valleys
look to remain near to around 5 degrees below normal from mid
week through the coming weekend in this unsettled pattern.
However, much different story for the central and southern areas
as temperatures rise to around 5 to 10 degrees above normal
(give or take). These warmer temperatures expand northward
Sunday into early next week as the moisture exits and high
pressure moves in, with highs potentially rising to 10 to 15
degrees above normal. Being that the upper level jet stream
remains north of the forecast area, the gradient will be tight
enough to promote decent mixing for breezy conditions each
afternoon. These gusty winds along with low relative humidity
across the central and southern valleys will help promote
elevated fire weather concerns where fuels are dry.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1151 AM MDT Tue Apr 16 2024

Moisture will continue to impinge upon the Colorado mountains
leaving some terrain obscuration and light snow in place over
the next several hours. However a drying trend should bring
clearing skies by sunset with winds also easing. Another batch
of moisture drops southward toward our northern CWA during the
early morning hours bringing another mid level cloud deck to end
this forecast at the northern TAF sites. MVFR cigs should be
lifting to IFR by 22Z and then above ILS by 00Z with VFR
prevailing thereafter at all locations.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory until noon MDT today for COZ004-010-
     013.
UT...None.

&&

$$

UPDATE...15
SHORT TERM...DB
LONG TERM...MDA
AVIATION...TGJT