186
FXUS65 KGJT 210957
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
357 AM MDT Tue May 21 2024

.KEY MESSAGES...

- Some early morning snowfall will range from 3 to 6 inches with
  locally higher amounts, generally above 10K feet. Snow will
  melt quickly after sunrise.

- More isolated to scattered showers expected this afternoon as
  an upper level disturbance moves through. Some thunderstorms
  also possible.

- Highs today will be 10 to 15 degrees cooler than yesterday
  while lows Wednesday morning will be around 10 degrees cooler
  than normal.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 240 AM MDT Tue May 21 2024

A broad swatch of rain and snow is moving across the CWA at the
moment thanks to the cold front. The current webcam at Snowmass
is showing some decent snowfall rates with 2 inches already
having fallen there. Rainfall amounts across the Western Slope
are ranging from a lowly .01 inches to a few spots around
Glenwood Springs reporting near .3 inches. Not too bad all
things considered. As mentioned, the cold front responsible for
this moisture will continue to track south and east this morning
while the heavier precip ends by mid morning as the forcing from
the front comes to an end. Snowfall amounts for the higher
elevations, generally above 10K feet, still look to range in the
3 to 6 inch range with some spots possibly reaching 8 to 10
inches when all is said and done. Coverage for these higher
amounts will be limited and thus, no highlights. Even so, Vail
Pass and Rabbit Ears Pass may be a bit dicey this morning due to
some accumulating snow. Once the sun rises, however, any snow
should quickly melt. For the remainder of the day, the upper
level trough that supported the cold front will be moving across
eastern Utah and western Colorado and will provide the upper
level support for more rain and possibly a few thunderstorms.
Coverage will reach a maximum from just after noon and
continuing through 6PM. Cloud cover may limit convection some
but with steeper lapse rates and SBCAPE of 200 to 500 J/kg the
possibility certainly exists. Temps today will also be
noticeably cooler with highs anywhere from 10 to 15 degrees
cooler than yesterday.

As the upper level trough exits the area around midnight, precip
will come to an end and with mostly clear skies expected, look
for some cool overnight lows, running about 10 degrees cooler
than normal. Temperatures will hover around freezing, if not a
bit below, for the northern valleys. The Grand Valley will drop
to the low 40s while the southern valleys will also drop near or
just above freezing. It`s almost June...sigh.

Wednesday, wind flow becomes more south through southwesterly
ushering in some warmer air from the south. Partly cloudy skies
will also allow plenty of daytime heating so we`ll see a quick
rebound to warmer temps.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 240 AM MDT Tue May 21 2024

A weak clipper system will pass to our north Wednesday night. This
is one of several shortwave disturbances along a frontal boundary
that will impact the CWA into the weekend. As the boundary settles
southward on Thursday, our northern mountains stand the best chance
at a few showers developing Thursday afternoon, while cloud cover
will likely invade farther south towards the Highway 50 corridor.
Models are trying to resolve an area of confluence over the West
Slope Thursday afternoon, merging a split jet overhead. This is
expected to yield some stronger surface winds as we mix down
Thursday afternoon. This looks like an opportunity for more critical
fire weather conditions around the Four Corners, given the warm
temperatures, low relative humidities, and gusty winds. The frontal
boundary will push south Friday and shower activity along the Divide
will too. Winds will remain gusty down south again Friday afternoon,
but less so than Thursday, as the stronger winds aloft slide east
and southward. Relative humidity`s inch up as well, thanks to
additional moisture along the front. Unfortunately, precipitable
moisture looks pretty spartan and aside from the high country,
surface rain looks unlikely. A deeper low diving out of the PACNW
into the Panhandle of Idaho Saturday morning will push another wave
across the CWA Saturday afternoon and into Sunday. This should be
good enough for some more widespread shower development on the
terrain Saturday afternoon. By Sunday afternoon, the upper low has
degraded into an open wave and drier northwesterly flow behind the
trough will keep the subcloud layers dry enough to put the brakes on
showers. Gusty outflows and a few short downpours remain a concern
on Sunday under the steep lapse rate regime. By Monday, models are
keen to build a big ridge from Mexico to the Canadian Rockies. This
scenario will send temperatures back above May climatology and cast
some sunshine on Memorial Day barbecues. Temperatures will hover
around climatology to close out this week and begin the holiday
weekend. As the persistent frontal boundary clears the region
Sunday, it looks like afternoon highs will trend downward ahead of
the early week warm up Monday and Tuesday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1142 PM MDT Mon May 20 2024

Showers and a few thunderstorms will continue overnight as a
frontal boundary slowly clears western CO and eastern UT. Winds
will taper over the next few hours as the front passes. Showers
and cloud cover will hang up on terrain closer to the Divide
tonight and mountain terminals are likely to see intermittent
periods of MVFR/IFR conditions with lower ceilings and showers.
A few gusty winds from decaying showers are possible as well.
Showers and thunderstorms will remain in the forecast for
Tuesday afternoon as an upper level wave finishes working
through the region. VFR conditions will likely finish the tail
end of this TAF period, as the last of the shower activity
pushes across the West Slope Tuesday evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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