986
FXUS65 KGJT 031047
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
447 AM MDT Fri May 3 2024

.KEY MESSAGES...

- A system will brush the northern tier of eastern Utah and
  western Colorado today, bringing a few valley rain and
  mountain snow showers. Minor accumulations are expected with
  little to no impacts.

- Scattered showers are possible late Saturday mainly in the
  mountains. Elsewhere expect warmer and dry conditions.

- A strong system is expected on Sunday and Monday. It will
  bring widespread precipitation and strong winds.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 115 AM MDT Fri May 3 2024

A shortwave trough will pass just north of the CWA later today. It
will bring a cold front and enough moisture for scattered valley
rain and mountain snow showers. The best chances for showers is
along and north of the highway 40 corridor, but a few could reach as
far as I-70 with little to no accumulation there. The northern
mountains look to receive a bulk of the precipitation as well
as the upper Yampa valley. Snow levels will range from 7-8 kft,
but given most of this falls during the day snow should cause to
limited impacts. Showers enter the area from Wyoming later this
morning and continue pushing eastward this afternoon before
exiting this evening. The prefrontal jet is quite strong with
this system so daytime mixing and virga showers will allow these
winds to reach the surface. This afternoon most locations see
gusts over 25 mph, but they could be as high was 40-50 mph in
spots. Right now that appears to be along and just north of I-70
from Rifle to Vail. Temperatures will be rather seasonable
across the southern half of the area. Up north clouds and precip
will keeps things cooler than normal.

Conditions dry out tonight due to a lack of lift, but the moisture
never really leaves the region. A weak shortwave sneaks up from the
southwest tomorrow during the day. It along with the moisture will
support convection later in the day. The best chances for showers
will be the southern and central mountains. The QPF is on the low
side so impacts should be minimal. Temperatures recover and warm in
this southwest flow aloft.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 115 AM MDT Fri May 3 2024

Any lingering showers from Saturday afternoon along the Continental
Divide mountains should diminish during the overnight hours Saturday
night. After a warm day, nighttime temperatures will be quite mild
with lows roughly 10 degrees above seasonal norms. For Sunday,
attention quickly turns to a large and deep mid-level closed low
pressure system that will be tracking across the Great Basin to
round out the weekend. Ahead of this system, a tightening pressure
gradient... along with a pronounced southwesterly mid and upper
level jet with wind speeds of 40 to 50 kts at 700mb and over 100 kts
at 250mb... will punch into eastern Utah and western Colorado Sunday
afternoon. Strong diabatic heating will support deep boundary layer
mixing, resulting in the efficient transport of very strong winds
aloft down to the surface. Frequent surface wind gusts of 45 to 55
mph are likely to be common, with max gusts up to 60 mph in the
valleys and 80 mph in the high elevations not ruled out. These are
the types of setups that often produce our high end wind events
here, so wind highlights are almost certainly going to be needed at
some point. For now, keep an eye to the forecast and be prepared for
a very windy day on Sunday.

Sunday night into Monday, models are highlighting a strong shortwave
and vort max rounding the base of the closed low now over the
northern Rockies, taking on a negative tilt, and swinging across
eastern Utah and western Colorado. This potent and dynamic feature
will also be accompanied by a strong cold front as it blasts through
Sunday night into Monday. Ahead of and along the front, fairly
widespread showers are expected to break out as moisture, surface
convergence, and large scale forcing for ascent increases and
becomes maximized. Right now, guidance is pointing towards the
heaviest precipitation being confined to the central and northern
Colorado mountains where QPF amounts of 0.50" to 1.00" are
progged... with lesser amounts of 0.25" or less elsewhere. The air
mass will initially be very warm, as evidenced by snow levels well
above 9000 to 10000 feet, but will quickly cool to between 5000 and
6000 feet by early Monday morning in the wake of the front. No doubt
the mountains way up high will see some snow from this system, but
how much entirely depends on how much precip is left once the colder
air moves in. Since this will be a fast moving system, and most of
the significant precipitation will be over with by Monday afternoon,
there`s likely just not enough time when the highest QPF amounts and
the colder air overlap. However, if there`s one place where snow
accumulations may be fairly decent, it`s in the highest elevations
of the Park Range as cold, upslope, orographic, northwesterly flow
and another wave on Tuesday may allow snow to pile up in excess of 6
and possibly 12 inches.

Beyond Tuesday, the rest of the long term period likely remains
unsettled with deterministic models and ensembles highlighting
continued troughing across the Intermountain West. Showers in the
high country will probably be a daily occurrence, particularly across
the northern Colorado mountains. Elsewhere, the big story will be
the cooler than normal temperatures with highs largely in the 50s
and 60s down low, and 30s and 40s up high. Overall, the synoptics
driving the pattern next week are chaotic and likely to be
influenced by mesoscale processes and convection. As a result,
expect to see some changes in the forecast and for the finer details
to remain unclear until we get closer.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 500 AM MDT Fri May 3 2024

VFR conditions should hold over the next 24 hours though cigs
will be lowering up north in the afternoon as the next system
works through. KHDN should see a passing shower with an outside
chance of MVFR conditions by mid afternoon. Gusty afternoon
winds of 25 to 40 mph are expected again at most sites. ILS
cigs are possible at KEGE and KRIL late afternoon.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...KJS
LONG TERM...MDM
AVIATION...TGJT