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606
FXUS65 KGJT 202341
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
541 PM MDT Mon May 20 2024

.KEY MESSAGES...

- Showers and thunderstorms will spread south and eastward
  tonight as the cold front associated with a late season spring
  storm moves through the area tonight.

- Colder air will cause snow to develop in the mountains with
  accumulation`s above 9,000 feet expected to range from 2 to 5
  inches with locally higher amounts.

- Cooler temperatures behind the front on Tuesday will bring
  markedly cooler temperatures with highs dipping by close to 15
  degrees relative to today`s highs.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 247 PM MDT Mon May 20 2024

Showers and isolated thunderstorms continued to fire along and
northwest of the cold front associated with the late spring
storm over the Great Basin. This activity has remained northwest
of a line from KDWX to 30S KPUC and isn`t likely to shift much
over the next few hours. Meanwhile, there is a marginal threat
of severe wind gusts from stronger cells over the northwest
through early evening. South and east of the line, strong gusty
south to southwest winds were the rule, and while clouds have
increased, no showers were apparent.

The trough axis shifts eastward tonight while a vort lobe
rotating through the base of the trough drives the cold front
across the forecast area. Dynamic forcing along with convergence
along the boundary will cause showers to move to the east and
expand southward with showers becoming more likely as the night
progresses. Infiltration of colder air will bring snow levels
down to near 7000 feet over northeast Utah and northwest
Colorado while hovering from 8500 to 9000 feet elsewhere.
Mountain snow will largely be confined to areas above 8500 feet
in the north and 9000 feet in the south with accumulations more
notable above 9000 and 10000 feet, respectively. Not enough snow
indicated to issue Winter Weather Advisories, but mountain
passes are likely to see impacts, especially at Rabbit Ears and
Vail Passes.

Some of the trough`s energy shifts to the northern Plains on
Tuesday, but the main trough is expected to pass over the area
during the day. As a result, showers and thunderstorms remain
likely over the mountains with the northern and central ranges
favored and lesser chances over the lower elevations of eastern
Utah and southwest Colorado. Total mountain snowfall from this
event is expected to be around 3 to 6 inches in the higher
elevations and locally up to 10 inches on favored peaks and
ridges. Temperatures will be markedly cooler behind the front
with highs running close to 10 degrees below seasonal norms.

Drying and clearing is expected in the subsident region in the
wake of the trough Tuesday night. As a result, we`ll see an end
to shower activity while clearing and colder air brings
unusually cool overnight lows with temperatures also dipping
to near 10 degrees below normal, though it doesn`t appear a
damaging freeze will occur in areas with sensitive vegetation.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 247 PM MDT Mon May 20 2024

Much drier weather is in store on Wednesday in the wake of our
departing trough, but a few returning spotty showers can`t be ruled
out across the Continental Divide mountains given lingering residual
moisture and daytime heating. High temperatures will be roughly 4 to
8 degrees below normal for this time of year. By Thursday, mid-level
flow becomes southwesterly again out ahead of another deep trough
and cold front digging across the Intermountain West. In response,
developing warm advection within the southwest flow ahead of the
front will boost high temperatures by about 5 degrees compared to
Wednesday... and more in line with seasonal norms. The cold front is
progged to move across eastern Utah and western Colorado Thursday
afternoon and evening, bringing another shot of cooler air in its
wake. As for precipitation chances, moisture along and ahead of the
front is modest at best, so despite decent forcing, slight chance to
chance PoPs are mainly confined to the high terrain well to the
north of the I-70 corridor, and QPF is mostly under a tenth of an
inch.

Behind the front, a cooler day is expected to round out the work
week on Friday with highs once again several degrees below normal. A
couple trailing waves have the potential to bring a few more rounds
of unsettled weather Friday into the weekend, though significant
differences still exist amongst the latest models. For now, will
continue to lean on the blended solution, which favors northeast
Utah, northwest Colorado, and the higher elevations along and north
of I-70 for any additional precipitation. Given the potential for
more clouds and precip, temperatures will continue to run a few to
several degrees below normal.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
-- Changed Discussion --
Issued at 535 PM MDT Mon May 20 2024

Strong southerly to southwesterly winds will continue to impact
terminals along and south of the I-70 corridor between now and
06z. These winds will turn northwesterly and weaken in the wake
of a cold front currently moving through eastern Utah. Showers
along and ahead of this front, as well as showers produced by
daytime heating along terrain features, will be capable of
producing erratic winds with gusts in excess of 40 knots. Brief
heavy rain, small hail, and lightning will also be threats with
more organized showers and storms. Lighter, more stratiform
showers will linger behind the front through 12z or so tomorrow
morning, holding on longest over the higher terrain. Only the
very highest elevations can expect snow. KASE, KEGE, and KRIL
can expect to remain below ILS Breakpoints between 06z and 12z,
and all terminals can expect periods of MVFR/IFR conditions with
passing showers and with the cold front. Otherwise, VFR
conditions will prevail. Gusty winds will return for tomorrow
afternoon.
-- End Changed Discussion --

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...NL
LONG TERM...MDM
AVIATION...TGJT