Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 081151
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
551 AM MDT Sat May 8 2021

.SHORT TERM...(Today through Sunday night)
Issued at 405 AM MDT Sat May 8 2021

The cold front has already progressed through northeast Utah and
much of northwest Colorado early this morning, and is currently
approaching the I-70 corridor near Rifle. Breezy conditions have
accompanied the front with sustained speeds of 10 to 15 mph and
gusts over 25 mph common. Unfortunately, models have continued to
trend drier and drier with this system with surface dewpoints only
climbing into the mid 30s along and behind the front. Light
returns on radar have not translated to much of anything at the
surface based on webcams and surface observations. The midlevel
trough axis will progress east across the area mid to late
afternoon before sliding east of the Continental Divide this
evening. Though available moisture and lift aloft have decreased
with the latest runs, orographic lift and surface convergence
along the front will still fuel scattered convection along the
Divide this afternoon. Precipitation totals will be light with
this system given the dry antecedent conditions with generally a
few hundredths to a couple tenths of an inch of QPF expected. An
inch or so of fresh snow will fall at the highest peaks in the
southern and central Colorado ranges by day`s end. Shower activity
will diminish by sunset with the trough`s departure.

Further west in the wake of the cold front, gusty post-frontal
northwesterly flow will settle overhead. Denser cloud cover will
dissipate as drier air filters into the region with minimum
humidities dropping back into the low to mid teens. The gusty
winds will combine with these lower humidities to produce critical
fire weather conditions across the western zones. Therefore, a
Red Flag Warning has been issued for portions of northwest
Colorado for this afternoon and evening where fuels are critical.

Even though we won`t be seeing any substantial precipitation from
this system, the entirety of the forecast area will experience
drastically cooler temperatures today. High temperatures this
afternoon will dip by 15 to 20 degrees across the north, 10 to 15
degrees across the central zones, and by close to 10 degrees in
the south relative to yesterday`s readings. This cooling trend
will continue into Sunday as colder air advects into the region in
post-frontal northwest-westerly flow aloft. High clouds will
increase Sunday morning as an upper level low maintains its
position over the Northern Rockies. Lower heights will begin to
sag into the Great Basin Sunday afternoon, potentially firing some
light showers over the Eastern Uintas. Shower coverage looks to
increase Sunday night as the base of the trough sinks further
south, though the higher elevations will continue to be favored.

.LONG TERM...(Monday through Friday)
Issued at 405 AM MDT Sat May 8 2021

To say describing the synoptic pattern for the Monday/Tuesday
timeframe is a pain would be an understatement. The aforementioned
stalled upper level trough will gradually push east Monday
morning. Based on QG plots, an area of enhanced lift will slide
over the northern tier of the forecast area as this eastward shift
occurs and a 700mb low treks overhead. Forecast soundings show
decent saturation of the profile into the afternoon hours as
available moisture (PWATs upwards of 0.40 inches) and subsequent
showers and storms increase throughout the day. The base of the
upper level trough will continue its slow progression Monday night
and into early Tuesday, allowing the unsettled conditions to
continue overnight. An exception will be across the western zones
as showers begin to taper off thanks to the transition to drier
northwesterly flow aloft. The GFS solution of a stronger, deeper
trough would support better shower coverage into Tuesday
afternoon, but will continue to favor the drier solution with this
morning`s package. Regardless, several more model runs will be
needed before confidence can improve on projected rain and
snowfall totals for the Western Slope. A secondary shortwave in
the northwesterly flow will brush the northern tier of the
forecast area on Tuesday night before weak midlevel ridging looks
to amplify for mid to late next week.

Due to the influence of the large, slow moving Pacific system,
expect temperatures to trend cooler than normal for both Monday
and Tuesday. As this system departs, a warming trend will ensue
with values sitting near to slightly above normal for midweek
before returning to well above seasonal to end the week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 551 AM MDT Sat May 8 2021

Mid and high level cloudiness will be moving through as a cold
front continues across western Colorado this morning. VFR
conditions should hold with this frontal passage as most lower
cigs and precipitation will be limited to the highest terrain.
Winds will once again flare up late this morning and through the
early evening hours. Gusts of 25 to 35 mph from the west to
northwest will be common over many of the western TAF sites. Winds
decrease after sunset with mainly clear skies moving in.

&&

.FIRE WEATHER...
Issued at 405 AM MDT Sat May 8 2021

A cold front will clear most of eastern Utah and western Colorado
by mid afternoon. This frontal passage will shift surface winds
to the Northwest for this afternoon. Minimal precipitation is
expected in the lower elevations with this front and dry air will
fill in behind it. As a result low afternoon humidity and gusty
northwest winds will create Red Flag conditions over portions of
northwest Colorado where fuels are susceptible. Localized critical
fire weather conditions could occur in southwest Colorado on
Sunday with some recovery in humidity to the North. Cooler and
wetter conditions arrive early next week.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from 1 PM this afternoon to 9 PM MDT this
     evening for COZ200-202-203.

UT...None.
&&

$$

SHORT TERM...MMS
LONG TERM...MMS
AVIATION...TGJT
FIRE WEATHER...15


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