Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 290311
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
911 PM MDT Sat May 28 2022

.UPDATE...
Issued at 911 PM MDT Sat May 28 2022

Relative humidity recovery is in full effect with wind gusts also
lessening for more than 50 percent of the fire weather zones.
Therefore, the Red Flag Warning for today has been cancelled.
Some localized conditions remain possible for the next hour or two
but overall, relative humidity is on the rise above 15 percent
and wind gusts are lessening below the 25 mph gust threshold.

Also, let the wind advisory expire on time at 8 pm this evening as
winds have lessened below the 45 mph gust threshold. Gusts in the
20s and 30s are still occurring in some areas but should lessen
overnight. Speaking of wind, based on the latest guidance, decided
to issue a Wind Advisory for Sunday afternoon and evening for the
lower elevations of southeast Utah and southwest Colorado, where
gusts in the 35 to 50 mph range are expected. Based on what
happened today, despite cloud cover, the majority of the lower
valleys hit wind advisory criteria with gusts exceeding 45 mph at
times. So expect more of the same across the Four Corners where
the jet will be positioned and better mixing should occur.

&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 405 PM MDT Sat May 28 2022

Strong southwest winds, in some cases aided by showers or virga,
developed over the region late this morning and have continued
through the afternoon. Meanwhile, along and south of the I-70
corridor, those winds combined with dry vegetation and low
relative humidity have brought critical fire weather conditions to
the area. The pressure gradient at the surface and aloft will
remain strong south of the cool front being driven southward
across northeast Utah and northwest Colorado this afternoon.
Therefore, Wind Advisories and Red Flag Warnings will continue
through 8 and 10 PM this evening, respectively.

Showers trailing the front will spread southward overnight as the
trough over the West deepens over the Great Basin. Decent mid-
level and jet level lift is indicated across the northern two-
thirds of the forecast area tonight which will drive this
precipitation. Snow will fall over the higher peaks tonight with
snow levels hovering at the 10 Kft level and higher. The front
washes out during the night according to all operational runs. Due
to clouds and adiabatic warming associated with precipitation
productions, overnight lows will be pretty mild as previously
forecast.

On Sunday, the trough over the Great Basin deepens further and
shifts eastward driving another cold front southward across the
northern half of the forecast area during the day. Meanwhile,
winds aloft will remain quite strong and lapse rates will steepen
as cooling occurs at the 500 mb level. CAPE is expected to range
from 750 to 1000 J/kg across the north with decent straight line
shear. This has prompted SPC to put the northern zones in the
marginal threat area for thunderstorms with the primary threat
being strong winds. HRRR and NSSL-WRF showed bowing structures
which seemed to fit with this scenario. Meanwhile, milder, drier
and continued breezy/windy conditions across portions of southwest
Colorado are expected to bring another round of a critical fire
weather conditions. Winds aren`t expected to be as strong as those
recorded today, so will not issue Wind Advisories for Sunday with
this package. Showers with scattered thunderstorms are expected
to be widespread over the mountains and areas along and north of
the I-70 corridor. Significantly cooler temperatures are expected
under these conditions, though not to the same degree across the
south.

Showers continue across the northern two-thirds of the forecast
area Sunday, but will be decreasing as the night progresses.
Meanwhile, the trough moves overhead and the front drops south of
the UT/CO borders. As a result, overnight lows will be much
cooler, though the threat of a freeze in the valleys is presently
low. Meanwhile, snow will continue in the higher reaches of the
mountains, however accumulations at and below pass level are
expected to be pretty light with melting limiting impacts.

.LONG TERM...(Monday through Saturday)
Issued at 405 PM MDT Sat May 28 2022

Unsettled and cooler than normal weather is likely to start off
the long term period as a large and broad trough remains parked
over the western CONUS. Several vortices embedded within the
parent trough will rotate through the northern Four Corners Monday
through Wednesday. The cold air aloft, as evidenced by 500mb
temperatures near -20C, combined with the strong late May sun
angle will produce steep lapse rates and marginal instability each
afternoon. This will result in a fair amount of clouds and
showers, especially over the higher terrain along the Continental
Divide and in the adjacent northern valleys. Snow levels will
start off around 8,500 feet Monday afternoon and will rise to over
10,000 feet by the same time on Wednesday. Additional snowfall
amounts during this period aren`t looking particularly impressive
with perhaps a trace up to a few inches possible way up high.
Rainfall amounts down low won`t add up to much either.

Outside of the higher terrain and higher valleys, mainly dry
weather is expected with just low odds of a brief sprinkle here
and there. Temperatures are favored to be quite cool for this time
of year. Highs are likely to be roughly 10 to 20 degrees below
normal on Monday and 5 to 15 degrees below normal on Tuesday.
Temperatures start to warm up on Wednesday as the parent trough
exits stage right, but highs will still skew slightly below
average. Given the higher humidity and lower temperatures, any
fire weather concerns are expected to be confined to near the
Colorado and New Mexico border, if anywhere.

The last shortwave on the backside of the now departed trough is
progged by ensembles to lift out of our CWA Wednesday into
Thursday. Beyond that, WPC ensemble clusters are in near
unanimous agreement that a strong ridge of high pressure builds
in over the Great Basin and Four Corners to round out the week.
Underneath this ridge, expect a return to drier and much warmer
than normal conditions under mostly sunny skies. Afternoon breezes
will need to be monitored for potential critical fire weather,
but winds should be lighter underneath the ridge. That, in turn,
should keep conditions fairly localized.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 606 PM MDT Sat May 28 2022

Southwest winds will continue to gust in the 25 to 35 kt range
with some sites gusting up to 40 to 50 kts at times. Scattered to
broken cloud cover is still working across the area and is
expected to increase in coverage overnight with showers moving
into the northwest portions of the area as the cold front
approaches. VCSH is possible after 06Z with prevailing showers
after 15Z Sunday. CIGS should remain above ILS breakpoints until
after 15Z when prevailing showers enter the picture, especially
across the north and higher elevation sites were better chances of
wetting rain exist. Isolated to scattered thunderstorms are also
expected by Sunday afternoon, some of which could be strong.
Erratic gusty outflow winds seem to be the primary concern,
especially in the lower elevations where chance of wetting rain is
lower.


&&

.FIRE WEATHER...
Issued at 405 PM MDT Sat May 28 2022

A strong cold front arrives tonight and will bring an increasing
risk for showers and thunderstorms. Humidity levels will be
rising behind the front, decreasing the fire weather risk across
the north. The front is expected to push into the Four Corners
area Sunday. Continued strong winds and low relative humidity
ahead of the front is expected to result in additional fire
weather concerns for portions of southwest Colorado. Therefore,
the Fire Weather Watch has been upgraded to a Red Flag Warning for
Colorado fire weather zones 207 below 6500 feet and 290. By
Monday, the fire weather risk shifts primarily towards the New
Mexico state line.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Wind Advisory from noon to 9 PM MDT Sunday for COZ020>022.

     Red Flag Warning from noon to 10 PM MDT Sunday for COZ207-290.

UT...Wind Advisory from noon to 9 PM MDT Sunday for UTZ022-029.

&&

$$

UPDATE...MDA
SHORT TERM...NL
LONG TERM...MDM
AVIATION...MDA
FIRE WEATHER...TGJT


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