683 
FXUS65 KGJT 070515
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1115 PM MDT Fri May 6 2022

.UPDATE...
Issued at 940 PM MDT Fri May 6 2022

After assessing the latest model guidance, which included the 
NBM/NBM 4.1, the HREF and NAM/NAMnest/HRRR bufkit soundings, 
decided to expand the Wind Advisory northward to include UTZ027, 
COZ020, COZ011, COZ006, COZ007 and COZ008. At the surface, a 
modestly strong cold front will be sliding into the northwestern 
portion of the CWA Saturday afternoon and evening. This front will
be tied to strong dynamical forcing with a negatively titled 
shortwave and robust 700-500mb frontogenesis aloft. Ahead of the 
front, deep boundary layer mixing will readily tap into a ~45kt 
southwesterly 700mb jet. Combined with the likely development of
virga... and an extremely dry subcloud layer (as evidenced by
progged inverted V signatures)... the potential for wind gusts up
to 50 mph exists for just about all valley locations along and
south of the I-70 corridor. With all of that said, clouds will be
increasing somewhat tomorrow afternoon and that could limit
mixing and the wind potential. It's certainly a failure point
that's in play. However, progged average downward momentum 
transfer values of 35 to 45kt in addition to HREF ensemble max
gusts of 40 to 55 mph for the southern two thirds of the forecast
area could not be ignored. Overall, the strongest winds will occur
between 2 and 8 PM and will diminish rapidly after sunset.

&&

.SHORT TERM...(Tonight through Saturday night)
Issued at 320 PM MDT Fri May 6 2022

Mixing through a deep atmospheric boundary layer has tapped into 
strong winds aloft, forcing gusty winds down to surface floors. 
The core of an upper-level jet is positioned just north of the 
CWA, with zonal flow draped across the entire region. Gusts of 25 
to 35 mph have been reported across the Four Corners region, with 
gusts around 40 mph for northern valley floors. Northern zones lie
in closer proximity to said jet, and thus have stronger winds to 
tap into. That being said, exposed desert floors across southwest 
Colorado have little friction upstream to slow down these westerly
winds from whipping across the earth's surface. The rest of this 
evening will continue to blow, until mixing with strong winds 
aloft is capped by steep surface inversions shortly after sunset.

Winds start to turn from the southwest tonight, as a mid-level low 
digs into the PacNW. In response, lower heights nudged southward 
and tighten the pressure gradient aloft. Another blustery day is 
in store for the West Slope thanks to a series of atmospheric 
features at play. The broad trough axis nudges east throughout 
the day, carrying a cold front across the northern zones. 
Moisture, instability and lift via a cold front (and mountains) 
will trigger convective activity Saturday afternoon/evening. The 
frontal boundary appears to stall along or just north of the I-70 
corridor, limiting any moisture from reaching southern valleys 
and confining storms generally to the northern and central 
mountains. Winds ahead and along the frontal boundary will 
generally gust between 25 to 35 mph. In addition, expect to see 
some high base storms develop with virga and/or outflow winds 
locally enhancing surface gusts. 

Shifting focus to our southern regions; a 700mb jet, preceding 
the wind core upstairs, will drape directly over the Four Corners
region. These areas will maintain a deep mixing layer and easily 
tap into enhanced low-level winds. Surface winds ramp up late 
morning to 20 to 30 mph with gusts up to 50 mph possible in the 
afternoon. Therefore, have included a Wind Advisory for southeast 
Utah and southwest Colorado from noon to 9 PM MDT. Thanks to the 
low-level jet, expect strong winds to persist across higher 
terrain overnight. 

The cold front will bring a dip in highs tomorrow across 
northeast Utah and northwest Colorado. However, the gradient 
slowly swings in the other direction as you move south. Temps in
the 80's to low 90's are forecast for desert valleys.

.LONG TERM...(Sunday through Friday)
Issued at 320 PM MDT Fri May 6 2022

Models were in good agreement with the first half of the medium
range periods, though consistency degrades in the later periods 
beyond Wednesday of next week. Cluster analyses indicated a 
persistent deep and broad mid-level long wave trough over the West
through Wednesday. Strong southwest flow aloft to the core of the
trough is expected to mix to the surface during the daylight 
hours generating windy conditions across much of the forecast area
each day. Week disturbances moving beneath the jet flowing 
northeastward across northeast Utah and northwest Colorado are 
expected to generated scattered showers and a few embedded 
thunderstorms across those areas Sunday into Monday. This activity
is expected to bring light accumulations to the northern 
mountains with the highest peaks of the Park Range favored. Warm 
air advection in the southwest flow is expected to bring warmer 
than normal temperatures with highs running around 10 degrees 
above normal Sunday and Monday.

Dry, windy and warmer than normal weather is expected Tuesday and
Wednesday as the mid-level trough over the West sharpens and flow
draws drier, more southerly flow. The latter part of the week is 
less certain as EOF (empirical orthogonal function) fields
depicted a good deal of variability with respect to position and
depth of the trough beyond the middle of next week. However, 
despite differences, all operational models indicated a closed 
low over the Southwest will lift northeastward across the region 
Thursday bringing scattered showers over the higher elevations 
with the north again favored along with more isolated activity 
across the lower elevations. A cold front associated with this 
system will bring around 10 degrees of cooling yielding daytime 
highs Thursday and Friday near or a little below normal for this 
time of year.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1112 PM MDT Fri May 6 2022

Gusts of 30 to 50 mph will be common over much of the area by 
early afternoon. Blowing dust could create some reduction of 
visibility and lead to MVFR conditions in isolated areas. 
Scattered showers are possible across the northern sites in the
evening, which could drop categories and cause gusty winds. 

&&

.FIRE WEATHER...
Issued at 320 PM MDT Fri May 6 2022

Gusty conditions will be a daily recurrence through the forecast 
period, with minimal moisture available for RH recovery. Another 
system will turn winds to the southwest tonight, intensifying 
winds overhead. As such, daily mixing will begin to transport 
strong winds to the surface by mid morning and widespread critical
fire weather conditions will be met across the southern zones. 
Northern areas will also experience gusty winds, though the source
will be tied to a weak front and afternoon convection. Unfortunately,
the front stalls along the I-70 corridor, confining moisture from
reaching southern valleys tomorrow night. 

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Wind Advisory from noon to 9 PM MDT Saturday for COZ006>008-011-
     020>022.

     Red Flag Warning from noon to 9 PM MDT Saturday for COZ207-290-
     292-295.

     Red Flag Warning from 11 AM to 10 PM MDT Sunday for COZ207-290-
     292-295.

UT...Wind Advisory from noon to 9 PM MDT Saturday for UTZ022-027-029.

&&

$$

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