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FXUS65 KGJT 070609
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1209 AM MDT Sun Jun 7 2020

.UPDATE...
Issued at 810 PM MDT Sat Jun 6 2020

Winds have fallen well below advisory criteria of 45 mph.
Therefore, the wind advisory for today has been cancelled. Due to
latest guidance and our gridded forecast data showing wind gusts
reaching or exceeding 45 mph on Sunday in many lower elevations
of east- central to southeast Utah as well as western Colorado,
decided to issue a Wind Advisory for Sunday from noon till 9 pm
MDT.

UPDATE Issued at 720 PM MDT Sat Jun 6 2020

Despite recent moisture, conditions were quickly drying out behind
this trough passage with relative humidities dropping to the teens
and single digits in many areas across southeast Utah and
southwest Colorado. A few wildfires that developed in Mesa County
on the ridges surrounding the Grand Valley are continuing to burn
with quite an increase in acreage since yesterday due to the
strong winds due to showers and storms last evening and today.
Even though relative humidity looked to be a bit borderline on
either side of 15 percent across much of Fire Weather Zones 203,
winds look to be gusting in the 40s. Due to the presence of the
still burning wildfires and strong wind gusts, decided to add Fire
Weather Zone 203 to the Red Flag Warning for Sunday.

&&

.SHORT TERM...(Tonight through Sunday night)
Issued at 400 PM MDT Sat Jun 6 2020

The negative tilt mid-level shortwave trough was over northeast
Utah and northwest Colorado late this afternoon. Much of the
shower and thunderstorm activity associated with this feature has
shifted north and east of the forecast area. However, a mesoscale
convective vortex over northeast Utah continued to generate an
area of strong thunderstorms over extreme northwest Colorado.
Separately, an area weaker lingering moist convection continued
over the central mountains and adjacent valleys. Finally, on the
far southeastern edge of the forecast area showers and embedded
thunderstorms were hanging on over the ranges southeast of Pagosa
Springs.

The potential for additional flood producing, or severe storms
beyond 4 and 5 PM this afternoon respectively, is exceedingly
unlikely. Therefore, remaining Flash Flood Watches and the Severe
Thunderstorm Watch will be allowed to expire.

Subsidence and cooling on the back side of the trough will bring
showers and thunderstorms to diminish with only a few showers
lingering over the eastern Uinta Mountains and the Elkhead and
Park Mountains early this evening. However, the longwave mid-level
trough to the west pushes eastward across the Great Basin late
tonight. Moisture streaming northeastward ahead of the trough
begins to impinge on northeast Utah by midnight and it's likely
that scattered showers will develop over the eastern Uinta
Mountains and portions of the Uinta Basin from midnight through
sunrise Sunday.

The longwave trough continues to push east Sunday driving a
surface cold front ahead of it. Height packing and pressure
falls ahead of the system will bring breezy to windy conditions to
the region again Sunday. There is the potential that another Wind
Advisory may be need to be hoisted but will hold off on adding
another product to the diverse set already in place. Meanwhile,
difluent flow, mid-level upward forcing indicated in Q fields,
divergence at the jet level and low level convergence is expected
to bring numerous showers and embedded thunderstorms to much of
northeast Utah and extreme northwest Colorado, especially during
the afternoon. Doesn't appear this activity will generate the
severe weather seen today, though with strong flow aloft, cannot
rule out isolated severe outflow winds.

A jet streak on the flanks of the longwave trough slows the
eastward progression of the system Sunday night. As a result,
showers will continue into the evening north of the I-70 corridor
with a few embedded thunderstorms possible before largely
diminishing overnight as a dry slot begins to move over northwest
Colorado.

Cooler airmass over the area will keep temperatures subdued again
on Sunday with highs expected to be close to those experienced
today.

.LONG TERM...(Monday through Saturday)
Issued at 400 PM MDT Sat Jun 6 2020

The mid-level longwave trough eases over the forecast area from
Monday into Monday night. Moisture will be limited south of the
I-70 corridor, so little precipitation is expected over those
areas from Monday morning through Tuesday morning. Meanwhile, lift
and moisture concentrated to the north will continue to bring
scattered showers and afternoon thunderstorms. Showers linger over
the northern Colorado mountains in northwest flow before
subsidence brings in drying during the afternoon. The cold front
driven by this system brings unseasonably cold air into the region
and as a result, temperatures on Monday and Tuesday are expected
to run well below seasonal norms.

The airmass moderates under a mid-level ridge forming ahead of a
deepening longwave trough over the eastern Pacific. By Wednesday
temperatures return to near normal levels. Flow aloft shifts from
west to southwest later this week as the ridge amplifies and its
axis pushes east of the Continental Divide. In response to warm
air advection, temperatures jump to around 10 degrees above normal
for the latter part of the week. Models continued to hint at
moisture streaming northward from the Mexican Plateau as flow
becomes more southerly in response to a closed low forming off of
southern California. This surge of moisture brings the potential
for showers and thunderstorms along the southern and central
Colorado mountains along the Continental Divide Friday and
Saturday. Meanwhile, flow aloft begins to increase Saturday which
could lead to a resurgence in critical fire weather conditions.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1207 AM MDT Sun Jun 7 2020

Winds increase again later this morning into the afternoon with
gusts 30 to 40 kts and mostly dry conditions. Some shower
activity is possible across northeast Utah and northwest Colorado,
mainly affecting KVEL with VCSH.

&&

.FIRE WEATHER...
Issued at 720 PM MDT Sat Jun 6 2020

A deep trough to the west will bring another round of strong
southwest winds to the region on Sunday. Despite today's rain,
expect fine fuels will be dry enough to create critical fire
weather conditions for east-central to southeast Utah and
west-central to southwest Colorado Sunday afternoon/evening.
Decided to add Fire Weather Zone 203 to the Red Flag Warning as
well due to the presence of still burning wildfires despite recent
rainfall and strong wind gusts in the 40s expected, even though
the relative humidity here was a bit borderline. Similar
conditions are possible Monday, despite unseasonably cool
conditions. Cooler temperatures and less wind expected through
midweek before temperatures rise above normal for the latter part
of the week. Winds expected to increase again next Saturday with
critical fire weather conditions again become possible.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from noon today to 9 PM MDT this evening for
COZ203-207-290-292.

Wind Advisory from noon today to 9 PM MDT this evening for
COZ001-002-006>008-011-020-021.

UT...Red Flag Warning from noon today to 9 PM MDT this evening for
UTZ490-491.

Wind Advisory from noon today to 9 PM MDT this evening for
UTZ022-027>029.

&&

$$

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