Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 291001
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
401 AM MDT Thu Jun 29 2017

.SHORT TERM...(Today through Friday)
Issued at 401 AM MDT Thu Jun 29 2017

Low level water vapor imagery channel and hand analysis seems to
indicate a weak frontal boundary settling across the central
Colorado Rockies back into S.Utah. A surface low was located along
the front near Blanding with much drier air remaining in place
near the 4 Corners where humidity is still in the lower teens.
North of this boundary some recovery of RH has occurred due to
cooler temperatures but the coolest remains just to our north and
will not really make a push through until tonight with main upper
trough passage. Main concern today remains fire weather related
with the humidity likely to fall again as good mixing occurs which
will kick up the wind gusts. Temperatures a bit cooler north of
the boundary by 3 to 5 degrees with minimal changes in the 4
corners region. Moisture still extremely limited but forcing from
the trough and the secondary cool push looks to favor our
northeast mountains late this afternoon and evening. In the south
the entrance region of the upper jet and channelized vorticity
near the stalled front may try and trigger some storms in the
southern hills. Confidence here very low so hardly mentioned in
grids but any storms/virga and associated outflows could affect
the bigger fire near Durango...so should be watched. Fairly
noticeable cool down on Friday as the upper trough swings through
the region. For the most part this will help eliminate widespread
critical fire weather conditions but isolated pockets will
remain...especially in the south where frontal boundary location
will help drive winds. Isolated storms also possible near this
boundary and narrow band of moisture aloft.


.LONG TERM...(Friday night through Wednesday)
Issued at 401 AM MDT Thu Jun 29 2017

A strong downstream blocking ridge over the Atlantic will keep
troughing over Great Lakes region going into the weekend. This
will allow another Pacific trough to swing across the Great Basin
before de-amplifying over the Rockies. This trough has been
trending a bit deeper and looks to affect our CWA by Sunday
afternoon. Prior to this however the cooler weather from Friday
will be pushed out building heights and ridging moves over the
Rockies. The front associated with the late week trough passage
looks to settle over northern NM. 310-315K theta surfaces suggest
moisture pooling near the front will be pulled back westward
through the lower terrain and then advected into our southern CWA
by Saturday afternoon. Forcing is weak but an embedded trough in
the southern stream will move into the 4 Corners region an
interact with afternoon instability. Coverage of showers will be
spotty and mainly over the southern hills Saturday afternoon.
Isolated pops attm and will watch this trend. Sunday with the main
trough the coverage may be a bit more spread out across the
western Colorado and northeast Utah hills. Moisture definitely not
over-impressive and we may see more wind than rain with many of
the showers and storms. High pressure than amplifies across the
Great Basin and Rockies. This is by no means the start of the
monsoon but a southern moisture tap will begin to saturate the
ridge and daily afternoon convection looks to be commence.
Confidence like pops low in the outer periods attm. Temperature
trends continue to rise under this ridge and should be well above
normal from Sunday onwards. Another benefit of the mositure tap
will be to push afternoon humidity values upward and ease critical
fire weather conditions.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 401 AM MDT Thu Jun 29 2017

The main concern again to aviation will be gusty afternoon winds
affecting landing and takeoff operations. Mountain top turbulence
may also be present with stronger jet stream level moving in
aloft. Hazy conditions due to smoke from regional fires will be
possible mainly the 4 Corners but local fire near Durango may
impact local vsbys near DRO. Otherwise VFR conditons will dominate
the forecast.


&&

.FIRE WEATHER...
Issued at 401 AM MDT Thu Jun 29 2017

Though a cool front boundary has passed through most of the
area...warm...dry and gusty conditions will develop again this
afternoon. Red Flag conditions will develop though sustained winds
may be a bit lower today widespread gusts at or above 25 mph are
expected during the peak heating hours. Another push of cooler air
arrives for Friday which will help limit the coverage of critical
fire weather conditions. Hot conditions continue beyond this but
it appears that moisture will slowly begin to creep into the
region and afternoon humidity could recover above critical levels.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from noon today to 8 PM MDT this evening for
     COZ200-202-203-207-290>295.

UT...Red Flag Warning from noon today to 8 PM MDT this evening for
     UTZ486-487-490-491.

&&

$$

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



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