Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 262149
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
349 PM MDT Mon Jun 26 2017

.SHORT TERM...(Tonight through Tuesday night)
Issued at 348 PM MDT Mon Jun 26 2017

Enough moisture and instability sneaking underneath the ridge of
high pressure has lended itself to a bit more thunderstorm
coverage than expected today. So far development has been confined
to the eastern Utah mountains and San Juans, with storms drifting
off the San Juans into the southern valleys. Not as much gusty
winds reported with storms yet, but small hail and brief heavy
rain have been reported. Hot and dry conditions are prevailing
elsewhere with high pressure remaining in control. Storm activity
should wane after sunset with mostly clear skies overnight.
However, smoke from the Brian Head wildfire in southwest Utah near
Cedar City will continue to settle back into the lower elevations
of southeast Utah and southwest Colorado, so introduced areas of
smoke back in the forecast for this evening through Tuesday
morning. Expect this smoke to mix out by late Tuesday morning as
the next disturbance approaches and moves through.

An upper low over British Columbia will track into Alberta and
eject a disturbance across eastern Utah and western Colorado late
Tuesday morning through Tuesday evening. A 75 kt jet will move
overhead with this disturbance with H5 winds increasing to 30 to
40 kts. Forecast soundings all support sufficient mixing to 500 mb
or higher allowing some of these stronger winds to reach the
surface. Coverage also looks more widespread with the latest
guidance so issued a Red Flag Warning for eastern Utah and
portions of western Colorado where these conditions look to be
met. See Fire Weather Discussion for more details. Some isolated
thunderstorms are also possible mainly over higher terrain, but
looks less than Monday/today as drier air moves through. Gusty
outflow winds and lightning would be the primary concerns with
stronger storms.

.LONG TERM...(Wednesday through Monday)
Issued at 348 PM MDT Mon Jun 26 2017

A stronger upper level jet streak of 90 kts will move through the
region on Wednesday, associated with another disturbance ejecting
out of the Alberta low. Forecast model soundings indicate
stronger mixing occurring in similar areas as Tuesday. There is a
bit more mid to upper level moisture up north which may inhibit
mixing there but otherwise, if this mixing occurs, critical fire
weather conditions would be met. Therefore, issued a Fire Weather
Watch for Wednesday for those areas. The back edge of the upper
level trough will move through Thursday with more moisture and
cloud cover, less wind and slightly cooler temperatures for a
quieter day weather wise. Despite cooler temperatures, daytime
highs will still be running a few degrees above normal.

High pressure will build back into the region for the latter half
of the week with dry weather and a warming trend through the
weekend. Another disturbance tries to break down the ridge late
Saturday into Sunday, but confidence on this is low due to model
discrepancy. Kept slight chance of storms mainly over higher
terrain with continued warm above normal temperatures and a mostly
dry forecast through Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1041 AM MDT Mon Jun 26 2017

VFR conditions will continue through the forecast period. A weak
frontal boundary will pass on Tuesday afternoon bringing a slight
uptick in westerly winds at all terminal locations.

&&

.FIRE WEATHER...
Issued at 348 PM MDT Mon Jun 26 2017

An upper level trough will move over the area on Tuesday with very
good mixing up to at least 500 mb or higher, which will allow
stronger winds to reach the surface. Coverage looks more
widespread than previous model runs with sufficient mixing in most
areas, so Red Flag Warning has been issued for Tuesday for all of
eastern Utah and portions of western Colorado (excluding the
higher divide areas) where fuels remain critical. Forecast model
soundings would seem to indicate strong mixing of these winds
whereas MOS guidance may not be as representative and underdone,
as has been the case many times in the past.

On Wednesday, a second and stronger jet streak will move over the
region and if mixing remains good, these higher wind speeds may be
tapped and reach the surface causing another day of critical fire
weather. Therefore, issued a Fire Weather Watch for most areas on
Wednesday.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from 11 AM to 8 PM MDT Tuesday for COZ200-202-
     203-207-290>292-294.

     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for COZ200-202-203-207-290-291-294.

UT...Red Flag Warning from 11 AM to 8 PM MDT Tuesday for UTZ486-487-
     490-491.

     Fire Weather Watch from Wednesday afternoon through Wednesday
     evening for UTZ486-487-490-491.

&&

$$

SHORT TERM...MDA
LONG TERM...MDA
AVIATION...MAC
FIRE WEATHER...MDA


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