Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 222152
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
352 PM MDT Thu Jun 22 2017

.SHORT TERM...(Tonight through Friday night)
Issued at 202 PM MDT Thu Jun 22 2017

The primary forecast challenge this evening remains handling
convective trends and wind gusts along and north of the I-70
corridor. A weak trough aloft, most readily seen as a diffuse
gradient in 700mb temperatures, remains to the north along the
CO/UT border today. This boundary will gradually sag southward
before heading east overnight and into Friday morning. PoPs were
bumped upward along the Roan and Tavaputs into the Flat Tops this
afternoon, and CAM guidance continues to indicate that current
showers/storms will persist through at least 03z before
dissipating along the Continental Divide. Winds have picked up
across a few areas this afternoon, some in association with dry
thunderstorm outflow boundaries. These stronger winds will also
persist through the early evening and the Fire Weather headlines
remain on track.

Overnight temperatures are expected to be notably cooler than in
past nights throughout much of eastern Utah and western Colorado
as the 700mb thermal gradient passes through. Some cloud cover
will linger as well overnight into Friday morning. Forecast
soundings do indicate that most areas should decouple and winds
will not be an issue overnight.

Friday will turn out mostly sunny and we will shave around 5 to 8
degrees off of our afternoon high temperatures. Wind flow will
generally be northwesterly behind the departing trough, with only
a few afternoon cumulus clouds expected in the higher terrain
along the Continental Divide.

.LONG TERM...(Saturday through Thursday)
Issued at 202 PM MDT Thu Jun 22 2017

The weekend forecast remains on track with dry west to
northwesterly flow in place and temperatures about 5 degrees above
normal as the southwestern ridge strengthens. The ridge axis will
pass sometime Monday evening with a few isolated dry thunderstorms
returning to the forecast by that timeframe. The GFS continues to
indicate the potential for another trough moving into the western
CONUS by Wednesday/Thursday. This system is much drier and flatter
than in yesterday`s model cycles however. Still, an uptick in wind
speeds may affect central and northern Utah/Colorado late on
Tuesday and through the day Wednesday. The ECMWF indicates a much
weaker gradient over the region with zonal flow persisting, so
confidence remains low to medium beyond the Day 6 timeframe.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1145 AM MDT Thu Jun 22 2017

Our morning sounding today looks a lot like yesterday`s...which
leads us to believe that we could be in for strong downdrafts (60
kts potentially) again this afternoon. Unfortunately, trying to
pinpoint where these will happen is near impossible, but east
central Utah (Tavaputs to Moab) and west central Colorado
(Bookcliffs to as far south as the Gunnison Basin) looks most
likely. Trying to indicate this threat in the TAFs is difficult,
but added TEMPOS in to show the highest likelihood time frames.
Otherwise, a few showers and thunderstorms here and there. The
smoke noticably in the air tonight is expected to clear late this
afternoon and this evening from north to south. The Four Corners
valleys may see some smoke settle into the valleys. Conditions are
expected to remain VFR over the next 24 hours...except for an
isolated wind gusts that may blow dust up and reduce visibility
temporarily.


&&

.FIRE WEATHER...
Issued at 202 PM MDT Thu Jun 22 2017

A weak trough is expected to pass over and just north of the Four Corners
this afternoon. Winds should increase in intensity this afternoon and the
gusty winds near 20-25 mph will last into the early evening hours. Fire
weather conditions will be critical as RH values will be well below 15%
threshold values. An isolated dry thunderstorm is also not out of the
question through the evening as the trough swings through, however the
areal coverage of thunderstorms will be mostly limited to the Roan and
Tavaputs areas as well as the Continental Divide. Dry northwest flow is
still expected to move in on Friday and last through the weekend. Winds
will be lighter and Fire Weather thresholds are not expected to be met
through the weekend.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning until 10 PM MDT this evening for COZ203-207-290-
     292.

     Heat Advisory until 10 PM MDT this evening for COZ006.

UT...Red Flag Warning until 10 PM MDT this evening for UTZ486-487-490-
     491.

     Heat Advisory until 10 PM MDT this evening for UTZ022-027-029.

&&

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...JAM
FIRE WEATHER...TGJT



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