FXUS65 KGJT 190933

Area Forecast Discussion
National Weather Service Grand Junction CO
333 AM MDT Wed Jun 19 2019

.SHORT TERM...(Today through Thursday)
Issued at 301 AM MDT Wed Jun 19 2019

A couple of showers are lingering at this hour, quickly heading to
the southeast. By dawn, they will have shifted east of the
Continental Divide and IR satellite not showing much upstream so
that should be about it for precip. The rest of today looks to be
fairly quiet. An area of high pressure remains well off to the
west over the Pacific Ocean while our next weather maker will be
spinning over southwestern Canada. Available moisture will start
decreasing dropping back to more normal values which is around .5
inches. While most models want to keep the CWA dry, the NAMNEST
does indicate a slight chance for some showers just along the
Continental Divide and this can't be ruled out so a small sliver
or Pops resides in that area. The rest of the CWA will remain dry
as some high clouds drift overhead in the afternoon hours
especially north of I-70.

Thursday, the jet stream takes a noticeable dip southward which
will bring the center of the disturbance from Canada into Montana
and Idaho. While the low pressure center stays well to our our
north, favorable jet dynamics and instability will bring some
precip to areas north of I-70. Channelled vorticity will also move
through the mean flow providing lift along with the jet stream
aloft. As the base of the trough starts to swing down into the
Great Basin, QPF amounts look to increase for the same areas so if
models are to be believed, light precip Will begin late Thursday
afternoon and continue into Friday with showers and thunderstorm
chances increasing. Models have been fairly consistent over the
last few days so confidence quite high with this solution.

Finally, deep mixing is expected to occur Thursday which looks to
tap into some of the stronger winds aloft bringing some gusts of
25 to 35 mph to areas south of I-70. Nothing too drastic but
combined with low humidities and critical fuels, fire weather
concerns increase. More on that in the fire weather section below.

.LONG TERM...(Thursday night through Tuesday)
Issued at 301 AM MDT Wed Jun 19 2019

Showers and thunderstorms will continue north of the I-70
corridor on Friday as low pressure tracks southward into Utah.
Fast flow as well as cooler temperatures aloft will support some
stronger thunderstorm activity, possibly with a gusty wind and
small hail threat during the late afternoon hours when instability
and inverted-V soundings are maximized. By Saturday afternoon,
forecast guidance is in agreement showing low pressure near the
Utah-Colorado border. Unseasonably cold temperatures aloft are
forecast by all major global models but the timing of these colder
temperatures moving in has changed somewhat. The GFS now shows the
0-2C temps moving in around noon on Sunday while the EC shows the
temps moving through early Sunday morning. With plenty of
moisture remaining in the base of the trough, some early summer
snow is quite possible across all mountain ranges, especially in
the central and northern portions of the Colorado Rockies on
Saturday night into Sunday morning. While it is too early to
speculate on exact totals, 700mb temperatures in the
aforementioned range can certainly support snowfall as low as
10,000 feet...and possibly lower. Depending on the timing, some
light snow may accumulate on roadways before melting once the sun
rises. With that in mind, motorists planning travel over the
higher passes, as well as recreationalists planning to be in the
backcountry on Saturday into Sunday, should pay careful attention
to the forecast over the next few days. Keep that winter gear

Northwesterly flow keeps things cool and unsettled again on Sunday
morning and afternoon as this low pressure system slowly heads
eastward. Dry weather looks to return by early next week as
westerly zonal flow resumes over the Four Corners.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 301 AM MDT Wed Jun 19 2019

Broken clouds remain over the eastern half of the CWA but these
continue to move to the southeast. By daybreak, most of the denser
clouds will have either lifted or shifted eastward. Either way,
few to scattered skies will be the rule once the broken skies
clear. Some high clouds will increase over northern portions of
the CWA this afternoon but will pose no threat to aviators. Expect
some gusty surface winds this afternoon of 20 to 25kts at most
TAF sites. The usual for this time of year. Outside of that, VFR
conditions continue.


Issued at 230 PM MDT Tue Jun 18 2019

A weather system will drop southward into the central Rockies Thursday.
This system will bring an increase in wind speeds over eastern
Utah and western Colorado throughout the day. Low RH values are
expected as well, although RH values will be closer to 15% until
the afternoon hours. A combination of high wind gusts, low RH
values, and critical fuel levels has prompted a Fire Weather Watch
for possible Red Flag conditions on Thursday. Will keep the Fire
Weather Watch in place with this morning's package so as to not
confuse partners into thinking the Red Flag Warning is for today,
Wednesday, when it's actually for Thursday. Do anticipate upgrades
to Red Flag Warnings later on this afternoon and if not then,
certainly tonight.



CO...Fire Weather Watch from Thursday afternoon through Thursday
evening for COZ203-207-290-292.

UT...Fire Weather Watch from Thursday afternoon through Thursday
evening for UTZ490.



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