Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 201521

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
921 AM MDT Sat May 20 2017

Issued at 919 AM MDT Sat May 20 2017

Updated to remove expired freeze warning headline.


.SHORT TERM...(Today through Sunday)
Issued at 351 AM MDT Sat May 20 2017

The storm which impacted the region during much of the past week
was spinning over the CO/NE/KS triple-point early this morning. A
shortwave trough on its southwest flank was generating clouds and
isolated light showers over the Gunnison Basin and western San
Juan Mountains early this morning. This disturbance will continue
to move quickly to the southeast and is expected to exit to the
southeast over the San Luis Valley around sunrise. Meanwhile,
clouds were filling in over northwest Colorado east of Craig.
Moisture constituting cloud cover appears to be largely residual,
and formative lift ostensibly provided by right entrance region of
the Polar Jet sliding south-southeastward over the area. Models,
to varying degrees, indicated the moisture and lift combined with
a modest orographic component will be sufficient to generate
isolated to scattered showers over the northern and portions of
the central mountains today.

Shower activity should decrease this evening but isn`t likely to
entirely dissipate during the night as a fairly vigorous shortwave
trough approaches from the northwest. This feature will push
across the area on Sunday bringing the likelihood of showers to
the northern mountains and a chance for precipitation across
adjacent valleys and central and southern mountains during the
afternoon. Snow levels will be higher than with this last storm,
so impacts to roadways should be less pronounced.

Temperatures will continue to moderate today and tonight and
should climb back to near normal for most locations Sunday

.LONG TERM...(Sunday night through Friday)
Issued at 351 AM MDT Sat May 20 2017

The broad upper level low will continue to spin over the far
northern CONUS, allowing for another disturbance or two to
circulate around the backside of the low. These weak embedded
waves will bring a quick shot of precipitation to the region with
activity generally being confined to the higher terrain. The
first, more substantial shortwave, will impact the area on Sunday
with the second disturbance clipping our northwestern CWA late
Monday and continuing into Tuesday. Impacts look to be minimal at
this time with just a couple inches of mountain snow expected.

By midday Tuesday a ridge of high pressure will be ushered in from
the west. Temperatures will jump back above normal with the lower
valleys climbing into the 80`s again. High pressure will remain
overhead through at least Wednesday before extended models begin
to diverge on the timing of what will come next. As another upper
level low deepens off the coast of western Canada the ridge should
begin to break down, opening the door for a more progressive
weather pattern with the return of cooler and potentially
unsettled conditions.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 351 AM MDT Sat May 20 2017

Residual moisture will fuel isolated showers over the higher
terrain, mainly during the afternoon and early evening. This
activity poses a slight threat to KRIL, KEGE and KASE. Should
showers occur at these locations, CIGS may briefly dip below ILS
breakpoints but VFR conditions will continue. Elsewhere, VFR
conditions will prevail and CIGS will remain above ILS
breakpoints. This is true for all TAF sites during the remainder
of the night.




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