Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181755
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1155 AM MDT WED MAY 18 2016

.UPDATE...
Issued at 703 AM MDT Wed May 18 2016

Local webcams show the fog having lifted near and around
Telluride. The ASOS now reporting 10 miles visibility with
ceilings at 7000 feet so cancelled the dense fog advisory.

UPDATE Issued at 538 AM MDT Wed May 18 2016

A Dense Fog Advisory has been issued for Telluride and surrounding
areas through 9 AM. Visibility has been reduced to one-quarter
mile at KTEX and CDOT webcams indicated the fog bank was extensive.

&&

.SHORT TERM...(Today through Thursday)
Issued at 423 AM MDT Wed May 18 2016

The storm center which has continued to bring unsettled weather to
the area moved to south-central Arizona overnight as models had
predicted. Latest radar and surface observations indicated that
showers had diminished over the area overnight, though it`s likely
that a few showers went undetected below the radar beam in the San
Juan, La Sal, and Abajo mountains.

The low begins to fill, evolving into an open wave as it shifts to
northwest New Mexico later today. Divergence aloft favors the
south and expect the bulk of the activity there as depicted by
models. Daytime warming will destabilize the airmass as in past
days, so expect thunderstorms to redevelop during the afternoon.
Though models appeared to be on track with this system they
continued to over forecast snow in the mountains with both GFS20
and NAM12 generating upwards of 18 inches of new snow by Thursday
evening. This hasn`t verified in earlier forecasts and am left to
conclude that convective influence is overdone while temperatures
haven`t been properly taken into account. Suspect 4 to 8 inches
with locally higher amounts are possible above 11,000 feet, but
impacts to roadways over the passes will be minimal. Consequently,
will not be issuing highlights for snow with this issuance.

Latest guidance showed showers largely diminishing overnight
tonight, then redeveloping Thursday afternoon. Showers and
thunderstorms will be fueled by residual moisture and instability
with little dynamic input.

Temperatures are expected to rise a few degrees in response to
weak mid-level warming today. However, temperatures will rise more
noticeably Thursday as 7h temperatures rise from near 4 degrees
celsius to around 8 degrees. As a result, Thursday`s highs should
return to normal, or a few degrees above seasonal norms.
Meanwhile, persistence best describes tonight`s forecast lows
which is right around normal for this time of year.

.LONG TERM...(Thursday night through Tuesday)
Issued at 423 AM MDT Wed May 18 2016

A ridge will build over the region Thursday night into Friday but
residual moisture expected to be sufficient to fuel afternoon and
evening showers and thunderstorms.

Meanwhile, a deep area of low pressure will drop down into the
Pacific northwest before becoming quasi-stationary. Models
continued to struggle with the positioning of the low so
confidence reduced. One thing that has remained consistent is
that this low will tighten the pressure gradient considerably
resulting in a breezy southwest winds across much of the Great
Basin. Eastern Utah and western Colorado can expect winds to pick
up Friday afternoon and to redevelop each afternoon through
Sunday. The best upper level support for this system looks to
stay to our north so expect some showers at times through Tuesday
but nothing too widespread.

Temperatures will rise to near, or a little above normal Friday
and Saturday before dropping a few degrees below seasonal norms
Sunday and into early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1151 AM MDT Wed May 18 2016

Some showers have formed over higher terrain as of 18z though no
lightning strikes reported yet. Do anticipate some thunderstorms
temporarily forming over mainly southern areas and included in
TAFs for MTJ...TEX...and DRO for this afternoon. Remaining
TAFS...outside of CNY and VEL...may also see some convection
though not sold on any storms moving overhead so vcts will do for
now. areas caught under the stronger cells will likely see gusts
of up to 30 mph and some brief mvfr/ifr thanks to heavier showers.
these should be fairly short in duration. conditions will improve
overnight though some mid to high level cigs may persist down
south.

&&

.HYDROLOGY...
Issued at 423 AM MDT Wed May 18 2016

Wet weather through midweek combined with rising temperatures
toward the end of the week are expected to drive river levels
gradually higher. In fact, over the next few weeks increased flows
will primarily be the result of melting snowpack. This will cause
rivers and streams to swell causing some streams to reach
bankfull. Use caution in and near swift currents.

&&

.GJT Watches/Warnings/Advisories...
CO...None.
UT...None.
&&

$$

UPDATE...TGR
SHORT TERM...NL
LONG TERM...NL/TGR
AVIATION...TGR
HYDROLOGY...TGJT



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