Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 281712
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1112 AM MDT TUE JUN 28 2016

.SHORT TERM...(Today through Wednesday)
Issued at 405 AM MDT Tue Jun 28 2016

High pressure will remain centered over the area through midweek
and beyond. This feature has largely brought hot and relatively
dry conditions to the area over the past several days. However,
models indicated that`s about to change.

Deep monsoon moisture poised to the south over Arizona and New
Mexico is shown to creep northward beneath the ridge and over the
Four Corners region beginning today. Precipitable water values
will approach the 1 inch mark along the border of southeast Utah
and southwest Colorado late this afternoon. Elevated moisture will
feed increased shower and thunderstorm activity over the San Juan
La Sal, and Abajo mountains with more isolated activity over the
central and northern mountains. Initial storms will be high based
as the sub-cloud layer will be dry at the outset producing outflow
wind gusts to 35 to 40 MPH. However, storm characteristics will
change later in the day and into the evening as moisture works
downward causing some storms to generate localized heavy rain.
Though higher terrain will be favored, some storms will drift over
adjacent valleys from late afternoon into the evening.

Diurnal cooling will cause moist convection to decrease late in
the evening with just a few showers lingering later in the night.
However, it appears the forecast area will see a sharp uptick in
thunderstorm activity Wednesday as an inverted trough now over the
Las Vegas area swings north, then eastward around the periphery
of the high pressure center. Models indicated this sheared
disturbance will arrive over the area around peak heating which,
when combined with deepening moisture, should bring scattered to
numerous showers and thunderstorms to much of the area. Moisture
will arrive too late across Colorado`s northwest plateau, so
coverage likely to be more isolated. Strong outflow winds and
localized heavy rain will be the main threat posed by storms.

Temperatures will remain hot across the northern and central
portion of the forecast area today as clouds and showers will be
less prevalent. The opposite will be true across the south. Except
for a modest increase across the south, overnight lows will remain
near persistence and pretty close to normal. Daytime highs
Wednesday will fall across the entire forecast area in response
to increased cloud cover, showers and thunderstorms.

.LONG TERM...(Wednesday night through Monday)
Issued at 405 AM MDT Tue Jun 28 2016

Wednesday night storm and shower coverage will remain high as
sheared dynamics has increased moisture to work with. In fact,
this may be the most active period with precip water values
approaching 1.25 inches in east-central Utah along with dynamical
support. Gusty storm-produced winds may become widespread over the
southern and central zones. Boundary interaction should keep
storms going into and through Thursday.

Friday, deep moisture remains in place but upper-level forcing is
lacking so scattered storms and showers will form mainly with and
beyond afternoon heating.

Temperatures will be shaved under the clouds and showers Wednesday
through Friday, but dewpoints will climb into the mid 40s to mid
50s making for uncomfortable, mucky conditions. Evaporative
coolers will not produce much cooling.

Saturday-Monday, the ridge is flattened by energy moving through
the northern Rockies. Available moisture is pushed to the east in
a drier west flow. Daytime temperatures to be near normal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1112 AM MDT Tue Jun 28 2016

VFR conditions are expected to prevail over the next 24 hours at
TAF sites with the exception of KDRO, KTEX, and potentially KASE.
Moisture is increasing from the south, and will continue to do so
over the next few days. Storms through about 22z are expected to
be wind-dominant with gusts to 45 kts possible. After this time,
mod to heavy rain possible with stronger storms. ILS breakpoints
will be reached this evening in the heavier showers and storms.
Some storms may continue through the overnight hours, but will
pick up again in coverage after 17z Wednesday.

&&

.FIRE WEATHER...
Issued at 405 AM MDT Tue Jun 28 2016

A moisture surge into the Four Corners will initially produce high
based thunderstorms producing dry lightning and locally gusty
outflow winds. Since most storms are expected to be of the dry
variety a Red Flag Warning has been issued for UT fire zones 490
and 491. Though moisture depth is projected to be greater over SW
Colorado, the potential for dry lightning appears high enough to
warrant Red Flag Warning for CO fire zone 207.

The latest forecast still shows portions of Colorado zone 200 may
be close to the wind and RH criteria for critical fire weather
conditions this afternoon. However, models suggest these
conditions will be brief and localized. Therefore, will not expand
warnings into the north today.

&&

.HYDROLOGY...
Issued at 405 AM MDT Tue Jun 28 2016

Releases from area reservoirs and management of water diversions
will likely add to flow in some rivers and streams. As a result,
waterways across the area will continue to run high, fast, and
cold through the coming weekend. Stay advised of the latest river
forecasts by visiting our website at weather.gov/gjt.

&&

.GJT Watches/Warnings/Advisories...
CO...Red Flag Warning until 8 PM MDT this evening for COZ207.

UT...Red Flag Warning until 8 PM MDT this evening for UTZ491.

&&

$$

SHORT TERM...NL
LONG TERM...JOE
AVIATION...JAM
FIRE WEATHER...NL/JOE
HYDROLOGY...AS



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