Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 221744
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1144 AM MDT MON AUG 22 2016

.SHORT TERM...(Today through Tuesday)
Issued at 314 AM MDT Mon Aug 22 2016

The old forecasting adage of "watch for the shortwave of the day"
applies both today and Tuesday. Broad low pressure will rest over
the western U.S. while a loosely organized shortwave trough over
AZ and NM slide north over the four corners and into central CO.
moisture will ride north with the shortwave. PWAT at KGJT is
projected to steadily increase toward the .80 inch range in the
NAM12 today. But dynamics are relatively weak with little wind
shear aloft. These conditions along with existing cloud cover
through the morning will mean a slow start to deep convection and
areal coverage will barely reach the numerous or widespread
category over the mountains. Local heavy rain under stronger
storms appears to be the main threat today. The shortwave will
slide east of the area by about midnight tonight.

Looking at Tuesday another shortwave trough starts off the day as
a closed 500 mb low over northern AZ. It fills to become an open
wave and moves over central CO by the end of the day. The NAM12
solution is stronger with this feature than the GFS20 and decide
to split the difference with pops and clouds.

.LONG TERM...(Tuesday Night through Sunday)
Issued at 350 PM MDT Sun Aug 21 2016

Models indicate that the moisture surge will peak on Tue. Also
the above mentioned Pacific low will reach the forecast area
during the afternoon. This combination should result in another
increase in late day showers and thunderstorms, both in areal
coverage and possibly in intensity. Heavy rain and small hail
will be possible, with precipitable water values near an inch.
Also, storms may be slow moving as steering will will stay on the
light side. The extra clouds and precipitation will keep
temperatures quite cool and well below normal through the day.

A modest drying trend will take place on Wednesday, only to
reverse again on Thursday. Therefore after a downturn in
convective activity Wed, showers and thunderstorms will again
increase on Thu and through the remainder of the forecast period.
As usual, the southern portion and the late day hours will be
favored. High temperatures will remain below normal, with lows
near normal.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1140 AM MDT Mon Aug 22 2016

Partly to mostly cloudy skies reside over the forecast area this
morning as mid to upper level moisture pushes into Eastern Utah
and Colorado. This moisture will result in afternoon showers and
thunderstorms which will persist into the evening hours. Expect
gusty and erratic winds in the vicinity of the showers and
thunderstorms, otherwise VFR conditions are expected to prevail.

&&

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

$$

SHORT TERM...CC
LONG TERM...EH
AVIATION...Larry


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