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Area forecast discussion 
National Weather Service Grand Junction Colorado
226 PM MDT Friday Aug 22 2014

Short term...(tonight through Saturday night)
issued at 225 PM MDT Friday Aug 22 2014

A monsoonal moisture feed and an embedded shortwave trough will
continue to move over the area from south to north this evening. A
solid bank of middle and hi clouds will suppress convective
development over the eastern portions of the forecast area...
generally east of a line from Durango to Grand Junction to Meeker.
West of that line...far more sun is heating the ground and helping
thunderstorms to form as expected. The wave related cloud bank
will shift north and east this evening and the convection in the
clearer area will follow it...shifting from SW to NE.

While all that is happening...a significant upper trough will
move from the pacnw into the Great Basin. By midnight its cold
front will be over NE Utah and late tonight the front will weaken as
it drags across northwest Colorado. Saturday morningthe best cold advection
and moisture...with added support from the jet stream aloft...will
produce more widespread precipitation. Best areal coverage will be
north of Interstate 70. Northern portions of the will also be
about 10 degrees cooler Sat. By midafternoon the cold front will
reach the Continental Divide over northern Colorado and stretch back to
the SW over the San Juan Mountains. Moisture will be eroding
throughout the areal coverage of precipitation should decrease.
Saturday night...only remnant showers will persist over the
Continental Divide.

Long term...(sunday through friday)
issued at 225 PM MDT Friday Aug 22 2014

At the synoptic level...a seasonally unusual trough pattern
persists over the intermountain west into middle week. The 12z ec
trough passage timing has trended closer to the faster GFS...
still timed for Tuesday in the Wednesday in the ec.

Available moisture/precipitable water remains less than one inch
through Tuesday...limiting shower intensity and coverage. Showers
will favor the mountains... especially the northern mountains late
Sunday through Tuesday under a 60kt jet. Storm motion Sunday
through Tuesday will be to the NE at 25-30kts which also limit
shower duration but threaten strong outflow winds. Valleys to the
NE of mountain ranges could also have gusty outflow winds and
light showers. Temperatures will be near normal until trough
passage Tuesday or Wednesday...rising above normal late in the
week as the more usual Four-Corners ridge pattern returns. The
ridge looks quite dry for Thursday into Friday.


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1037 am MDT Friday Aug 22 2014

Monsoonal moisture will continue to flow into the area from the
south through the next 24 hours...mainly over western Colorado. Expect
periods of mountain obscuration over Colorado with numerous showers and
thunderstorms. Flight categories will likely fall into the MVFR
range due to heavy rain at the western Colorado taf sites and most
western Colorado airports. Stronger cells may drive visibility into the IFR
range with MVFR ceilings. Over eastern Utah...showers and thunderstorms
will be scattered with significantly less chance for Airport
impacts from thunderstorms. Showers and thunderstorms will
continue overnight with the focus shifting to the north.


Gjt watches/warnings/advisories...


Short term...cirrocumulus
long term...Joe

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