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Area forecast discussion 
National Weather Service Grand Junction Colorado
444 PM MDT Friday Aug 29 2014

Short term...(tonight through Saturday night)
issued at 256 PM MDT Friday Aug 29 2014

The short-lived ridge of high pressure stays over the region until
about midnight tonight...then a weak upper level trough
approaches eastern Utah by Saturday morning. This will shift flow
to the southwest and retain the available moisture over the area.
Moderate divergence aloft of 50kt stays over the region over the
next 24 hours then increases Saturday evening as the nose of a
60kt 300 mb jet reaches into northern Utah and Colorado. This combined
with a 500 mb vorticity maximum swinging into the forecast region in the late
afternoon will help to fire off scattered showers and
thunderstorms mainly north of I-70 late Saturday afternoon and
into the evening. Increased probability of precipitation in the valley to reach a slight
chance of precipitation for Saturday afternoon.

Long term...(sunday through friday)
issued at 256 PM MDT Friday Aug 29 2014

The nose of an 80kt 300mb jet will Rake across northeast Utah and
northwest Colorado on sun as the southern extent of the latest trough
brushes our forecast area. An associated cold front will dip into
the area from the north-northwest by daybreak...then sag
southeast through the day. This front will make it to around the
central Divide area before shifting east in the afternoon. As a
result the chance for showers and thunderstorms initially confined
mostly to the northern edge will spread into the central Divide
mountains by late morning and afternoon. The 12z model runs have
indicated the front will push a little farther south on our side
of The Divide compared to yesterday's runs...and have likewise
painted the quantitative precipitation forecast farther south. This seems reasonable and so have
made sure that there is a chance of showers and thunderstorms in
the central Colorado mountains...and a slight chance in the San Juans.
This system quickly shifts east by early evening.

Models show another weaker wave will brush the far north on Monday.
The main effects for our forecast area will be breezy conditions
Monday afternoon...mainly over the north. Warmer and drier conditions
are expected through most of the work week as high pressure
dominates the southern tier states. By Thursday the flow will become
southwest and increase as the next Pacific trough strengthens off
the coast. This southwest flow may open up the door for a return
of subtropical moisture into the area. Therefore...the chance of
diurnal and terrain based showers and thunderstorms will increase
Thursday and Friday.

After a cool morning on Monday...temperatures will warm to around
normal or a little above by midweek.


Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 444 PM MDT Friday Aug 29 2014

Isolated short-lived thunderstorms will continue over the
mountains through 09z before diminishing by midnight. This
activity is unlikely to impact area taf sites so expect no
interruption to VFR conditions through 18z/Sat. Afternoon heating
will bring another round of thunderstorms to the high country
Saturday afternoon.


Gjt watches/warnings/advisories...




Short term...jam
long layers

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