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Area forecast discussion 
National Weather Service Grand Junction Colorado
1045 PM MDT Friday Apr 18 2014

Short term...(this evening through Saturday night)
issued at 336 PM MDT Friday Apr 18 2014

Winds have picked up this afternoon as expected and will continue
to be increased past sunset as a weather disturbance approaches
from the southwest. The main activity from this system is
currently affecting southern Arizona and heading north toward The
Four Corners. The short term rap and NAM models have done well in
forecasting the isolated showers this afternoon after the northern
San Juan and Elk Mountains. The possibility of isolated showers
and a possible strike of lightning will continue through midnight.
Model skew-ts across southwestern Colorado are showing a classic
'v' pattern which suggests strong outflow winds tonight from virga
and showers which do develop.

Just after midnight...a surge of moisture from the southwest is
expected to reach The Four Corners and continue northeast.
Scattered to numerous showers are expected with possible embedded
thunderstorms. Looks like there will be an area of rain/snow with
snow level starting near 8500 feet overnight moving northeast and
tapering off in coverage as it passes over the southwestern Colorado
mountains however...with precipitable waters well above normal at 0.50 to 0.70 inch
by noon Saturday...expecting scattered to numerous showers across
the County Warning Area Saturday afternoon with isolated/scattered thunderstorms
as well. With so much potential precipitation...storms that do
develop could pack a good punch of water. Snow level will rise to
near 10000 feet by noon so the winter snowpack is expected to
diminish...therefore small streams and creeks could rise quickly.
Use caution if traveling through the backcountry or traveling near
low-lying areas along small drainages. We appreciate any reports
of rising water.

Long term...(sunday through friday)
issued at 336 PM MDT Friday Apr 18 2014

Lingering moisture behind Saturday/S disturbance will allow isolated
to scattered showers and thunderstorms to develop over the mountains
during the afternoon. Helping this convection will be a weak wave
passing to our north...and daytime surface heating. While a few
mountain showers will again be possible Monday afternoon a downturn
is expected as a ridge passes overhead...and the next low pressure
trough approaches the Pacific northwest coast.

Models indicate the potential for a significant wind event on
Tuesday as this trough shifts inland and into the Great Basin. Also
an associated cold front will approach our forecast area from the
northwest late Tuesday-Tuesday night. Warming ahead of the front...and the
tightening gradient will produce warm...windy and dry conditions.
Models do show some some middle-high level moisture which may act to
dampen the winds. However model soundings show an inverted-v
signature...for the potential of virga or light high-based showers
which would greatly boost wind gusts. At this looks like
the cold front will push into the northwest corner around midnight
Tuesday night...then across most of the forecast area by late Wednesday
morning. This will keep the air mass unsettled through the
night...with strong wind gusts again developing along the far
southern border Wednesday morning and early afternoon. Since the bulk of
the upper level system and the associated moisture will remain to
our north...this will not be a big precipitation producer for our
area. A chance of showers will develop over the northern portion on
Wednesday behind the front...only isolated mountain showers are
expected in the south.

Then with pretty good agreement...the 12z model runs indicate a
ridge building over the region for Thursday and Friday.

After warming conditions early in the week...especially on
Tuesday...temperatures could drop by 15 or more degrees on Wednesday
and Thursday behind the front. Temperatures then warm again on Friday.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1045 PM MDT Friday Apr 18 2014

Western Colorado and eastern Utah will be stuck between systems
passing through the northern High Plains and lifting across
Arizona and New Mexico the next 24 hours. Currently moisture is
streaming northward...mainly in the form of middle and high
cloudiness. Dry air near the surface is preventing moisture from
getting into the valleys. Gusty winds...spotty showers or virga
will be possible over the higher terrain this evening. This will
change toward morning and especially tomorrow afternoon as lift
and instability increases. Showers will become widespread over the
mountains along with occasional obscuration of the terrain.
Valleys a bit more tricky as far as precipitation...but gusty
winds and isolated thunderstorms may impact forecast terminal
operations through much of the day.


Fire weather...
issued at 336 PM MDT Friday Apr 18 2014

As a large low pressure trough moves onshore over the Pacific
northwest on Tuesday...strong southwest flow will develop over
eastern Utah and western Colorado. This flow will mix into the
valleys by the afternoon and increase over the area as a cold front
associated with the trough approaches from the northwest. Ahead of
the front conditions will remain dry...especially over southwest
Colorado and southeast Utah where minimum relative humidity values
will likely drop below 15 percent below 8000 feet. Also the
strongest winds are expected across eastern Utah and southwest
Colorado. Therefore critical weather conditions will be possible
Tuesday afternoon in areas where fuels are dry. Models indicate that
the bulk of the energy and moisture associated with the trough will
remain north of the forecast area. Low relative humidity and gusty
west winds are expected over the far southern zones Wednesday


Gjt watches/warnings/advisories...


Short term...jam