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Area forecast discussion 
National Weather Service Grand Junction Colorado
939 PM MDT Sat Apr 25 2015

Update...
issued at 556 PM MDT Sat Apr 25 2015

Few adjustments to pop grids as showers continue to expand in
coverage across the West Slope. Expect the showers and
thunderstorms to continue through about 2 am...before diminishing
in areal coverage as we push toward sunrise. Hrrr and NAM both
leaning toward this solution. However...another round still in
store for most of the forecast area later Sunday as the low passes
to our south and heads east to Albuquerque Sunday afternoon.

&&

Short term...(tonight through Sunday night)
issued at 343 PM MDT Sat Apr 25 2015

Daytime heating combined with 500 to 1000j of cape this afternoon is
producing thunderstorms in eastern Utah and western Colorado in
partly cloudy skies ahead of the next cloud shield currently over
Utah. Periods of moderate to heavy rain are expected with these
thunderstorms...as well as small hail...frequent lightning...and
gusty winds. The approaching trough and cold front will increase
southwesterly winds and precipitation this evening. By midnight
tonight the front will be reaching central Utah and then eastern
Utah by the early morning hours. Expect periods of showers and
thunderstorms throughout the night.

Southern portion of the splitting trough forms a closed low just
south of The Four Corners by midday Sunday with precipitation
expected to be widespread across the forecast area. Southerly flow
at mountaintop level Sunday morning becomes east to northeast Sunday
afternoon as the 700 mb low consolidates along the Colorado/nm border.
Area of upper divergence develops over the central areas as the
wraparound flow north of the low encounters the split trough axis
pushing in from Utah. This couplet of upper divergence and low
level moisture convergence should aid precipitation. Q-g fields
show increasing subsidence Sunday night but moist low level north
to northeast flow should keep some snow going on favored slopes
Sunday night.

Upgraded the Winter Storm Watch to a late-season impacted-based
Winter Storm Warning for elevations above 9000 feet beginning at
midnight tonight for 5-10 inches of Snow. Mountain passes the most
affected. Added the Abajo/La Sal Mountains in southeast Utah to the warning for
4-8 inches. Also put The Flat Tops and Gore/Elk Mountains in a winter
advisory above 9000 feet. Likely to see snow below 9000 feet at
times but accumulations and impact will be less.

Cooler air could push low temperatures down near freezing in the
Cortez and Durango areas late Sunday night for a concern to Orchard
and vineyards in those areas.

Long term...(monday through saturday)
issued at 343 PM MDT Sat Apr 25 2015

Models are consistent moving the closed southwest low across northern Texas
and okla Monday and Monday night. Moisture in the northeast flow
wrapping back around the low will keep a chance of showers mainly
over the western Colorado mountains Monday as drier air slowly works in from the
west.

A positive-tilted upper ridge pushes into the Great Basin Tuesday and
overhead on Wednesday. This ridge then becomes the dominant weather
feature until Friday...when a developing West Coast trough shifts the
ridge eastward. A warming trend will push daytime temperatures above normal
Wed-Fri. As the ridge shifts east...southwest winds should pick up
Thursday and Friday in the favored areas of eastern Utah and northwest Colorado. Lingering
moisture and afternoon heating will keep a low chance of showers
over the mountains Tue-Thu...but most areas should be dry. The chance
of mountain showers begins to increase Friday and Sat as the West Coast
trough develops.

&&

Aviation...(for the 06z tafs through 06z Sunday night)
issued at 934 PM MDT Sat Apr 25 2015

Flight conditions will continue in the MVFR and IFR range at most
taf sites through Sunday. A strengthening storm centered over
western Arizona will continue moving east tonight through Sunday and
reach New Mexico by Sunday afternoon. Widespread rain and snow
showers along with isolated thunderstorms will continue across all
of eastern Utah and western Colorado through this period. Expect
snow levels to drop as low as 7500 feet at times. Mountains will
be obscured through the period. There will be brief open VFR
windows between waves of rain and snow.

&&

Gjt watches/warnings/advisories...
Colorado...Winter Weather Advisory until 9 am MDT Monday for coz010-013.

Winter Storm Warning until 9 am MDT Monday for coz009-012-018-
019.

Utah...Winter Storm Warning until 9 PM MDT Sunday for utz028.

&&

$$

Update...jdc
short term...jam/jad
long term...jad
aviation...cirrocumulus

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