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Area forecast discussion 
National Weather Service Grand Junction Colorado
808 am MDT Sat Apr 25 2015

issued at 808 am MDT Sat Apr 25 2015

First round of precipitation has moved into the forecast area this
morning...with rain over the western valleys...and snow in the
mountains. The heaviest snow has occurred over the western San
Juan Mountains with a quick 6 inches reported at Silverton by 8am
MDT. Expect this first round to wind down late this morning. Also
as the day warms...any snow/slush on the roadways will melt. While
snow showers will still be expected at times this afternoon...
melting and settling will keep any impacts low. Therefore went
ahead and issued a Snow Advisory above 9000 feet through
cover the accumulations this morning. The watch is still on track
for late tonight through Monday morning.


Short term...(today through sunday)
issued at 353 am MDT Sat Apr 25 2015

Wet and potentially snowy weekend remains on track for much of
eastern Utah and western Colorado as strong 300 mb jet closes off
southern portion of splitting trough. This new closed low
eventually tracks across northeast Arizona to near Albuquerque by
late Sunday afternoon.

System taps subtropical moisture coming up off the Baja California with
precipitable water values exceeding a half inch across southeast
Utah and extreme western Colorado by this afternoon. Upslope flow
into the southern valleys and approaching wave from the west will
kick off widespread showers across much of the region through
this evening...with isolated thunderstorms also possible. Cloud
cover will help knock temperatures back a few more degrees today and have
undercut the cooler mav numbers by a few degrees..especially
across the central and southern zones.

By tonight...slightly cooler air aloft slides in as the low
passes to our south. 700 mb temperatures drop to around -2c by Sunday morning
and with any convection expect snow levels to drop as low as 7500
feet...although any significant accumulations will be above 10k.
Still some question as to how much cold air we can wrap into
this system with southern tap of moisture working around the
low. Not quite ready to jump into any advisories or warnings for
the higher peaks...but have issue a Winter Storm Watch for areas
above 10k feet for zones 9...12...18 and 19. Will let day shift
make final call on watch or warning products...but potential for
6 plus inches is not out of the question for the San Juans and
west central mountains above the 10k mark.

Sunday will see more of the same as the low tracks slowly across
New Mexico with moisture wrapping around the northern periphery of
the low. Will keep probability of precipitation high through the period with liquid precipitation
amounts exceeding an inch possible in some areas. Temperatures will be
running well below seasonal norms on Sunday with guidance numbers

Long term...(sunday night through friday)
issued at 353 am MDT Sat Apr 25 2015

The Winter Storm Watch will continue through Monday morning for
the higher elevations of zone 9...12...18 and 19...which comprise
the Grand Mesa...western San Juan mts and the west elks above
10,000 feet. By late Sunday night the low center should be moving
from Easter nm to The Pan handles of Texas and OK with precipitation
continuing to wrap around the northwest quadrant of the storm. This flow
should keep high elevation snow falling over the zones will
watches...with the snowfall diminishing over zone 9
first...followed by 19...12 then 18. 700 mb temperatures will be the
coolest of the storm Sun night and Monday morning...but moisture will
be on the decline.

Late Monday afternoon through and Tuesday morning a short wave
projected to drop down the west side of the slow-moving low may
bring a brief upturn in precipitation over the Colorado mts and high plateau.
Lingering orographic showers will slowly diminish Tuesday and Tuesday

High pressure will build in the from west Wednesday and past east of the
area Thursday evening. Weak disturbances in the SW flow behind the
ridge should bring an uptick in mountains convective development
Friday. Temperatures should rise above normal Wednesday through Friday.


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 353 am MDT Sat Apr 25 2015

The initial disturbance in a return to winter-like weather will
bring a broad area of rain showers/shsn and low ceilings/visibility from NE Utah
first and into western Colorado through 18z...then continuing across the
rest of western Colorado this afternoon. Expect widespread -shra/-shsn with
scattered thunderstorms with this band...with ceilings below 050 and visible below
3sm at times in the heaviest Showers. Mountain tops will be obscured at
times in shsn. Snow level around 10000ft except down to 8000ft in
heaviest storms.

After a brief downturn in precipitation coverage this evening...
widespread rain and snow will move into the area after midnight
tonight. Mts will be obscured and flight conditions will drop to
MVFR at most taf sites...with IFR at the higher elevation


Gjt watches/warnings/advisories...
Colorado...Winter Weather Advisory until noon MDT today for coz018-019.

Winter Storm Watch from late tonight through Monday morning for


short term...jdc
long term...cirrocumulus

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