Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 271134

Area Forecast Discussion
National Weather Service Grand Junction CO
534 AM MDT Mon Mar 27 2017

.SHORT TERM...(Today through Tuesday)
Issued at 433 AM MDT Mon Mar 27 2017

A blocky downstream pattern and anomalously strong SE.Pacific
ridge will favor digging storm systems across the Great Basin
through this forecast. The first of these storms is progressing
across the left coast near CA/OR this morning and will be closing
a mid level circulation over central Utah this evening. The models
through 48 hours are a bit closer in agreement then taking this
low just to the left of the 4 Corners then swinging it across
NW.Arizona into NC.New Mexico through Tuesday afternoon. Ascent
will slowly increase through the day as the SW to NE oriented jet
shifts across the UT/CO border and the upstream trough digs into
the Great Basin. Strong height falls to our West increases southerly
flow and advect some of the Pacific tap of moisture northward.
The bulk of the organized precipitation today will be focused to
our west though an area of enhanced lift does nose into NE.Utah
by early afternoon and winter highlights will begin there as a
result. As the atmosphere destabilized this afternoon unorganized
convection will bubble over the remainder of the region. Mixing
will aid heating except in the the far NW CWA where cloud shield
and precipitation will hinder warming. Several interesting things
happen tonight as this storm deepens and moves by the 4 Corners.
The height falls over our area will again induce strong southerly
winds over the high plains...creating a warm conveyor belt of
moisture from the Gulf of Mexico up into eastern CO/WY. To the
west...surface low pressure looks to track ahead of the upper low
and lift a warm front through SE.UT/SW.CO. This boundary along
with plenty of instability will lead to an area of enhanced
precipitation that will be lifting to the north border through
sunrise. This area of precipitation is then followed by the cold
frontal passage tracking in the wake of the upper low dropping to
the southeast. Eventually the moisture riding northward with the
front range conveyor belt will wrap around the back side of the
low on Tuesday and keep widespread precipitation pointed at NW
Colorado and NE Utah. Cold valley rain will transition to snow in
the hills. Cold air aloft will keep a strong convective component
to the snowfall which makes this a difficult forecast. Time of
year will not favor snowfall accumulating in lower elevations but
the convective element will be driving heavier precipitation
rates. Feel elevations above 9000 feet have the greatest threat of
snow impacts though snow could be falling as low as 6000 feet at
times. Snow has the best chance of accumulating at night...though
snow to liquid ratios still around 10-12:1. The areas of higher
confidence extend from the SE/Utah and SW Colorado mountains into
the high central mountains...and the high Uintas will be favored
through the event due to the strong wrap around moisture on NE

.LONG TERM...(Tuesday Night through Sunday)
Issued at 433 AM MDT Mon Mar 27 2017

As the upper level cutoff low shifts east on the southern high
plains as the stronger core of the upper jet reforms to the east
late Tuesday. Lee cyclogenesis will commence over the southern
plains as a result and help pull cold air down the front range.
Dynamic support shifts east triggering the probability for heavy
snowfall snowfall to the front range and points eastward. Despite
the loss of dynamics, lingering moisture and northwesterly upslope
flow will result in mountain snow showers through the night and
into Wednesday morning. The ECMWF and NAM end precipitation in the
mountains around noon, with the GFS holding on to a few snow
showers in the Elk, Gore, and Sawach ranges through 6pm.

The storm system will move east across the High Plains on
Wednesday night bringing an end to the precipitation to all
mountain locations. A transient ridge will provide a short break
as the next storm system drops into the Great Basin region on
Thursday. Both the GFS and the EC take this closed low to a
position near the Four Corners region on Friday and slowly move
the storm east near the Colorado/New Mexico state line on
Saturday. The EC takes a faster and more progressive solution
moving the storm out of our area by Saturday as a quick moving
shortwave drops southeast into New Mexico by Monday. Run to run
consistency has been fairly low with this storm so confidence is
low regarding details of the storm. However, this storm is quite
cold and fairly wet so depending on its exact track, the
possibility exists for significant snowfall in some mountain
locations late Thursday into the weekend.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 534 AM MDT Mon Mar 27 2017

Mid and high level clouds will gradually lower through the
afternoon and evening hours and the next storm system approaches.
ILS break points may be in threat after 21z today at many
locations with lower flight criteria likely after 06z. No impacts
through the first six hours of the 27/12Z forecast are
anticipated. Isolated thunderstorms will be a threat this
afternoon and evening across much of eastern Utah and western


CO...Winter Weather Advisory from 6 PM this evening to noon MDT
     Wednesday for COZ009-010-012-013-018-019.

UT...Winter Weather Advisory from 3 PM this afternoon to 9 AM MDT
     Wednesday for UTZ023.

     Winter Weather Advisory from 6 PM this evening to 9 AM MDT
     Wednesday for UTZ028.



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