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Area forecast discussion 
National Weather Service Grand Junction Colorado
317 PM MDT Monday Apr 20 2015

Short term...(this evening through Tuesday night)
issued at 317 PM MDT Monday Apr 20 2015

This afternoon...no organized forcing is seen in northwest flow but
precipitation water values are at a respectable 0.50 inch. Afternoon
showers isolated storms formed first over higher terrain this
early afternoon with a few storms to move over nearby valleys
late afternoon to near sunset. Gusty outflow winds will be more
widespread than showers. Small hail is possible over the higher
terrain under the strongest afternoon cells.

Most showers and storms will end around sunset though isolated
showers may continue over the eastern mountains until near midnight.
Convective debris clouds diminish after midnight. Overnight lows
will drop to near normal.

A southeast to northwest oriented ridge of high pressure will
shift over the area on Tuesday. Look for a slight downturn in
afternoon convection on Tuesday as the moisture slowly erodes. The
flow will weaken and become more westerly...but moderate middle
level instability will persist. Temperatures will climb to a few
degrees above normal.

Long term...(wednesday through monday)
issued at 317 PM MDT Monday Apr 20 2015

A series of disturbances will impact the western Continental U.S. Through the
long term period. For starters a flattening ridge will persist over
eastern Utah/western Colorado through Wednesday. However remnant energy from an
ejecting Baja California low will pass over the area from the southwest...
and will provide a little better environment for afternoon
convection. Thus an uptick in showers and thunderstorms can be
expected Wednesday afternoon.

The pattern will then become more active as a stronger low pressure
system moves into the Desert Southwest then across The Four Corners
Thursday and into Friday. While model agreement is fairly high in the bigger
picture...there continues to be many differences in the details. The
GFS is about 6-9 hours faster then the European model (ecmwf)...with precipitation
spreading into the area by midday Thursday and peaking during the late
afternoon and evening. The European model (ecmwf) holds off with the best
precipitation not until late Thursday night and through the day on
Friday.

Then as this trough exits...models indicate the next disturbance
will pass over the western U.S. This weekend. Again details have yet
to be resolved...but this shortwave appears to track more from the
west or northwest.

Temperatures look to be a little above normal through Thursday...then a
little below normal through the weekend.

&&

Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 317 PM MDT Monday Apr 20 2015

In continued marginally moist and unstable northwest flow...scattered
mountain obscuration with snow and rain showers will result in
MVFR ceilings and visibility over the higher terrain through 02z. Through
02z...kase kege kmtj could see brief ceilings below 040 visible below 5sm in
-tsra. All sites could see outflow winds with g35kts through 02z.
Isolated shsn/rain could linger over Colorado higher terrain until 06z.
But for taf sites after 02z VFR conditions are expected tonight
though Tuesday. After 18z Tuesday expect isolated cells and showers
forming mainly over the Colorado higher terrain.

&&

Gjt watches/warnings/advisories...
Colorado...none.
Utah...none.

&&

$$

Short term...eh/Joe
long term...eh
aviation...Joe

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