Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 200502

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1102 PM MDT Fri May 19 2017

.SHORT TERM...(Tonight through Saturday night)
Issued at 225 PM MDT Fri May 19 2017

The upper level low responsible for producing significant snowfall
across the mountains and northern valleys the last couple days is
slowly shifting eastward, and weakening as it does. The center of
this low circulation is hard to pinpoint exactly, but seems like
it is centered along the central divide (near Vail to Monarch Pass
vicinity). Some moisture is still rotating around the broad
circulation with the bulk of the energy directed over the Plains,
but overall appears disorganized across the western slope. Some
convective showers are occurring, but seems hit or miss and not
very widespread. A couple inches of snow are possible over the
northern and central higher terrain through this evening but roads
should remain wet where showers fall and according to webcams are
dry elsewhere, as enough sun is breaking through the clouds to
help melt snow on the pavement as it falls. Previous winter
highlites were cancelled this morning and this forecast appears on
track with improving conditions from west to east today as the
system moves further eastward.

The slow movement of this upper low will also keep clouds hanging
around overnight for the central and northern areas, limiting
sufficient radiational cooling for areas like the Grand Valley and
Montrose to see widespread freezing temperatures. Temperatures may
approach freezing in Montrose, but areas north of there from Delta
to Hotchkiss appear to remain above freezing. Therefore, cancelled
the Freeze Watch for tonight for COZ011 (Delta-Montrose area).
This has also been the trend the last couple of days with cloud
cover despite colder air moving in, where majority of those areas
were above freezing. Southwest Colorado valleys, however, will see
more clearing on the southwest end of that low and should drop
below freezing, as temps the past couple nights were in the upper
20s to low 30s. So, upgraded COZ020 (Paradox Valley) and COZ021
(Cortez area) to a Freeze Warning for tonight through Saturday
morning. This should be the last freeze products issued for a
while as a warming trend is in store through the coming week.

A dry day is in store for most of the area on Saturday as the
upper low moves into the central high plains and high pressure
tries to build over the west coast. A weak disturbance will clip
our northern mountains for some light snowfall, but accumulations
appear minimal at this time. Temperatures should slowly rebound
for a milder day but still a few degrees below normal.

.LONG TERM...(Sunday through Friday)
Issued at 225 PM MDT Fri May 19 2017

The GFS and ECMWF are in pretty good agreement through Friday,
leading to higher confidence in the going forecast although some
discrepancies lie in a few details. As the upper low moves into
Ontario and the northern Great Lakes by Sunday, a few weak
disturbances will move around this large scale circulation through
Tuesday as the low remains over this region. This will result in
a chance of afternoon showers and storms mainly over the higher
terrain each day with some spread into adjacent valleys. The
northern and central mountains look favored at this time but
snowfall accumulations in the mountains look minimal with a couple
inches at best with each disturbance. The Sunday disturbance looks
a little more robust than the others, resulting in a bit better
coverage of showers. Temperatures will be on a slow warming trend
with values near normal through Tuesday.

Drier air will encompass much of the region by Tuesday afternoon
through Thursday as the ridge of high pressure over the west
slides over the region. This will also lead to temperatures rising
to above normal levels through the end of the week. A couple weak
shortwaves move in from the Great Basin and across the northern
portion of the area towards late Thursday into Friday, resulting
in a few showers and storms once again over the higher terrain.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1102 PM MDT Fri May 19 2017

Clouds will gradually clear with cigs slowly lifting as the
strong low pressure system continues to drift east. A few isolated
showers and lower cigs will persist as a result of residual
moisture but otherwise, VFR conditions are expected for all TAF


CO...Freeze Warning until 9 AM MDT Saturday for COZ020-021.



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