Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 162104

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
304 PM MDT Fri Mar 16 2018

.SHORT TERM...(Tonight through Saturday night)
Issued at 216 PM MDT Fri Mar 16 2018

Observations across western Colorado and eastern Utah showed
clear skies and cool temperatures today. To the east, yesterday`s
storm system was spinning, in dramatic fashion, as a vertically
stacked upper level low dragging a cold front through eastern
Kansas. To the west, a few high cirrus clouds were moving in atop
a few boundary layer cumulus. These high clouds were associated
with a strengthening anticyclonic jet and upper level ridge.
Water vapor imagery showed a trough moving onto the coast of
northern California to the west of the ridge.

The aforementioned ridge should keep things quiet the rest of
today and for the first part of tomorrow before the approaching
trough begins to impinge on eastern Utah and western Colorado.
Strong southwesterly winds aloft and at the surface should develop
as a 110kt 300 mb jet moves overhead. Weak surface cyclogenesis
across northern utah and southern Wyoming will also enhance
surface winds. A few spots in Colorado Zones One and Two may come
close to Wind Advisory criteria Saturday afternoon. Given the
limited spatial coverage and uncertainty of any meaningful gusts,
have decided to not issue an advisory at this time. Saturday
evening showers and some isolated thunderstorms should develop.
Most numerical guidance showed mild air associated with the system
to start. This will keep snow ratios low to begin with. Colder
air will quickly fill in from the Northwest behind the cold front
late Saturday night.

.LONG TERM...(Sunday through Friday)
Issued at 216 PM MDT Fri Mar 16 2018

The heaviest snow from this storm system is expected to fall
Midnight Saturday through early morning Sunday. Rapid Lee
Cyclogenesis is expected across southeastern Colorado Sunday
Morning. A Sub 1000 mb low should develop by mid day accelerating
the pacific front further east. This rapid deepening will also
help create additional lift over the far eastern portions of the
area, especially the Southeastern San Juans. the NAM and GFS both
show frontogenic banding developing along the arctic front
Sunday. This could produce some higher snow totals in areas
underneath this feature.

Confidence is high in widespread precipitation falling across the
area Saturday night into Sunday. The GFS is a bit more aggressive
than other guidance bringing the precip and colder air into Utah
slightly earlier. Aside from small timing differences, there is
good agreement on QPF and significant mountain snow. Above 8,000
feet 5 to 10 inches with an isolated 12 are expected through
Midnight Monday. Further north, generally 4 to 8 inches can be
expected. Lower valleys along Interstate 70 will be too warm to
start but may see a change over to a rain snow mix late Sunday.
Durango and the southern valleys could see a broad 2 to 4 inches
as the best forcing aloft passes overhead early Sunday.

Some orographic snow showers on the backside of the low should
persist across the north through Tuesday as northwest flow aloft
develops ahead of another ridge of high pressure. This will keep
Midweek quiet before another potentially impactful storm
approaches early next weekend.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1156 AM MDT Fri Mar 16 2018

This storm system and moisture is moving east of the Rockies
leaving VFR conditions in place late this morning. Instability is
strong enough to keep some cumulus clouds building this afternoon
and there could be some ILS break points temporarily met. Dry air
invading from the west should prevent precipitation from becoming
more than isolated in the mountains through sunset. Northwest flow
with gusts over 20 mph could create some arrival issues into KASE
through sunset as well.




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