Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 162334
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
434 PM MST Sat Dec 16 2017

.SHORT TERM...(Tonight through Sunday night)
Issued at 308 PM MST Sat Dec 16 2017

Plenty of cloud cover across the region today as mid and high
level moisture increased in the southwesterly flow ahead of a
weak shortwave trough. The latest model runs this afternoon really
are quite dismal in terms of any substantial precipitation with
the passage of this trough this evening and Sunday given how dry
the lower levels of the atmosphere are and that the brunt of upper
level support will be deflected well to our south as this system
splits. The Eastern Uintas will have the best potential to
receive a quick shot of snow tonight but accumulations remain
minimal.

Heavier cloud cover will begin to dissipate throughout the day on
Sunday as the shortwave lifts to the northeast and a weak
transitory ridge of high pressure builds in from the west. Daytime
highs Sunday will be a few degrees cooler under a slightly colder
airmass and overnight lows will remain on the chilly side and be
closer to seasonal norms.

.LONG TERM...(Monday through Saturday)
Issued at 308 PM MST Sat Dec 16 2017

Temperatures will gradually rebound through midweek as upper level
flow eventually becomes zonal. By Tuesday night our next and much
stronger Pacific storm will begin to move inland across the
northwestern CONUS. The progression of this storm into the Great
Basin on Wednesday will allow southwesterly flow to increase over
our region and see the return of heavier cloud cover. Models are
consistent in seeing this storm transition to a closed low as it
arrives on our doorstep Wednesday evening. This low has the first
decent storm structure we`ve seen in quite a while as well as
some substantial moisture so scattered and even numerous showers
look to develop overnight Wednesday and continuing through
Thursday.

Snow levels at the onset of this event will range between 6 and
8kft. Significantly colder air will work into the region with the
passage of a cold front Wednesday night which will allow snow
levels to plummet to valley floors area-wide. Confidence is not
high at this time in terms of accumulations given the differences
still existing in QPF totals but confidence is high in regards to
the drastically colder 700mb temperatures which has been a
consistent model trend over the past several runs.

The Euro is slightly quicker than the GFS in carrying this low out
of our region Thursday night and pushes it out into the southern
Plains while the GFS carries it south to Arizona. Behind this
system a weak embedded disturbance in the northwesterly flow
should bring some light orographic snow showers to the northern
Colorado mountains on Saturday. Some of the coldest temperatures
of the season so far are expected for Thursday and going into the
weekend with daytime highs staying in the low to mid 30s for many
valley locations while the mountains stay in the upper teens to
low 20s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 429 PM MST Sat Dec 16 2017

Mid to upper level clouds will continue to stream into the area
for the rest of this afternoon into the overnight hours. Ceilings
should remain above 12K feet so no flight concerns there. VFR will
remain in place for all TAF sites. ILS breakpoints are also not
expected to be reached at any TAF site.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...MMS
LONG TERM...MMS
AVIATION...TGR



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