Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 230952
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
352 AM MDT Thu Mar 23 2017

.SHORT TERM...(Today through Friday)
Issued at 352 AM MDT Thu Mar 23 2017

Forecast models are in great agreement regarding this storm system
through Friday, leading to higher confidence in the storm track.
Showers are steadily increasing across eastern Utah this morning
as a strong Pacific storm system moves into the Great Basin. The
upper low center is currently situated over Las Vegas area with a
120 kt jet rounding the base of the trough through Mexico and into
Arizona. Utah and Arizona are located in the left exit region of
this upper level jet streak, with thunderstorms having occurred
last evening through the early morning hours and starting to
become more isolated. Temperatures are still fairly mild this
morning with snow levels aoa 9000 to 10000 feet MSL. Vernal has
already picked up almost 0.5 inches of rain since 9 pm yesterday
evening with the eastern Uintas seeing an estimated 2 to 4 inches
so far. Substantial moisture is advecting in ahead of this low
with specific humidities rising to between 4 and 5 g/kg. Satellite
was showing plenty of lift over northeast Utah as well which is
now moving into Wyoming, due to a weak H7 circulation, leading to
enhanced precip rates last night into this morning. This H7 low
circulation however is forecast to move into Wyoming as it already
seems to be doing this morning, resulting in a slight downturn in
precipitation intensity across northeast Utah.

The upper level jet streak will translate to 110 kts as it nudges
its way into southeast Utah and southwest Colorado late this
morning into the afternoon. Precipitation is expected to spread
eastward across much of western Colorado by the afternoon with the
cold front along the UT-CO border by noon. The flow will shift
around to the northwest across northeast Utah at this time, with
the northerly slopes being favored, while the rest of southeast
Utah and western Colorado see southwest winds with southwest
slopes favored for snowfall. Expect thunderstorms to develop
across the area by late morning into the afternoon with the best
lift and forcing occurring with the front that is expected to move
through western Colorado late this afternoon into the early
evening, shifting the flow to the west. Temperatures will lower
behind this front throughout the day with H7 temps bottoming out
tonight between -4C and -6C. Snow levels will start off fairly
high this morning around 8000 to 9000 feet and lower throughout
the day to around 6500 feet by midnight into Friday morning.

The upper level low will move across southern Colorado during the
late afternoon and become closed and vertically stacked by
Thursday evening over southeast Colorado. As it does, a strong
northerly flow will develop late this evening into Friday morning
across the western slope, leading to potential for enhanced snow
rates and blowing snow in the high country. North slopes will be
favored at this time. Snow accumulations appear to lessen after
midnight though as subsidence works its way in on the back side of
the low, so winds may be the biggest concern as H7 winds increase
to 30 to 45 kts. Most of the energy will be taken east of the
divide towards the Front Range and Plains after midnight tonight
into Friday morning as the upper low strengthens over southeast
Colorado and quickly moves eastward into Kansas by Friday morning.
Expecting 4 to 8 inches of snow in the mountains with some areas
seeing locally higher amounts towards a foot above 10,000 feet.
Current Winter Weather Advisories remain in good shape ending by 8
am Friday morning which still appears on track. Impacts will be
seen among the higher mountain passes. Some snow is possible among
some valley locations or mixing with rain tonight into Friday
morning but accumulations in the valleys appear very light if
anything. Improving trend will be seen late Friday morning into
the afternoon with a ridge of high pressure and drier air sliding
in from the west, leading to cooler temperatures near normal and
mostly sunny skies by Friday afternoon.

.LONG TERM...(Friday night through Wednesday)
Issued at 352 AM MDT Thu Mar 23 2017

Both the 00Z GFS and 00Z ECMWF show a ridge over the area on
Saturday, providing us with a dry weather day. However, we are
headed into a progressive/active weather pattern. A trough of low
pressure is forecast to quickly pass over Utah and Colorado
Saturday night into Sunday morning bringing the possibility of
additional precipitation with a quick ridge Sunday afternoon.
Model continuity breaks down on Monday, however both models are
forecasting a low pressure system to more or less stall out over
the Great Basin and Intermountain West for Tuesday and Wednesday,
bringing more valley rain and mountain snow to the region.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 352 AM MDT Thu Mar 23 2017

Showers will continue to spread eastward across eastern Utah and
western Colorado this morning into the afternoon as an early
Spring storm and associated cold front march eastward throughout
the day. Expect the development of scattered thunderstorms late
this morning into the afternoon, with best precipitation rates
along the cold front. Winds will be breezy at times under showers
with activity becoming more numerous to widespread after 18z. Snow
levels will remain between 8000 and 9000 feet MSL this morning,
before gradually dropping to 6000 to 8000 feet MSL after frontal
passage late this afternoon into the evening. Areas of MVFR and
brief IFR can be expected with lower cigs/vsby in heavier showers.
Mountains will be frequently obscured in snow and blowing snow.
Winds will gust to between 40 and 50 kts at the higher peaks this
evening into early Friday morning, resulting in areas of mountain
turbulence as the storm system moves onto the Front Range and
Plains.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 9 AM MDT Friday for COZ009-010-012-
     013-018-019.

UT...Winter Weather Advisory until 9 AM MDT Friday for UTZ023.

     Winter Weather Advisory until 6 AM MDT Friday for UTZ028.

&&

$$

SHORT TERM...MDA
LONG TERM...MDA/Larry
AVIATION...MDA


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