Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 232221

Area Forecast Discussion
National Weather Service Grand Junction CO
321 PM MST Thu Feb 23 2017

.SHORT TERM...(Tonight through Friday night)
Issued at 318 PM MST Thu Feb 23 2017

A much colder airmass has settled over the area under a broad
trough of low pressure aloft. Surface low pressure over southern
WY and a deeper low over southeast CO has enabled gusty surface
winds due the tight pressure gradient over the region. There is
also a mid level low pressure center over southern WY and
circulation around this will keep a favorable upslope northerly
wind into the Uinta Mtns through tonight...and a west to
southwesterly flow into the central and northern mountains through
midday Friday. Radar and webcams indicate quite a bit of snow
shower activity across the area, but lower elevations not seeing
much reach the ground due to very dry low levels. Models picking
up on some convergence over the Flat Tops and upslope orographic
snow for the Uintas and northern and central mtns of CO through
tonight and into Friday. With that in mind, the main change to the
short range was to boost PoPs and precip amounts in these areas.
However, with the unstable nature of the atmosphere, snowfall will
be showery, but still persistent near the Divide. Did not go as
high on the QPF as the NAM suggests, but still ended up with forecast
snowfall of 4 to 12 inches for the above mentioned areas through
Friday. This combined with the stronger winds through early
tonight will necessitate extending and expanding the winter
weather advisory. Did not go with warning due to highest snowfall
amounts limited to areas not highly traveled and snowfall today
has not impacted roads. Vail Pass will certainly be a trouble spot
due to its high elevation, and periodic heavier snow rates

As the main upper level trough shifts east over the Plains Friday,
flow becomes northwesterly and lightens. The airmass also dries
out slowly. Snow showers will continue, most numerous across the
northern half of the area Friday and Friday night. Otherwise,
temperatures will be 8 to 12 degrees below normal and feel
downright chilly compared to recent weeks.

.LONG TERM...(Saturday through Thursday)
Issued at 318 PM MST Thu Feb 23 2017

Another vigorous upper level trough will move down the West Coast
late Friday into Saturday. This causes the flow over our region to
become west or southwesterly Saturday. The trough moves quickly
through Saturday night and Sunday morning with relatively higher
chances for snow showers accompanying and in the rear of its
passage. The NAM is an outlier with higher snowfall amounts for
the southern San Juans and adjacent lower elevations toward the NM
border Sunday morning. Have not bit off on that solution, but
opted for an ensemble approach which keeps PoPs and QPF lower for
now. This system will at least act to reinforce the colder air
over the region heading into the early part of next week.

The active pattern continues early in the week as another, but
broader, upper level trough moves through Monday night and
Tuesday. This period will have relatively higher chances of
precipitation, mainly snow though rain/snow mix possible for lower
valleys. There are considerable differences in the various long
range models on the moisture and strength associated with this
trough and the southwest flow ahead of the system. So, confidence
at this point is low. Northwest and drier flow follows for Wed
and Thur with a slow warming trend, but remaining below normal.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1129 AM MST Thu Feb 23 2017

The cold front has pushed through so now we deal with cold air
advection aloft, gusty winds, and convective showers. Expect gusty
winds to continue through about 00Z as the gradient loosens.
Occasional snow showers will be possible through the next 24 hours
especially for the mountain TAF sites as well as north of the I-70
corridor. When these showers move in, expect MVFR cigs and vis possibly
dropping to IFR under the stronger showers. Outside of KTEX, KASE,
and KEGE, expect varying scattered to broken ceilings over the
next 24 hours. Low clouds will continue for KVEL and will likely
remain so for the next 24 hours along with some patchy fog.


CO...Winter Weather Advisory until 9 AM MST Friday for COZ003-004-009-

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



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