Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 142316

Area Forecast Discussion
National Weather Service Grand Junction CO
416 PM MST Tue Feb 14 2017

.SHORT TERM...(Tonight through Wednesday night)
Issued at 205 PM MST Tue Feb 14 2017

Clearing and drying continues over the forecast area this
afternoon. Low clouds have persisted into the afternoon along the
US 40 corridor from Craig to Hayden, however coverage of these
clouds has decreased over the past few hours. This trend is
expected to continue through the evening as drier air at low
levels slowly filters south from Wyoming. Aloft, a few high clouds
will also drift southward over the central Rockies overnight.
These clouds will be south of the Colorado border by sunrise with
a mostly clear night expected area-wide. Tonight will be a good
radiational cooling night in high-mountain valleys that still hold
a snowpack; as a result low temperatures will be at or below
lowest guidance in places such as Craig and Gunnison. In fact, all
valleys should cool well tonight and despite the mild air in
place, low temperatures should end up right around average for

Wednesday will turn out mostly sunny over all of eastern Utah and
Western Colorado. 500mb heights will slowly rise through the day
as a ridge of high pressure builds in. As a result, high
temperatures will be slightly warmer on Wednesday by two or three
degrees in most locations. Mostly clear skies are once again
expected on Wednesday night with lows near or slightly above
average. Have lowered low temperatures slightly in this forecast
package after considering low cloud cover and dry air in place.

.LONG TERM...(Thursday through Tuesday)
Issued at 205 PM MST Tue Feb 14 2017

Thursday will start off mostly sunny as the ridge axis at 500mb
passes through western Colorado. High clouds will begin to stream
in over eastern Utah and western Colorado in the evening as
unsettled weather moves into the west coast. The first in a series
of weather makers will pass through the Utah-Colorado region on
Friday morning. This system has trended weaker in today`s forecast
guidance, with only a brief period of light snow in the northeast
UT/northwest CO mountains on Friday morning. Valleys south of
Interstate 70 will stay dry, with a few rain showers in valleys to
the north. Guidance has trended drier for friday afternoon and
evening, with barely any precipitation even in the mountains from
noon through midnight Friday. Temperatures will remain warm during
the afternoon, with highs in the valleys in the mid 50s to near 60
in the lower valleys in southeastern Utah.

As mentioned in previous discussions, the weather pattern from
Friday evening through the weekend is complex, with a rather high
degree of uncertainty on precipitation timing and amounts. A deep
trough will come ashore along the California coastline on Friday
afternoon, directing a stream of Pacific moisture into the central
and southern Sierra. As this trough digs southward, flow will turn
southerly over eastern Utah and western Colorado on Saturday. The
trough will eventually cut off over the northern Baja Saturday
evening. Where and when exactly this trough cuts off will largely
determine impacts over the Four Corners region this weekend. As
of 12z guidance Tuesday afternoon, light precipitation will likely
move back in over the central Rockies after midnight on Saturday
morning as a weak warm front pivots north around the area of low
pressure. Scattered light precipitation is likely during the
afternoon on Saturday before a break on Saturday night into
Sunday. Temperatures Saturday are expected to be warm enough for
all rain in the valleys with light snow in the mountains in areas
over 8000 feet. 700mb temperatures are expected to be in the -1 to
-3 degree range during the afternoon hours Saturday, warming to
near 0 area-wide during the day on Sunday.

After a break in precipitation on Sunday, the cutoff low will head
eastward through Arizona and New Mexico late Sunday night into
Monday morning. Guidance is split as to whether or not we will see
a second round of precipitation during this time frame. The GFS
keeps the low pressure suppressed to the south, with only the San
Juan mountains seeing a mix of snow in the higher terrain and rain
in the valleys. The ECMWF lifts this storm northward through the
central Rockies, with snow in all mountain zones on Sunday night
and Monday morning, lingering into the afternoon hours. This
forecast package reflects a wetter solution for the Sunday
night/Monday timeframe. Temperatures will once again be warm with
this event, with snow levels likely to be above at least 7000 feet
through late weekend and early next week.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 412 PM MST Tue Feb 14 2017

VFR conditions will continue through the early evening hours at
all terminal locations. A few lingering mid level clouds will
gradually scatter out over DRO as the evening progresses with CIG
heights above ILS break points. Isolated patchy fog may develop in
the north however VEL is expected to remain clear overnight at
this time. Overall forecast confidence is high.




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