Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 180456

Area Forecast Discussion
National Weather Service Grand Junction CO
1056 PM MDT Fri Mar 17 2017

.SHORT TERM...(Tonight through Saturday night)
Issued at 320 PM MDT Fri Mar 17 2017

Record warmth continues across Utah and Colorado as high amplitude
ridging remains across the region. The hottest day of the week is
expected on Saturday. The NAM and GFS are trying to put isolated
showers over the San Juans again tomorrow afternoon, but with
conditions so dry and stable I took these out. Current satellite and
webcams in the San Juans where the forecast models were putting
precipitation today show very shallow cu squashed by a lack of any
vertical motion.

.LONG TERM...(Sunday through Friday)
Issued at 320 PM MDT Fri Mar 17 2017

The trough interacting with the ridge in place on Sunday is weaker
than in past forecast runs, but does flatten the ridge and increase
winds on Sunday. Because of the lack of cloud cover Sunday, decided
to slightly bump up the max temps on Sunday from what was there
closer to Saturday`s highs using the ADJMAV guidance. The wind at
mid levels picks up later in the afternoon on Sunday which could
lead to some gusty conditions across eastern Utah and western
Colorado valleys as winds mix down in the late afternoon. Made minor
adjustments to the forecasts as well for these afternoon wind gusts.
Mid to upper level cloud cover will increase Sunday night as the
pattern shifts to a cloudier and eventually wetter pattern. The
previous forecast discussion mentioning Sunday showers over the
mountains already looks to be outdated as the first threat of precip
shifts back to Monday. Even on Monday, mountain showers will be
isolated and very much terrain driven with weak embedded energy over
the ridge axis. The GFS is most bullish on precip on Monday evening,
and is an outlier at this point.

Clouds will stick around Tuesday, but the next chance of
precipitation is with the approaching system midweek on Wednesday.
The GFS, EC, CMC are still dancing around with their details, but do
still indicate precip beginning Wednesday evening sometime favoring
areas in southwest flow. The GFS continues to develop a closed low
over Utah before tracking it into Colorado on Thursday, versus the
EC and CMC which keep this system as an open wave. Available
moisture for this system even more impressive today than what we saw
the last couple of days, which indicates a warmer system. The
mountains of eastern Utah and western Colorado could receive a
significant amount of snow (above ~9000 ft, maybe even higher), with
liquid equivalence in either rain or snow form adding some
significant moisture to the region. QPFs on the GFS are indicating
about an inch of liquid precip in mainly locations, so we will need
to watch not only new snowfall, but rain on snow issues as well. As
mentioned in previous discussions, the snow level behind the
associated cold front may drop low enough for valleys above 6000 ft
on Thursday to see some snow at times, but these detailed can`t be
accurately parsed out until we get some forecast model consensus
and figure out the strength of this system.

This weather system will impact the region Wednesday through
Thursday, with conditions looking to clear Friday and Saturday
before the next chance of precipitation next Sunday with another
open trough or closed low.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1056 PM MDT Fri Mar 17 2017

Flow will shift to the southwest and increase Saturday afternoon
as the high pressure shifts east of the Continental Divide. Record
warmth will allow strengthening southwest winds aloft to mix to
the surface after 19Z resulting in breezy conditions at all TAF
sites except KVEL through 02Z/Sunday. Otherwise, expect dry
weather to prevail for another 24 hours bringing VFR conditions
and no chance for CIGS below ILS breakpoints region wide.


Issued at 320 PM MDT Fri Mar 17 2017

High pressure flattens over the the area Saturday. This will
allow southwest winds to strengthen over the region by Sunday
afternoon. Relative humidities are expected to drop into the 15 to
25 percent range Sunday afternoon, but they may drop lower with
record or near record heat persisting. The gusty winds combined
with warm temperatures, low humidity and still dormant or dry
vegetation may increase the potential for heightened fire weather
awareness. Check the latest forecast before attempting any burning
through this weekend as conditions can change rapidly. The
potential will be greatest for elevations below 8000 feet.


Issued at 320 PM MDT Fri Mar 17 2017

Prolonged period of record or near record high temperatures will
continue to impact the region through Sunday. This will
accelerate snowmelt resulting in increased flows on area waterways
and slow but steady rises in river levels. Temperatures are
expected to cool next week, which will help to slow the snowmelt,
however major moisture is possible during the middle of next week
in the form of both rain and snow. Will need to monitor for rain
on snow issues that could develop mid to late next week with the
changing snowpack levels.





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