Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 240539

Area Forecast Discussion
National Weather Service Grand Junction CO
1139 PM MDT Mon Apr 23 2018

.SHORT TERM...(Tonight through Tuesday night)
Issued at 400 PM MDT Mon Apr 23 2018

Rising temperatures and instability were driving some light moist
convection and a few lightning strikes over the northern and
central Colorado mountains early this afternoon. Some weak lift
also provided by the closed low pressure trough over the northern
Rockies. This system was driving a cold front which had reached a
KRWL-to eastern Uinta Mountains-to near KPUC line as of 2 PM this
afternoon. As the front moves across northeast Utah and northwest
Colorado late this afternoon then across east-central Utah and
west-central Colorado this evening, shower/isolated thunderstorm
activity will become more focused over Colorado`s central
mountains, with scattered showers impacting adjacent valleys.
Snowfall in the mountains will be elevated, with 2 to 4 inch
accumulations with locally higher accumulations above 10,000 feet
expected. Impacts from snowfall are expected to be minimal so have
no plans to issue Winter Weather Advisory with this event.

Instability, residual moisture and a weak trailing shortwave
associated with the Rockies low will continue to bring scattered
showers and isolated thunderstorms to the Continental Divide
Tuesday. A ridge of high pressure builds to the west on Tuesday
night which, when combined with diurnal cooling should bring an
end to shower activity by late evening.

Temperatures will be cooler across the north tonight, and cooler
across the entire forecast area on Tuesday, though highs will be
near seasonal norms. Overnight lows a bit chilly Tuesday night as
clouds decrease and winds will are expected to be light and
terrain driven.

.LONG TERM...(Wednesday through Monday)
Issued at 400 PM MDT Mon Apr 23 2018

High pressure over the West will keep shower/thunderstorm activity
at bay Wednesday and Wednesday night. A shallow, fast moving
shortwave in the northwest flow is expected to brush the northern
mountains along the Continental Divide on Thursday bringing some
light scattered precipitation which should end by sunset.

The GFS solution diverges with the EC/Canadian solutions on Friday
resulting in significant differences in QPF output. The GFS moves
a closed low over the eastern Pacific toward the northern
California coast and begins to tap into subtropical moisture from
the Mexican Plateau on Friday. It then fills the low center and
moves the resulting open wave trough across the Great Basin. As
this feature translates eastward it will keep showers going over
much of the southern portion of the forecast area through Saturday
evening, before dryer weather arrives Sunday. In contrast, the EC
and Canadian hold the low center well off the coast on Friday,
and as a result, generate little (EC) to no QPF (Canadian) on
Friday. They then move the closed low over northern California
Saturday then slowly across the Great Basin Sunday which begins a
period of unsettled weather over the area which extends into the
coming week. However, positioning of the low by the end of the
extended period is much farther north according to the EC and more
southerly in the Canadian solution. Given model differences will
go with the low end blended solutions until model agreement

Temperatures will be mild through the period with highs around 5
degrees above normal and higher until Monday when afternoon
temperatures are expected to dip back to near normal levels.
Overnight lows will be close to normal by and large.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1138 PM MDT Mon Apr 23 2018

Scattered rain and snow showers will persist over the region
through Tuesday afternoon. Showers will be most numerous over the
mountains and high valleys, including in the vicinity of KHDN,
KASE and KEGE. Mountain obscuration will occur in the vicinity of
showers and CIGS will drop below ILS breakpoints at times through
late Tuesday afternoon before conditions improve Tuesday evening.
Local wind gusts up to 40kts will also be possible near showers.




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