Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 241140

Area Forecast Discussion
National Weather Service Grand Junction CO
540 AM MDT Tue Apr 24 2018

.SHORT TERM...(Today through Wednesday)
Issued at 252 AM MDT Tue Apr 24 2018

A fairly robust upper trough is dropping across the W.Dakotas this
morning and will continue to drop southeast through NE/KS over the
next 24 hours. The upper jet rounding the southern periphery of
this low will be a good vehicle for providing ascent over
W.Colorado through the early evening hours. There is also some
decent mid level upglide over the surface front that is weakening
over the southern CWA early this morning. Add in some orographics
and bit of instability and this is leading to scattered snow
showers over the central divide mountains this morning. The top of
Vail Pass is showing some light snow accumulation but still have
no plans for winter highlites. There should be somewhat of a lull
this morning but the direct circulation of the upper jet will be
coming through around peak heating which should get some decent
convective showers going from the Central to Southern hills.
Again not too worried about these showers under the late April.
Most of the activity will be moving out of the southern mountains
through the late evening hours as the jet moves off to Plains.
Transitory ridging follows for Wednesday leading to a dry
forecast. Temperatures behind the front will be some 7 to 12
degrees cooler with only a few degrees different in the far south.
Down here there is some concern for localized critical fire
weather conditions and winds traditionally are quite strong across
the southern valleys in the wake of a front. Low humidity will
also be present near the NMex border. Rather chilly night with the
ridge bringing in clearing skies.

.LONG TERM...(Wednesday night through Monday)
Issued at 252 AM MDT Tue Apr 24 2018

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 12Z TAFS through 12Z Wednesday morning)
Issued at 540 AM MDT Tue Apr 24 2018

Scattered light rain and snow showers will continue this morning
over the central portions of the forecast area primarily impacting
KASE. Showers will be in the vicinity at KEGE and KGUC. Thunderstorms
will develop after 18Z this afternoon mainly over the central and
southern Colorado mountains along the divide. Potential impacts
to KASE and KGUC with gusty winds to 40 kts possible near showers.
Mountain obscuration will occur at times with CIGS dropping below
ILS breakpoints. Elsewhere, expect VFR conditions with breezy
conditions this afternoon and partly sunny skies. Conditions
greatly improve this evening as drier air moves in and skies




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