Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 310550 AAA

Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
1150 PM MDT SAT JUL 30 2016

Issued at 900 PM MDT Sat Jul 30 2016

Line of severe thunderstorms moving southeast out of the Black
Hills of South Dakota could clip parts of Dawes and Northern Box
Butte counties here in the next few hours as the cold pool off
that complex accelerates southeast. Severe Thunderstorm Watch in
effect for those counties...but will also have to closely watch
the Fort Robinson area of northern Sioux County for potential
development on the southwest side of the line...although right now
greater threat is for areas east for damaging winds and large


.SHORT TERM...(This evening through Sunday night)
Issued at 200 PM MDT Sat Jul 30 2016

The coverage and intensity of potential thunderstorms this afternoon
and evening continues to be a big question mark. Although skies have
been clear for much of the day, MLCIN values are still in the -50 to
-100 J/kg range per the latest SPC Mesoanalysis. Capping less across
east central Wyoming and the northern Panhandle, but HRRR runs still
suggest failed convective initiation and little/no coverage of tstms
through the late afternoon and evening. If storms develop, MLCAPE in
the neighborhood of 1500 to 2000 J/kg and effective bulk shear of 30
to 35 knots could support supercell development. The SPC Slight Risk
area looks good for the highest probability of this. Isolated/widely
scattered PoPs should be appropriate here. An unsettled pattern will
remain in place for Sunday beneath active, quasi-zonal flow aloft. A
few differences in QPF output between the GFS and NAM, likely due to
capping with H7 temps progged around +18 deg C, but we expect to see
some development along a surface trough tracking across the area. It
will be warm on Sunday, with 90s common east of the Laramie Range.

.LONG TERM...(Monday through Saturday)
Issued at 200 PM MDT Sat Jul 30 2016

Upper ridge building back into the area through next week should
limit precip chances and we should begin to warm and dry out.

Do have a frontal boundary that comes through Wednesday night into
Thursday that could bring the return of convection across the
Panhandle to the eastern slopes of the Laramie Range. Some
disagreements seen on the ECMWF and GFS on this happening though.
ECMWF does not bring convection back into the area until next

Did a blend of the two models and kept slight chance PoPs for the
afternoon hours. Seemed to match up well with the neighboring
offices as well doing this.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1140 PM MDT Sat Jul 30 2016

VFR will prevail overnight with partly cloudy skies. Light southeast
winds and some boundary layer moisture may lead to MVFR visibility
in patchy fog/mist by daybreak over portions of western Nebraska,
specifically invof Chadron and Alliance. Confidence is not high
enough to mention in TAFs, but will monitor. Any fog/mist that forms
will burn off around mid-morning Sunday. Expect isolated to scattered
coverage of SHRA/TSRA Sunday afternoon across southeast Wyoming, with
the best chances over the mountains. Added VCTS for Rawlins, Laramie
and Cheyenne.


Issued at 150 PM MDT Sat Jul 30 2016

Fire weather concerns will be elevated over the next several days to
the west of the Laramie Range. Minimum humidities will be in the low
to middle teens, with wind gusts around 25 MPH in the afternoon.


.CYS Watches/Warnings/Advisories...


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