Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 311124
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
524 AM MDT WED AUG 31 2016

.UPDATE...
Issued at 419 AM MDT Wed Aug 31 2016

Getting reports from southern Nebraska METARs of dense fog under a
quarter mile. Went ahead and issued a Dense Fog Advisory as
11-3.9u satellite imagery showing fog is pretty widespread. May
have to add Laramie County as well as Pine Bluffs just went down
to a half mile. Updates sent.

&&

.SHORT TERM...(Today through Friday)
Issued at 300 AM MDT Wed Aug 31 2016

Winds and fire weather concerns are the forecast challenges in the
short term.

Currently...Frontal boundary lays across central Montana into
central South Dakota into southern Iowa this morning. IR satellite
imagery showing next Pacific low pressure system moving into the
PACNW. Starting to see stratus developing over the southern
Panhandle. Areas of fog look to be a good call from the previous
crew as Sidney is now BKN007 and 11-3.9u satellite imagery
showing the stratus spreading north and west.

For today, look for the fog/stratus over the southern Panhandle to
break up mid morning or so. All guidance showing some convection
developing along the I-80 corridor from Sidney to Cheyenne. Did
add some low chance PoPs into the forecast for this area. Ridge
axis moves east early this evening. Southerly winds begin to
become stronger out over the Panhandle as GFS 850mb winds increase
to 30-35kts and southwesterly winds develop west of the Laramie
range at 15-20kts at 700mb. Going to set us up for a breezy to
windy day Thursday.

For Thursday...Could be really close to advisory level winds in
the Panhandle as 850mb winds continue through the day at 30-35kts.
Did increase winds in the Panhandle to advisory level. If the
guidance continues to show these winds tonight, we will need to
issue wind advisories for most of the Panhandle. Further west, we
are going to be close to critical fire weather as GFS soundings
showing us mixing to 550mbs. Forecast winds up there are 25-30kts,
but humidities are only marginal for Red Flag Thursday.

Better day Friday for fire weather as 35-40kts mix down across
Carbon, Albany and Converse Counties. For the Panhandle, GFS 850mb
winds peak out at 40kts Thursday night into Friday morning, so
feel pretty confident we will need wind advisories out there most
of that period. One other aspect to think about is dry
thunderstorms. Inverted V soundings Friday across the area with
PWATS around .6 to .7 inches. High based storms with not a lot of
rainfall could create some fire starts around the area. They will
also pull down these strong winds as well. Not a very good day for
fire fighters Friday.

.LONG TERM...(Friday night through Tuesday)
Issued at 300 AM MDT Wed Aug 31 2016

Friday night/Saturday...After isolated to scattered evening showers
and thunderstorms, concentrated east of an Alliance to Cheyenne
line, expect them to dissipate by or near midnight. GFS progs a low
level convergence boundary to form from Laramie to Sidney, thus will
paint isolated to scattered thunderstorms along this line Saturday
afternoon. Slightly cooler than Friday with additional cloud cover.

Sunday...Flow aloft remains southwest in advance of the upper
trough. Enough moisture for isolated afternoon and evening showers
and thunderstorms, mainly east of Interstate 25. Slightly cooler
again with cloud cover.

Monday...Upper trough moves eastward across eastern Montana with the
bulk of showers and thunderstorms up there. However, looks like we
will have enough moisture for isolated showers and thunderstorms
north of a Douglas to Kimball line.

Tuesday...Slow cooling trend continues per thickness and 700 mb
temperature trends. Though chances look minimal, we may see isolated
afternoon thunderstorms along and east of Interstate 25.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 520 AM MDT Wed Aug 31 2016

Wyoming TAFS...VFR at Rawlins. Localized MVFR at Laramie from
12Z to 15Z...otherwise VFR. MVFR at Cheyenne from 12Z to 14Z...
otherwise VFR.

Nebraska TAFS...IFR through 15Z...then VFR. IFR developing again
after 07Z.

&&

.FIRE WEATHER...
Issued at 300 AM MDT Wed Aug 31 2016

Elevated to critical fire weather conditions still a possibility
beginning Thursday but moreso Friday. Humidities may be an issue
Thursday as we are only getting small pockets of critical
humidities Thursday afternoon across western Converse and northern
Carbon County. Will let the day crew take another look before
hoisting any watches. Better day Friday as low pressure tracks
across Montana. Will see wind gusts in excess of 40MPH across
much of southeast Wyoming and Nebraska Panhandle Friday.
Humidities look there for areas west of the Laramie Range with
widely scattered dry thunderstorms. Front comes through Saturday
with cooler temperatures and higher humidities.

&&

.CYS Watches/Warnings/Advisories...
WY...None.
NE...Dense Fog Advisory until 9 AM MDT this morning for NEZ003-
     019>021-054-055-096.

&&

$$

UPDATE...GCC
SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...GCC



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