Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 201746
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1045 AM MST Mon Nov 20 2017

.UPDATE...
Issued at 1013 AM MST Mon Nov 20 2017

Update to advance the high wind warning to now as winds have come
up over more of Laramie County. Also modified temps and clouds for
current observations.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 300 AM MST Mon Nov 20 2017

Winds the main forecast challenge today. They are already going
along and west of Laramie Range this morning.

Currently...Upper low visible on water vapor imagery this morning
tracking across northern Montana and as expected, winds are really
going to town out west. Camp Creek RAWS site just west of Muddy
Gap gusting in the upper 70s, Quealy Dome on I-80 in the Laramie
Valley hit 66mph earlier and the Summit is hitting fairly
widespread gusts above 60 mph so far this morning. With whats
going on at Camp Creek and Quealy Dome, decided to upgrade
previous watch and start it this morning instead of 11AM. Updates
have been sent on those upgrades.

Question continues for zones east of the Laramie Range. GFS
continues to showing +50kts right off the surface on both the GFS
and NAM soundings. Looks like we should easily mix into those
stronger winds on both soundings here at Cheyenne and possibly
Douglas, so went ahead and upgraded these watches to warnings as
well. GFS 750 and 800mb winds close to 60kts over Platte and
Goshen Counties this afternoon. Day crew may need to add Goshen
County into the warning if trends show winds hitting out there at
Torrington later this morning.

Pretty quick shot of snow over the Snowy and Sierra Madre Ranges
today/tonight and thats another area to watch. Am only getting 4
inches of snow in the Snowy Range in the forecast grids, but day
shift will need to monitor SNOTELS for heavier rates. Will hold
off on any advisories, but needs to be watched closely. Light
snow may continue out over the Snowy/Sierra Madre Ranges through
Tuesday before easing off.

.LONG TERM...(Wednesday night through Sunday)
Issued at 300 AM  MST Mon Nov 20 2017

Thanksgiving...Dry, mild and windy for the holiday with brisk
northwest flow aloft and decent surface lee troughing. Maximum
temperatures will climb into the 60s east of I-25 with 700 mb
temperatures near 5 Celsius.

Friday...Slightly cooler with a fast moving shortwave trough aloft
passage. Low and mid level moisture too scant for any precipitation.

Saturday...Warming trend begins anew as ridging aloft develops
across the Great Basin states with strengthening northwest flow
aloft over our counties, producing another windy day with near high
wind criteria winds possible across our wind prone locations. Dry
again with lack of low and mid level moisture.

Sunday...Ridge aloft moves overhead though with little temperature
changes noted. Lack of low and mid level moisture precludes mention
of precipitation.

&&

.AVIATION...(For the 18Z TAFS through Tuesday morning)

Main concern will be strong westerly winds across the region,
possibly extending as far east as the western Nebraska terminals
into tonight.  Although confidence with the wind forecast is high
through 00z this evening, there is limited confidence tonight as
mountain wave activity will likely keep winds on the high side
across southeast Wyoming. However, it will not be windy all the time
with brief lulls in the wind expected.

&&

.FIRE WEATHER...
Issued at 330 AM MST Mon Nov 20 2017

Elevated to locally critical fire weather conditions across the
southern Nebraska Panhandle and extreme southeast Wyoming today
(FWZ 310 and 313). Low pressure system tracking across Montana
today will increase winds over the area with many High WInd
Warnings in effect across southeast Wyoming. Downsloping winds off
the Laramie Range will create locally critical humidity across
southern 310 and 313 along with wind gusts exceeding 35 mph. Look
for increasing chances for some precipitation when the associated
cold front moves through tonight into Tuesday.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...High Wind Warning until 8 PM MST this evening for WYZ106-110-116-
     117.

     High Wind Warning until 5 PM MST this afternoon for WYZ101-104-
     105-107-115-118.

NE...None.
&&

$$

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



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