Area Forecast Discussion
Issued by NWS Cheyenne, WY

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474
FXUS65 KCYS 052158
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
258 PM MST FRI FEB 5 2016

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 204 PM MST FRI FEB 5 2016

A VERY WINDY PATTERN WILL EVOLVE ACROSS SOUTHEAST WY AND THE WESTERN
NE PANHANDLE OVER THE NEXT FEW DAYS. THE INHERITED HIGH WIND WARNING
FOR OUR WIND CORRIDORS ARE IN EXCELLENT SHAPE...SO NO CHANGES APPEAR
TO BE NECESSARY ATTM. A STRONG MID-LEVEL SHORTWAVE CURRENTLY LOCATED
OFF THE PACIFIC NW COAST WILL MOVE QUICKLY INTO WESTERN MONTANA THIS
EVENING AND OVERNIGHT...WITH LOW-LEVEL GRADIENTS INCREASING MARKEDLY
AS A RESULT. THE NAM H85 CAG-CPR GRADIENT CLIMBS TO 60 METERS BY 06Z
AND TO NEAR 90 METERS BY 15Z SAT. THIS...COMBINED WITH A BROAD SWATH
OF 55-65 KNOT FLOW AT H7-H8 OVER THE WIND CORRIDORS SHOULD SUPPORT A
FEW WIND GUSTS IN EXCESS OF 70 MPH. THIS WILL CONTINUE WELL INTO SAT
EVENING AS THE H7 CAG-CPR GRADIENT REMAINS ABOVE 60 METERS UNTIL 06Z
SUN AND THE MID-LEVEL WAVE TRACKS ACROSS NORTHEAST WY. SFC TEMPS ARE
GOING TO BE WARMER ON SATURDAY...SO CRUSTING OF SNOWPACK SHOULD TEND
TO LIMIT THE EXTENT OF BLOWING SNOW. THERE WILL CERTAINLY BE REDUCED
VISIBILITIES AND SLICK ROADS THOUGH...MAINLY ACROSS OUR PRIMARY WIND
CORRIDORS.

THERE IS STILL A LOT OF UNCERTAINTY WITH HOW THIS IS GOING TO EVOLVE
FOR SOME OF THE ADJACENT VALLEYS/HIGH PLAINS. MAV GUIDANCE IS COMING
IN LOWER WITH SUSTAINED WINDS ON SATURDAY AFTERNOON WITH NONE OF THE
SITES IN THE HIGH WIND WATCH EXCEEDING 27 KTS. OUR LOCAL PROBABILITY
GUIDANCE FOR 50 KNOT GUSTS AT CYS HAS TRENDED MUCH LOWER TOO. BUFKIT
SOUNDINGS FROM THE NAM AND GFS DO NOT SUGGEST EXCELLENT MIXING...BUT
STEEP ENOUGH LAPSE RATES FOR DOWNWARD MOMENTUM TRANSFER. BELIEVE THE
BEST DECISION IS TO LEAVE THE WATCH AS-IS AND LET THE MIDNIGHT SHIFT
RE-EVALUATE. WARNING-CRITERIA GUSTS ARE A POSSIBILITY WITH 55-65 KTS
UPSTAIRS...BUT OUR CONFIDENCE IN THIS SCENARIO IS LOW. BETTER CHANCE
FOR HIGH WINDS OVER THE EASTERN PLAINS MAY COME ON SUN WITH 55-65 KT
H75 FLOW OVERSPREADING ALL AREAS ALONG AND EAST OF THE LARAMIE RANGE
INCLUDING THE NEBRASKA PANHANDLE. THE LATEST MAV GUIDANCE FOR SIDNEY
SHOWS 37 KNOT SUSTAINED WINDS...SO LATER SHIFTS MAY NEED TO CONSIDER
A HIGH WIND WATCH FARTHER EAST.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 204 PM MST FRI FEB 5 2016

PRETTY QUIET WEATHER PATTERN IN THE EXTENDED PERIOD WITH AN UPPER
RIDGE ENTRENCHED ACROSS THE INTERMOUNTAIN WEST. NORTH TO
NORTHWESTERLY FLOW ALOFT WILL PREVAIL. IT WILL BE BREEZY TO WINDY
FROM SUNDAY NIGHT THROUGH TUESDAY ESPECIALLY TO THE EAST OF THE
LARAMIE RANGE WHERE THE MODELS SHOW 700 MB WINDS OF 40-55 KTS. THE
STRONGEST WINDS COULD ACTUALLY OCCUR SUNDAY NIGHT OVER THE
PANHANDLE WITH AROUND 60 KTS JUST A FEW THOUSAND FEET OFF THE SFC.
THE WINDS WOULD BE HIGHER IF THE LLVL LAPSE RATES WERE BETTER.
STILL...20-30 KTS OF SFC WIND WILL BE COMMON MUCH OF THE TIME
THROUGH TUES. BY WED AND INTO THURS THE MIDLVL JET WILL SHIFT WELL
EASTWARD INTO MINNESOTA/IOWA. TEMPS WILL WARM THROUGH THE MIDDLE
OF THE WEEK WITH HIGHS 10-15 DEGREES ABOVE NORMAL BY THURS. PRECIP
CHANCES ARE SLIM WITH THE UPPER RIDGE NEARBY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1057 AM MST FRI FEB 5 2016

VFR CONDITIONS THROUGH THE TAF PERIOD. WINDS WILL GUST TO 25-30
KTS THROUGH THE AFTERNOON. THE WINDS WILL DECREASE ACROSS THE
NEBRASKA PANHANDLE AFTER 00Z...BUT REMAIN BREEZY OVER SOUTHEAST
WYOMING THROUGH THE NIGHT. CLOUDS WILL MOSTLY BE LIMITED TO MID-
TO-HIGH LEVEL.

&&

.FIRE WEATHER...
ISSUED AT 204 PM MST FRI FEB 5 2016

STRONG WINDS RETURN TO SOUTHEAST WYOMING AND ARE LIKELY TO BECOME
WIDESPREAD ACROSS THE AREA SATURDAY. HIGH WIND WARNINGS HAVE BEEN
POSTED FOR THE WIND PRONE AREAS OF SOUTHEAST WYOMING FOR WIND
GUSTS IN EXCESS OF 70 MPH WITH HIGH WIND WATCHES FOR MANY OF THE
LOWER AREAS SATURDAY. THESE WINDS WILL SPREAD OUT INTO THE
NEBRASKA PANHANDLE SATURDAY NIGHT INTO SUNDAY AND WIND HEADLINES
WILL LIKELY BE NEEDED OUT THERE AS WELL. WITH AN ABUNDANT SNOW
PACK THOUGH...FIRE WEATHER CONCERNS SHOULD BE MINIMAL.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING FROM 8 PM THIS EVENING TO 11 PM MST SATURDAY
     FOR WYZ106-110-116-117.

     HIGH WIND WATCH FROM SATURDAY MORNING THROUGH SATURDAY EVENING
     FOR WYZ101-104-105-107-109-115.

NE...NONE.
&&

$$

SHORT TERM...CLH
LONG TERM...ZF
AVIATION...ZF
FIRE WEATHER...CLH



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