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000
FXUS65 KCYS 112204
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
304 PM MST WED DEC 11 2013

.SHORT TERM...(THIS AFTERNOON THROUGH FRIDAY NIGHT)
ISSUED AT 230 PM MST WED DEC 11 2013

THE AFTERNOON WATER VAPOR IMAGERY DEPICTED A UPPER LOW BENEATH A
RIDGE AXIS ALONG THE NORTHERN PACIFIC COAST...AND A TROUGH AXIS
EAST OF THE MISSISSIPPI RIVER. UPPER LEVEL MOISTURE IN THE FORM OF
CIRRUS WAS STREAMING NORTHWEST TO SOUTHEAST ACROSS THE REGION.
FILTERED SUNSHINE AND GUSTY WEST TO SOUTHWEST WINDS PUSHED THE
MERCURY INTO THE 20S AND 30S MOST AREAS. STRONGEST GUSTS HAVE BEEN
45 TO 55 MPH THROUGH THE WIND CORRIDORS OF ARLINGTON AND ELK
MOUNTAIN AS WELL AS NEAR BORDEAUX...AND THESE WIND SPEEDS WILL
PERSIST THROUGH THE LATE AFTERNOON. A FEW GUSTS OF 58 MPH OR
HIGHER WILL BE POSSIBLE.

THE CONSENSUS MODEL GUIDANCE SHOWS THE RIDGE OUT WEST GRADUALLY
DE-AMPLIFYING AS IT PROGRESSES EAST ACROSS THE GREAT BASIN AND
CONTINENTAL DIVIDE THROUGH THURSDAY. A WEAK SHORTWAVE WILL MOVE
FROM MONTANA INTO THE DAKOTAS TONIGHT AND THURSDAY. THIS SYSTEM
WILL TIGHTEN THE LOW LEVEL PRESSURE GRADIENT RESULTING IN A
CONTINUATION OF THE GUSTY WEST TO SOUTHWEST WINDS OVER MUCH OF
SOUTHEAST WYOMING. GFS TIME HEIGHT CROSS SECTIONS INDICATE 700MB
WINDS OF 45 TO 50 KT WITH CRAIG TO CASPER 850MB HEIGHT DIFFERENCES
OF 50 TO 60M BETWEEN 12Z THURSDAY AND 00Z FRIDAY. GUSTS OF 45 TO
55 MPH ARE EXPECTED IN AND NEAR ARLINGTON...ELK MOUNTAIN AND
BORDEAUX TONIGHT AND THURSDAY. CANNOT RULE OUT A FEW GUSTS OF 58
MPH OR HIGHER. GIVEN THE MARGINAL NATURE OF THE EVENT...DO NOT
ANTICIPATE ANY HIGH WIND HEADLINES ATTM. LATER SHIFTS WILL NEED TO
MONITOR WIND OBS AND REVIEW 00Z MODEL DATA FOR POTENTIAL HEADLINES.
LOWS TONIGHT WILL BE COLDEST SINGLE DIGITS ABOVE ZERO FOR THE
VALLEYS AND RIDGES...WITH TEENS TO MID 20S ELSEWHERE. 700MB
TEMPERATURES RECOVER TO 0C TO 4C THURSDAY AFTERNOON WITH HIGHS IN
THE 40S LEE OF THE LARAMIE RANGE WITH DUE TO A DOWNSLOPING WIND
COMPONENT. AREAS ALONG AND WEST OF THE LARAMIE RANGE WILL BE IN
THE 20S AND 30S.

A SHORTWAVE TROUGH OVER THE PACIFIC NORTHWEST QUICKLY MOVES
SOUTHEAST ACROSS THE CWA FRIDAY...PUSHING A SURFACE COLD FRONT
THROUGH. MOISTURE FOR PRECIPITATION WILL BE LIMITED TO THE HIGHER
TERRAIN...WITH LIGHT SNOW FRIDAY AND FRIDAY NIGHT OVER THE SNOWY
AND SIERRA MADRES. ACCUMULATIONS OF AN INCH OR TWO WILL BE
POSSIBLE. IT WILL BE ABOUT 10 DEGREES COOLER AS 700MB TEMPERATURES
LOWER TO -5 TO -7C. HIGHS FRIDAY WILL BE IN THE 30S TO NEAR 40
EAST WITH 20S WEST. IT WILL BE BRISK FRIDAY WITH WEST TO NORTHWEST
WINDS 15 TO 25 MPH AND GUSTY.

.LONG TERM...(SATURDAY THROUGH TUESDAY NIGHT)
ISSUED AT 300 PM MST WED DEC 11 2013

GENERALLY FAST NORTHWEST FLOW WILL BE OVERHEAD THROUGH THE PERIOD...
WITH THE CWA ON THE SOUTHERN AND DRIER FRINGE OF THE UPPER LEVEL
JET. OUTSIDE OF A FEW MOUNTAIN SHOWERS EARLY IN THE PERIOD AS
SHORTWAVE ENERGY MOVES OVER THE NORTHERN ROCKIES...WILL REMAIN DRY
ACROSS THE FORECAST AREA. THE MAIN CONSTANT THROUGH THE LONG TERM
WILL BE WINDY CONDITIONS ACROSS SOUTHEAST WYOMING WITH MILD TEMPS
ACROSS THE EASTERN PLAINS DUE TO DOWNSLOPE EFFECTS.

THE AFOREMENTIONED SHORTWAVE WILL MOVE ACROSS THE NORTHERN ROCKIES
SATURDAY AND SATURDAY NIGHT...AND WILL RAPIDLY DEEPEN THE LEE-SIDE
PRESSURE TROUGH THROUGH SUNDAY MORNING. WAA WILL OCCUR AHEAD OF THE
WAVE AND WILL INITIALLY STRENGTHEN THE LOW LEVEL INVERSION OVER THE
CWA BEFORE THE COLD BL MIXES OUT. THIS INVERSION WILL COMBINE WITH
THE STRENGTHENING GRADIENT TO PRODUCE STRONG WINDS IN THE GAP
REGIONS OUT WEST. COULD BE CLOSE TO HIGH WIND CRITERIA BOTH DAYS
SO WILL HAVE TO KEEP A CLOSE EYE ON THIS SCENARIO OVER THE NEXT
FEW DAYS. WINDY CONDITIONS WILL CONTINUE TUESDAY...WITH SLIGHTLY
COOLER TEMPS EXPECTED AS A WEAK COOL FRONT MOVES ACROSS THE EASTERN
PLAINS TUESDAY MORNING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY MORNING)
ISSUED AT 1113 AM MST WED DEC 11 2013

VFR CONDITIONS WILL PERSIST THROUGH THE PERIOD...WITH A HIGH CLOUD
DECK MOVING OVERHEAD FROM THE NORTH. WESTERLY WINDS WILL GUST AS
HIGH AS 45 KT IN AREAS ALONG AND WEST OF THE LARAMIE RANGE THROUGH
THURSDAY....WITH 25 TO 35 KT EXPECTED AT THE WYOMING TERMINALS THIS
AFTERNOON AND THEN AGAIN LATE TONIGHT. MODERATE LOW LEVEL TURBULENCE
IS LIKELY OVER THE CWA DUE TO MOUNTAIN WAVE ACTIVITY WITH THESE
MODERATE WINDS IN PLACE.

&&

.FIRE WEATHER...
ISSUED AT 200 PM MST WED DEC 11 2013

NO FIRE WEATHER CONCERNS ARE EXPECTED FOR THE NEXT FEW DAYS WITH A
FAIRLY EXTENSIVE SNOW PACK...COOL TO COLD TEMPERATURES AND MINIMUM
RELATIVE HUMIDITIES OF 30 TO 40 PERCENT. GUSTY WEST TO SOUTHWEST
WINDS WILL PREVAIL OVER SOUTHEAST WYOMING...WITH STRONGEST GUSTS
OF 45 TO 55 MPH ALONG AND WEST OF THE LARAMIE RANGE THIS AFTERNOON
THROUGH THURSDAY. A COLD FRONT WILL MOVE THROUGH THE DISTRICTS
FRIDAY...BRINGING COOLER TEMPERATURES AND A CHANCE FOR SNOW FOR
THE SNOWY AND SIERRA MADRE RANGES INTO SATURDAY. DRIER...WARMER
AND WINDY CONDITIONS ARE FORECAST FOR LATE WEEKEND AND EARLY NEXT
WEEK.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&

$$

SHORT TERM...JAMSKI
LONG TERM...RJM
AVIATION...RJM
FIRE WEATHER...JAMSKI