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000
FXUS65 KCYS 170456
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1056 PM MDT THU MAY 16 2013

.UPDATE...
ISSUED AT 727 PM MDT THU MAY 16 2013

OTHER THAN A COUPLE THUNDERSTORM CELLS OVER SOUTHEAST LARAMIE
COUNTY AND WESTERN KIMBALL COUNTY...THUNDERSTORMS HAVE ALL BUT
ENDED ACROSS THE FORECAST. THESE REMAINING STORMS SHOULD MEET A
QUICK DEMISE OVER THE NEXT HOUR OR TWO. OTHERWISE ONLY ISOLATED
SHOWERS THIS EVENING WITH SHOWERS EVENTUALLY ENDING AND SKIES
CLEARING.

UPDATE ISSUED AT 421 PM MDT THU MAY 16 2013

MOST THUNDERSTORM ACTIVITY IS CURRENTLY OVER THE NEBRASKA
PANHANDLE WITH ONE STORM OVER NIOBRARA COUNTY IN SOUTHEAST
WYOMING. THESE STORMS...A FEW OF WHICH PRODUCED HALF INCH
SIZED HAIL AND WIND GUSTS TO 50 TO 60 MPH HAVE WEAKENED
SUBSTANTIALLY AND WILL CONTINUE TO DO SO THE REST OF THE
AFTERNOON AND WILL MOVE EAST OF THE AREA BY EARLY THIS
EVENING. BRIEF HEAVY RAIN AND WIND GUSTS TO 40 MPH WILL BE
POSSIBLE OVER THE NEXT FEW HOURS...OTHERWISE SKIES WILL BEGIN
TO CLEAR WHILE SHOWERS AND THUNDERSTORMS DIE OFF.

A FEW STRONG GUSTS WERE ALSO REPORTED THIS AFTERNOON OVER CARBON
COUNTY BUT WERE ASSOCIATED MAINLY WITH LIGHT RAIN SHOWERS. WINDS
HAVE BEGUN TO RELAX AND SHOULD BECOME LIGHT THIS EVENING WHILE
SKIES CLEAR.

&&

.SHORT TERM...(TONIGHT THROUGH SATURDAY)
ISSUED AT 248 PM MDT THU MAY 16 2013

WATER VAPOR LOOP AT MID AFTERNOON SHOWED A SHORTWAVE TROUGH MOVING
INTO WESTERN NEBRASKA. WIDELY SCATTERED STRONG CONVECTION DEVELOPED
ON THE BACKSIDE OF THE TROUGH SHORTLY AFTER MIDDAY OVER SOUTHEAST
WYOMING AND WESTERN NEBRASKA PANHANDLE. GUSTY WINDS TO 55 MPH...PEA
TO PENNY SIZE HAIL AND LOCALLY HEAVY RAIN HAVE BEEN THE BYPRODUCTS
OF THESE THUNDERSTORMS.

THE 12Z NAM AND SREF INDICATE THAT THE THUNDERSTORMS WILL END
FROM WEST TO EAST EARLY THIS EVENING AS THE TROUGH MOVES INTO THE
PLAINS AND DIABATIC COOLING STABILIZES THE LOWER AND MIDDLE
ATMOSPHERE. MID/UPPER RIDGE AMPLIFIES OVER THE PLAINS FRIDAY WITH
DRIER MORE STABLE AIRMASS DOMINATING THE REGION. 700MB TEMPERATURES
CREEP UP INTO THE LOWER TEENS CELSIUS FRIDAY AFTERNOON...YIELDING
HIGHS IN THE 80S TO AROUND 90 EAST OF THE LARAMIE RANGE. SURFACE
TROUGH/DRYLINE SETS UP OVER WESTERN NEBRASKA FRIDAY WITH HIGHER
INSTABILITY OVER THE CENTRAL PLAINS. WEST TO SOUTHWEST SURFACE
WINDS WILL BECOME QUITE GUSTY FROM LATE MORNING THROUGH THE
AFTERNOON...MAINLY ALONG AND WEST OF THE LARAMIE RANGE.

A PACIFIC COLD FRONT OVER NORTHWEST WYOMING FRIDAY AFTERNOON WILL
MOVE THROUGH SOUTHEAST WYOMING LATE FRIDAY NIGHT AND WESTERN
NEBRASKA PANHANDLE EARLY SATURDAY MORNING. 700MB TEMPERATURES FALL
BACK TO 4 TO 8 DEGREES CELSIUS SATURDAY AFTERNOON. THERE WILL
BE A 10 TO 15 DEGREE WEST TO EAST TEMPERATURE GRADIENT...RANGING
FROM 60S WEST TO LOWER 80S EAST. SOUTHWEST FLOW ALOFT WILL
TRANSPORT PACIFIC MOISTURE AND FORCING FROM SHORTWAVE ENERGY
AHEAD OF THE UPPER TROUGH PRODUCING SCATTERED SHOWERS AND
AFTERNOON THUNDERSTORMS FOR SATURDAY. NO SEVERE THUNDERSTORMS
ARE EXPECTED...BUT MODERATE RAINFALL AND GUSTY WINDS WILL BE
POSSIBLE.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 248 PM MDT THU MAY 16 2013

HIGH CONFIDENCE IN MODEL SOLUTIONS DUE TO STRONG MODEL SYNOPTIC
CONSISTENCY.

SATURDAY NIGHT...ISOLATED TO SCATTERED SHOWERS AND A FEW
THUNDERSTORMS IN THE POST FRONTAL AIRMASS WITH THE NEGATIVELY TILTED
SHORTWAVE TROUGH PASSING OVERHEAD.

SUNDAY...REFRESHINGLY COOL...BREEZY AND SHOWERY DAY WITH LARGE SCALE
UPPER TROUGH OVERHEAD. LOOKS LIKE MOST AREAS WILL RECEIVE BENEFICIAL
MEASURABLE RAIN WITH ADEQUATE LOW AND MID LEVEL MOISTURE...MESOSCALE
AND SYNOPTIC LIFT...THOUGH SOME RAIN SHADOWING EFFECTS NOTED
DOWNWIND OF THE LARAMIE RANGE ALONG INTERSTATE 25 DUE TO LOW LEVEL
DOWNSLOPING.

MONDAY...CLOSED AND STACKED UPPER TROUGH MOVES ACROSS SOUTH DAKOTA.
STILL ENOUGH LOW AND MID LEVEL MOISTURE FOR SCATTERED AFTERNOON AND
EVENING SHOWERS AND ISOLATED THUNDERSTORMS IN THE CYCLONIC FLOW
ALOFT.

TUESDAY...WARMING AND DRYING TREND AS SHORTWAVE RIDGING OCCURS OVER
WYOMING AND LOW AND MID LEVEL MOISTURE DECREASE.

WEDNESDAY...PROGRESSIVE SHORTWAVE RIDGING WILL PREVAIL AND COMBINED
WITH LIMITED LOW AND MID LEVEL MOISTURE...THUNDERSTORMS WILL BE
QUITE UNLIKELY.

THURSDAY...FLOW ALOFT TURNS SOUTH AS THE NEXT DEEP UPPER TROUGH
APPROACHES FROM THE WESTERN UNITED STATES. ASSOCIATED SURFACE WINDS
WILL BE STRONG SOUTHEASTERLY UPSLOPE IN RESPONSE ADVECTING LOW LEVEL
MOISTURE NORTHWESTWARD ACROSS OUR COUNTIES. AS A SHORTWAVE TROUGH
ALOFT ROTATES NORTHEAST ACROSS COLORADO...EXPECT SCATTERED AFTERNOON
THUNDERSTORMS TO ERUPT ALONG THE SPINE OF THE LARAMIE RANGE AND
INTERSTATE 25 CORRIDOR WITH MECHANICAL LIFT AND DIFFLUENCE ALOFT AND
SHORTWAVE TROUGH ENERGY. THIS WILL BE THE FIRST OF SEVERAL DAYS OF
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS...SOME STRONG AND
POSSIBLY SEVERE...NEAR OUR CLIMATOLOGICALLY FAVORED TIME OF YEAR IN
LATE MAY AND EARLY JUNE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY EVENING)
ISSUED AT 1047 PM MDT THU MAY 16 2013

WINDS WILL BE ON THE LIGHT SIDE TONIGHT BUT GUSTY WEST WINDS WILL
BE FOUND ACROSS SOUTHEAST WYOMING FRIDAY AFTERNOON WITH GUST OF
25 TO 35 MPH. WINDS WILL DROP OFF AND BECOME LIGHT FRIDAY NIGHT.
VFR THROUGH THE TAF PERIOD WITH SCATTERED HIGH CLOUDS.

&&

.FIRE WEATHER...
ISSUED AT 248 PM MDT THU MAY 16 2013

A WEAK UPPER LEVEL DISTURBANCE WILL MOVE ACROSS THE DISTRICTS THIS
AFTERNOON AND EARLY EVENING WITH WIDELY SCATTERED THUNDERSTORMS
BRINGING BRIEF LOCALLY HEAVY WETTING RAINFALL. WARMER AND DRIER
CONDITIONS ARE FORECAST FOR FRIDAY AS A UPPER LEVEL RIDGE OF HIGH
PRESSURE MOVES ACROSS THE FRONT RANGE AND HIGH PLAINS. GUSTY WINDS
AND LOW RELATIVE HUMIDITIES FOR VALLEYS WEST OF THE LARAMIE RANGE
WILL ENHANCE THE FIRE WEATHER THREAT. ELSEWHERE IN SOUTHEAST
WYOMING...FUELS ARE IN GREEN-UP STAGE. FOR THE WESTERN PANHANDLE...
FUELS ARE READY...HOWEVER WINDS WILL BE LIGHTER. COOLER AND SHOWERY
WEATHER WILL BECOME WIDESPREAD THIS WEEKEND INTO EARLY NEXT WEEK
AS A UPPER LEVEL TROUGH MOVES SLOWLY ACROSS THE CENTRAL ROCKIES
AND HIGH PLAINS. SCATTERED THUNDERSTORMS WILL BE POSSIBLE BOTH
SATURDAY AND SUNDAY...MAINLY DURING THE AFTERNOON AND EVENING.
DRIER AND WARMER CONDITIONS RETURN AGAIN BY THE MIDDLE OF NEXT WEEK.

&&

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

$$

UPDATE...LIEBL
SHORT TERM...JAMSKI
LONG TERM...RUBIN
AVIATION...LIEBL
FIRE WEATHER...JAMSKI