000
FXUS65 KCYS 171057
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
457 AM MDT MON JUN 17 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 430 AM MDT MON JUN 17 2013

THE GOES WATER VAPOR IMAGERY LOOP SHOWED A UPPER RIDGE AXIS FROM
THE TEXAS BIG BEND TO WESTERN MONTANA. A POTENT SHORTWAVE WAS
PROVIDING LARGE SCALE LIFT FOR A MESOSCALE CONVECTIVE SYSTEM
PROPAGATING SOUTHEAST ACROSS THE SOUTHERN PLAINS. A WEAKER WAVE
WAS MOVING EAST-SOUTHEAST THROUGH EASTERN WYOMING AND WESTERN
SOUTH DAKOTA. CONVECTION ASSOCIATED WITH THIS WAVE HAS HAD A
HISTORY OF PRODUCING LOCALLY HEAVY RAINFALL. RADAR ESTIMATES OF
TWO TO FOUR INCHES WERE OBSERVED OVER NORTHWEST CONVERSE COUNTY
SINCE MIDNIGHT. THE SHOWERS AND TSTORMS WILL CONTINUE TO PROGRESS
EAST-SOUTHEAST INTO THE NORTHERN NEBRASKA PANHANDLE THROUGH EARLY
MORNING. ELSEWHERE...IT WAS DRY WITH MOSTLY CLEAR SKIES AND
TEMPERATURES IN THE 40S AND 50S.

THE LATEST SHORT RANGE MODEL GUIDANCE INDICATES THAT THE UPPER
RIDGE TO THE WEST WILL GET NUDGED EASTWARD DURING THE NEXT 24
HOURS AS THE CLOSED LOW OFFSHORE THE PACIFIC NORTHWEST MOVES
INLAND. THE RIDGE WILL BE SITUATED ALONG THE FRONT RANGE TONIGHT
AND HIGH PLAINS ON TUESDAY. THE SHORTWAVE RESPONSIBLE FOR THIS
MORNING`S CONVECTION WILL MOVE SOUTHEAST INTO CENTRAL NEBRASKA
THIS AFTERNOON. THE NEXT SHORTWAVE TO AFFECT THE REGION MOVES
THROUGH THIS EVENING. SIMILAR TO YESTERDAY...CONVECTION WILL FORM
OVER THE HIGHER TERRAIN AND INCREASE IN COVERAGE AND INTENSITY
WHEN ENCOUNTERING THE MOIST AND UNSTABLE AIR MASS EAST OF THE
LARAMIE RANGE WHERE SBCAPES OF 1500-2000 J/KG ARE FORECAST.
LARGE SCALE SHEAR OF 40 TO 50 KT IN STRONG UPSLOPE FLOW REGIME
WILL SET THE STAGE FOR STRONG TO SEVERE TSTORMS OVER THE SOUTHEAST
WYOMING PLAINS AND SOUTHERN NEBRASKA PANHANDLE FROM MID AFTERNOON
THROUGH MID EVENING....AS INDICATED BY THE SPC DAY1 OUTLOOK. THE
MAIN THREATS WITH THESE STORMS WILL BE DAMAGING WINDS AND LARGE
HAIL. AN ISOLATED TORNADO OR TWO CANNOT BE RULED OUT AS WELL.

THE SHOWERS AND TSTORMS WILL COME TO AN END FOR ALL BUT THE
SOUTHEAST PANHANDLE ZONES LATER THIS EVENING. TUESDAY WILL BE
SIMILAR TO TODAY WITH REGARD TO DIURNAL TSTORM COVERAGE...HOWEVER
THE SEVERE THREAT WILL BE MINIMAL WITH THE MID/UPPER LEVEL RIDGE
OVER THE HIGH PLAINS. THIS WILL LIMIT TSTORM COVERAGE AND DEEP
LAYER SHEAR AS WINDS WILL BE LIGHTER.

HIGH TEMPERATURES TODAY WILL BE WARMER OVER LOWER ELEVATIONS OF
CARBON COUNTY WHERE 700MB TEMPERATURES WARM TO 12 TO 14C. ELSEWHERE...
700MB TEMPERATURES WILL RANGE BETWEEN 8 AND 11C...WHICH WILL YIELD
SEASONAL TEMPERATURES IN THE 70S TO LOWER 80S. LOW TEMPERATURES
TONIGHT WILL BE IN THE 40S AND 50S. HIGH TEMPERATURES TUESDAY WILL
AVERAGE ABOUT 5 DEGREES WARMER WITH 700MB TEMPERATURES FROM 11 TO
15C.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 500 AM MDT MON JUN 17 2013

A FAIRLY ACTIVE PATTERN WILL CONTINUE THROUGH THE LONG TERM PERIOD
AS AN UPPER LOW SLOWLY MOVES ACROSS THE PAC NW AND KEEPS THE ROCKIES
IN AN ENERGETIC SOUTHWEST FLOW PATTERN. THE THERMAL RIDGE WILL BE
OVERHEAD ON WEDNESDAY WHICH WILL KEEP TEMPERATURES IN THE 80S AND
90S. VERY WARM TEMPS ALOFT AS WELL WILL CAP THE ENVIRONMENT FOR MUCH
OF THE DAY...BUT AN APPROACHING SHORTWAVE AND DIFFLUENT FLOW REGION
OF THE UPPER JET COULD TRIGGER STORMS IN THE LATE AFTERNOON AND EVENING
ALONG THE DRYLINE WHICH LOOKS TO SET UP ALONG THE WY/NE BORDER. A
FEW STORMS COULD ALSO FORM OFF THE MOUNTAINS ALTHOUGH MOISTURE MAY
BE LIMITED ENOUGH TO KEEP ONLY DRY AND BREEZY CONDITIONS HERE.
STRONG MOISTURE ADVECTION ACROSS THE EASTERN PLAINS AHEAD OF THE
WAVE WILL INCREASE CAPE VALUES TO AROUND 3000 J/KG IN THE
PANHANDLE...ALTHOUGH AGAIN THE CAP WILL LIMIT COVERAGE AND INTENSITY
OF STORMS AT FIRST. TIMING OF THE STRONGEST FORCING LOOKS TO
COINCIDE WITH THE LLVL JET FORMATION...AND WITH AROUND 2500 J/KG OF
CAPE TO PERSIST IN THE PANHANDLE...LIKELY WILL SEE CONVECTION
INTENSIFY IN THIS AREA LATE EVENING AND CONTINUE EASTWARD OVERNIGHT.
SOME STORMS COULD BE STRONG AT TIMES DUE TO THE HIGH POTENTIAL
INSTABILITY STILL IN PLACE AS THE WAVE MOVES ACROSS THE FORECAST
AREA OVERNIGHT.

THE DRYLINE WILL PUSH TO THE EAST ON THURSDAY SO CONVECTION SHOULD
BE LIMITED TO THE FAR EASTERN ZONES IN THE LATE AFTERNOON AND
EVENING. A DEVELOPING SFC LOW OVER THE CENTRAL PLAINS WILL DRAG A
FRONT SOUTH ACROSS THE EASTERN PLAINS ON FRIDAY WITH A BROADER
COVERAGE OF SHOWERS AND STORMS DEVELOPING ALONG THIS FRONTAL
CONVERGENCE BOUNDARY. THE MAIN UPPER WAVE OVER THE PAC NW WILL
FINALLY BEGIN TO MOVE OVER THE NORTHERN ROCKIES ON SATURDAY WITH A
DEEPER FETCH OF MID AND UPPER LEVEL MOISTURE MOVING OVER THE FORECAST
AREA FOR SATURDAY AND SUNDAY. WILL MAINTAIN CHANCES FOR SHOWERS AND
THUNDERSTORMS MAINLY ACROSS THE EASTERLY PLAINS THROUGH THIS TIME
ALTHOUGH CANNOT RULE OUT A FEW STORMS DEVELOPING OVER THE HIGH
TERRAIN AS WELL WITHIN THE DEEPER MOISTURE PLUME. TEMPERATURES WILL
REMAIN VERY WARM THROUGH THE PERIOD...WITH VERY DRY AND BREEZY
CONDITIONS PERSISTING FOR AREAS WEST OF THE LARAMIE RANGE WHICH WILL
MAINTAIN ELEVATED FIRE WEATHER CONCERNS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 430 AM MDT MON JUN 17 2013

WIDELY SCATTERED SHOWERS AND TSTORMS WILL CONTINUE TO PROPAGATE
TO THE EAST AND SOUTHEAST ACROSS EAST CENTRAL WYOMING AND THE
NORTHERN NEBRASKA PANHANDLE THIS MORNING. ALSO...PATCHY MVFR TO
IFR CEILINGS AND VISIBILITIES WILL DEVELOP OVER SOUTHERN PORTIONS
OF THE NEBRASKA PANHANDLE AND PERSIST UNTIL MID MORNING. SCATTERED
AFTERNOON AND EVENING TSTORMS WILL FORM OVER THE LARAMIE RANGE
EARLY AFTERNOON THEN MOVE EAST ONTO THE PLAINS. LOCAL MVFR TO
IFR CONDITIONS AND GUSTY/ERRATIC WINDS WILL BE POSSIBLE WITH SOME
OF THE TSTORMS.

&&

.FIRE WEATHER...
ISSUED AT 307 AM MDT MON JUN 17 2013

AN UPPER RIDGE OF HIGH PRESSURE TO THE WEST WILL SLOWLY MOVE EAST
ACROSS THE FRONT RANGE AND HIGH PLAINS THROUGH TUESDAY. WEAK
DISTURBANCES ALOFT WILL INTERACT WITH THE MOIST AND UNSTABLE AIR
MASS OVER THE EASTERN PLAINS AND WESTERN PANHANDLE THE NEXT FEW
DAYS. ISOLATED TO SCATTERED AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS WILL DEVELOP OVER THE LARAMIE RANGE AND INTENSIFY AS
THEY MOVE TO THE EAST. LOCALLY HEAVY RAINFALL...HAIL AND GUSTY
WINDS WILL BE POSSIBLE WITH THE STRONGER STORMS. ISOLATED GUSTY
THUNDERSTORMS PRODUCING LITTLE RAINFALL ARE EXPECTED FOR AREAS
WEST OF THE LARAMIE RANGE WHERE RELATIVE HUMIDITIES WILL BE LOW.
SEASONAL TEMPERATURES WILL GRADUALLY WARM TO ABOVE NORMAL BY MID
WEEK AS THE RIDGE MOVES INTO THE GREAT PLAINS. FOR THE LATTER HALF
OF THE WEEK...IT WILL BE DRIER FOR SOUTHEAST WYOMING...WHILE
ISOLATED LATE DAY THUNDERSTORMS WILL BE POSSIBLE FOR THE WESTERN
NEBRASKA PANHANDLE.

&&

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

$$

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