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000
FXUS63 KUNR 190517
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1117 PM MDT TUE JUN 18 2013

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 259 PM MDT TUE JUN 18 2013

CURRENT UPPER LEVEL ANALYSIS SHOWS A RIDGE OVER THE
CENTRAL CONUS...WITH A LOW PRESSURE SYSTEM PUSHING IN FROM THE
PACIFIC. A WAVE MOVING THROUGH THE RIDGE IS BEGINNING TO PRODUCE
SOME SHOWERS AND THUNDERSTORMS ACROSS WYOMING. SURFACE HIGH IS EAST
OF THE CWA...WITH THE SURFACE LOW MOVING IN FROM IDAHO. WINDS ARE
LIGHT AND SOUTHERLY WITH TEMPS RISING INTO THE UPPER 70S AND LOWER
80S.

THUNDERSTORMS...SOME OF WHICH MAY BE SEVERE WITH LARGE HAIL AND
STRONG WINDS...ARE EXPECTED TO MOVE INTO NORTHEAST WYOMING THIS
AFTERNOON AS THE SHORTWAVE PUSHES THROUGH THE RIDGE. HIGHEST MLCAPE
VALUES OF 1500 TO 2000 J/KG WILL BE MAINLY ACROSS NORTHEAST WYOMING
AND SOUTHERN SOUTH DAKOTA. BEST 0-6 KM SHEAR OF 35-40 KTS IS
EXPECTED OVER NORTHERN SOUTH DAKOTA AND NORTHEAST WYOMING LATE THIS
AFTERNOON AND THIS EVENING. STRONGEST CAP EXISTS ACROSS NORTHERN
SOUTH DAKOTA...AND SO STORMS SHOULD REMAIN FARTHER SOUTH. MODELS ARE
IN DISAGREEMENT ABOUT WHETHER STORMS ACROSS NORTHEAST WYOMING WILL
MAKE IT INTO SOUTH DAKOTA...ESPECIALLY AFTER 00Z. WITH CAPE
PREDICTED TO PERSIST ACROSS SOUTHERN SOUTH DAKOTA INTO THE EVENING
AND A LOW-LEVEL JET INCREASING DURING THE NIGHT...EXPECT STORMS TO
CONTINUE INTO THE EVENING AND MOVE EASTWARD OVERNIGHT AS THE WAVE
PUSHES THROUGH.

ON WEDNESDAY...THE PRESSURE GRADIENT WILL TIGHTEN AS THE SURFACE LOW
CONTINUES MOVING INTO THE REGION. SOUTHEAST WINDS WILL BECOME BREEZY
ACROSS THE SOUTH DAKOTA PLAINS. LOOKS LIKE A MARGINAL WIND ADVISORY
EVENT...SO LATER SHIFTS WILL NEED TO EXAMINE THAT POSSIBILITY
FURTHER. THE SOUTHERLY WINDS WILL ADVECT WARM AND MOIST AIR INTO THE
AREA...WITH HIGHS IN THE 80S TO LOWER 90S AND DEW POINTS ACROSS THE
SOUTH DAKOTA PLAINS IN THE LOWER 60S. A DRY LINE SETS UP ALONG THE
WY/SD BORDER BY WEDNESDAY EVENING. IMPRESSIVE CAPE VALUES AND
SUFFICIENT 0-6 KM SHEAR ACROSS THE WESTERN SOUTH DAKOTA PLAINS
SUGGEST THUNDERSTORMS ARE POSSIBLE AGAIN WEDNESDAY EVENING...SOME OF
WHICH MAY BECOME SEVERE.

&&

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 259 PM MDT TUE JUN 18 2013

WEAK COOL FRONT MOVES THROUGH THE CWFA ON THURSDAY WITH
DRY SLOT IN THE SW FLOW ALOFT...LEADING TO NEAR ZERO CAPE AND VERY
LIMITED MOISTURE IN ALL BUT OUR FAR ERN CWFA. THUS...MOSTLY DRY
CONDITIONS AND WARM TEMPS. UPPER LEVEL LOW OVER THE PAC NW/NRN
ROCKIES AND UPPER RIDGE TO OUR EAST WILL REMAIN IN PLACE THROUGH THE
FIRST PART OF THE WEEKEND...WITH A NEARLY DAILY CHANCE FOR TSTMS
UNDER CONTINUED SW FLOW ALOFT. FLOW THEN BECOMES INCREASINGLY ZONAL
FOR THE END OF THE WEEKEND INTO EARLY NEXT WEEK AS UPPER LOW PASSES
TO OUR NORTH...LEADING TO SMALLER CHANCES FOR TSTMS. EVEN WARMER
WEATHER BEGINS TO BUILD IN EARLY NEXT WEEK AS UPPER RIDGE BEGINS
BUILDING INTO THE NRN ROCKIES/NRN PLAINS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1104 PM MDT TUE JUN 18 2013

A STRONG UPPER LEVEL TROUGH WILL SHIFT NE INTO THE NORTHERN PLAINS
WEDNESDAY. STRONG SOUTHERLY WINDS WILL DEVELOP AS ASSOCIATED SFC LOW
PRESSURE MOVES INTO THE REGION...WITH ISOLD MORNING LL WIND SHEAR
POSSIBLE ACROSS SCENTRAL SD. A STRONG CAP SHOULD KEEP MOST
CONVECTION CONFINED TO THE FAR EASTERN FA AND EAST WED MORNING
ALONG THE NOSE OF THE LL JET. OTHERWISE...AN ISOLD TS WILL BE
POSSIBLE WED AFTERNOON/EVENING AHEAD OF THE ADVANCING SFC COLD
FRONT...POSSIBLY STEMMING FROM THE BLACK HILLS.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...POJORLIE
LONG TERM...JOHNSON
AVIATION...JC