000 
FXUS63 KUNR 300837
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
237 AM MDT SAT MAY 30 2009

.DISCUSSION...CURRENT WATER VAPOR IMAGERY SHOWS RIDGE ACROSS THE
WESTERN CONUS WITH TROUGH OVER THE EASTERN CONUS. WEAK SHORTWAVE
WILL MOVE ACROSS THE CWA TODAY AND IS EXPECTED TO TRIGGER A FEW
SHOWERS AND THUNDERSTORMS ACROSS NORTHEAST WYOMING AND THE
NORTHERN BLACK HILLS. THE NAM IS INDICATING AROUND 750 J/KG CAPE
BY TOMORROW AFTERNOON ACROSS PORTIONS OF NORTHEAST WYOMING. GIVEN THE
CAPE AND FORECAST SOUNDINGS INDICATING RATHER DRY LOWER LEVELS OF
THE ATMOSPHERE...A FEW STORMS COULD PRODUCE GUSTY WINDS ALONG WITH SOME
SMALL HAIL.

NORTHWEST FLOW ALOFT WILL REMAIN OVER THE CWA TODAY BEFORE
TRANSITIONING TO ZONAL FLOW LATE TONIGHT. A COLD FRONT WILL
APPROACH THE CWA LATE TONIGHT AND IS EXPECTED TO MAKE ITS WAY INTO
NORTHEAST WYOMING AND FAR NORTHWEST SOUTH DAKOTA EARLY SUNDAY
MORNING. SOUTHWESTERLY WINDS OVER THE BLACK HILLS AHEAD OF
APPROACHING FRONT WILL KEEP TEMPERATURES WARM OVERNIGHT ACROSS THE
EASTERN FOOTHILLS. SHOWERS AND THUNDERSTORM ARE EXPECTED TO
DEVELOP ALONG AND AHEAD OF THE COLD FRONT SUNDAY MORNING AS IT
MAKES ITS WAY INTO SOUTH CENTRAL SOUTH DAKOTA BY LATE SUNDAY
AFTERNOON. SHEAR WILL BE ON THE WEAK SIDE. HOWEVER...CAPE VALUES
AROUND 1000 J/KG MAY SUPPORT A FEW STRONG STORMS ESPECIALLY ACROSS
SOUTH CENTRAL SOUTH DAKOTA SUNDAY AFTERNOON. INSTABILITY IS
EXPECTED TO LINGER OVER NORTHEAST WYOMING AND WESTERN SOUTH DAKOTA
BEHIND THE FRONT. WEAK SHORTWAVES MOVING ACROSS THE AREA SUNDAY
AFTERNOON INTO SUNDAY NIGHT WILL TRIGGER ADDITIONAL SHOWER AND
THUNDERSTORM ACTIVITY ACROSS MUCH OF THE CWA.

STRONGER SHORTWAVE WILL MOVE ACROSS THE CWA ON MONDAY AS FRONTAL
BOUNDARY SETS UP FROM NORTHERN IOWA...ACROSS NEBRASKA...AND INTO
NORTHEAST COLORADO. SHOWERS AND THUNDERSTORMS CAN BE EXPECTED
ACROSS MOST OF THE CWA ON MONDAY. A NARROW AXIS OF INSTABILITY
WILL BE FOUND OVER THE BLACK HILLS AND INTO THE NEBRASKA PANHANDLE
MONDAY AFTERNOON. A FEW STRONG THUNDERSTORMS MAY DEVELOP ACROSS
THESE AREAS MONDAY AFTERNOON INTO EARLY MONDAY EVENING. GIVEN THE
RATHER WEAK SHEAR PROFILES AND SLOW STORM MOTION...SOME STORMS
COULD PRODUCE HEAVY RAIN. PRECIPITATION WILL TAPER OFF MONDAY
NIGHT AS SURFACE HIGH PRESSURE BUILDS INTO THE CWA.

EXTENDED...QUASI ZONAL FLOW ALOFT WILL TRANSITION TO SOUTHWESTERLY 
FLOW LATE IN THE WEEK...KEEPING A SLIGHT CHANCE OF SHOWERS AND 
THUNDERSTORMS IN THE FORECAST FROM TUESDAY THROUGH SATURDAY. 
TEMPERATURES WILL BE SLIGHTLY BELOW AVERAGE AROUND MIDWEEK...WITH A 
SLOW WARM UP INTO NEXT WEEKEND. 

&&

.AVIATION...VFR CONDITIONS GENERALLY EXPECTED THROUGH SUNDAY 
MORNING. SOME RAIN SHOWERS AND THUNDERSTORMS ARE EXPECTED AGAIN THIS 
AFTERNOON AND EVENING.

&&

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

$$