026
FXUS63 KUNR 201132
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
532 AM MDT MON MAY 20 2013
SHORT TERM
TODAY THROUGH TUESDAY NIGHT
ISSUED AT 235 AM MDT MON MAY 20 2013
A CLOSED LOW WITH TWO WEAK SURFACE CENTERS IS WOBBLING
AROUND OVER CENTRAL AND EASTERN SOUTH DAKOTA THIS MORNING...
APPARENTLY NOT IN A HURRY TO MAKE EASTWARD PROGRESS. LIGHT TO
LOCALLY MODERATE RAIN SHOWERS ARE WRAPPING AROUND THE CENTER IN A
LARGE ARC WHICH EXTENDS NORTHWEST INTO NORTH DAKOTA AND THEN CURVES
BACK TO THE SOUTH THROUGH WESTERN SOUTH DAKOTA AND A SLIVER OF
NORTHEAST WYOMING. A STRONG SURFACE PRESSURE GRADIENT HAS SET UP IN
THE CYCLONIC FLOW OVER WESTERN SOUTH DAKOTA PROMPTING A WIND
ADVISORY YESTERDAY EVENING.
TODAY AND TONIGHT...WITH LITTLE MOVEMENT IN THE LOW CENTER...WEATHER
EVENTS WILL BE DRIVEN BY FEATURES ROTATING AROUND THE CENTERS. A
LOW AMPLITUDE TROUGH EXTENDING NORTHWESTWARD FROM THE NORTHERN MOST
LOW CENTER IS CURRENTLY SWEEPING COUNTER CLOCKWISE TOWARD THE
SOUTHWEST AND WILL BE THE FOCUS FOR MORE RAIN TO MOVE THROUGH THE
BLKHLS AND OTHER PARTS OF WESTERN SOUTH DAKOTA TODAY. INSTABILITY
AND SHEAR WILL REMAIN MINIMAL...HOWEVER LONG PERIODS OF CONTINUOUS
RAIN AND SOME UPSLOPE ENHANCEMENT IS EXPECTED TO PRODUCE OVER 2
INCHES OF RAIN IN THE FAVORED AREAS OF THE NORTHERN BLKHLS. ANOTHER
ONE OF THESE RADIAL TROUGHS IS FORECAST TO DO PRETTY MUCH THE SAME
THING THIS EVENING BEFORE THE LOW CENTER SHIFTS EASTWARD EARLY
TUESDAY. AS WELL AS SUPPORTING THE PRECIPITATION WITH LARGE SCALE
ASCENT THESE TROUGHS SERVE TO TIGHTEN THE PRESSURE GRADIENT AND
ENHANCE THE SURFACE WIND SPEEDS.
TUESDAY...BY EARLY TUESDAY MORNING THE LOW CENTER IS FORECAST TO
MOVE OUT OF EASTERN SOUTH DAKOTA AND THE LARGE SPIRAL BAND OF
MOISTURE GOES WITH IT. A GRADUALLY DISSIPATION OF THE CLOUD COVER
AND PRECIPITATION WILL CHARACTERIZE THE DAY AS WELL AS DECREASING
WIND SPEEDS. THE ONLY THING THAT WON'T IMPROVE MUCH IS TEMPERATURES
SINCE LINGERING CLOUD COVER AND CONTINUED COLD ADVECTION IN THE
NORTHLY FLOW WILL KEEP THE SPRING SUN FROM WARMING THE AIRMASS
MUCH.
LONG TERM
WEDNESDAY THROUGH SUNDAY
ISSUED AT 235 AM MDT MON MAY 20 2013
THE STORM SYSTEM WILL CONTINUE TO SLOWLY MOVE EAST OF THE REGION ON
WEDNESDAY...WITH ONLY ISOLATED TO WIDELY SCATTERED SHOWERS
EXPECTED...MAINLY IN THE MORNING OVER NORTHERN AND EASTERN PORTIONS
OF THE CWA. WEAK RIDGING BEHIND THE EXITING SYSTEM WILL BRING MOSTLY
DRY CONDITIONS LATE WEDNESDAY INTO THURSDAY. A SHOWER OR TWO COULD
MAKE IT INTO PORTIONS OF NORTHEASTERN WY FROM THE MTS WEDNESDAY
NIGHT.
A GRADUAL WARMUP IS EXPECTED LATE IN THE WEEK...WITH TEMPERATURES
BACK ABOVE AVERAGE LEVELS BY THE WEEKEND. SOUTHWEST FLOW ALOFT WILL
DEVELOP ACROSS THE REGION BY THE END OF THE WEEK AS AN UPPER LOW
STALLS ACROSS THE PACIFIC NW. SOUTHEASTERLY WINDS AT THE SURFACE
WILL BRING INCREASING LOW LEVEL MOISTURE INTO THE NORTHERN
PLAINS...ESPECIALLY EAST OF THE BLACK HILLS. THIS SETUP SHOULD BRING
DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS TO A GOOD PORTION OF THE
AREA FROM FRIDAY THROUGH THE HOLIDAY WEEKEND. DEPENDING ON THE
TIMING AND STRENGTH OF THE DISTURBANCES PASSING THROUGH THE
AREA...THIS COULD BE AN ACTIVE PERIOD FOR SEVERE WX...ESPECIALLY FOR
THE BLACK HILLS AND EASTWARD ACROSS THE SD PLAINS.
AVIATION
FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING
ISSUED AT 532 AM MDT MON MAY 20 2013
OCCASIONAL RAIN SHOWERS WILL CONTINUE TODAY AND INTO TONIGHT...WITH
MVFR/IFR CONDITIONS GENERALLY PERSISTING ACROSS MOST OF THE AREA.
HOWEVER...VFR CONDITIONS COULD PERSIST AT KRAP THROUGH MUCH OF
TODAY. A MORE STEADY RAIN IS EXPECTED ACROSS THE NORTHERN BLACK
HILLS INTO PORTIONS OF NORTHEASTERN WYOMING AND FAR NORTHWESTERN
SOUTH DAKOTA TODAY. STRONG NORTHWESTERLY WINDS WILL CONTINUE ACROSS
MUCH OF THE PLAINS TODAY...ESPECIALLY THE FAR WESTERN SD PLAINS.
WINDS WILL DIMINISH SOME THIS EVENING...BUT REMAIN GUSTY.
UNR WATCHES/WARNINGS/ADVISORIES
SD...WIND ADVISORY UNTIL 7 PM MDT TUESDAY FOR SDZ001-002-012-013-026-
031-072-073.
WIND ADVISORY UNTIL 7 PM MDT TUESDAY FOR SDZ030-041.
WY...NONE.
SHORT TERM...CARPENTER
LONG TERM...26
AVIATION...26
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page