000
FXUS63 KUNR 121822
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1222 PM MDT SUN MAY 12 2013

.SHORT TERM...TODAY THROUGH MONDAY NIGHT
ISSUED AT 302 AM MDT SUN MAY 12 2013

09Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE ERN DAKOTAS/MN WITH
A WEAK SFC TROUGH EXTENDING FROM NWRN MT THROUGH ERN WY/CO. UPPER
ANALYSIS SHOWS AN UPPER TROUGH OVER THE ERN CONUS WITH A RIDGE
BUILDING OVER THE WEST.

SOUTHERLY RETURN FLOW HAS DEVELOPED OVER THE FORECAST AREA. HOWEVER
DEWPOINTS ARE STILL VERY LOW...IN THE TEENS TO LOWER 30S AND IT
LOOKS LIKE THEY WILL ONLY RISE INTO THE MID TO UPPER 30S THIS
AFTERNOON. ALTHROUGH THE LL MOISTURE WILL REMAIN LOW TODAY...THE
COMBINATION OF DIURNAL HEATING AND LOW LEVEL CONVERGENCE MAY BE
ENOUGH FOR ISOLATED SHOWERS OR THUNDERSTORMS OVER THE BLACK HILLS
THIS AFTN.

THE UPPER RIDGE...AS WELL AS THE LOW-LEVEL THERMAL RIDGE...WILL
BEGIN TO MOVE OVER THE CWA TONIGHT. THE SURFACE TROUGH WILL SHIFT
EAST A LITTLE AND THUS ALLOW FOR WESTERLY BOUNDARY LAYER FLOW TO
KEEP PARTS OF THE BLKHLS AREA RATHER MILD OVERNIGHT...THUS SETTING
THE STAGE FOR A WARM MONDAY.

HIGH TEMPERATURES ARE EXPECTED TO REACH THE LOWER 90S AT MANY
LOCATIONS ON MONDAY. DUE TO SYNOPTIC SCALE SUBSIDENCE UNDER THE
UPPER RIDGE AND VERY DRY AIR IN PLACE ONCE AGAIN WILL INCLUDE ONLY
A SLIGHT CHANCE OF AFTN THUNDERSTORMS OVER THE BLACK HILLS.

&&

.LONG TERM...TUESDAY THROUGH SATURDAY
ISSUED AT 302 AM MDT SUN MAY 12 2013

UPPER LEVEL RIDGE BREAKS DOWN ON TUESDAY AS A STRONG SURFACE LOW
PASSES TO THE NORTH...AND A STRONG COLD FRONT DROPS THROUGH THE
DAKOTAS. NORTHWEST WINDS OF 25+ MPH CAN BE EXPECTED ACROSS THE SOUTH
DAKOTA PLAINS TUESDAY AFTERNOON AND EARLY EVENING. MORE SEASONABLE
TEMPS ARE EXPECTED FOR THE REMAINDER OF THE WEEK AS AREA REMAINS
UNDER ZONAL FLOW. WEAK DISTURBANCES WITHIN THIS FLOW WILL BRING
CHANCES FOR MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
FROM MID WEEK ONWARD. A MORE POTENT SYSTEM MAY CROSS THE NORTHERN
PLAINS LATE IN THE WEEK AND INTO THE WEEKEND...BRINGING THE
POSSIBILITY OF MORE WIDESPREAD MOISTURE.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON
ISSUED AT 1222 PM MDT SUN MAY 12 2013

VFR CONDITIONS ARE GENERALLY EXPECTED THROUGH MONDAY MORNING. AN
ISOLATED AFTERNOON THUNDERSTORM IS POSSIBLE ACROSS THE BLACK HILLS.

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

$$

SHORT TERM...10
LONG TERM...15
AVIATION...26