000
FXUS63 KFSD 250407
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1107 PM CDT FRI MAY 24 2013

.UPDATE...
ISSUED AT 930 PM CDT FRI MAY 24 2013

LATE AFTERNOON CONVECTION ROUND HAS MOVED EAST OF THE AREA WHILE
LEAVING VERY SPOTTY LIGHT SHOWERS FAR EAST. NEXT ROUND THE
DEVELOPED OVER WESTERN AND CENTRAL NE HAS BEEN TURNING MORE EAST
NORTHEAST WITH THE STRONGER CONVECTION AND EXPECT THIS TREND TO
CONTINUE. HOWEVER...FEEL THE SHORT TERM RAP CONTINUES TO BE MORE
IN TUNE WITH THE THREAT OF LIGHT TO MODERATE CONVECTION DEVELOPING
NORTH OF THIS AREA AND AFFECTING ESPECIALLY THE SOUTHERN EDGE OF
THE FORECAST AREA...MORE FAR SOUTHEAST VERY LATE TONIGHT. THE NAM
CONTINUES TO DOWNPLAY THIS THREAT. OVERALL LOW TEMPERATURES LOOK
OK WITH HOURLY READING EXPECTED TO GRADUALLY EVEN OUT...THAT IS
THE TEMPERATURES CONTRAST FROM SOUTH TO NORTH SHOULD DECREASE A
LITTLE.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 332 PM CDT FRI MAY 24 2013

SCATTERED SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE CWA WITH
THE MOST CONCENTRATED AREA NORTH OF INTERSTATE 90 AND EAST OF
INTERSTATE 29 THIS EVENING. WITH THE WAVE THAT IS AIDING IN THIS
DEVELOPMENT MOVING NORTHEAST SUSPECT THE TREND TO THE EAST AND
NORTH WITH THIS ACTIVITY WILL CONTINUE. SHEAR AND INSTABILITY NOT
ENOUGH FOR SEVERE THUNDERSTORMS BUT SOME VERY SMALL HAIL POSSIBLE
WITH THE STRONGER STORMS. BETWEEN ABOUT 3Z TO 6Z THE LOW LEVEL JET
INCREASES QUITE A BIT IN CENTRAL NEBRASKA AND BEGINS TO FOCUS THE
BEST CONVERGENCE/ADVECTION TOWARDS THE MISSOURI RIVER ALONG THE
SOUTH DAKOTA NEBRASKA BORDER. THE WEAKEST CIN AND HIGHEST CAPE
VALUES SUGGEST THAT A PARCEL LIFTED FROM ABOUT 850MB TO 800MB WOULD
HAVE ABOUT 1500 J/KG TO WORK WITH. WHILE THE EFFECTIVE SHEAR IS
QUITE WEAK SOME NICKEL TO DIME SIZED HAIL WOULD BE POSSIBLE NEAR THE
MISSOURI RIVER. WITH FAIRLY SLOW STORM MOTION ANY STORMS THAT COULD
DEVELOP WOULD HAVE THE POTENTIAL TO PRODUCE SOME HEAVIER RAINFALL.
WILL KEEP THE HIGHEST POPS ALONG THE MISSOURI RIVER INTO NORTHWEST
IOWA OVERNIGHT WITH A TREND DOWNWARD IN RAIN AND THUNDERSTORM
POTENTIAL ON SATURDAY. OTHER THAN CONVECTIVE BLOW OFF OR SOMETHING
THAT ADVECTS IN IT LOOKS LIKE CAPPING WILL KEEP THUNDERSTORMS AT BAY
MOST OF THE DAY IN MOST LOCATIONS. STILL EXPECTING QUITE A BIT OF
CLOUD COVER AND COOL TEMPERATURES...RANGING FROM THE MID 60S EAST OF
THE BUFFALO RIDGE TO 75 TO 80 IN SOUTH CENTRAL SOUTH DAKOTA.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 332 PM CDT FRI MAY 24 2013

MODELS SUGGEST THAT A PAIR OF WAVES MAY BEGIN NOSING INTO BLACK
HILLS AREA SATURDAY AFTERNOON AND AGAIN SUNDAY AFTERNOON...
TRIGGERING CONVECTION TO OUR WEST SATURDAY EVENING AND SOUTHWEST ON
SUNDAY EVENING. WITH A QUASI-STATIONARY BOUNDARY DRAPED ACROSS THE
REGION...VERY HIGH PRECIPITABLE WATER AMOUNTS THROUGHOUT THE REGION
AND A STRENGTHENING LOW LEVEL JET NEAR THE MISSOURI RIVER BOTH
NIGHTS...EXPECT SHOWER AND THUNDERSTORM POTENTIAL TO PEAK DURING THE
EVENING AND OVERNIGHT HOURS. MAIN CONCERN WITH THIS CONVECTION WOULD BE
LOCALLY HEAVY RAINFALL AMOUNTS AND STRONG WIND GUSTS. MARGINALLY
SEVERE HAIL WILL ALSO BE POSSIBLE...HOWEVER THIS THREAT WOULD BE
MAINLY DURING THE EVENING HOURS. PRECIPITATION CHANCES DO DIMINISH
SLIGHTLY DURING THE DAY ON SUNDAY...BUT WILL KEEP SCATTERED MENTION
GOING THROUGH THE DAY WITH SOME TIMING UNCERTAINTY.

VERY ACTIVE AND WET PATTERN IS EXPECTED TO PERSIST THROUGH THE
ENTIRE MID AND LONG RANGE WITH PRECIPITATION IN THE FORECAST EACH
PERIOD...INCLUDING MEMORIAL DAY. STILL SEEING QUITE A BIT OF
UNCERTAINTY WITH TIMING ALL OF THE SHORTWAVES TRACKING THROUGH THE
REGION ALONG THE GENERAL UPPER LEVEL SOUTHWEST FLOW. WEST COAST
TROUGHING STARTS NUDGING FURTHER EAST INTO THE HIGH PLAINS LATE WEEK
NEXT WEEK...HOWEVER THE SLOW MOVING NATURE OF THIS SYSTEM KEEPS
IT...AND PRECIPITATION IN THE FORECAST EVEN THROUGH NEXT WEEKEND.
TEMPERATURES WILL WARM A LITTLE TO SLIGHTLY ABOVE NORMAL READINGS
AROUND MID WEEK BUT WILL START TO COOL A BIT LATE WEEK WITH POTENTIAL
TROUGHING ARRIVING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1103 PM CDT FRI MAY 24 2013

MODELS CONTINUE TO SHOW CEILINGS DETERIORATING INTO MVFR-IFR RANGE
LATER TONIGHT AT ALL TAF SITES. STARTING TO SEE HINTS OF MVFR CLOUDS
IN EASTERN NEBRASKA AS OF 04Z...SO WILL CONTINUE THIS DOWNWARD TREND
IN CEILINGS THROUGH THE FIRST 4-6 HOURS OF TAF PERIOD...WITH NEXT
CHANCE OF RAIN EXPANDING INTO SOUTHERN PARTS OF THE AREA ALONG WITH
THE LOWER CEILINGS. SOME MID LEVEL INSTABILITY PRESENT AS THE RAIN
MOVES INTO SOUTHWEST PARTS OF THE FORECAST AREA...BUT PRECIP MOVES
INTO MORE STABLE AIRMASS AS IT PROGRESSES EASTWARD...LEADING TO MORE
ISOLATED THUNDER THREAT ALONG AND EAST OF I-29 CORRIDOR. THUS HAVE
LEFT MENTION OF THUNDER OUT OF KFSD/KSUX TAFS AT THIS TIME...THOUGH
CANNOT COMPLETELY BE RULED OUT 08Z-15Z...ESPECIALLY AT KSUX. BULK OF
MVFR CEILINGS EXPECTED TO BECOME MORE SCATTERED THROUGH THE LATE
MORNING/EARLY AFTERNOON SATURDAY...THOUGH WITH MORE ABUNDANT LOW
LEVEL MOISTURE...POTENTIAL FOR MVFR CUMULUS AT TIMES THROUGH THE
AFTERNOON. GREATER CHANCE OF MVFR-IFR REDEVELOPMENT SATURDAY EVENING
WITH NEXT CHANCE OF CONVECTION SPREADING INTO THE AREA.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&

$$

UPDATE...
SHORT TERM...08
LONG TERM...
AVIATION...