496 
FXUS63 KFSD 172332
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
632 PM CDT MON JUL 16 2012

.DISCUSSION.../ISSUED AT 407 PM CDT/
A HOT AND HUMID DAY CURRENTLY UNDERWAY WITH TEMPERATURES WELL INTO 
THE 90S AND DEWPOINTS IN THE 60S. FRONTAL BOUNDARY CURRENTLY 
SITUATED AROUND HIGHWAY 14...SHOULD SLOWLY MOVE SOUTH THIS EVENING. 
ATMOSPHERE REMAINS CAPPED OVER THE AREA...DESPITE MLCAPE OVER 3500 
J/KG NORTH OF THE BOUNDARY. INTERESTINGLY...CU HAS FORMED FURTHER 
SOUTHWEST ACROSS NEBRASKA AND NEAR THE MISSOURI RIVER. IT SEEMS 
LIKELY THE ATMOSPHERE HAS MIXED ALL THE WAY THROUGH THE CAP IN THESE 
AREAS. THIS IS EVIDENT BY THE LOWER DEWPOINTS IN THE 40S AND 50S IN 
THESE AREAS. SO WHILE THIS MIXING HAS ERODED THE CAP...IT HAS ALSO 
ERODED MUCH OF THE INSTABILITY...HENCE THE LACK OF OF SIGNIFICANT 
UPGROWTH. EXPECT THIS TO CONTINUE TO BE THE CASE THROUGH THE EVENING 
WITH ONLY AN ISOLATED SHOWER OR THUNDERSTORM WITH THAT CU. SEEMS 
MORE PROBABLE THAT CONVECTION DEVELOPS WEST OF OUR CWA ALONG THE 
OTHER BOUNDARY. THESE STORMS SHOULD PROPAGATE TOWARDS OUR WESTERN 
CWA THIS EVENING...POSSIBLY IMPACTING LOCATIONS WEST OF THE JAMES 
RIVER. WILL ALSO HAVE TO MONITOR DEVELOPMENT ALONG THE BACKDOOR 
BOUNDARY AS IT DROPS SOUTH THROUGH THE CWA. HRRR AND NAM SEEM TO BE 
OVERDOING CONVECTION CHANCES WITH THIS BOUNDARY...BUT CANT RULE OUT 
A FEW STORMS WITH ABUNDANT LOW LEVEL MOISTURE POOLING AROUND THE 
BOUNDARY.

UPPER LEVEL FORCING AND DEEPER MOISTURE SHOULD MOVE ACROSS THE CWA 
AFTER MIDNIGHT TONIGHT.  SO EVEN IF NO SURFACE CONVECTION GETS GOING 
THIS EVENING...SHOULD HAVE A CHANCE OF ELEVATED STORMS LATER TONIGHT 
NORTH OF THE BOUNDARY IN AREA OF LOW LEVEL THETAE ADVECTION. THIS 
CONVECTION WILL LIKELY STAY GENERALLY FROM HIGHWAY 34 AND POINTS 
NORTH...WITH THE ECMWF ACTUALLY KEEPING IT NORTH OF THE CWA...SO DID 
NOT GO ANY HIGHER THAT 30 TO 40 POPS. LOWS TONIGHT WILL STAY 
MILD...GENERALLY LOW TO MID 70S.

WEDNESDAY WILL BE ANOTHER HOT ONE ACROSS MUCH OF THE REGION...WITH 
HIGHS IN THE 90S EVERYWHERE BUT SOUTHWEST MINNESOTA. DEWPOINTS WILL 
LIKELY BE HIGHER THAN TODAY...ESPECIALLY ALONG AND EAST OF 
INTERSTATE 29...WHERE VALUES IN THE LOW 70S ARE LIKELY. THIS WILL 
MAKE FOR ANOTHER DAY OF VERY HIGH HEAT INDICES...SO WENT AHEAD AND 
ISSUED A HEAT ADVISORY FOR AREAS MOST LIKELY TO HAVE A HEAT INDEX 
OVER 100. THE ABOVE MENTIONED WAVE WILL CONTINUE TO PUSH EAST 
WEDNESDAY. BY THIS TIME BEST CHANCE OF CONVECTION SHOULD BE 
GENERALLY EAST OF INTERSTATE 29. AREAS TO THE WEST WILL BE UNDER AN 
AREA OF LARGE SCALE SUBSIDENCE AND SHOULD REMAIN CAPPED. INITIAL 
CONVECTION SHOULD EB ELEVATED...BUT IF THE WAVE MOVES SLOW ENOUGH WE 
SHOULD SEE A TRANSITION TO SURFACE BASED CONVECTION BY AFTERNOON. IF 
THIS HAPPENS...WOULD BE MOST LIKELY OVER SOUTHWEST MINNESOTA AND 
PORTIONS OF NORTHWEST IOWA. COULD SEE A COUPLE SEVERE STORMS DURING 
THE AFTERNOON...WITH A BIT BETTER SHEAR EXPECTED. /CHENARD

ANY CONVECTION THAT DEVELOPS ON WEDNESDAY AFTERNOON MAY LINGER INTO 
THE EVENING ACROSS NW IOWA AND SW MN. MODELS DO SHOW A SECOND WEAK 
WAVE MOVING SOUTHEAST ACROSS MINNESOTA ON WEDNESDAY NIGHT. THIS MAY 
RESULT IN MORE STORMS DEVELOPING INTO SOUTHWEST MINNESOTA AFTER 
SUNSET. AGAIN...ANY STORM DEVELOPMENT WILL BE SOMEWHAT ISOLATED. ANY 
STORMS SHOULD MOVE EAST BY DAWN ON THURSDAY. OTHERWISE...EASTERLY 
FLOW IS EXPECTED ACROSS THE AREA THROUGH THE EVENING. THIS WILL 
BRING A BIT COOLER AIR INTO THE AREA...ALLOWING LOWS TO DROP BELOW 
70 DEGREES IN SW MN ANAD BETWEEN 70 AND 75 DEGREES ELSEWHERE.

THE UPPER LEVEL RIDGE WILL BUILD ACROSS THE AREA THURSDAY AND 
FRIDAY. AS HEIGHTS RISE AT 500 MB...THE SURFACE RIDGE WILL 
STRENGTHEN OVER THE GREAT LAKES.  THIS WILL KEEP WINDS OUT OF THE 
EAST DURING THE DAY. HOWEVER...MOSTLY SUNNY SKIES ARE EXPECTED AND 
THE AIR MASS REMAINS VERY WARM. TEMPERATURES ARE EXPECTED TO BE 
SIMILAR TO WEDNESDAY FROM AROUND 90 IN SOUTHWEST MINNESOTA TO AROUND 
100 IN SOUTH CENTRAL SD. CLEAR SKIES AND RELTIAVELY LIGHT WINDS ARE 
AGAIN EXPECTED THURSDAY NIGHT. LOWS WILL BE SIMLAR TO WEDNESDAY 
NIGHT FROM THE UPPER 60S IN SOUTHWEST MINNESOTA TO 70 TO 75 
ELSEWHERE.

THE REMAINDER OF THE FORECAST WILL REALLY FOCUS ON THE RETURN OF THE 
HEAT. OVERALL...THE GFS AND ECMWF ARE VERY SIMILAR ON THE STRENGTH 
AND DURATION OF THIS RIDGE. BY EARLY NEXT WEEK THEY BOTH HAVE A 
FAIRLY STRONG WAVE MOVE ALONG THE CANADIAN BORDER. THEY ALSO SHOW 
THE RIDGE VERY SLOWLY BREAKING DOWN BY TUESDAY OR WEDNESDAY ALTHOUGH 
OVERALL THE RIDGE REMAINS OVER THE CENTRAL UNITED STATES THROUGH THE 
MIDDLE NEXT WEEK SO NO SIGNIFICANT BREAK IN THE HEAT IS REALLY 
EXPECTED FOR THE NEXT 7 DAYS. IN TERMS OF PRECIPITATION...BOTH 
MODELS SHOW A WEAK SYSTEM MOVING ACROSS THE DAKOTAS ON SUNDAY BUT IT 
REMAINS VERY WARM ALOFT OVER SOUTHERN SOUTH DAKOTA AND THE LARGE 
SCALE FORCING FOR ASCENT REMAIN CLOSER TO THE CANADIAN BORDER. SO 
WHILE WE HAVE KEPT A 20 TO 30 PERCENT CHANCE OF PRECIPATION FOR 
SUNDAY AND SUNDAY NIGHT...THE CONVECTION DOES NOT LOOK TO BE 
WIDESPREAD AT THIS POINT AND MOST AREAS WILL LIKELY NOT SEE ANY RAIN 
FROM THIS SYSTEM. GOING INTO NEXT WEEK...THERE DOES NOT APPEAR TO BE 
ANY REAL CHANCE OF WIDESPREAD RAINFALL INTO THE MIDDLE OF NEXT 
WEEK.

LOOKING AT DAY TO DAY...FRIDAY WILL SEE THE HEAT SPREAD INTO THE 
JAMES VALLEY WITH HIGHS AROUND 100. TO THE EAST HIGHS WILL RANGE 
FROM THE LOWER 90S AROUND HIGHWAY 71 IN MINNESOTA AND IOWA...TO THE 
MID TO UPPER 90S IN THE REMAINDER OF SOUTHEAST SOUTH DAKOTA. AFTER 
FRIDAY...LOWS SATURDAY MORNING THROUGH TUESDAY MORNING WILL BE IN 
THE LOWER TO MID 70S.  HIGHS ON SATURDAY AND SUNDAY WILL BE SIMILAR 
TO FRIDAY GENERALLY IN THE LOWER 90S IN SOUTHEAST MINNESOTA TO AT OR 
ABOVE 100 WEST OF THE JAMES RIVER. IF THERE ARE LESS CLOUDS OR THE 
SURFACE HIGH RETREATS MORE QUICKLY...TEMPERATURES BOTH DAYS COULD BE 
2 TO 5 DEGREES WARMER...RESULTING IN HIGHS APPROACHING 100 OVER MUCH 
OF THE AREA.  A WEAK BOUNDARY WILL GO THROUGH SUNDAY EVENING AND 
THIS MAY BRING A BIT COOLER AIR INTO THE AREA. HOWEVER...HOW COOL 
THE AIR WILL BE AND HOW LONG IT REMAINS IS VERY UNCERTAIN AT THIS 
POINT. FOR NOW...FORECAST HIGHS ONLY 3 TO 5 DEGREES COOLER THAN THE 
WEEKEND WHICH MEANS 90S LOOK TO PERSIST THROUGH TUESDAY. IF THE 
FRONT RETREATS BACK TO THE NORTH MORE QUICKLY...PER THE 12Z 
ECMWF...HIGHS COULD BE BACK OVER 100 DEGREES IN PARTS OF THE AREA BY 
TUESDAY./SCHUMACHER

&&

.AVIATION.../FOR THE 00Z TAF ISSUANCE/
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH 00Z THURSDAY. FRONT 
SLOWLY PROGRESSING SOUTH ACROSS THE CWA AT THIS TIME. ISOLATED 
SURFACE BASED CONVECTION DEVELOPING ACROSS THE AREA...BUT CONFIDENCE 
IN IT REACHING ANY OF THE PARTICULAR AIRPORTS LOW ENOUGH THAT IT WAS 
LEFT OUT OF THE FORECAST. THERE IS SOME ELEVATED CONVERGENCE TONIGHT 
WITH THE I-90 CORRIDOR LOCATED ON THE NOSE OF THE LOW LEVEL JET. 
POTENTIAL FOR STORMS TO AFFECT I-90 AND HIGHWAY 14 CORRIDOR BUT 
AGAIN CONFIDENCE IS TOO LOW TO INCLUDE IN THE FORECAST. SMALL CHANCE 
A FEW OF THESE STORMS FORM FURTHER SOUTH WEDNESDAY MORNING AND EARLY 
AFTERNOON CLOSER TO KFSD AND KSUX...BUT PROBABILITY AND TIMING 
CONFIDENCE TOO LOW TO INCLUDE IN TAF.  MODEL SOUNDINGS ARE QUICK TO 
GO CONVECTIVE...BUT APPEAR TO BE TOO QUICK TO BREAK DOWN THE 
ELEVATED INVERSION ALOFT.  IF CONVECTION WAS ABLE TO DEVELOP BEST 
CHANCES WOULD BE IN THE 17-21Z TIMEFRAME FOR INITIATION. 


&& 

.FSD WATCHES/WARNINGS/ADVISORIES...

SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&

$$