National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KFSD 150156
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
856 PM CDT FRI JUN 14 2013

.UPDATE...
ISSUED AT 855 PM CDT FRI JUN 14 2013

THREAT FOR TORNADOES HAVE WANED ACROSS THE AREA AS OUTFLOW
BOUNDARY HAS STABILIZED THE NEAR SURFACE ENVIRONMENT IN THE
VICINITY OF SIOUX CITY. HOWEVER...AS WEAK UPPER WAVE MOVES INTO NW
IA...ELEVATED THUNDERSTORMS HAVE DEVELOPED IN NW IA. 00Z RAP SHOWS
THAT THERE IS 2000 TO 3000 J/KG OF MUCAPE AVAILABLE TO WORK WITH
BUT THE EFFECTIVE SHEAR IS AROUND 30 KTS AND DROPS THROUGH THE
EVENING. SO AT THIS POINT...DO NOT EXPECT ELEVATED SUPERCELLS BUT
AN ISOLATED MULTICELL STORM COULD PRODUCE QUARTER TO HALF DOLLAR
SIZE HAIL THROUGH MIDNIGHT IN NORTHWEST IOWA. HAVE RAISED POPS TO
50 TO 70 PERCENT WITH THIS ACTIVITY. LATER TONIGHT...NAM AND RAP
BOTH SUGGEST THAT CONVERGENCE ALONG THE 850 MB FRONT WILL RESULT
IN MORE CONVECTIVE DEVELOPMENT FROM CENTRAL NEBRASKA INTO NORTHWEST
IOWA. AM A LITTLE CONCERNED THAT ONGOING CONVECTION OVER ERN
NEBRASKA MAY RESULT IN THIS CONVECTION FOCUSING A BIT FARTHER
SOUTH AS 850 MB JET INTERACTS WITH REINFORCED OUTFLOW BOUNDARY.
BUT ENOUGH UNCERTAINTY AT THIS POINT THAT WILL CONTINUE 50 POPS IN
NW IA AND NE NEBRASKA LATE TONIGHT. WITH CLOUDS AND AMPLE MOISTURE
OVER THE MUCH OF THE AREA...LOWS SHOULD REMAIN IN THE 60S. THE
ONLY EXCEPTION MAY BE TOWARD 9V9 AND HON. WITH KPIR AND KMBG DEW
POINTS IN THE MID 50S...NORTHERLY FLOW SHOULD BRING SOME OF THIS
DRY AIR INTO PORTIONS OF CENTRAL SD SO WILL DROP LOWS A COUPLE OF
DEGREES INTO THE UPPER 50S.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 325 PM CDT FRI JUN 14 2013

SEVERE THUNDERSTORM THREAT STILL EXISTS OVER THE AREA LATE THIS
AFTERNOON AND EVENING. CONVERGENCE IS STRENGTHENING AT/NEAR THE
SURFACE OVER NORTHEAST NEBRASKA AND THIS CONVERGENCE COUPLED WITH A
BOUNDARY THAT EXTENDS SOUTH OF THERE SHOULD PROVIDE A FOCUS FOR
THUNDERSTORM DEVELOPMENT. VIRTUALLY ALL OF THE MODELS...INCLUDING
THE HIGH RESOLUTION MODELS SUGGEST THIS AREA FOR DEVELOPMENT AND
ONLY DIFFER ON HOW FAR NORTH THE STRONG UPDRAFTS WILL BE. SUSPECT
THAT DEVELOPMENT WILL OCCUR IN NORTHWEST KANSAS TO CENTRAL NEBRASKA
THEN WORK NORTHEAST. WHILE CAPPING WILL NEED TO BE OVERCOME...LIKELY
NEEDING HIGH TEMPERATURES CLOSE TO 95 DEGREES...IF ANYTHING COULD
DEVELOP IT SHOULD QUICKLY BECOME SEVERE. MODELS STILL HINTING AT
SURFACE BASED CAPE VALUES OF 3000 TO 3500 J/KG WITH DEEP LAYER SHEAR
OF ABOUT 30 TO 35 KNOTS. THE SURFACE TO 1 KM SHEAR ALSO SUGGESTED TO
BE AROUND 20 KNOTS SO A TORNADO WOULD BE POSSIBLE. AT THIS TIME
DAKOTA AND DIXON COUNTIES APPEAR TO HAVE THE HIGHEST THREAT FOR
TORNADOES IN THE SIOUX FALLS CWA. THERE HAVE BEEN SOME HINTS THAT
SOME SHOWERS AND THUNDERSTORMS COULD DEVELOP OVER THE FAR WESTERN
CWA AS THE UPPER LEVEL SUPPORTS SWINGS INTO THE AREA BUT WILL NOT
INCLUDE ANY CHANCES YET AS CONFIDENCE IN THAT IS TOO LOW.

THE CHANCE FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE IN THE FAR
SOUTHERN CWA ON SATURDAY AS THE UPPER LEVEL WAVE MOVES THROUGH.
INSTABILITY AND SHEAR MUCH WEAKER ON SATURDAY SO MORE GENERAL
CHANCES WITH NO SEVERE THUNDERSTORMS EXPECTED.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 325 PM CDT FRI JUN 14 2013

PRECIP CHANCES ACROSS NORTHWEST IOWA APPEAR TO WANE FAIRLY RAPIDLY
SATURDAY EVENING WITH SURFACE BOUNDARY AND CONVECTION EXPECTED TO
FOCUS ALONG AND SOUTH OF I-80.  SURFACE RIDGE NOSES INTO THE
REGION...RESULTING IN GOOD RADIATIVE CONDITIONS.

SURFACE RIDGE BEGINS TO DRIFT TO THE SOUTH AND EAST ON SUNDAY WITH
INSTABILITY ALOFT STARTING TO CREEP INTO SOUTH CENTRAL SOUTH
DAKOTA.  INSTABILITY APPEARS TO BE FAIRLY CAPPED WITH WARM LAYER
NEAR 700 MB.  WHILE ELEVATED INSTABILITY CREEPS NORTHWARD THROUGHOUT
THE DAY...CAP ONLY WEAKENS SUBSTANTIALLY ENOUGH ALONG THE MISSOURI
RIVER VALLEY WITH LACK OF STRONG UPPER LEVEL SUPPORT.  MAY GET A
LITTLE SUPPORT FROM RIGHT REAR QUADRANT OF STRENGTHENING JET
STREAK...BUT STILL MAY BE DIFFICULT TO OVER COME 60-100 J/KG OF
ELEVATED CIN.  AS SUCH...LEFT SLIGHT CHANCE/LOW CHANCE POPS
THROUGHOUT THE DAY BUT AM EXPECTING THE FOCUS TO BE SOUTH OF THE
FORECAST AREA.

AS COLD FRONT WORKS THROUGH THE AREA SUNDAY NIGHT HAVE SLIGHT
CHANCE/LOW END CHANCE POPS MAINLY ACROSS NORTHWEST IOWA AND ADJACENT
AREAS. STILL NOT A TON OF INSTABILITY TO WORK WITH...SO IF ANYTHING
DEVELOPS EXPECTING MAINLY GENERAL THUNDERSTORMS WITH JUST AN
ISOLATED THREAT OF SEVERE WEATHER AT BEST.

SURFACE RIDGE BUILDS BACK INTO THE AREA MONDAY INTO TUESDAY CREATING
RELATIVELY QUIET BENIGN WEATHER FOR MID JUNE.  WINDS APPEAR TO BE
FAIRLY LIGHT WITH DEW POINTS IN THE MID AND UPPER 50S.

THEREAFTER...A SERIES OF SHORTWAVES MOVE ACROSS THE NORTHERN PLAINS
WEDNESDAY AND BEYOND ORIGINATING FROM THE UPPER LOW OVER THE PACIFIC
NORTHWEST.  TIMING OF THE WAVES IS DIFFICULT THAT FAR OUT...SO LEFT
POPS SIMILAR TO GUIDANCE WITH FOCUS MORE TOWARDS THE END OF THE
PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 553 PM CDT FRI JUN 14 2013

VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS MOST OF SOUTHEAST
SOUTH DAKOTA AND SOUTHWEST MINNESOTA THIS EVENING. THE EXCEPTIONS
ARE AREAS ACROSS AND NEAR NORTHWEST IOWA AND NORTHEAST
NEBRASKA...WHERE A COUPLE OF INTERSECTING FRONTS WILL BE THE FOCUS
FOR STRONG TO SEVERE THUNDERSTORMS. THE NORTHWARD EXTENT OF THE
THUNDERSTORM COVERAGE IS NOT ENTIRELY CERTAIN AND HAVE INTRODUCED
VCTS TO THE KFSD TAF ACCORDINGLY. THE KSUX TAF SITE COULD SEE SOME
SEVERE THUNDERSTORM ACTIVITY THIS EVENING WITH STRONG
LLWS/GUSTS...ESPECIALLY THROUGH 04/05Z. A FRONT WILL STALL ACROSS
NORTHWEST IOWA TONIGHT...MAKING ADDITIONAL TSRA DEVELOPMENT
POSSIBLE AT KSUX SATURDAY MORNING. THE FRONT SHOULD PUSH SOUTHEAST
OF THE AREA DURING THE LATE AFTERNOON.


&&

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

$$

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