000
FXUS63 KFSD 141535
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1035 AM CDT FRI JUN 14 2013

.UPDATE...
ISSUED AT 1026 AM CDT FRI JUN 14 2013

NO BIG CHANGES TO THE FORECAST AT THIS TIME. WATCHING SOME
ELEVATED SHOWERS AND VERY ISOLATED THUNDERSTORMS WHICH APPEAR TO
BE DEVELOPING AROUND 8000 KFT. LIFTING A PARCEL FROM THIS LEVEL
PRODUCES A CAPE OF ABOUT 500-800 J/KG SO FOR NOW NOT PLANNING ON
ANY OF THIS WARM AIR ADVECTED CONVECTION TO PRODUCE MUCH MORE THAN
BRIEF HEAVY DOWNPOURS AS IT PROGRESSES EASTWARD. THE THREAT FOR
SEVERE THUNDERSTORMS WILL CONTINUE LATE THIS AFTERNOON AND EVENING
WITH THE BEST CHANCE FROM NORTHEAST NEBRASKA INTO NORTHWEST IOWA
FROM ABOUT 23Z THROUGH 5Z. IF TEMPERATURES IN CENTRAL NEBRASKA CAN
CLIMB TO ABOUT 90 OR SO THERE IS A DECENT CHANCE THAT THE CAP WILL
BREAK. IF THAT DOES HAPPEN UPSTREAM INSTABILITY IN THE FORM OF
MIXED LAYER CAPE VALUES OF 3000 J/KG AND 0 TO 6 KM BULK SHEAR
VALUES OF ABOUT 35 TO 40 KNOTS SUPPORT THE THREAT FOR ROTATING
SUPERCELLS AND LARGE HAIL. THE 0 TO 1 KM BULK SHEAR WILL ALSO BE
PUSHING ABOUT 20 KNOTS WHICH WITH THE EXTREME INSTABILITY WILL
CARRY A THREAT FOR TORNADOES. ADDITIONAL DEVELOPMENT WILL BE
POSSIBLE THROUGH THE NIGHT BUT THE STRONGEST ACTIVITY SHOULD BE
BEFORE ABOUT 5Z.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 444 AM CDT FRI JUN 14 2013

SEEING CONVECTION CONTINUING TO DEVELOP ACROSS PORTIONS OF
SOUTHWESTERN MINNESOTA INTO THE IOWA GREAT LAKES REGION EARLY THIS
MORNING IN ASSOCIATION WITH A WEAK MIDLEVEL BOUNDARY IN PLACE OVER
THAT AREA. ANTICIPATE THIS TO PULL OFF TO THE EAST THROUGH THE EARLY
MORNING HOURS. OTHERWISE...EXPECT CONVECTION TO DEVELOP ACROSS THE
EASTERN PORTIONS OF THE CWA AFTER SUNRISE WITH INCREASING THETA E
ADVECTION AS A STRENGTHENING LOW LEVEL JET DEVELOPS THROUGH NEBRASKA
INTO THE LOWER MISSOURI RIVER CORRIDOR THROUGH THE MORNING HOURS.
WHILE THEIR IS PLENTY OF ELEVATED INSTABILITY...SHEAR IS NOT OVERLY
IMPRESSIVE AT AROUND 20 KTS SO WOULD BE LOOKING AT MULTICELLULAR
DEVELOPMENT...AND COULD NOT RULE OUT MARGINALLY SEVERE HAIL WITH
THESE STORMS. WITH A STRENGTHENING CAP ACROSS THE AREA THROUGH THE
DAY...THINK THAT SURFACE BASED CONVECTION IS GOING TO BE HARD TO
COME BY WITH MODELS NOT WEAKENING THE CAP UNTIL VERY LATE TODAY AS A
SHORTWAVE TRACKS INTO THE REGION AND TEMPERATURES COOL ALOFT. WHILE
THE STRONGER INSTABILITY AND SHEAR WILL BE SITUATED THROUGH THE
WESTERN PORTIONS OF OUR CWA IN THE AFTERNOON...THE CAP WILL BE
STRONGEST OVER THIS AREA IN THE PREFRONTAL ENVIRONMENT AHEAD OF THE
SURFACE BOUNDARY WHICH WILL APPROACH OUR FAR WEST LATE IN THE DAY.
IF BY SOME CHANCE THE CAP WOULD BREAK...THEN SEVERE STORMS WOULD
ALMOST BE A CERTAINTY WITH MUCAPE VALUES JUST OVER 2000 J/KG AND
EFFECTIVE SHEAR AROUND 40 KTS. THE BETTER LOW/MID LEVEL FORCING WILL
REMAIN OVER OUR EAST DURING THE DAY...SO WILL KEEP BETTER CHANCE OF
CONVECTION OVER THAT AREA. AS FOR HIGHS...TEMPERATURES WILL BE
WARMEST IN OUR WEST WHERE THERE STANDS A BETTER POSSIBILITY OF
GETTING SOME BREAKS IN THE CLOUDS...WITH HIGHS TOPPING OUT IN THE
LOWER TO MID 80S. TO THE EAST...WHERE CONVECTION/CLOUD COVER WILL
RESIDE...HIGHS WILL REMAIN IN THE UPPER 70S.

BY TONIGHT...A SURFACE LOW WILL BE SITUATED THROUGH EAST CENTRAL
NEBRASKA WITH A WARM FRONT EXTENDING EASTWARD FROM THE LOW. THESE
FEATURES WILL LIFT TO THE NORTHEAST DURING THE NIGHT...AS A
SECONDARY SHORTWAVE LIFTS OUT OF NEBRASKA. THIS WILL KEEP A GOOD
CHANCE OF CONVECTION GOING THROUGH OUR SOUTHEASTERN ZONES DURING THE
OVERNIGHT HOURS WITH CONTINUING THETA E ADVECTION/ISENTROPIC LIFT
REMAINING OVER THAT AREA. THERE WILL STILL BE PLENTY ELEVATED
INSTABILITY AND SHEAR...SO AGAIN COULD HAVE A FEW SEVERE STORMS WITH
LARGE HAIL/DAMAGING WIND. WITH THE POTENTIAL FOR A FEW ROUNDS OF
CONVECTION GOING OVER THE SAME AREA DURING THE NIGHT...MAY HAVE TO
KEEP AN EYE ON THE FLOODING POTENTIAL OVER THAT AREA. LOWS LOOK TO
RANGE FROM NEAR 60 IN THE NORTH AND FAR WEST...TO THE MID 60S
THROUGH THE LOWER MISSOURI RIVER CORRIDOR INTO NORTHWESTERN IOWA.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 444 AM CDT FRI JUN 14 2013

850MB FRONT LINGERS OVER SOUTHEAST PORTION OF THE CWA INTO SATURDAY
MORNING...THOUGH EXACT PLACEMENT SOMEWHAT UNCERTAIN AND DEPENDENT ON
WHAT HAPPENS WITH OVERNIGHT CONVECTION. GENERAL MODEL CONSENSUS DOES
SHOW ANOTHER WEAK MID LEVEL WAVE SLIDING EAST-NORTHEAST ALONG THIS
BOUNDARY THROUGH THE MORNING WHICH WOULD CONTINUE THREAT OF STORMS
WITH LOCALLY HEAVY RAIN AS GFS/NAM BOTH SHOWING PRECIPITABLE WATER
VALUES OF 1.5-1.8 INCHES IN THE AREA SATURDAY MORNING. WILL HANG
ONTO HIGH POPS IN AREAS MAINLY SOUTH OF A VERMILLION SD TO SPENCER
IA LINE THROUGH 18Z...THOUGH AGAIN THIS COULD SHIFT IF THE BOUNDARY
HANGS UP A LITTLE FARTHER NORTH OR SOUTH. PRECIP CHANCES SHOULD
DIMINISH IN THE AFTERNOON AFTER THE WAVE PASSES BY. NAM PUSHES THE
BOUNDARY FARTHEST SOUTH AWAY FROM OUR CWA THROUGH THE AFTERNOON...
ALLOWING DRIER AIR TO PUSH SOUTHWARD THROUGH OUR FORECAST AREA. GFS
AND ECMWF CONTINUE TO HOLD LOW LEVEL BOUNDARY CLOSER TO KSUX/KSLB
THOUGH. WITH CONTINUED INSTABILITY AND BROAD LIFT IN RIGHT ENTRANCE
REGION OF DEPARTING JET STREAK OVER NORTHERN MINNESOTA...CANNOT CUT
POPS OUT OF THE AFTERNOON COMPLETELY...BUT WILL TAPER INTO CHANCE
RANGE WITH PARTIAL CLEARING THROUGH THE AFTERNOON. NORTHWEST IOWA
LIKELY TO SEE COOLER TEMPERATURES THAN AREAS FARTHER NORTHWEST IN THE
AREA WHERE SUNSHINE WILL BE MORE PREVALENT. IF RAIN/CLOUDS PERSIST
LONGER INTO THE AFTERNOON...GOING HIGHS MAY STILL BE A LITTLE TOO
WARM...BUT WILL HEDGE TOWARD OPTIMISTIC SIDE FOR NOW.

SATURDAY NIGHT SHOULD BE MOSTLY DRY...WITH JUST A SMALL CHANCE OF
LINGERING STORMS IN OUR FAR SOUTHEAST IN THE EVENING. SUNDAY REMAINS
RATHER MUDDLED AND UNCERTAIN...AS OUR AREA IS SITUATED BETWEEN MAIN
UPPER TROUGH DROPPING SOUTHWARD INTO THE UPPER MIDWEST OUT OF CANADA
AND A TRAIN OF SMALL-SCALE WAVES TRACKING EAST OUT OF THE CENTRAL
ROCKIES. SEEING VERY LITTLE CONSENSUS IN POSITIONING/TIMING OF THE
LATTER...RESULTING IN LOW CONFIDENCE PRECIPITATION FORECAST FOR
SUNDAY/SUNDAY NIGHT. ALL MODELS SEEM TO DEVELOP SOME SORT OF COMPLEX
OVER THE HIGH PLAINS OF SOUTHWEST SD/WESTERN NEBRASKA SUNDAY MORNING
BUT WHAT HAPPENS AFTER THAT IS WHERE GREATEST QUESTIONS LIE. ECMWF
AND NAM GENERALLY TRACK THIS SYSTEM SOUTHEASTWARD INTO NEBRASKA...
POSSIBLY SCRAPING THROUGH THE SOUTHERN PORTIONS OF OUR CWA SUNDAY
AFTERNOON BEFORE PULLING AWAY. GFS/GEM ON THE OTHER HAND...GROW THE
COMPLEX UPSCALE THROUGH THE DAY...POSSIBLY IN RESPONSE TO NORTHERN
STREAM TROUGH DROPPING SOUTH ALONG WITH GENERAL CONVECTIVE FEEDBACK
IN THE MODEL...AND PRODUCE MUCH MORE WIDESPREAD PRECIPITATION IN OUR
AREA SUNDAY AFTERNOON/SUNDAY NIGHT. WITH UNCERTAINTY...GENERALLY
SPLIT THE DIFFERENCE AT THIS POINT AND WILL CARRY LOW-MID RANGE
CHANCE POPS IN OUR SOUTHWEST SUNDAY AFTERNOON...AND GENERALLY
ALONG/SOUTH OF I-90 SUNDAY NIGHT. HOWEVER...PLENTY OF ROOM FOR
ADJUSTMENTS IN THIS PERIOD AS MODELS HOPEFULLY COME AROUND TO ONE
PREFERRED SOLUTION. DAY 3 SEVERE OUTLOOK INCLUDES OUR SOUTHWEST
FORECAST AREA IN SLIGHT RISK AREA...BUT WITH AFOREMENTIONED LOW
CONFIDENCE IN STORM EVOLUTION THROUGH THIS PERIOD...OPTED TO LEAVE
ANY MENTION OF SEVERE THREAT OUT OF THE HWO AT THIS TIME.

IF WE DO SEE ANY STORMS SUNDAY/SUNDAY NIGHT...NORTHERN STREAM WAVE
SHOULD CLEAR THEM OUT BY MONDAY MORNING...LEAVING GENERALLY DRY AND
COOLER WEATHER FOR THE BEGINNING OF NEXT WEEK. WARMER AIR BUILDS BACK
IN BY MIDWEEK AS UPPER RIDGE SHIFTS EAST ACROSS THE PLAINS. MODELS
SHOW A SMATTERING OF LIGHT PRECIP IN WARM ADVECTION ACROSS THE AREA
WEDNESDAY...BUT LOW CONFIDENCE IN AVAILABLE MOISTURE SO WILL LEAVE
THE AREA MOSTLY DRY FOR WEDNESDAY...WITH A LOW CHANCES FOR STORMS
WEDNESDAY NIGHT/THURSDAY AS THE UPPER RIDGE AXIS SHIFTS EAST AND
WEAK WAVE COULD SLIDE INTO THE AREA IN RESULTING SOUTHWEST FLOW
ALOFT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 616 AM CDT FRI JUN 14 2013

SCATTERED THUUNDERSTORMS WILL DEVELOP ACROSS MAINLY THE EASTERN
PORTIONS OF THE AREA TODAY...THOUGH CONFIDENCE ON TIMING IS LOW.
THE BETTER CHANCES WILL REMAIN EAST OF SIOUX FALLS...THOUGH CANNOT
RULE OUT A PERIOD OF THUNDERSTORM ACTIVITY ANYTIME TODAY AROUND
KFSD...WITH BRIEF REDUCED VISIBILITIES IN A HEAVIER STORM.
NORTHWESTERN IOWA AND SOUTHWESTERN MINNESOTA WILL HAVE A BETTER
CHANCE...ESPECIALLY THIS AFTERNOON AND EVENING. AS WINDS DIE OFF
TONIGHT AT KFSD AND KSUX...MAY SEE MVFR VISIBILTIES DEVELOP LATER
AT NIGHT.


&&

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

$$

UPDATE...08
SHORT TERM...JM
LONG TERM...JH
AVIATION...JM