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000
FXUS63 KFSD 182031
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
331 PM CDT TUE JUN 18 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 330 PM CDT TUE JUN 18 2013

THE RIDGE AXIS OVERHEAD BEGINS TO SHIFT EAST TONIGHT ALLOWING FOR A
RETURN FLOW OF MOISTURE INTO THE AREA...WITH A PRETTY GOOD SURGE OF
THETAE ADVECTION NOTED LATER TONIGHT. QUESTION BECOMES DO WE
SATURATE ENOUGH TO GET SOME ELEVATED CONVECTION. AND HOW DOES A WEAK
CAP AND DRY AIR ABOVE 700 MB IMPACT OUR CONVECTION CHANCES. BEST
CALL RIGHT NOW WOULD BE FOR INCREASING CHANCES FROM SOUTHWEST TO
NORTHEAST AFTER MIDNIGHT. ELEVATED CAPE EXPECTED TO STAY UNDER 1000
J/KG WITH EFFECTIVE SHEAR ON THE LOW SIDE...THUS ANYTHING TONIGHT
SHOULD BE SUB SEVERE WITH JUST SMALL HAIL THE MAIN THREAT. LOWS
SHOULD RUN A FEW DEGREES ABOVE NORMAL IN THE WEAK WAA
REGIME...MAINLY FROM AROUND 60 TO 65.

PROBABLY WILL CONTINUE TO SEE SOME ELEVATED CONVECTION SCATTERED
ABOUT THE AREA ON WEDNESDAY MORNING. HOWEVER ITS LOOKING
INCREASINGLY LIKELY THAT SKIES BECOME PARTLY TO EVEN POSSIBLY MOSTLY
SUNNY FOR A PERIOD DURING THE AFTERNOON. THUS WENT AHEAD AND RAISED
HIGHS A COUPLE DEGREES...WITH UPPER 70S TO MID 80S FORECAST. QUITE
POSSIBLE HIGHS END UP EVEN A FEW DEGREES WARMER THAN THIS...BUT
GIVEN CLOUD COVER UNCERTAINTY DID NOT WANT TO GO TOO HIGH AT THIS
POINT. NEXT QUESTION IS DO WE GET ANY MORE CONVECTION THAT FIRES IN
THE AFTERNOON...PROBABLY CLOSER TO SURFACE BASED. DESPITE A WEAK
SHORTWAVE SEEN ON 500 MB HEIGHT CHARTS...UPPER LEVEL SUPPORT IS
PRETTY MUCH NEUTRAL...WITH THE LARGE SCALE RIDGE OVERHEAD. LOW AND
MID LEVEL ISENTROPIC LIFT SHOULD CONTINUE FOR MUCH OF THE DAY
THOUGH. NOT MUCH OF A CAP IN PLACE...ALTHOUGH SIGNS OF A WEAK NOSE
OF WARM AIR AROUND 600 MB...AND QUITE A BIT OF DRY AIR ABOVE 700
MB...WHICH WOULD GET ENTRAINED IN ANY UPDRAFT AND LIKELY NOT ALLOW
US TO FULLY REALIZE THE FORECAST 2000+ J/KG OF CAPE. SO ITS A TOUGH
CALL...BUT MOST HI RES MODELS DO POP SOME STORMS...AND THINKING IS
WE SHOULD BE ABLE TO GET ISOLATED TO SCATTERED ACTIVITY IN THE
AFTERNOON AFTER ANY ELEVATED MORNING STORMS WIND DOWN. DEEP SHEAR IS
PRETTY WEAK...ALTHOUGH MAY HAVE JUST ENOUGH LOW LEVEL SHEAR FOR SOME
MULTICELL ACTIVITY. MOST STORMS WOULD LIKELY BE SUB SEVERE WITH
SMALL HAIL...ALTHOUGH AN ISOLATED QUARTER SIZE HAIL PRODUCING STORM
SEEMS POSSIBLE...ESPECIALLY IF WE DO GET CAPES UP AND OVER 2000 J/KG.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 330 PM CDT TUE JUN 18 2013

WEDNESDAY NIGHT INTO THURSDAY WILL SEE THE TAIL END UP THE UPPER
LEVEL SUPPORT SWING THROUGH. THUNDERSTORMS WILL CONTINUE TO BE
POSSIBLE WITH A FEW SEVERE THUNDERSTORMS NOT OUT OF THE QUESTION.
THURSDAY AFTERNOON LOOKS PARTICULARLY INTERESTING IF SOMETHING CAN
DEVELOP WITH 2500 J/KG CAPE A DECENT SFC TO 3KM BULK SHEAR. NO
DISCERNIBLE LOW LEVEL FEATURE TO WORK OFF OF BUT THERE IS A MID
LEVEL WAVE PASSING THROUGH SO THAT MIGHT BE ENOUGH TO GET THINGS
GOING IF THE CAP CAN BREAK. OTHERWISE PRETTY WINDY WEDNESDAY NIGHT
AND THURSDAY SO LOWS 65 TO 70 AND HIGHS MAINLY IN THE MID TO UPPER
80S.

THURSDAY NIGHT INTO FRIDAY NIGHT CONTINUES THE THREAT FOR SEVERE
THUNDERSTORMS AND HEAVY RAINFALL...WHICH CHANCES LIKELY BETTER
DURING THIS TIME FRAME. THE UPPER LEVEL TROUGH TO THE WEST BEGINS TO
WORK ONTO THE PLAINS WHICH HELPS FOCUS THE LOW LEVEL JET AND
INCREASES SHEAR ALOFT A BIT AS WELL. WILL JUST BE A MATTER OF
BREAKING THE CAP DURING THE DAY...WHICH SHOULD OCCUR
SOMEWHERE...LIKELY INT HE WESTERN CWA OR POINTS WEST OF THERE...THEN
FORM INTO A LARGER SCALE MCS AT NIGHT. VERY WARM CONDITIONS THROUGH
THIS TIME WITH LOWS 65 TO 70 AND HIGHS 85 TO 95.

SATURDAY INTO NEXT TUESDAY LOOKS PRETTY BUSY AS WELL BUT WILL NOT
REALLY TRY TO PIN ANYTHING DOWN AT THIS TIME. THE UPPER LEVEL WAVE
EJECTS TO THE NORTHEAST OVER THE WEEKEND THEN A FLAT RIDGE WITH
FAIRLY STRONG WEST WINDS ALOFT CONTINUES TO SUPPORT A FAVORABLE
ENVIRONMENT FOR SEVERE THUNDERSTORMS...ESPECIALLY WITH A LOW LEVEL
BOUNDARY FLOATING AROUND. OVERALL LOWS IN THE 60S AND HIGHS IN THE
80S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1213 PM CDT TUE JUN 18 2013

VFR CONDITIONS WILL CONTINUE THROUGH THE MAJORITY OF THE TAF PERIOD.
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE
LATER TONIGHT INTO THE DAY WEDNESDAY...ALTHOUGH EXPECTED AREAL
COVERAGE IS TOO LOW TO INCLUDE IN THE TAFS AT THIS TIME. BRIEF
REDUCTIONS TO MVFR WILL BE POSSIBLE IN ANY STORM. WINDS WILL
GRADUALLY INCREASE LATER TONIGHT INTO WEDNESDAY MORNING...WITH SOUTH
SOUTHEASTERLY WINDS GUSTING AROUND 20 KTS BY LATE MORNING.

&&

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

$$

SHORT TERM...CHENARD
LONG TERM...08
AVIATION...CHENARD