Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 011118
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
618 AM CDT MON JUN 1 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 424 AM CDT MON JUN 1 2015

NARROW CORRIDOR OF ISENTROPIC ASCENT WILL LEAD TO THE DEVELOPMENT OF
A FEW SHOWERS THROUGH EARLY MONDAY MORNING. OTHERWISE...RATHER QUIET
CONDITIONS ARE EXPECTED IN THE SHORT TERM.  TEMPERATURES TODAY WILL
CLIMB INTO THE 70S AND 80S.  DEPENDING ON CLOUD COVER...SOME
POTENTIAL FOR TEMPERATURES TO JUMP A BIT WARMER THAN CURRENT
FORECAST. WINDS WILL ALSO INCREASE THROUGH THE DAY...PREVAILING FROM
THE SOUTHEAST.

QUIET CONDITIONS WILL CONTINUE THROUGH THE OVERNIGHT PERIOD. WILL
NEED TO MONITOR WIND CONDITIONS ESPECIALLY WEST OF THE JAMES
RIVER...WHERE WE MAY HAVE WINDS APPROACH 15 TO 20 KNOTS AT TIMES.
THERE IS AN OUTSIDE CHANCE OF AN ISOLATED SHOWER DRIFTING INTO THE
WESTERN ZONES TOWARDS DAYBREAK.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 424 AM CDT MON JUN 1 2015

WAVE PUSHING INTO THE MEAN RIDGING ALOFT LIFTS NORTHWARD EARLY
TUESDAY.  THERE WILL BE A SMALL THREAT FOR NOCTURNAL CONVECTION TO
BRUSH THROUGH THE FAR WESTERN TO NORTHWESTERN CWA EARLY IN THE DAY
ON THE NOSE OF PLUME OF WARMING ALOFT /+10 TO +12C 700 HPA/.
OTHERWISE...THE WARM TEMPS ALOFT THROUGH THE DAY SHOULD KEEP MUCH OF
THE DAY QUIET. SOME CONCERN THAT MOISTURE TRAPPED BELOW THE
INVERSION WILL IMPACT POTENTIAL OF TEMPERATURES WITH A FAIR AMOUNT
OF CLOUDS AROUND THROUGH THE DAY...BUT STILL SHOULD SEE MIXTURE OF
MID 70S TO LOWER 80S...DEPENDING ON AMOUNT OF SUNSHINE...PERHAPS
SOME MID 80S IN THE THE FAR WEST.  THE BIG STORY FOR THE DAYTIME
HOURS IS LIKELY TO BE THE STRONGER SOUTHERLY WINDS. WHILE GFS IS
LIKELY OVERDONE WITH THE 40 TO 45 KNOTS SHOWING UP IN THE UPPER
MIXED LAYER TOWARD THE JAMES VALLEY IN THE MORNING AND MIDDAY...
UNIDIRECTIONAL SOUTHERLY FLOW UP THROUGH THE LOW LEVEL JET DOES
SUGGEST BUMPING WINDS UP SEVERAL KNOTS FROM STRONGER GUIDANCE.

ACTIVE PERIOD OF WEATHER INITIATES ON TUESDAY NIGHT...BRINGING
CONCERNS FOR SEVERE STORMS. AFTER WHAT SHOULD BE A WELL CAPPED DAY
OVER THE CWA ON TUESDAY...WILL FIND STORMS INITIATING ACROSS THE
WESTERN PORTIONS OF THE STATE IN THE VERY LATE AFTERNOON AND EARLY
EVENING...CLOSER TO FORCING OF LIFT FROM THE NEXT UPSTREAM WAVE AND
WHERE DEEPER LOW LEVEL CONVERGENCE WILL BE ORGANIZING THROUGH THE
DAY. WHILE STORMS WEST WILL BE QUITE DISCRETE...TENDENCY WILL BE FOR
STORMS TO CONGEAL INTO SEVERAL SMALL LINEAR STRUCTURES...OR PERHAPS
ONE LARGER LINEAR STRUCTURE WHILE PUSHING EASTWARD THROUGH THE
NIGHT. SHEAR PROFILE WILL BECOME A BIT ENHANCED WITH INCREASE IN MID
LEVEL WINDS WITH WAVE WITH 30 TO 40 KNOTS IN PLAY. PLENTY OF
INSTABILITY WILL REMAIN AS REPLENISHED BY LOW LEVEL JET...WITH
PERHAPS 2000-2500 J/KG OF ELEVATED INSTABILITY. MODE LOOKS TO
TRANSITION STRONGLY TO WIND BY THE TIME ACTIVITY WOULD REACH THE CWA
LATER EVENING AND THROUGH THE OVERNIGHT...POTENTIALLY LARGE HAIL
REMAINING A CONCERN TO AROUND THE JAMES VALLEY TO LATE EVENING.
STORMS WILL LARGELY BE JAMES VALLEY AND WEST THROUGH THE EVENING...
PUSHING SOUTHEAST IN THE OVERNIGHT TO THE FAR CORNER OF THE CWA.

AFTER TUESDAY NIGHT...CONVECTIVE COVERAGE AND TIMING BECOMES FAIRLY
MUDDLED...WITH GUIDANCE FROM MODELS TAKING OFF ON DIFFERING TRACKS
ON HOW TO HANDLE VARIOUS WAVES AND BOUNDARIES. IF TUESDAY NIGHT
CONVECTION OCCURS ON THE ORDER OF EXPECTATIONS...THEN LIKELY THE
EFFECTIVE BOUNDARY WILL BE DRIVEN WELL SOUTHWARD TOWARD MORE
AGGRESSIVE NAM SOLUTION...AND LIMITING CONVECTION THREAT OVER A
GREATER AREA ON WEDNESDAY. EXPECT THAT WILL FIND EXISTING CONVECTION
GREETING DAY ACROSS AT LEAST THE SOUTHERN AND EASTERN
CWA...GRADUALLY WANING WITH DIURNAL CYCLE...ALTHOUGH LIKELY NOT
DISSIPATING ALL TOGETHER AS BOUNDARY STALLS AND UPPER DIV Q LINGERS
ACROSS THE SOUTH WELL INTO THE DAY. HAVE NUDGED TEMPS BACK WITH
LIKELIHOOD OF CONSIDERABLE CONVECTIVE DEBRIS AND MODIFIED AIR MASS.

ANOTHER WAVE LOOKS TO APPROACH ON WEDNESDAY NIGHT AND WANDER SLOWLY
ACROSS THE REGION THURSDAY...BUT IMPACT OF THIS MUCH MORE IN
QUESTION. WILL NOT HAVE EITHER THE INSTABILITY OR SHEAR TO WORK WITH
THAT TUESDAY NIGHT CONVECTION DOES. CONCERN WITH THIS SYSTEM WOULD
BE FOR CONVECTION TO RIDE THE GRADIENT OF BETTER INSTABILITY WHICH
WOULD TURN MORE SIGNIFICANT ACTIVITY SOUTHEASTWARD THROUGH NEBRASKA
AND INTO IOWA...WHILE THE MISSOURI VALLEY PERHAPS ENDS UP IN
PROXIMITY TO A LARGER THREAT FOR HEAVY RAINFALL...AND MORE GENERAL
SHOWERS AND STORMS HEADING NORTH FROM THERE. EVEN SHADING SOMEWHAT
LOWER THAN OFTEN OVER PREDICTED PRECIPITABLE WATER...NEAR KOAX
PROGGED VALUES ARE WELL INTO THE UPPER QUARTILE FOR THIS TIME OF
YEAR ON WEDNESDAY NIGHT AND EARLY THURSDAY...AS WELL AS SHOWING A
LARGE WARM CLOUD DEPTH.

IF THERE IS ANY QUIET PERIOD IN THE FORECAST...IT WOULD LOOK TO BE
FROM FRIDAY INTO SATURDAY. TREND WILL BE FOR TEMPS TO BE COOLER WITH
IMPACTS OF SURFACE RIDGE NOSING IN FROM THE NORTH...MAINLY 70S FOR
HIGHS AND 50S TO AROUND 60 FOR LOWS. BY LATER SATURDAY THROUGH
SUNDAY...WILL AGAIN FIND BROAD AGREEMENT FOR SOME TYPE OF WAVE
TRAVERSING RIDGE WITH BAROCLINICITY IN PLAY FOR A GREATER CHANCE OF
SHOWERS AND STORMS RETURNING.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 616 AM CDT MON JUN 1 2015

VFR CONDITIONS EXPECTED THROUGH TUESDAY MORNING. THICK MID-LVL
DECK WILL REMAIN IN PLACE NEARLY ALL DAY...AND MAY CONTINUE INTO
THE NIGHT. WINDS WILL TURN RATHER GUSTY BY THE AFTERNOON...WITH
SOUTHEAST WINDS PREVAILING.

OVERNIGHT...WINDS WILL REMAIN BREEZY WITH VFR MID-LVL CLOUDS AGAIN
EXPECTED.

&&

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

$$

SHORT TERM...DUX
LONG TERM...CHAPMAN
AVIATION...DUX



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