Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 040235
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
935 PM CDT FRI JUL 3 2015

.UPDATE...
ISSUED AT 935 PM CDT FRI JUL 3 2015

EXPANDING MENTION OF PATCHY SMOKE TO COVER THE CWA FOR THE REST OF
TONIGHT. WHILE VISIBILITY IS NOT AS LOW AS AREAS TO OUR NORTH...WE
ARE BEGINNING TO SEE HINTS OF VISIBILITY DROPPING OFF THROUGHOUT
THE AREA. DO NOT HAVE A REALLY GOOD HANDLE ON WHEN THE SMOKE WILL
DISPERSE TO ALLOW FOR IMPROVING VISIBILITY...BUT THINK INCREASE
IN SOUTHERLY FLOW AFTER DAYBREAK SATURDAY SHOULD HELP. REMAINDER
OF FORECAST LOOKS PRETTY GOOD FOR TONIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 248 PM CDT FRI JUL 3 2015

SURFACE HIGH PRESSURE LEADING TO VERY LIGHT WINDS AROUND THE REGION.
EXPECT CONDITIONS TO CONTINUE...WITH FILTERED SUNSHINE WITH FAIR
WEATHER CUMULUS FIELD DYING AWAY TOWARDS SUNSET.  SATELLITE
INDICATING THERE IS A BIT OF SMOKE LEAKING INTO WEST AND NORTH
FRINGES OF THE FORECAST AREA...BUT AS SOUTHERLY FLOW DEVELOPS
OVERNIGHT AS SURFACE RIDGE NUDGES EAST...COULD BE DIFFICULT FOR
SMOKE TO ESTABLISH A SIGNIFICANT RESIDENCE TIME.

SOUTHERLY FLOW INCREASES FROM WEST TO EAST ON SUNDAY. WEAK WAVE
MOVES THROUGH THE AREA...AND MAY BE ENOUGH TO IGNITE SOME MID AND
LATE AFTERNOON CONVECTION IN THE WEST.  WITH EFFECTIVE SHEAR NEAR 40
KNOTS AND MU CAPE OF 2000-2500 J/KG...A FEW OF THE STRONGER STORMS
COULD PRODUCE MARGINALLY SEVERE HAIL OR AN ISOLATED DAMAGING WIND
GUST.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 248 PM CDT FRI JUL 3 2015

SEVERE WEATHER CHANCES SUNDAY EVENING AND NIGHT REMAIN THE AREA OF
FOCUS FOR THE MEDIUM AND EXTENDED PORTIONS OF THE FORECAST.
OVERALL...ONLY SLIGHTLY MODIFICATIONS MADE TO THE ONGOING FORECAST.

SATURDAY NIGHT...ISOLATED TO SCT THUNDERSTORMS IN AND NEAR THE MO
RIVER VALLEY REGION OF CENTRAL SD WILL LINGER INTO THE EARLY EVENING
HOURS. AS THE LOW-LVL JET INTENSIFIES OVERNIGHT...SOUNDINGS SHOW
CONTINUED ELEVATED INSTABILITY ANCHORED ABOVE 700MB WITH THE
POTENTIAL FOR A FEW ELEVATED STORMS WEST OF THE JAMES RIVER THROUGH
THE NIGHT. HOWEVER...THE MAIN SVR WEATHER RISK WOULD BE FOCUSED
INTO THE FIRST FEW HOURS OF THE EVENING.

SUNDAY-SUNDAY NIGHT...A RATHER WARM AND UNSTABLE AIRMASS IS EXPECTED
TO DEVELOP THROUGH THE DAY...AHEAD OF A LARGER SYNOPTIC TROUGH
DIGGING INTO THE NORTHERN PLAINS LATE IN THE AFTERNOON. BY THE
AFTERNOON...A SFC BOUNDARY WILL BECOME ESTABLISHED ACROSS CENTRAL
AND NERN SE.  AS THE ATMOSPHERE BECOME MORE UNCAPPED BY LATE
AFTN...TWO AREAS OF STORMS MAY FORM...ONE CLUSTER OVER NORTHERN AND
NORTHEASTERN SD AND A SECOND CLUSTER IN SOUTH CENTRAL SD.
EVENTUALLY THESE AREAS WILL MERGE TOGETHER AS THE FRONT DROPS
SOUTHEAST IN THE EVENING AND OVERNIGHT HOURS. GIVEN SHEAR AND
INSTABILITY PARAMETERS...CERTAINTY LOOKS LIKE A SEVERE WEATHER RISK
INTO THE OVERNIGHT HOURS. LOW LVL SHEAR NOT ALL THAT
IMPRESSIVE...BUT WITH INCREASE MID-UPR LVL WINDS IN THE EVENING...STORMS
SHOULD BE CAPABLE OF PRODUCING VERY LARGE HAIL AND DAMAGING
WINDS...EVENTUALLY MERGING INTO A LARGER MCS MORE CAPABLE OF
STRONG WINDS AS IT SLIDES EAST SOUTHEAST. STORMS WILL MOVE ACROSS
THE CWA THROUGH MONDAY MORNING...WITH WANING INSTABILITY FURTHER
EAST INTO MN/IA LESSENING THE SEVERE RISK SOME.

COOL AND DRY WEATHER WILL RETURN FOR THE FIRST FEW DAYS OF NEXT
WEEK. SCATTERED RAIN CHANCES WILL RETURN BY WEDNESDAY AND
THURSDAY...BUT WITH FAIRLY DISORGANIZED AND WEAK FLOW...ALONG WITH
MORE STABLE EASTERLY LOW LVL FLOW...OVERALL SEVERE WEATHER RISKS
WOULD BE LOW.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 635 PM CDT FRI JUL 3 2015

MAINLY VFR CONDITIONS AND VERY LIGHT WINDS EXPECTED TONIGHT AS
SURFACE HIGH PRESSURE SLOWLY SHIFTS EAST. BASE OF SMOKE LAYER ALOFT
APPEARS TO BE IN 4-6KFT LAYER PER MID-LATE AFTERNOON PIREPS...AND
FORECAST SOUNDINGS SHOW THIS WEAK INVERSION MIXING OUT ACROSS FAR
NORTHERN PARTS OF OUR AREA OVERNIGHT. THIS COULD ALLOW SMOKE TO
BECOME MORE SURFACE BASED...WITH SURFACE VISIBILITY DROPPING INTO
MVFR RANGE. TIMING FOR THIS TO OCCUR IS UNCERTAIN AS HAVE ALREADY
BEEN SEEING THIS IN AREAS TO OUR NORTH AND WEST THROUGHOUT THE DAY.
HOWEVER...DID INTRODUCE PERIOD OF MVFR VISIBILITY IN SMOKE AT KHON
AFTER 06Z FOR NOW...CARRYING THROUGH 13Z WHEN SLIGHTLY STRONGER
SOUTHERLY FLOW SHOULD HELP DISPERSE THE SMOKE PARTICLES AND BRING
SOME IMPROVEMENT TO SURFACE VISIBILITY. AT THIS TIME...UNCERTAINTY
IS TOO HIGH TO BRING REDUCED VISIBILITY AS FAR SOUTH AS KFSD/KSUX
BUT WILL CERTAINLY MONITOR TRENDS AND AMEND IF NEEDED.


&&

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

$$

UPDATE...JH
SHORT TERM...
LONG TERM...DUX
AVIATION...JH



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