Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 281148
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
648 AM CDT TUE JUL 28 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 351 AM CDT TUE JUL 28 2015

UNSEASONABLY STRONG WAVE MOVING ALONG THE INTERNATIONAL BORDER EARLY
THIS MORNING...WITH STRONG WARM LAYER ALOFT AND LOW LEVEL JET ACROSS
THE CWA. MCS WITH ORIGINS IN WESTERN HIGH PLAINS CONTINUES TO WORK
EASTWARD ACROSS THE AREA EARLY THIS MORNING...FEATURING MAINLY SUB
SEVERE WINDS AND HEAVY RAINFALL TO THIS POINT. SUSTAINING UPPER
FORCING IS LIFTING NORTHWARD AWAY FROM THE AREA... AND SQUALL LINE
PUSHING TOWARD A BIT MORE STABLE CONDITIONS OVERALL. SEE NO REASON
THAT CONVECTIVE LINE WILL NOT CONTINUE TO MAINTAIN IN A GRADUALLY
WEAKENING STATE AS IT PUSHES EAST AT 40 MPH THROUGH THE EARLY
MORNING HOURS. LOW LEVEL SHEAR VECTORS SUGGEST MAY HAVE TO WATCH FOR
BREAKDOWN TO A FEW VORTICES...BUT HAVE BEEN UNABLE TO ESTABLISH
PERSISTENT ENOUGH UPDRAFTS ALONG THE LEADING EDGE TO THIS POINT...
AND PROSPECT FOR KEEPING FOCUSED UPDRAFTS WILL NOT GET ANY BETTER
WITH THE STATE OF THE AIRMASS. BOUNDARY WILL START TO LAY OUT A BIT
MORE THROUGH THE SOUTHERN CWA WITH TIME EARLY MORNING...AND HAVE
LINGERED SOME CHANCE LEVEL POPS INTO MID TO LATE MORNING ALONG THE
LOWER MISSOURI VALLEY. MAIN SURFACE BOUNDARY AND SHARPER DRYING BACK
WEST OF THE CWA AT 09Z...AND THIS MOISTURE DISCONTINUITY WILL
PROVIDE THE NEXT CHANCE FOR PRECIPITATION DURING THE AFTERNOON
HOURS. HOWEVER...WARM TEMPS ALOFT AND MODIFICATION OF THE AIRMASS BY
SQUALL LINE WILL PROVE DIFFICULT TO DESTABILIZATION. ALTHOUGH
SURFACE BOUNDARY HAS TRENDED JUST A TOUCH SLOWER THAN EARLIER RUN...
QUESTION WHETHER WILL BE ABLE TO REACH A RENEWED CONVECTIVE POINT
NEAR THE BOUNDARY AS IT WORKS TO CLEAR THE CWA DURING THE AFTERNOON.
ENOUGH OF A CAP INDICATED ON FAIRLY WARM RAP TO REALLY LIMIT ANY POP
MENTION TO LOWER CHANCE...AND SHOULD BE LARGELY CLEAR OF THE FAR
SOUTHEAST CWA BY 00-01Z.  ANY STORMS THAT DO FORM WOULD HAVE A
CONDITIONAL SEVERE HAIL OR WIND THREAT ACROSS THE SOUTHEAST CWA
AFTER 19-20Z.

LIKELY GOING TO BE BIT SLOWER RELAXING HUMIDITY IN THE SOUTHERN AND
EASTERN AREAS WITH BOUNDARY STILL WELL BACK IN NW IA AND SW MN BY
18Z...BUT EVENTUAL PASSAGE OF FRONT WILL BRING NOTICEABLY LOWER
DEWPOINTS.  STRONGER PUSH OF COOLING ALOFT WILL SETTLE IN TONIGHT AS
UPPER LOW MOVES NORTH OF THE AREA...WITH WESTERN WINDS DECOUPLING
SOME ACROSS THE SOUTH COMPARED TO NORTH.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 351 AM CDT TUE JUL 28 2015

WEDNESDAY AND THURSDAY BOTH LOOKING DRY AND WARM. WEDNESDAY ALSO
LOOKING A BIT WINDY...ESPECIALLY NORTH OF INTERSTATE 90 WHERE A FEW
GUSTS OF 30 TO 35 MPH ARE LIKELY. BY THURSDAY THE GRADIENT WILL
WEAKEN BUT THE LOW LEVEL AIR MASS LOOKS A BIT WARMER. HIGHS
WEDNESDAY IN THE LOWER TO MID 80S AND THURSDAY THE MID 80S TO LOWER
90S.

IN THE OUTER PERIODS(FRIDAY THROUGH MONDAY)...NORTHWEST FLOW ALOFT
IN PLACE THROUGH THE PERIOD WITH HIGHS MAINLY IN THE 80S AND LOWS
MAINLY IN THE 60S. SATURDAY STILL LOOKING LIKE THE DAY WHEN IT COULD
GET HOTTEST SO WILL KEEP SOME 90S ACROSS THE AREA. HUMIDITY WILL
ALSO BE PRETTY NORMAL FOR THIS TIME OF YEAR...MAYBE JUST A TOUCH
BELOW NORMAL...WITH DEW POINTS IN THE 60S. WILL MAINTAIN SOME SMALL
CHANCES FOR THUNDERSTORMS SATURDAY THROUGH MONDAY BUT AT THIS TIME
NOT CONFIDENT ENOUGH TO ADD ANYTHING OTHER THAN THAT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 647 AM CDT TUE JUL 28 2015

MAIN ISSUES WITH AVIATION DEAL WITH DEPARTING CONVECTION IN
NORTHWEST IOWA...AND POTENTIAL FOR REDEVELOPMENT THIS AFTERNOON.
COULD YET SEE A COUPLE OF SHOWERS AROUND KSUX THROUGH THIS
MORNING. WAKE OF CONVECTIVE LINE BACK TO LOCATION OF THE
FRONTAL ZONE IN THE WESTERN CWA COULD SEE A BRIEF PERIOD OF MVFR
CEILINGS. OTHERWISE...WIND GUSTS OF 25 TO 30 KNOTS WILL BE
POSSIBLE AS MIXING INCREASES BEHIND BOUNDARY LATER THIS MORNING
AND AFTERNOON.

&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...08
AVIATION...CHAPMAN


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