Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 270436
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1136 PM CDT SUN JUL 26 2015

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 356 PM CDT SUN JUL 26 2015

AN ISOLATED STORM OR TWO IS POSSIBLE IN OUR SOUTH CENTRAL SD ZONES
THIS EVENING AS THE LOW LEVEL JET RETURNS A BIT COUPLED WITH MAX
DAYTIME HEATING TRIGGERING THE CONVECTIVE TEMPERATURE. IN
ADDITION THE SURFACE WIND IS FROM AN UPSLOPE DIRECTION. THAT SAID...
NOT EXPECTING A LOT IN THE WAY OF SEVERE ACTIVITY AS THE WIND SHEAR
IS WEAK AND THE MID LEVEL WINDS ARE ONLY 15 KNOTS...AND INSTABILITY
IS NOT REAL OUTSTANDING WITH ML CAPES AROUND 1000 J/KG. IT IS FOR
THESE REASONS WHICH SHOULD KEEP CONVECTIVE DEVELOPMENT TO A MINIMUM.
AFTER EVENING TONIGHT AND LINGERING RIGHT INTO MONDAY...THE MODELS
ARE ALL OVER THE MAP IN SHOWING THEIR RESPECTIVE PRECIPITATION
SOLUTIONS WITH NO CONSENSUS. THEREFORE CONFIDENCE IS LOW AND KEPT
POP CHANCES LOW. ALL MODELS DO SHOW YET ANOTHER 700MB SHORT WAVE
MOVING INTO CENTRAL NEBRASKA BY LATE TONIGHT WHICH MAY PRODUCE A
STORM OR TWO FROM ABOUT YANKTON TO CHAMBERLAIN. IF THERE ARE A FEW
SHOWERS OR STORMS LATE TONIGHT AND EARLY MONDAY MORNING IN THAT
AREA...THEY SHOULD PROG EASTWARD TOWARD THE I 29 CORRIDOR BY MIDDAY
BEFORE DISSIPATING EAST OF I 29 WHERE THE AIR MASS IS MORE UNSTABLE
INFLUENCED BY HIGH PRESSURE OVER THE GREAT LAKES. AFTER THAT...
PERHAPS A FEW STORMS WILL POP IN THE LATE AFTERNOON IN OUR FAR
WESTERN ZONES JUST AHEAD OF THE WELL ADVERTISED UPPER TROUGH MOVING
THROUGH MONDAY NIGHT.

FOR LOWS...WITH LIGHT WINDS OUT OF THE EAST SOUTHEAST TONIGHT...
HEDGED WITH THE COOLER GUIDANCE READINGS WHICH STILL GIVES LOWS IN
THE UPPER 60S TO LOWER 70S. BUT STAYED AWAY FROM THE MID 70S WHICH
DO NOT MAKE SENSE TO ME RIGHT NOW. ON MONDAY...ANOTHER WARM AND
HUMID DAY AND IN FACT...THERE ARE SOME HEAT INDEX READINGS RIGHT
NEAR 100 DEGREES FOR A FEW HOURS IN THE AFTERNOON MAINLY IN THE
JAMES RIVER VALLEY FROM HURON TO MITCHELL. BUT THIS WAS TOO SMALL OF
AN AREA TO WARRANT A HEADLINE AT THIS TIME. IF THE TEMPERATURES LOOK
MORE HOT WITH TONIGHTS FORECAST AND 100 DEGREE HEAT INDEX READINGS
BECOME MORE WIDESPREAD...THEY COULD ISSUE A HEAT ADVISORY FOR OUR
WESTERN ZONES.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 356 PM CDT SUN JUL 26 2015

ACTIVE WEATHER EXPECTED TO PERSIST MONDAY NIGHT INTO TUESDAY NIGHT
IS ASSOCIATION WITH A POTENT UPPER LEVEL TROUGH LIFTING FROM THE
NORTHERN ROCKIES AND DEEPENING NEAR THE MONTANA...NORTH DAKOTA AND
CANADA BORDER BY TUESDAY AFTERNOON. AHEAD OF THIS SYSTEM...SOUTHERLY
FLOW INCREASES WITH A ROBUST LOW LEVEL JET DEVELOPING OVERNIGHT.
THIS WILL CONTINUE TO TAP INTO PLENTY OF MOISTURE...WHILE BREEZY
WINDS WILL HELP KEEP OVERNIGHT TEMPERATURES IN THE 70S. A WEAK
SHORTWAVE EJECTING OVER TOP OF THE RIDGE COULD PROVIDE THE BEST
FOCUS FOR THUNDERSTORM DEVELOPMENT IN THE EVENING AND
OVERNIGHT...HOWEVER OVERALL CONVERGENCE IS WEAK FOR THE BULK OF THE
FORECAST AREA. THE BEST POTENTIAL STILL LOOKS TO BE IN EAST CENTRAL
SD INTO SOUTHWEST MINNESOTA AND FAR NORTHERN IOWA. WITH STRONG
INSTABILITY AND WIND SHEAR...SEVERE WEATHER WILL BE A CONCERN WITH
ANY CONVECTION THAT DOES DEVELOP.

THE POTENT SYSTEM DROPS A COLD FRONT INTO THE WESTERN FORECAST AREA
LATE MONDAY NIGHT...WHICH STALLS EAST OF I29 ON TUESDAY AFTERNOON.
STILL SOME TIMING CONCERNS...BUT THIS BOUNDARY SHOULD BECOME THE
FOCUS FOR ADDITIONAL THUNDERSTORM ACTIVITY IN THE AFTERNOON AND INTO
EARLY WEDNESDAY. THE QUESTION WILL BE HOW WELL NORTHWEST IOWA AND
ADJACENT AREAS WILL HEAT UP AND BECOME UNSTABLE IN THE AFTERNOON.
BUT THEY COULD POTENTIALLY WILL SEE ENOUGH INSTABILITY AND SHEAR FOR
SEVERE WEATHER CONCERNS.

SOME RELIEF TO THE HEAT AND HUMIDITY RETURNS WEDNESDAY AND THURSDAY
AS NORTHWEST FLOW AND COOLER TEMPERATURES ALOFT WILL HOLD HIGH
TEMPERATURES IN THE UPPER 70S TO UPPER 80S. DRY CONDITIONS RETURN AS
WELL...BUT WITH A NORTHWEST FLOW TRAJECTORY SMOKE FROM CANADIAN
FIRES COULD MAKE A RETURN TO THE NORTHERN PLAINS.

THE UPPER RIDGE BEGINS REBUILDING TO THE WEST LATE IN THE
WEEK...WITH MID SUMMER HEAT REBOUNDING. OVERALL THE PATTERN IS
RELATIVELY DRY. THE GFS...CANADIAN AND ECMWF ALL SHOW A WEAK WAVE
DIVING SOUTHEAST LATE THIS WEEK...BUT TIMING IS STILL UNCERTAIN...AS
IS THE MOISTURE AVAILABILITY. DID NOT ALTER THE SUPERBLEND POPS MUCH
WITH LOW CONFIDENCE IN WHETHER ANY STORMS WILL MANAGE TO DEVELOP IN
THE FRIDAY NIGHT THROUGH SATURDAY NIGHT TIME FRAME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1127 PM CDT SUN JUL 26 2015

GUIDANCE SUGGESTING THE POSSIBILITY OF MVFR TO IFR STRATUS
DEVELOPING ACROSS PORTIONS OF THE AREA AFTER 10Z TONIGHT...THOUGH
DID NOT INCLUDE IN TAFS WITH MODEL DIFFERENCES. WHILE ISOLATED
THUNDERSTORMS WILL BE POSSIBLE THROUGH THE TAF PERIOD...CONFIDENCE
IN PLACEMENT AND TIMING TOO LOW TO INCLUDE IN TAFS. SOMEWHAT
BETTER AGREEMENT BY MODELS ON THUNDERSTORMS DEVELOPING WEST OF
THE INTERSTATE 29 CORRIDOR AFTER 03Z MONDAY EVENING.

&&

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

$$

SHORT TERM...MJ
LONG TERM...
AVIATION...JM



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