Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 020008
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
708 PM CDT MON JUN 1 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 334 PM CDT MON JUN 1 2015

FAIRLY QUIET NIGHT IN STORE ACROSS THE AREA WITH ONLY SMALL
THUNDERSTORM CHANCES IN OUR FAR NORTHWEST LATE. GUSTY SOUTHERLY
WINDS WILL FALL OFF IN THE EVENING...THOUGH REMAIN IN THE 10 TO 15
MPH OVERNIGHT. WITH THE ONGOING SOUTHERLY FLOW IT WILL BE A MILD
NIGHT WITH LOWS IN THE MID 50S TO LOWER 60S. LATER TONIGHT A
SHORTWAVE BEGINS TO LIFT THROUGH NORTHWESTERN SOUTH DAKOTA...WITH A
STRENGTHENING LOW LEVEL JET OVER CENTRAL SOUTH DAKOTA. WHILE MODELS
ARE PORTRAYING THEIR USUAL DIFFERENCES IN HANDLING
CONVECTION...CANNOT RULE OUT A FEW THUNDERSTORMS DEVELOPING OVER
MAINLY THE NORTHERN JAMES RIVER VALLEY LATE TONIGHT INTO EARLY ON
TUESDAY MORNING. THE BETTER INSTABILITY WILL REMAIN TO THE WEST OF
OUR AREA SO NOT WORRYING ABOUT ANY SEVERE STORMS.

OTHER THAN POSSIBLE MORNING CONVECTION IN OUR NORTHWEST ON TUESDAY
MORNING...EXPECT THE REMINDER OF THE DAY TO BE DRY WITH A
STRENGTHENING CAP ACROSS THE AREA. IT WILL BE A BREEZY DAY WITH A
DECENT GRADIENT ACROSS THE REGION AND WINDS AT THE TOP OF THE MIXED
LAYER RUNNING AROUND 30 TO 35 KTS. MODEL LAYER RH TIME SECTIONS
WOULD SUGGEST A DECENT AMOUNT OF CLOUD COVER...ESPECIALLY EARLIER IN
THE DAY...THOUGH SHOULD BE ABLE TO CLIMB INTO THE MID 70S TO LOWER
80S ACROSS THE AREA BY AFTERNOON.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 334 PM CDT MON JUN 1 2015

THE MIDDLE OF THE WEEK IS HIGHLIGHTED BY UNSETTLED WEATHER. STILL
LOOKING AT ONE SHORT WAVE MOVING ACROSS THIS AREA TUESDAY NIGHT...
WITH THE ECMWF AND GFS EXTREMELY CLOSE WITH THE TIMING OF THIS
FEATURE. THE SHORT WAVE AT 500MB ENTERS ARE FAR WESTERN ZONES AT 06Z
WEDNESDAY...IS CLOSE TO I 29 AT 12Z WED...THEN IS PROGGED TO BE JUST
EAST OF OUR FORECAST AREA BY 18Z WED. HOW THE CONVECTION PLAYS OUT
TUESDAY NIGHT AND WEDNESDAY IS PROBLEMATIC...AS THE WAVE ITSELF OUT
RUNS THE LOW LEVEL WIND SHIFT LINE. IN FACT THE SURFACE WIND SHIFT
MOVES SLOWLY EASTWARD INTO OUR AREA LATE TUESDAY NIGHT AND WEDNESDAY
AND BASICALLY STALLS OUT FROM NEAR A WINDOM MN TO VERMILLION SD LINE
BY WEDNESDAY EVENING.

AS MENTIONED IN PREVIOUS DISCUSSIONS FOR TUESDAY EVENING...THE MID
LEVEL WINDS ARE FORECAST TO BE WEAK...AT ONLY ABOUT 10 TO 15 KNOTS
AT 700MB AND 20 TO 25 KNOTS AT 500MB. THE FOCUS SHOULD BE NEAR THE
SURFACE WIND SHIFT LINE IN CENTRAL SD TUESDAY EVENING...WITH THE
TRIGGER BEING THE SHORT WAVE. AGREE WITH SPC THAT THE MID LEVEL
WINDS ARE THE LIMITING FACTOR FOR SEVERE WEATHER...BUT A COUPLE OF
SEVERE CELLS MAY GET GOING IN OUR FAR WESTERN ZONES AS THE LOW LEVEL
WIND SHEAR IS STRONG...EVIDENCED BY VARIOUS HODOGRAPHS OFF OF THE
NAM AND GFS MODELS FROM 0-1KM. THE MAIN THREAT WOULD LIKELY BE LARGE
HAIL IN OUR FAR WESTERN ZONES LATER TUESDAY EVENING...POSSIBLY
WAITING UNTIL AFTER 01Z OR 02Z...WITH HAIL SIZES ABOUT 1 TO 2 INCH
IN DIAMETER. ML CAPE IS TOO HIGH OFF OF THE NAM AS THE DEW POINT
TEMPERATURES ARE TOO HIGH...BUT EVEN THE GFS HAS ML CAPE VALUES OF
AROUND 2500 J/KG IN CENTRAL SD. AFTER DISCRETE CELL INITIATION IN
THE EVENING...THE CELLS MAY MORPH INTO A BROKEN LINE OF
CONVECTION...OR A MULTICELLULAR CLUSTER AS THEY MOVE SLOWLY
EASTWARD. OF ALL THE MODELS...PREFER THE ECMWF SOLUTION BY FAR IN
HOW IT MOVES THE RAINFALL EASTWARD...AND THERE SHOULD BE VERY LITTLE
IN THE WAY OF A SEVERE THREAT EAST OF THE JAMES RIVER VALLEY
OVERNIGHT TUESDAY/EARLY WED MORNING.

SO USING THE ECMWF...STILL HAVE LIKELY POPS TUESDAY NIGHT AND
WEDNESDAY MORNING MOVING FROM WEST TO EAST ACROSS OUR AREA.
WEDNESDAY AFTERNOON IS TRICKY IN THAT THE GFS DEVELOPS AN AREA OF
CONVECTION FOR MANY OF OUR SOUTHERN ZONES ALONG THE WIND SHIFT. THIS
IS IN RESPONSE TO A CONVECTIVELY MANUFACTURED SHORT WAVE WHEREAS THE
OTHER MODELS ARE MUCH MORE TAME AND JUST KEEP MOVING THE PRECIP
EASTWARD. SO FAR NOW NOT REALLY BUYING THE GFS SOLUTION BEING SUCH
AN OUTLIER WITH THIS. CONCERNING TEMPERATURES TUESDAY NIGHT AND
WEDNESDAY...NO NEED TO MAKE HARDLY ANY CHANGES...WITH 60S TUESDAY
NIGHT FOLLOWED BY 75 TO 80 ON WEDNESDAY. IN BETWEEN THE RAIN SHOWERS
ON WEDNESDAY...THE DAY SHOULD ACTUALLY BE A FAIRLY NICE DAY WITH NOT
A LOT OF WIND.

GENERALLY FOR WEDNESDAY NIGHT AND THURSDAY...THE BETTER CONVECTIVE
CHANCES FAVORS AREAS SOUTH OF I 90. THE ECMWF AND GFS SHOW ANOTHER
SHORT WAVE MOVING PRIMARILY ACROSS OUR SOUTHERN ZONES LATE WEDNESDAY
NIGHT AND THURSDAY OVER THE LOW LEVEL WIND SHIFT BOUNDARY. THEREFORE
LIKELY POPS ARE WARRANTED FOR MANY AREAS SOUTH OF I 90 WEDNESDAY
NIGHT AND THURSDAY...TAPERING OFF HEADING NORTHWARD AS STABLE HIGH
PRESSURE INFLUENCES OUR NORTHERN ZONES MORE. DOES NOT LOOK LIKE MUCH
OF A SEVERE THREAT WEDNESDAY NIGHT AND THURSDAY...MAYBE JUST A BIT
NEAR THE WIND SHIFT FROM SIOUX CITY TO STORM LAKE. IT WILL DEPEND ON
HOW MUCH CLOUD DEBRIS HANGS AROUND ON WEDNESDAY.

ON THURSDAY NIGHT...LIKELY POPS ARE STILL WARRANTED IN OUR SOUTHEAST
ZONES IN AND CLOSE TO NORTHWEST IA. BUT THAT WOULD BE PRETTY EARLY
IN THE EVENING WITH THE SHORT WAVE PROGRESSING OUT OF HERE AFTER
EVENING. SO AFTER THURSDAY NIGHT...THIS LEAVES NOT A LOT GOING ON
UNTIL POSSIBLY LATE SATURDAY AND SATURDAY NIGHT WHEN A NORTHERN
STREAM SHORT WAVE WITH LIMITED MOISTURE MOVES THROUGH. AFTER THIS
LATE WEEK MOVES THROUGH THE REGION...A STRONG NORTHWEST FLOW OF AIR
WILL SETUP SHOP DRYING THINGS OUT FOR EARLY NEXT WEEK AND THAT MAY
LAST A WHILE. PERUSED OVER THE TEMPERATURES FROM A BLEND OF THE GFS
AND ECMWF 850MB TEMPERATURES FROM FRIDAY ONWARD...AND REALLY NOT A
LOT GOING ON WITH THEM. JUST LOOKS LIKE HIGHS ARE MAINLY IN THE
SEASONAL 70S.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 702 PM CDT MON JUN 1 2015

MAIN CONCERN IS THE POTENTIAL FOR THUNDERSTORMS TO DEVELOP IN
SOUTH CENTRAL SOUTH DAKOTA LATER TONIGHT AND TRACK INTO AREAS
MAINLY WEST OF THE JAMES RIVER LATE TONIGHT THROUGH MID MORNING
TUESDAY. KHON AREA MAY BE IMPACTED TUESDAY MORNING...HOWEVER
CONFIDENCE ON THIS SCENARIO IS TOO LOW TO MENTION IN THE TAF.
ADDITIONALLY...SOME MODELS CONTINUE TO HINTING AT MVFR STRATUS
DEVELOPMENT ON TUESDAY MORNING BUT CONFIDENCE REMAINS LOW.

&&

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

$$

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



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