Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 031200
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
700 AM CDT MON AUG 3 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 357 AM CDT MON AUG 3 2015

MAIN FORECAST CONCERN IS THE POTENTIAL FOR CONVECTION BOTH TODAY AND
TONIGHT IN THE MISSOURI VALLEY.

FOR TODAY...ALL MODELS SHOW AN AREA OF 700 MB FRONTOGENESIS IN THE
MISSOURI VALLEY. WHILE THERE IS NO UPPER LEVEL WAVE TO ENHANCE THIS
CIRCULATION...THE NAM SHOWS ENOUGH INSTABILITY PRESENT FOR
CONVECTION TO DEVELOP. ALL THE HI-RES MODELS...NMM...ARW...AND
HRRR...ARE SHOWING CONVECTION DEVELOPING THIS MORNING NEAR THE SD/NE
BORDER AND LATEST FOG IMAGERY IS SHOWING A NARROW BAND OF MIDLEVEL
CLOUDS FORMING IN THIS SAME AREA. THERE IS STILL SOME QUESTION IF
CONVECTION WILL MOVE INTO FAR SRN SD...BUT POTENTIAL IS THERE TO ADD
A LOW POP INTO THE MISSOURI VALLEY WEST OF SIOUX CITY FOR TODAY. THE
BEST CHANCE FOR THIS CONVECTION WILL BE LATER THIS MORNING. DURING
THE AFTERNOON...EXPECT AN APPROACHING UPPER WAVE INTO HIGH PLAINS
WILL REFOCUS LIFT FARTHER SOUTHWEST. OTHERWISE...THE REMAINDER OF
THE AREA WILL SEE SUNNY SKIES WITH HIGHS IN THE UPPER 70S TO MID 80S.

OVERNIGHT...THE AFOREMENTIONED WAVE AND ASSOCIATED 850 MB FRONT WILL
MOVE NORTHEAST TOWARD THE SD/NE BORDER. ALL MODELS SHOW AT LEAST
MODEST...APPROXIMATELY 300-500 J/KG CAPE...FOR PARCELS LIFTED ABOVE
850 MB. THE NAM IS MUCH MORE UNSTABLE...1000 TO 2000 J/KG MUCAPE...
BUT THIS SEEMS TO BE AN INHERENT BIAS OF THE NAM FOR ELEVATED
CONVECTION AND DISREGARDED AT THIS TIME. THERE IS ENOUGH INSTABILITY
THAT EXPECT CONVECTION TO DEVELOP IN OR MOVE INTO THE MISSOURI
VALLEY AFTER SUNSET. HIGH RES MODELS DO SHOW POTENTIAL OF AN INCH OF
RAIN WITH THIS CONVECTION. AS WITH THIS MORNING...HOW FAR NORTH THE
MOST VIGOROUS CONVECTION CAN MOVE IS STILL IN QUESTION AND THE
HEAVIEST RAIN MAY REMAIN IN NORTHERN NEBRASKA. SO DID RAISE POPS TO
AROUND 50 PERCENT IN SOUTH CENTRAL SD BUT KEPT QPF LESS THAN A
QUARTER INCH AT THIS TIME. AT THIS POINT DO NOT EXPECT ANY SEVERE
WEATHER SINCE CAPE SHOULD REMAIN FAIRLY MODEST BUT SHOULD NAM
SOLUTION VERIFY...THEN MARGINALLY SEVERE HAIL WOULD BE POSSIBLE. DO
NOT EXPECT THE CONVECTION TO GET TOO FAR NORTHEAST OF THE MISSOURI
VALLEY AS THE ATMOSPHERE RAPIDLY STABILIZES AS ON APPROACHES I90.
LOWS OVERNIGHT WILL BE IN THE 50S EVERYWHERE BUT THE MISSOURI VALLEY
WHERE CLOUDS WILL KEEP TEMPERATURES IN THE LOWER TO MIDDLE 60S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 357 AM CDT MON AUG 3 2015

ON TUESDAY THE LOW LEVEL BOUNDARY LIFTS CLOSER TO THE MISSOURI RIVER
VALLEY AS A SHORTWAVE OVER EASTERN WYOMING SLIDES INTO NEBRASKA
DURING THE DAY. THIS WILL KEEP SHOWER AND THUNDERSTORM CHANCES
THROUGH THE MO RIVER CORRIDOR THROUGH THE DAY...WITH AREAS BACK TO
THE NORTH AND EAST REMAINING RAIN FREE AS A EAST/NORTHEASTERLY LOW
LEVEL FLOW FROM THE UPPER MIDWEST KEEPS DRIER AIR OVER THAT AREA.
THE BETTER INSTABILITY REMAINS TO THE SOUTH OF OUR CWA SO THINK
THERE WILL BE LITTLE CONCERN FOR SEVERE STORMS. HIGH TEMPERATURES
WILL SIT JUST EITHER SIDE OF 80 DEGREES...WITH THE SLIGHTLY COOLER
READINGS MOST LIKELY IN OUR SOUTHWEST WHERE CLOUD COVER WILL BE MOST
ABUNDANT.

BY TUESDAY NIGHT MOST MODELS HAVE THE WESTERN NEBRASKA SHORTWAVE
SPLITTING AND TAKE STRENGTHENING ENERGY INTO KANSAS DURING THE
NIGHT...AS THE NORTHERN PIECE OF ENERGY WEAKENS OVER WESTERN SOUTH
DAKOTA. THE GFS IS AN OUTLIER IN STRENGTHENING THE NORTHERN ENERGY
THROUGH THE NIGHT...AND THUS LIFTS THE BETTER PRECIPITATION CHANCES
NORTHWARD INTO OUR AREA. FOR THE MOST PART DISCOUNTED THIS
SOLUTION...WITH THE BETTER RAIN CHANCES REMAINING OVER THE MO RIVER
CORRIDOR DURING THE NIGHT.

SHOWER AND THUNDERSTORM CHANCES ON WEDNESDAY ARE DEPENDENT ON WHICH
OF THE SOLUTIONS VERIFY...AS MOST MODELS BLOW UP CONVECTION THROUGH
KANSAS WHICH MAY LESSEN OUR RAIN CHANCES HERE. AGAIN THE GFS IS AN
OUTLIER BRINGING THE STRONGER NORTHERN ENERGY INTO OUR AREA. FOR NOW
WILL LEAN CLOSER TO HEAVIER MODEL CONSENSUS WITH LESSER RAIN CHANCES
IN OUR SOUTH AND EAST...AND HIGHER POPS IN OUR WEST AND NORTH AS THE
REMNANT OF THE NORTHERN ENERGY SLIDES INTO THE AREA. TEMPERATURES ON
WEDNESDAY MAY BE A TOUCH COOLER WITH CLOUD COVER...WITH HIGHS MID
70S TO AROUND 80.

THE REMAINDER OF THE EXTENDED INTO THE UPCOMING WEEKEND LOOKS TO BE
UNSETTLED WITH FAIRLY CONSISTENT THUNDERSTORM CHANCES THROUGH THE
PERIOD AS A SERIES OF SHORTWAVES SLIDE ACROSS THE REGION.
TEMPERATURES THROUGH THE PERIOD WILL BE AT OR JUST BELOW NORMAL WITH
HIGHS GENERALLY UPPER 70S TO LOWER 80S AND LOWS MOSTLY LOWER 60S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 658 AM CDT MON AUG 3 2015

VFR THROUGH THE PERIOD. ISOLATED THUNDERSTORMS WILL BE POSSIBLE
ALONG THE MISSOURI RIVER TOWARDS KSUX AFTER 06Z TONIGHT BUT AT
THIS TIME NOT CONFIDENT ENOUGH ON TIMING AND PLACEMENT TO INCLUDE
THREAT IN THE TAF.

&&

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

$$

SHORT TERM...SCHUMACHER
LONG TERM...JM
AVIATION...SCHUMACHER



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