314
FXUS63 KFSD 122332
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
632 PM CDT WED AUG 12 2020
SHORT TERM
(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 325 PM CDT WED AUG 12 2020
THE LOW LEVEL JET HAS REMAINED FIRMLY PLANTED ACROSS THE AREA,
USHERING IN WARM AND MOIST AIR WITH ITS BREEZY WINDS. AREAS ALONG
AND EAST OF THE I-29 CORRIDOR HAVE HAD A BROKEN STRATUS DECK STICK
AROUND MOST OF THE DAY, BUT DESPITE THAT TEMPERATURES HAVE CLIMBED
UP INTO THE MID TO UPPER 80S FOR MOST EXCEPT THOSE ALONG THE BUFFALO
RIDGE IN SW MN. THE LLJ HAS BEEN TRIGGERING A COUPLE SHOWERS WITHIN
NW IA AND SW MN, WITH THAT ACTIVITY EXPECTED TO CONTINUE INTO THE
EVENING HOURS. AS FOR THE THUNDERSTORMS THAT WERE EXPECTED ALONG THE
MO RIVER VALLEY IN CENTRAL SD, NO STRONG TRIGGERING MECHANISMS HAVE
PASSED OVERHEAD. BECAUSE OF THIS, THERE HAS ONLY BEEN A COUPLE
SHOWERS WITH ISOLATED THUNDER FORM AND ARE THUS NO LONGER EXPECTING
SEVERE WEATHER.
WILL LIKELY SEE THE SHOWERS CONTINUE TO FORM DUE TO THE LLJ
OVERNIGHT IN SW MN AND NW IA, BUT OTHERWISE WILL BE A RELATIVELY
QUITE NIGHT WITH LOW TEMPERATURES NEAR 70. THE WINDS INCREASE AFTER
SUNRISE WITH TEMPERATURES RISING INTO THE MID 80S AGAIN ON THURSDAY.
WITH THE SYNOPTIC SETUP REMAINING LARGELY UNCHANGED, ANOTHER BROKEN
STRATUS DECK IS LIKELY TO DEVELOP TOMORROW WHICH WILL KEEP MOST
AREAS FROM REACHING INTO THE 90S. MORE SHOWERS AND ISOLATED
THUNDERSTORMS WILL LIKELY FORM ACROSS NW IA AND SW MN DURING THE
AFTERNOON. WHILE STORMS AREN'T EXPECTED TO DEVELOP IN THE AREA, THEY
WILL LIKELY FORM IN SOUTHERN ND OR CENTRAL SD DURING THE AFTERNOON
AND TRAVEL INTO THE AREA OVERNIGHT. THE NAM BASED CAMS ALL SHOW A
GROUP/LINE OF STORMS FORMING, WITH VARYING SPATIAL AND TEMPORAL
SOLUTIONS. WITH MLCAPE VALUES IN EXCESS OF 3000 J/KG, SPC'S MARGINAL
RISK FOR OUR AREA SEEMS WARRANTED ALTHOUGH BULK SHEAR VALUES ARE
LESS THAN IDEAL FOR SEVERE WEATHER.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 325 PM CDT WED AUG 12 2020
AFTER ANY LINGERING SHOWERS AND THUNDERSTORMS EXIT OFF TO OUR EAST,
THE LLJ WILL CONTINUE TO BRING IN ABOVE NORMAL TEMPERATURES WITH
BREEZY CONDITIONS. THIS WILL LIKELY BE OUR LAST DAY WITH DEWPOINTS
IN THE 70S, AS A COLD FRONT IS GOING TO BE PUSHED ACROSS THE AREA BY
A SURFACE HIGH PRESSURE IN SOUTHERN SASKATCHEWAN. THIS COLD FRONT
WILL BE ACTING AS THE FOCUS MECHANISM FOR CONVECTION LATER IN THE
AFTERNOON, LARGELY EAST OF THE JAMES RIVER VALLEY. LOOK FOR AROUND
3000 J/KG OF MLCAPE, WITH ROUGHLY 40 KNOTS OF BULK SHEAR TO BE
AVAILABLE FOR THE STORMS TO TAP INTO. BEST SOUNDING PROFILES LOOK TO
BE ACROSS SW MN ALONG AND NORTHEAST OF THE BUFFALO RIDGE, WHERE THE
THICKEST CAPE PROFILES ARE ALONG WITH DECENT VEERING WINDS. SEVERE
THUNDERSTORMS WILL BE POSSIBLE PRIMARILY ALONG AND EAST OF THE I-29
CORRIDOR, WITH BEST CHANCES ALONG THE BUFFALO RIDGE WHICH MATCHES
WELL WITH SPCS DAY 3 MARGINAL AND SLIGHT RISK.
MODELS DISAGREE ON HOW QUICKLY THE AFOREMENTIONED COLD FRONT WILL
BE PUSHED THROUGH THE AREA, BUT THERE IS DECENT AGREEMENT THAT
TEMPERATURES WILL BECOME MORE SEASONABLE WITH HIGHS IN THE LOWER 80S
AND DEWPOINTS DROPPING BACK DOWN INTO THE 60S. A COUPLE MODELS HINT
AT SOME STORMS FORMING ALONG THE NORTHERN INSTABILITY GRADIENT LATE
SATURDAY AFTERNOON INTO SUNDAY MORNING, SO HAVE LEFT A SLIGHT CHANCE
OF THAT OCCURRING IN THE GRIDS BUT CONFIDENCE IS NOT HIGH ON THAT
OCCURRING. THE REST OF THE EXTENDED FORECAST WILL FEATURE BELOW TO
AVERAGE TEMPERATURES, WITH SLIGHTLY BREEZY DAYTIME CONDITIONS. DON'T
SEE ANY STRONG SIGNALS FOR RAIN CHANCES INTO THE MIDDLE OF THE WEEK,
LARGELY THANKS TO UPPER LEVEL RIDGING AND NORTHWESTERLY FLOW
ALOFT.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 632 PM CDT WED AUG 12 2020
WHILE NOT ZERO, CHANCES FOR PRECIPITATION OVER THE NEXT 24 HOURS
ARE RATHER REMOTE, WITH LOW CHANCES PRIMARILY CONFINED TO PORTIONS
OF SOUTHWEST MN/NORTHWEST IA, EAST OF OUR TAF SITES. COULD SEE
MVFR STRATUS AND/OR FOG IMPACT AREAS EAST OF I-29 IN THE 09Z-15Z
WINDOWS AS WELL. AGAIN THIS CURRENTLY EXPECTED TO REMAIN EAST OF
TAF SITES, BUT WILL CARRY SCT015-025 AT KFSD/KSUX TO INDICATE
PROXIMITY OF THE POTENTIAL CLOUD BANK TO OUR EAST.
SOUTHERLY LOW LEVEL JET THROUGH CENTRAL SD WILL BRING A PERIOD OF
NON-CONVECTIVE LOW LEVEL WIND SHEAR TO KHON DURING THE PRE-DAWN
HOURS, WITH THESE STRONGER WINDS ALOFT TRANSLATING TO OCCASIONAL
GUSTS 20-30KT DURING THE LATE MORNING-AFTERNOON HOURS THURSDAY.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
SHORT TERM...APT
LONG TERM...APT
AVIATION...JH
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