Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 082333
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
633 PM CDT TUE JUL 8 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 258 PM CDT TUE JUL 8 2014

BREEZY NORTHWEST WINDS WILL CONTINUE THROUGH THE LATE AFTERNOON
HOURS DUE TO MECHANICAL MIXING.  SHOULD SEE THE GUSTS DECREASE
FAIRLY MARKEDLY THIS EVENING...BUT MAY HANG ON TO SLIGHTLY STRONGER
WINDS THAN ANTICIPATED THROUGH THE EVENING DUE TO LINGERING LOW
LEVEL COLD AIR ADVECTION IN THE EAST.  COULD ALSO HAVE AN
AFTERNOON/EARLY EVENING SHOWER IN EASTERN CWA WITH NEARLY UNCAPPED
ENVIRONMENT.  SHEAR PROFILES ARE VERY LINEAR...SO ANY STORMS THAT
DEVELOP WOULD LIKELY STRUGGLE TO BECOME ORGANIZED.

SURFACE HIGH PRESSURE REMAINS ACROSS THE AREA ON WEDNESDAY. WITH
MIXING...WILL LIKELY DEVELOP A LIGHT NORTHWEST WIND...ESPECIALLY
ACROSS THE EASTERN HALF OF THE FORECAST AREA THAT WILL LINGER
THROUGH THE DAY.  WITH DRY ATMOSPHERE...KEPT DRY FORECAST GOING WITH
SLIGHTLY BELOW NORMAL TEMPERATURES.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 258 PM CDT TUE JUL 8 2014

THE CHANCES FOR SHOWERS AND THUNDERSTORMS NOT VERY GOOD ON WEDNESDAY
NIGHT AS THE SLIGHTLY MORE UNSTABLE AIR LOOKS TO REMAIN SOUTH AND
WEST OF THE AREA. AND WITH LOW LEVEL FLOW MAINLY SOUTHEAST THE
ADVECTION OF THIS MORE UNSTABLE AIR NOT OCCURRING. WILL MAINTAIN
SOME SMALL POPS IN THE WESTERN CWA AS A WEAK WAVE MOVES THROUGH.

BY THURSDAY A STRONGER WAVE WILL MOVE EAST ALONG THE ND/SD BORDER
WHICH WILL TURN WINDS A LITTLE MORE SOUTHERLY AND
SOUTHWESTERLY...AIDING IN CONVERGENCE AND DESTABILIZATION. THIS WILL
BRING THE NEED FOR INCREASED POPS BUT THE CHANCE FOR SEVERE PRETTY
SLIM WITH GENERALLY LESS THAN 1000 J/KG OF SKINNY CAPE. THIS THREAT
WILL CONTINUE INTO THURSDAY NIGHT AND EXIT TO THE EAST LATE THURSDAY
NIGHT AND FRIDAY MORNING.

ANOTHER WEAKER WAVE WILL MOVE THROUGH ON FRIDAY AND WILL NEED SOME
LOWER END POPS TO COVER THIS THREAT. ONCE AGAIN INSTABILITY MARGINAL
SO THE SEVERE THREAT ALSO MARGINAL.

IN THE OUTER PERIODS(FRIDAY THROUGH TUESDAY)...MODELS STILL TRENDING
AND CONVERGING TOWARDS A CHILLY SUMMERTIME PATTERN. A DEEP LARGE
SCALE TROUGH/LOW PRESSURE IS EXPECTED TO DIG INTO THE GREAT LAKES
REGION SUNDAY INTO MONDAY BRINGING MUCH COOLER AIR TO THE REGION. A
FEW OF THE RUNS ARE COOL ENOUGH THAT THE NORTHEAST THIRD OF THE CWA
MIGHT NOT MAKE IT TO 70 DEGREES. THIS PATTERN SUGGESTS TEMPERATURES
MUCH BELOW NORMAL FOR MONDAY AND TUESDAY. STATISTICAL GUIDANCE
SOMEWHAT SUPPORTIVE OF THIS WITH THE MEX NUMBERS BELOW CLIMATOLOGY
AND THE ENSEMBLE MEAN EVEN COOLER. A COUPLE OF WEAK WAVES WILL MOVE
THROUGH OVER THE WEEKEND WHICH COULD BRING A FEW SHOWERS AND
THUNDERSTORMS BUT MONDAY AND TUESDAY SHOULD SEE MAINLY COOL AND
STABLE AIR WITH LOWER PROBABILITIES OF RAINFALL.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 633 PM CDT TUE JUL 8 2014

00Z TAFS HAVE SEVERAL GROUPS MAINLY DUE TO A VARIANCE IN WIND
DIRECTIONS. THE MAIN THING TO MONITOR TONIGHT IS THE THICK SMOKE
WHICH IS STREAMING DOWNWARD WITH THE NORTHWEST ALOFT FROM LARGE
FIRES IN NORTHERN CANADA. SOME OBSERVATIONS IN ND ARE SHOWING A
VISIBILITY REDUCTION AT AROUND 6 TO 7 MILES. AT THIS TIME...IT IS
DIFFICULT TO ASCERTAIN EXACTLY HOW HIGH THE SMOKE WILL BE IN OUR
FORECAST AREA...WITH KHON PROBABLY THE MOST IMPACTED. FOR
NOW...LEFT THE TAF SITES SKC WITH P6SM VISIBILITY TONIGHT...BUT
MAY HAVE TO AMEND THIS IF SOME VISIBILITY RESTRICTIONS COME TO
PASS...POSSIBLY INTO THE MVFR CATEGORY.

&&

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

$$

SHORT TERM...
LONG TERM...08
AVIATION...MJ






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