Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 300857
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
357 AM CDT THU JUL 30 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 357 AM CDT THU JUL 30 2015

ANOTHER PLEASANT DAY AHEAD WITH LESS WIND THAN YESTERDAY BUT SIMILAR
TEMPERATURES AND HUMIDITY. LOW PRESSURE PEELS OFF TO THE EAST AND
HIGH PRESSURE BUILDS ACROSS NEBRASKA...LEAVING A WEST TO NORTHWEST
WINDS ACROSS THE AREA. WITH THE ANTICIPATED LOW LEVEL TEMPERATURES
HIGHS SHOULD BE ABOUT 1 TO 2 DEGREES WARMER THAN YESTERDAY...SO
MAINLY MID TO UPPER 80S. VERY LITTLE CLOUD COVER TO SPEAK OF BUT DO
EXPECT A BAND OF MID LEVEL CLOUDS ABOUT ALONG AND SOUTH OF
INTERSTATE 90 THROUGH THE MORNING INTO THE EARLY AFTERNOON.

A JET MAX WILL DROP SOUTHEAST INTO MINNESOTA WHICH WILL BRING A WEAK
COOL FRONT AND A FEW CLOUDS INTO THE AREA...ESPECIALLY THE NORTHERN
CWA. NOT MUCH EFFECT OTHER THAN THAT...NOT EXPECTING
PRECIPITATION...AND LOWS SHOULD BE IN THE UPPER 50S TO LOWER 60S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 357 AM CDT THU JUL 30 2015

REINFORCING FRONTAL BOUNDARY NOW A BIT QUICKER ON FRIDAY...AND ALL
BUT ENSURES THAT WILL NOT HAVE TIME TO DESTABILIZE BEFORE IT CLEARS
THE LAST OF THE SOUTHERN CWA BY MID TO LATE MORNING. REFRESHED
NORTHERLY FLOW WITH JUST A TOUCH OF 925-850 HPA COOLING SHOULD LEAD
TO WELL MIXED ENVIRONMENT WITH HIGHS IN THE 80S. REALLY LOOKS TO BE
A LOW HUMIDITY DAY WITH DEWPOINTS FALLING INTO THE MID 40S TO MID
50S BY AFTERNOON. DRY AIR SHOULD LEAD TO POTENTIAL FOR A COOLER THAN
GUIDANCE NIGHT ON FRIDAY NIGHT AS WEAK RIDGE SLIDES PAST WITH
DEVELOPMENT OF RETURN FLOW LATER IN THE NIGHT.

MAIN FOCUS OF THE INTERMEDIATE TERM IS THE CONVECTIVE POTENTIAL ON
SATURDAY. MODELS ALL INDICATED SOME DEGREE OF QUICK MOVING WAVE IN
NORTHWEST FLOW MOVING THROUGH LATER SATURDAY AND SATURDAY EVENING...
WITH SOME USUAL TIMING DIFFERENCES.  WILL HAVE A FAIRLY SIGNIFICANT
ISSUE GETTING ANY MEANINGFUL MOISTURE RETURN...WHICH SHOULD ACT TO
LIMIT COVERAGE AND LONGEVITY OF PRECIPITATION. SHEAR IS QUITE
IMPRESSIVE WITH SOUTH/SOUTHWEST TO NORTHWEST FLOW LOWER TO MID
LEVELS...LEADING TO 50 TO 60 KNOTS OF A VERY DISTRIBUTED DEEP LAYER
SHEAR. CAPE PROFILES INDICATE LIKELY 1500-2000 J/KG...AND ALSO HAVE
A THICK LOOK TO THEM...WITH MUCH OF THE POSITIVE AREA IN A GOOD HAIL
REGIME.  SUPERCELLULAR ORGANIZATION SUPPORTED...AND WOULD EXPECT
STRONGER STORMS TO HAVE A FAIRLY SIGNIFICANT HAIL/WIND THREAT...
PERHAPS EVEN FOR VERY LARGE HAIL. CURRENT THOUGHT IS THAT WILL NEED
TO HAVE A FOCUS IN THE LOWER LEVEL CONVERGENCE AXIS IN ORDER TO GET
STORMS GOING...WHICH WOULD DELAY ONSET A BIT TOWARD THE LATTER
AFTERNOON FOR MOST AREAS...WITH STORMS EXITING THE SOUTHEASTERN CWA
BY MID TO LATE EVENING.

ON SUNDAY...ANOTHER QUICK MOVING WAVE...BUT ALMOST NO MOISTURE TO
WORK WITH AS FRONT PUSHES THROUGH DURING THE LATER AFTERNOON. BEST
OF THE MEAGER DYNAMICS CLIPS THE NORTHEASTERN CWA... WHERE ALSO A
BIT MORE CONVERGENT ON THE COOLER SIDE OF THE MID LEVEL THERMAL
GRADIENT.  OVERALL..SHOULD BE THE WARMEST DAY FOR MOST... WITH HIGHS
MID 80S EAST TO MID 90S WEST...AND COULD BE EVEN A BIT WARMER.
COOLER AND DRIER AIRMASS AGAIN SLIDES SOUTHWARD BEHIND BOUNDARY ON
SUNDAY NIGHT AND MONDAY...BUT A BIT STRONGER COOLING INDICATED WITH
4-6C COOLING THROUGH LOWER LEVELS. SHOULD REMAIN DRY THROUGH MONDAY
NIGHT AND WELL INTO TUESDAY FOR MOST.

TUESDAY TO WEDNESDAY PERIOD CONTINUES TO SHOW SOME FAIRLY GOOD
DEVIATION IN THE AMPLITUDE OF PATTERN...AND RESULTANT LOCATION FOR
BETTER PRECIPITATION THREAT. WILL MAINTAIN CHANCE POPS AT THIS TIME
FOR TUESDAY NIGHT/WEDNESDAY TO COVER UNCERTAINTY...BUT GAINING
EVIDENCE THAT A GREATER PORTION OF THIS COULD RUN THROUGH THE
WESTERN TO SOUTHERN CWA WITH ENSEMBLES A BIT MORE TOWARD LOWER
AMPLITUDE SIDE. TEMPS LOOK TO SHADE BACK TO NEAR OR A BIT BELOW
NORMAL THROUGH THE END OF THE PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1100 PM CDT WED JUL 29 2015

VFR CONDITIONS EXPECTED THROUGH THE PERIOD. LIGHT/VARIABLE WINDS
OVERNIGHT BECOMING NORTHWEST AROUND 6-12KTS BY MID-LATE MORNING
THURSDAY...THEN BECOMING LIGHT/VARIABLE AGAIN THURSDAY EVENING.

&&

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

$$

SHORT TERM...08
LONG TERM...CHAPMAN
AVIATION...JH



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