Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 260914
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
414 AM CDT SUN JUL 26 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 413 AM CDT SUN JUL 26 2015

THE ATMOSPHERE IN THE WAKE OF THE OVERNIGHT MCS IS VERY SUPPORTIVE
OF STRATUS DEVELOPMENT AND ALREADY STARTING TO SEE DEVELOPMENT IN
THE JAMES RIVER VALLEY. WILL MAINTAIN MOSTLY CLOUDY TO CLOUDY
CONDITIONS THROUGH THE MORNING THEN BREAKING OUT TO MOSTLY SUNNY TO
PARTLY CLOUDY CONDITIONS IN THE AFTERNOON. WITH A VERY WORKED OVER
ATMOSPHERE AND A LIGHT SOUTHEAST WIND CONVECTION VERY UNLIKELY SO
LOOKING AHEAD TO A DRY...ALBEIT INCREASINGLY HUMID DAY. HIGHS WILL
RANGE FROM THE MID 80S IN SOUTHWEST MINNESOTA TO 90 TO 95 DOWN THE
MISSOURI RIVER CORRIDOR. WILL PROBABLY SEE A COUPLE OF HOURS OF HEAT
INDICES NEAR 100 FROM ABOUT YANKTON TO SIOUX CITY BUT NOT QUITE LONG
ENOUGH FOR A HEAT ADVISORY.

BY TONIGHT A WAVE IS EXPECTED TO MOVE THROUGH NEBRASKA AND COULD
CREATE A LITTLE CONVERGENCE WHICH WOULD SUPPORT SPOTTY THUNDERSTORM
ACTIVITY. NOT EXPECTING SEVERE AT THIS TIME AND THE BETTER CHANCES
WILL BE NEAR THE MISSOURI RIVER AND ONLY SLIGHT TO LOW END CHANCE.
LOWS WILL BE WARM AND MAINLY FROM 70 TO 75.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 413 AM CDT SUN JUL 26 2015

WEAK WAVE COMING THROUGH NEBRASKA MAY YET PROVE TO SPARK A COUPLE OF
THUNDERSTORMS TOWARD THE LOWER MISSOURI VALLEY AND NORTHWEST IOWA...
ON EDGE OF BETTER WARM AIR ADVECTION AND WITH TEMPS ALOFT NOT YET
TOO WARM. HOWEVER...LOW LEVEL JET REMAINING JUST WEST AND THE
LIKELIHOOD OF ANY ACTION TURNING EAST/SOUTHEAST FROM ORIGIN IN THE
HIGH PLAINS HAVE GONE WITH NEIGHBORS ON REMOVAL OF POPS. ACTUALLY
NOT MUCH MORE TO FOCUS ON THROUGH THE DAY...WITH PERHAPS A BIT
BETTER LOWER LEVEL CONVERGENCE AT LOWER LEVELS BUILDING INTO THE
WESTERN CWA DURING THE LATTER AFTERNOON...ALONG WITH THE BETTER
POTENTIAL INSTABILITY AS WEAK WAVE BRUSHES PAST THROUGH THE WESTERN
HIGH PLAINS.

HEADING INTO MONDAY NIGHT...LIKELY THE BEST CHANCE FOR CONVECTION IN
PARTS OF THE AREA.  LOW LEVEL WARM FRONT SHOULD BE LIFTING RAPIDLY
NORTHWARD WITH STRONG LOW LEVEL JET OF 45 TO 55 KNOTS. BEST
CONVERGENCE EVOLVES ACROSS THE NORTHERN CWA WITH LEADING WAVE
SHEARING OVER THE RIDGE...SO HAVE GENERALLY PORTIONED OUT THE BETTER
CHANCE POPS IN THE NORTH...TO SMALLER SLIGHTS IN THE SOUTH...BUT
EVEN THIS COULD BE OVERDONE WITH LACK OF FOCUS FOR MUCH OF THE AREA.
LOWS IN THE STRONG SOUTHERLY FLOW WITH PLENTY OF LOW LEVEL MOISTURE
TRAPPED BELOW CAP WILL HANG UP IN THE LOWER TO MID 70S. HOWEVER...A
MUCH STRONGER WAVE WILL BE PUSHING THROUGH THE NORTHERN ROCKIES...
AND WILL DRIVE A STRONG COLD FRONT INTO THE WESTERN CWA...AND SOME
DRYING OF THE AIRMASS SHOULD LEAD TO A FEW UPPER 60S INTO THE FAR
WEST.

PACE OF THE MODEL CONSENSUS REMAINS QUICKER WITH THE DEEP TROUGH
PASSING TO THE NORTH TUESDAY INTO WEDNESDAY...AND THE ASSOCIATED
COLD FRONT. ISSUE BECOMES THE DEGREE OF WARMTH ALOFT AS FRONT
PROGRESSES TO THE SOUTHEAST...AND BOUNDARY LOOKS TO REMAIN FAIRLY
CAPPED OFF AS IT PUSHES RAPIDLY EASTWARD ON TUESDAY...REACHING NW IA
BY 18Z...AND CLEARING THE CWA BY 21Z.  BETTER UPPER FORCING WILL
PUSH OUT ACROSS THE BOUNDARY DURING THE LATTER AFTERNOON...BUT IF DO
NOT SEE A LITTLE HIGH BASED CONVECTION EARLIER IN THE DAY WITH STEEP
LAPSE RATES...HARDLY WARRANTS MORE THAN A LOW CHANCE POP ALONG AND
SOUTHEAST OF A SPENCER TO SIOUX CITY LINE BY AFTERNOON AND EARLY
EVENING.  A FEW LOCATIONS MAY BE ABLE TO SQUEAK OUT A READING AROUND
90 DEGREES...BUT GENERALLY MID TO UPPER 80S.  THE BIG STORY LOOKS TO
BE THE MUCH DRIER AIR PUSHING IN BEHIND THE BOUNDARY. A COUPLE RAW
MODEL SOLUTIONS SUGGEST UPPER 30S TO MID 40S DEWPOINTS INTO THE
WESTERN CWA. HAVE TEMPERED THIS EXTREME CHANGE A BIT...BUT WOULD NOT
BE SURPRISED TO FIND UPPER 40S TO MID 50S DEWPOINT READINGS OVER
MUCH OF SE SD BY MID AFTERNOON. HOWEVER...WILL STILL BE DEALING WITH
SOME BURLY HEAT INDEX READINGS ACROSS THE EASTERN CWA INTO THE LOWER
TO MID 90S...BEFORE LATE DAY IMPROVEMENT.

WEDNESDAY WILL BE COOLER...BUT VERY WELL MIXED TO FIND UPPER 70S TO
MID 80S ACROSS THE AREA ALONG WITH VERY COMFORTABLE HUMIDITY LEVELS.
WILL HAVE TO WATCH TO SEE IF CHANGE OF TRAJECTORY BRINGS BACK THE
MORE SMOKY CONDITIONS. FLOW TURNS A BIT MORE WEST TO SOUTHWEST ON
THURSDAY WITH TEMPS REBOUNDING SEVERAL DEGREES...BUT NO DRASTIC
INCREASE IN LOW LEVEL MOISTURE.

CONFIDENCE DIMINISHES A BIT MORE FOR THE LATTER PORTIONS OF THE
EXTENDED RANGE. CONTINUED NORTHWEST FLOW ALOFT WITH A COUPLE OF
SUBTLE WAVES/ILL TIMED WEAK FRONTAL PASSAGE. WOULD EXPECT AT LEAST A
SMALL THREAT FOR THUNDERSTORMS TO RETURN AT TIMES FROM FRIDAY TO
SUNDAY...WITH TEMPS NEAR TO A BIT ABOVE NORMAL.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1210 AM CDT SUN JUL 26 2015

THUNDERSTORMS WILL CONTINUE TO PUSH EASTWARD ACROSS THE AREA
OVERNIGHT...WITH LOCALIZED IFR VISIBILITIES IN HEAVIER STORMS.
THERE WILL BE SOME MVFR VISIBILITIES AND CEILINGS WITH THE
DEPARTURE OF THE STORMS...DISSIPATING AFTER 14Z ON SUNDAY.

&&

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

$$

SHORT TERM...08
LONG TERM...CHAPMAN
AVIATION...JM



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