Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 300326
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1026 PM CDT MON SEP 29 2014

.UPDATE...
ISSUED AT 1025 PM CDT MON SEP 29 2014

STRATUS FAIRLY MINIMAL THROUGH THE EVENING WITH JUST A RESIDUAL
PATCH DRIFTING WEST SOUTHWEST ACROSS NORTHWEST IOWA. DRIER LOW
LEVEL AIR CONTINUES TO PUSH IN FROM MINNESOTA ON EASTERLY FLOW
WITH UPPER 40S TO LOWER 50S DEW POINTS. EXPECT THAT AREA JUST
NORTH OF LOW LEVEL BOUNDARY WITH MOISTURE POOLING WOULD BE SOURCE
OF ADDITIONAL DEVELOPMENT OVERNIGHT...STARTING NEAR THE MISSOURI
RIVER. OTHERWISE...WIDESPREAD CONVECTION LINED UP THROUGH THE
WESTERN HIGH PLAINS WILL SHEAR NORTHEASTWARD THROUGH THE NIGHT.
MODELS REALLY HAVE SLOWED UP APPROACH OF CONVECTION...AND SEEMS
TO BE SLIGHTLY TOO MUCH SO BASED ON CURRENT DEVELOPMENT. WILL
HAVE SOME SLOWING OF NET PROPAGATION WITH DRY AIR INTRUSION TO THE
EAST...BUT AFTER INITIAL LINE PERHAPS WEAKENS A BIT...SECONDARY
WAVE LIFTING NORTHEAST SHOULD ONCE AGAIN INCREASE COVERAGE OF
PRECIP DURING THE EARLY TO MID MORNING ALONG ADVANCING
BOUNDARY...AND HAVE BOOSTED LATER MORNING AND EARLY AFTERNOON
POPS A BIT AS AREA PROGRESSES EASTWARD.

OTHERWISE...ONE OTHER CHANGE MADE TO FORECAST GOING OUT LATER
THROUGH TOMORROW AFTERNOON. SEVERE THREAT MAY BE MORE CONCENTRATED
ALONG SECONDARY CONVERGENCE BOUNDARY PUSHING INTO THE JAMES VALLEY
DURING THE AFTERNOON. QUITE IMPRESSIVE SHEAR AND IF CAN GET
CEILINGS CAN BREAK OUT BEHIND CONVECTION AND CONTRIBUTE TO
SLIGHTLY MORE SURFACE BASED DESTABILIZATION. IN THIS CASE...DEEP
LAYER SHEAR IS MORE THAN SUFFICIENT FOR SUPERCELLS...AND SOME
LOWER TOPPED VARIETY WOULD BE FAVORED ALONG CONVERGENCE BOUNDARY.
AREAS CLOSER TO THE DRYLINE/TRIPLE POINT TOWARD K9V9-KHON AXIS
WOULD BE OF GREATER INTEREST.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 326 PM CDT MON SEP 29 2014

EXPECT LOW LEVEL MOISTURE WHICH IS STILL AROUND TO MANIFEST ITSELF IN
EVENTUAL WIDESPREAD REDEVELOPMENT OF LOW CLOUDS OVER THE AREA
TONIGHT. EVENTUALLY EXPECT THE CLOUDS TO DEVELOP SOUTH ALL THE WAY
TO SUX/SLB WHERE THEY WERE AVOIDED LAST NIGHT AND THIS MORNING.
MEANWHILE...STRONG WAVE APPROACHING FROM THE SOUTHWEST WILL BRING
RAIN/SHOWERS AND POSSIBLY A FEW THUNDERSTORMS INTO THE SOUTHWEST
CORNER OF THE AREA. THIS ACTIVITY IN THE FORM OF A FAIRLY SOLID BAND
SHOULD CONTINUE TO EAST OF THE JAMES RIVER BEFORE DAYBREAK...AND
FURTHER EAST IN THE AREA TUESDAY MORNING. INCREASING INSTABILITY IS
THEN EXPECTED TO RESULT IN MORE SCATTERED SHOWERS AND STORMS IN THE
AFTERNOON...WITH A SLIGHT RISK OF SEVERE STORMS AS PER CONSISTENT
SPC OUTLOOKS. POPS FOR TUESDAY WILL BE KEPT PRETTY HIGH BECAUSE OF
THE EXPECTED SOLID NATURE OF THE INITIAL BAND. RAINFALL AMOUNTS
SHOULD NOT BE TOO GREAT UNLESS THE MORE SCATTERED ACTIVITY IN THE
AFTERNOON PRODUCES DECENT STORMS WITH HEAVY RAINFALL. EVEN IN THAT
CASE...THE LIKELY DECENT STORM MOTION SHOULD HELP HOLD THE MAX
POTENTIAL DOWN.

TEMPERATURES WILL COOL TAMELY TONIGHT WITH LOW LEVEL MOISTURE AND
THE LOW LEVEL FLOW WORKING TO KEEP LOWS ABOVE GUIDANCE. CLOUDS AND
RAIN WILL OF COURSE KEEP TEMPERATURES IN THE EAST DOWN
TUESDAY...THOUGH CLEARING OVER THE SOUTHWEST CORNER MAY RESULT IN
BETTER WARMING THERE. MET GUIDANCE LOOKS TOO COOL ON HIGHS WITH MAV
LOOKING A LITTLE BETTER.

WINDS ARE LIKELY TO PICK UP TO THE BREEZY OR WINDY CATEGORY TUESDAY
MAINLY IN THE WEST CLOSE TO THE TRACK OF THE NORTHEASTWARD MOVING
UPPER WAVE.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 326 PM CDT MON SEP 29 2014

POTENT NEGATIVELY TILTED UPPER LOW WILL CONTINUE TO LIFT TO THE
NORTH NORTHEAST ACROSS NORTH DAKOTA INTO SOUTHERN CANADA ON TUESDAY
NIGHT AND WEDNESDAY. ONGOING SHOWERS AND THUNDERSTORMS ALONG AND
EAST OF INTERSTATE 29 IN THE EARLY EVENING WILL SHIFT EASTWARD
THROUGH THE LATE EVENING BEFORE DIMINISHING IN COVERAGE AND
INTENSITY OVERNIGHT IN NORTHWEST IOWA. THE LOW END SEVERE THREAT
WILL ALSO LARGELY COME TO AN END AFTER MIDNIGHT.

FRONTAL BOUNDARY SAGS SOUTH OF THE FORECAST AREA ON WEDNESDAY AND
STALLS OUT. MEANWHILE...A SECOND DEEP SHORT WAVE EMERGES IN THE
CENTRAL HIGH PLAINS AND GRADUALLY SLIDES NORTHEAST THROUGH THE
REGION WEDNESDAY THROUGH THURSDAY. SCATTERED SHOWERS...PERHAPS WITH
AN ISOLATED RUMBLE OR TWO OF THUNDER WILL ACCOMPANY THIS FEATURE AND
LIFT NORTHEAST ACROSS PORTIONS OF NORTHWEST IOWA. MUCH COOLER
TEMPERATURES ALSO SETTLE INTO TO REGION.  WEDNESDAY WILL SEE HIGHS
NEAR 70...BUT WITH NORTHERLY FLOW...LIGHT RAIN IN OUR SOUTHEAST AND
MOSTLY CLOUDY SKIES ELSEWHERE...HIGHS WILL STRUGGLE TO REACH THE MID
60S ON THURSDAY.

BRISK NORTHWEST FLOW AND EXPANDING HIGH PRESSURE WILL DRY OUT THE
REGION FOR THE END OF THE WEEK. DESPITE MOSTLY CLOUDY SKIES...WINDY
CONDITIONS ON FRIDAY WILL MAKE FOR A BRISK FALL DAY WITH HIGHS ONLY
IN THE MID 50S TO NEAR 60. WINDS TURN WEST TO SOUTHWEST ON
SATURDAY...ALLOWING FOR SLIGHTLY WARMER CONDITIONS. THE GFS DROPS A
MID LEVEL WAVE ALONG THE NORTHWEST FLOW INTO SOUTHWEST
MINNESOTA...HOWEVER WITH SOME UNCERTAINTY HERE WILL LEAVE THE
FORECAST DRY...BUT WILL INCREASE THE CLOUDS IN OUR NORTHEASTERN HALF
DURING THE DAY AND EVENING.

SUNDAY AND MONDAY WILL SEE A CONTINUATION OF DRY WEATHER UNDER THE
UPPER LEVEL NORTHWEST FLOW WITH ANY SHORTWAVE ACTIVITY REMAINING TO
OUR NORTH AND EAST. HIGHS WILL CONTINUE IN THE MID 60S TO LOW 70S
THIS WEEKEND AND INTO EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 626 PM CDT MON SEP 29 2014

WARM FRONT REMAINS JUST SOUTH OF THE CWA LATE THIS
AFTERNOON...WITH STRATUS DISSOLVING BY MID-AFTN. SHORT TERM MODELS
DOING A POOR JOB HANDLING THE LOW-LVL MOISTURE...BUT IN GENERAL
ANTICIPATING REDEVELOPMENT OF MVFR CEILINGS LATER TONIGHT. THESE
CEILINGS WILL HOLD ON INTO TUESDAY MORNING...BEFORE A LINEAR BAND
OF SHOWERS AND EMBEDDED THUNDERSTORMS MOVES THROUGH THE AREA. FEEL
THE THUNDER CHANCES REMAIN LOW...SO WILL NOT INCLUDE AT THIS TIME.

THIS RAIN WILL PASS THROUGH THE AREA BY EARLY AFTERNOON AND
CEILINGS MAY TRY TO LIFT LATER IN THE AFTERNOON. DEPENDING ON THE
TIMING OF THE UPPER WAVE MOVING THROUGH...A NARROW CORRIDOR OF
CLEARING MAY DEVELOP AHEAD OF THE PRIMARY COLD FRONT POISED TO
MOVE THROUGH TUESDAY EVENING.


&&

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

$$

UPDATE...CHAPMAN
SHORT TERM...
LONG TERM...
AVIATION...DUX


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