Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 301726
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1226 PM CDT SAT MAY 30 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 337 AM CDT SAT MAY 30 2015

WATER VAPOR IMAGERY SHOWS A MID-LVL DISTURBANCE CONTINUING TO ROTATE
SOUTHEAST ACROSS THE AREA THIS MORNING. SCATTERED SHOWERS OR
SPRINKLES WILL PERSIST OVER THE SOUTHEASTERN THIRD OF THE CWA
THROUGH MID-MORNING...AS A DRY LAYER OF AIR AOA 5K FT AGL ADVECTS
SOUTHWARD INTO THE AREA.  A BREEZY AND COOL SATURDAY IS EXPECTED FOR
MOST...WITH HIGH TEMPERATURES NEARLY 10 DEGREES BELOW NORMAL.
SOUNDINGS SUGGEST CU DEVELOPMENT BY EARLY AFTERNOON...AND COULD NOT
RULE OUT A FEW SPRINKLES.

OTHERWISE...A VERY CHILLY OVERNIGHT PERIOD IS EXPECTED TONIGHT AS
SKIES REMAIN CLEAR.  WILL NEED TO WATCH FOR A BIT OF STRATUS TRYING
TO ADVECT WESTWARD ACROSS NORTHERN IOWA OVERNIGHT.  TEMPERATURES
WILL FALL INTO THE 40S IN MANY AREAS.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 337 AM CDT SAT MAY 30 2015

ON SUNDAY...MID AND CLOUDS WILL INCREASE FAIRLY QUICKLY FROM THE
NORTHWEST WITH APPROACH OF THE UPPER LEVEL WAVE/WEAK JET OUT OF
THE NORTHERN ROCKIES...WITH A LITTLE STRATUS BRUSHING ACROSS THE
SOUTH. DRY AIR MASS IN PLACE TO THE EAST...WHICH WILL RESIST THE
INITIAL EFFECTS OF MID LEVEL ISENTROPIC LIFT FOR MUCH OF THE
MORNING. EVENTUALLY...PERSISTENCE AND SUPPORT OF THE DEEPER LIFT
CIRCULATION SHOULD RESULT IN COVERAGE OF SCATTERED LIGHT SHOWERS
ACROSS MAINLY EASTERN SOUTH DAKOTA ESPECIALLY DURING THE AFTERNOON
AND EARLY EVENING. WAVE REALLY SEEMS TO OUTRUN THE MID LEVEL
BOUNDARY/WARM ADVECTION GOING THROUGH THE AFTERNOON AND EVENING
HOURS...AND WILL LIKELY FIND THE DRY AIR TO THE EAST AND THE
DISJOINTED SYSTEM MAKING FOR A DIFFICULT PRECIPITATION PROGRESSION
INTO SOUTHWEST MINNESOTA. SOUNDINGS QUITE STABLE AS WELL...SO
THUNDER NOT ANTICIPATED. EVENTUALLY...GET LOW LEVEL JET BRINGING
SOME INCREASED OFF SURFACE MOISTURE TOWARD SOUTHEAST SOUTH DAKOTA
DURING SUNDAY NIGHT...AND A VERY SMALL ELEVATED CAPE COULD BE
ENOUGH FOR AN ISOLATED RUMBLE OR TWO HEADING INTO SUNDAY NIGHT
WEST OF I- 29. IN TERMS OF TEMPS...NUDGED TEMPS DOWN JUST A TOUCH
FOR SUNDAY ESPECIALLY THROUGH MID JAMES VALLEY TOWARD EAST CENTRAL
SD...GIVEN THE DEGREE OF CLOUDINESS AND IMPACT OF EVAPORATIVE
COOLING ON STABLE SOUTHEAST FLOW. WITH SOUTHEAST GRADIENT
REMAINING OVERNIGHT...WILL KEEP TEMPS MILDER IN UPPER 40S TO MID
50S ON SUNDAY NIGHT.

MID LEVEL BOUNDARY HANGING AROUND ON MONDAY...WHILE HEIGHTS CONTINUE
TO BUILD THROUGH THE PLAINS...DIVERTING THE BETTER OF WEAK FORCING
AROUND THE REGION. SPELLS LIKELIHOOD THAT PRECIPITATION THREAT WILL
BE FAIRLY SMALL...EVEN GIVEN THE MOISTURE TRANSPORT INTO THE AREA.
WORKED ON TRENDING EXISTING LOW POPS BY MONDAY MORNING DOWNWARD...
AND MAINLY A DRY AFTERNOON AND EVENING. WESTERN AREAS UNDER IMPACT
OF GREATER RIDGING AND OUT OF THE BETTER LOW LEVEL MOISTURE
TRANSPORT COULD WARM UP NICELY TOWARD 80 DEGREES...WHILE THREAT FOR
MORE CLOUDS EAST WILL MEAN BELOW TO NEAR NORMAL UPPER 60S TO MID
70S. WEAK SIGNATURE OF LOW LEVEL SYNOPTIC BOUNDARY LOOKS TO REMAIN
ACROSS AREAS WELL SOUTH AND WEST...WHICH CONCERNS THAT BETTER THREAT
FOR CONVECTIVE DEVELOPMENT OVERNIGHT MONDAY WILL REMAIN SOUTH OF THE
AREA. ASSUMING LOW LEVEL JET DOES NOT GET DIVERTED TOO MUCH...AND
WITH WEAK WAVE MOVING INTO THE WESTERN PLAINS...WILL KEEP A LOWER
LATE NIGHT CHANCE MAINLY ACROSS SOUTHEASTERN SOUTH DAKOTA.

FOR THE LONGER RANGE /TUESDAY THROUGH FRIDAY/...LOOK TO BE DEALING
WITH LARGE SCALE RIDGE AND THE MYRIAD OF SMALLER SCALE DISTURBANCES
WHICH PUSH ACROSS/THROUGH THE FEATURE.  PERSISTENT SOUTHEAST TO
SOUTH FLOW WILL INCREASE THE MOISTURE THROUGH THE PERIOD...AND WILL
PROBABLY FEEL A GREAT DEAL MORE HUMID THIS WEEK THAN HAS BEEN OF
LATE. DIURNAL RANGES ARE ALSO LIKELY TO BE SOMEWHAT RESTRAINED WITH
POTENTIAL GREATER CLOUD COVER AND INCREASED LOW LEVEL MOISTURE. POPS
ARE A REAL CHALLENGE...AS WILL GENERALLY BE BROAD BRUSHED A BIT AT
THIS RANGE GIVEN THE UNCERTAINTY IN FEATURE TIMING AND BOUNDARY
LOCATION. MESSAGE OF THIS PERIOD OF THE FORECAST IS NOT ONE OF A
TOTAL WASHOUT...BUT NUMEROUS CHANCES FOR PRECIPITATION THROUGH THE
WEEK.  SOME INDICATION THAT A MORE COHERENT SYSTEM WILL MOVE INTO
THE MEAN RIDGE AROUND WEDNESDAY NIGHT AND EARLY THURSDAY. PROSPECTS
FOR A BIT BETTER CONVERGENCE AND LOCATION OF LOWER LEVEL BOUNDARIES
ALSO INCREASES CERTAINTY IN THIS PERIOD FOR CONVECTION...BUT MUCH
WILL DEPEND ON ACTIVITY FROM EARLIER IN THE WEEK.  WOULD ALSO HAVE
TO SAY THAT A COUPLE EPISODES OF SEVERE STORMS WOULD ALSO NOT BE
UNREASONABLE FOR THE LATTER HALF OF THE WEEK...ESPECIALLY IF CAN GET
STRONGER LOW LEVEL BOUNDARY INTO THE AREA ALONG WITH AN INCREASE IN
MID LEVEL WINDS AS INDICATED BY SEVERAL MODELS BY WED NIGHT/THU/FRI.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1226 PM CDT SAT MAY 30 2015

BROKEN MVFR STRATOCU CEILINGS AT START OF THE PERIOD IN PARTS OF
THE AREA EXPECTED TO BECOME SCATTERED BY MID-LATE AFTERNOON AS
DRIER LOW LEVEL AIR CONTINUES TO WORK SOUTHWARD INTO THE REGION.
THEREAFTER VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. SOME
MODELS HINTING AT SOME MOISTURE RETURN IN THE 1500-3000FT LAYER
LATE TONIGHT/EARLY SUNDAY...BUT DOES NOT APPEAR EXTENSIVE ENOUGH
TO WARRANT MORE THAN FEW-SCT MENTION IN THE TAFS. GREATER COVERAGE
OF MID LEVEL CLOUDS GENERALLY ABOVE 12KFT EXPECTED TO OVERSPREAD
THE AREA FROM THE WEST AFTER 12Z SUNDAY. SPOTTY LIGHT RAIN SHOWERS
COULD ACCOMPANY THE INCREASING CLOUDS LATE IN THE PERIOD...BUT
MORE LIKELY TO HOLD OFF UNTIL AFTER THIS TAF PERIOD AND HAVE NOT
INCLUDED ANY MENTION OF SHRA THROUGH 31/18Z.

&&

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

$$

SHORT TERM...DUX
LONG TERM...CHAPMAN
AVIATION...JH



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