Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 260011
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
711 PM CDT MON AUG 25 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 258 PM CDT MON AUG 25 2014

SHORT TERM MODELS STRUGGLING THIS AFTERNOON HANDLING A WEAK
SHORTWAVE MOVING ACROSS EASTERN NEBRASKA THIS AFTERNOON.  SCATTERED
CONVECTION CONTINUES JUST SOUTH OF THE CWA ALONG ELEVATED BOUNDARY.
THIS ACTIVITY WILL CONTINUE TO PUSH MORE EAST THAN NORTH THROUGH THE
EARLY EVENING HOURS...BUT MAY TICKLE THE FAR SOUTHERN ZONES THIS
EVENING.

GUIDANCE IN GENERAL HAS SHIFTED THE HIGHEST RISK FOR RAIN FURTHER
SOUTH OVERNIGHT AS THETA-E GRADIENT DIPPED A BIT FURTHER SOUTH THAN
EARLIER THOUGHT. EXPECTATIONS OF A NARROW CORRIDOR OF THUNDERSTORMS
DEVELOPING LATE THIS EVENING ALONG GRADIENT NORTH OF OMAHA AND SOUTH
OF SIOUX CITY. SHORTWAVE ENERGY ENTERING THE WESTERN PLAINS LATE
TONIGHT SHOULD ENHANCE THIS PRECIPITATION CREATING A NARROW...BUT
HEAVY...CORRIDOR OF RAIN.  HAVE LOWERED POPS FURTHER NORTH
OVERNIGHT...AND TIGHTENED THE OVERALL GRADIENT.  GIVEN LACK OF CLOUD
COVER THIS AFTERNOON...HAVE LOWERED TEMPERATURES A FEW
DEGREES...ESPECIALLY NORTH OF INTERSTATE 90.

TUESDAY...SURFACE HIGH PRESSURE WILL DRIFT EASTWARD BY TUESDAY
MORNING PULLING DRIER AIR IN FROM THE NORTHEAST. WITH SHORTWAVE
ENERGY DEPARTING EASTWARD...HIGHEST RAIN CHANCES WILL AGAIN BE
CONFINED TO THE SOUTHERN ZONES. LESS CLOUD COVER SHOULD ALLOW FOR
TEMPERATURES TO CLIMB A FEW DEGREES HIGHER...BUT STILL SEASONABLY
COOL IN THE LOW 70S.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 258 PM CDT MON AUG 25 2014

MAIN FOCUS WILL CONTINUE TO BE ON RAIN CHANCES INTO THE EARLY
PERIODS. MODELS CONTINUE TO BE A LITTLE DIFFERENT IN TIMING WITH
THE ECMWF BEING A LITTLE SLOWER AND EVEN A LITTLE FURTHER
NORTHWEST...BUT NOT MUCH. EXPECT RAIN TO CONTINUE TO IMPACT
SOUTHERN ZONES/COUNTIES AND THEN SPREAD NORTHEAST TUESDAY NIGHT.
RAIN WILL BE ACROSS THE SOUTHERN POTION OF CWA WEDNESDAY AND
THURSDAY AS WAVE AFTER WAVE EJECTS FROM SOUTHWESTERN TROUGH.
POTENTIAL FOR QUITE HEAVY RAIN CONTINUES TO LOOK TO BE IN THE
CARDS FOR OUR SOUTHERN COUNTIES...MAINLY SOUTH OF HIGHWAY 18.
RIGHT NOW...IT LOOKS LIKE A POTENTIAL 2 TO 5 INCHES WILL BE
POSSIBLE IN THOSE AREAS WITH LIGHTER AMOUNTS TO THE NORTH. AT THIS
POINT...I DONT SEE MUCH OF A CHANCE FOR SEVERE STORMS ON
WEDNESDAY OR THURSDAY AS MAIN THREAT WILL BE THE HEAVY RAIN.
CLOUDS AND EXPECTED PRECIP WILL KEEP TEMPS WELL BELOW NORMAL FOR
THIS TIME OF YEAR ON BOTH DAYS. WILL DEFINITELY HAVE TO KEEP ON AN
EYE ON HOW SATURATED SOIL BECOMES IN THE SHORT TERM IN THOSE AREAS
AS THAT WILL HEAVILY INFLUENCE FLOOD WATCH DECISION.

AS THE HOLIDAY WEEKEND KICKS OFF...MODELS CONTINUE TO SHOW ENOUGH
ENERGY MOVING OVER THE AREA TO CONTINUE TO MENTION A CHANCE FOR
SHOWERS/STORMS ON FRIDAY AND EVEN SATURDAY IF ECMWF TURNS OUT TO
BE RIGHT. GFS WOULD LEAN TO BE MORE ON THE DRY SIDE...BUT AT THIS
POINT I HAVE DECIDED TO MENTION A CHANCE OF RAIN FOR THE WEEKEND
BUT THEN WENT DRY ON LABOR DAY ITSELF. AREAL RAIN COVERAGE WILL BE
CONSIDERABLE LESS ON THE WEEKEND AND RAINFALL AMOUNTS WILL BE
FAIRLY LIGHT. WARMED TEMPS UP ON THE WEEKEND AS RAIN CHANCES
DECREASE AND CLOUD COVER BEGINS TO THIN OR BREAK UP.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 710 PM CDT MON AUG 25 2014

FORECASTING CONVECTION THE LARGEST CHALLENGE OVER THE NEXT 24
HOURS. MOST GUIDANCE SUGGESTS THAT DEVELOPMENT WILL BE IMPEDED
FOR MUCH OF THE AREA WITH DRIER PUSH TO LOW LEVEL AIRMASS...
AND TIED TO BOUNDARY LOCATION TO THE SOUTH...AS EACH WEAK WAVE
LIFTS NORTHEAST ACROSS THE AREA. HAVE LIMITED CONVECTION MENTION
AT THIS TIME TO JUST A FEW HOURS LATER TONIGHT AND EARLY TUESDAY
MORNING FOR KSUX...WHICH WILL BE ON THE NORTHERN FRINGE OF LATER
NIGHT DEVELOPMENT TO THE SOUTH. VFR CONDITIONS ARE EXPECTED TO
PREVAIL.

&&

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

$$

SHORT TERM...DUX
LONG TERM...HEITKAMP
AVIATION...CHAPMAN





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