Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 270158
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
858 PM CDT TUE AUG 26 2014

.UPDATE...
ISSUED AT 846 PM CDT TUE AUG 26 2014

MADE A FEW CHANGES WITH REGARDS TO POPS. FIRST...INCLUDED SOME
SMALL POPS FURTHER NORTH IN OUR WESTERN ZONES TO ACCOUNT FOR THE
CONVECTIVE ACTIVITY CURRENTLY GOING ON IN NORTHWEST NEB AND FAR
SOUTHWEST SD. SO THEREFORE SMALL POPS ARE NOW IN THERE FOR
CHAMBERLAIN AND HURON. THE HIGH POPS FOR OUR SOUTHERN ZONES FOR
VERY LATE TONIGHT STILL LOOK ON TARGET AS MOISTURE SURGES
NORTHWARD. BUT THIS SHOULD MAINLY BE CONFINED RIGHT ALONG OUR MO
RIVER VALLEY ZONES. LASTLY...TEMPERED THE POPS ON WEDNESDAY FOR
OUR EASTERN ZONES. LATEST INDICATIONS FROM SOME OF THE 18Z MODEL
RUNS SHOW THAT THE HIGH PRESSURE AREA TO OUR EAST MIGHT BE TOO
STRONG TO ALLOW CONVECTION TO RUN INTO SOUTHWEST MN AND IMMEDIATE
ADJACENT AREAS.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 237 PM CDT TUE AUG 26 2014

ONCE AGAIN THE FOCUS IN THE SHORT TERM WILL BE THE CONVECTION CHANCES
ACROSS THE AREA.  LOOKS LIKE THE EVENING WILL BE FAIRLY QUIET ACROSS
THE AREA AS THE FRONTAL BOUNDARY STAYS WELL TO THE SOUTH OF THE
AREA....CLOSER TO THE I-80 CORRIDOR.  AND WITH THE CONTINUATION OF
THE NORTHEASTERLY SURFACE FRONT...I WOULD NOT EXPECT THE FRONT TO
MOVE MUCH TO THE NORTH.  WITH THAT IN MIND...I HAVE POPS FAIRLY LOW
ACROSS MOST OF THE AREA THROUGH 09Z.  AFTER 09Z...START TO INCREASE
THE POPS AS ALL HIRES MODELS POINT TO THE CONVECTION DEVELOPING
RAPIDLY AS THE FRONT MOVES NORTH.  WENT WITH LIKELY POPS ACROSS THE
SOUTHERN TIER OF COUNTIES BY 12Z BUT DIDNT GET CARRIED AWAY WITH IT
AS I THINK THE MODELS MAY BE A LITTLE TOO FAR NORTH WITH FRONT AND
THEREFORE WITH CONVECTION.

WEDNESDAY LOOKS TO BE FAIRLY CLOUDY ACROSS THE AREA AND FAIRLY
WET...ESPECIALLY ACROSS THE SOUTH.  ALL MODELS INDICATE A STRONGER
WAVE TO BE EJECTED TOWARDS THE TRI STATE AREA DURING THE LATER
AFTERNOON AND EVENING AND THEREFORE INCREASED POPS TOWARDS THE
NORTHEAST PORTION OF THE CWA.  AREAS THAT DONT SEE THE PRECIP WONT
ESCAPE THE INFLUENCE OF THE WAVE AS THE CLOUDS WILL BE WIDESPREAD.
AND TEMPS WILL BE RELATIVELY COOL ONCE AGAIN FOR WEDNESDAY.  LOWERED
HIGHS A TAD FROM EARLIER FORECAST...BUT MAY NOT HAVE LOWERED THEM
ENOUGH.  THIS WILL ESPECIALLY BE TRUE IF THUNDERSTORMS PRODUCE LOW
LEVEL COLD POOL IN WHICH CASE WE COULD BE STUCK IN THE 60S IN SOME
OF THE AREA.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 237 PM CDT TUE AUG 26 2014

HEAVY RAIN SEEMS TO BE A GOOD BET ACROSS THE CWA WEDNESDAY NIGHT
INTO THURSDAY MORNING...AS A MUCH MORE DYNAMIC SHORTWAVE MOVES NORTHEAST
INTO THE REGION. RAINFALL COVERAGE AND RATES WILL GREATLY INCREASE
WEDNESDAY NIGHT AS LOW LEVEL JET INCREASES. AMPLIFYING PRECIPITATION
IS THE FACT THAT THE CWA WILL BE TEMPORARILY CAUGHT IN THE FAVORABLE
ZONES OF A DOUBLE JET STRUCTURE. WITH PWAT VALUES SO HIGH...OVER 2
INCHES...COULD SEE RAINFALL TOTALS APPROACH A FEW INCHES. LATER
SHIFTS WILL NEED TO CONSIDER A HYDROLOGIC WATCH OF SOME TYPE. FOR
NOW...WILL INCLUDE HEAVY RAIN IN GRIDS AND BUMP UP POPS FURTHER.

THURSDAY REMAINS A TRICKY FORECAST AS LARGER SYNOPTIC TROUGH REMAINS
SITUATED ACROSS COLORADO. DEPENDING ON THE TIMING OF THE INITIAL
SHORTWAVE MOVING THROUGH THE AREA...LOW-LVL CONVERGENCE ZONE REMAINS
SPRAWLED ACROSS THE REGION AND WOULD FAVOR REDEVELOPMENT DURING THE
DAY...ESPECIALLY OVER THE SOUTHEASTERN TWO THIRDS OF THE CWA.
TEMPERATURES WILL BE HIGHLY DEPENDENT ON CLOUD COVER.

MODELS IN GOOD AGREEMENT NOW...PULLING THE SYNOPTIC TROUGH THROUGH
THE MID-MISSOURI RIVER VALLEY ON FRIDAY AND SATURDAY.  THIS WOULD
KEEP A CHANCE OF RAIN ACROSS THE SOUTHEASTERN CWA INTO FRIDAY
NIGHT...AND KEEP THE POTENTIAL FOR ADDITIONAL HEAVY RAIN OVER
NORTHWESTERN IOWA AND SOUTH CENTRAL MINNESOTA.

A TEMPORARY PERIOD OF DRY WEATHER ANTICIPATED FOR THE WEEKEND AS
TROUGHING DIGS BACK INTO THE PACIFIC NORTHWEST. TEMPERATURES WILL
RUN NEAR OR SLIGHTLY ABOVE SEASONAL NORMALS. THE NEXT CHANCE OF RAIN
WILL ARRIVE SUNDAY NIGHT AND MONDAY AS A COLD FRONT PUSHES THROUGH
THE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 638 PM CDT TUE AUG 26 2014

MAIN AVIATION CONCERNS THIS PERIOD WILL BE SOUTH OF INTERSTATE 90
CLOSER TO THE MISSOURI RIVER. EXPECT AN AREA OF THUNDERSTORMS TO FORM
LATER TONIGHT...AND PUSH NORTH TOWARDS THE MISSOURI RIVER AFTER 09Z.
STILL SOME QUESTION AS TO HOW FAR NORTH THIS CONVECTION GETS...BUT
FEEL THE THREAT OF IT REACHING KSUX IS HIGH ENOUGH TO KEEP A TEMPO
GROUP BETWEEN 10Z AND 14Z. STORMS COULD LINGER AFTER THIS..BUT THINK
COVERAGE AND INTENSITY SHOULD BE LOWER AFTER THIS TIME...UNTIL
REGENERATION OCCURS WEDNESDAY EVENING. SHOULD HAVE SOME MVFR...OR
EVEN IFR...CIGS ACCOMPANY THESE STORMS...WITH THESE LOWER CIGS
POTENTIALLY LINGERING INTO MID AFTERNOON AT KSUX. KEPT THINGS VFR AT
KFSD AS FEEL LIKE REDUCTIONS SHOULD MOST LIKELY HOLD OFF UNTIL JUST
AFTER THE TAF PERIOD.


&&

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

$$

UPDATE...MJ
SHORT TERM...HEITKAMP
LONG TERM...DUX
AVIATION...CHENARD





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