Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 121152
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
652 AM CDT SAT APR 12 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 456 AM CDT SAT APR 12 2014

MAINLY ZONAL MID LEVEL FLOW EARLY THIS MORNING...WITH WAVE MOVING
THROUGH EASTERN NORTH DAKOTA INTO NORTHERN MINNESOTA. STRONG LOW
LEVEL JET TO THE SOUTH OF THIS FEATURE VEERING EASTWARD AS THE
OVERNIGHT WEARS ON. INCREASE IN OTHERWISE LACKING LOW LEVEL
MOISTURE PUSHING NORTHWARD THROUGH SOUTHEASTERN NEBRASKA. AT THE
SURFACE...LOW PRESSURE/PREFRONTAL TROUGH WAS MOVING INTO THE FAR
SOUTHWEST CWA...WITH MAIN COLD AIR PUSH STILL HOLDING WELL BACK
THROUGH THE WESTERN PLAINS.

ENOUGH MID LEVEL MOISTURE ALONG WITH STEEP LAPSE RATES EARLY THIS
MORNING FOR ISOLATED TO SCATTERED HIGH BASED SHOWERS...AND EVEN A
FEW RUMBLES OF THUNDER EARLIER. STRONGER CELL SOUTH OF KFSD SHOWED
A PRETTY SOLID SMALLER HAIL SIGNATURE ON DUAL POLARIZATION RADAR
DATA. CONVERGENCE WITH LOW LEVEL JET WILL QUICKLY SHIFT NORTH/EAST
OF THE AREA...SO HAVE ONLY CARRIED A SMALL POP FOR A COUPLE HOURS
EARLY ON THIS MORNING BEFORE LARGE SCALE BECOMES LESS FAVORABLE
FOR LIFT BETWEEN EXITING WAVE AND THE APPROACHING WESTERN TROUGH
ENERGY. PREFRONTAL TROUGH WILL CONTINUE TO SETTLE SOUTHWARD
THROUGH THE DAY...AND WILL DEFLECT INCREASE IN DEWPOINTS TO
LOCATIONS AHEAD OF FEATURE ACROSS MAINLY NW IA.  TEMPS TODAY
STILL APPEAR TO BE PRIMED TO REACH PLEASANT SPRING LEVELS ACROSS
THE AREA...WITH GOOD MIXING INTO THE 70S EXPECTED BEHIND
PREFRONTAL TROUGH...DESPITE AN INCREASING AMOUNT OF HIGHER LEVEL
CLOUDS THROUGH THE AFTERNOON. A FEW SOLUTIONS INDICATE THAT
POOLING OF MOISTURE WILL EVENTUALLY GET CLOSE WITH ERODING THE
CAPPING WITH THE NOSE OF WARMER TEMPS ALOFT NEAR THIS BOUNDARY...
BUT REALLY DOES NOT WARRANT MORE THAN A LOW END/SHORT TERM/VERY
LATE AFTERNOON INTO EARLY EVENING MENTION AND ONLY IN THE EXTREME
SOUTHEASTERN CWA.

MAIN COOLING WILL BEGIN TO FALL INTO THE AREA OVERNIGHT AS WESTERN
TROUGH STARTS TO APPROACH LATE. PROGRESSION OF MID LEVEL FRONTAL
BOUNDARY IS NOW SLOWER...AS IS THE INCREASE IN FRONTOGENETIC
FORCING. HAVE SLOWED UP APPROACH OF PRECIP DEVELOPMENT UNTIL
GENERALLY AFTER MIDNIGHT...AND WITH THE SLOWER TIMING OF THE SPLIT
WAVE ENERGY...WILL COME A TENDENCY FOR A MORE SOUTHWARD TILT TO
DEVELOPMENT. NAM CONTINUES TO HOLD COURT AS THE NORTHERN OUTLIER
TO DEVELOPMENT OF POST FRONTAL PRECIPITATION LATER TONIGHT AND
INTO SUNDAY MORNING. HAD TRENDED DEVELOPMENT JUST A BIT SOUTHWARD
FITTING A STRONGER MODEL CONSENSUS. DESPITE COOLING OF AIRMASS...
DOES NOT LOOK LIKE THERE IS ENOUGH POTENTIAL FOR MUCH OF A MIX/CHANGE
UNTIL LATE AT NIGHT...AND THEN ONLY IN THE FAR NORTH/WEST EDGE OF
THE PRECIP BAND.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 456 AM CDT SAT APR 12 2014

STILL SOME GOOD FORCING AROUND ON SUNDAY AS DRY AIR GRADUALLY BUILDS
SOUTH ACROSS THE CWA. TEMPERATURES VERY MARGINAL FOR RAIN OR SNOW SO
WILL GO WITH A MIX THROUGH THE DAY AND KEEP AMOUNTS UNDER AN INCH
FOR THE MOST PART. AS THE COLD AIR BUILDS SOUTH NORTH WINDS WILL
INCREASE AND COULD APPROACH ADVISORY CRITERIA. AFTER THE HANDFUL OF
PLEASANT SPRING DAYS THAT WE HAVE HAD SUNDAY IS GOING TO SEEM
DOWNRIGHT COLD WITH TEMPERATURES IN THE UPPER 30S TO LOWER 40S IN
MANY SPOTS AND NORTH WINDS OF ABOUT 20 TO 30 MPH.

BY SUNDAY NIGHT THE FORCING SLIDES SOUTHEAST AND DRY AIR TAKES OVER
SHUTTING DOWN THE POTENTIAL FOR RAIN AND SNOW. WILL MAINTAIN SOME
POPS IN NORTHWEST IOWA THROUGH ABOUT MIDNIGHT BUT THAT SHOULD BE
ABOUT IT. TEMPERATURES LIKELY TO DROP INTO THE 20S IN MOST
LOCATIONS.

MONDAY WILL SEE THE AREA ENTRENCHED IN THE COLDER AIR. THE NAM FOR
SOME REASON QUITE A BIT COLDER THAN THE GOING FORECAST AND THE OTHER
MODELS SO WILL IGNORE FOR NOW AND STICK WITH HIGHS FROM THE UPPER
30S TO MID 40S.

HIGHS PRESSURE MOVES THROUGH ON MONDAY NIGHT WITH COLDER LOWS IN
THE 20S AGAIN. THIS WILL SET UP A SOUTHERLY FLOW FOR MOST SPOTS ON
TUESDAY BUT MODEL DIFFERENCES ARE FAIRLY SIGNIFICANT. THE EC HAS THE
ENTIRE CWA WITHIN THE WARM SECTOR...PLACING A WARM FRONT INTO
SOUTHERN ND...WHILE THE GEM KEEPS THE WARM FRONT NEAR THE MISSOURI
RIVER. AIMING TOWARDS A BLEND OF THE GFS AND EC FOR NOW SO WARMED
TEMPERATURES A BIT WITH MID 40S IN SOUTHWEST MN AND NEAR 60 IN
GREGORY COUNTY.

IN THE OUTER PERIODS...TUESDAY NIGHT THROUGH FRIDAY...MODELS STILL
CONVERGING ON A SOLUTION THAT HINTS AT THE POTENTIAL FOR A DECENT
PRECIPITATION MAKER TUESDAY NIGHT INTO THURSDAY. PLENTY OF
DIFFERENCES AMONGST THE MODELS SO NOT REALLY ABLE TO NAIL ANY
DETAILS DOWN JUST YET. THE GEM IS COLDEST AND SUPPORTS SNOW AND MORE
PRECIPITATION WHILE THE GFS IS NOT QUITE AS COLD BUT WOULD SUPPORT
SNOW AS WELL IN SOME SPOTS. THE ECMWF IS BY FAR THE WARMEST AND A
BIT OF AN OUTLIER BUT STILL NEEDS TO BE TAKEN INTO ACCOUNT SO
AGAIN...INCREASED POPS A BIT BUT CONFIDENCE NOT REAL HIGH ON ANY OF
THE IMPORTANT DETAILS. OTHERWISE THURSDAY INTO FRIDAY WILL CONTINUE
THE BELOW NORMAL CONDITIONS. STATISTICALLY LOTS OF SIGNALS TO GO
COLD. THE MEX VALUES ARE BELOW CLIMATOLOGY AND THE ENSEMBLE MEAN
NUMBERS GO EVEN FARTHER BELOW CLIMATOLOGY WHICH IS USUALLY A GOOD
SIGNAL TO GO WITHE THE MEAN NUMBERS OR COLDER. THE ECMWF ENSEMBLE
OUTPUT REALLY HITS A WEDNESDAY BEING COLDER WITH A STANDARD
DEVIATION OF 8 AND THE MEAN ABOUT 10 DEGREES COLDER THAN THE
OPERATIONAL RUN.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 652 AM CDT SAT APR 12 2014

VFR CONDITIONS ARE LIKELY THROUGH THE PERIOD FOR ALL SITES...BUT
MAY GET A BRIEF PERIOD OF MVFR CUMULUS AROUND KSUX BY EARLY AFTERNOON
RIGHT ALONG/AHEAD OF ADVANCING WIND SHIFT.  AT THIS POINT...NOT
CONFIDENT ENOUGH IN TIMING TO START MENTION OF PRECIP IN THE LAST
FEW HOURS OF THE TAF WITH DEVELOPMENT OF POST FRONTAL
PRECIPITATION...ALTHOUGH BY 09Z-12Z WINDOW COULD BE SEEING PRECIP
AROUND EACH SITE.

&&

.FIRE WEATHER...
ISSUED AT 456 AM CDT SAT APR 14 2014

INCREASING NORTHERLY WINDS BY AFTERNOON WITH LOWEST RELATIVE HUMIDITY
OF AROUND 25 PERCENT WILL CREATE A VERY HIGH RANGELAND FIRE DANGER
FOR AREAS GENERALLY EAST OF AN ARLINGTON TO YANKTON SD LINE. EARLIER
ISSUED A SPOT FORECAST FOR WILDFIRE LOCATED SOUTH OF TABOR SD.
ERRATIC AND CHANGEABLE WINDS WILL BE THE PRIMARY CHALLENGE TO ANY
CONTROL EFFORTS WITH WINDS SHIFTING EARLY THIS MORNING...AND
INCREASING BY MID TO LATE MORNING AFTER THE NORTHWARD SHIFT.

&&

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

$$

SHORT TERM...CHAPMAN
LONG TERM...08
AVIATION...CHAPMAN
FIRE WEATHER...CHAPMAN/08






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