Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 112344
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
644 PM CDT FRI APR 11 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 410 PM CDT FRI APR 11 2014

QUIET START TO THE NIGHT WITH SOUTHERLY WINDS SLOWLY INCREASING
THROUGH THE EVENING AS THE GRADIENT TIGHTENS IN ADVANCE OF
APPROACHING LOW PRESSURE. BY THE LATE EVENING/EARLY NIGHT TIME
HOURS...MAY SEE SCATTERED SHOWERS DEVELOP ACROSS OUR NORTH AND EAST
WITH INCREASING THETA E ADVECTION AND LOW LEVEL CONVERGENCE AS A LOW
LEVEL JET DEVELOPS ACROSS THE AREA AND A SHORTWAVE DROPS THROUGH THE
REGION. WILL MOST LIKELY HAVE SOME THUNDERSTORM ACTIVITY IN OUR
SOUTHEAST LATER AT NIGHT WHERE BETTER INSTABILITY WILL
EXIST...THOUGH CONVECTIVE PARAMETERS DO NOT SUGGEST THAT ANY OF THIS
ACTIVITY WOULD BE SEVERE. WITH WARM AIR ADVECTION AND BREEZY
CONDITIONS IT WILL BE A MUCH MILDER NIGHT WITH LOWS IN THE MID 40S
TO LOWER 50S.

ANY OF THE SHOWER/THUNDERSTORM ACTIVITY SHOULD BE EXITING OUR FAR
EAST ON EARLY SATURDAY MORNING...OTHERWISE IT WILL BE A MIXY DAY
WITH RELATIVELY BREEZY NORTHWEST WINDS ON THE BACKSIDE OF THE LOW
PRESSURE...AND LOOKING AT HIGHS GENERALLY LOWER TO MID 70S. COULD
SEE SOME SHOWER/THUNDERSTORM ACTIVITY DEVELOP OVER OUR FAR SOUTHEAST
IN THE LATE AFTERNOON ALONG A TRAILING COLD FRONT...THOUGH ONLY
INCLUDED ISOLATED THUNDERSTORMS WITH THE BETTER INSTABILITY WELL TO
OUR SOUTH. IN TERMS OF FIRE WEATHER...WILL MOST LIKELY HAVE A VERY
HIGH FIRE DANGER AGAIN ON SATURDAY...WITH THE WARM TEMPERATURES AND
BREEZY CONDITIONS...THOUGH AFTERNOON RELATIVE HUMIDITY VALUES LOOK
TO BE HIGHER THAN TODAY.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 410 PM CDT FRI APR 11 2014

MUCH COOLER START TO THE FORECAST IN THE MEDIUM RANGE WITH
INCREASING NORTHEAST FLOW DEVELOPING AS SURFACE LOW MOVES ACROSS THE
CENTRAL PLAINS.  RIGHT REAR QUADRANT OF THE UPPER LEVEL JET CREATING
A LARGE AREA OF NEGATIVE Q ACROSS THE FORECAST AREA.  STRONG
FRONTOGENETIC FORCING IS EXPECTED TO RESULT IN A BAND OF
PRECIPITATION DEVELOPING. EXPECT PRECIPITATION TO BEGIN AS
RAIN...BUT AS THE COLD AIR WRAPS INTO THE BACK SIDE OF THE BAND
EXPECT PRECIPITATION TO MIX WITH AND CHANGE OVER TO SNOW.  TOUGH
CALL ON SNOWFALL AMOUNTS...BUT HAVE BUT HAVE ADDED SOME MINOR
ACCUMULATIONS ACROSS THE NORTHERN PORTIONS OF THE FORECAST AREA.

EXPECT THE BAND TO SLIDE TO THE SOUTHEAST DURING THE DAY ON SUNDAY.
RAIN MAY CONTINUE TO MIX WITH SNOW ON THE BACKSIDE OF THE BAND...BUT
AM NOT EXPECTING MUCH IN THE WAY OF ACCUMULATIONS AT THIS POINT.
WITH THE BRISK NORTH WIND AND PRECIPITATION...EXPECT IT TO BE A
RELATIVELY RAW DAY WITH TEMPERATURES STRUGGLING TO CLIMB INTO THE
LOWER 40S.  THE SYSTEM QUICKLY EXITS OUT OF THE REGION IN THE LATE
AFTERNOON AND EARLY EVENING HOURS BUT THE COOL AND BREEZY CONDITIONS
LINGER INTO MONDAY.

WITH STRONG MIXING EXPECT TO SEE TEMPERATURES MODERATE SOME ON
MONDAY...BUT WITH 850 HPA TEMPS HOVERING IN THE - 6 TO -10 C RANGE
STILL EXPECT ANOTHER DAY WITH TEMPERATURES BELOW NORMAL WITH HIGHS
IN THE LOWER 40S.

UNSETTLED PATTERN SETTING UP TUESDAY NIGHT INTO THURSDAY AS WARM
FRONT LIFTS NORTH AS A SERIES OF PHASED UPPER LEVEL WAVES MOVE
THROUGH THE NORTHERN HALF OF THE US.  TOUGH CALL ON PRECIPITATION
TYPE IN THE NORTHERN HALF OF THE FORECAST AREA NORTH OF THE WARM
FRONT...WHILE SOUTH OF THE FRONT LOOKS TO BE RAIN.  INCREASED POPS
OVER GUIDANCE AND TIGHTENED DIURNAL RANGE THROUGH THE PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 644 PM CDT FRI APR 11 2014

VFR CONDITIONS EXPECTED THROUGH THE PERIOD...WITH LOW LEVEL WINDS
PRESENT GREATEST AVIATION CONCERN. VARIABLE AND RELATIVELY LIGHT
WINDS AT THE START OF THE PERIOD...WITH SPOTTY GUSTS DUE TO MIXING
WHICH SHOULD DECREASE BY 01Z-02Z AS BOUNDARY LAYER DECOUPLES. LOW
LEVEL JET INCREASES ACROSS THE REGION OVERNIGHT...PRESENTING LOW
LEVEL WIND SHEAR CONCERNS FOR KFSD/KSUX TAF SITES...PRIMARILY AFTER
06Z WHEN SOUTH-SOUTHWESTERLY LOW LEVEL JET PROJECTED TO TOP 50KT
ABOVE DECOUPLED SOUTH-SOUTHEAST SURFACE FLOW.

ISOLATED HIGH-BASED SHRA/TSRA WITH WEAK ELEVATED INSTABILITY WORKING
INTO SOUTHEAST PORTIONS OF THE AREA ON THE NOSE OF THE LOW LEVEL JET.
HOWEVER CONFIDENCE IN DEVELOPMENT/LOCATION/COVERAGE NOT HIGH ENOUGH
TO INCLUDE IN KFSD/KSUX TAFS AT THIS TIME. ADDITIONAL HIGH-BASED
-SHRA MAY DRIFT THROUGH NORTHERN PORTIONS OF THE REGION OVERNIGHT.
HAVE NOT INCLUDED THESE IN TAFS AT THIS TIME AS CONFIDENCE LOW THAT
MID LEVEL LIFT WILL BE ENOUGH TO OVERCOME DRY SUB-CLOUD LAYER.
HOWEVER...ANY ISOLATED -SHRA/VIRGA WITH THIS WAVE COULD PRODUCE BRIEF
WIND GUSTS AT OR ABOVE 20KT...WHICH COULD IMPACT KHON 04Z-09Z AND
KFSD 06Z-11Z.

&&

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

$$

SHORT TERM...JM
LONG TERM...
AVIATION...JH










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