Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 062037
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
337 PM CDT WED MAY 6 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 336 PM CDT WED MAY 6 2015

SCATTERED SHOWERS ACROSS THE AREA DUE TO LOW LEVEL WARM AIR
ADVECTION WITH LITTLE CAPPING INVERSION ACROSS THE REGION.  NO REAL
FOCUS THROUGH THE AFTERNOON HOURS...BUT AS THE MAIN UPPER WAVE
APPROACHES FROM THE SOUTHWEST EXPECT CONVECTION TO INCREASE THROUGH
THE EVENING HOURS.  HAVE KEPT HIGH POPS THROUGH THE OVERNIGHT WITH
PWAT VALUES OVER AN INCH AS UPPER LEVEL WAVE MOVES NORTHEAST.

EXPECT PRECIPITATION TO LIFT TO THE NORTHEAST OF THE FORECAST AREA
THURSDAY MORNING AND REFOCUS THROUGHOUT THE DAY TO THE WEST AS COLD
FRONT MOVES THROUGH THE AREA. AHEAD OF THE COLD FRONT...EXPECT
ATMOSPHERE TO RE-DESTABILIZE...LEADING TO 1000-1500 J/KG OF CAPE.
AS THE FRONT MOVES THROUGH...COULD SEE A FEW STORMS APPROACH SEVERE
LIMITS ALONG AND AHEAD OF THE FRONT ACROSS THE EASTERN PORTION OF
THE CWA WITH LARGE HAIL AND DAMAGING WIND AS THE MAIN THREATS. FOR
HIGHS...HAVE SIDED WITH COOLER HIGHS ACROSS THE WEST BASED ON THE
TIMING OF THE COLD FRONT...WITH WARMER HIGHS IN THE EAST.


.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 336 PM CDT WED MAY 6 2015

THURSDAY NIGHT...THE FORECAST AREA WILL GENERALLY BE BEHIND A WIND
SHIFT TO THE WEST AND NORTHWEST. EARLY IN THE EVENING...THERE COULD
BE A FEW SHOWERS AND THUNDERSTORMS IN OUR EXTREME SOUTHEAST ZONES
AROUND SPENCER AND STORM LAKE IA...WITH A FEW MARGINALLY SEVERE. THE
BEST CHANCE FOR ORGANIZED RAINFALL WILL BE IN THE EARLY EVENING
ACROSS EAST CENTRAL SD JUST BEHIND THE WIND SHIFT...WITH SHOWERS
THEN TAPERING OFF BY LATE EVENING IN THAT AREA.

DOES NOT APPEAR TO BE A LOT GOING ON FRIDAY AND SATURDAY WITH A
STABLE NORTH TO NORTHEAST FETCH OF AIR AFFECTING THIS AREA. HIGHS
WILL BE MILD MAINLY IN THE 60S BOTH DAYS...WITH LOWS IN THE 40S TO
LOWER 50S. SATURDAY NIGHT...THE WEATHER BEGINS TO CHANGE WITH THE
FIRST OF A SERIES OF SHORT WAVES MOVING NORTHEASTWARD AHEAD OF THE
PARENT UPPER LOW SITUATED IN EASTERN CO AND WESTERN KS. BANDED
RAINFALL WILL LIKELY OCCUR EXCEPT IN SOUTHWEST MN AND CLOSE TO THE
BROOKINGS LOCATION...WHERE ONLY CHANCE POPS ARE JUSTIFIED AT THIS
TIME.

SUNDAY STILL LOOKS INTERESTING AT THE BEGINNING OF THE EXTENDED
FORECAST. BY 00Z MONDAY...THE ECMWF...GFS AND GEM GLOBAL ARE ALL
SIMILAR IN POSITIONING THE 500MB LOW CENTER FROM CENTRAL SD TO NORTH
CENTRAL NEB. OVERALL...THE SURFACE PATTERN IS ALSO VERY CLOSE
BETWEEN THE THREE SOLUTIONS...BUT ENOUGH VARIANCE THAT IT DOES MAKE
A BIG DIFFERENCE ON EXACTLY WHERE THE BEST CHANCES FOR SEVERE
CONVECTION WILL BE. FOR NOW...BLENDED THE THREE SOLUTIONS WHICH
PLACE THE SURFACE LOW JUST BARELY NORTH OF SIOUX CITY BY 00Z MONDAY.
THE ADJOINING WARM FRONT EXTENDS EASTWARD BETWEEN SPENCER AND STORM
LAKE IOWA. WIND SHEAR IS FAIRLY DEEP WITH A STRONGLY VEERING PROFILE
ALONG AND SOUTH OF THE WARM FRONT...AND 0-6KM BULK SHEAR VECTORS
AVERAGING 35 TO 50 KNOTS. SO UNLESS THINGS CHANGE...THERE IS
CERTAINLY A POTENTIAL FOR SEVERE WEATHER WITH A TORNADIC POTENTIAL
IN NORTHWEST IA AND EXTREME NORTHEAST NEB SUNDAY AFTERNOON AND
EVENING. HOWEVER IF THE SURFACE LOW AND WARM FRONT COME OUT FURTHER
SOUTH...THEN THAT SCENARIO WILL ALSO SHOVE THE SEVERE WEATHER
POTENTIAL FURTHER SOUTH. AT THIS TIME...DOUBT THERE WILL BE MUCH OF
A NORTHERLY ERROR IN THE MODELS. CONVERSELY OUR WESTERN ZONES WILL
BE CHILLY AND MUCH MORE STABLE IN NORTHERLY WINDS RAIN COOLED AIR.
FOR HIGHS ON SUNDAY...READINGS COULD VARY ANYWHERE FROM AROUND 50 IN
CHAMBERLAIN...TO THE UPPER 60S IN SIOUX CITY AND STORM LAKE IA.

BEHIND THE LOW PRESSURE AND ATTENDANT COLD FRONT...MONDAY WILL BE
MUCH COOLER WITH HIGHS MAINLY ONLY IN THE LOWER TO MID 50S WITH WHAT
LOOKS LIKE PLENTY OF CLOUD COVER AND LINGERING LIGHT SHOWERS. FOR
TUESDAY AND WEDNESDAY...LITTLE TO NO ORGANIZED PRECIPITATION IS IN
STORE WITH WARMER READINGS IN THE 60S ON TUESDAY...WARMING TO AROUND
70 ON WEDNESDAY. NOT REAL EXCITED ABOUT RAIN CHANCES ON WEDNESDAY
WITH ONLY SLIGHT CHANCE POPS JUSTIFIED PER THE ECMWF SOLUTION AND
ITS WEAK SHORT WAVE ASSOCIATED WITH WARM AIR ADVECTION OFF THE
SURFACE.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1244 PM CDT WED MAY 6 2015

DIFFICULT AVIATION FORECAST IN THE NEAR TERM WITH SCATTERED
SHOWERS ACROSS THE AREA. EXPECT A FEW MORE BREAKS IN THE ACTIVITY
THROUGH THE AFTERNOON HOURS BUT THEN EXPECT SHOWERS AND
THUNDERSTORMS TO RE DEVELOP TOWARDS 00Z AS MAIN WAVE LIFTS
NORTHEAST. THIS ACTIVITY COULD LEAD TO LOCALLY HIGHER AND
TEMPORARILY REDUCED VISIBILITIES.

IN TERMS OF CEILINGS...EXPECT CEILINGS TO HOVER IN THE MVFR RANGE
MUCH OF THE TIME...BUT COULD BRIEFLY DROP INTO THE IFR CATEGORY
WITH CONVECTION.


&&

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

$$

SHORT TERM...
LONG TERM...MJ
AVIATION...


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