Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KFSD 250824
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
324 AM CDT MON MAY 25 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 324 AM CDT MON MAY 25 2015

VERY CHALLENGING AND PROBLEMATIC FORECAST IN THE NEAR TERM TODAY AND
TONIGHT. FOR STARTERS WE HAVE FOG...SOME OF IT RATHER DENSE...IN THE
EASTERN SECTIONS OF SOUTHWEST MN AND ALSO IN GREGORY COUNTY.
BASICALLY THE FOG IN SOUTHWEST MN IS DUE TO STRATUS ON THE GROUND
FROM THEIR HIGHER TERRAIN...WHILE THE FOG IN SOUTH CENTRAL SD WAS
ORIGINALLY AIDED BY AN UPSLOPE FLOW WHICH IS NOW BEGINNING TO WANE.
BUT ACCOUNTED FOR THESE AREAS BY JUST GOING WIDESPREAD FOG INTO MID
MORNING...WITH ONLY PATCHY OR AREAS OF FOG ELSEWHERE. WITH A DRY MID
LEVEL LAYER...THERE COULD BE SOME PATCHY DRIZZLE ALMOST ANYWHERE
THROUGH MID MORNING. BUT FOR NOW DECIDED TO LEAVE OUT AS THE
FORECAST ALREADY HAS A LIGHT SHOWER AND FOG MENTION AND DID NOT WANT
TO CLUTTER UP THE GRIDS AND WORDING WITH TOO MANY ELEMENTS.

OTHERWISE...OUR EVER PRESENT LARGE UPPER LOW IS CENTERED WHERE THE
NEB PANHANDLE...EASTERN WY AND NORTHEAST CO MEET...WITH A SECONDARY
CIRCULTION CLOSE TO NORTHEAST SD. THIS SECOND CIRCULATION IS CAUSING
QUITE A BIT OF LIGHT SHOWER ACTIVITY AT THIS TIME PRIMARILY NORTH OF
OUR FORECAST AREA. SO ALL TOLD FOR THE MORNING HOURS...REALLY NOT
EXPECTING A LOT TO HAPPEN IN OUR FORECAST AREA AS WE ARE BETWEEN
SHORT WAVES. A SURFACE AND LOW LEVEL WIND SHIFT OOZES DOWN IN OUR
NORTHERN AND WESTERN ZONES THIS AFTERNOON BEHIND THE WEAK NORTHERN
UPPER LOW. THIS WIND SHIFT COULD PROVIDE A FOCUS FOR THUNDERTORM
DEVELOPMENT THROUGHOUT OUR SOUTHEAST ZONES LATE THIS AFTERNOON AND
EARLY EVENING BEFORE DISSIPATING. THEREFORE KEPT LIKELY POPS GOING
GENERALLY ALONG AND SOUTH OF A TYNDALL SD...TO IOWA GREAT LAKES LINE
DURING THOSE HOURS. SOME OF THE CELLS COULD BE MARGINALLY SEVERE...
ESPECIALLY FROM SIOUX CITY TO SPENCER AND SOUTHWARD...WITH NAM ML
CAPE VALUES BETWEEN A 1000 TO 2000 J/KG AND 925MB LIFTED INDEX
VALUES -4 TO -7C. WIND SHEAR IS NOT TOO IMPRESSIVE...ESPECIALLY IN
THE LOW LEVELS...BUT 0-3KM BULK SHEAR VECTORS ARE AVERAGING 30 TO 40
KNOTS IN THAT AREA COUPLED WITH 0-3KM HELICITY VALUES OF 100 TO 120.

TONIGHT...THE UPPER LOW OPENS UP AND MOVES INTO SOUTHERN NEB AND KS.
A GENERAL DRYING TREND WILL TAKE PLACE FROM NORTH TO SOUTH WITH ONLY
SMALL POPS LINGERING AFTER THE EVENING HOURS GENERALLY ALONG AND
EAST OF A YANKTON...TO SIOUX FALLS TO MARSHALL MN LINE. BUT HONESTLY
FROM 06Z TO 12Z TUESDAY THERE WILL LIKELY BE VERY LITTLE GOING ON IN
OUR FORECAST AREA EXCEPT FOR A FEW LIGHT SHOWERS IN THOSE AREAS.
CLOUD COVER COULD STUBBORNLY HANG ON EVEN IN OUR NORTHWEST ZONES AS
THE VARIOUS MODELS ARE SHOWING STRATUS. WITH THE LOW LEVEL AIR
FAIRLY DEAD...THIS COULD CERTAINLY BE A POSSIBILITY. THEREFORE KEPT
LOWS ON THE MILD SIDE...WARMER THAN MANY CONSENSUS READINGS.


.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 324 AM CDT MON MAY 25 2015

COMPLICATED AND SOMEWHAT MURKY FORECAST CONTINUES INTO THE EXTENDED
WITH SUBTLE MODEL DIFFERENCES LEADING TO FAIRLY SUBSTANTIAL CHANGES
IN THE FORECAST.  OVERALL...APPEARS TO BE A FAIRLY ACTIVLE PERIOD
WITH UPPER LEVEL LOW SHIFTING TO THE EAST AND A SECOND SYSTEM
WORKING INTO THE WESTERN US.

ON TUESDAY...COLD FRONT ASSOCIATED WITH THE VACATING SYSTEMS MOVES
ACROSS THE EASTERN CWA.  MODELS HAVE SLOWED THE PROGRESSION OF THE
FRONT. FOCUS FOR PRECIP IS MAINLY ALONG AND AHEAD OF THE FRONT...AND
HAVE CONCENTRATED POPS ACROSS NORTHWEST IOWA INTO FAR SOUTHWEST
MINNESOTA. TALL THIN CAPE PROFILES LEADING TOWARDS EFFECTIVE
HYDROMETOR DEVELOPMENT AS OPPOSED TO ANY SEVERE WEATHER POTENTIAL.

TUESDAY NIGHT INTO WEDNESDAY APPEAR TO BE FAIRLY QUIET WITH A
SURFACE RIDGE MOVING ACROSS THE AREA.

BY WEDNESDAY NIGHT...TROUGH TO THE WEST STARTS TO APPROACH AS LOW
LEVEL JET DEVELOPS ACROSS THE PLAINS LEADING TO THUNDERSTORM
POTENTIAL ACROSS CENTRAL SOUTH DAKOTA. THIS THREAT CONTINUES INTO
THURSDAY AND FRIDAY AHEAD OF A COLD FRONT WORKING SOUTH.  MODEL
DISCREPANCIES CONTINUE...WITH THE GFS STALLING THE FRONT ACROSS THE
AREA...WHILE THE ECMWF SHOWING VERY STRONG FRONT THAT WOULD RESULT
IN WELL BELOW NORMAL TEMPERATURES FOR THE WEEKEND.  FOR
NOW...TRENDING LOWER WITH TEMPERATURES ACROSS THE NORTH....WHILE
WHAT TO DO WITH TEMPS FURTHER SOUTH IS MORE UNCERTAIN.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1035 PM CDT SUN MAY 24 2015

CEILINGS WILL CONTINUE TO DROP OVERNIGHT...ALREADY AT IFR LVLS IN
SOME LOCATIONS...SHOULD FALL INTO LIFR THROUGH DAYBREAK. MAY SEE A
BIT MORE FOG/DRIZZLE DEVELOPMENT OVERNIGHT. FOR MONDAY...AGAIN
EXPECTING SLOW IMPROVEMENT THROUGH THE MORNING AS A WARM FRONT
TRIES TO LIFT NORTH. FEEL GFS/RAP MAY BE MOST REPRESENTATIVE OF
CONDITIONS...SUGGESTING PRECIP MAY TRY TO SLIDE INTO THE AREA
EARLY IN THE AFTERNOON...WITH CONVECTION BUILDING EAST THROUGH THE
AFTERNOON. GIVEN THE COMPLEX NATURE OF THE TAFS IN THE FIRST 12
HOURS...AND UNCERTAINTY WITH WHERE CONVECTION WILL ALIGN...WILL
CONTINUE WITH VCTS.


&&

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

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.