National Weather Service Raw Text Product

219 
FXUS63 KFSD 230248
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
948 PM CDT TUE APR 22 2014

.UPDATE...
ISSUED AT 947 PM CDT TUE APR 22 2014

THE CURRENT FORECAST IS RUNNING ALONG WELL...AND GIVEN THE NATURE
OF THE CURRENT AND UPSTREAM AIRMASS ACROSS THE AREA...EXPECT THAT
TO CONTINUE OVERNIGHT. VERY LOW LEVELS...PER KOAX/KTOP/KLBF...ARE
EXTREMELY DRY AND THE ELEVATED THETA E ADVECTION ABOVE 700 HPA HAS
HARDLY BEEN ABLE TO GENERATE BUT A FEW SPRINKLES. TRAJECTORY DOES
NOT SUGGEST A GREAT CHANGE IN LOWER LEVELS THROUGH MUCH OF THE
NIGHT...BUT WILL CONTINUE TO SEE INCREASE IN THE 700-500 HPA LAPSE
RATE AND WEAK DISTURBANCE IN THE WESTERN PLAINS WORKING INTO THE
RIDGE AXIS ACROSS THE AREA OVERNIGHT. ONGOING IDEA OF A LOW CHANCE
POP WORKING INTO THE WEST TOWARD MIDNIGHT...AND ENHANCING JUST A
BIT BY LATE TONIGHT AND TOMORROW MORNING TOWARD THE EAST SEEMS ON
TRACK. THE ONLY CHANGE OF SUBSTANCE WAS TO INCREASE WIND GUSTS
DURING THE MORNING AND MIDDAY HOURS...AS WINDS OF 35 TO 40 KNOTS 
WILL BE WELL WITHIN ANY MIXED LAYER AND WILL NOT TAKE LONG TO
REALIZE ONE DIURNAL MIXING OCCURS.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 329 PM CDT TUE APR 22 2014

RETURN FLOW GRADUALLY INCREASING FROM WEST TO EAST ACROSS THE AREA 
LATE THIS AFTERNOON AHEAD OF AN APPROACHING TROUGH.  AS OF 
20Z...TROUGH WAS OVER THE PACIFIC NORTHWEST BUT IS EXPECTED TO 
RAPIDLY SHIFT EAST THROUGH THE OVERNIGHT.  850 -700 MB THETA-E 
ADVECTION IS STRONG ENOUGH THROUGH THE OVERNIGHT TO POTENTIALLY 
CREATE A FEW SCATTERED SHOWERS/ISOLATED THUNDER THROUGH THE 
OVERNIGHT.  THE STRONG THETA-E ADVECTION SHIFTS EAST THROUGH THE 
MORNING HOURS ON WEDNESDAY.

VERY WINDY DAY EXPECTED AHEAD OF THE APPROACHING LOW.  925 HPA WINDS 
START OFF AROUND 40 KNOTS AND GRADUALLY DECREASE THROUGHOUT THE DAY 
AS TROUGH APPROACHES FROM THE WEST.  WITH STRONG WINDS ALOFT AND 
MIXING...SHOULD SEE ADVISORY CONDITIONS ACROSS MUCH OF THE AREA AND 
HAVE ISSUED A WIND ADVISORY ACROSS THE AREA.  TOUGH CALL IN TERMS OF 
SEVERE WEATHER AS SYNOPTIC WARM FRONT VERY BRIEFLY NOSES INTO THE 
FORECAST AREA.  MAINLY ELEVATED INSTABILITY AHEAD OF THE APPROACHING 
LOW AND INSTABILITY REMAINS ABOVE MUCH OF THE EFFECTIVE SHEAR.  
THEREFORE...MAINLY EXPECTING STORMS TO REMAIN BELOW SEVERE LIMITS 
BUT COULD HAVE AN ISOLATED HAILER APPROACH THE LOW END OF SEVERE 
LIMITS IN THE MISSOURI RIVER LATE WEDNESDAY AFTERNOON. 

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 329 PM CDT TUE APR 22 2014

THE THREAT FOR LOW END SEVERE WILL CONTINUE INTO EARLY WEDNESDAY 
EVENING OVER MAINLY THE SOUTHEAST QUARTER OF THE CWA...WITH ELEVATED 
HAILERS THE MAIN CONCERN. STILL EXPECTING A FAIRLY BROAD AREA OF 
RAINFALL HOWEVER WITH A DECREASING THREAT FOR THUNDER TO THE WEST. 
THE BETTER FORCING SHIFTS EAST THROUGH THE NIGHT WITH MOST OF THE 
PRECIPITATION EAST OF THE I-29 CORRIDOR BY LATE NIGHT. THE UPPER 
LEVEL SUPPORT WILL GRADUALLY ROTATE TO THE NORTHEAST WHICH WILL 
LEAVE A SMALL THREAT FOR SHOWERS AND ISOLATED THUNDERSTORMS OVER THE 
NORTHEAST THIRD OF THE CWA. THE MAIN THREAT COULD BE DURING THURSDAY 
AFTERNOON AS WE HEAT OUT AND A LITTLE BIT OF SURFACE BASED CAPE 
DEVELOPS...ABOUT 500 J/KG OR LESS. WITH A VERY LOW FREEZING LEVEL 
SOME SMALL HAIL WILL BE POSSIBLE. 

THE OTHER CONCERN ON THURSDAY WILL BE FIRE WEATHER. VERY DEEP MIXING 
WILL LEAD TO WINDS LIKELY GUSTING TO AROUND 35 TO 40 MPH AND SURFACE 
RELATIVE HUMIDITY VALUES IN THE TEENS TO LOWER 20S...SO IF THE 
FORECAST HOLDS RED FLAG CONDITIONS WILL BE VERY POSSIBLE.

ON FRIDAY THE MODELS HAVE COME AROUND TO A SLIGHTLY WARMER AND MORE 
MIXED DAY WITH THE 12Z GFS QUITE A BIT COLDER THAN THE NAM/ECMWF/GEM 
OUTPUT. SO RAISED HIGHS A BIT MORE INTO THE UPPER 50S TO UPPER 60S. 
ANOTHER FAIRLY BREEZY DAY BUT FOR NOW IT LOOKS LIKE SURFACE RELATIVE 
HUMIDITY VALUES WILL BE A BIT BELOW WHATS NEEDED FOR RED FLAG 
CONDITIONS. 

IN THE OUTER PERIODS(SATURDAY THROUGH TUESDAY)...MODELS INCONSISTENT 
AND DIVERGING A BIT SO CONFIDENCE NOT REAL STRONG...AT LEAST ON SOME 
OF THE DETAILS. ONE THINGS SEEMS ALMOST FOR CERTAIN AND THAT IS FOR 
BELOW NORMAL TEMPERATURES...BUT AT LEAST FOR THE WEEKEND EVEN THAT 
IS NOT COMPLETELY GUARANTEED. THE LATEST ECMWF HAS COME IN MUCH 
WARMER...FARTHER NORTH WITH THE WARM FRONT...THAN EITHER THE GFS OR 
GEM. AT THIS TIME SIDING WITH THE GFS/GEM OUTPUT WHICH KEEPS THE 
DEVELOP UPPER LEVEL LOW A LITTLE FARTHER SOUTH WHICH SHOULD IN TURN 
KEEP THE WARMER AIR LOCKED UP TO THE SOUTH AS WELL. BY MONDAY INTO 
TUESDAY COOLER AIR SETTLES IN ON ALL THE MODELS SO A BIT MORE 
CONFIDENT FOR COLDER CONDITIONS THESE DAYS. STILL A VERY GOOD CHANCE 
FOR RAIN SUNDAY INTO MONDAY...BUT WILL NEED TO SEE IF THE MODELS CAN 
BECOME A BIT MORE CONSISTENT BEFORE BRINGING IN HIGHER 
PROBABILITIES.     

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 640 PM CDT TUE APR 22 2014

LARGEST AVIATION ISSUE OVER THE NEXT 24 HOURS WILL BE THE VERY 
STRONG WINDS. A CONTINUED INCREASE IN THE GRADIENT IS EXPECTED
OVERNIGHT...AND WILL GET WINDS STRONG ENOUGH ALOFT TO WARRANT SOME
NEAR 40 KNOT GUSTS AS EARLY AS 14-15Z. AT THIS TIME...WILL LIKELY
END UP WITH SURFACE WINDS STRONG ENOUGH TO AVOID MENTION OF LOW
LEVEL WIND SHEAR PRIOR TO MIXING OUT NEAR SURFACE INVERSION BY
MID MORNING. WHILE DO ACKNOWLEDGE THE FACT THAT COULD BE SOME
SHOWERS AND ISOLATED THUNDER BY LATER TONIGHT AND EARLY MORNING...
THEN AGAIN TOWARD LATER AFTERNOON FOR KHON...THE PROBABILITY AT 
THIS TIME WILL KEEP FROM MENTIONING WITH LIKELIHOOD THAT ANY
SHOWERS WOULD ALSO CONTAIN VFR CEILINGS AND VISIBILITIES.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY FROM 10 AM TO 8 PM CDT WEDNESDAY FOR SDZ040-055-
     056-062-066-067-070-071.

     WIND ADVISORY FROM 10 AM TO 4 PM CDT WEDNESDAY FOR SDZ038-039-
     050-052>054-057>061-063>065-068-069.

MN...WIND ADVISORY FROM 10 AM TO 8 PM CDT WEDNESDAY FOR MNZ071-072-
     080-081-089-090-097-098.

IA...WIND ADVISORY FROM 10 AM TO 8 PM CDT WEDNESDAY FOR IAZ001>003-
     012>014-020>022-031-032.

NE...WIND ADVISORY FROM 10 AM TO 8 PM CDT WEDNESDAY FOR NEZ013-014.

&&

$$

UPDATE...CHAPMAN
SHORT TERM...
LONG TERM...08
AVIATION...CHAPMAN/SCHUMACHER