Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
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 300854
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
354 AM CDT TUE JUN 30 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 353 AM CDT TUE JUN 30 2015

NORTHWEST FLOW ALOFT REMAINS IN PLACE THROUGH THE DAY...WITH AREAS
WEST OF INTERSTATE 29 TURNING JUST A BIT MORE TO A WEST NORTHWEST
DIRECTION. EARLY THIS MORNING THIS SUBTLE SHIFT IN THE MID AND UPPER
LEVEL WIND FIELD WAS WORKING WITH THE LITTLE BIT OF AVAILABLE
ELEVATED INSTABILITY TO ALLOW A FEW SHOWERS AND THUNDERSTORMS TO
DEVELOP ALONG AND WEST OF THE JAMES RIVER VALLEY. THE MAIN QUESTION
THEN BECOMES HOW FAR WEST CAN THIS WEAK BOUNDARY SHIFT AND HOW MUCH
INSTABILITY WILL BE LEFT TO WORK WITH. FOR NOW LEANING TOWARDS NOT
TOO FAR AND NOT VERY MUCH...SO WILL MAINTAIN 20 POPS NEAR THE
INTERSTATE 29 CORRIDOR...WITH HIGHER POPS THROUGH THE DAY TO THE
WEST. SUSPECT THAT THERE SHOULD BE A SLIGHT DOWNWARD TREND IN
ACTIVITY BY MID MORNING BUT WILL NEED TO KEEP SOME POPS IN THE
WESTERN CWA THROUGH THE DAY. BY LATE AFTERNOON INTO THE EVENING
HOURS THE THREAT FOR THUNDERSTORMS WILL BE HIGHEST ALONG THE
MISSOURI RIVER INTO NEBRASKA AS THE LOWER LEVEL INSTABILITY MAY
ACTIVATE A FEW THUNDERSTORMS. AT THIS TIME NOT ANTICIPATING ANY
SEVERE THUNDERSTORMS IN THE AREA TODAY OR TONIGHT.

ALSO OF INTEREST WILL BE THE FAIRLY THICK LAYER OF SMOKE. LOWERED
HIGHS A DEGREE OR TWO IN THE EAST TO ACCOUNT FOR THE POTENTIAL THAT
THE SMOKE COULD LINGER THROUGH THE DAY AS THE NORTHWEST WINDS REMAIN
IN PLACE ALL DAY. LOWS TONIGHT WILL BE MILD...IN THE UPPER 50S TO
LOWER 60S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 353 AM CDT TUE JUN 30 2015

SOME QUESTION AS TO HOW MUCH OF THE OVERNIGHT CONVECTIVE DEVELOPMENT
WILL REMAIN BY WEDNESDAY MORNING...AS LIFT FORCING WITH MAIN UPPER
WAVE WILL BE QUICKLY EXITING THE EASTERN HALF OF THE CWA...AND
IMPACT OF THE MORE FAVORED DEVELOPMENT ALONG THE SOUTHERN CWA
SHIFTING SOUTHWARD TOWARD INSTABILITY/LOW LEVEL BAROCLINICITY WILL
ALSO PUT A DRAIN ON COVERAGE ALONG THE LINGERING MID LEVEL BOUNDARY.
GENERAL LOW LEVEL EASTERLIES WILL KEEP THE OVERALL PROFILE TOWARD
THE STABLE/NEUTRAL SIDE...WITH JUST HINTS OF MARGINAL INSTABILITY AT
TIMES. ALMOST A CRIME TO KEEP THUNDER AT AS HIGH A LEVEL AS THE
PRECIPITATION THREAT...BUT WITH SUCH LOW POPS THROUGH THE DAY

WILL START WITH A BIT HIGHER RAIN CHANCES IN THE EARLY MORNING ALONG
THE FAR SOUTH/EAST...BUT GRADUALLY DROP BACK AS UPPER FORCING
BECOMES MORE HOSTILE...AT LEAST FOR A TIME THROUGH THE LATER MORNING
AND EARLY AFTERNOON. REMAINS JUST A HINT OF DIV Q AXIS ACROSS THE
NORTHEAST HALF THROUGH THE DAY...AND JUST A TOUCH COOLER ALOFT AS
WELL.  BY LATE DAY...LEADING EDGE OF FORCING FROM NEXT IMPULSE WILL
BE TANTALIZINGLY CLOSE TO THE NORTHERN CWA...AND WILL AGAIN INCREASE
PRECIPITATION THREAT INTO CHANCE RANGE.

MUCH STRONGER SYSTEM WILL BE PUSHING SOUTHEAST IN THE NORTHWEST FLOW
BY LATER WEDNESDAY NIGHT AND THROUGH THE DAY THURSDAY. FORCING WILL
ACT TO REFOCUS PRECIPITATION THREAT TO THE NORTHWEST DURING THE
EVENING...WITH SOUTHEASTERLY FLOW AT LOWER LEVELS HELPING TO
DRY/STABILIZE THE FAR EAST/SOUTHEASTERN CWA FOR A TIME OVERNIGHT. A
BIT MORE ELEVATED INSTABILITY NOTED BY LATE NIGHT AND
THURSDAY...WHICH WILL DRIVE MUCAPE TOWARD 500-700 J/KG BY EARLY
THURSDAY...SIGNALING A BETTER CHANCE FOR THUNDER COVERAGE.
HOWEVER...NARROW CAPE PROFILE AND LIMITED SHEAR WILL KEEP VERY LOW
CHANCE FOR EVEN MARGINALLY SEVERE WEATHER. WILL LIKELY HAVE LITTLE
OPPORTUNITY TO BUILD MEANINGFUL SURFACE BASED INSTABILITY WITH
ABUNDANT CLOUDS AND FAIRLY WIDESPREAD PRECIPITATION THROUGH THE DAY
THURSDAY. BEST CHANCE WILL BE ON THE EASTERN FRINGE OF THE PRECIP
SHIELD ACROSS SW MN/NW IA.  HIGHS THURSDAY WILL REFLECT THE LACK OF
DIABATIC INFLUENCE WITH 70S.

UPPER WAVE WILL CONTINUE TO PLOD ALONG TO THE SOUTHEAST THURSDAY
NIGHT AND FRIDAY. WHILE PROGRESSING NICELY AT MID AND UPPER
LEVELS... LOWER LEVELS INDICATIVE OF LEAVING BEHIND PERSISTENT
AND WEAKENING EASTERLY FLOW... AND THE WORRISOME THREAT OF STRATUS.
HAVE PUT IN A LITTLE LATE NIGHT FOG THURSDAY NIGHT FOR NOW...AND
COULD ALSO BE A MORE SIGNIFICANT THREAT ON FRIDAY NIGHT/SATURDAY
MORNING AS WELL AS FLOW BEGINS A TRANSITION TO SOUTHERLY. WILL HAVE
TO WATCH OUT FOR STRATUS...AS WOULD HAVE A POTENTIAL IMPACT ON HIGHS
FOR FRIDAY. IF CAN SNEAK IN A LITTLE SUN...WOULD CERTAINLY BE A
SOMEWHAT SELF DESTRUCTIVE INSOLATION...WITH SOME INDICATION OF SMALL
SURFACE BASED INSTABILITY. HAVE MAINTAINED ISOLATED LEVEL POPS
THROUGH THE DAY FRIDAY TO COVER THIS THREAT.

SHOULD BE THE MOST QUIET IN THE FRIDAY NIGHT THROUGH SATURDAY NIGHT
TIME FRAME WITH WEAK RIDGING ALOFT. THE ONLY FLY IN THE OINTMENT FOR
SATURDAY AT THIS TIME WOULD BE THE LINGERING LOW LEVEL MOISTURE AXIS
AND FACT THAT TEMPS ALOFT REALLY DO NOT WARM A GREAT DEAL...AS NOW A
WEAK WAVE PASSING THROUGH THE MEAN RIDGE ON SATURDAY.  THERE IS A
SMALL THREAT THAT COULD DEVELOP SOME SURFACE BASED INSTABILITY AND
AGAIN BE DEALING WITH A FEW ROGUE SHOWERS/STORMS DURING THE HEATING
PORTIONS OF THE DAY IN THE AFTERNOON AND EARLY EVENING. AT THIS
TIME...TOO LOW A THREAT TO INTRODUCE IN THE FORECAST. OVERALL...A
WARMER AND MORE HUMID DAY WITH INCREASING SOUTHERLY WINDS...AND
HIGHS FROM AROUND 80 TO THE MID 80S.

MODELS CONTINUE TO FLUCTUATE WITH TIMING OF FEATURES SUNDAY INTO
MONDAY...WITH GFS/ECMWF SWAPPING ROLES TONIGHT ON 00Z RUNS. ECMWF IS
NOW A BIT FASTER WITH BOUNDARY ON SUNDAY. TRENDS AND ENSEMBLES WOULD
SUGGEST KEEPING A BIT SLOWER...WHICH BRINGS INTO PLAY A DECENT
WARMER PUSH OUT AHEAD OF BOUNDARY BOTH SURFACE AND ALOFT. SHEAR AND
INSTABILITY MUCH MORE IMPRESSIVE...AND LOOK TO HAVE A STRONG ENOUGH
CAP IN PLACE TO KEEP ACTIVITY TIED TO APPROACH OF BOUNDARY AROUND
LATER DAY. CERTAINLY SUGGESTS A BETTER SEVERE WEATHER THREAT FOR
LATER SUNDAY AND SUNDAY EVENING SOMEWHERE IN THE VICINITY. BOUNDARY
PUSHES SOUTHWARD BY MONDAY...WITH A FAIRLY MIXY DAY OF NORTHWEST
FLOW AND SHOULD BE SEASONABLE...WELL INTO THE 80S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1047 PM CDT MON JUN 29 2015

5-10 SM VISIBILITY EXPECTED THROUGH THE PERIOD. FAIRLY THICK
SMOKE POURING INTO THE REGION UNDER NORTHWEST FLOW ALOFT.
NORTHWEST FLOW IS EXPECTED TO GRADUALLY THIN THROUGH THE DAY...SO
EXPECT SMOKE TO THIN. WITH THAT SAID...CLOUDS WILL BE ON THE
INCREASE WITH A WEAKLY UNSTABLE ATMOSPHERE. COULD SEE A SCATTERED
SHOWER/THUNDERSTORM AS WELL...BUT TIMING IS UNCERTAIN SO LEFT
MENTION OUT OF THE TAF.

&&

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

$$

SHORT TERM...08
LONG TERM...CHAPMAN
AVIATION...



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