Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 231143
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
643 AM CDT WED APR 23 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 450 AM CDT WED APR 23 2014

CURRENT RADAR VERY EARLY THIS MORNING SHOWING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS DEVELOPING THROUGH THE CENTRAL PORTIONS OF
THE CWA...THOUGH NOT THINKING MUCH RAIN IS REACHING THE GROUND WITH
CLOUD BASES RUNNING FROM AROUND 7 TO 10 KFT. THIS CONVECTION LOOKS
TO BE ALIGNED WELL WITH MODEL 700 MB THETA E ADVECTION...AND HI RES
MODELS SHOWING THIS SHIFTING OFF TO THE EAST THROUGH THE MORNING
HOURS. ALSO SEEING CONVECTION DEVELOP THROUGH EAST CENTRAL NEBRASKA
OUT AHEAD OF A SHORTWAVE TRACKING OUT OF THE WESTERN PORTION OF THAT
STATE. INDICATIONS ARE THAT THIS SCATTERED CONVECTION WILL LIFT
ACROSS NORTHWEST IOWA DURING THE EARLY MORNING HOURS...THEN
EXPECTING AN OVERALL BREAK IN CONVECTIVE ACTIVITY THROUGH THE LATE
MORNING AND EARLY AFTERNOON...BEFORE REDEVELOPMENT TAKES PLACE IN
THE LATE AFTERNOON...FOCUSED THROUGH SOUTH CENTRAL SOUTH
DAKOTA/SOUTHERN JAMES RIVER VALLEY WITH THE APPROACH OF AN UPPER
LEVEL TROUGH AND SURFACE FRONTAL BOUNDARY. CONVECTION WILL THEN RAMP
UP THROUGH THE LOWER MISSOURI RIVER VALLEY THIS EVENING...THEN
TRANSLATE ACROSS THE EASTERN PORTIONS OF THE CWA OVERNIGHT. THIS
BEING FUELED BY STRONG MOISTURE TRANSPORT ON A 50 KT LOW LEVEL JET
AND STRONG UPPER LEVEL DIVERGENCE/LIFT THANKS TO AN UPPER LEVEL JET
MAX STREAMING THROUGH THE WESTERN/CENTRAL PART OF THE STATE. COULD
SEE SOME DECENT RAINFALL AMOUNTS ACROSS PORTIONS OF NORTHWEST IOWA
WITH THIS ACTIVITY. IN TERMS OF SEVERE WEATHER...THINK THAT IT WILL
BE ISOLATED AT BEST IN THE LATE AFTERNOON OR EARLY EVENING THROUGH
THE LOWER MISSOURI RIVER CORRIDOR...WITH BUFKIT SOUNDING ANALYSIS
SHOWING MUCAPE VALUES ONLY IN THE RANGE OF 500 TO 700 J/KG AND
EFFECTIVE SHEAR OF AROUND 25 KT.

OTHERWISE...IT WILL BE VERY WINDY TODAY WITH A TIGHT GRADIENT AND
WINDS AT THE TOP OF THE MIXED LAYER AROUND 40 KT. IN LIGHT OF
THAT...WAS APPROPRIATE TO KEEP THE WIND ADVISORY GOING FROM 15Z
THROUGH 00Z...STAGGERED FROM WEST TO EAST. THERE WILL BE A WIDE
RANGE OF TEMPERATURES ACROSS THE AREA TODAY...TOPPING OUT ONLY
AROUND 60 THROUGH THE NORTHEASTERN THIRD OF THE CWA WHERE SKIES
SHOULD REMAIN CLOUDY THROUGH THE DAY...TO AS WARM AS THE UPPER 70S
OVER SOUTH CENTRAL SOUTH DAKOTA WITH A WARM FRONT NUDGING UP INTO
THAT AREA.

THE SURFACE LOW/ASSOCIATED FRONTAL BOUNDARY WILL TRACK ACROSS THE
REGION TONIGHT...WITH CONVECTION TAPERING OFF FROM WEST TO EAST LATE
AT NIGHT AND WINDS SLOWLY DYING DOWN. LOWS LOOK TO BE IN THE 40S
ACROSS THE ENTIRE AREA.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 450 AM CDT WED APR 23 2014

IMMEDIATE CONCERN IN THE LONGER RANGE WILL BE FIRE DANGER AND
POTENTIAL FOR RED FLAG CONDITIONS ACROSS WESTERN PORTIONS OF THE
AREA. SHOULD SEE SOME LINGERING SHOWERS/ISOLATED THUNDERSTORMS
ACROSS OUR EAST AT THE START OF THE DAY...BUT EXPECT THIS TO MOVE
OUT OF OUR AREA BY LATE MORNING/MIDDAY...WITH STRONG MIXING WITHIN
DEEP WESTERLY FLOW BEHIND THE SYSTEM. COOLER MID LEVEL AIR LINGERS
ACROSS THE FAR NORTHEAST CWA THROUGH THE AFTERNOON...RESULTING IN
SOME WEAK INSTABILITY DUE TO THE STEEP MID LEVEL LAPSE RATES. WILL
HANG ONTO A CHANCE OF SHOWERS/ISOLATED THUNDERSTORMS NORTHEAST OF
KBKX-KMJQ...THOUGH MAINLY HEATING DRIVEN SO EXPECT ANY ACTIVITY TO
DIMINISH BY EARLY EVENING.

FORECAST SOUNDINGS ACROSS THE SOUTHWEST HALF OF THE CWA INDICATE
POTENTIAL FOR LOWER DEW POINTS MIXING TO THE SURFACE THAN EVEN RAW
MODEL VALUES SUGGEST...AND THUS HAVE LOWERED DEW POINT VALUES A BIT
FURTHER FROM PREVIOUS FORECAST...GENERALLY BOTTOMING OUT FROM LOWER
20S WEST TO AROUND 30 EAST. THIS ALONG WITH WELL-MIXED TEMPERATURES
IN THE 60S YIELDS A LARGE AREA OF MINIMUM HUMIDITY VALUES IN THE 15
TO 20 PERCENT RANGE FROM SOUTH CENTRAL SD...THROUGH THE JAMES RIVER
VALLEY AND INTO EXTREME NORTHEAST NEBRASKA. HELPING TO MIX DOWN THE
DRY AIR WILL BE WEST WINDS AROUND 25 MPH WITH GUSTS TO 35 MPH. THIS
PATTERN HAS BEEN FAIRLY CONSISTENT FOR THE PAST COUPLE OF DAYS...SO
OPTED TO ISSUE A FIRE WEATHER WATCH FOR THE ABOVE MENTIONED AREAS
THURSDAY AFTERNOON. NORTHEAST AREAS SHOULD SEE HIGHER HUMIDITY AS
WELL AS SLIGHTLY LOWER WIND SPEEDS...THOUGH FIRE DANGER WILL STILL
BE VERY HIGH.

FRIDAY CONTINUES TO LOOK WARMER AS UPPER LOW TRACKS EAST INTO THE
GREAT LAKES REGION. STILL SOME DISCREPANCY REGARDING STRENGTH OF A
TRAILING WAVE AND WHETHER IT WILL DROP A BACK DOOR COOL FRONT INTO
OUR NORTHERN CWA SOME TIME ON FRIDAY. NAM/ECMWF HOLD THE COLD AIR
WILL NORTHEAST OF THE AREA...WHILE GFS CONTINUES TO DROP SLIGHTLY
COOLER AIR INTO THE REGION...AND GEM SOMEWHERE BETWEEN THE COOL GFS
AND WARM NAM/ECMWF. THAT SAID...EVEN COOLER GFS IS QUITE MILD WITH
HIGHS IN THE UPPER 60S INTO THE MISSOURI RIVER VALLEY...AND THUS
FELT COMFORTABLE BUMPING TEMPS UP A FEW MORE DEGREES FROM PREVIOUS
FORECAST...WITH HIGHS FROM THE LOWER 60S NORTHEAST TO LOWER 70S
SOUTH. DO NOT EXPECT HUMIDITY TO BE AS LOW...NOR WINDS TO BE AS
STRONG AS THURSDAY THOUGH...WITH SLACK GRADIENT ACROSS THE REGION...
SO FIRE DANGER SHOULD BE KEPT IN CHECK.

LONGER RANGE SATURDAY THROUGH TUESDAY IS A PERIOD OF RELATIVELY LOW
CONFIDENCE AS MODELS NOT SHOWING GREAT AGREEMENT REGARDING TRACK OF
STRONG UPPER TROUGH AND ASSOCIATED SURFACE LOW AS IT MOVES INTO THE
PLAINS THROUGHOUT THE WEEKEND. FEEL FAIRLY SURE THAT PRECIPITATION
CHANCES WILL INCREASE AS THE WEEKEND PROGRESSES. BUMPED POPS INTO
LIKELY RANGE FOR AT LEAST PARTS OF THE AREA SATURDAY NIGHT THROUGH
SUNDAY NIGHT...AS MOST LOCATIONS MORE LIKELY TO SEE AT LEAST SOME
LIGHT PRECIPITATION CHANCES. GREATER UNCERTAINTY COMES WITH REGARD
TO STRENGTH OF LOW LEVEL WARMING...AS NORTHERN TRACK OF ECMWF WOULD
BRING MUCH WARMER AIR INTO SOUTHERN PARTS OF THE REGION THROUGH THE
WEEKEND...ALONG WITH A GREATER POTENTIAL FOR THUNDERSTORMS. ON THE
OTHER HAND...GFS/GEM TRACK THE SYSTEM FARTHER SOUTH THROUGH THE
PLAINS WITH COOLER AND MORE STABLE AIR LOCKED IN PLACE AS FAR SOUTH
AS THE MISSOURI VALLEY AND FAR NORTHERN NEBRASKA. EVEN THE COOLER
MODELS ARE WARMER THAN WAS INDICATED A FEW DAYS AGO...BUT STILL
SEEING SOME 10-20 DEGREE DIFFERENCES IN FORECAST HIGH TEMPERATURES
FOR SOME LOCATIONS BETWEEN MODELS FOR BOTH SATURDAY AND SUNDAY. NOT
ENOUGH CONFIDENCE IN ANY ONE SOLUTION TO DEVIATE TOO FAR FROM MODEL
CONSENSUS...THOUGH DID GENERALLY MOVE IN A WARMER DIRECTION FROM THE
PREVIOUS FORECAST. WITH TREND TOWARD WARMER...ALSO CHOSE TO INCLUDE
MENTION OF THUNDER ACROSS THE SOUTHERN HALF OF THE AREA WITH THE
INCREASING PRECIP CHANCES LATE IN THE WEEKEND.

MONDAY AND TUESDAY STILL LOOK TO BE ON THE COOLER SIDE...THOUGH
AGAIN MODELS DISAGREE ON JUST HOW COLD...OR HOW LONG THREAT OF
PRECIP WILL LINGER ACROSS THE AREA. WITH CONFIDENCE LOW...MADE
LITTLE CHANGE TO GIVEN CONSENSUS GRIDS IN THESE OUTER PERIODS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 638 AM CDT WED APR 23 2014

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS PORTIONS OF
THE AREA THIS MORNING WILL DIMINISH AFTER 15Z. OTHERWISE...STRONG
SOUTHEASTERLY WINDS GUSTING TO NEAR 35 KTS AT TIMES WILL CONTINUE
INTO THE LATE AFTERNOON...BEFORE DROPPING OFF EARLY THIS EVENING.
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO REDEVELOP THROUGH THE
LOWER MISSOURI RIVER VALLEY LATE THIS AFTERNOON...THEN EXPAND TO
THE NORTH AND EAST DURING THE OVERNIGHT. CONFIDENCE THAT THIS
ACTIVITY WILL AFFECT KHON IS LOW...SO DID NOT INCLUDE IT IN THE
TAF. WHILE EXPECTING MAINLY VFR CONDITIONS WITH THE
SHOWERS/THUNDERSTORMS...CANNOT RULE OUT BRIEF LOCALIZED MVFR
CONDITIONS IN A HEAVIER STORM.

&&

.FIRE WEATHER...
ISSUED AT 450 AM CDT WED APR 23 2014

CONCERNS OVER POTENTIAL FOR CRITICAL FIRE WEATHER ACROSS PORTIONS OF
THE AREA ARE INCREASING FOR THURSDAY AFTERNOON. STRONG MIXING WITHIN
DRYING AIR MASS BEHIND DEPARTING LOW PRESSURE SYSTEM EARLY THURSDAY
IS EXPECTED TO YIELD GUSTY WESTERLY FLOW IN THE 25 TO 35 MPH RANGE...
ALONG WITH VERY LOW HUMIDITY LEVELS OF 15 TO 20 PERCENT FROM THE
LOWER BRULE REGION...THROUGH THE JAMES RIVER VALLEY...AND INTO THE
LOWER BIG SIOUX RIVER VALLEY AND EXTREME NORTHEAST NEBRASKA. GIVEN
THE CONSISTENCY WHICH HAS BEEN SEEN THE PAST FEW DAYS INDICATING THIS
EXPECTED PATTERN...HAVE ISSUED A FIRE WEATHER WATCH FOR FIRE ZONES
255...256...258 IN SOUTH DAKOTA...AS WELL AS NEBRASKA FIRE ZONE 249.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
     EVENING FOR SDZ255-256-258.

     WIND ADVISORY FROM 10 AM THIS MORNING TO 8 PM CDT THIS EVENING
     FOR SDZ040-055-056-062-066-067-070-071.

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

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

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

NE...FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
     EVENING FOR NEZ249.

     WIND ADVISORY FROM 10 AM THIS MORNING TO 8 PM CDT THIS EVENING
     FOR NEZ013-014.

&&

$$

SHORT TERM...JM
LONG TERM...JH
AVIATION...JM
FIRE WEATHER...JH






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