Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 101733
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1233 PM CDT WED SEP 10 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 328 AM CDT WED SEP 10 2014

FRONTAL BOUNDARY HAS PUSHED THROUGH ALL BUT THE FAR SOUTHEASTERN
PORTIONS OF THE CWA THIS MORNING.  TEMPERATURES HAVE FALLEN INTO THE
LOWER 50S IN CENTRAL SD...WHILE READINGS CONTINUE TO HOVER NEAR 60
IN THE SE.  WIND SPEEDS WILL CONTINUE TO INCREASE THROUGH DAYBREAK
AS SURFACE PRESSURE GRADIENT TIGHTENS DUE TO CYCLOGENESIS IN EASTERN
IOWA. CURRENT EXPECTATIONS ARE THAT ONGOING SHOWER ACTIVITY WILL
CONTINUE INTO MID MORNING AS ELONGATED VORTICITY MAX PASSES TO THE
EAST. SHOWERS MAY ALSO BE REPLACED BY PERIODS OF DRIZZLE.  IT WILL
TAKE A BIT OF TIME FOR SHOWERS TO COMPLETELY DISSIPATE TODAY AS LOW
LVL WINDS DO NOT TAKE A MORE NORTHERLY TURN UNTIL MID-DAY.
SOUNDINGS BEGIN TO INDICATE INTRUSION OF DRY AIR ALOFT FROM THE
NORTH AFTER 15Z...BUT MORE LIKELY BY 18Z. DUE TO EXTENSIVE CLOUD
COVER AND CONTINUED COLD AIR ADVECTION ALOFT...TEMPERATURES ONCE
THEY BOTTOM OUT THIS MORNING WILL HOLD STEADY THROUGH THE DAY IN THE
LOWER TO MIDDLE 50S.  THESE READINGS WILL LIKELY BE COLD HIGH
TEMPERATURE RECORDS FOR A FEW SITES...WITH OTHERS FALLING JUST SHY
DUE TO THE HIGHEST TEMPERATURE OF THE DAY OCCURRING EARLY THIS
MORNING.

A SECONDARY SHORTWAVE WILL EJECT EASTWARD INTO THE PLAINS LATER THIS
EVENING. A FAIRLY LARGE AREA OF SHOWERS IS ANTICIPATED OVER THE
WESTERN HALF OF SD OVERNIGHT AS ISENTROPIC LIFT ALONG THE 295-300K
SURFACES INCREASES. HOWEVER...MUCH OF THE FORECAST AREA WILL REMAIN
UNDER THE INFLUENCE OF DRY AIR AND WEAK ISENTROPIC DOWNGLIDE...WITH
THE EXCEPTION BEING THE FAR SOUTHWESTERN CWA. WILL SLOWLY INCREASE
POPS AFTER MIDNIGHT IN THE FAR WEST.  TEMPERATURES OVERNIGHT WILL
FALL A DEGREE OR TWO EITHER SIDE OF THE 40 DEGREE MARK.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 328 AM CDT WED SEP 10 2014

ON THURSDAY THE UPPER LEVEL SHORTWAVE CONTINUES TO TRACK OUT OF THE
NORTHERN ROCKIES...WITH MIDLEVEL WARM AIR ADVECTION/ISENTROPIC LIFT
OVERSPREADING THE SOUTHERN PORTIONS OF OUR AREA DURING THE DAY AS
MIDLEVEL FRONTOGENESIS DEVELOPS IN THE VICINITY OF THE WESTERN AND
CENTRAL SOUTH DAKOTA/NEBRASKA BORDER. THIS WILL BRING A CHANCE OF
SHOWERS TO OUR WESTERN CWA...WITH BETTER CHANCES THROUGH THE SOUTH
CENTRAL SOUTH DAKOTA ZONES...DUE TO A PERSISTENT NORTH/NORTHEASTERLY
FLOW IN THE LOW AND MIDLEVELS ADVECTING DRIER AIR INTO THE REGION.
IT WILL BE A COOL DAY WITH CLOUDS...A NORTHERLY SURFACE FLOW...AND
850 MB TEMPERATURES HOVERING JUST EITHER SIDE OF 0 DEGREES
C...YIELDING HIGHS IN THE UPPER 40S IN OUR SOUTHWEST TO MID 50S
THROUGH OUR EAST.

THE UPPER LEVEL WAVE PULLS EASTWARD ON THURSDAY NIGHT...BRINGING
PRECIPITATION CHANCES ACROSS THE CWA...AGAIN MAINLY TO AREAS THROUGH
THE MISSOURI RIVER CORRIDOR WITH THE DRY NORTHERLY FLOW
CONTINUING...AND BETTER LIFT LOCATED THROUGH THAT AREA. ABUNDANT
CLOUD COVER WILL KEEP TEMPERATURES IN CHECK...ALTHOUGH IT WILL STILL
BE QUITE CHILLY WITH LOWS IN THE UPPER 30S TO LOWER 40S.

THE GENERAL TREND FOR FRIDAY WILL BE FOR ANY LINGERING PRECIPITATION
TO END IN OUR SOUTHEAST BY AFTERNOON AS THE SHORTWAVE PULLS
AWAY...WITH DECREASING CLOUDS THROUGH THE DAY. THERMAL PROFILES WILL
SUPPORT HIGHS IN THE 50S. FRIDAY NIGHT WILL BE THE COLDEST NIGHT OF
THE WEEK WITH CLEAR SKIES AND LIGHT WINDS...AND CANNOT RULE OUT
PATCHY FROST IN LOWER LYING AREAS AS LOW TEMPERATURES FALL INTO THE
MID 30S.

SURFACE RIDGING THROUGH THE REGION MOVES EASTWARD FOR THE
WEEKEND...PUTTING OUR AREA BACK INTO A SOUTHERLY FLOW...AND ALLOWING
TEMPERATURES TO WARM A FEW DEGREES EACH DAY...ALBEIT STILL BELOW
NORMAL FOR THIS TIME OF YEAR. IT LOOKS TO BE DRY THROUGH THE PERIOD
WITH HIGHS IN THE 60S AND LOW IN THE 40S. MODEL DIFFERENCES GROW BY
LATER ON SUNDAY INTO THE BEGINNING OF NEXT WEEK WITH REGARD TO A
FRONTAL PASSAGE/AND STRENGTH OF AN UPPER LEVEL TROUGH DIVING INTO
THE REGION DURING THAT TIME FRAME. WITH THAT...THERE ARE TEMPERATURE
DIFFERENCES AMONG THE MODELS...THOUGH CONSENSUS VALUES GIVE HIGHS IN
THE 60S TO LOWER 70S WITH LOWS IN THE 40S. LOOKS TO BE MAINLY DRY IN
THE OUTER EXTENDED PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1229 PM CDT WED SEP 10 2014

MVFR STRATUS WILL SLOWLY LIFT THROUGH THE AFTERNOON BUT SHOULD
REMAIN IN THE MVFR RANGE THROUGH 00Z. WITH THE LOSS OF
MIXING...LOWER DECK SHOULD MELT AWAY REVEALING MID-LEVEL DECK THAT
WILL HANG FAIRLY TOUGH THROUGH THE NIGHT. LOWER STRATUS WILL
DEVELOP ON THURSDAY MORNING AS MIXING INCREASES AND SHORTWAVE
APPRAOCHES FROM THE WEST. NOT MUCH IN THE WAY OF LOW LEVEL MOISTURE
TO WORK WITH...BUT POTENTIAL FOR SOME NON VISIBILITY RESTRICTING
RAIN ALONG AND WEST OF THE JAMES VALLEY THROUGH 13/00.

&&

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

$$

SHORT TERM...DUX
LONG TERM...JM
AVIATION...


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