Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 171710
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1210 PM CDT WED SEP 17 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 314 AM CDT WED SEP 17 2014

SOUTHERLY TO SOUTHEASTERLY LOW LEVEL FLOW CONTINUES TO DEVELOP
SLOWLY THIS MORNING. WEAK BACK DOOR COLD FRONT WILL OOZE INTO THE
AREA AND TURN THE FLOW MORE EASTERLY FOR A WHILE BEFORE IT
DISSIPATES. MOISTURE FLOW AT THE UPPER EDGE OF LOW LEVELS...THAT IS
AROUND H8...WILL SHIFT A LITTLE MORE EAST BEFORE STAGNATING AS IT
GETS A LITTLE HEATED AND MIXED OUT. THE DAY SHOULD BE MOSTLY SUNNY
WEST TO PARTLY CLOUDY EAST WITH HIGH TEMPERATURES CLOSE TO WHAT WE
HAVE BEEN CARRYING...OR 70 NORTHEAST TO MID 70S SOUTHWEST.

TONIGHT MODELS CONTINUE TO SHOW A MUCH LOWER MOISTURE INFLOW AND
HINT AT THE DEVELOPMENT OF STRATUS AND POSSIBLY SOME DRIZZLE...
ESPECIALLY ALONG THE MISSOURI RIVER AREA. MODELS GENERALLY DO POORLY
ON LOW LEVEL MOISTURE PATTERNS WITH A TENDENCY TO OVERDO THE
MOISTURE. STILL...AN INCREASE IN LOW STRATUS LATE TONIGHT SEEMS
REASONABLE ESPECIALLY OVER THE ABOVE MENTIONED MISSOURI RIVER AREA.
THE DRIZZLE IS MORE OF A PROBLEM GIVE THE LIMITED DEPTH OF THE
MOISTURE AND THE MODELS NOT SHOWING SOLID SATURATION. THE DRIZZLE
FOR LATE TONIGHT WAS MENTIONED IN THE FORECAST FROM YESTERDAY AND
WILL KEEP FOR NOW. LOW TEMPERATURES ARE EXPECTED TO BE INT HE LOWER
50S NORTHEAST TO THE UPPER 50S SOUTH. THE MAIN CHALLENGE ON THURSDAY
WILL BE THE THREAT FOR A LITTLE FOG AND DRIZZLE. WHILE THE SOUNDINGS
ARE NOT SCREAMING WIDESPREAD FOG AND DRIZZLE THERE ARE ENOUGH
SIGNALS...ESPECIALLY OVER THE SOUTHWESTERN TWO THIRDS OF THE
CWA...TO HAVE A MENTION. EVEN PARTS OF GREGORY COUNTY COULD SEE A
PASSING THUNDERSTORM AS A WEAK WAVE MOVES THROUGH BUT THAT THREAT IS
VERY MINIMAL. FOR NOW WILL ERODE THE FOG AND DRIZZLE IN THE MORNING
BUT EXPECT MOSTLY CLOUDY CONDITIONS THROUGH THE DAY WITH AN
INCREASING DEW POINT AT THE SURFACE. THIS WILL KEEP HIGH
TEMPERATURES IN CHECK...TOPPING OUT MAINLY IN THE LOWER TO MIDDLE
70S.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 314 AM CDT WED SEP 17 2014

BY THURSDAY NIGHT THE THETA E ADVECTION IN THE MID LEVELS INCREASES
QUITE A BIT AND EXPECT SCATTERED SHOWERS AND THUNDERSTORMS TO
DEVELOP...ESPECIALLY OVER THE EASTERN HALF OF THE CWA. WILL CARRY A
LOW CHANCE IN THAT AREA. STRONG SOUTHERLY FLOW AND RELATIVELY HIGH
DEW POINTS WILL KEEP LOW TEMPERATURES IN THE LOWER TO MIDDLE 60S.

FRIDAY AFTERNOON AND NIGHT WILL SEE A FAIRLY STRONG JET MAX CRUISE
BY TO THE NORTH OF THE AREA. THIS LEAVES MUCH OF THE AREA IN THE
RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET. THIS WILL PUT THE AREA
IN A DECENT LOCATION FOR SHOWERS AND THUNDERSTORMS AS LOW PRESSURE
TO THE NORTHEAST WILL SWING THROUGH A COLD FRONT OVERNIGHT.
TEMPERATURES AHEAD OF THIS FRONT SHOULD CLIMB FAIRLY
NICELY...REACHING THE MID AND UPPER 80S IN MANY LOCATIONS. PLENTY OF
INSTABILITY TO SUPPORT SOME SEVERE THUNDERSTORMS SO WILL NEED TO
KEEP AN EYE OUT FOR THE THREAT ON FRIDAY NIGHT.

IN THE OUTER PERIODS (SATURDAY THROUGH TUESDAY)...A TROUGH OF LOW
PRESSURE IS EXPECTED TO SWING THROUGH ON SATURDAY...THEN DEEPEN OVER
THE GREAT LAKES REGION AND NORTHEAST UNITED STATES. THIS SHOULD SET
UP A MILD AND DRY PATTERN. UPPER LEVEL FLOW WILL BE MODERATE TO
BEGIN THE PERIOD AS THE TROUGH MOVES THROUGH BUT WILL WEAKEN BY
LATER IN THE PERIOD AS A RIDGE OF HIGH PRESSURE ALOFT BUILDS OVER
THE WESTERN HIGH PLAINS. THIS SHOULD BRING VERY SEASONAL
TEMPERATURES WITH LOWS GENERALLY IN THE MID 40S TO LOWER 50S AND
HIGHS IN THE 70S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1159 AM CDT WED SEP 17 2014

EASTERLY WINDS WILL PREVAIL INTO THE EVENING HOURS...BEFORE
TURNING MORE SOUTHERLY AFTER MIDNIGHT. SCATTERED CU FIELD LIKELY
THIS AFTERNOON...WITH MODELS SUGGESTING A SCATTERED 10K FT AGL
DECK MOVING IN THIS EVENING AS WEAK SHORTWAVE PASSES THROUGH.

MODELS STILL SUGGEST LOW LEVEL MVFR/IFR STRATUS DEVELOPING TOWARD
DAYBREAK WITH LOCALIZED MVFR VISIBILITY RESTRICTIONS...WHICH WILL
GRADUALLY LIFT THROUGH THE MORNING.

&&

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

$$

SHORT TERM...
LONG TERM...08
AVIATION...DUX



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