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000
FXUS63 KFSD 231139
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
639 AM CDT THU MAY 23 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 340 AM CDT THU MAY 23 2013

LIKELY THE BEST DAY OF THE NEXT MANY DAYS WILL OCCUR ACROSS THE
AREA TODAY WITH SHARP RIDGE ALOFT ACROSS THE AREA. EASTERLY TO
NORTHEAST TRAJECTORY OUT OF KEEWATIN HIGH WILL CONTINUE TO INTRODUCE
DRIER AIR AT LOWER LEVELS.  FLOW IS QUITE ANTICYCLONIC AND OVERALL
LARGER SCALE QUITE SUBSIDENT. RECENT PRECIPITATION HAS SATURATED UP
THE SURFACE QUITE A BIT...AND WITH HEATING AND BUILDING OF MIXED
LAYER WOULD EXPECT POTENTIAL FOR A BIT OF FLAT CUMULUS DEVELOPMENT.
LIKELY SOMEWHAT TERRAIN TIED. LARGE SCALE AND ANTICYCLONIC FLOW
SHOULD KEEP CLOUDS FROM GAINING A GREAT DEAL OF DIURNAL COVERAGE...
PROBABLY AN EARLY TO MID  AFTERNOON MAXIMUM IN THE SCATTERED
COVERAGE REALM. GOOD RECOVERY TO TEMPS WITH SUNSHINE TODAY...
MIXING TO MID 60S TO AROUND 70.

PRESSURE GRADIENT GRADUALLY INCREASES ACROSS THE AREA THROUGH THE
OVERNIGHT AS SURFACE RIDGE RETREATS TO THE EAST. RELATIVELY DRY
AIRMASS ACROSS THE AREA SHOULD LEAD TO COOL OVERNIGHT LOWS...WITH
THE COOLEST READINGS IN THE EASTERN CWA WHERE WINDS AND INCREASING
CLOUDS WILL BE LESS OF A FACTOR.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 340 AM CDT THU MAY 23 2013

MODELS INDICATE STRONG MOISTURE TRANSPORT IN THE MID LEVELS ON
FRIDAY LEADING TO ELEVATED CONVECTIVE POTENTIAL AS ISENTROPIC LIFT
INCREASES THROUGHOUT THE DAY. MODEL SOUNDINGS INDICATE TALL THIN
CAPE PROFILE...AND WITH RELATIVELY WEAK WIND SHEAR...AM NOT
EXPECTING MUCH IN THE WAY OF SEVERE POTENTIAL. BAND APPEARS TO
GRADUALLY SHIFT TO THE EAST FRIDAY NIGHT...WITH CONVECTIVE
POTENTIAL REORGANIZING TO THE SOUTH AS BETTER INSTABILITY AND
MOISTURE ORGANIZES TO THE SOUTH. MODELS INDICATE WARM FRONT
HANGING ACROSS THE AREA THROUGH THE WEEKEND...MAKING CONVECTION
DIFFICULT TO TIME. AM NOT THINKING THE WEEKEND WILL BE AN ENTIRE
WASHOUT...BUT INSTEAD PERIODIC RAIN CHANCES FAVORING A DIURNAL
TREND. SLIGHTLY BETTER SEVERE POTENTIAL EXISTS ON SATURDAY INTO
SUNDAY...HOWEVER...REALTIVELY WEAK WIND SHEAR SHOULD KEEP SEVERE
POTENTIAL FAIRLY ISOLATED. CONVECTION CHANCES APPEAR TO BE FAIRLY
GOOD SATURDAY NIGHT AS LOW LEVEL JET INCREASES ACROSS THE PLAINS
AND HAVE RAISED POPS SOME OVER GUIDANCE.

FORECAST BECOMES QUITE MUDDY BEYOND SATURDAY NIGHT WITH SHORTWAVES
EMBEDDED IN WEST TO SOUTHWEST FLOW ALOFT. MODELS IN GENERAL SUGGEST
AN ACTIVE PATTERN...WITH EACH OFFERING THEIR OWN FLAVOR ON TIMING
AND LOCATION OF POPS. IN GENERAL...KEPT CHANCE POPS THROUGH THE
PERIOD. IN TERMS OF TEMPERATURES...KEPT TEMPERATURES VERY SIMILAR
TO THE PREVIOUS FORECAST...HOWEVER...OPERATIONAL RUN OF GFS IS
ERRING TOWARDS THE WARMER SIDE OF THE ENSEMBLE...POTENTIALLY
SUGGESTING OPTIMISTIC FORECAST HIGHS FOR THE HOLIDAY WEEKEND INTO

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 638 AM CDT THU MAY 23 2013

WEBCAM AT HURON AIRPORT REVEALS THAT AUTOMATED OBSERVATION HAS
GENERALLY BEEN WELL OFF THIS MORNING...INDICATING AS LOW AS 1/4SM
VISIBILITY AND A 100 FT AGL CEILING AT TIMES...WHEN MUCH LESS
STRICT CONDITIONS HAVE BEEN IN PLAY. AS A RESULT...HAVE WRITTEN
A MUCH MORE OPTIMISTIC TAF FOR KHON...WITH SHALLOW MOISTURE IN
FORECAST SOUNDINGS SUPPORTIVE OF THE FUZZY 3-5SM VISIBILITY
APPARENTLY PRESENT. OTHERWISE...HAVE SOME MVFR CEILINGS ON VERGE
OF EXITING KSUX AREA BY 12Z...AND THIS WILL LEAD TO OVERALL VFR
CONDITIONS THROUGH REMAINDER OF PERIOD. SOME LOW END VFR CLOUDS
WILL DEVELOP AROUND MIDDAY HOURS.  AS SOUTHERLY GRADIENT ALOFT
INCREASES...KHON WILL LIKELY DEVELOP SOME LOW LEVEL WIND SHEAR
CONDITIONS AFTER 06Z.

&&

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

$$

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