000
FXUS63 KFSD 070142
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
842 PM CDT SAT SEP 6 2008
.DISCUSSION...
MADE SOME CHANGES TO THE TIMING OF PRECIPITATION TONIGHT. INITIAL
SHORTWAVE THAT BROUGHT THE LIGHT TO OCCASIONALLY MODERATE RAIN TO
THE AREA HAS PRETTY MUCH MOVED OUT WITH ONLY SOME LIGHT SHOWERS
AROUND JACKSON MN AT 830 PM CDT. EXPECT A PERIOD OF QUIET WEATHER
AFTER THIS FOR ABOUT 6 HOURS BEFORE NEXT SHORTWAVE MOVING ACROSS
NORTHERN SD SWINGS A COLD FRONT ALOFT THROUGH THE AREA. THIS WILL
BRING A BAND OF SHOWERS...WHICH SHOULD DECREASE IN COVERAGE AS YOU
TRAVEL SOUTH OF THE SHORTWAVE...THROUGH WITH THE BEST CHANCE FOR
ADDITIONAL RAINFALL OVER THE NORTHERN TIER OF COUNTIES.
OTHERWISE...LOWERED EVENING TEMPERATURES A LITTLE AS TEMPERATURES
DID NOT RECOVER MUCH BEHIND AREA OF PRECIPITATION. WILL ALSO HAVE TO
WATCH FOR FOG POTENTIAL...MAINLY OVER NORTHWEST IOWA...WITH LIGHT
WINDS AND A PERIOD OF CLEAR SKIES. IF THE SHORTWAVE TO THE NORTHWEST
IS STRONG ENOUGH TO BRING SHOWERS AND CLOUD COVER THROUGH...THIS
THREAT MAY BE MINOR AND CONFINED MAINLY TO LOW SPOTS.
08
&&
.AVIATION...
MAINLY VFR THROUGH THE NIGHT WITH A FEW SHOWERS POSSIBLE AT HON AND
FSD. SOME FOG ALSO POSSIBLE AT SUX AND FSD LATE TONIGHT. CONDITIONS
SHOULD REMAIN VFR IN SHOWERS BUT COULD FALL TO IFR IN FOG.
&&
.PREV DISCUSSION...
NORTH TO SOUTH ORIENTED BAND OF SHOWERS/ISOLATED THUNDERSTORMS WILL
CONTINUE TO WORK EAST LATE THIS AFTERNOON INTO THE EARLY EVENING
HOURS ACROSS THE FORECAST AREA. THIS ACTIVITY HAS DEVELOPED IN
RESPONSE TO WEAK SHORTWAVE MOVING THROUGH. SUBSIDENCE BEHIND THE
WAVE APPEARS TO BE FAIRLY LIMITED...WITH DIURNALLY DRIVEN SHOWERS
DEVELOPING ACROSS CENTRAL AND WESTERN PORTIONS OF THE STATE. EXPECT
THESE SHOWERS TO REMAIN ACROSS MAINLY WEST OF THE JAMES RIVER VALLEY
AND DIE WITH SUNSET. REMAINING SHOWERS TO THE EAST SHOULD BECOME
MORE ORIENTED NORTHWEST TO SOUTHEAST THIS EVENING INTO THE OVERNIGHT
AS LOW LEVEL BOUNDARY INTERACTS WITH MIDLEVEL WAVE. HAVE INCREASED
POPS THROUGH THE OVERNIGHT PERIOD...WITH 0.05-0.15 OF MOISTURE
EXPECTED IN MOST LOCATIONS. BEST CHANCES OF PRECIPITATION APPEAR TO
BE IN NORTHERN AND EASTERN PORTIONS OF CWA.
STILL VERY BUSY PATTERN THRU THE FCST...WITH MAIN ISSUES HOW FAR
NORTH THE MONDAY SYSTEM GETS AND HOW FAST WED NGT SYSTEM MOVES EAST.
STILL SOMEWHAT UNSTABLE FOR SUN AS WEAK TROUGH MOVES EAST...WITH
MAIN CHC SHRA IN NERN CWA IN THE MRNG...THEN A NICE BREAK FOR THE
AFTN OVER THE CWA. MODELS PRETTY STRONG WITH WAVE FOR SUN NGT AND
MON...BUT GFS TOO FAR NORTH WITH MAIN QPF BOUNDARY AND ALSO A LIT
ON THE FAST SIDE. WENT MORE WITH THE SOUTH BIAS OF THE OTHER
MODELS...BUT MEASURABLE RAIN STILL QUITE PSBL TO THE NORTH...WITH
A COOL RAIN TO THE SOUTH IN THE CWA. CERTAINLY EXPCT MORE FLIP/FLOPS
OF THE MODELS WITH THIS SYSTEM...AND NEXT FEW RUNS OF THE GFS WILL
MOST LIKELY REVERT TO THE SOUTH. CLRG OUT FM NW TO SE IN CWA FOR MON
NGT WITH GOOD RADIATIONAL COOLING EXPCD. NICE WARMING WITH SOUTH
WINDS SPRDG EAST OVER THE CWA FOR TUE THRU WED...ALONG WITH EXPCD
RETURN OF LOW LVL MOISTURE FOR LATE TUES NGT THRU WED. SO KEPT THE
POPS GOING FOR SRN CWA LATE TUES NGT AND MAINLY ERN CWA FOR WED AS
LOW LVL SLY JET INTERACTS WITH DYNAMIC WLY FLOW ALOFT. THE MAIN
DYNAMICS AND CHCS TSTMS EXCPD WITH MAIN UPR TROUGH AND CDFNT WED
NGT...MOVG OFF TO THE EAST ON THU. MODELS LOOK PRETTY CONSISTENT
BRINGING RETURN SLY FLOW OF WARMER AIR FOR FRI AFTN INTO SAT...AND
WENT WARMER THAN THE PREV FCST CLOSE TO HPC GUIDANCE.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE
IA...NONE.
NE...NONE.
&&
$$
BT/RSR
