000
FXUS63 KFSD 101612
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1111 AM CDT FRI OCT 10 2008
.DISCUSSION...
AS EXPECTED...EVERYTHING AS WEAKENED OR DISSIPATED AND LIFTED NORTH
AND WEST OF THE CWA. BIG QUESTION NOW BECOMES HOW TO HANDLE
TEMPERATRUES AND JUST WHERE THE SFC FRONT WILL END UP AND HOW MUCH
CLOUD COVER TO EXPECT. GOING FORECAST IN PRETTY GOOD SHAPE AND WILL
LIKELY NOT CHANGE MUCH WITH HIGHS NEAR 80 AT SUX AND NEAR 60 AT HON.
SOME LOCATIONS INBETWEEN...LIKE ALONG I90...MAY NEED TO BE TAKEN
DOWNWARD IF THE CLOUD COVER CONTINUES TO THICKEN. THE PLACEMENT OF
THE FRONT WILL ALSO BE A FACTOR IN PRECIPTIATION CHANCES FOR LATER
TONIGHT. IF THE FRONT REMAINS WHERE IT IS AT...EXPECT THE BULKL OF
ANY PRECIPITATION THAT DEVELOPS OVERNIGHT TO REMAIN NORTH AND WEST
OF THE AREA. WILL STILL CARRY A SMALL CHANCE FOR MAINLY AREAS WEST
OF THE JAMES RVIER LATE TONIGHT.
&&
.AVIATION...
VFR CONDITIONS CAN BE EXPECTED TO PERIST FOR KFSD/KHON AND KSUX
AREAS THRU 12Z SAT. KHON WILL SEE A CHANCE TO GET INTO SOME POST
FRONTAL MVFR CEILINGS BY THIS AFTERNOON HOWEVER AND MAY NEED TO BE
UPDATED. SCT VFR LIGHT SHRA WL PERSIST INTO THE EARLY MORNING HOURS
FOR KHON...WITH ANOTHER CHANCE FOR REDEVELOPMENT OF SHRA AND ISOLD
TSRA OCCURRING AFT 06Z SAT FOR KHON...IN AXIS OF GREATER ELEVATED
INSTABILITY AND STRONG MID LVL WINDS.
&&
.PREV DISCUSSION...
IN THE NEAR TERM THIS MORNING...WERE DEALING WITH A TON OF H85
FRONTOGENESIS AND ASSOCIATED WAA LIFTING NWD THRU THE CWFA.
THEREFORE SCT -SHRA CONT TO BE FOUND ACROSS THE NRN PTNS OF THE FA
ATTM...WITH EVEN SOME ACCAS SPRINKLES WHICH HAVE JUST DEVELOPED
AROUND THE IA GRTLKS VCNTY. ALL OF THIS ACTIVITY SHOULD LIFT NWD AS
THE MORNING PROGRESSES WITH THE H85 BOUNDARY. RH TIME SECTIONS SHOW
A DECREASE IN CLOUDS ONCE THE H85 BARCOCLINICTY PASSES THROUGH. SO
ONCE AGAIN...OPTED TO GO TO A PARTLY SUNNY OR PARTLY CLOUDY SKY FOR
MUCH OF THE FA THIS AFTERNOON...MINUS OF COURSE THE CHAMBERLAIN TO
HURON STRETCH WHO IS CLOSER TO THE MAIN LLV INVERTED TROF. IT IS
QUITE CLEAR RIGHT NOW IN CENTRAL AND ERN NEB...AND OUR FAR SRN FA IS
RIGHT ON THE EDGE OF IT. SO IT WL NOT TAKE MUCH SE LLV FLOW TO SHOVE
SOME CLEARING NWD AS IS EXPECTED. BECAUSE OF THIS...DECIDED TO KEEP
VERY MILD TEMPS THRU OUR SOUTH AND EAST. TEMPS ACROSS OUR FAR N AND
FAR W ARE VERY TRICKY. ONE WONDERS IF HURON AND CHAMBERLAIN WL NOT
HIT 60 AGAIN WHICH IS WHAT I CURRENTLY HAVE GOING. SO THAT WL HAVE
TO BE MONITORED VERY CAREFULLY BY THE DAY CREW. NEAR BROOKINGS AND
MARSHALL...AM BANKING ON SOME PARTIAL AFTERNOON SUN MAKING IT TO
THOSE LOCATIONS TO GET THEM INTO THE MID AND UPPER 60S AS THE SSE
LLV FLOW PUSHES NWD THRU THE DAY. BUT LIKE YESTERDAY...MY THERMAL
GRADIENT MAY NOT BE TIGHT ENUF FM OUR NW TO THE I 29 CORRIDOR.
AFTER THAT...WE ARE STILL DEALING WITH THE VERY LARGE UPPER LOW OVR
THE WRN CONUS WHICH PARKS ITSELF OUT THERE TONIGHT THRU SAT NIGHT.
PLACED THE SFC INVERTED TROF TONIGHT FM ABOUT ERN CHARLES MIX CO TO
KINGSBURY CO...WITH A VERY MILD SE FLOW AHEAD OF IT. EXPANDED OUR
LATE NIGHT POPS JUST A BIT EWD TO COVER ALL OF OUR AREA W OF I 29.
THIS IS BECAUSE BOTH THE NAM AND GFS ARE SHOWING A FAIR AMOUNT OF
ISENTROPIC LIFT AT AND ABV THE 300K LYR...WHICH SUGGESTS SOME HIGH
BASED SHRA MAY GET GOING. AS EVIDENCED RIGHT NOW WITH THE ABUNDANT
BUOYANCY...IT DOES NOT TAKE MUCH TO GET SHRA GOING.
SATURDAY IS VERY INTERESTING. THE NAM IS EXTREMELY AGGRESSIVE IN
CONTINUING TO PUSH THE SFC FRONT THRU THE I 29 CORRIDOR...WHEREAS
THE GFS HANGS IT WAY BACK TO THE WEST. THE NAM MID AND UPPER Q
VECTORS DO NOT SUPPORT THAT AGGRESSIVE OF A PUSH EWD WITH THE SFC
WINDS...SO IT COULD BE CONVECTIVELY DRIVEN BY THE MODEL. THEREFORE
ATTM...OPTED TO CHOOSE THE ECMWF SFC WIND POSITION WHICH STALLS THE
SFC BOUNDARY JUST W OF THE I 29 CORRIDOR. KEPT PCPN CHCS TIED TO
THIS BOUNDARY WITH AN ABSENCE OF S/W ENERGY AND THE BULK OF THE
ISENTROPIC LIFT GOES NWD IN THE MORNING. FOR TEMPS...SAME STORY.
VERY MILD AHEAD OF THE BOUNDARY IN OUR ERN HALF...FALLING OFF VERY
RAPIDLY BEHIND THE SFC BOUNDARY POSITION IN OUR WEST.
SAT NIGHT IS ALSO INTERESTING IN THAT BOTH THE NAM AND GFS SHOW A
QUICK MOVG S/W MOVG N TO NEWD THRU THE CWFA...WITH QUITE A BIT OF
MID LVL PV AND ELEVATED INSTABILITY. AGAIN WITH A LOT OF BROAD
ASCENT IN PLACE...DECIDED TO GO A LOT OF SCT POPS THRU MUCH OF OUR
ERN FA DUE TO THIS WAVE. IT APPEARS AS THOUGH THE INITIAL SFC
BOUNDARY ON SATURDAY WL WASH OUT HOPEFULLY JUST W OF I 29...AND A
NEW SFC BOUNDARY WL TAKE OVR IN CENTRAL SD PLACING OUR CWFA IN A
BRISK AND MOIST SE FLOW OF AIR. THE MODELS HAVE BEEN VERY CONSISTENT
IN SHOWING THIS CENTRAL SD CDFNT AHEAD OF THE HUGE UPPER LOW.
THEREFORE KEPT OUR LIKELY POPS GOING IN OUR NW CORNER WHERE MOISTURE
IS PRETTY DEEP THRU H5 AND CLOSER TO THE NEW BOUNDARY. LOWS WL BE
VERY MILD FOR THIS TIME OF YEAR...AND IN FACT OUR FAR WEST MAY
HARDLY DROP OFF FM THEIR DAYTIME HIGHS ON SATURDAY.
THEN ON SUNDAY...SUNDAY NIGHT AND INTO MONDAY...THE GFS AND NAM TAKE
THE UPPER LOW AND MOV IT NEWD INTO S CENTRAL CANADA. THIS WL ALLOW
THE SFC CDFNT TO MOV EWD GRADUALLY THRU OUR FA SUN AND SUN NIGHT.
THEREFORE HIGH POPS ARE STILL WARRANTED IN THESE TWO PERIODS AND
ELEVATED INSTABILITY IS STILL ABUNDANT. OBVIOUSLY MAX TEMPS ON
SUNDAY ARE DIFFICULT DUE TO THE FROPA WHICH SHOULD BE CLOSING IN ON
THE I 29 CORRIDOR BY EARLY EVENING. THEREFORE ONLY MODESTLY RAISED
TEMPS IN OUR FAR WEST FROM SATURDAY MORNING MINS. CONVERSELY...HIGHS
ONCE AGAIN SHOULD BE QUITE MILD AHEAD OF THE FRONT IN OUR E DESPITE
A MOSTLY CLOUDY SKY. WITH THIS MUCH MOIST AIR ADVECTING NWD...TEMPS
CAN STILL WARM UP DESPITE CLOUDS...AND AREAS IN OUR EAST COULD SEE
PARTIAL SUNSHINE AT TIMES ANYWAY.
LIKELY POPS ARE STILL WARRANTED IN OUR FAR E MONDAY MORNING WITH THE
CDFNT.
INTERESTINGLY...BOTH THE ECMWF AND GEM THEN BRING THE SRN PTN OF THE
UPPER LOW EWD INTO THE PLAINS ON TUESDAY. THIS UPPER LOW WAS HELD
BACK FM THE INITIAL UPPER LOW HEADING INTO S CENTRAL CANADA. THIS IS
NOT AN UNREALISTIC SCENARIO AT ALL. THEREFORE THERE COULD BE A
TEMPORARY LULL IN THE PCPN MON NIGHT...ONLY TO REFORM AGAIN ON
TUESDAY AT LEAST IN OUR ERN FA WITH THIS SECOND UPPER LOW. SOMETHING
TO KEEP AN EYE ON. THEREFORE ADDED SOME LOW POPS FOR NOW IN OUR EAST
ON TUE.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
PUBLIC...MJF
AVIATION...CHAPMAN
