000 
FXUS63 KFSD 171712
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1111 AM CST WED NOV 17 2004

.DISCUSSION...
UPDATED ALL ZONES AND GRIDS WITH THE BIGGEST CHANGES TO THE 
TEMPERATURE FIELDS. THICK CIRRUS ASSOCIATED WITH H300 JET STREAK 
REALLY HOLDING TEMPS DOWN IN THE NORTH AND WEST...WHILE TEMPS HAVE 
EASILY CLIMBED INTO THE 60S SOUTH OF WARM FRONT IN NW IOWA. MAX 
MIXING IN WARM SECTOR YIELDS HIGHS IN LOW 60S AND MANY LOCATIONS 
WILL JUMP UP TO NEAR HIGH SOON AND THEN STABILIZE. NUMEROUS ECHOES 
IN WESTERN CWA SEEM TO BE NOTHING MORE THAN VIRGA AS LAPS/RUC/ETA 
SOUNDINGS INDICATE A VERY DRY AIR MASS BELOW H700. HOWEVER AMPLE 
MOISTURE IS BEING ADVECTED NORTHWARD ALONG BOUNDARY COMING THROUGH 
NEBRASKA...SO HAVE SPED UP AND EXPANDED POPS THIS AFTERNOON TO COVER 
THIS. BOUNDARY SHOULD THEN SAG SOUTHWARD TONIGHT SO MADE ONLY A FEW 
MINOR TWEAKS TO TONIGHT PERIOD.


.PREV DISCUSSION...
IN THE SHORT TERM...PATCHY FOG IS A CONCERN ACRS THE ERN FA WHERE 
THINGS CLEARED OUT...WITH THE BONAFIDE STRATUS HAVING A HECK OF A 
TIME MAKING IT NWD INTO NW IA. TRYING TO PROG THE STRATUS NWD IS 
DIFFICULT INTO NW IA AS THE META 950MB SHOWS IT ADVECTING IN...BUT 
THE 925MB RH FIELD DOES NOT. ATTM LEFT IT OUT...AND REALLY INCREASED 
THE SKY COVER THRU THE FA A LITTLE LATER TODAY AS THICKER MID LVL 
CLOUDS STREAM NWD FM THE SRN PLAINS. WILL WATCH ANY LOCATIONS FOR A 
POSSIBLE DENSE FOG ADVY CLOSER TO SUNRISE AS SOMETIMES THE INVERSION 
LOWERS THEN HELPING TO ALLOW RADIATIONAL FOG TO GET OUT OF CONTROL.
OTHERWISE...UPPER LOW CONTS TO MEANDER IN CNTRL AND WRN TX TDAY...
STREAMING A LOT OF JUICY MID LVL AIR INTO THE FA AS THE DAY 
PROGRESSES. H7 FRONTOGENESIS BEGINS TO DEVELOP ACRS THE FAR SRN CWFA 
LATE TODAY NEAR A MID LVL CONVERGENCE ZONE...MARKING THE SLY FLOW TO 
THE SOUTH AND A NLY FLOW CLOSER TO I 90. THEREFORE KEPT THE SLGT CHC 
POPS GOING FROM SIOUX CITY TO STORM LAKE LATE TDAY...AND CHC OR SLGT 
CHC POPS ACRS THE SE QUAD TNGT AS THE FRONTOGENESIS LINGERS. KIND OF 
A STATIC PCPN PATTERN AND DIFFICULT TO TIME THINGS WITH THE SLOWNESS 
OF THE UPPER LOW TO THE SOUTH. SOME OF THIS LIGHT PCPN MAY TRY TO 
NUDGE A LITTLE FURTHER NWD ON THURSDAY. SOME H85 FRONTOGENESIS LEAKS 
UP BUT THE MID LVL CONVERGENCE WEAKENS. CERTAINLY MID LVL MSTR IS 
NOT A PROBLEM TNGT AND THURSDAY...BUT LOW LVL MSTR MAY BE AS A 
STRONG ANTICYCLONE MOVES OVER THE NRN PLAINS PRODUCING AT FIRST A NW 
FLOW...GOING NE ON THURSDAY ADVECTING IN SOME DRIER AIR. THEREFORE 
DO NOT WANT TO GO TOO CRAZY ON THE POPS...EVEN OVER OUR FAR SOUTH 
ATTM.

THURSDAY NIGHT THINGS BEGIN TO CHANGE. UPPER TROF ON BOTH THE 
ETA/GFS IS STILL PROGGED TO MOVE INTO THE DESERT SW GIVING THE SRN 
PLAINS UPPER LOW A BOOT. BOTH MODELS ARE CLOSE IN PROGGING THIS 
UPPER LOW TO TRACK INTO MO THURSDAY NIGHT...THEN NEWD ON FRIDAY WITH 
A REINFORCING S/W BEHIND IT IN NEB. STRONG INVERTED TROF COULD SETUP 
LATER THUR NIGHT AND FRI MRNG FM AROUND THE KANSAS CITY AREA...NWWD 
INTO THE SE QUAD OF THE FA. AT ANY RATE...MSTR REALLY DEEPENS WITH 
NO SHORTAGE OF UPPER -DIV Q FOR SUPPORT. THIS MSTR STREAMS AS FAR 
BACK AS THE WRN CWFA SO WOULD NOT RULE OUT PCPN IN THE WEST ALSO. 
WENT WELL ABV GUIDANCE FOR LOWS ON THUR NIGHT WITH THE CLOUD COVER 
ANTICIPATED...AND BLO SOME HIGHS ON FRIDAY. FRIDAY COULD BE A RAW...
CHILLY DAY...AND MOST HIGHS I HAVE ARE NOT TOO FAR FM THE LOWS.

SATURDAY WILL NEED WATCHING AS THE LATEST GFS IS ROTATING A S/W 
AROUND THE BASE OF THE UPPER TROF THRU THE CNTRL PLAINS. IT IS 
TRYING TO BRING A LITTLE MSTR INTO THE SE PART OF THE FA AND WITH 
THE AMOUNT OF BAROCLINICITY INVOLVED...WOULD NOT RULE IT OUT BUT 
LEFT IT DRY FOR NOW UNTIL FURTHER RUNS CONT THE TREND. ADJUSTED SAT 
NIGHT IN THE EXTENDED A BIT AND ADDED A SLGT CHC OR CHC OF -SN ACRS 
THE ERN CWFA. ANOTHER UPPER WAVE IS DIVING DOWN THE NLY FLOW ALOFT 
WITH STRONG -DIV Q IN THE MID AND UPPER LEVELS. WITH THE KIND OF CAA 
POURING IN...REALLY CANNOT RULE IT OUT.


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

$$

JRM/MJF