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