FXUS63 KFSD 150857 AFDFSD AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 355 AM CDT MON MAR 15 2010 .DISCUSSION... IN THE NEAR TERM...INTERESTING LITTLE VORT MAX IN SERN SD CONTS TO GENERATE A FEW SHOWERS ATTM...AND WL LIKELY LINGER BETWEEN THE I 29 CORRIDOR AND JAMES RIVER VALLEY THIS MORNING. UNLIKE YESTERDAY HOWEVER...VERY LITTLE MINIMAL RAIN ACCUMULATIONS WL BE REALIZED. BELIEVE THE GFS WAS TOO AGGRESSIVE IN ITS EWD PUSH THIS MORNING OF THIS -RA...AS THE VORT MAX DIVES DEFINITELY MORE TO THE SE THAN STRAIGHT EWD BEFORE IT WEAKENS. THE SPIN SURE SHOWS UP NICE ON WV IMAGERY. OTHERWISE...THE CWFA IS JUST STUCK IN THE USUAL STRATUS WITH DENSE FOG IN SW MN...SWD THRU THE IA GRTLKS...AND SOME IMMEDIATE ADJACENT AREAS. THIS FOG HAS BEEN SOMETHING ELSE WHEN CONSIDERING THAT WE HAVE BEEN DEALING WITH A FAIRLY DECENT N OR NW SFC WIND THE PAST COUPLE OF DAYS. MENTION A THREAT OF -DZ IN MANY AREAS DUE TO THE STRATUS OUTSIDE OF THE BONAFIDE RAIN SHRA...BUT NO BIG DEAL. AND FINALLY...PUT A FEW BREAKS IN THE CLOUD COVER FOR THE AFTERNOON HRS INSTEAD OF GOING STRAIGHT 100 PERCENT ON THE SKY COVER...AS SOME AREAS HAVE BEEN BREAKING OUT A BIT IN THE AFTERNOON RECENTLY WITH DRYING FM ALOFT COMING DOWN DUE TO THE MARCH SUN. MAX TEMPS SHOULD BE GENERALLY IN THE 40S WITH PRETTY MILD H925 TEMPS TODAY. TONIGHT...ANOTHER S/W DIVES SWD FM S CENTRAL CANADA THRU MN AND THE EXTREME ERN DKTS. SOLID STRATUS SHOULD REFORM AGAIN AFTER SUNSET... AND A SMALL SLGT CHC POP IS WARRANTED IN OUR ERN ZONES WHERE THE MOISTURE IS DEEPER ASSOCIATED WITH THE WAVE. BUT OTHERWISE WITH SHALLOWER MOISTURE ALONG THE I 29 CORRIDOR AND WWD...ONLY MENTIONED THE THREAT OF SOME VERY LIGHT DZ ALONG AND E OF THE JAMES RIVER VALLEY. WEST OF THE JAMES...THE MOISTURE IS SHALLOWER YET...ONLY WARRANTING PATCHY FOG. LOW LEVEL TEMPS BEGIN TO COOL OFF WITH COOL SFC HIGH PRES ENTRENCHED. BUT STRATUS WL KEEP TEMPS IN THE LOWER TO MID 30S ONCE AGAIN. TUESDAY IS INTERESTING IN THAT THERE IS A POCKET OF COOL AIR IN THE LOW LEVELS JUST OFF THE SFC RIGHT ON TOP OF THIS FA. WITH A NLY FETCH OF AIR...BACKED OFF ON SOME MAX TEMPS IN THE FAVORED COOLER LOCATIONS...ESP WITH WET GROUND/LINGERING SNOW COVER SUCH AS SW MN AND THE JAMES RIVER VALLEY ALL THE WAY DOWN TO KYKN. EVEN CHAMBERLAIN MANY TIMES STRUGGLES WITH A N SFC WIND. STILL LOOKS LIKE THERE MAY BE FINALLY SOME GOOD DRYING WITH REGARDS TO THE SKY COVER ALONG AND WEST OF THE JAMES RIVER VALLEY. BUT E OF THE JAMES... GETTING RID OF ALL THE STRATUS MAY BE TOUGH WITH THE AFOREMENTIONED COOL AIR OVER THE WET GROUND. USUALLY THAT IS NOT GOOD FOR CLEARING DURING THE DAY HOURS. ON TUE NIGHT...BOTH MODELS FINALLY ADVECT THE H925-H9 MOISTURE EWD A FAIR AMOUNT...WITH THE GFS SLOWER THAN THE NAM. FOR NOW... COMPROMISED BETWEEN THE TWO SOLUTIONS IN HOW FAR EAST THE CLEARING LINE ADVANCES AND KEPT OUR FAR ERN ZONES MOSTLY CLOUDY. AND OF COURSE WITH ANY NIGHT TIME CLEARING AND LIGHT WINDS ALONG AND W OF I 29...WE RUN THE REAL RISK OF RADIATIONAL FOG DEVELOPMENT. THAT SCENARIO WL BE LOOKED AT CLOSER FOR TODAY AND TONIGHTS SHIFTS. FOR MIN TEMPS...HAVE A FULL 10 DEG SPREAD FM NW TO SE...AGAIN BANKING ON CLEARING IN OUR WEST...AND CLOUDS EAST. ASIDE FM ANY POTENTIAL OF RADIATIONAL MORNING FOG...WED LOOKS QUIET WX WISE AND MILD. AS SFC WINDS BECOME SWLY...LOCATIONS SHOULD NOT HAVE ANY TROUBLE REACHING THE MID 50S IN OUR SW...TO MID 40S IN SW MN. FURTHER OUT...DECIDED TO ADD A SLGT CHC POP FOR RAIN IN SOME OF OUR WRN ZONES THUR AFTERNOON. MID LVL CLOUDINESS PICKS UP IN THAT AREA IN ADVANCE OF THE NEXT UPPER TROF...COUPLED WITH A DECENT RR QUAD OF A JET STREAK. THE 00Z ECMWF AND CANADIAN GLOBAL REALLY SCREAM THE FROPA THRU OUR FA QUICKLY ON THURSDAY WITH THE GFS A SLOWER OUTLIER. THIS IS BOTHERSOME. WITH THE DEGREE OF JET STRENGTH AND HGT FALLS COMING DOWN FM THE NW...THE QUICKER SOLUTIONS MAY NOT BE BAD AT ALL. THEREFORE BACKED OFF ON OUR MAX TEMPS ON THURSDAY IN OUR NRN FA. EVEN WITH THE SLOWER GFS...OUR NRN ZONES MAY STRUGGLE TO WARM A BIT WITH THE ADVANCING MID AND HIGH CLOUDS. SO WITH THE QUICKER LOW LEVEL FROPA...THE ECMWF AND GEM SETUP THE PCPN BASICALLY TO THE SOUTH OF OUR FA THUR NIGHT AND FRIDAY. THE GFS PUTS MOST OF THE WET WX ON OUR FA AS THE RR QUAD OF THE JET IS FURTHER NORTH...AS WELL AS THE BOUNDARY. WITH THIS KIND OF DISCREPANCY...DECIDED NOT TO ALTER POPS AT ALL LATE THIS WEEK. BUT DID CONT THE TREND OF HIGHER POPS IN OUR SOUTH...AND LOWER POPS NORTH. /MJF && .AVIATION... COPIOUS LOW LVL MOISTURE WILL RESULT IN CONTD MOSTLY IFR CIGS THRU 16/12Z. SLIGHT DAYTIME WARMING MAY LIFT CIGS TO 1-2K FT IN SOME AREAS 17Z-02Z AFTER WHICH ANY SUCH HIR CIGS LIKELY TO LOWER AGAIN TO BLO 1K FT. VSBYS THRU 18Z WILL BE VFR VRBL TO MVFR MOST OF SERN SD AND FAR NERN NE. IFR TO LIFR VSBYS NEAR ZERO IN PLACES WILL CONT OVER MOST OF SWRN MN AND NWRN IA AS WELL AS NEAR THE BKX AREA. AFT 18Z VSBYS SHUD BE GNLY ABV 5SM W TO 3-5SM FAR E THO A FEW AREAS OF 1-3SM IN BR MAY LINGER FAR ERN FCST AREA. VSBYS LIKELY TO LWR AGAIN AFT 00Z-03Z...THO HIR CLD DECK MAY DVLP OVER ERN FCST AREA WITH WEAK SHRTWV TNGT AND LIMIT SOMEWHAT ANY FOG INCREASE. /WILLIAMS && .FSD WATCHES/WARNINGS/ADVISORIES... IA...DENSE FOG ADVISORY UNTIL 1 PM CDT MONDAY FOR IAZ002-003-013-014- 022. MN...DENSE FOG ADVISORY UNTIL 1 PM CDT MONDAY FOR MNZ071-072-080-081- 089-090-097. NE...NONE. SD...DENSE FOG ADVISORY UNTIL 1 PM CDT MONDAY FOR SDZ039-040-055-056. && $$