000 FXUS63 KARX 100349 AFDARX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 949 PM CST TUE FEB 9 2010 .UPDATE... ONLY VERY LIGHT SNOW REMAINS ACROSS THE AREA WITH MOST VISIBILITIES NOW AT OR ABOVE 3 MILES. CALLS AROUND THE AREA THIS EVENING INDICATE THAT ONLY A DUSTING AT MOST AS OCCURRED SINCE 6 PM AND NO PROBLEMS WITH BLOWING OR DRIFTING SNOW REPORTED. THE REMAINING SNOW WILL END LATE THIS EVENING OR SHORTLY AFTER MIDNIGHT SO DECIDED TO END THE ADVISORY EARLY WITH LITTLE OR NO ADDITIONAL ACCUMULATIONS EXPECTED TO OCCUR. 04 && .PREV DISCUSSION... /ISSUED 604 PM CST TUE FEB 9 2010/ UPDATE... RADAR RETURNS INDICATE NOTHING BUT LIGHT SNOW IS FALLING OVER SOUTHEAST MINNESOTA AND NORTHEAST IOWA. NORTH WINDS ARE NOT REAL STRONG SO ANY BLOWING SNOW THAT IS OCCURRING IS LIKELY VERY ISOLATED IN NATURE. HAVE LET THE WINTER STORM WARNING EXPIRE AS SCHEDULED WHILE MAINTAINING THE WINTER WEATHER ADVISORY FROM THE MISSISSIPPI RIVER COUNTIES EAST INTO CENTRAL WISCONSIN. 04 PREV DISCUSSION... /ISSUED 302 PM CST TUE FEB 9 2010/ SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT FORECAST CONCERNS THIS PACKAGE...SNOW/BLOWING SNOW YET THIS EVENING...SNOW CHANCE AGAIN FRI/FRI NIGHT...TEMPERATURES THRU THE PERIOD. 18Z DATA ANALYSIS HAD LOW PRESSURE NEAR THE OH/KY BORDER WITH A TROUGH TO THE NORTHWEST INTO IA. PRESSURES STILL FALLING ACROSS THE FCST AREA BUT STRONGEST FALLS OF 5+MB/3HRS OVER LK ERIE. WV IMAGERY SHOWED THE UPPER LOW SPINNING OVER EAST CENTRAL MO...WITH MOISTURE PLUME/TROWAL WRAPPED AROUND TO THE NORTH OF THE LOW. COLD POCKET OF AIR AT THE SFC UNDER THE LOW...WITH TEMPS IN THE SINGLE DIGITS ACROSS SOUTHERN IA/NORTHERN MO...WHILE TEMPS ACROSS NORTHERN IA/ SOUTHERN MN IN THE 20S. AREA RADARS SHOWED A BROAD AREA OF GENERALLY LIGHT SNOW ACROSS WI AND NEARBY AREAS IN THE TROWAL/ MOISTURE PLUME AND BROAD ISENTROPIC LIFT/THETA-E CONVERGENCE. SNOW TAPERING OFF ALONG/WEST OF I-35 EARLY THIS AFTERNOON. NO ISSUES NOTED WITH 09.12Z NAM/GFS/ECMWF/GEM INITIALIZATIONS. THESE SOLUTIONS VERY SIMILAR FOR TONIGHT THRU THU...BEFORE DIVERGING WITH THE TIMING/STRENGTH OF A SHORTWAVE DROPPING THRU THE NORTHWEST FLOW ALOFT AND ACROSS THE REGION THU NIGHT INTO FRI NIGHT. DPROG/DT OF 500MB HGTS AT 09.12Z SHOWED MODEL RUNS OF 07.12Z AND 08.12Z ALL VERIFIED QUITE WELL ACROSS NOAM/EASTERN PAC. SLIGHT EDGE ON RUN-TO- RUN CONSISTENCY TO ECMWF...BUT ALL WERE A BIT WEAK WITH THE UPPER LOW OFF THE NORTHERN CA COAST. THRU 36HRS MODELS CONVERGING TOWARD COMMON SOLUTIONS WITH THE UPPER LOW MOVING OFF THE EAST COAST AND THE ONE TO NEAR THE AZ/MEX BORDER. ECMWF WITH THE BETTER RUN-TO-RUN CONSISTENCY. FOR 36-60HRS MODELS HAVE TRENDED TOWARD FASTER OF THE EARLIER RUNS WITH THE SOUTHERN STREAM TROUGH INTO TX. MODEL CONSENSUS TIGHTENING WITH THE SHORTWAVE DROPPING INTO THE DAKOTAS AT 60HRS...TRENDING TOWARD BLEND OF EARLIER MODELS ON STRENGTH/TIMING. GFS/UKMET/GEM REMAIN ON THE FASTER SIDE WITH THIS FEATURE...ECMWF/ NAM SLOWER. MODEL CONSISTENCY IMPROVED WITH THIS LEAD WAVE IN THE 60-84HR PERIOD...BUT RUN-TO-RUN CONSISTENCY POOR WITH THE NEXT STRONGER WAVE TO DROP INTO ND/MN AND IMPACT THE AREA JUST BEYOND THE SHORT TERM. CHECK OF OBS VS. MODEL DATA SHOWED NAM/GFS/ECMWF/GEM QUITE GOOD WITH THE SFC MASS FIELDS ACROSS THE CENTRAL CONUS. PER WV IMAGERY ALL LOOKED QUITE GOOD WITH THE SHORTWAVE DETAILS OVER CENTRAL NOAM. GFS/ECMWF/GEM BETTER WITH DETAILS IN THE UPPER LOW OFF THE CA COAST. MODEL/ENSEMBLE CONSENSUS...INCLUDING LOCAL/REGIONAL WRF MODELS...GOOD WITH THE 12Z-18Z PRECIP ACROSS THE CENTRAL CONUS. NO CLEAR DETERMINISTIC MODEL FAVORITE THIS CYCLE AND AGAIN FAVORED THE MODEL/ENSEMBLE CONSENSUS. WITH THE GOOD CONSENSUS...FORECAST CONFIDENCE GOOD FOR TONIGHT THRU THU...THEN AVERAGE AT BEST BY FRI/FRI NIGHT WITH THE POOR RUN-TO-RUN CONSISTENCY WITH THE NEXT SHORTWAVE CROSSING THE REGION. FOR THE SHORT TERM...TROWAL NORTH OF THE UPPER LOW...ISENTROPIC LIFT AND THETA-E CONVERGENCE WITH IT WILL PIVOT OVER THE AREA THRU THE REST OF THE AFTERNOON...THEN SLOWLY ROTATE EAST OF THE AREA THRU THIS EVENING. STRONG ENSEMBLE/MODEL CONSENSUS FOR SOME -SN TO LINGER OVER THE FCST AREA THIS EVENING...ESPECIALLY ALONG/EAST OF THE MS RIVER...WITH ADDITIONAL MINOR -SN ACCUMULATIONS. WITH SNOW ALREADY TAPERING OFF WEST OF ROUGHLY A KRST-KOLZ LINE...WILL LET WINTER STORM WARNING EXPIRE AT 6 PM. GIVEN ADDITIONAL SNOW ACCUMULATIONS ALONG/EAST OF THE MS RIVER INTO THIS EVENING...WILL EXTEND WINTER WEATHER ADVISORY THRU 03Z /9PM/. WET ROADS THIS AFTERNOON WITH SOME SOLAR INSOLATION GETTING THRU THE CLOUD LAYER...WILL BECOME ICY THIS EVENING WITH SUNSET AND CONTINUED -SN. LOW/LIFT PULL AWAY AFTER MIDNIGHT WITH COLUMN ABOVE 900MB DRYING OUT BY 12Z WED. LINGERED A SMALL -SN CHANCE AFTER MIDNIGHT THEN REMOVED -SN CHANCE AFTER 09Z. MODEL SOUNDINGS AND 925MB RH PROGS INDICATE SOME LOWER LEVEL MOISTURE TO BE TRAPPED UNDER AN INVERSION THRU WED. MODELS DIFFER A BIT ON HOW QUICKLY THIS MOISTURE AND LIKELY STRATO-CU DECK ADVECTS EAST OF THE AREA ON WED. NAM/ECMWF FASTER...GFS SLOWER. TRENDED TOWARD MORE CLOUDS WED MORNING...THEN REMAINED OPTIMISTIC FOR SUNSHINE/CLEARING FOR THE AFTERNOON AS THE SFC-850MB RIDGE AXIS APPROACHES. WITH THIS RIDGE AXIS OVER THE AREA WED NIGHT...THE FRESH SNOW COVER AND CLEAR/MOSTLY CLEAR SKIES...THU MORNING TO BE THE COLDEST MORNING OF THE WEEK WITH SUB-ZERO LOWS MOST LOCATIONS. MID/HIGH LEVEL MOISTURE AHEAD OF THE NEXT SHORTWAVE IN THE NORTHWEST FLOW STARTS TO SPREAD ACROSS THE AREA THU...BUT SHOULD STILL SEE PLENTY OF SUNSHINE. MODELS START TO DIVERGE WITH THE SPEED OF THE NEXT SHORTWAVE THU NIGHT...GEM/GFS FASTER...NAM/ECMWF SLOWER. WITH SREF INCREASING THE PROBABILITY OF PRECIP BY LATE THU NIGHT...DID ADD A SMALL -SN CHANCE TO THE WEST HALF OF THE FCST AREA. EVEN WITH DIFFERENCES AMONG THE MODELS...REASONABLE CONSENSUS AMONG THEM AND SREF MEAN FOR THE PASSING WAVE AND WEAK SFC REFLECTION TO PRODUCE SOME LIGHT PRECIP ACROSS THE AREA FRI INTO FRI NIGHT. RAISED -SN CHANCES TO AROUND 30 PERCENT OVER MAINLY THE CENTRAL/WEST PARTS OF THE FCST AREA BOTH PERIODS. GUIDANCE LOWS SIMILAR FOR TONIGHT AND APPEAR REASONABLE. WITH THE FRESH SNOW COVER...FAVORED COLDER OF GUIDANCE HIGHS WED. WITH THE LIGHT WINDS/CLEAR SKIES UNDER THE RIDGE AXIS WED NIGHT EVEN COLDER OF GUIDANCE LOWS LOOK TOO WARM AND CONTINUED THE PREVIOUS FCST GRID LOWS OF A CATEGORY OR TWO BELOW THE GUIDANCE FOR MOST LOCATIONS. WITH THE COLD START THU MORNING...EVEN COLDER OF GUIDANCE HIGHS LOOK ABOUT A CATEGORY TOO WARM MOST LOCATIONS. FAVORED COLDER OF GUIDANCE LOWS THU NIGHT...WITH PERHAPS LOWS IN THE EVENING THEN SLOWLY RISING TEMPS AFTER MIDNIGHT AS CLOUDS INCREASE. WITH DIFFERENCES AMONG THE MODELS FOR FRI/FRI NIGHT...FAVORED A BLEND OF GFS MEX/ENSEMBLE MOS AND HPC GUIDANCE TEMPS...WEIGHTED TOWARD THE GFS ENSEMBLE MOS. LONG TERM...SATURDAY THROUGH TUESDAY 09.00Z MEDIUM RANGE MODELS HAVE TRENDED STRONGER THAN THEIR 08.00Z RUNS WITH A SHORTWAVE TROUGH TO DROP INTO/ACROSS THE WESTERN GREAT LAKES SAT/SUN. HOWEVER...CONSIDERABLE DIFFERENCES AMONG THE MODELS WITH TIMING/TRACK/STRENGTH DETAILS OF THIS FEATURE. ECMWF ON THE FASTER SIDE OF THE ENVELOPE...GEM ON THE SLOW/STRONG SIDE...GFS/ UKMET/GFS ENSEMBLE MEAN IN THE MIDDLE ON TIMING/STRENGTH. MEDIUM RANGE MODELS IN BETTER AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS IN THE MON/TUE PERIOD AS LONGWAVE TROUGHING ROTATES THRU THE EASTERN CONUS AND THE REGION REMAINS UNDER NORTHWEST FLOW ALOFT. GIVEN THE DIFFERENCES WITH THE SAT/SUN PERIOD...LONG-TERM FCST CONFIDENCE AVERAGE AT BEST THIS CYCLE. FAVORING A MODEL/ENSEMBLE CONSENSUS WHICH IS SIMILAR TO GFS/UKMET...ANOTHER STRONG SHORTWAVE POISED TO DROP ACROSS THE WESTERN GREAT LAKES SAT/SAT NIGHT AS A CLOSED 500MB LOW AND AN INVERTED TROUGH AT THE SFC...VERY SIMILAR TO THE SYSTEM FROM MON THRU TODAY. RAISED/ADDED A SNOW CHANCE TO SAT/SAT NIGHT. MAY YET NEED A SMALL LINGERING SNOW CHANCE FOR SUN. BUT GIVEN A REASONABLE MODEL CONSENSUS FOR ANOTHER CAN HIGH PRESSURE SYSTEM TO DROP INTO THE REGION FOR THE SUN-TUE PERIOD...LEFT THESE PERIODS DRY FOR NOW. WITH THE NORTHWEST FLOW ALOFT TEMPS LOOK TO REMAIN BELOW NORMAL. A BLEND OF GFS MEX/HPC GUIDANCE HIGHS APPEARING REASONABLE THRU THE DAY 4-7 PERIOD. AVIATION...TONIGHT AND WEDNESDAY THE LOW PRESSURE SYSTEM THAT GAVE THE AREA A LONG-DURATION/ SIGNIFICANT SNOWFALL WILL PULL INTO THE OHIO RIVER VALLEY REGION TONIGHT. AS A RESULT...LOOK FOR THE SNOW TO CONTINUE DIMINISHING FROM WEST TO EAST THIS EVENING. HOWEVER...NORTH WINDS AT 10 TO 20 MPH WITH GUSTS AROUND 25 MPH WILL CONTINUE TO PRODUCE SOME BLSN AT KRST TIL MIDNIGHT. OTHERWISE...IFR VIS WILL IMPROVE TO VFR BY MIDNIGHT WITH THE DIMINISHED SNOW AND BLSN. MVFR CIGS WILL LIKELY CONTINUE PAST MIDNIGHT...EVENTUALLY SCATTERING OUT AFTER 10.09Z AS A RIDGE OF HIGH PRESSURE BUILDS IN FROM THE PLAINS. QUIET/VFR CONDITIONS WILL BE SEEN ON WEDNESDAY AS HIGH PRESSURE BUILDS OVER THE AREA. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM... RRS AVIATION.......... DAS