RSS FeedsIssued by NWS La Crosse, WI
000 FXUS63 KARX 231001 AFDARX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 401 AM CST MON NOV 23 2009 .SHORT TERM...TODAY THROUGH WEDNESDAY AT 3 AM...A BAND OF RAIN WAS MOVING NORTH ACROSS PARTS OF NORTHEAST IOWA...SOUTHEAST MINNESOTA...AND WEST CENTRAL WISCONSIN. THIS RAIN WAS ASSOCIATED WITH MOISTURE TRANSPORT AND FRONTOGENESIS AHEAD OF A SHORT WAVE TROUGH MOVING NORTHEAST ACROSS EASTERN SOUTH DAKOTA...SOUTHERN MINNESOTA...IOWA...AND NORTHERN ILLINOIS. WHILE THE COURSER 23.00Z MODELS ARE SHOWING THAT THIS RAIN WILL CONTINUE THROUGH 23.12Z...THE 4 KM SPC NAM WRF INDICATES THAT THIS RAIN WILL CONTINUE THROUGH AT LEAST 23.15Z AND THEN IT MOVES QUICKLY NORTH THROUGH SOUTHEAST MINNESOTA AND WEST CENTRAL WISCONSIN BETWEEN BETWEEN 23.15Z AND 23.18Z. SINCE THIS MODEL IS DOING SO WELL THIS MORNING...THE FORECAST FOR TODAY WAS TRENDED TOWARD IT. LIKE THE PAST COUPLE OF DAYS...IT CONTINUES TO LOOK LIKE THE BEST FORCING AND MOISTURE TRANSPORT WILL REMAIN WEST OF THE FORECAST AREA THIS AFTERNOON AND EVENING. AS A RESULT...THESE FORECAST PERIODS WERE LEFT DRY. FROM LATE TONIGHT THROUGH TUESDAY NIGHT...THE MODELS HAVE CONTINUED TO TREND A BIT FURTHER SOUTH WITH THE LOW PRESSURE AREA. THE NAM/WRF IS BY FAR THE FARTHEST SOUTH WITH THIS SYSTEM. IT IS ACTUALLY AN OUTLIER WHEN COMPARED WITH THE GFS...GEM...AND ECMWF. DUE TO THIS...THE NAM/WRF WAS NOT USED FOR THESE TIME PERIODS. THERE WAS AN ATTEMPT TO LOWER THE PRECIPITATION CHANCES ALONG AND NORTH OF INTERSTATE 94 ON TUESDAY...BUT THERE WAS STILL ENOUGH CONCERN THAT THIS PRECIPITATION MAY BE A BIT FURTHER NORTH THAT THERE WAS LITTLE CHANGE TO THE PRECIPITATION CHANCES IN THESE AREAS. WHILE THERE WAS NO CHANGE TO THIS...THERE WAS SOME TIMING FOR THE RAIN ADDED TO THE GRIDS ON TUESDAY. ON WEDNESDAY...IT CONTINUES TO LOOK LIKE COLD AIR ADVECTION WILL MOVE INTO THE FORECAST AREA DURING THE AFTERNOON. DUE TO THIS A NON DIURNAL TEMPERATURE CURVE WAS USED. IN ADDITION...THE SNOW CHANCES WERE REMOVED ACROSS WESTERN WISCONSIN...AND DELAYED UNTIL THE MID TO LATE AFTERNOON IN NORTHWEST IOWA AND SOUTHEAST MINNESOTA. .LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY THE 23.00Z GFS...GEM...AND ECMWF CONTINUES TO SHOW THAT A SECONDARY SHORT WAVE TROUGH WILL DROP INTO THE LONG WAVE TROUGH LOCATED ACROSS NORTHERN AND CENTRAL PLAINS...MID AND UPPER MISSISSIPPI RIVER VALLEYS...GREAT LAKES AND OHIO VALLEY ON WEDNESDAY NIGHT. THIS GREATLY ENHANCES THE FRONTOGENESIS ACROSS WISCONSIN...EASTERN MINNESOTA...AND NORTHERN IOWA. IN ADDITION... THE SURFACE LOW SLOWLY DEEPENS AS IT MOVES NORTHEAST ACROSS SOUTHERN AND EASTERN WISCONSIN. AS THIS OCCURS...THE GFS INDICATES THAT WARM AIR ALOFT /POSSIBLY RELATED TO A TROWAL/ IS BROUGHT BACK WESTWARD INTO THE FORECAST AREA. MEANWHILE THE ECMWF KEEPS THIS WARM AIR FURTHER EAST AND THE PRECIPITATION TYPE REMAINS IN THE FORM OF SNOW. WITH SOME UNCERTAINTY IN THE PRECIPITATION TYPE ACROSS WISCONSIN...A MIX OF RAIN AND SNOW WAS INTRODUCED INTO THE WEATHER GRIDS FOR OUR WISCONSIN COUNTIES FOR WEDNESDAY NIGHT AND THANKSGIVING. MEANWHILE FURTHER WEST ACROSS SOUTHEAST MINNESOTA AND NORTHEAST IOWA...IT LOOKS LIKE THE PRECIPITATION TYPE WILL BE MAINLY SNOW. A MAJORITY OF THE GFS MREF PLUMES SHOW LESS THAN 2 INCHES OF SNOW WITH THIS SYSTEM. HOWEVER THERE ARE TWO OF THEM WHICH HAVE SNOWFALL TOTALS AROUND 6 INCHES. WHILE THERE WILL LIKELY BE A MIX OF RAIN AND SNOW IN LA CROSSE...THE PRECIPITATION TYPE PLUMES STILL SHOW SOME LIGHT SNOW ACCUMULATIONS /LESS THAN AN INCH/. MEANWHILE WITH THE PRECIPITATION STAYING IN THE FORM OF SNOW IN THE EMF...THE SNOWFALL AMOUNTS ACROSS THE FORECAST AREA RANGE FROM 4 TO 9 INCHES. NEEDLESS TO SAY...THIS SYSTEM STILL BEARS SOME WATCHING. && .AVIATION...TODAY AND TONIGHT BAND OF -RA CONTINUED TO EXTEND FROM NEAR DLH SOUTH ACROSS RST AND INTO SOUTHERN IA. RAIN WAS ASSOCIATED WITH SOME FRONTOGENETIC FORCING...ISENTROPIC UPGLIDE...AND IN AN AREA OF 850MB MOISTURE TRANSPORT. LATEST RUC13 AND NAM12 SHIFTS THIS FORCING WEST/NORTHWEST LATE THIS MORNING...AND SO SHOULD THE LIGHT RAIN. OTHER MESO MODELS //SPCWRF...ETC// ALSO SUPPORT THIS. LATEST FOG/STRATUS SATELLITE IMAGERY...COUPLED WITH SFC OBS...PLACED CEILINGS ACROSS THE LOCAL AREA FROM 6 TO 10 KFT. SATELLITE TRENDS WERE SHIFTING THIS AC DECK TO THE NORTH/NORTHWEST WITH WIND PROFILERS AND VAD WINDS SHOWING BACKING TO THE SOUTHEAST IN THE 925-700 MB LAYER OVER THE PAST FEW HOURS. JUST TO THE EAST OF THIS CLOUD MASS THE SKIES WERE CLEAR...WHICH WAS RESULTING IN SOME FOG AND STRATUS FORMATION OVER NORTHERN ILL/SOUTHEAST WI. WILL HAVE TO MONITOR TRENDS BEFORE 12Z ISSUANCE TO SEE IF SOME OF THESE LOWER CEILINGS/FOG COULD IMPACT THE KLSE. BELIEVE KRST WILL BE TOO FAR WEST. REGARDLESS....3-5SM MVFR BR SHOULD PERSIST THROUGH THE MORNING. UPPER LEVEL TROUGH WILL BE MOVING OVER THE SOUTHERN PLAINS BY 12Z TUES...AND THERE LOOKS TO BE A DECENT SURGE OF MOISTURE NORTHWARD AHEAD OF THIS SYSTEM. CEILINGS WILL GRADUALLY LOWER...POTENTIALLY IFR CONDITIONS BY TUES NIGHT. HOWEVER...IF THE CURRENT MID CLOUDS STAY MOSTLY WEST/NORTH OF KRST/KLSE TONIGHT...SOME FG AND STRATUS DEVELOPMENT COULD OCCUR BY 12Z TUES. NUMERICAL GUIDANCE POINTS TO THIS POSSIBILITY. CONFIDENCE NOT PARTICULARLY HIGH AT THE MOMENT...BUT TRENDS WILL HAVE TO BE MONITORED. WILL HINT AT THIS POSSIBILITY... WITH LATER UPDATES REFINING THE POTENTIAL. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...BOYNE AVIATION...RIECK
