Issued by NWS Milwaukee/Sullivan, WI
000 FXUS63 KMKX 071009 AFDMKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 409 AM CST FRI NOV 7 2008 .DISCUSSION...FORECAST FOCUS ON PRECIPITATION COVERAGE AND TYPE WITH SLOWLY APPROACHING UPPER LOW. THEN ATTENTION TURNS TO MODEL DIFFERENCE WITH RESPECT TO SYSTEM FOR MONDAY NIGHT INTO TUESDAY. TODAY- UPPER LOW CENTER ACROSS SOUTHERN MINNESOTA TO DRIFT TOWARDS SW WISCONSIN TODAY. INCREASING DIFFERENTIAL CYCLONIC VORTICITY WILL REPLACE THE DRY SLOT. THICKNESSES COLLAPSE BELOW 540DM CWA WIDE THIS AFTERNOON...BUT BOUNDARY LAYER TEMPS/DEW POINTS AND WET BULB CONSIDERATIONS POINT TO A CLOSE CALL ON PRECIP TYPE...MIXY PER GOING FORECAST IN THE WEST. THE EAST LOOKS TO BE WARM ENOUGH TO SUPPORT RAIN WITH PRECIP POTENTIAL HOLDING OFF UNTIL MID TO LATE AFTERNOON. TONIGHT- DIFFERENT STORY AS BOUNDARY LAYER COOLS. NEARLY STACKED SYSTEM TRAVERSES THE AREA WITH MODEST 850-700MB Q VECTOR CONVERGENCE. 700-300MB Q VECTOR CONVERGENCE SHOWS A WEAKENING SIGNAL. NEVERTHELESS EXPECT A GOOD COVERAGE OF SNOW SHOWERS WITH END LIKELY REASONABLE AT THIS POINT. ACCUMS LOOK MINOR ON GRASSY SURFACES. SATURDAY- MODEL CONSENSUS IS TO TAKE UPPER LOW FROM EASTERN WISCONSIN INTO NORTHERN LOWER MICHIGAN BY 00Z SUNDAY. 850 MILLIBAR AND SURFACE TROUGH WILL AID CONTINUED VERTICAL MOTION DURING THE DAY. THICKNESSES AND 850 TEMPERATURES SUGGEST SNOW...THOUGH BOUNDARY LAYER LIKELY TO WARM TO SUPPORT AN EVENTUAL MIX. THIS PLAYED OUT IN THE GOING GRIDS. SUNDAY- SECONDARY SHORT WAVE IN NW UPPER FLOW ARRIVES WITH 850 MILLIBAR COLD AIR ADVECTION UNDERWAY. MOISTURE AND LIFT APPEAR CONFINED TO NORTHERN CWA...NORTH OF SHORTWAVE TRACK. NAM IS DRY AND GFS WITH SOME LIGHT QPF...AGAIN MAINLY NORTH OF VORT TRACK. MONDAY- RIDGING LOOKS DOMINANT THOUGH GFS HINTING AT INCREASING 850 WARM AIR/MOISTURE ADVECTION LATER IN THE DAY WITH LIGHT QPF SPREADING INTO THE SOUTHWEST CWA. HOWEVER...GFS VORT PATTERN LOOKS TO BE SHOVING TOO MUCH VORTICITY ADVECION INTO THE RIDGE AXIS. FOR NOW WILL LEAN TOWARDS MEX MOS POPS AND LEAVE MONDAY DRY. TUESDAY- 00Z ECMWF HAS TRENDED THE SOUTHERN SYSTEM FURTHER SOUTH THAN THE 12Z RUN...THOUGH OVERALL THE TREND OF THE ECWMF HAS BEEN TO KEEP THIS STORM SYSTEM TO OUR SOUTH...MOST CONSISTENT OVER THE LONG HAUL. MORE FLIP FLOPPING FROM THE GFS BUT NORTHWARD TREND IN LAST SEVERAL RUNS IS A CONCERN. FOR NOW WILL GO WITH CONSENSUS FROM SURROUNDING OFFICES AND LEAVE THIS PERIOD DRY FOLLOWING CLOSER TO THE MORE CONSISTENT ECMWF SOLUTION. && .AVIATION...DRY SLOT OVER SOUTHEAST WISCONSIN EARLY THIS MORNING WILL FILL IN AS UPPER LOW PUSHES EAST INTO WISCONSIN. VFR CIGS INITIALLY BUT SOME MVFR CIGS AS CORE OF UPPER LOW REACHES CENTRAL WISCONSIN. STEEP LOW LEVEL LAPSE RATES SHOULD ALLOW FOR SCATTERED RAIN OR SNOW SHOWERS DURING THE AFTERNOON...WITH SOME MVFR VSBYS. && .MARINE...SURFACE PRESSURE GRADIENT EASING FOR A TIME TODAY. AS SURFACE LOW MOVES TOWARD THE UPPER GREAT LAKES PRESSURE GRADIENT WILL TIGHTEN AGAIN BY EVENING. WITH STEEP LAPSE RATES WINDS SHOULD MIX DOWN AND REACH SMALL CRAFT ADVISORY CONDITIONS AGAIN BY EVENING. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST SUNDAY FOR LMZ643>646. && $$ SHORT/LONG TERM...PC AVIATION/MARINE...SH