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
