FXUS63 KMKX 060228
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
828 PM CST SAT DEC 5 2009
.UPDATE...
18Z NAM AND GFS BACKED OFF ON QPF FOR SUNDAY NIGHT AND MONDAY. BETTER
QPF NORTHERN AREAS FROM DELLS TO SHEBOYGAN. ONLY 0.01 LIQUID QPF
AT MILWAUKEE AND 0.03 AT MADISON OFF 18Z NAM...BUT 0.20 NORTH
TOWARD SHEBOYGAN. 0.10 AT MILWAUKEE AND 0.17 AT MADISON OFF GFS.
NEW 00Z NAM IS BACK TO AMOUNTS LIKE 12Z RUNS...A BIT SLOWER...AND IS
FARTHER SOUTH WITH THE BETTER QPF. NOW WELL ACROSS MOST OF OUR
ENTIRE FORECAST AREA. MAX 0.25 INCH QPF IN A SW TO NE BAND FROM
LAFAYETTE COUNTY TO OZAUKEE COUNTY...WITH THE LESSER AMOUNTS
NORTHWEST TOWARD THE DELLS AND FAR SE BY KENOSHA. WITH SNOW RATIOS
THIS IS STILL IN THE 2 TO 4 INCH RANGE. IF NEW GFS FOLLOWS...THEN
A SLIGHT SOUTHWARD SHIFT IN THE SNOW TOTALS MAY BE NEEDED.
&&
.PREV DISCUSSION... /ISSUED 353 PM CST SAT DEC 5 2009/
SHORT TERM /TONIGHT THROUGH TUESDAY/...
TONIGHT...CONFIDENCE: MEDIUM
WEAK WARM AIR ADVECTION AND VORTICITY ADVECTION AHEAD OF SHEARED
VORT...CURRENTLY OVER SERN S DAKOTA ON WATER VAPOR LOOPS...DEVELOPS
LAYER Q VECTOR MAX THAT CONTINUES TO TARGET CENTRAL AND NORTHERN
WISCONSIN TONIGHT. FORCING GENERATES LIGHT QPF JUST TO THE NORTH
SIDE OF SURFACE TROUGH AS IT SAGS THROUGH THE STATE. WILL KEEP
SLIGHT CHANCE SNOW SHOWERS IN THE VICINITY OF Q VECTOR MAX AND LOWER
CONDENSATION PRESSURE DEFICIT MAX ACROSS NRN SECTIONS OF CWA FOR
OVERNIGHT. BUFKIT FORECAST SOUNDINGS FOR OSHKOSH INDICATE PERIOD OF
ELEVATED SATURATION AND LIFT WILL ONLY LAST FOR AN HOUR OR TWO.
SUNDAY...CONFIDENCE: HIGH.
WEAK SURFACE TROUGH TO BISECT CWA WITH SOUNDINGS SHOWING MIXING UP
TO -6C 925 MB YIELDING LOW 30 HIGHS...WITH INCREASING CLOUDS AHEAD
OF NEXT SHORT WAVE.
SUNDAY NIGHT AND MONDAY...CONFIDENCE: MEDIUM.
NEXT ACCUMULATING SNOW COMES SUNDAY NIGHT INTO MONDAY AS MODELS
COMING INTO SOME AGREEMENT ON A TRACK ACROSS NRN IL. AXIS OF
HEAVIEST QPF LIES ACROSS EITHER NRN CWA/CENTRAL WI...OR THROUGH THE
HEART OF THE CWA DEPENDING ON MODEL. Q VECTOR AND FRONTOGENETIC
FORCING ON 18Z SAT RUNS ARE INDICATING BEST SNOW MAY SHIFT CLOSER TO
IL BORDER. ALSO...PERIOD OF NORTHEAST WINDS MAY BRING SOME LAKE
ENHANCEMENT TO LAKESHORE COUNTIES. MAX SNOW AMOUNTS ARE LOW END
ADVISORY SO ISSUED AN SPS TO HIGHLIGHT POTENTIAL AND LET NIGHT CREW
DECIDE WHERE AND IF AN ADVISORY MAY BE NEEDED.
MONDAY NIGHT AND TUESDAY...CONFIDENCE: HIGH.
HIGH PRESSURE DRIFTS ACROSS REGION WITH DRY WEATHER AND COLD LOWS IN
THE TEENS. INCREASING CLOUDS WITH HIGHS IN THE 20S AS STRONG LOW
APPROACHES FROM THE SOUTHERN PLAINS.
LONG TERM/TUESDAY NIGHT THROUGH SATURDAY/...
TUESDAY NIGHT THROUGH WEDNESDAY...CONFIDENCE: MEDIUM
00Z MID RANGE MODELS DIFFERED ON TRACK OF DEEPENING LOW...WITH ECMWF
AND CANADIAN FARTHER SOUTH THAN GFS. 12Z RUNS COMING INTO BETTER
AGREEMENT WITH A ST LOUIS...DANVILLE IL...TO LK HURON TRACK. WHILE
TRACK MAY FLUCTUATE BETWEEN NOW AND TUESDAY...AND HAS IMPORTANT
IMPLICATIONS FOR PCPN AMOUNTS AND A CHANCE FOR A MIX FOR SRN
WI...CONFIDENCE IS IN THE MID RANGE THAT THERE WILL BE A GREATER
THAN 5 INCH SNOWFALL FOR A PORTION OF SRN WI BEGINNING TUESDAY
AFTERNOON/EVENING THROUGH THE DAY WEDNESDAY...WITH BLOWING AND
DRIFTING WEDNESDAY AS TIGHT PRESSURE GRADIENT PASSES OVER WISCONSIN
WITH SFC LOW FALLING AROUND 10 MB BETWEEN 12Z WED AND 00Z THU.
FOLLOWING THE FAVORED AND SOMEWHAT CONSISTENT ECMWF WHICH GIVES SRN
WI ALL SNOW. NOT MUCH OF A DIURNAL CHANGE OF TEMPERATURES FROM TUE
AFTERNOON THROUGH MIDDAY WED...THEN TEMPS FALL WITH STRONG CAA
BEHIND LOW.
WEDNESDAY NIGHT THROUGH THURSDAY...CONFIDENCE: MEDIUM.
COLDEST TEMPERATURES SO FAR THIS SEASON EXPECTED BEHIND SYSTEM WITH
THE MORE NORTHERLY GFS STRONGER WITH COLD ADVECTION BEHIND SYSTEM.
TWEAKED HPC GUIDANCE NUMBERS WHICH TREND WELL WITH GFS ENSEMBLE MOS
AND WHILE NOT AS COLD AS 2 METER TEMPS STILL BRING SINGLE DIGIT LOWS
FOR WEDNESDAY AND THURSDAY NIGHTS.
FRIDAY AND SATURDAY...CONFIDENCE: LOW.
WITH SHARPER SHORT WAVE TROUGH AND ECMWF BRINGS PCPN INTO SRN WI
FRIDAY WITH GOOD ISENTROPIC LIFT ON 850 MB WAA AND 850 LOW TRACKING
ACROSS WI/IL BORDER...WHILE GFS IS WEAKER WITH ADVECTION AND LIFT
AND ONLY SHOWS A NARROW BAND OF PCPN ACROSS THE WI/IL BORDER. WILL
GO WITH SLIGHT CHANCE SNOW. BOTH MODELS SHOW HI PRESSURE FOR
SATURDAY. AGAIN FOLLOWED COOLER HPC GUIDANCE NUMBERS FOR TEMPS.
AVIATION...VFR CIGS WILL RETURN TONIGHT IN STRONG WARM AIR
ADVECTION. THERE COULD BE ENOUGH MID LEVEL MOISTURE RETURN AND
FORCING TO CAUSE ISOLD TO SCT -SHSN BUT IT IS EXPECTED PRIMARILY
NORTH OF MSN/UES/MKE. MODELS HAVE BACKED OFF ON WIND SHEAR POTENTIAL
FOR TONIGHT...WITH ONLY SW 30 KTS AROUND 2000FT AND AROUND 10KT AT
SFC.
NEXT AVIATION CONCERN WILL BE LOWERING CIGS SUN AFTERNOON AT MSN AND
SUN NIGHT ELSEWHERE AS A SFC LOW PRESSURE SYSTEM APPROACHES THE
MIDWEST. SNOW IS EXPECTED TO SPREAD ACROSS THE REGION AFTER MIDNIGHT
SUNDAY NIGHT.
MARINE...INCREASING SW LOW LEVEL WINDS TNGT TO 20 TO 30KTS JUST OFF
SURFACE MAY BE ABLE TO MIX DOWN TO LAKE SURFACE DUE TO STEEP LAPSE
RATE IN THE VERY LOW LEVELS. WINDS WILL APPROACH SMALL CRAFT ADVY
CONDITIONS...BUT ARE NOT EXPECTED TO EXCEED THEM TONIGHT. SMALL
CRAFT CONDITIONS WILL AGAIN BE APPROACHED WITH NORTHWEST WINDS ON
THE BACK SIDE OF LOW PRESSURE ON MONDAY.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
SHORT/LONG TERM...06
AVIATION/MARINE...06
