Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 232044
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
244 PM CST TUE DEC 23 2014

.TONIGHT...FORECAST CONFIDENCE - MEDIUM.

PARTIAL CLEARING MAY STICK AROUND FOR A TIME IN THE FAR SOUTHEAST
WHERE KENW ENJOYED SOME AFTN SUN AND MILDER TEMPS.  FARTHER
NORTHWEST...SFC LOW OVER CENTRAL WI WILL REMAIN NEARLY STATIONARY
WHILE WEAKENING AS SHORT WAVE RIDGING TO THE NORTH OF DEEPING SRN
PLAINS LOW OVERWHELMS WI CIRCULATION.  EXPECT CLOUDS AND OCCASIONAL
-RA OR -DZ TO CONTINUE CLOSER TO LINGERING CIRCULATION OVER THE
NORTHWEST.  LATEST VSBL IMAGERY SHOWING LOW CLOUDS CONTINUE TO
BREAKUP OVER FAR SOUTHEAST WI INTO NRN IL.  THIS PARTIAL CLEARING WL
LIKELY AFFECT MORE OF SOUTHEAST WI THROUGH THE EVE.

WEAK CONVERGENCE IN VICINITY OF FILLING LOW PRESSURE WL LIKELY CUASE
SOME PATCHY -RA OR -DZ.  TEMPS EXPECTED TO REMAIN AT OR ABOVE
FREEZING SO FREEZING DRIZZLE NOT A CONCERN. DIMINISHING WINDS WL
ALLOW FOG TO DEVELOP.  IF CLEARING BECOMES MORE WIDESPREAD IN THE
EAST...THEN DENSE FOG MAY BE AN ISSUE LATE TNGT.

.WEDNESDAY...FORECAST CONFIDENCE - LOW.

12Z NAM AND GFS TRENDING NORTHWEST WITH STRONGER FORCING ASSOCIATED
WITH LOW PRESSURE EXPECTED TO UNDERGO CYCLOGENESIS AS IT MOVES FROM
THE LOWER MS RIVER VALLEY INTO THE CENTRAL GTLAKES ON WED/WED NGT.
STRONG LAYER Q-VECTOR CONVERGENCE OF 20 TO 40 UNITS GRAZES SOUTHEAST
WI FROM 18Z NAM WED AFTN.

SHORT TERM GUIDANCE STILL SHOWING A VARIETY OF SPECIFICS WITH
REGARDS TO AMOUNT OF QPF AND FORCING AS THIS SYSTEM AFFECTS
SOUTHEAST WI...MAINLY WED AFTN AND EARLY EVE. 18Z NAM NOW TRENDING
SLIGHTLY TO THE EAST WITH 12Z BUT STILL SHOWS QPF BETWEEN ONE
QUARTER AND FOUR TENTHS INCH. GFS HAS BEEN MORE CONSISTENT WITH SFC
AND ELEVATED FEATURES BUT APPEARS TO BE ON THE FAST SIDE IN BRINGING
PRECIP INTO SOUTHEAST WI WED MRNG.  MEANWHILE...HI RES ECMWF
TRENDING FARTHER EAST WITH QPF LESS THAN ONE TENTH INCH.

DUE TO ABUNDANT UNCERTAINTIES...PARTICIPATED IN CONFERENCE CALL WITH
WEATHER PREDICATION CENTER AND NWS OFFICES TO THE SOUTH.  AGREED TO
TREND AWAY FROM WETTER NAM OUTLIER BUT NOT AS DRY AS ECMWF.  HENCE
MODEL BLEND WITH BETWEEN ONE TENTH AND ONE QUARTER INCH QPF IN THE
SOUTHEAST.  FORECAST SOUNDINGS AND CRITICAL THICKNESSES SHOW LOW
LEVELS COOLING AS PRECIP INTENSITY INCREASES DURING THE AFTN DUE TO
DYNAMICAL PROCESSES WITH THIS STRENGTHENING SYSTEM.  DESPITE
DIFFERENCES...BOTH NAM AND GFS DO SHOW A BURST OF MODERATE TO STRONG
FRONTOGENETIAL FORCING TIED TO NEGATIVE EPV IN THE DENDRITIC GROWTH
ZONE FOR SEVERAL HOURS.  WITH SNOW-LIQUID RATIOS AROUND 10 TO 1
DURING THE PEAK LIFT...EXPECT A RAIN/SNOW MIX TO TRANSITION TO WET
SNOW WITH SEVERAL INCHES OF QUICK ACCUMULATION IN THE SOUTHEAST. DUE
TO THIS BURST OF SNOW OCCURRING IN THE AFTN PRIOR TO XMAS EVE...WL
ISSUE WINTER WX ADVY FOR THREE SOUTHEAST COUNTIES...WHICH LINES UP
WELL WITH NORTHEAST IL ADVY...FOR 1 TO 3 INCH ACCUMULATIONS.
EVE/MIDNIGHT SHIFT CAN ADJUST ADVY ACCORDINGLY AS SHORT TERM
GUIDANCE COMES INTO BETTER AGREEMENT.

PAVEMENT TEMPS LIKELY TO BE SLIGHTLY ABOVE FREEZING DURING BURST OF
SNOW WED AFTN...SO INITIAL MELTING OF SNOW WL YIELD TO SOME SLUSHY
ACCUMULATIONS.  AS FORCING WITH UPPER LOW EXITS TO THE EAST XMAS
EVE...WL TREND TOWARD SNOW ENDING DURING THE EVENING WITH ADDITIONAL
LIGHT ACCUMULATIONS UP TO 03Z.

.CHRISTMAS DAY...FORECAST CONFIDENCE IS HIGH.

HIGH PRESSURE CENTERED OVER THE GULF COASTAL STATES WILL STRETCH
ITS AXIS UP INTO THE GREAT LAKES FOR CHRISTMAS...BRINGING A DRY
AND RATHER PLEASANT DAY WITH HIGHS IN THE MID TO UPPER 30S.

.FRIDAY AND FRIDAY NIGHT...FORECAST CONFIDENCE IS HIGH.

A WEAK LOW PRESSURE TROF AND COLD FRONT IS FORECAST TO PUSH INTO
WISCONSIN DURING THE DAY. THE BEST SATURATION AND FORCING STAYS
MOSTLY NORTH OF THE FORECAST AREA DURING THE DAY...BUT THERE IS A
SLIGHT CHANCE OF A RAIN/SNOW MIX NORTH OF MILWAUKEE AND MADISON.
AS THE TROF MOVES THROUGH OVERNIGHT...THE BETTER SATURATION
ARRIVES AND THIS COULD RESULT IN SOME VERY LIGHT PRECIP. GIVEN
TEMPS...IT WOULD BE A RAIN/SNOW MIX TRANSITIONING OVER TO ALL
LIGHT SNOW. ANY SNOW ACCUMS WILL BE VERY LOW...WELL BELOW 1/2
INCH.

.SATURDAY THROUGH TUESDAY...FORECAST CONFIDENCE IS HIGH.

IT LOOKS LIKE HIGH PRESSURE WILL GENERALLY DOMINATE THROUGH THIS
PERIOD WITH THINGS LOOKING VERY DRY OVERALL. THERE ARE HINTS OF A
FEW WEAK WAVES PASSING BY...BUT NOT ENOUGH CONFIDENCE TO GO
AGAINST HIGH AND DRY.

&&

.AVIATION/00Z TAFS/...

EXPECT STRATUS TO CONTINUE TO AFFECT WESTERN TAF SITES AND GRADUALLY
ADVANCE BACK INTO SOUTHEAST WI OVERNIGHT AS LOW LEVEL WINDS BECOME
MORE NORTH TO NORTHWEST.  HOWEVER WL LIKELY HOLD OFF FOR A WHILE FOR
THE CIGS TO RETURN TO KENW. PARTIAL CLEARING MAY AFFECT KMKE/KUES
FOR A PORTION OF THE EVENING AS VSBL IMAGERY SHOWING LOW CLOUDS
FURTHER ERODING TOWARD KBUU.

KMSN LIKELY TO EXPERIENCE SOME DRIZZLE AT TIMES BUT TEMPS TO REMAIN
AT OR ABOVE FREEZING SO NO -ZL EXPECTED.  SOUTHEAST WI LIKELY GET
GRAZED BY DEEPENING LOW PRESSURE PASSING TO THE SOUTHEAST ON WED.
THIS WILL BRING A RAIN/SNOW MIX CHANGING OVER TO SNOW DURING THE DAY
WITH SOME SLUSHY ACCUMULATIONS LIKELY.

&&
.MARINE...

BASED ON OBSERVED WINDS AND WEB CAMS ALONG THE LAKE...IT LOOKS
LIKE WE CAN CANCEL THE SMALL CRAFT ADVISORY THAT WAS IN EFFECT
UNTIL 6 PM THIS EVENING. NEXT UP...LOW PRESSURE PASSING TO OUR
EAST WEDNESDAY INTO WEDNESDAY NIGHT WILL BRING BRISK/GUSTY
NORTHWEST WINDS THAT WILL LIKELY MEET SMALL CRAFT ADVISORY
CRITERIA. WILL THEREFORE POST AN ADVISORY FROM 3 PM WEDNESDAY
THROUGH NOON ON THURSDAY. THE OFF SHORE WINDS WILL PUT THE HIGHEST
WAVES OUT TOWARD OPEN WATER.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY FROM NOON TO 9 PM CST WEDNESDAY FOR
     WIZ066-071-072.

LM...SMALL CRAFT ADVISORY FROM 3 PM WEDNESDAY TO NOON CST THURSDAY
     FOR LMZ643>646.

&&

$$

TONIGHT/WEDNESDAY AND AVIATION/MARINE...MBK
WEDNESDAY NIGHT THROUGH TUESDAY...DAVIS


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