Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 220240
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
840 PM CST FRI NOV 21 2014

.UPDATE...
THE LEADING EDGE OF THE PRECIP ACROSS IOWA CONTINUES TO EVAPORATE
AS IT HITS THE VERY DRY AIR IN PLACE ACROSS THE REGION. DEWPOINTS
OVER SOUTHERN WISCONSIN ARE IN THE SINGLE DIGITS TO LOWER TEENS
AND RISE ONLY SLOWLY TO THE SOUTH. IR SATELLITE IMAGERY SHOWS A
NICELY DEFINED MID LEVEL SHORT WAVE OVER IOWA...FCST TO LIFT
ACROSS SRN WISCONSIN TONIGHT...EXITING TO THE EAST BY AROUND 12Z
SATURDAY. THE HRRR RADAR DEPICTION HAS BEEN SHOWING A RATHER
UNIMPRESSIVE PRECIP PATTERN FOR SOUTHERN WISCONSIN OVERNIGHT...
SCATTERED IN COVERAGE AND STAYING MOSTLY SOUTH AND EAST OF
MADISON. THE NEW 00Z NAM IS HEADED THAT WAY AND KEEPS THE BULK OF
THE PRECIP SOUTH OF A DODGEVILLE TO PORT WASHINGTON LINE.

ROAD SENSOR DATA SHOWS PAVEMENT TEMPERATURES GENERALLY IN THE MID
TO UPPER 20S F. AIRCRAFT SOUNDER DATA IS ALREADY SHOWING THE WARM
LAYER ALOFT PUSHING INTO SOUTHERN WISCONSIN...SO THAT SHOULD BE
IN PLACE AND STRONG ENOUGH TO ENSURE THE PRECIP TYPE WILL BE
FREEZING RAIN ONCE THE PRECIP GETS HERE. THE BASE OF THAT LAYER IS
AROUND 3KFT RIGHT NOW.

CONFIDENCE IN THE ADVISORY NORTH OF MADISON IS VERY SHAKY RIGHT
NOW...BUT EVEN A MODERATE AMOUNT OF LIGHT DRIZZLE IN A QUICKLY
MOISTENING BOUNDARY LAYER COULD CAUSE PROBLEMS VERY QUICKLY. THE
ADVISORY LOOKS GOOD SOUTH AND EAST OF MADISON WHERE THERE IS
BETTER CONFIDENCE THERE WILL BE A BIT MORE PRECIP. WILL STAY THE
COURSE FOR NOW OUT OF AN ABUNDANCE OF CAUTION.

TEMPERATURES WILL RISE ABOVE FREEZING SHORTLY AFTER SUNRISE...BUT
PAVEMENT TEMPERATURES MAY LAG THAT AND STILL BE A PROBLEM THROUGH
MID MORNING. THEREAFTER...ALL TEMPS SHOULD SUPPORT RAIN/WET ROADS.

&&

.AVIATION/06Z TAFS/...
LOOK FOR CONDITIONS TO STEADILY DETERIORATE WITH RESPECT TO CIGS
OVERNIGHT. GENERALLY IFR CONDITIONS SHOULD OVERSPREAD THE AREA BY
SUNRISE. AN AREA OF FREEZING RAIN IS EXPECTED ACROSS SOUTHEAST
WISCONSIN...MAINLY BETWEEN ABOUT 2 AM AND 7 AM. AIR TEMPERATURES
THEREAFTER SHOULD BE ABOVE FREEZING...BUT PAVEMENT TEMPERATURES
MAY BE LAGGING BY A FEW HOURS. MADISON MAY ONLY SEE A BRIEF PERIOD
OF FREEZING RAIN AROUND MIDNIGHT WITH PATCHY FREEZING DRIZZLE
POSSIBLE AFTER THAT UNTIL TEMPS WARM ABOVE FREEZING AFTER
SUNRISE.

CIGS MAY BRIEFLY IMPROVE TO MVFR CONDITIONS SATURDAY
AFTERNOON...THEN DROP BACK TO IFR AS MOISTURE STREAMS NORTH INTO
THE AREA AHEAD OF A DEVELOPING LOW PRESSURE TO THE SOUTH AND WEST.

LOW LEVEL WIND SHEAR EXISTS THROUGH ABOUT SUNRISE SATURDAY.

&&

.MARINE...

A SMALL CRAFT ADVISORY CONTINUES THROUGH SUNDAY MORNING DUE TO A
TIGHT PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE EASTERN
GREAT LAKES AND LOW PRESSURE APPROACHING FROM THE NORTHERN PLAINS.

&&

.PREV DISCUSSION... /ISSUED 349 PM CST FRI NOV 21 2014/

SHORT TERM...

TONIGHT...FORECAST CONFIDENCE HIGH.

FREEZING RAIN WILL SPREAD INTO SOUTH CENTRAL WI BY LATE EVENING AND
INTO SOUTHEAST AND EAST CENTRAL WI AROUND MIDNIGHT. THERE IS A
FREEZING RAIN ADVISORY IN EFFECT FOR THE LATE EVENING TO SATURDAY
MORNING HOURS. SOUTHERN WI IS VERY DRY RIGHT NOW WITH SUNSHINE...
BUT THE LOW LEVEL MOISTURE WILL BE ADVECTING INTO THE AREA QUICKLY
THIS EVENING.

WEAK SHORTWAVE ENERGY AND PERSISTENT LOW LEVEL MOISTURE AND WARM AIR
ADVECTION WILL CREATE MODERATE UPWARD MOTION /OMEGA/ OVER SOUTHERN
WI THROUGH MUCH OF THE NIGHT. THE MID LEVELS WILL SATURATE SHORTLY
AFTER THE LOW LEVELS. THIS MEANS WE WILL HAVE A DEEP MOISTURE
PROFILE WITH A WARM LAYER FROM 2 TO 7 KFT WITH A MAX TEMP ALOFT OF
+4C. MEANWHILE... SURFACE TEMPS WILL REMAIN BELOW FREEZING THROUGH
MUCH OF THE NIGHT.

SINCE WE HAVE BEEN IN A COLD PATTERN... BELOW FREEZING FOR THE PAST
10 DAYS... THE GROUND TEMPERATURES ARE BELOW FREEZING. THIS WILL
ALLOW ANY LIQUID TO FREEZE ON CONTACT AND CREATE GLAZED SURFACES.
EXPECT SLIPPERY CONDITIONS ON SIDEWALKS AND UNTREATED ROADS.

THE 12Z MODELS CAME IN WITH SLIGHTLY HIGHER QPF AMOUNTS... SO WE
INCREASED ICE ACCUMULATION AMOUNTS TO UP TO 0.15 INCH IN SOUTHEAST
WI WITH LOWER AMOUNTS ELSEWHERE.

THE UNCERTAINTY FOR TONIGHT IS HOW LOW THE TEMPS WILL DROP AND HOW
LONG THEY WILL REMAIN BELOW FREEZING. THE MODELS ARE STARTING TO
SHOW A SLIGHTLY WARMER TREND. THIS WOULD IMPACT ICE ACCUMULATION
AMOUNTS.

SATURDAY...FORECAST CONFIDENCE HIGH.

TEMPS WILL GRADUALLY WARM ABOVE FREEZING AS THE RAIN TAPERS OFF
SATURDAY MORNING. THE MID LEVELS DRY OUT...BUT THE LOW LEVEL
MOISTURE WILL LINGER THROUGH THE DAY. EXPECT LOW CLOUDS... PERIODS
OF DRIZZLE AND SOME PATCHY FOG WITH TEMPS WARMING INTO THE LOWER
40S.

SATURDAY NIGHT THROUGH TUESDAY...FORECAST CONFIDENCE MEDIUM.

SLY FLOW AND LOW LEVEL WARM...MOIST ADVECTION WILL INCREASE SAT NT
AHEAD OF A TROUGH OF LOW PRESSURE APPROACHING FROM THE PLAINS.
THUS LIGHT RAIN CHANCES AND/OR DRIZZLE WILL INCREASE THROUGHOUT
THE NIGHT. THE RELATIVELY MILD AND MOIST AIR FLOWING OVER A FROZEN
GROUND WILL AID IN SOME FOG DEVELOPMENT.

FOR SUNDAY...A STRONG SHORTWAVE TROUGH OVER E TX WILL LIFT NEWD
TO THE OHIO RIVER VALLEY BY 00Z MON WHILE A LARGER SCALE UPPER
TROUGH MOVES EWD ACROSS THE NRN PLAINS. STRONG CYCLOGENESIS WILL
RESULT FROM CENTRAL IL TO ERN UPPER MI FROM SUN AFTERNOON THROUGH
12Z MON. THE STRONG LOW WILL TRACK NORTH OVER WRN LOWER MI WITH
PWS INCREASING TO ONE INCH OVER WI. THE DEEP QG DYNAMICS AND
FRONTOGENESIS WILL LEAD TO WIDESPREAD MDT RAIN FOR SUN AFTERNOON
AND NIGHT. AS THE RAIN DIMINISHES LATE SUN NT AND EARLY MON AM...A
CHANGE TO LGT SNOW IS EXPECTED WITH LITTLE TO NO SNOW
ACCUMULATION. THE AFOREMENTIONED UPPER TROUGH TO THE WEST WILL
THEN PASS MON AFTERNOON AND NIGHT WITH A SECONDARY COLD FRONT FOR
MON NT. THIS WILL BRING CONTINUED CHANCES OF LGT SNOW THAT COULD
LINGER INTO TUE AM OVER ERN WI. OVERALL RAINFALL DURING THIS TIME
SHOULD REACH ONE INCH.

LONG TERM...TUESDAY AFTERNOON THROUGH FRIDAY...FORECAST
CONFIDENCE MEDIUM.

HIGH PRESSURE WILL SETTLE OVER THE AREA BY LATE TUE INTO WED AM. A
LARGE SCALE UPPER TROUGH WILL THEN DIG SEWD FROM CANADA...INTO THE
GREAT LAKES AND EVENTUALLY ALL OF THE ERN USA. THIS WILL BRING
CHANCES OF LIGHT SNOW WED AND WED NT WITH STRONG COLD ADVECTION TO
FOLLOW. POLAR HIGH PRESSURE THEN EXPECTED BY LATE THU INTO FRI
WITH VERY COLD TEMPS ONCE AGAIN.

AVIATION/00Z TAFS/...LOW LEVEL CLOUDS WILL MOVE IN FROM THE SOUTHWEST
THIS EVENING. CEILINGS WILL DROP TO MVFR LATE THIS EVENING AT MSN
AND AROUND MIDNIGHT AT EASTERN TAF SITES...AN HOUR OR TWO AHEAD OF
FREEZING RAIN ONSET. EXPECTING FREEZING RAIN TO START AT MSN
AROUND MIDNIGHT AND AN HOUR LATER AT EASTERN TAF SITES. THE
MAJORITY OF THE FREEZING RAIN SHOULD END AROUND SUNRISE SATURDAY.
EXPECTING UP TO 0.15 INCHES OF ICE ACCUMULATION AT MKE AND ENW AND
UP TO 0.10 AT MSN AND UES. HIGH CONFIDENCE OF AT LEAST SOME ICE
ACCUMULATION AT ALL TAF SITES. WINDS AT 2000 FT EXPECTED TO BE 40
TO 45 KTS DURING THE NIGHT. NO MENTION OF WIND SHEAR WITH GUSTS UP
TO 20 KTS EXPECTED AT THE SURFACE.

PATCHY DRIZZLE OR PATCHY FREEZING RAIN EXPECTED FOR A COUPLE HOURS
AFTER SUNRISE SATURDAY BEFORE A CHANGEOVER TO PATCHY DRIZZLE DURING
THE LATE MORNING. PATCHY DRIZZLE EXPECTED TO CONTINUE THROUGH THE
DAY WITH CEILINGS UNDER 1000 FT POSSIBLE LATE SATURDAY AFTERNOON AND
INTO THE EVENING. SOME UNCERTAINTY WITH THE TIMING OF THESE LOWER
CEILINGS.

MARINE...THE SMALL CRAFT ADVISORY REMAINS IN EFFECT UNTIL 6 AM SUNDAY. A
TIGHT PRESSURE GRADIENT WILL DOMINATE THE REGION WITH HIGH PRESSURE
TO THE SOUTHEAST AND LOW PRESSURE TO THE NORTHWEST. FREEZING RAIN
EXPECTED AFTER MIDNIGHT THROUGH SUNRISE WITH DRIZZLE DURING THE DAY
ON SATURDAY.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 9 AM CST SATURDAY FOR WIZ046-047-
     056-057-062-063-067>069.

     FREEZING RAIN ADVISORY FROM 1 AM TO 10 AM CST SATURDAY FOR
     WIZ051-052-058>060-064>066-070>072.

LM...SMALL CRAFT ADVISORY UNTIL 6 AM CST SUNDAY FOR LMZ643>646.

&&

$$

UPDATE...DAVIS
TONIGHT/SATURDAY AND AVIATION/MARINE...SM
SATURDAY NIGHT THROUGH FRIDAY...GEHRING


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