Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 021822 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1222 PM CST TUE FEB 2 2016

.UPDATE...

THUNDERSNOW IS ONGOING OVER THE WESTERN FORECAST AREA... INCLUDING
MADISON AND WISCONSIN DELLS. THIS IS PRODUCING HEAVY SNOWFALL
RATES OF AN INCH PER HOUR OR GREATER. HEAVIEST HIT SO FAR PER
WEBCAMS AND SURFACE OBS IS SAUK COUNTY. PRECIP TYPE WITH THE
NORTHWESTERN FORECAST AREA... FROM MONROE TO MADISON TO JUNEAU TO
FOND DU LAC AND SHEBOYGAN...IS ALL SNOW.

IN SOUTHEAST WI... DRY AIR ATE UP ALL OF THE 700MB WARM AIR
ADVECTION EARLY THIS MORNING. ROUND TWO WITH THE 850MB WARM AIR
ADVECTION... DRY AIR IS ALSO EATING UP SOME OF THAT PRECIP AT THE
ONSET LATE THIS MORNING. EXPECT SOUTHEAST WI TO FILL IN QUICKLY WITH
PRECIP AT THIS NOON HOUR. PRECIP TYPE IS QUESTIONABLE. MOST AREAS
SHOULD SEE RAIN... ALTHOUGH DO NOT BE SURPRISED TO SEE SNOW AND
SLEET MIXED IN ESPECIALLY EARLY THIS AFTERNOON. PRECIP WILL
DEFINITELY CHANGE TO ALL RAIN IN SOUTHEAST WI BY 2 PM INCLUDING
WAUKESHA AND MILWAUKEE.

THE NOSE OF THE 850MB LOW LEVEL JET AND WARM FRONT ARE GENERATING
SHOWERS AND THUNDERSTORMS IN NORTH CENTRAL AND NORTHEAST IL. THE
HRRR MODEL IS CAPTURING THIS WELL AND BRINGS CONVECTION INTO
SOUTHEAST WI EARLY THIS AFTERNOON. THUNDER IS IN THE FORECAST AND
THIS SHOULD OCCUR BETWEEN NOON AND 3 PM BEFORE THE STRONG FORCING
SLIDES OFF TO THE EAST. PRECIP TYPE WITH THIS THUNDER WILL BE RAIN
FOR MILWAUKEE DOWN TO KENOSHA. THERE COULD BE A LITTLE SLEET MIXED
IN A LITTLE FURTHER INLAND FOR WAUKESHA AND BURLINGTON.

THE DRY SLOT WILL MARCH INTO SOUTH CENTRAL AND SOUTHEAST WI BETWEEN
4 PM AND 7 PM THIS AFTERNOON. REGIONAL RADAR IS SHOWING THAT THIS IS
A PROMINENT DRY SLOT AND THERE IS A GOOD CHANCE FOR DRY WEATHER
BENEATH IT. THAT SAID... WINDS WILL DIMINISH AS THE SURFACE LOW
TRACKS OVERHEAD SO WE CAN EXPECT AREAS OF FOG... POSSIBLY DENSE...
AND VERY LOW CLOUDS IN THE MIDDLE OF THE NIGHT.

LIGHT SNOW FROM THE WRAP-AROUND REGION OF THE SPRAWLING LOW PRESSURE
SHOULD HOLD OFF UNTIL EARLY WEDNESDAY MORNING FOR SOUTHERN WI.

&&

.AVIATION/18Z TAFS/...

THUNDERSNOW IN MADISON WILL BE WINDING DOWN BY 130 PM/1930Z. PRECIP
WILL CHANGE TO RAIN BETWEEN 2 AND 4 PM/ 20-22Z. MSN IS RIGHT ON THE
CUTOFF FOR RAIN AND SNOW TODAY... SO THERE IS LOW CONFIDENCE.

SOUTHEAST WI IS NOW FILLING IN WITH SNOW AND RAIN. EXPECT MAINLY
RAIN FOR MKE AND ENW TODAY. THUNDER IS POSSIBLE FOR MKE TO ENW EARLY
THIS AFTERNOON THROUGH ABOUT 3 PM. PRECIP TYPE FOR UES IS A LITTLE
MORE UNCERTAIN AS THERE COULD BE A LONGER PERIOD OF SNOW/SLEET/RAIN
MIX.

LOOK FOR PRECIP TO DIMINISH FROM SOUTHWEST TO NORTHEAST LATE
AFTERNOON TO EARLY EVENING. LOW CEILINGS AND FOG...POSSIBLY
DENSE...ARE EXPECTED OVERNIGHT AS THE SURFACE LOW TRACKS OVERHEAD.

&&

.PREV DISCUSSION... /ISSUED 601 AM CST TUE FEB 2 2016/

SHORT TERM...TODAY AND TONIGHT...FORECAST CONFIDENCE IS MEDIUM.

INITIAL BAND OF RADAR RETURNS LIFTING NORTH THROUGH SRN WI IN LINE
WITH 700 MB WAA BUT LITTLE TO NO GROUND TRUTH AS ANY ELEVATED PCPN
EVAPORATES AS IT FALLS INTO DEEP DRY LAYER BELOW ON AREA FORECAST
SOUNDINGS. SATURATION WILL BE RELATIVELY FAST AFTER 12Z WITH STRONG
WARM ADVECTION AND STRONG LIFT. FORECAST SOUNDINGS SHOW COLUMN
SATURATES QUICKLY AND THERE IS A RAPID DROP IN CONDENSATION PRESSURE
DEFICITS NOTED ON ISENTROPIC FORECASTS.

BASED ON VERTICAL THERMAL PROFILES WILL SEE A BURST OF MAINLY SNOW
MOVE INTO SOUTHERN WISCONSIN MID-MORNING...CHANGING RAPIDLY TO RAIN
IN THE SOUTHEAST...AND A MIX IN CENTRAL SECTIONS THAT PUSHES UP TO
THE NORTHEAST WITH A MID LEVEL WARM LAYER. WITH REDUCED SNOW AMOUNTS
OVERALL AND ESPECIALLY IN THE SOUTHEAST CWA...HAVE TRIMMED
WASHINGTON AND JEFFERSON COUNTIES FROM THE ADVISORIES...AND
PULLED IOWA COUNTY OUT OF THE WARNING AND INTO AN ADVISORY.

NORTHWESTERN SECTIONS OF THE CWA REMAIN IN THE WARNING AND WILL SEE
STEADY MODERATE TO AT TIMES HEAVY SNOW THROUGH THE AFTERNOON AS THE
STRONGEST FORCING AND OMEGA LIFT UP OVER THE REGION. SNOW TOTALS
WILL BE IN THE 6 TO 8 INCH RANGE ALONG AND NORTHWEST OF A LONE
ROCK...PORTAGE TO BERLIN LINE...TAPERING TO 3 TO 5 INCHES IN THE
ADVISORY AREAS...WITH 1 TO 2 INCHES ELSEWHERE...EXCEPT FOR LESS
THAN 1 INCH AMOUNTS SOUTHEAST OF A MEQUON TO LAKE GENEVA LINE.

A COMPLICATING FACTOR FOR THE ENTIRE CWA WILL BE THE GUSTY EAST
WINDS IN THE TIGHTENING GRADIENT AHEAD OF THE LOW THIS AFTERNOON.
WINDS WITHIN 1500 FT OF THE SURFACE JUMP UP TO 35 TO 40 KNOTS...WITH
FORECAST SOUNDINGS SHOWING ENOUGH LOW-LEVEL MIXING TO TAP SOME OF
THESE WINDS. SATURATED ISOTHERMAL PROFILE WILL LIMIT MOMENTUM
TRANSFER BUT COULD STILL SEE WIDESPREAD GUSTS BETWEEN 25 AND 30
KNOTS. WINDS WILL EASE THIS EVENING AS GRADIENT SLACKENS WITH THE
LOW MOVING CLOSER TO SOUTHERN WISCONSIN.

ELEVATED CAPE AROUND 260 J/KG ORIGINATING AROUND 4-5K FT WITH
EQUILIBRIUM LEVELS  NEAR 27K FT BRINGS THE POTENTIAL OF THUNDER TO
THE SOUTHEAST THIS AFTERNOON.

STEADY MODERATE PCPN ENDS FROM SOUTH TO NORTH AS STRONGEST
FORCINGMOVES OFF TO THE NORTH AND MID-LEVEL DRY PUNCH OVERSPREADS
MOST OF SOUTH CENTRAL WI BY 00Z AND THE REST OF SRN WI BETWEEN 00Z
AND 06Z. THE LOSS OF CRYSTAL GROWTH AS THE DENDRITE GROWTH ZONE
DRIES OUT WILL CHANGE SNOW TO LIGHT RAIN OR DRIZZLE....WITH SOME ICE
PELLETS POSSIBLE. ONLY THE FAR NORTHWEST CORNER OF THE CWA LOOKS TO
STAY IN LIGHT SNOW AS THE COLUMN REMAINS COOL AND THE DGZ MOIST
ENOUGH FOR SNOW.

LIGHT PRECIPITATION WILL BEGIN TO CROSS THE CWA WITH A REGION OF LOW
TO MID LEVEL FRONTOGENESIS IN THE DEFORMATION ZONE ON THE NW FLANK
OF THE SURFACE LOW AS IT PASSES ACROSS SRN WI AND AHEAD OF A
VIGOROUS VORTICITY MAXIMA THAT ROUNDS THE BASE OF THE 500 MB TROUGH
AND LIFTS INTO THE REGION AROUIND 12Z WED.

WEDNESDAY THROUGH FRIDAY...FORECAST CONFIDENCE MEDIUM.

BY WED MORNING THE 500 MB UPPER TROUGH WILL BE NEAR THE MS RIVER
WHILE A 996 MB SFC LOW AND COLD FRONT WILL BE LOCATED OVER SE WI.
THE UPPER TROUGH PASSAGE AND SFC-850 MB FRONTOGENESIS WILL BRING
LGT SNOW TO MUCH OF SRN WI WITH 1-2 INCHES OF ACCUM OVER THE NRN
CWA AND MOST OF SOUTH CENTRAL WI...WITH LESSER AMOUNTS IN SE WI.
THE PCPN TYPE WILL STILL BE INITIALLY RAIN IN FAR ERN WI BUT CHANGE
TO ALL SNOW BY THE MIDDLE TO LATE MORNING HOURS AS THE COLD
ADVECTION INCREASES ON BRISK NWLY SFC WINDS. SFC TEMPS WILL VERY
GRADUALLY FALL THROUGHOUT THE DAY.

FOR WED NT SOME UNCERTAINTY ON WHETHER STRATOCUMULUS FIELD WILL
BECOME FEW-SCT OR REMAIN BROKEN. A WEAK SFC RIDGE WILL MOVE INTO
SOUTH CENTRAL WI BY THU MORNING. ACCOUNTED FOR SOME CLEARING
MAINLY IN THE FAR WRN CWA WITH UPPER SINGLE DIGIT LOWS WITH TEENS
ELSEWHERE. FOR THU-THU NT A COUPLE SHORTWAVE TROUGHS WILL PASS
WITH THE FIRST EXPECTED TO BE DRY WHILE THE 2ND ONE IS A DIGGING
VORT MAX FOR THU AFT AND EVE. THERE WILL BE A VERY WEAK SFC TROUGH
WITH THIS FEATURE ALTHOUGH OVERALL LIFT IS VERY WEAK. THUS WENT
WITH SLIGHT CHANCE POPS FOR THU NT AS OF NOW. ANOTHER WEAK SFC
RIDGE WILL SLOWLY MOVE EWD ACROSS SRN WI ON FRI. AFTER MILD TEMPS
INTO WED MORNING...SFC TEMPS WILL RETURN TO MORE NORMAL CONDITIONS
THROUGH FRI.

LONG TERM...SATURDAY THROUGH MONDAY...FORECAST CONFIDENCE MEDIUM.

A WEAK SFC TROUGH WILL PASS FRI NT FROM LOW PRESSURE PASSING
ACROSS THE NRN GREAT LAKES. THIS WILL BE FOLLOWED BY A WEAK RIDGE
OF HIGH PRESSURE FOR SAT. SLIGHT CHANCES OF SNOW IS FORECAST FRI
NT INTO SAT MORNING FOR THE FAR NRN CWA. A LARGE AND FAIRLY STRONG
SFC LOW WILL THEN TRACK ALONG THE US AND CANADIAN BORDER FOR EARLY
NEXT WEEK. SWLY WINDS AND WARM ADVECTION WILL BOOST HIGH TEMPS
INTO THE 30S WITH COOLING AFTERWARD. ONLY SMALL POPS FOR LGT SNOW
ARE FORECAST DURING THIS TIME.

AVIATION/12Z TAFS/...

INCREASING EAST WINDS ARE LIFTING THE FOG INTO MORE OF AN IFR STRATUS
DECK. SOME VFR CIGS MOVING IN FROM THE SOUTH...BUT EXPECT MAINLY
MVFR CIGS. INITIAL ELEVATED BAND OF PRECIPITATION ON AREA RADARS
NOT PRODUCING MUCH IN THE WAY OF GROUND TRUTH AS IT FALLS INTO
DRIER AIR BELOW. RAPID UPDATE MODELS IN LINE WITH OTHER GUIDANCE
IN BRINGING STEADY MODERATE TO AT TIMES HEAVY PRECIPITATION INTO
THE FORECAST AREA AROUND/AFTER 15Z....MOVING FROM SOUTH TO NORTH
AND COVERING ALL OF SOUTHERN WISCONSIN BY 18Z.

WILL SEE SNOW INITIALLY...TURNING TO A MIX ALONG AND SOUTH OF THE
I-94 CORRIDOR FROM MADISON TO MILWAUKEE AND SOUTH WITH MAINLY RAIN
IN THE SOUTHEAST. MVFR CONDITIONS WITH PERIODS OF IFR ARE
EXPECTED FROM LATE MORNING THROUGH THE AFTERNOON. EAST WINDS WILL
INCREASE WITH GUSTS OF 25 TO 30 KNOTS FROM LATE MORNING THROUGH
THE AFTERNOON. PRECIPITATION WILL TAPER OFF THIS EVENING TO
SCATTERED LIGHT RAIN OR SNOW AS BEST FORCING MOVES NORTH.

MARINE...

KEPT THE GALE WARNING IN EFFECT FROM 15Z TODAY TO 00Z
WEDNESDAY ACROSS THE NEARSHORE WATERS OF LAKE MICHIGAN....THOUGH
THE STRONGER EAST GALE GUSTS MAY BE SOMEWHAT DELAYED...ESPECIALLY
NORTH OF MILWAUKEE... WITH THE LATER ARRIVAL OF THE STRONG LOW
PRESSURE SYSTEM. WINDS WILL EASE THIS EVENING TO SMALL CRAFT
LEVELS WITH THE BAGGIER GRADIENT AROUND THE ELONGATING LOW AS IT
MOVES OVER SOUTHERN LAKE MICHIGAN OVERNIGHT INTO WEDNESDAY.

THE GUSTY ONSHORE WINDS WILL BUILD HIGH WAVES.

THE GUSTY WINDS WILL LOWER AND SHIFT NORTH LATER TONIGHT INTO
WEDNESDAY MORNING AS THE LOW PASSES OVER SOUTHERN LAKE
MICHIGAN...THEN NORTHWEST AS THE LOW MOVES NORTHEAST AND AWAY FROM
THE AREA. GUSTS OF 25 KNOTS ARE EXPECTED FROM LATE WEDNESDAY MORNING
INTO THE EVENING...WITH HIGH WAVES SHIFTING TOWARD AND OVER THE OPEN
WATERS. A SMALL CRAFT ADVISORY WILL BE NEEDED FOR MOST OF THIS
PERIOD...AFTER THE GALE WARNING EXPIRES.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR WIZ067-
     068.

     WINTER STORM WARNING UNTIL 6 AM CST WEDNESDAY FOR WIZ046-047-056-
     057.

     WINTER WEATHER ADVISORY UNTIL 6 AM CST WEDNESDAY FOR WIZ051-052-
     058-062-063.

LM...GALE WARNING UNTIL 6 PM CST THIS EVENING FOR LMZ643>646.

&&

$$

UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...REM
WEDNESDAY THROUGH MONDAY...GEHRING



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