Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 311718 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1118 AM CST SAT JAN 31 2015

.UPDATE...

12Z MODELS IN GENERAL ARE SIMILAR TO PREVIOUS COUPLE OF RUNS WITH
REGARDS TO SYNOPTIC FEATURES ACROSS THE AREA FOR TONIGHT INTO
SUNDAY/SUNDAY NIGHT. BEST UPWARD VERTICAL MOTION IS EXPECTED
LATER TONIGHT INTO EARLY SUNDAY...WITH FOCUSED 600 MB WARM AIR
ADVECTION AND FRONTOGENESIS RESPONSE SHIFTING EAST ACROSS THE FAR
SOUTHERN COUNTIES. MOST OF THIS DOES REMAIN IN NORTHERN ILLINOIS.
BEST UPWARD VERTICAL MOTION IN THE DENDRITE GROWTH ZONE ALSO
REMAINS IN NORTHERN ILLINOIS...THOUGH STILL HAVE UP TO 5
MICROBARS/SECOND IN OUR AREA.

THIS MAY BE WHY MESOSCALE MODELS...ESPECIALLY THE LATEST FEW HRRR
RUNS...ARE SHOWING THE BEST SIMULATED REFLECTIVITY VALUES
REMAINING JUST TO THE SOUTH OF THE AREA LATER TONIGHT INTO SUNDAY
MORNING.

THE 12Z NAM/GFS ARE SHOWING TOTAL QPF FOR THE EVENT OF 0.75
INCHES IN THE FAR SOUTH...TO 0.25 INCHES IN THE FAR NORTHERN
COUNTIES. GIVEN THE BEST UPWARD VERTICAL MOTION FIELDS BEING JUST
TO OUR SOUTH...THESE QPF AMOUNTS MAY BE A BIT TOO HIGH. MAY
CONSIDER LOWERING QPF AND AMOUNTS A BIT...THOUGH SOME UNCERTAINTY
EXISTS.

OVERALL...STILL EXPECTING A GOOD LONG DURATION SNOW EVENT FOR THE
AREA TONIGHT INTO SUNDAY/SUNDAY NIGHT. AT THIS TIME...THINK MOST
HEADLINES SHOULD REMAIN INTACT ACROSS THE AREA.

THE ONE AREA THAT MAY NEED A HEADLINE CHANGE IS THE FAR SOUTHERN
COUNTIES WEST OF RACINE/KENOSHA. CURRENTLY...THE FORECAST HAS
AROUND 8 INCHES OF ACCUMULATION IN 24 HOURS. THE EXPECTED GUSTY
WINDS WITH THE SNOW MAY REQUIRE AN UPGRADE TO A WINTER STORM
WARNING FOR THE REST OF THE BORDER COUNTIES. STILL ASSESSING THE
12Z MODELS...AND WILL MAKE A DECISION THIS AFTERNOON.

&&

.AVIATION/18Z TAFS/...

VFR CONDITIONS ARE EXPECTED THIS AFTERNOON INTO EARLY THIS
EVENING. COLD FRONT SLIDING SOUTH ACROSS THE AREA LATER THIS
AFTERNOON WILL ALLOW LIGHT WEST TO NORTHWEST WINDS TO SHIFT
NORTHEAST BY MIDDLE EVENING. THESE WINDS WILL BECOME GUSTY DURING
THE NIGHT AND REMAIN SO ON SUNDAY...BECOMING NORTH SUNDAY NIGHT.
GUSTS OF 25 TO 28 KNOTS ARE EXPECTED AT TIMES SUNDAY INTO SUNDAY
NIGHT.

SNOW WILL SPREAD NORTHEAST INTO TAF SITES BETWEEN 03Z AND 05Z
SUNDAY...AND REMAIN LIGHT TO MODERATE LATER TONIGHT AND SUNDAY.
THE SNOW SHOULD END AT MADISON BETWEEN 00Z AND 03Z
MONDAY...LINGERING AT THE EASTERN SITES UNTIL BETWEEN 09Z AND 12Z
MONDAY DUE TO LAKE EFFECT SNOW BAND MOVING THROUGH THAT AREA.

EXPECT HOURLY SNOW RATES OF 1/4 TO 1/2 INCH PER HOUR LATER TONIGHT
INTO SUNDAY...WITH RATES UP TO 1 INCH PER HOUR POSSIBLE IN ANY
MODERATE SNOW BANDS. TOTAL AMOUNTS OF 5 TO 6 INCHES AT
MADISON...WITH 6 TO 8 INCHES AT WAUKESHA AND MILWAUKEE...AND 7 TO
9 INCHES AT KENOSHA.

EXPECT CEILINGS AND VISIBILITIES AROUND OR BELOW ALTERNATE
MINIMUMS DURING THE PERIOD OF SNOW...APPROACHING AIRPORT MINIMUMS
AT TIMES LATER TONIGHT INTO SUNDAY. BLOWING SNOW IS ALSO
ANTICIPATED SUNDAY INTO SUNDAY NIGHT WITH THE GUSTY WINDS. THIS
MAY REDUCE VISIBILITIES TO MVFR CATEGORY FOR A FEW HOURS AFTER THE
SNOW ENDS.

&&

.MARINE...

SMALL CRAFT ADVISORY REMAINS IN EFFECT FROM LATER THIS EVENING
INTO MONDAY MORNING ACROSS THE NEARSHORE WATERS OF LAKE MICHIGAN.
TIGHT PRESSURE GRADIENT WITH THE PASSING LOW PRESSURE SYSTEM TO
THE SOUTH WILL RESULT IN GUSTY ONSHORE WINDS TONIGHT INTO
SUNDAY...BECOMING MORE OFFSHORE SUNDAY NIGHT. GUSTS TO 30 KNOTS
ARE EXPECTED AT TIMES.

THIS WILL GENERATE HIGH WAVES UP TO 6 TO 10 FEET SUNDAY INTO
SUNDAY NIGHT...SLOWLY SUBSIDING MONDAY MORNING. FREEZING SPRAY IS
ALSO EXPECTED...WITH HEAVY FREEZING SPRAY POSSIBLE SUNDAY NIGHT. A
HEAVY FREEZING SPRAY WATCH MAY BE NEEDED FOR SUNDAY NIGHT IF
CONDITIONS CONTINUE TO BE FAVORABLE.

&&

.PREV DISCUSSION... /ISSUED 602 AM CST SAT JAN 31 2015/

SHORT TERM...

TODAY...FORECAST CONFIDENCE IS HIGH.

WILL SEE A FEW PEEKS OF SUN THIS MORNING THEN MID-HIGH CLOUD SHIELD
WITH APPROACHING STORM MOVE IN.  HIGHS REACHED AROUND MIDDAY AS A
WEAK 850 MB THERMAL RIDGE MOVES ACROSS THE REGION...THEN TEMPS
STEADY WITH A GRADUAL COOLING FROM NORTH TO SOUTH DURING THE MID TO
LATE AFTERNOON AS WEAK SURFACE TROUGH/COLD FRONT SAGS INTO SRN WI.

TONIGHT...FORECAST CONFIDENCE IS HIGH.

WILL TIME BEGINNING OF SNOW INTO THE FORECAST AREA WITH FORCING AND
INCREASING DEEP LAYER MOISTURE...WHICH BRINGS THE LEADING EDGE OF
THE SNOW SHIELD INTO THE SW BETWEEN 22Z AND 00Z. SOME HINTS ON
FORECAST SOUNDINGS THAT THERE COULD INITIALLY BE A MIX OF RAIN AND
SNOW...OR EVEN RAIN...IN THE FAR SOUTHWEST GOING QUICKLY OVER TO ALL
SNOW WITH SATURATION IN THE DENDRITE GROWTH ZONE. LOW CONFIDENCE IN
THIS SCENARIO SO WILL LEAVE ALL SNOW.

STEADY LIGHT TO MODERATE SNOW MOVES IN ACROSS THE CWA AS THE
STRONGEST LAYER FRONTOGENESIS SPREADS ACROSS THE SRN HALF OF CWA AND
NRN IL BETWEEN 06Z AND 12Z SUNDAY. BLENDED QPF AMOUNTS AND CONSENSUS
SNOW RATIOS INDICATE 3 TO 4 INCHES ON THE GROUND ALONG AND SOUTHWEST
OF A LINE FROM THE DELLS THROUGH SRN DANE COUNTY TO PLEASANT PRAIRIE
BY 12Z SUNDAY.

INCREASING NORTHEAST WINDS GUSTING UP TO 25-30 MPH AS APPROACHING
LOW DEEPENS BRINGS BLOWING SNOW INTO THE PICTURE AFTER
06Z...CREATING DIFFICULT DRIVING CONDITIONS WITH REDUCED
VISIBILITIES AND DRIFTING SNOW.

SUNDAY AND SUNDAY NIGHT... FORECAST CONFIDENCE HIGH.

THE SNOW WILL REMAIN STEADY OVER ALL OF SOUTHERN WI ON SUNDAY AS A
500MB SHORTWAVE TROUGH SWINGS THROUGH THE REGION. 850-600MB
FRONTOGENESIS WILL LINGER OVER SOUTHERN WI ON SUNDAY AS WELL. WE
WILL LOSE THE FORCING FROM THE UPPER JET AS THE SHORTWAVE MOVES IN
THUS NO ENHANCEMENT OF UPWARD MOTION... JUST A STEADY 2 TO 4
MICROBARS PER SECOND. THE BEST CHANCE FOR MODERATE SNOW WILL BE FROM
MIDNIGHT SATURDAY NIGHT THROUGH NOON SUNDAY. SNOW WILL BEGIN TO
TAPER OFF SUNDAY AFTERNOON INLAND FROM THE LAKE.

THE SURFACE LOW WILL BE CROSSING SOUTHERN IL DURING THE DAY
SUNDAY... CAUSING A TIGHT PRESSURE GRADIENT OVER SOUTHERN WI AND
RESULTING IN BLUSTERY NORTHEAST WINDS AND BLOWING SNOW. WINDS WILL
REMAIN ELEVATED THROUGH THE DAY AND GRADUALLY DIMINISH SUNDAY NIGHT.

TOTAL SNOWFALL AMOUNTS FOR THE ENTIRE STORM ARE EXPECTED TO RANGE
FROM 2 TO 4 INCHES NORTH OF A LINE FROM SHEBOYGAN TO THE DELLS...
AND 6 TO 8 INCHES SOUTH OF A LINE FROM WEST BEND TO MADISON TO LONE
ROCK. THIS IS NOT MUCH OF A SHIFT FROM THE PREVIOUS FORECAST. THESE
TOTALS ARE OVER A LONG DURATION OF TIME... FROM THIS EVENING THROUGH
SUNDAY NIGHT. IF IT WAS NOT FOR THE BLOWING SNOW FACTOR... MANY
AREAS WITH AN ADVISORY WOULD NOT EVEN NEED A HEADLINE BECAUSE WE ARE
TALKING ABOUT SNOWFALL AMOUNTS OF 1 TO 3 INCHES OVER A COUPLE OF 6-
HOUR PERIODS. BUT... IT WILL BE VERY WINDY ON SUNDAY WITH RECENT
SNOWFALL WHICH WILL HAVE A GOOD CHANCE OF CAUSING REDUCED
VISIBILITIES WITH BLOWING AND DRIFTING SNOW... THUS SUPPORTING AN
ADVISORY.

NOW FOR THE LAKE EFFECT PORTION OF THE EVENT. WE WENT WITH A WINTER
STORM WARNING FOR MILWAUKEE-RACINE-KENOSHA COUNTIES DUE TO SLIGHTLY
HIGHER EXPECTED SNOWFALL AMOUNTS DUE TO LAKE ENHANCEMENT AND
EVENTUALLY A POSSIBLE LAKE EFFECT SNOW BAND. 1000-850MB FLOW WILL
CHANGE FROM ENE TO NNE SUNDAY AFTERNOON AND NIGHT... JUST AS THE
SYSTEM SNOW IS PULLING AWAY FROM THE REGION. THE WIND SHIFT WILL
ALLOW FOR SOME MORE ENHANCED CONVERGENCE OVER THE LAKE WHICH COULD
FORM A HEAVY LAKE EFFECT SNOW BAND THAT SLIDES FROM NORTH TO SOUTH
DOWN THE LAKESHORE SUNDAY NIGHT. THIS WOULD BE ACCOMPANIED BY GUSTY
NNE WINDS... A DEEP DENDRITIC GROWTH ZONE LAYER AND STRONG UPWARD
MOTION IN THE LOW LEVELS. WHILE THIS COULD BE AN INTENSE BAND OF
SNOW WITH HIGH SNOWFALL RATES... IT SHOULD BE TRANSIENT AND NOT SIT
OVER ONE AREA FOR A LONG PERIOD OF TIME.

LONG TERM...

MONDAY THROUGH TUESDAY... FORECAST CONFIDENCE MEDIUM.

NORTHWEST FLOW ALOFT WILL RESUME OVER THE UPPER MIDWEST. CLIPPERS
COULD BRING LIGHT SNOW TO SOUTHERN WI MONDAY NIGHT AND TUE NIGHT.
THE TUE NIGHT SYSTEM HAS THE POTENTIAL TO DROP A COUPLE OF INCHES.
TEMPS WILL BE BELOW NORMAL DURING THIS PERIOD.

WEDNESDAY THROUGH FRIDAY... FORECAST CONFIDENCE MEDIUM.

A BLAST OF ARCTIC AIR IS EXPECTED TO SETTLE OVER THE UPPER GREAT
LAKES THROUGH THIS PERIOD ON DRY HIGH PRESSURE. WIND CHILL TEMPS
WILL APPROACH -20F THU NIGHT.

AVIATION/12Z TAFS/...

VFR STRATO CU DECK SHOULD EXIT EASTERN TAF SITES BY MID-MORNING
WITH VFR CONDITIONS EXPECTED THROUGH MOST OF THE DAY. MVFR CIGS
ACROSS THE NORTHERN HALF OF THE STATE ARE BEHIND A WEAK SURFACE
TROUGH/COLD FRONT THAT IS EXPECTED TO DROP THROUGH SRN WI THIS
AFTERNOON...BRINGING THE LOWER CIGS INTO THE TAF SITES LATE THIS
AFTERNOON AND EVENING.

APPROACHING LOW PRESSURE WILL SPREAD STEADY SNOW INTO SOUTHERN
WISCONSIN EARLY THIS EVENING. CURRENT TIMING BRINGS THE SNOW TO
THE TAF SITES BY 02Z. THIS WILL BE A LONG DURATION EVENT...WITH
MAINLY STEADY LIGHT SNOW WITH A FEW BRIEF PERIODS OF MODERATE
SNOW...ESPECIALLY AT KMKE AND KENW WHERE LAKE-ENHANCEMENT/LAKE
EFFECT WILL RAISE SNOW TOTALS. THIS WILL KEEP PREVAILING IFR
CONDITIONS THROUGH THE REMAINDER OF THE FORECAST...WITH LIFR
VISIBILITIES AT TIMES DUE TO BLOWING AND DRIFTING SNOW AS
NORTHEAST WINDS GUST UP TO 25 KNOTS.

THE SNOW WILL SLOWLY TAPER OFF FROM WEST TO EAST LATE SUNDAY
AFTERNOON AND EVENING...WITH BLOWING SNOW CONTINUING INTO SUNDAY
NIGHT.

MARINE...

WILL BE ISSUING A SMALL CRAFT ADVISORY BEGINNING AT 03Z SUNDAY FOR
THE NORTHERN ZONES AND 05Z IN THE SOUTH AS NORTH TO NORTHEAST WINDS
INCREASE WITH APPROACHING DEEPENING LOW PRESSURE. WINDS WILL LOWER
BELOW CRITERIA BY 12Z MONDAY...BUT WAVES WILL BE SLOWER TO
SUBSIDE...SO WILL END ADVISORY IN THE NORTHERN ZONES AT 15Z MONDAY
AND IN THE SOUTH AT 18Z. THE COMBINATION OF WINDS...WAVES AND
TEMPERATURES WILL CREATE FREEZING SPRAY...BUT NOT CONFIDENT IT WILL
BE HEAVY ENOUGH FOR A HEAVY FREEZING SPRAY WATCH/WARNING. LATER
SHIFTS WILL HAVE TO MONITOR THIS POTENTIAL.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 3 AM CST
     MONDAY FOR WIZ066-071-072.

     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 9 PM CST
     SUNDAY FOR WIZ056-057-062-063-067>069.

     WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 3 AM CST MONDAY
     FOR WIZ052-058>060-064-065-070.

LM...SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO NOON CST MONDAY
     FOR LMZ645-646.

     SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 9 AM CST MONDAY
     FOR LMZ643-644.

&&

$$

UPDATE...WOOD
TODAY/TONIGHT AND AVIATION/MARINE...REM
SUNDAY THROUGH FRIDAY...MRC


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