Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 290246
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
946 PM CDT SAT MAR 28 2015

.UPDATE...INCREASING HIGH CLOUDS AND BOUNDARY LAYER WINDS WILL
SLOW DOWN EARLY EVENING TEMPERATURE FALL. AS IS...STILL NEEDED TO
LOWER THE OVERNIGHT MINIMUM TEMPS IN A FEW SPOTS DUE TO EARLY
EVENING FALL. AIR MASS REMAINS VERY DRY...BUT RAPIDLY INCREASING
LOW LEVEL JET LATE TONIGHT INTO SUNDAY MRNG WILL PULL SURGE OF
DEEPER MOISTURE QUICKLY INTO THE AREA. PWAT VALUES INCREASE TO
AROUND 0.75 INCH SUN MRNG. STRONG FORCING FROM VIGOROUS SHORT
WAVE AND STRONG WARM AIR ADVECTION WILL RESULT IN A 2 TO 4 HOUR
PERIOD OF MIXED PRECIPITATION ACROSS SRN WI...SPREADING INTO THE
WEST 12-13Z...REACHING THE EAST 15-16Z.

EXPECT WRN CWA TO BE CLOSER TO SURGE OF WARMER LOW LEVEL AIR.
HENCE LIKELY SLEET AND RAIN CHANGING TO MOSTLY RAIN. HOWEVER
TIMING CRITICAL AND MAY BE A 1 TO 2 HOUR PERIOD WHEN SFC TEMPS
AROUND FREEZING. THEREFORE STILL A POTENTIAL FOR LIGHT FREEZING
RAIN. FARTHER EAST...SFC TEMPS WL HAVE TIME TO WARM...HOWEVER MORE
DRY AIR IN PLACE AND EVAPORATIVE COOLING MAY RESULT IN MORE OF A
RAIN...SLEET MIXTURE. FORECAST SOUNDINGS FOR THE LATE MORNING SHOW
THE COLUMN COOLING AROUND 17-18Z POSSIBLY RESULTING IN SOME SNOW
MIXED IN...HOWEVER BEGIN TO LOSE ICE CRYSTALS FALLING INTO CLOUD
LAYER AT THIS TIME. EARLIER THIS EVENING ISSUED SPS AND TOP NEWS
STORY TO WEBSITE TO HIGHLIGHT MIX THREAT.

LOW LEVEL INVERSION WILL PREVENT STRONGEST WINDS FROM REACHING SFC
ON SUNDAY. HOWEVER STILL EXPECT WIND GUSTS TO 40 MPH WITH
SUSTAINED WINDS OF 20 TO 25 MPH...WITH A FEW SPOTS REACHING
30 MPH.

&&

.AVIATION/06Z TAFS/...EXPECT A PERIOD OF MIXED SLEET AND RAIN TO
SWEEP ACROSS TAF SITES SUN MRNG. MAY BE A PERIOD OF LIGHT FREEZING
RAIN AT KMSN 14-15Z. RAIN AND SLEET MAY BE MIXED WITH SNOW IN ERN
TAF SITES. MIXED PRECIP WL END IN THE LATE MRNG AND EARLY AFTN
WITH LINGERING SCT -SHRA IN THE AFTN. EXPC VFR CONDITIONS TO
RETURN IN THE AFTN OR EVE. GUSTY SOUTHWEST WINDS MAY REACH 35KTS
ON SUN. LOW LEVEL WIND SHEAR WILL DEVELOP TONIGHT INTO SUN MRNG.

&&

.MARINE...RAPIDLY TIGHTENING PRESSURE GRADIENT OVERNIGHT AHEAD OF
APPROACHING LOW PRESSURE AND COLD FRONT WILL CAUSE SOUTH WINDS TO
BEGIN GUSTING IN EXCESS OF 22KTS LATER TONIGHT. THE STRONGEST
WINDS ARE EXPECTED FROM MID-MORNING SUNDAY INTO THE AFTERNOON WHEN
GALE FORCE GUSTS OF 35 TO 40KTS ARE EXPECTED DUE TO VIGOROUS
WEATHER SYSTEM MOVING THRU WESTERN GTLAKES. HENCE STATUS QUO ON
SMALL CRAFT ADVISORY STARTING UP LATER TONIGHT AND GALE WARNING ON
SUNDAY.

&&

.PREV DISCUSSION... /ISSUED 311 PM CDT SAT MAR 28 2015/

SHORT TERM...

TONIGHT...FORECAST CONFIDENCE IS HIGH.

SHORT TERM MODELS IN GOOD AGREEMENT WITH HIGH PRESSURE MOVING
FURTHER EAST SOUTHEAST OF THE REGION. PRESSURE GRADIENT GRADUALLY
TIGHTENS LATER TONIGHT...AHEAD OF APPROACHING COLD FRONT/500 MB
SHORTWAVE TROUGH. SOUTH WINDS INCREASE LATER TONIGHT AS A
RESULT...WITH SOME GUSTINESS TOWARD DAYBREAK SUNDAY MORNING.

MIDDLE TO HIGH CLOUDS SHOULD GRADUALLY MOVE EASTWARD INTO THE AREA
LATER TONIGHT AS WELL. LOWS TONIGHT SHOULD OCCUR LATER THIS
EVENING...THEN HOLD STEADY OR RISE SLIGHTLY WITH STRONG WARM AIR
ADVECTION PUSHING INTO THE AREA.

SUNDAY...FORECAST CONFIDENCE IS MEDIUM.

SYNOPTIC AND MESOSCALE MODELS ARE IN DECENT AGREEMENT WITH THE
TIMING OF PRECIPITATION WITH THE STRONG WARM AIR ADVECTION...AS WELL
AS THE PASSING 500 MB SHORTWAVE TROUGH AND SURFACE COLD FRONT. FIRST
BATCH OF MIXED PRECIPITATION SHOULD MOVE EAST THROUGH THE AREA
DURING THE MORNING...FOLLOWED BY A SECOND ROUND OF RAIN DURING THE
AFTERNOON WITH A SECONDARY 500 MB SHORTWAVE TROUGH.

THE PRECIPITATION TYPES WITH THE FIRST BATCH OF PRECIPITATION WILL
BE TRICKY...CONFIDENCE HERE IS MEDIUM. AREA FORECAST SOUNDINGS FROM
NAM/GFS SHOWING POTENTIAL FOR LIGHT FREEZING RAIN AND LIGHT
SLEET...DEPENDING ON IF ICE CRYSTALS ARE INTRODUCED INTO THE AIR
COLUMN AND THE MAGNITUDE OF THE WARM LAYER IN THE LOW LEVELS. CANNOT
RULE OUT SOME LIGHT SNOW AT THE ONSET AS WELL. IF TEMPERATURES WARM
UP QUICKER THAN EXPECTED...LIGHT RAIN MAY OCCUR WITHOUT THE MIXED
PRECIPITATION.

FOR NOW...WILL CONTINUE WITH THE MIXED PRECIPITATION TYPES WORDING
FOR SUNDAY MORNING. TEMPERATURES SHOULD WARM ENOUGH FOR MOSTLY LIGHT
RAIN BY 15Z TO 16Z SUNDAY...THOUGH LIGHT SLEET REMAINS POSSIBLE
UNTIL MIDDAY. TEMPERATURES SHOULD WARM INTO THE MID 40S DURING THE
AFTERNOON. SOUTHWEST GUSTS OF 30 TO 35 KNOTS ARE EXPECTED WITH THE
TIGHT PRESSURE GRADIENT.

SUNDAY NIGHT AND MONDAY... FORECAST CONFIDENCE HIGH.

THE 250 MB UPPER TROUGH EXITS SOUTHERN WISCONSIN SUNDAY NIGHT WITH
A NORTHWEST UPPER FLOW MONDAY. FAIRLY NEUTRAL UPPER DIVERGENCE.
850/700 MB WARM AIR ADVECTION OCCURS SUNDAY NIGHT AS A TROUGH
MOVES ACROSS THE UPPER GREAT LAKES MONDAY. DOWNWARD 700 MB MOTION
SUNDAY NIGHT AND MONDAY MORNING WITH WEAK UPWARD MOTION MONDAY
AFTERNOON. 850/700 MB RH IS DRY UNTIL MONDAY AFTERNOON AS THE 700
MB LAYER SATURATES.

MONDAY NIGHT AND TUESDAY...FORECAST CONFIDENCE HIGH.

A JET MAX SWINGS THROUGH THE NORTHWEST FLOW TUESDAY AS A 250 MB
UPPER RIDGE MOVES INTO THE DAKOTAS. THE UPPER LEVEL DIVERGENCE
INCREASES MONDAY NIGHT AND CONTINUES UNTIL THE EARLY AFTERNOON
OVER THE SOUTHEAST ON TUESDAY. 850/700 MB WARM AIR ADVECTION
IS QUITE STRONG MONDAY NIGHT BEFORE COOLING TUESDAY. WEAK 700 MB
UPWARD MOTION OCCURS EARLY MONDAY EVENING BEFORE INCREASING TO
FAIRLY STRONG VALUES MAINLY FROM NORTH OF MILWAUKEE AND ACROSS
EAST CENTRAL WISCONSIN. 700 MB RH IS NEARLY SATURATED MONDAY
EVENING BEFORE DRYING FROM THE WEST. MONDAY EVENING THE 700 MB
LAYER SATURATES. 850 MB LAYERS DO NOT SATURATE BUT DO INCREASE
FROM THE NORTH TUESDAY BRINGING A POTENTIAL BAND OF SHALLOW
STRATOCUMULUS. HOWEVER WITH MIXING THIS MAY STAY SCATTERED.

THE GFS IS DRY MONDAY NIGHT BUT THE ECMWF BRINGS PRECIPITATION TO
ALL BUT THE FAR SOUTHWEST AREAS...WITH THE NAM KEEPING IT OVER
NORTHEAST AREAS OF THE FORECAST AREA...ESPECIALLY TOWARD
SHEBOYGAN. GIVEN THE SURFACE AND 850 MB TEMPERATURES...IT WOULD
BE RAIN IF IT HAPPENS. HIGH PRESSURE WILL DRIFT THEN THROUGH THE
REGION TUESDAY.

LONG TERM...

TUESDAY NIGHT AND WEDNESDAY... FORECAST CONFIDENCE HIGH.

THE UPPER RIDGE WILL WEAKEN AS IT MOVES ACROSS WISCONSIN MONDAY
MORNING WITH THE UPPER FLOW BECOMING WEST/SOUTHWEST WEDNESDAY
AFTERNOON. AS THE HIGH RECEDES EAST TUESDAY EVENING...WARM AIR
ADVECTION OCCURS WEDNESDAY WITH SOUTH WINDS. THE MODELS KEEP THE
PRECIPITATION OFF TO THE WEST THROUGH WEDNESDAY AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY... FORECAST CONFIDENCE MEDIUM.

A SHORTWAVE EXITS THE NORTHERN PLAINS WEDNESDAY EVENING...AND
MOVES ACROSS THE LAKE SUPERIOR AREA THURSDAY MORNING ON THE GFS.
THE ECMWF IS A LITTLE WEAKER AND SLOWER. AS A RESULT THE ECMWF IS
SLOWER WITH THE COLD FRONT AND PRECIPITATION AS A STRONG LOW MOVES
ACROSS SOUTHERN CANADA. THE GFS HAS ALL THE PRECIPITATION
WEDNESDAY NIGHT...WITH THE ECMWF LINGERING IT INTO WEDNESDAY.

FRIDAY AND SATURDAY... FORECAST CONFIDENCE LOW.

THE MODELS DIVERGE AS WE GET TO FRIDAY. WHILE THE ECMWF WAS WEAKER
WITH THE NORTHERN STREAM SHORTWAVE THURSDAY...IT IS STRONGER WITH
A SHORTWAVE MOVING ACROSS WISCONSIN AND THE MID MISSISSIPPI
VALLEY FRIDAY. AS A RESULT THE ECMWF BRINGS A STRONG DEEPENING LOW
ACROSS CENTRAL ILLINOIS TOWARDS LOWER MICHIGAN...WHILE THE GFS
TRACKS A SOMEWHAT WEAKER LOW ACROSS THE OHIO RIVER AREA. THE GFS
ONLY BRINGS SOME PRECIPITATION...LIKELY SNOW TO THE ILLINOIS
BORDER AREA. MEANWHILE THE ECMWF BRINGS A MIX OF RAIN AND SNOW
CHANGING TO SNOW FRIDAY INTO FRIDAY EVENING...WITH HEAVY
PRECIPITATION JUST TO OUR SOUTH AND EAST.

AVIATION/00Z TAFS/...

HIGH PRESSURE WILL SLIDE EAST SOUTHEAST OF THE REGION TONIGHT. VFR
CONDITIONS ARE EXPECTED AT TAF SITES TONIGHT. SOUTHEAST WINDS WILL
LINGER AT THE EASTERN SITES INTO EARLY EVENING...BEFORE BECOMING
SOUTH. SOUTH WINDS WILL REMAIN AT MADISON. MIDDLE TO HIGH CLOUDS
WILL GRADUALLY SPREAD INTO THE AREA LATER TONIGHT.

SOUTH WINDS WILL GRADUALLY INCREASE IN MAGNITUDE LATER
TONIGHT...WITH GUSTY SOUTHWEST WINDS SUNDAY MORNING...BECOMING
WESTERLY LATER SUNDAY AFTERNOON. SOUTHWEST WINDS OF 45 TO 50 KNOTS
AT 2000 FEET ABOVE GROUND LEVEL BETWEEN 09Z AND 14Z SUNDAY WILL
BRING LOW LEVEL WIND SHEAR CONDITIONS.

COLD FRONT AND TROUGH OF LOW PRESSURE MOVING EAST THROUGH THE REGION
SUNDAY WILL BRING A ROUND OF MIXED PRECIPITATION TO TAF SITES IN THE
MORNING. A MIX OF LIGHT RAIN AND LIGHT SLEET SHOULD MOVE EAST INTO
MADISON BY 14Z SUNDAY...AND THE EASTERN SITES BY 15Z SUNDAY.

LIGHT FREEZING RAIN IS POSSIBLE AT TIMES...ALONG WITH LIGHT SNOW AT
THE ONSET. CONFIDENCE HERE IS MEDIUM AND THINGS COULD CHANGE IN
LATER FORECASTS. ANY ACCUMULATIONS OF LIGHT SNOW/SLEET WILL BE JUST
A FEW TENTHS OF AN INCH AT BEST...WITH A LIGHT GLAZING POSSIBLE AS
WELL. KEEP UP WITH LATER FORECASTS.

TEMPERATURES SHOULD WARM ENOUGH FOR A CHANGEOVER TO ALL LIGHT RAIN
BETWEEN 15Z AND 18Z SUNDAY...LINGERING INTO THE AFTERNOON. CEILINGS
AND VISIBILITIES SHOULD BE IN THE LOWER MVFR TO IFR CATEGORIES
SUNDAY...BUT ABOVE ALTERNATE MINIMUMS.

MARINE...

A TIGHT PRESSURE GRADIENT WILL DEVELOP LATER TONIGHT AND LINGER INTO
SUNDAY NIGHT...AS A COLD FRONT MOVES EAST TOWARD AND THROUGH THE
REGION. INCREASING SOUTH WINDS WILL DEVELOP BY LATER TONIGHT...THEN
VEER SOUTHWEST ON SUNDAY...THEN WEST LATE SUNDAY INTO SUNDAY NIGHT.

FREQUENT GUSTS OF 25 TO 30 KNOTS ARE EXPECTED LATER TONIGHT INTO
EARLY SUNDAY MORNING FROM NORTH TO SOUTH ACROSS THE NEARSHORE
WATERS. WAVES SHOULD BUILD TO 3 TO 6 FEET. A SMALL CRAFT ADVISORY IS
IN EFFECT FOR THIS PERIOD.

FREQUENT GUSTS TO 35 KNOT GALES ARE THEN ANTICIPATED FOR MOST OF
SUNDAY...WHERE A GALE WARNING REMAINS IN EFFECT. WAVES SHOULD BUILD
TO 5 TO 10 FEET. A SMALL CRAFT ADVISORY WILL BE NEEDED LATER SUNDAY
INTO SUNDAY NIGHT...AS WINDS AND WAVES SLOWLY SUBSIDE.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY FROM 4 AM TO 10 AM CDT SUNDAY FOR LMZ645-
     646.

     GALE WARNING FROM 10 AM TO 4 PM CDT SUNDAY FOR LMZ643>646.

     SMALL CRAFT ADVISORY FROM 1 AM TO 10 AM CDT SUNDAY FOR LMZ643-
     644.

&&

$$
UPDATE...MBK



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