Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 030237
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
937 PM CDT SAT MAY 2 2015

.UPDATE...EXPECT SHOWERS AND ISOLD THUNDER OVER ERN IA TO MOVE OFF
TO THE SOUTHEAST NEXT SEVERAL HOURS AS MID-LEVEL SHORT WAVE
PASSES INTO CENTRAL IL. THIS WL ALLOW LOW LEVEL JET TO REFOCUS
INTO SRN WI REGION DURING THE LATE NIGHT. COLUMN PWAT VALUES
EXPECTED TO DOUBLE TO AROUND 1 INCH BY 12Z. SFC DEWPTS WL REMAIN
STEADY OR RISE THROUGH THE 40S. DUE TO EXPECTED LOW LEVEL MOISTURE
CONVERGENCE AND WEAK 700H SHORT WAVE...WL CONTINUE SMALL CHANCE
FOR SHOWERS AND ISOLD THUNDER LATE TONIGHT INTO SUN MRNG ACROSS
MOST OF THE AREA. SLY BREEZES AND RETURNING CLOUDS WL KEEP TEMPS
MILD...BUT DID NEED TO LOWER SHEBOYGAN A FEW DEGREES.

&&

.AVIATION/06Z TAFS/...VFR CONDITIONS TO CONTINUE THROUGH SUN.
STRENGTHENING LOW LEVEL JET OVERNIGHT WILL RESULT IN WINDS
APPROACHING LOW LEVEL WIND SHEAR CRITERIA AT KMSN...AS DEPICTED
BY RAP BUFKIT SOUNDINGS. APPEARS WIND SHEAR TO REMAIN JUST BELOW
THRESHOLD SO WL HOLD OFF ON INTRODUCING INTO KMSN TAF AT THIS
TIME. WL INCLUDE THUNDER IN MOST TAFS LATER SUN EVE.

&&

.MARINE...SHALLOW INVERSION OVER NEAR SHORE WATERS OVERNIGHT WILL
OCCASIONALLY RESULT IN WIND GUSTS OF 15 TO 20 KNOTS AWAY FROM THE
SHORE. OTHERWISE...STRONGER LOW LEVEL MIXING ON SUNDAY WILL RESULT
IN WIND GUSTS TO 25 KNOTS DEVELOPING DURING THE MORNING. SMALL
CRAFT ADVISORY WILL REMAIN IN EFFECT. THUNDERSTORMS WITH THE
POTENTIAL FOR STRONG WIND GUSTS WILL AFFECT THE NEAR SHORE WATERS
AFTER 02Z/MON.

&&

.PREV DISCUSSION... /ISSUED 325 PM CDT SAT MAY 2 2015/

SHORT TERM...

TONIGHT AND SUNDAY...FORECAST CONFIDENCE...HIGH

A WEAK SHORTWAVE WILL MOVE THROUGH TONIGHT INTO SUNDAY
MORNING...BRINGING A CHANCE FOR SHOWERS. BEST CHANCE WILL BE LATER
TONIGHT THROUGH THROUGH THE MIDDLE OF SUNDAY MORNING ACROSS THE
SOUTHERN HALF OF THE FORECAST AREA. MAY HEAR A RUMBLE OR TWO OF
THUNDER AS INSTABILITY SLOWLY INCREASES. SHOULD BE MAINLY DRY THEN
LATE MORNING INTO THE AFTERNOON...WITH DECREASING CLOUDS AS WELL.

WITH CLOUDS EXPECTED AGAIN TONIGHT AND MILD TEMPS ALOFT...LOWS WILL
LIKELY BE IN THE 50S. TEMPS WILL VERY PLEASANT AGAIN SUNDAY...WITH
HIGHS IN THE UPPER 70S TO LOW 80S...THOUGH IT WILL BE BREEZIER THAN
TODAY. ALONG SHORE WINDS WILL LIKELY BRING SOME COOLER AIR INTO
LAKESHORE AREAS MAINLY NORTH OF MILWAUKEE...PARTICULARY TOWARD THE
SHEBOYGAN AREA.

SUNDAY NIGHT AND MONDAY...FORECAST CONFIDENCE IS HIGH.

A MID AND UPPER LEVEL SHORTWAVE MOVES ACROSS SOUTH CENTRAL CANADA
AS THE 250 MB UPPER JET MAX INCREASES TO 125 KNOTS AS IT MOVES
ACROSS THE LAKE SUPERIOR REGION. THE STRONGEST UPPER DIVERGENCE
AFFECTS NORTHERN AND WESTERN AREAS OF THE FORECAST AREA EARLY
SUNDAY NIGHT...AND WEAKENS AS IT SAGS SOUTHEAST. THEN AS THE
SHORTWAVE MOVES INTO SOUTHEAST CANADA THE RIGHT ENTRANCE REGION OF
THE JET BEGINS TO INCREASE THE UPPER DIVERGENCE AGAIN LATER MONDAY
AFTERNOON.

AN 850/700 MB WARM AXIS PUSHES INTO SOUTHERN WISCONSIN...BUT COOLS
SOMEWHAT LATER SUNDAY NIGHT AND MONDAY...ESPECIALLY AT 700 MB. THE
STRONGEST 850/700 MB WINDS ARE ALREADY ACROSS THE UPPER GREAT
LAKES BY MIDNIGHT...WITH WIND SPEEDS WEAKENING LATER SUNDAY NIGHT
AND MONDAY. THE 850/700 MB RH INCREASES SUNDAY NIGHT...BUT DOES
NOT SATURATE UNTIL LATER MONDAY...ESPECIALLY IN THE FAR SOUTH.

MODELS IN DECENT AGREEMENT WITH SLIDING COLD FRONT INTO SOUTHERN
WISCONSIN FROM THE NORTHWEST SUNDAY NIGHT THEN EXITING THE FAR
SOUTHEAST MONDAY AFTERNOON. EXPECT A LINE OF THUNDERSTORMS TO
PUSH INTO SOUTHERN WISCONSIN SUNDAY NIGHT...THEN WEAKEN AS THE
LOW/MID LEVEL CONVERGENCE WEAKENS WITH THE BEST MID/UPPER LEVEL
FORCING STAYING NORTH BEFORE MOVING OFF.

THE NAM HAS THE HIGHEST ZERO-1 KM CAPE...ALMOST 2000 JOULES/KG
NORTHWEST TOWARDS THE DELLS AT 7PM CDT SUNDAY...DUE TO THE
TYPICAL NAM BIAS OF HIGHER LOW LEVEL MOISTURE. THE CAPE DROPS TO
AROUND 500 JOULES/KG LATE SUNDAY NIGHT. SOME POTENTIAL WITH
INSTABILITY RISING AGAIN MONDAY NEAR THE ILLINOIS BORDER BEFORE
THE COLD FRONT EXITS AND LAKE COOLING INCREASES. SPC DAY 2
OUTLOOK HAS OUR FAR NORTHWEST TOWARDS THE DELLS IN A SLIGHT RISK
OF SEVERE NOW WITH THE REST OF SOUTH CENTRAL AND NORTHWEST
PORTIONS OF SOUTHEAST WISCONSIN CONTINUING IN THE MARGINAL
CATEGORY.

MONDAY NIGHT AND TUESDAY...FORECAST CONFIDENCE IS HIGH.

A ZONAL WEST TO EAST FLOW EXTENDS ACROSS THE U.S./CANADIAN BORDER
WITH A WEAKENING UPPER JET MAX ACROSS THE NORTHERN GREAT LAKES.
STILL SOME WEAK UPPER LEVEL DIVERGENCE DUE TO THE PROXIMITY OF THE
JETS RIGHT ENTRANCE REGION.

THE 850/700 MB SOUTHWEST FLOW INCREASES AGAIN AS IT LIFTS TO THE
NORTH. THIS INCREASES THE 850/800 MB MOISTURE CONVERGENCE AND 700
MB UPWARD MOTION AS IT PUSHES TO THE NORTH. THE 700 MB RH BECOMES
SATURATED MONDAY NIGHT WITH THE SATURATION LIFTING INTO CENTRAL
WISCONSIN TUESDAY. THE 950/850 MB PATTERN IS SIMILAR...JUST NOT
QUITE SATURATED. MEANWHILE THE SURFACE FRONT STAYS JUST SOUTH OF
THE ILLINOIS BORDER. THE NAM SOUNDINGS INDICATE A LOW STRATUS OVER
MUCH OF SOUTHERN WISCONSIN...WITH SOME ELEVATED CAPE. HOWEVER THE
MODEL BRINGS THE SOUNDING TO MOIST ADIABATIC DUE TO THE GENERATED
PRECIPITATION.

LONG TERM...

TUESDAY NIGHT AND WEDNESDAY...FORECAST CONFIDENCE IS HIGH.

AN UPPER RIDGE BUILDS INTO WISCONSIN FROM THE OHIO RIVER VALLEY
AS A SHORTWAVE TROUGH PUSHES INTO THE CENTRAL PLAINS.

LOW PRESSURE EXPANDS ACROSS THE PLAINS WITH AN INCREASING SOUTH
FLOW ACROSS WISCONSIN. THIS LIFTS THE SURFACE BOUNDARY NORTH INTO
SOUTHERN WISCONSIN...AND APPROACHES CENTRAL WISCONSIN WEDNESDAY
AFTERNOON. AS A RESULT THE SHOWERS AND SCATTERED THUNDERSTORM
POTENTIAL WOULD LIFT NORTH ACROSS MUCH OF SOUTHERN WISCONSIN...
WITH THE FAR SOUTH POTENTIALLY PRECIPITATION FREE WEDNESDAY
AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...FORECAST CONFIDENCE IS MEDIUM.

THE SHORTWAVE TROUGH LIFTS NORTHEAST AND WEAKENS. THE 12Z GFS IS
FASTER WITH THE TROUGH THAN THE 00Z ECMWF. THE MODELS ARE MAINLY
PRECIP FREE OVER MOST OF THE AREA...WITH SOUTHERN WISCONSIN IN A
WARM AND INCREASINGLY MOIST AIRMASS.

FRIDAY AND SATURDAY...FORECAST CONFIDENCE IS MEDIUM.

THE WEAKENING SHORTWAVE CONTINUES TO LIFT NORTHEAST TOWARD
WISCONSIN AND THE LAKE SUPERIOR AREA.

AS LOW PRESSURE MOVES NORTHEAST FROM MINNESOTA TOWARDS THE LAKE
SUPERIOR AREA...A TRAILING COLD FRONT ENTERS SOUTH CENTRAL
WISCONSIN FRIDAY AFTERNOON AND EVENING...EXITING THE SOUTHEAST
SATURDAY. THE 12Z GFS STALLS THE FRONT ACROSS SOUTHERN WISCONSIN.
THIS WILL KEEP THE SHOWER AND THUNDERSTORM CHANCES THROUGH THE
PERIOD ON THE GFS...BUT WOULD DRY THINGS OUT BEHIND THE FRONT
FRIDAY ON THE 00Z ECMWF.

AVIATION/00Z TAFS/...

VFR CONDITIONS ARE EXPECTED THROUGH THE DAY SUNDAY.

A WEAK WAVE WILL MOVE THROUGH TONIGHT INTO SUNDAY...POSSIBLY KICKING
OFF A FEW SHOWERS AND MAYBE A RUMBLE OR TWO OF THUNDER. BETTER
CHANCE FOR WIDESPREAD SHOWERS/STORMS WILL COME SUNDAY EVENING AND
OVERNIGHT AS A COLD FRONT MOVES THROUGH. WILL PROBABLY SEE LOWER
VSBYS WITH ANY MODERATE TO HEAVY RAIN.

MARINE...

A SMALL CRAFT ADVISORY IS BEING ISSUED THIS AFTERNOON FOR
SUNDAY...MID MORNING UNTIL EVENING. SOUTH TO SOUTHWEST WINDS WILL
GUST TO 25 KNOTS. WAVES SHOULD STAY GENERALLY LESS THAN 4 FEET GIVEN
THE WIND DIRECTION.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM CDT SUNDAY FOR
     LMZ643>646.

&&

$$
UPDATE...MBK


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