Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 191618
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1118 AM CDT FRI SEP 19 2014

.UPDATE...

WITH THE SUNNY SKIES SOUTH WINDS AND WARM AIR ADVECTION...WILL
LIKELY HAVE TO RAISE MAX TEMPS A LITTLE.

&&

.AVIATION/18Z TAFS/...

VFR CONDITIONS EXPECTED WITH ONLY SCATTERED CUMULUS THIS AFTERNOON
THAT WILL BE VERY SHALLOW DUE TO THE STRONG CAP AROUND 5 THSD FT.

SOUTH WINDS WILL INCREASE TO 15 TO 25 KNOTS AS THE PRESSURE
GRADIENT TIGHTENS WITH THE APPROACH OF LOW PRESSURE AND A COLD
FRONT. THERE IS A CHANCE OF SHOWERS WITH ISOLATED THUNDERSTORMS
AFTER MIDNIGHT TONIGHT AS STORMS DEVELOP UPSTREAM NEAR THE FRONT
AND MOVE SLOWLY INTO THE AREA. EXPECT SOME MVFR CIGS/VSBYS AROUND
OR AFTER SUNRISE. DUE TO THE INCREASING MOISTURE AHEAD OF THE
FRONT. THE CHANCE FOR THUNDERSTORMS WILL CONTINUE THROUGH
SATURDAY.

&&

MARINE...

LOW PRESSURE APPROACHING THE AREA TODAY WILL RESULT IN SOUTH WINDS
REACHING SMALL CRAFT ADVISORY LEVELS THROUGH MID AFTERNOON ON
SATURDAY.  WAVES WILL BE ON THE INCREASE INTO TONIGHT.

WINDS WILL SHIFT TO THE WEST NORTHWEST IN THE WAKE OF A PASSING
COLD FRONT SATURDAY AFTERNOON...THUS MARINE CONDITIONS WILL BE
IMPROVING BY THEN.


&&

.PREV DISCUSSION... /ISSUED 325 AM CDT FRI SEP 19 2014/

TODAY...FORECAST CONFIDENCE IS HIGH.

PESKY LOW LEVEL MOISTURE TRAPPED UNDER AN INVERSION HAS RESULTED
IN AN EXPANDING LARGE LOW STRATUS FIELD ACROSS SOUTHERN WI. THIS
WOULD PROBABLY BE A WIDESPREAD DENSE FOG EVENT...EXCEPT WINDS JUST
ABOVE THE BOUNDARY LAYER ARE BLOWING PRETTY GOOD...THUS LIFTING IT
INTO MORE A STRATUS EVENT.

THESE CLOUDS SHOULD BLOW NORTH AND CLEAR OUT OF SOUTHERN
WISCONSIN FAIRLY QUICKLY THIS MORNING...AS A COMBO OF SUNSHINE AND
INCREASING SOUTHERLY WINDS WORK TO CLEAR IT OUT. THE REST OF THE
DAY SHOULD BE DECENT WITH A MIX OF SUNSHINE AND HIGH CLOUDS
SPILLING IN FROM THE NORTHWEST. TEMPS IN THE LOWER 70S WILL BE
CLOSE TO NORMAL LEVELS FOR THIS TIME OF YEAR.

TONIGHT...FORECAST CONFIDENCE IS MEDIUM.

A STRONG LOW LEVEL JET WILL LIKELY SUPPORT SOME CONVECTION
UPSTREAM THAT WILL EVENTUALLY WORK ITS WAY SOUTH INTO THE
AREA...MAINLY AFTER MIDNIGHT. THE PROBLEM IS THAT THE LOW LEVEL
JET WILL BE WEAKENING AND BE FOCUSED WELL OFF TO THE EAST WITH
TIME. HOWEVER...THERE IS A DECENT MID LEVEL TROF THAT WILL BE
DIGGING IN...BRINGING COOLER TEMPS UPSTAIRS.

SOME OF THE MESO MODELS ARE EXCITED ABOUT CONVECTION...WHILE THE
NAM ESSENTIALLY KEEPS THE AREA DRY GIVEN THE WEAKENING SUPPORT.
THE ECMWF IS IN BETWEEN THESE TWO CAMPS. THE GFS IS LOOKING WET
AFTER 06Z TONIGHT. AT 12Z SAT...THE SFC FRONT WILL LIKELY BE
LOCATED NORTHWEST OF THE CWA...MOVING IN DURING THE MORNING. WILL
KEEP THE POPS IN THE CHCY CATEGORY FOR TONIGHT.

SHORT TERM...SATURDAY THROUGH SUNDAY NIGHT...FORECAST CONFIDENCE
IS MEDIUM.

GFS/ECMWF/CANADIAN MODELS BRING SURFACE COLD FRONT SOUTHEAST
THROUGH THE AREA BY 00Z SUNDAY...WITH THE NAM JUST ENTERING THE
WESTERN COUNTIES BY THEN. 500 MB VORTICITY MAXIMUM SHIFTS THROUGH
THE AREA ON SATURDAY AS WELL...WITH 250 MB JET STREAK SHIFTING
SOUTHEAST INTO THE AREA. LOW LEVEL FRONTOGENESIS IS STRONGER ON
THE NAM THAN THE GFS SATURDAY...AS IT SHIFTS SOUTHEASTWARD.

AREA FORECAST SOUNDINGS SHOWING A CAP IN THE LOW LEVELS INTO THE
AFTERNOON...MIXING OUT BETWEEN 21Z SATURDAY AND 00Z SUNDAY.
HOWEVER...IF THE GFS/ECMWF/CANADIAN MODELS TIMING WITH THE FRONT
IS CORRECT...MOST OF THE CONVECTION MAY DEVELOP JUST TO THE SOUTH
AND EAST OF THE AREA. IT IS A CLOSE CALL...ESPECIALLY IN THE FAR
SOUTHEAST COUNTIES. KEPT LIKELY POPS IN THE FAR SOUTHEAST IN THE
AFTERNOON...CLOSEST TO THE FRONT...WITH LOWER POPS TO THE
NORTHWEST.

NAM MORE AGGRESSIVE WITH MEAN LAYER CAPE THAN GFS...1300 TO 1700
J/KG VERSUS UP TO 1000 J/KG ON GFS. STILL...STRONG DEEP LAYER
SHEAR OF 40 TO 50 PLUS KNOTS ARE SEEN ACROSS THE AREA.
THUS...THERE IS THE POTENTIAL FOR SEVERE STORMS WITH LARGE HAIL
AND DAMAGING WINDS. SPC DAY 2 OUTLOOK HAS AREAS SOUTHEAST OF A
PORT WASHINGTON TO MONROE LINE IN A SLIGHT RISK FOR SEVERE STORMS.
THIS SEEMS REASONABLE GIVEN THE AMOUNT OF MEAN LAYER CAPE AND DEEP
LAYER SHEAR WITH THE PASSING COLD FRONT.

STRONG 500 MB SHORTWAVE TROUGH THEN PUSHES SOUTHEAST THROUGH THE
REGION SATURDAY NIGHT INTO SUNDAY MORNING. ENOUGH LOW LEVEL
MOISTURE LINGERS WITH STEEP LOW LEVEL LAPSE RATES TO KEEP SHOWERS
IN FORECAST IN THE NORTHEAST COUNTIES LATER SATURDAY NIGHT INTO
SUNDAY. QUIET WEATHER IS EXPECTED ELSEWHERE ACROSS THE AREA
SUNDAY...ACROSS THE ENTIRE AREA SUNDAY NIGHT AS HIGH PRESSURE
PASSES TO THE SOUTHWEST.

WARM TEMPERATURES AND HUMID CONDITIONS ARE EXPECTED SATURDAY AHEAD
OF THE FRONT...WITH COOLER TEMPERATURES MOVING IN FOR SATURDAY
NIGHT INTO SUNDAY/SUNDAY NIGHT BEHIND IT.

LONG TERM...MONDAY THROUGH THURSDAY...FORECAST CONFIDENCE IS
MEDIUM.

GFS/ECMWF SHOWING DECENT AGREEMENT WITH NORTHWEST FLOW AT 500 MB
LINGERING MONDAY...BEFORE A WEAK RIDGE MOVES OVER THE REGION
MONDAY NIGHT INTO TUESDAY. HIGH PRESSURE AT THE SURFACE MOVES
ACROSS OR JUST SOUTH OF THE REGION...BRINGING QUIET WEATHER AND
NEAR NORMAL TEMPERATURES.

MODELS THEN TRY TO BRUSH THE AREA WITH 500 MB VORTICITY MAXIMA
WEDNESDAY INTO THURSDAY. THEY TRY TO BRING LIGHT QPF ACROSS
NORTHWESTERN PORTIONS OF THE AREA WEDNESDAY NIGHT...AND DRY
ELSEWHERE. SOME UNCERTAINTY HERE THIS FAR OUT. FOR NOW...USED
CONSENSUS MODEL POPS AND TEMPERATURES FOR THIS PERIOD.

AVIATION/12Z TAFS/...

A LARGE AREA OF IFR CIGS/VSBYS WILL LIFT NORTH QUICKLY THIS
MORNING AS SOUTHERLY WINDS INCREASE QUICKLY. ONCE THESE CLOUDS
MOVE OUT...LOOK FOR VFR CONDITIONS THROUGH THE REMAINDER OF THE
TAF PERIOD.

SOUTHERLY WINDS WILL INCREASE TO 15 TO 25 KNOTS AS THE PRESSURE
GRADIENT TIGHTENS WITH THE APPROACH OF LOW PRESSURE AND A COLD
FRONT. THERE IS A CHANCE OF THUNDERSTORMS AFTER MIDNIGHT TONIGHT
AS STORMS DEVELOP UPSTREAM NEAR THE FRONT AND MOVE SLOWLY INTO THE
AREA. THE CHANCE FOR STORMS WILL CONTINUE THROUGH SATURDAY.

MARINE...

LOW PRESSURE APPROACHING THE AREA TODAY WILL RESULT IN SOUTHERLY
WINDS INCREASING QUICKLY THIS MORNING. WINDS AND WAVES WILL REACH
SMALL CRAFT ADVISORY LEVELS BY MID MORNING AND CONTINUE THROUGH
MID AFTERNOON ON SATURDAY.

WINDS WILL SHIFT TO THE WEST NORTHWEST IN THE WAKE OF A PASSING
COLD FRONT SATURDAY AFTERNOON...THUS MARINE CONDITIONS WILL BE
IMPROVING BY THEN.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 PM CDT SATURDAY FOR LMZ644>646.

     SMALL CRAFT ADVISORY UNTIL 4 PM CDT SATURDAY FOR LMZ643.

&&

$$

UPDATE...HENTZ
TODAY/TONIGHT AND AVIATION/MARINE...DAVIS
SATURDAY THROUGH THURSDAY...WOOD



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