Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 310217
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
917 PM CDT SAT AUG 30 2014

.UPDATE...UPPER LEVEL SHORT WAVE OVER CENTRAL WI AIDED BY WEAK
CONVERGENCE IN VICINITY OF SFC CDFNT RESULTING IN PERSISTENT ISOLD
-SHRA NEAR KPDC/KOVS. THESE -SHRA MOVING TO THE EAST AND WL AFFECT
PORTIONS OF IOWA/SAUK COUNTIES TOWARDS 03Z. IR IMAGERY SHOWING
COOLING CLOUD TOPS AND WEAK ELEVATED INSTABILITY SO POSSIBLE THESE
-SHRA WL HANG ON AND AFFECT KMSN AREA AROUND 05Z OR SO.

OTHERWISE...EXPECT AREAS OF FOG TO DEVELOP TOWARD AND AFTER
MIDNIGHT BUT MAY BE TEMPERED BY POSSIBLE STRATUS DEVELOPMENT AS
WEAK FRONTAL BOUNDARY SLOWS DOWN OVER SRN WI LATER TONIGHT. IN
ADDITION...SFC OBS SHOW QUITE A BIT OF STRATUS UPSTREAM OVER
CENTRAL WI BEHIND APPROACHING CDFNT WHICH WL LIKELY AFFECT NRN CWA
FOR A TIME. HENCE NOT ENOUGH CONFIDENCE TO EXPECT MORE WIDESPREAD
DENSE FOG LATE TNGT BUT MOST FAVORED AREA WOULD BE IN THE SOUTH. IF
STRATUS WERE TO DEVELOP LATE TONIGHT...WL LIKELY LINGER INTO SUN
MRNG OVER EASTERN AREAS AROUND AND NORTH OF WEAK FRONT.

&&

.AVIATION/06Z TAFS/...LOW LEVEL CONVERGENCE ALONG APPROACHING
FRONTAL BOUNDARY MAY TRIGGER AREAS OF IFR STRATUS LATER TONIGHT.
OTHERWISE...HIGHER STRATUS/MID CLOUDS IN THE WAKE OF CDFNT
ASSOCIATED WITH WEAK COLD AIR ADVECTION MAY AFFECT TAF SITES
OVERNIGHT AS WELL. BEFORE STRATUS DEVELOPS...WL LIKELY BE AREAS OF
FOG WHICH COULD BECOME DENSE FOR A TIME...ESPECIALLY AT KENW.

&&

.PREV DISCUSSION... /ISSUED 304 PM CDT SAT AUG 30 2014/

SHORT TERM...

REST OF THIS AFTERNOON AND TONIGHT - CONFIDENCE...MEDIUM
SURFACE TROUGH EXTENDS INTO SRN WI FROM DEPARTING LOW PRESSURE TO
OUR NORTHEAST. LOW LEVEL CONVERGENCE HAS BEEN MAXIMIZED VCNTY THIS
BOUNDARY WITH NUMEROUS SHOWERS. ONE SHORTWAVE/SPEED MAX LIFTING
NORTHEAST WITH ANOTHER VORT WRAPPING EAST FROM ERN MN/WRN WI. WILL
LINGER THESE SHRA INTO THE EARLY EVENING BEFORE INFLUENCE OF SECOND
VORT AND LOSS OF HEATING PUT AN END TO THE PRECIP. THEN FOCUS SHIFTS
TO CLEARING TREND AND FOG/STRATUS DEVELOPMENT LATER ON. DEW POINTS
REMAIN UP AND LOW LEVEL MOISTURE HAS INCREASED DUE TO THE NUMEROUS
SHRA. SO WITH A WEAK RIDGE OF HIGH PRESSURE SLIDING ACROSS EXPECTING
SOME FOG AND STRATUS TO TAKE SHAPE. THIS PLAYED OUT ON LLVL RH
PROGS AND MOS GUID. SOME GOOD CONSENSUS WITH THE LATTER...SO NOT
MUCH CHANGE TO GOING WX GRIDS IN THIS REGARD.

SUNDAY - CONFIDENCE...MEDIUM
WEAK SURFACE RIDGE SHIFTS EAST. SOUTHERLY FLOW STARTS TO DEVELOP.
ANY INFLUENCE OF APPROACHING COLD FRONT FROM THE PLAINS WILL REMAIN
TO OUR WEST. BY DAYS END 925 TEMPS MODIFY TO 21-24C. SO WARMER TEMPS
WITH SOME 80S RETURNING...ESPECIALLY IN THE WESTERN AND CENTRAL CWA.

SUNDAY NIGHT AND MONDAY...FORECAST CONFIDENCE IS HIGH

A RATHER STRONG SHORTWAVE EXITS THE PLAINS AND MOVES INTO THE
UPPER MISSISSIPPI VALLEY. THE LEAD SHORTWAVE MOVES ACROSS
WISCONSIN MONDAY WITH THE BEST DYNAMICS JUST TO THE NORTH AS A
110 KNOT JET MAX MOVES TO THE NORTH OF LAKE SUPERIOR...WITH A
SECOND SPEED MAX PUSHING ACROSS WISCONSIN. STRONG UPPER
DIVERGENCE MAINLY NEAR AND JUST TO THE WEST OF THE MISSISSIPPI
RIVER LATE SUNDAY NIGHT WEAKENS SOMEWHAT AND LIFTS NORTHEAST
ACROSS WISCONSIN MONDAY. THE STRONGEST UPWARD MOTION PUSHES INTO
SOUTH CENTRAL WISCONSIN BY SUNRISE AND ACROSS THE SOUTHEAST
MONDAY MORNING. THE 850/700 MB THERMAL RIDGE MOVES ACROSS SOUTHERN
WISCONSIN LATE SUNDAY NIGHT AND MONDAY MORNING. A 50 KNOT 850/700
MB  SPEED MAX MOVES ACROSS SOUTHERN WISCONSIN...BUT THE BEST
CONVERGENCE IS TO THE NORTH.

THE SURFACE LOW MOVES FROM JUST TO THE WEST AND NORTH WITH THE
COLD FRONT EXITING THE FAR SOUTHEAST AROUND NOON.

THE NAM KEEPS THE HEAVY RAIN JUST WEST SUNDAY NIGHT AND JUST NORTH
MONDAY MORNING. THE GFS/ECMWF BRINGS THE BAND OF MODERATE
PRECIPITATION AMOUNTS MORE INTO INTO SOUTH CENTRAL AND SOUTHEAST
WISCONSIN. THE NSHARP FORECAST SOUNDINGS INDICATE MAINLY A
MARGINAL SEVERE POTENTIAL.

MONDAY NIGHT AND TUESDAY...FORECAST CONFIDENCE IS HIGH

THE MAIN MID/UPPER TROUGH AXIS ENTERS WISCONSIN MONDAY NIGHT AND
REACHES LAKE HURON LATE TUESDAY AFTERNOON. THERE IS STILL SOME
UPPER DIVERGENCE AND 700 MB UPWARD MOTION SOUTHEAST MONDAY
EVENING. THE NAM AND GFS STILL HAVE SOME PRECIPITATION...WITH THE
NAM BRINGING MODERATE AMOUNTS WITH ZERO TO 1 KM MIXED LAYER CAPES
AROUND 900 JOULES/KG. MID AND LOW LEVELS THEN DRY. THERE IS STILL
SOME FAIRLY STEEP ZERO TO 3 KM LAPSE RATES OF 8.4 CELSIUS/KG ON
TUESDAY...BUT LOW LEVEL RH IS ONLY AROUND 64 PCT WITH MID LEVELS
AT 44 PCT. MODELS ARE DRY ON TUESDAY.

LONG TERM...

WEDNESDAY AND THURSDAY...FORECAST CONFIDENCE IS HIGH

THE GFS AND ECMWF HAVE A ZONAL FLOW ACROSS THE U.S./CANADIAN
BORDER AREA AS ANOTHER TROUGH DIGS A LITTLE ACROSS THE NORTHWEST
U.S.  THE UPPER FLOW BECOMING A LITTLE MORE WEST/SOUTHWEST LATER
WEDNESDAY AND THURSDAY.

WEAK HIGH PRESSURE MOVES ACROSS THE GREAT LAKES EARLY WEDNESDAY
WITH A WARM FRONT AND PRECIPITATION APPROACHING SOUTHERN
WISCONSIN WEDNESDAY NIGHT AND THURSDAY ON THE GFS WITH MODERATE
AMOUNTS OF PRECIPITATION.

THE 00Z ECMWF IS SLOWER AND DRIER...FOCUSING THE PRECIPITATION
OVER CENTRAL AND NORTHERN WISCONSIN THURSDAY.

FRIDAY AND SATURDAY...FORECAST CONFIDENCE IS MEDIUM

THE GFS AND ECMWF HAVE A WEST/SOUTHWEST FLOW ACROSS WISCONSIN
FRIDAY WITH A LARGE RIDGE ACROSS THE SOUTHERN U.S.

THE 12Z GFS AND 00Z ECMWF ARE NOT AS CONSISTENT WITH EACH OTHER
BY SATURDAY WITH THE SHORTWAVES ACROSS CANADA.

BY FRIDAY NIGHT THE ECMWF PUSHES A COLD FRONT INTO SOUTHERN
WISCONSIN...WHICH IS SLOWER ON THE GFS. LATER FRIDAY AND SATURDAY
BOTH MODELS PUSH THE FRONT TO THE SOUTH...WITH THE GFS MAINLY OVER
CENTRAL ILLINOIS AND THE UPPER OHIO VALLEY...WITH THE ECMWF
FARTHER SOUTH HAVING THE FRONT REACHING KENTUCKY. AS A RESULT BOTH
THE GFS AND ECMWF HAVE PRECIPITATION...WITH MODERATE TO HEAVY
AMOUNTS FRIDAY...WITH THE ECMWF DRYING THINGS ON SATURDAY.

AVIATION/00Z TAFS/...

LOW PRESSURE WILL CONTINUE TO MOVE NORTHEAST AWAY FROM WI
TONIGHT. A LARGE CU FIELD...MOSTLY VFR...PERSISTS DUE TO CYCLONIC
FLOW ALOFT. EXPECT THIS TO GRADUALLY DISSIPATE AS THE EVENING
WEARS ALONG. A NARROW RIDGE OF HIGH PRESSURE BUILDS IN BRINGING A
LIGHTER WIND REGIME. FOG/STRATUS DEVELOPMENT STILL ON TRACK WITH
THE LOW LEVEL MOISTURE...CLEARING SKIES AND THE LIGHT WIND REGIME.
WITH THE NAM/GFS MOS IN DECENT AGREEMENT BROUGHT VSBYS DOWN INTO
THE IFR CATEGORY...WITH A FEW LIFR CONDITIONS NOT OUT OF THE
QUESTION. INFLUENCE OF APPROACHING COLD FRONT ON SUNDAY HOLDS OFF
TO OUR WEST DURING THE DAY SO AFTER ANY MORNING FOG/STRATUS BURNS
OFF...EXPECT A QUIET VFR DAY BEFORE TSRA RETURNS SUNDAY NIGHT INTO
LABOR DAY.

MARINE...HOISTED A SHORT TERM SMALL CRAFT ADVISORY FROM WIND POINT
SOUTH TO WINTHROP HARBOR DUE TO SOUTHWEST WINDS GUSTING TO 22-25 KNOTS
AT TIMES. THIS IN LINGERING TIGHTER PRESSURE GRADIENT AHEAD OF SURFACE
TROUGH AXIS. EXPECT THE GRADIENT TO BECOME MORE BAGGY INTO THIS EVENING
AS HIGH PRESSURE DRAWS CLOSER.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

$$

UPDATE...MBK


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