Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 312021
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
321 PM CDT SUN AUG 31 2014

.SHORT TERM...

.TONIGHT - CONFIDENCE...MEDIUM
LAKE BREEZE BOUNDARY HAS PUSHED WELL INLAND PER TERMINAL DOPPLER
AND OBS. STABLE MARINE LAYER CLEARING OUT CU FIELD IN FAR ERN CWA.
HOWEVER STRATUS AND SOME FOG STILL CLOSE TO THE SHORE AND OVER THE
LAKE. MID LEVEL RIDGING WILL BREAK DOWN AND GIVE WAY TO A TROUGH
APPROACHING FROM THE PLAINS. SURFACE PRESSURE GRADIENT WILL TIGHTEN
UP AHEAD THE LOW AND ASSOCIATED COLD FRONT. THIS WILL HELP TO BRING
DEW POINTS BACK INTO THE UPPER 60S/LOW 70S. LOW LEVEL JET PROGGD TO
STRENGTHEN FROM THE SOUTH AS THE NIGHT WEARS ON. MODELS IN DECENT
AGREEMENT IN BRINGING LEADING EDGE OF TSRA COMPLEX INTO WESTERN CWA
LATE IN THE NIGHT IN CLOSE PROXIMITY TO DCVA OF LEADING SHORTWAVE.

.LABOR DAY - CONFIDENCE...MEDIUM
INFLUENCE OF LEAD AND PRIMARY SHORTWAVE ASSOCIATED WITH APPROACHING
UPPER TROUGH IS PROGGD TO HAVE GREATEST IMPACT DURING THE MORNING HOURS.
AT A TIME WHEN DIURNAL DRIVEN INSTABILITY IS AT A MINIMUM. HOWEVER
SHORTWAVE IS NEGATIVE TILT AND H8 LLJ WILL BE DECENT AT 30-40 KNOTS.
SO WHILE TIME OF DAY SUGGESTS STORMS WILL BE BELOW SVR LIMITS...THERE
WILL BE SOME FAVORABLE FACTORS COMING INTO PLAY. MID LEVEL LAPSE RATES
ARE NOT SUPPORTIVE OF HAIL BUT 0-6 SHEAR WILL BE INCREASING WITH SOME
HIGHER DOWNDRAFT CAPE NOTED.

BULK OF EVIDENCE SUPPORTS LATER DAY DEVELOPMENT OCCURS TO OUR
SOUTHEAST THOUGH THE NAM DOES REDEVELOP A BAND OF CONVECTION BETWEEN
LATER IN THE DAY. MEANWHILE GFS AND ECMWF ARE DRY. SPC HAS TRIMMED
THE SWODY2 TO INCLUDE JUST THE SOUTHEAST HALF SUGGESTING ANY AFTN
DEVELOPMENT WOULD FOCUS IN THE SE 1/2 OF CWA CLOSER TO PROXIMITY OF
FRONTAL BOUNDARY IF IT HASN/T ALREADY SHIFTED SOUTHEAST OF THE AREA.
WILL HAVE TO WATCH THIS SCENARIO AS LOW LEVEL BOUNDARY MAY SLOW UP
ENOUGH TO ALLOW FURTHER DESTABILIZATION TO OCCUR AFTER ANY MORNING
CONVECTION WORKS THROUGH. UPPER JET CORE/UPPER DIVERGENCE WITHIN
BROADLY CYCLONIC FLOW WILL STILL BE FAVORABLE FACTORS FOR LATER DAY
DEVELOPMENT...SO SCENARIO DOES EXIST FOR A COUPLE DIFFERENT ROUNDS
OF CONVECTION...MRNG/ERLY AFTERNOON AND THEN ANOTHER LATER IN THE
AFTERNOON.

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

THE MAIN MID/UPPER TROUGH AXIS ENTERS WISCONSIN MONDAY NIGHT AND
REACHES LAKE HURON TUESDAY AFTERNOON. THERE IS A SECOND AREA OF
MODERATE UPPER DIVERGENCE AND WEAK 700 MB UPWARD MOTION IN THE
SOUTHEAST MONDAY EVENING WITH SOUTHEAST WISCONSIN IN THE LEFT
ENTRANCE REGION OF THE 250 MB 110 KNOT UPPER JET. ZERO TO 1 KM
MIXED LAYER CAPE IS STILL AROUND 2200 JOULES/KG IN THE KENOSHA
AREA WITH NSHARP STILL INDICATING A SEVERE POTENTIAL...ESPECIALLY
WITH HAIL AS WET BULB ZERO HEIGHTS LOWER TO 9500 FEET.

THE NAM HAS A LINE OF PRECIPITATION WITH THE FRONT ACROSS MUCH OF
THE FORECAST AREA DURING THE EVENING. HOWEVER THE GFS AND 00Z
ECMWF ARE DRY. THE HIGH RES ARW AND NMN IS ALSO DRIER.

THERE IS STILL SOME FAIRLY STEEP ZERO TO 3 KM LAPSE RATES OF 8.2
CELSIUS/KG ON TUESDAY...BUT ONLY A SHALLOW CUMULUS CLOUD LAYER IS
IMPLIED ON THE DRIER NAM. THE 12Z GFS AND 00Z ECMWF DO BRING SOME
SPOTTY LIGHT PRECIPITATION...MAINLY TO THE NORTH OF MILWAUKEE AND
MADISON DURING THE AFTERNOON. HOWEVER THE GFS SOUNDINGS LOOK
SIMILAR TO THE NAM AND PREFER TO KEEP THE FORECAST DRY GIVEN THE
LOW GFS MOS POPS.

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

THE GFS AND ECMWF HAVE A ZONAL FLOW ACROSS THE U.S./CANADIAN
BORDER AREA AS A TROUGH DIGS A LITTLE INTO THE NORTHWEST U.S.

WEAK HIGH PRESSURE MOVES ACROSS THE GREAT LAKES EARLY WEDNESDAY
WITH LOW LEVEL WARM AIR ADVECTION. THE 12Z GFS AND 00Z ECMWF ARE
DRY ACROSS SOUTHERN WISCONSIN...BUT THE NAM DOES BRING IN LIGHT
PRECIPITATION INTO SOUTH CENTRAL WISCONSIN.

.LONG TERM...

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

THE UPPER FLOW BECOMES A LITTLE MORE WEST/SOUTHWEST THURSDAY AS
THE NORTHWEST U.S. TROUGH BEGINS TO MOVE EAST ACROSS SOUTHWEST
CANADA.

A WARM FRONT AND PRECIPITATION MOVES ACROSS SOUTHERN WISCONSIN
BY WEDNESDAY NIGHT ON THE 00Z ECMWF AND EARLY THURSDAY MORNING ON
THE GFS. AS A RESULT THE BULK OF THE SHOWERS AND THUNDERSTORMS ARE
TO THE NORTH ON THE ECMWF...BUT OCCURS WEDNESDAY NIGHT ON THE GFS
WITH SOME HEAVY RAINFALL.

.FRIDAY AND SATURDAY...FORECAST CONFIDENCE IS HIGH

THE GFS AND ECMWF HAVE A WEST/SOUTHWEST FLOW ACROSS WISCONSIN AS A
SHORTWAVE MOVES ACROSS SOUTH CENTRAL CANADA AND THE UPPER GREAT
LAKES. MEANWHILE A LARGE RIDGE EXTENDS ACROSS THE SOUTHERN U.S.

BOTH THE 12Z GFS AND 00Z ECMWF PUSH A COLD FRONT ACROSS MOST OF
SOUTHERN WISCONSIN THURSDAY NIGHT AND FRIDAY MORNING.

LATER FRIDAY AND SATURDAY BOTH MODELS PUSH THE FRONT TO THE
SOUTH...REACHING KENTUCKY BY SATURDAY. AS A RESULT BOTH THE GFS
AND ECMWF HAVE PRECIPITATION...WITH MODERATE TO HEAVY AMOUNTS
MAINLY THURSDAY NIGHT AND SATURDAY MORNING...WITH BOTH THE GFS AND
ECMWF NOW DRYING THINGS ON SATURDAY.

.SUNDAY...FORECAST CONFIDENCE IS HIGH

THE SHORTWAVE MOVES ACROSS SOUTHEAST CANADA WITH A WEST/NORTHWEST
UPPER FLOW ON THE GFS. THE ECMWF IS MORE ZONAL WITH A WEAK TROUGH
OVER THE UPPER MIDWEST.

A LARGE SURFACE HIGH IS EXPECTED TO EXTEND ACROSS THE GREAT LAKES
REGION.

&&

.AVIATION/00Z TAFS/...

VFR CU FIELD WILL GRADUALLY DISSIPATE WITH
EASING OF THERMAL TROUGH AND LOSS OF DIURNAL HEATING. LOW LEVEL WARM
AIR ADVECTION INCREASES AHEAD OF ADVANCING COLD FRONT FROM THE
PLAINS. EXPECTING AREA OF STORMS TO AFFECT SRN WI LATE
TONIGHT...AFTER 09Z FROM KMSN WEST AND THEN OVERSPREADING THE
REMAINDER OF SRN WI DURG THE MORNING HOURS...AROUND 09-15Z.
DEVELOPMENT LATER IN THE DAY WILL HINGE ON WHERE SURFACE BOUNDARY
ENDS UP AND WHETHER ENOUGH INSTABILITY CAN DEVELOP AHEAD OF THE
BOUNDARY. BULK OF MODELS POINTING TOWARDS LATER DEVELOPMENT
SOUTHEAST OF WI THOUGH 12Z NAM HINTED AT LATE DAY/EARLY DEVELOPMENT
ALONG LINGERING SURFACE BOUNDARY IN SRN/ERN WI.

&&

.MARINE...WITH PRESSURE GRADIENT TIGHTENING UP AHEAD OF COLD
FRONT...WILL HOIST SMALL CRAFT ADVISORY FROM 15-23Z MONDAY. WINDS
SHOULD GUST TO 25 KNOTS FROM THE SW.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM CDT MONDAY FOR
     LMZ643>646.

&&

$$

TONIGHT/MONDAY AND AVIATION/MARINE...COLLAR
MONDAY NIGHT THROUGH SUNDAY...HENTZ



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