Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 181700 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1200 PM CDT MON AUG 18 2014

.UPDATE...

LOW CLOUDS CONTINUE TO MIX OUT ACROSS MOST OF THE AREA. REMAINING
AREAS SHOULD MIX OUT BY EARLY THIS AFTERNOON. SHOULD SEE SCATTERED
TO BROKEN DIURNAL CUMULUS CLOUDS DEVELOP THIS AFTERNOON AS WELL.
HIGHS LOOK ON TRACK IN THE UPPER 70S TO AROUND 80 INLAND...WITH
LOWER TO MID 70S NEAR THE LAKE WITH ONSHORE WINDS.

LATEST MESOSCALE MODELS TRYING TO DEVELOP AN AREA OF SHOWERS AND
STORMS FROM CENTRAL TO SOUTHWEST WISCONSIN BY 21Z THIS
AFTERNOON...THEN SLIDING SOUTHEAST THROUGH THE AREA LATE THIS
AFTERNOON AND THIS EVENING. THEY ALSO TRY TO BRING SECONDARY AREA
OF CONVECTION EASTWARD INTO THE AREA LATER THIS EVENING AND
OVERNIGHT.

500 MB VORTICITY MAXIMUM WILL MOVE INTO THE AREA BY 06Z
TUESDAY...WITH A WEAKER ONE MOVING IN BY 00Z TUESDAY. MAIN ONE
MOVES INTO THE AREA LATER TONIGHT INTO TUESDAY. BETTER UPWARD
VERTICAL MOTION SEEN WITH EVENING VORTICITY MAXIMUM THAN WEAKER
ONE LATER THIS AFTERNOON. TOUGH TO PICK OUT ANY DECENT LOW LEVEL
BOUNDARIES UNTIL MAIN COLD FRONT PUSHES EAST THROUGH THE AREA ON
TUESDAY.

AREA FORECAST SOUNDINGS SHOWING GOOD LOW LEVEL MIXING WITH 1000
TO 1300 J/KG OF MEAN LAYER CAPES DEVELOPING BY LATE THIS
AFTERNOON...WEAKENING SOMEWHAT TONIGHT BEFORE INCREASING ON
TUESDAY. DEEP LAYER SHEAR IS 20 TO 25 KNOTS LATER THIS AFTERNOON
AND TONIGHT...AND 25 TO 30 KNOTS ON TUESDAY.

SPC HAS PUT AREAS WEST OF A DELLS...TO MADISON...TO MONROE LINE
IN A SLIGHT RISK FOR SEVERE STORMS LATER THIS AFTERNOON AND
TONIGHT. HOWEVER...FEEL SEVERE STORMS MAY BE HARD TO COME BY GIVEN
MODEST DEEP LAYER SHEAR AND LACK OF WELL DEFINED LOW LEVEL
BOUNDARY. CERTAINLY COULD SEE SMALL HAIL AND BRIEF GUSTY WINDS
WITH STRONGER STORMS.

FOR NOW...CUT BACK ON POPS IN THE SOUTHEAST COUNTIES THIS
AFTERNOON. WILL WATCH TRENDS AND ADJUST HIGHER END POPS IN THE
WEST IF NEEDED. SLOW STORM MOTION VECTORS WITH PRECIPITABLE WATER
VALUES AROUND 1.80 INCHES SUGGEST HEAVY RAINFALL IS POSSIBLE WITH
THE STORMS LATER THIS AFTERNOON AND TONIGHT. THIS CERTAINLY WOULD
BE WELCOME ACROSS THE AREA.

&&

.AVIATION/18Z TAFS/...

ANY REMAINING LOW CLOUDS WILL MIX OUT BY EARLY THIS
AFTERNOON...WITH SCATTERED TO BROKEN VFR CATEGORY DIURNAL CUMULUS
CLOUDS DEVELOPING. LIGHT SOUTHEAST WINDS ARE EXPECTED AT THE
EASTERN SITES...WITH SOUTH WINDS AT MADISON.

SHOWERS AND STORMS WITH MVFR CEILINGS AND VISIBILITIES WILL REACH
MADISON BY 02Z TUESDAY...AND THE EASTERN SITES BY 05Z TUESDAY.
THEY WILL THEN BE ON AND OFF THROUGH THE OVERNIGHT HOURS INTO
TUESDAY MORNING. SHOULD SEE SOME IFR CEILINGS AND VISIBILITIES
LATER TONIGHT INTO TUESDAY MORNING. COULD SEE SMALL HAIL AND BRIEF
GUSTY WINDS WITHIN STRONGEST STORMS.

SOUTH WINDS SHOULD PICK UP LATER TONIGHT AND BECOME SOUTHWEST ON
TUESDAY...SHIFTING WEST TUESDAY AFTERNOON AS COLD FRONT CROSSES
THE AREA. SHOWERS AND STORMS REMAIN POSSIBLE TUESDAY
AFTERNOON...BUT WILL NOT MENTION IN TAFS AT THIS TIME DUE TO
UNCERTAINTY.

&&

.MARINE...MAY SEE PATCHY FOG DEVELOP ACROSS THE NEARSHORE WATERS
OF LAKE MICHIGAN TONIGHT...AS MORE MOISTURE MOVES INTO THE AREA
AND OVER THE LAKE. NOT ANTICIPATING DENSE FOG AT THIS
TIME...THOUGH IS MAY BE POSSIBLE IF WINDS ARE LIGHT ENOUGH.

&&

.PREV DISCUSSION... /ISSUED 332 AM CDT MON AUG 18 2014/

SHORT TERM...

TODAY AND TONIGHT...FORECAST CONFIDENCE - MEDIUM.

LIGHT WINDS AND CLEAR SKIES ON THE WESTERN PERIPHERY OF THE
INCREASING STRATUS AND FOG SHIELD EXPANDING OVER EASTERN CWA HAS LED
TO DENSE FOG IN THE JANESVILLE AREA EXTENDING EAST TO AROUND
ELKHORN.  EXPECT ST AND FOG SHIELD TO CONTINUE EXPANDING WWD INTO
MORE OF SOUTH CENTRAL WI NEXT SEVERAL HOURS.  WL NEED TO KEEP AN EYE
ON OBS AND WEBCAMS AS PATCHY DENSE FOG CONTINUES TO EXPAND FARTHER
NORTH.  FOR NOW WL ISSUE DENSE FOG ADVY FOR FAR SOUTHERN THREE
COUNTIES AS WALWORTH CO DISPATCH REPORTED AREAS OF DENSE FOG IN THE
COUNTY AS WELL.  EXPECT DENSE FOG TO SPREAD INTO GREEN COUNTY NEXT
SEVERAL HOURS.  WEBCAMS SHOW DENSE FOG MORE PATCHY IN SHEBOYGAN AREA
DESPITE ONE HALF MILE VSBY AT KSBM. VSBYS CONTINUE TO FLUCTUATE AT
KSBM AND KETB.

OTRW...WEAK MID-LEVEL SHORT WAVE OVER SRN WI MAY CAUSE A FEW SHOWERS
OR TSTORMS TO GRAZE NORTHWEST CWA EARLY THIS MRNG.  FOR NOW WL KEEP
POPS SMALL BUT MAY NEED TO BUMP UP TO SCT WORDING IN THIS AREA.
BETTER CHANCE FOR MORE WIDESPREAD CONVECTION THIS AFTERNOON AND
TONIGHT.  THIS AFTN...UPSTREAM STRONGER SHORT WAVE OVER ERN SD MOVES
ACROSS SRN WI THIS AFTN AS DEEPER COLUMN MOISTURE SETTLES IN.
BETTER ISENTROPIC OMEGA ON 310 THETA SURFACE ALONG WITH LOWER
CONDENSATION PRESSURE DEFICITS THIS AFTN AS WELL.  HENCE WL CONTINUE
WITH HIGH CHANCE TO LOW CATEGORICAL POPS IN THE WEST LATE THIS AFTN.
SPREAD CATEGORICAL POPS EWD ACROSS CWA DURING THE NIGHT AS LOW LEVEL
JET PIVOTS ACROSS SRN WI AND INCREASES A BIT AS LOW PRESSURE ALOFT
STRENGTHENS A BIT.  PWAT VALUES INCREASE TO 1.5 TO 1.9 INCHES DURING
THIS PERIOD WITH APPROACHES TWO STANDARD DEVIATIONS AT KGRB FOR MID-
AUGUST.  BESIDES MOISTURE...SEVERAL OTHER FACTORS FAVOR HEAVY
RAINFALL POTENTIAL TONIGHT INCLUDING DEEP WARM CLOUD DEPTH OF 9500
FT AND CORFIDI VECTORS LESS THAN 10 KNOTS UNTIL LATE TONIGHT.  ADDED
HEAVY RAINFALL MENTION TO FORECAST FOR LATE AFTN AND TNGT AND WL
INCLUDE IN HWO.  DRIER AIR ROTATING AROUND DEEPING LOW PRESSURE
SHOULD HELP TO DECREASE CONVECTION LATER TONIGHT.

TUESDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE MEDIUM.

THE 500MB SHORTWAVE TROUGH WILL STALL OVER THE WESTERN GREAT LAKES
THROUGH WEDNESDAY MORNING. ONGOING SHOWERS AND THUNDERSTORMS MONDAY
NIGHT WILL TAPER OFF FROM SOUTHWEST TO NORTHEAST ACROSS THE MKX
FORECAST AREA ON TUESDAY AS DRY AIR WRAPS INTO THE REGION. EVEN
THOUGH MANY MODELS END PRECIP IN SOUTH CENTRAL WI BY TUE
AFTERNOON...OPTED TO KEEP LOW POPS IN. THE UPPER LOW WILL STILL BE
OVERHEAD...LEADING TO STEEP LOW LEVEL LAPSE RATES AND THE POTENTIAL
FOR A FEW SHOWERS OR THUNDERSTORMS DUE TO WEAK VORTICITY MAXIMA
ROTATING IN.

WEAK FLOW AND RECENT RAIN SHOULD LEAD TO PATCHY FOG OR AREAS OF
FOG...OVER SOUTH CENTRAL WI LATER TUE NIGHT. STRATUS CLOUDS COULD BE
A LIMITING FACTOR FOR DENSE FOG.

THE UPPER LOW WILL SHIFT EAST ON WEDNESDAY AND WEAK RIDGING WILL
MOVE IN. MOST OF THE MODELS ARE DRY ACROSS THE MKX FORECAST
AREA...SO FINALLY WENT DRY FOR THE FORECAST. WARMER AIR WILL BE
WORKING ITS WAY INTO SOUTH CENTRAL WI AS WELL.

LONG TERM...

WEDNESDAY NIGHT THROUGH THURSDAY...FORECAST CONFIDENCE MEDIUM.

AN 850MB BAROCLINIC ZONE OVER THE MIDWEST WILL LIFT NORTHWARD INTO
SOUTHERN WI WEDNESDAY NIGHT. THE NOSE OF THE LOW LEVEL JET WILL BE
POINTING RIGHT INTO NORTHEAST IOWA BY LATE THU NIGHT AT THE SAME
TIME THE RIGHT ENTRANCE REGION OF THE UPPER JET MOVES OVERHEAD.
MODELS ARE SUGGESTING A CONVECTIVE COMPLEX WILL DEVELOP IN THE
MN/IA/WESTERN WI AREA AND SLIDE EAST THROUGH SOUTHERN WI EARLY THU
MORNING. WITH HIGH PRECIPITABLE WATER VALUES OF NEARLY 2 INCHES
SPREADING IN...PERIODS OF HEAVY RAIN WILL BE POSSIBLE. PRECIP SHOULD
TAPER OFF THU AFTERNOON AS THE SYSTEM WEAKENS.

PRECIP WILL HAVE A LARGE IMPACT ON TEMPERATURES. THE FORECAST HIGHS
AROUND 80 ARE ASSUMING SHOWERS AND STORMS.

FRIDAY THROUGH SUNDAY...FORECAST CONFIDENCE LOW.

THAT 850MB BAROCLINIC ZONE WILL WAFFLE OVER SOUTHERN/CENTRAL WI
THROUGH THE WEEKEND. THE 00Z ECMWF CAME INTO BETTER AGREEMENT WITH
THE GFS WITH THE FRONT STALLING OVER SOUTHERN WI. SHOWERS AND
THUNDERSTORMS WILL RE-DEVELOP AT TIMES ALONG THIS FRONT...
ESPECIALLY EACH AFTERNOON/EVENING.

THIS SHOULD BE A WARM AND HUMID PERIOD.

AVIATION/12Z TAFS/...

MOSTLY STRATUS WITH AREAS OF FOG CONTINUING TO SPREAD WWD ACROSS
EASTERN HALF OF CWA EARLY THIS MRNG.  ON WESTERN PERIPHERY OF ST
FIELD...CLEAR SKIES AND LIGHT WINDS HAS ALLOWED PATCHY DENSE FOG TO
DEVELOP IN KJVL AREA WHICH MAY SPREAD NORTH INTO KMSN NEXT SEVERAL
HOURS.  OTRW...MOIST LOW LEVEL FLOW ALLOWING OTHER AREAS OF MVFR
STRATUS AND FOG TO DEVELOP FARTHER SOUTHWEST.  THINKING LOW CLOUDS
AND FOG WL SLOWLY ERODE LATER THIS MRNG INTO THE AFTN WITH LOW
CLOUDS POTENTIALLY RETURNING TNGT ALONG WITH MORE WIDESPREAD
CONVECTION.

MARINE...

FOG IS THE MAIN ISSUE FOR NEXT SEVERAL DAYS.  MAY BE SOME PATCHY FOG
AROUND THIS MRNG IN LIGHT MOIST FLOW.  WL NEED TO WATCH FOR FOG
RETURNING TNGT AS SLY SFC WNDS CARRY HIGHER DEWPTS AND MOISTURE
ACROSS LAKE MI NEARSHORE WATERS.  WINDS LOOK TO REMAIN BELOW SMALL
CRAFT ADVY LEVELS FOR THE FORESEEABLE FUTURE.

&&

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

$$

UPDATE...WOOD
TODAY/TONIGHT AND AVIATION/MARINE...MBK
TUESDAY THROUGH SUNDAY...MRC


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