159  
FXUS63 KMKX 260514 AAC  
AFDMKX  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI  
1214 AM CDT WED JUL 26 2017  
   
UPDATE
 
 

 
   
AVIATION(06Z TAFS)
 
 
MIDDLE TO HIGH CLOUDS WILL CONTINUE TO PUSH THROUGH THE AREA  
OVERNIGHT INTO WEDNESDAY. CEILINGS WILL LOWER TO AROUND 4000 FEET  
OR SO WITH THE SHOWERS AND THUNDERSTORMS MOVING THROUGH THE AREA  
LATER WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CEILINGS DOWN TO  
2500 FEET ARE POSSIBLE LATER WEDNESDAY NIGHT, ALONG WITH LIGHT  
FOG.  
 
SOUTH WINDS OVERNIGHT WILL BECOME WEST SOUTHWEST ON WEDNESDAY,  
GRADUALLY WEAKENING DURING THE DAY. WINDS WILL SHIFT TO THE NORTH  
BEHIND THE COLD FRONT LATER WEDNESDAY NIGHT.  
 
SCATTERED SHOWERS AND THUNDERSTORMS WILL PUSH THROUGH THE AREA  
LATER WEDNESDAY AFTERNOON INTO WEDNESDAY EVENING. THEY SHOULD EXIT  
LATER WEDNESDAY NIGHT. BEST CHANCE FOR SEVERE STORMS AND LOCALLY  
HEAVY RAINFALL WILL BE SOUTHWEST OF MADISON. GUSTY WINDS AND  
HAIL REMAIN POSSIBLE ELSEWHERE DURING THIS TIME.  
 
WOOD  
 

 
   
PREV DISCUSSION
 
(ISSUED 951 PM CDT TUE JUL 25 2017)  
 
UPDATE...  
 
ELEVATED CONVECTION, DRIVEN BY LOW LEVEL JET POINTING INTO  
NORTHEAST AND EAST CENTRAL WISCONSIN, CLIPPED NORTHEASTERN  
SHEBOYGAN COUNTY. THIS ACTIVITY WILL CONTINUE TO SHIFT AWAY FROM  
THE AREA LATE THIS EVENING. THERE ARE A FEW WEAK SHOWERS IN  
NORTHWESTERN PORTIONS OF THE AREA, BUT THESE ARE NOT EXPECTED TO  
LAST VERY LONG.  
 
KEPT LOW POPS GOING FOR LATER TONIGHT ACROSS THE FAR NORTHERN  
PORTIONS OF THE AREA, IN CASE SOME SHOWERS OR STORMS FROM THE  
NORTH DRIFT INTO THOSE AREAS. MOST OF THE NIGHT SHOULD REMAIN  
DRY. MESOSCALE MODELS HAVE ANY APPROACHING ELEVATED CONVECTION  
LATER TONIGHT INTO WEDNESDAY MORNING WEAKENING AND STAYING JUST  
NORTH OF THE AREA, WHERE THE BETTER UPWARD VERTICAL MOTION FIELDS  
ARE EXPECTED TO BE LOCATED.  
 
00Z NAM RUN CONTINUES TO FOCUS THE MAIN AREA OF CONVECTION FOR  
LATER WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT TO THE SOUTHWEST OF  
THE AREA. THE LOW LEVEL JET FOCUSES MOSTLY IN THIS AREA. IT DOES  
HAVE SOME CONVECTION AFFECTING THE FORECAST AREA, AS THE COLD  
FRONT MOVES THROUGH THE AREA WEDNESDAY NIGHT.  
 
DEEP LAYER BULK SHEAR IS AT 25 TO 35 KNOTS, WITH VARYING AMOUNTS  
OF MEAN LAYER CAPE, DEPENDING ON THE MODEL. THINK CURRENT SLIGHT  
RISK AREA FROM SPC LOOKS GOOD FOR NOW, AND MAY NEED A FURTHER  
NUDGE TO THE SOUTHWEST IF OTHER MODELS ARE SIMILAR TO THE NAM.  
LOCALLY HEAVY RAINFALL IS POSSIBLE WITH HIGH PRECIPITABLE WATER  
VALUES AND OTHER FAVORABLE HEAVY RAINFALL PARAMETERS.  
 
WOOD  
 
MARINE...  
 
SOUTH WINDS WILL LINGER AT 10 TO 20 KNOTS ACROSS THE NEARSHORE  
WATERS OF LAKE MICHIGAN OVERNIGHT. THIS WILL BRING WAVES OF 2 TO 4  
FEET, HIGHEST TOWARD THE SHEBOYGAN AREA. WINDS WILL GRADUALLY  
WEAKEN AND BECOME MORE WEST SOUTHWEST ON WEDNESDAY, WITH LOWER  
WAVES.  
 
SCATTERED THUNDERSTORMS SHOULD MOVE THROUGH THE AREA LATER  
WEDNESDAY AFTERNOON AND NIGHT. GUSTY WINDS AND HAIL ARE POSSIBLE  
IN ANY STRONGER STORMS.  
 
GUSTY NORTHEAST WINDS THURSDAY INTO PERHAPS FRIDAY WILL BRING  
BUILDING WAVES OF 3 TO 6 FEET TO THE NEARSHORE WATERS OF LAKE  
MICHIGAN. THESE WAVES MAY LINGER AS LATE AS FRIDAY NIGHT. A SMALL  
CRAFT ADVISORY MAY BE NEEDED FOR THIS PERIOD.  
 
WOOD  
 
PREV DISCUSSION... (ISSUED 648 PM CDT TUE JUL 25 2017)  
 
UPDATE...  
 
AVIATION(00Z TAFS)...  
 
WINDS WILL BECOME SOUTH AND DECREASE SOMEWHAT TONIGHT, THEN BECOME  
WEST SOUTHWEST ON WEDNESDAY. MIDDLE TO HIGH CLOUDS WILL CONTINUE  
TO PUSH THROUGH THE AREA EARLY THIS EVENING, BEFORE MORE EXTENSIVE  
CLOUDS MOVE IN LATER THIS EVENING AND OVERNIGHT. MIDDLE TO HIGH  
CLOUDS WILL LINGER ON WEDNESDAY, WITH SOME DIURNAL CUMULUS  
POSSIBLE.  
 
LOWER CEILINGS TO 3500 FEET WITH SCATTERED THUNDERSTORMS SHOULD  
MOVE EAST THROUGH THE AREA LATE WEDNESDAY AFTERNOON AND EVENING.  
VISIBILITIES DOWN TO AROUND OR BELOW ALTERNATE MINIMUMS ARE  
POSSIBLE WITH ANY STORMS, ALONG WITH GUSTY WINDS AND HAIL. BEST  
SHOT FOR STRONG TO SEVERE STORMS, AND HEAVY RAINFALL, WILL BE  
SOUTH AND WEST OF MADISON DURING THIS TIME.  
 
WOOD  
 
PREV DISCUSSION... (ISSUED 226 PM CDT TUE JUL 25 2017)  
 
DISCUSSION...  
 
TONIGHT - CONFIDENCE...MEDIUM  
PRECIP SHIELD ASSOCIATED WITH MORNING MCS HAS SHOWN A CONSIDERABLE  
DIMINISHING TREND AND THIS WILL CONTINUE. PLENTY OF DEBRIS  
CLOUDINESS WILL REMAIN INTO THIS EVENING. WITH THE SURFACE HIGH  
SHIFTING OFF TO THE EAST THE RETURN FLOW WILL PICK UP. ALREADY  
SEEING A BOOST IN THE DEW POINTS BACK TO NEAR OR ABOVE 60 HERE  
WITH HIGHER NUMBERS UPSTREAM POISED TO MOVE IN OUR DIRECTION. AT  
THIS TIME IT APPEARS THE BETTER FOCUSING WILL BE TO OUR NORTH  
WHERE 500 MILLIBAR VORT ACTION/LOWER LEVEL FRONTAL CONVERGENCE  
AND AXIS OF LLJ MEET UP. CANNOT RULE OUT SOME PARTS OF OUR NORTH  
BEING GRAZED SO HAVE SOME POPS IN PLACE THERE A BIT LATER ON.  
 
WEDNESDAY - CONFIDENCE...MEDIUM  
MAIN FOCUS WILL BE ON CONVECTIVE TRENDS WITH APPROACHING FRONTAL  
BOUNDARY FROM THE NORTHWEST. WHILE THE PRIMARY FRONT STAYS TO OUR  
NORTHWEST DURING THE DAY, THERE IS A 500 MILLIBAR SHORTWAVE THAT  
IS PROGGD TO ARRIVE DURING THE AFTERNOON HOURS. THERE IS ALSO SOME  
DIVERGENCE NOTED WITH THE WEST/EAST MOVING JET STREAM ACROSS THE  
UPPER LAKES REGION. THE PROGS SUGGEST THE WESTERN AND NORTHERN CWA  
WOULD HAVE THE BETTER CHANCES FOR TSRA DEVELOPMENT SO HAVE A NW-SE  
GRADIENT IN POPS. SOME MODEL DIFFERENCES NOTED ON DEGREE OF  
INSTABILITY DURING THE AFTERNOON WITH WIND FIELDS NOT EXACTLY  
OVERLY FAVORABLE. 925 TEMPS RISE INTO THE LOW/MID 20S CELSIUS SO  
EXPECT PLENTY OF TEMPS REACHING THE MID 80S.  
 
WEDNESDAY NIGHT...FORECAST CONFIDENCE IS HIGH.  
 
THERE'S VERY GOOD CONSENSUS AMONG THE MODELS THAT THE COLD FRONT  
WILL PUSH SOUTH THROUGH THE AREA, LIKELY EXITING SOUTHERN  
WISCONSIN SHORTLY AFTER MIDNIGHT. THE ARRIVAL OF A MID LEVEL SHORT  
WAVE TRACKING IN FROM NE/IA WILL HELP TO ENERGIZE THE ACTIVITY IN  
THE AFTERNOON AND EVENING ACROSS SOUTHERN WI...ESPECIALLY THE  
SOUTHWEST. SHEAR IS DECENT ENOUGH, BUT NOT IMPRESSIVE. CAPE  
VALUES ARE QUITE VARIED AMONG THE MODELS WITH THE NAM MOST  
AGGRESSIVE. BUT AGAIN, NOTHING TOO EXTREME. IN FACT, THE NAM IS  
MOST AGGRESSIVE WITH MANY OF THE FIELDS AND IS LIKELY SUFFERING  
FROM IT'S USUAL CONVECTIVE FEEDBACK ISSUES. THE MODELS DO TEND TO  
FOCUS THE HEAVIEST RAINFALL AMOUNTS ACROSS OUR WESTERN FORECAST  
AREA, WITH LIGHTER AMOUNTS IN THE EAST. HOWEVER, AS WE'VE SEEN  
WITH ALL OF THE EVENTS THIS MONTH, WE NEED TO REMAIN OPEN TO  
SHIFTS IN THESE PLACEMENTS ONCE THE ACTIVITY GETS GOING. THERE  
WILL BE ONGOING CONVECTION PRIOR TO IT ARRIVING IN SOUTHERN WI AND  
HOW THAT EVOLVES WILL CERTAINLY HAVE AN INFLUENCE ON SUBSEQUENT  
DEVELOPMENT.  
 
THE SPC HAS BACKED OFF ON THE SLIGHT RISK ACROSS SOUTHERN  
WISCONSIN. KEEPING IT MAINLY SOUTH AND WEST OF A BARABOO TO  
WATERTOWN TO PADDOCK LAKE LINE. OUR FAR SOUTHEAST AND NORTHEAST  
ARE NOW JUST IN A MARGINAL RISK. I LIKE THIS ADJUSTMENT, FOCUSING  
MORE ON OUR SOUTHWEST, CLOSER TO THE NOSE OF THE LOW LEVEL JET AND  
EXPECTED COLD POOLING BEHAVIOR.  
 
THURSDAY THROUGH SATURDAY...FORECAST CONFIDENCE IS HIGH.  
 
HIGH PRESSURE BUILDS ACROSS THE AREA DURING THIS PERIOD. THERE IS  
A POTENT SHORT WAVE THAT DROPS NORTHEAST WISCONSIN LATER THURSDAY  
AFTERNOON THROUGH THURSDAY NIGHT. THERE MAY BE SOME DIURNAL  
SHOWERS ACROSS THE NORTH THAT COULD SNEAK INTO OUR NORTHERN CWA  
BEFORE THEY DIE AT SUNSET. TEMPS AND HUMIDITY WILL BE COMFORTABLE.  
 
SUNDAY AND MONDAY...FORECAST CONFIDENCE IS LOW.  
 
THE GFS IS SUGGESTING A COLD FRONT COULD BE THE FOCUS FOR SHOWERS  
AND STORMS DURING THIS PERIOD, WHILE THE ECMWF IS MUCH DRIER  
LOOKING. WE'LL CARRY SMALL CHANCES FOR THIS POTENTIAL.  
 
AVIATION(18Z TAFS)...MCS HAS DECAYED WITH JUST DEBRIS CLOUDINESS  
REMAINING. PROGS HINTING AT SOME MVFR CLOUDINESS FORMING LATER  
TONIGHT INTO SC WI. MAIN CONCERN WILL BE WITH POTENTIAL FOR  
STRONG TO SEVERE STORMS LATER WEDNESDAY/WEDNESDAY EVENING THOUGH  
SOME DEVELOPMENT POSSIBLE PRIOR TO 00Z ESP IN SC WI.  
 
MARINE...WINDS AND WAVES EXPECTED TO REMAIN BELOW SMALL CRAFT  
LEVELS INTO WEDNESDAY. HOWEVER, A SOUTHERLY FLOW WILL BE IN PLACE  
AHEAD OF A FRONTAL BOUNDARY. SCATTERED STORMS, A FEW STRONG, ARE  
MOST LIKELY WEDNESDAY AFTERNOON INTO THE EVENING HOURS.  
 
BEACHES...  
 
BRISK NORTHEAST WINDS BY THURSDAY AFTERNOON WILL LIKELY RESULT IN  
HIGH SWIM RISK CONDITIONS ALONG THE LAKE MICHIGAN SHORE.  
 

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

 
 

 
 
UPDATE...WOOD  
TONIGHT/THURSDAY AND AVIATION/MARINE...COLLAR  
THURSDAY NIGHT THROUGH WEDNESDAY...DAVIS  
 
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