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Area Forecast Discussion

000
FXUS63 KMKX 011515
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1015 AM CDT SAT AUG 1 2015

.AVIATION/18Z TAFS/...VFR CONDITIONS AT LEAST INTO THIS EVENING.
LEADING EDGE OF WAA/MOIST ADV GENERATING ISOLD SHRA WITHIN LARGE
ACCAS FIELD ACRS CNTRL/SRN WI. THIS LIKELY TO GIVE WAY TO MORE
SUNSHINE AS THE DAY WEARS ON. MAIN FOCUS FOR CONVECTIVE
DEVELOPMENT ARRIVES LATER TONIGHT INTO MONDAY MORNING AS MORE
PRONOUNCED LLJ AIMS INTO SRN WI. STILL SOME TRACK UNCERTAINTY ON
MCS BUT OVERALL MOIST ADVECTION WITH 850 LLJ AND SHORTWAVE
ACTIVITY WARRANTS THE CHANCE OF STORMS LATER TONIGHT INTO SUNDAY
MORNING. POCKETS OF MVFR CIGS/VSBYS WITH ANY STRONGER STORMS.
MESOSCALE DETAILS AFTER OVERNIGHT/EARLY MORNING STORMS WILL
DICTATE STORM EVOLUTION/SEVERITY ON SUNDAY AFTERNOON/EVENING AS
SURFACE LOW AND COLD FRONT INTERACT WITH POTENTIALLY VERY UNSTABLE
AIRMASS.

PC

&&

.PREV DISCUSSION... /ISSUED 329 AM CDT SAT AUG 1 2015/ 

TODAY - CONFIDENCE...MEDIUM.

COMPACT STRONG SURGE OF LOW LEVEL MOISTURE AND WARM AIR ADVECTION 
TRIGGERING ISOLATED SHOWERS AND STORMS IN SOUTHEAST MN.  SFC 
DEWPOINTS INCREASE FROM THE LOWER 50S ACROSS SRN WI TO THE UPPER 50S 
TO LOWER 60S ACROSS NRN IA/SRN WI. STORMS ARE MOVING SOUTHEAST ALONG 
DENSITY DISCONTINUITY AND WILL LIKELY AFFECT WESTERN AND SOUTHERN 
PORTIONS OF CWA THIS MRNG AS SURGE OF LOW LEVEL MOISTURE FLUX 
CONVERGENCE PASSES ACROSS THE AREA.  FOR NOW...WL GO WITH ISOLD 
WORDING BUT MAY HAVE TO INCREASE TO MORE SCT IN WEST FOR AN HOUR OR 
TWO.  SURGE OF MOISTURE FLUX CONVERGENCE MOVES SOUTH OF BORDER BY 
AFTN SO DRY CONDITIONS EXPECTED.  925H TEMPS WARM TO 22-24C SO 
DAYTIME TEMPS SHOULD EASILY RETURN TO THE 80S. WINDS NOT EXPECTED TO 
BE AS BREEZY TODAY DUE TO SLIGHTLY WEAKER PRESSURE GRADIENT BUT 
SHOULD STILL BE IN THE 10 TO 20KT RANGE.  THIS SHOULD BE STRONG 
ENOUGH TO PREVENT LAKE BREEZE FROM DEVELOPING...OR ELSE HOLDING IT 
CLOSE TO THE SHORE THIS AFTN.  

TONIGHT - CONFIDENCE...MEDIUM.

EXPECTING A QUIET EVENING ACROSS MOST OF THE AREA.  MODERATE MID 
LEVEL STEERING FLOW IS EXPECTED TO CARRY AMPLIFYING LOW PRESSURE 
TROF INTO THE NORTHERN PLAINS TONIGHT.  STRENGTHENING LOW LEVEL JET 
AHEAD OF THIS TROF TO 35 TO 45 KNOTS PIVOTS INTO CENTRAL AND SRN WI 
AFT 06Z/SUN. STRONG SURGE OF MOISTURE FLUX CONVERGENCE SPREADS INTO 
WESTERN CWA LATE TNGT.  MESO-SCALE CONVECTIVE SYSTEM EXPECTED TO 
DEVELOP IN THE NORTHERN PLAINS THIS EVENING AND FOLLOW EXPANDING 
INSTABILITY GRADIENT TO THE EAST-SOUTHEAST WHICH MAY CARRY MCS INTO 
SRN WI.  NOT ENOUGH CONFIDENCE AT THIS POINT TO BUMP UP POPS TO 
LIKELY DUE TO DISAGREEMENT BETWEEN SHORT TERM GUIDANCE ON TRACK OF 
MCS.  HOWEVER WITH LLJ SPREADING ACROSS SRN WI LATE TNGT...WL CONT 
HIGHER CHANCE POPS AND SWITCH TO SCT WORDING IN WEST.  ELEVATED 
CAPES EXCEED 1000 J/KG LATE TNGT IN SOUTH CENTRAL WI WITH 30KTS OF 
BULK SHEAR.  HENCE SLT RISK FOR SEVERE FOCUSING ON HAIL AND WIND 
SEEMS WARRANTED. 

SUNDAY...FORECAST CONFIDENCE...MEDIUM

STILL QUITE A FEW QUESTIONS WITH THE SUNDAY FORECAST. FIRST...WILL 
LIKELY BE DEALING WITH THE EXITING OVERNIGHT THUNDERSTORM COMPLEX AT 
DAYBREAK. WILL PROBABLY BE QUITE A BIT OF CONVECTIVE DEBRIS LIMITING 
HEATING EARLY IN THE DAY. LOW LEVEL JET WILL SLIDE SOUTHEASTWARD 
ACROSS THE FORECAST AREA DURING THE DAY. STRONG LOW LEVEL FLOW WITH 
THIS JET AHEAD OF AN APPROACHING COLD FRONT WILL DRAW WARM AND HUMID 
CONDITIONS INTO SOUTHERN WISCONSIN. DEPENDING ON HOW QUICKLY CLOUDS 
CAN MOVE OUT AND INSTABILITY BUILDS...COULD SEE SOME DEVELOPMENT 
AHEAD OF THE FRONT BY EARLY AFTERNOON. BETTER CHANCE WILL COME LATE 
AFTERNOON AND EVENING AS THE FRONT PUSHES SOUTHEAST THROUGH THE 
FORECAST AREA. EVEN IF 2M DEWPOINTS ARE A BIT OVERDONE...STILL 
SHOULD SEE PLENTY OF INSTABILITY GIVEN ENOUGH HEATING. MID LEVEL 
LAPSE RATES PROGGED TO BE IN THE 7-8C RANGE BY MID/LATE AFTERNOON. 
BULK SHEAR FROM 0-6 KM STILL AROUND 35-40 KNOTS IN MODELS. NOT 
SURPRISING SPC HAS THE SOUTHEAST HALF OF THE FORECAST IN A SLIGHT 
RISK FOR SEVERE STORMS...WITH THE NORTHWEST IN A MARGINAL RISK. 

OTHER CONCERN FOR SUNDAY IS HOW WARM IT GETS. NAM/GFS 925 MB AND 2 
METER TEMPS QUITE WARM. LATEST ECMWF HAS TRENDED THAT WAY...BUT IS 
NOT QUITE AS WARM AS NAM/GFS SOLUTIONS. OPTED TO WARM TEMPS A BIT 
FROM PREVIOUS FORECAST...BUT DID NOT GO AS NEARLY AS WARM AS WARMEST 
MODELS WOULD SUGGEST GIVEN A GOOD DEAL OF UNCERTAINTY IN TIMING OF 
PRECIP AND CLOUD COVER. POTENTIAL EXISTS FOR EVEN WARMER TEMPS IF
THE SUN DOES COME OUT FOR A SIGNIFICANT AMOUNT OF TIME.

MONDAY THROUGH FRIDAY...FORECAST CONFIDENCE...MEDIUM

EXPECT DRY WEATHER MONDAY AS HIGH PRESSURE BEGINS TO BUILD IN FROM 
THE NORTHWEST AND MODEL PRECIPITABLE WATER VALUES DROP TO AROUND
HALF OF AN INCH. SHOULD BE DRY THEN TUESDAY AND WEDNESDAY UNDER
THE HIGH. HAVE SOME LOW POPS IN THE FORECAST FOR LATER THURSDAY
INTO FRIDAY AS ANOTHER WAVE TRAVERSES THE AREA.

HIGH TEMPS MON/TUE LOOK TO BE WITHIN A COUPLE DEGREES OF 
NORMAL...COOLING A FEW DEGREES FOR WED-FRI UNDER PERSISTENT
NORTHWEST FLOW ALOFT.

AVIATION/12Z TAFS/...EXPECT ISOLD SHOWERS TO AFFECT SOUTH CENTRAL 
WI EARLY THIS MORNING.  MAY EVEN BE A RUMBLE OF THUNDER.  MAY NEED 
TO USE A VCTY REMARK IN KMSN TAF FOR AN HOUR OR TWO.  OTRW VFR 
CONDITIONS FOR THE BULK OF THE TAF PERIOD.  SCT T MAY RESULT IN 
LOWER CIGS LATE TONIGHT...ESPECIALLY AT KMSN.  

MARINE...NOT AS BREEZY TODAY ACROSS THE NEARSHORE WATERS DUE TO 
WEAKER PRESSURE GRADIENT AND SLIGHTLY WEAKER WINDS IN THE LOW 
LEVELS.  STILL MAY HAVE GUSTS TO AROUND 20 KTS LATER THIS MORNING 
AND AFTERNOON.

SMALL CRAFT CONDITIONS MAY RETURN LATE TONIGHT BUT MORE LIKELY ON 
SUNDAY AHEAD OF A COLD FRONT THAT WILL MOVE ACROSS THE NEAR SHORE 
WATERS LATE IN THE AFTERNOON AND EARLY EVENING.  SOME STRONG TSTORMS 
MAY ACCOMPANY FRONTAL PASSAGE.

&&

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

$$
TODAY/TONIGHT AND AVIATION/MARINE...MBK 
SUNDAY THROUGH FRIDAY...DDV