000
FXUS63 KMKX 170250
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
950 PM CDT THU MAY 16 2013

.UPDATE...BEEFED UP CLOUD COVER FOR MUCH OF THE NIGHT AS EXPECT
UPSTREAM CONVECTION TO CONTINUE SPREADING NORTHEAST. ALSO...WEAKER
LOW LEVEL WARM AIR AND MOISTURE ADVECTION TRIGGERING A SMALL LINE
OF SHOWERS IN EASTERN IA SOUTH OF KDBQ. BOTH HRRR AND WRF-4L CARRY
CONVECTION FARTHER EAST INTO SOUTH CENTRAL AND PORTIONS OF
SOUTHEAST WI BY 12Z. WHILE LOW TO MID LEVEL LAYER RH
INCREASES...LAYER Q-VECTOR CONVERGENCE ALSO INCREASES LATE
TONIGHT. ALREADY INCREASED EASTWARD EXTENT AND PUSHED START TIME
UP SLIGHTLY...BUT MAY NEED TO PUSH UP EVEN FARTHER AND EXPAND INTO
PARTS OF SOUTHEAST WI.

&&

.AVIATION/06Z TAFS/...VFR CONDITIONS TO CONTINUE. THREAT FOR
THUNDER INCREASES FRI MRNG AND CONTINUES INTO THE
EVENING...ESPECIALLY AT KMSN. HOWEVER UNCERTAINTY REGARDING TIMING
SO WL CONT TO USE VCNTY REMARK. DRIER AIR FEED IN EASTERN AREAS SO
WL NOT INTRODUCE ANY T ATTM.

&&

.PREV DISCUSSION... /ISSUED 331 PM CDT THU MAY 16 2013/

VERY SHORT TERM...TONIGHT AND FRIDAY. FORECAST CONFIDENCE...
MEDIUM

A SLIGHT CHANCE FOR SHOWERS ACROSS THE NORTHWEST FORECAST AREA WAS
HELD ONTO THROUGH EARLY EVENING. CURRENTLY...THERE IS A LOT OF
CUMULUS DEVELOPMENT IN THE NORTHEAST...BUT NO SIGNS OF
PRECIPITATION. MAY HAVE TO REMOVE THESE POPS BY LATE AFTERNOON IF
LACK OF DEVELOPMENT PERSISTS. MODELS HAVE BACKED OFF AS WELL...SO
LOOKING LESS LIKELY BY THE HOUR. DEW POINT DEPRESSIONS ARE ON THE
ORDER OF 40 DEGREES AT THE MOMENT ACROSS THE NORTHWEST...SO THE DRY
AIR IS LIKELY CONTRIBUTING TO THE LACK OF DEVELOPMENT.

SHOULD BE DRY THEN THROUGH THE MAJORITY OF THE NIGHT. THE HRRR TRIES
TO SNEAK SOME ACTIVITY INTO THE SW A BIT EARLIER THAN OTHER
MODELS...BUT GENERALLY HELD OFF ON POPS UNTIL EARLY TOMORROW
MORNING. AS THE LAKE AIR MASS CONTINUES TO PUSH INLAND UNDER EASTERLY
WINDS...LOWS TONIGHT SHOULD NEAR NORMAL VALUES...MAINLY IN THE UPPER
40S TO LOW 50S.

WILL HAVE A BAROCLINIC ZONE STRETCHED NORTHWEST TO SOUTHEAST ACROSS
THE FORECAST AREA ON FRIDAY...WHILE A WEAK SHORTWAVE APPROACHES THE
AREA. THESE FEATURES WILL LIKELY COMBINE TO KICK OFF SHOWER AND
THUNDERSTORM ACTIVITY TOMORROW...PARTICULARLY ACROSS THE WEST AND
SOUTHWEST TOWARD THE MILDER AIR. A COOL AND STABLE AIR MASS OFF THE
LAKE WILL LIKE INHIBIT DEVELOPMENT IN THE EAST...SO KEPT POPS LOW.
WILL SEE GOOD SPREAD IN HIGH TEMPS TOMORROW...WITH HIGHS LIKELY NOT
GETTING OUT OF THE 50S ALONG THE LAKESHORE UNDER ONSHORE WINDS...TO
THE LOW 70S IN THE SOUTHWEST.

SHORT TERM...FRIDAY NIGHT THROUGH SUNDAY.

FRIDAY NIGHT...FORECAST CONFIDENCE

MODELS TAKE PRECIPITATION MAXIMA AT THE START OF THE PERIOD TO THE
NORTH AND SOUTH OF THE FORECAST AREA WITH DEPARTING SHORT WAVES.
LINGERING Q-VECTOR CONVERGENCE SUPPORT A GRADIENT OF CHANCE
POPS...WITH THE HIGHER CHANCES NORTH...DIMINISHING AFTER 06Z
SATURDAY. WITH WARM FRONT JUST PUSHING INTO THE FAR SW...WILL SEE A
NEARLY 10-DEGREE DIFFERENCE WITH OVERNIGHT LOWS...WITH UPPER 40S IN
THE NORTHEAST AND UPPER 50S IN THE FAR SW.

SATURDAY...FORECAST CONFIDENCE MEDIUM.

ENOUGH INSTABILITY AS DAYTIME HEATING/MIXING KICK IN...AND LOW-LEVEL
CONVERGENCE AS WARM FRONT STALLS AND BECOMES A STATIONARY FRONT
THROUGH THE MIDDLE PORTIONS OF THE CWA...TO WARRANT LOW-END POPS.
SOME OF THE HIGHER INSTABILITY IS PREDICATED ON HIGHER THAN
EXPECTED MODEL SURFACE DEW POINTS...A RECENT PROBLEM ON THE
MODELS...SO HOLDING TO ONLY SLIGHT CHANCE POPS APPEARS
APPROPRIATE. WILL SEE A STRONG TEMPERATURE CONTRAST ACROSS THE
STATIONARY BOUNDARY WITH MID-UPPER 70S IN THE SW 1/2....AND UPPER
60S TO LOW 70S NE HALF.

SATURDAY NIGHT...FORECAST CONFIDENCE HIGH.

RIDGING AHEAD OF DEEPENING WAVE KEEPS AREA DRY. EASTERLY WINDS BRING
UPPER 40S-LOW 50S ALONG THE KETTLE MORAINE AND EAST...AND IN THE MID
TO UPPER 50S TO THE WEST WITH LOW 60S IN THE SOUTHWEST.

LONG TERM...

THIS PERIOD DOMINATED BY IMPACT OF CLOSED...NEARLY-STACKED LOW AS IT
MOVES/FILLS OVER THE UPPER MIDWEST. CHANCES FOR THUNDER EACH PERIOD
FROM SUNDAY NIGHT INTO WEDNESDAY WITH LOBES OF VORTICITY ROTATING
AROUND CENTRAL CIRCULATION PROVIDING LIFT TO A WARM...MOIST UNSTABLE
AIR MASS FEEDING INTO THE REGION ON SRLY FLOW AHEAD OF TROUGH. CIPS
ANALOGS HAS INCREASING PROBABILITIES MOVING INTO SW WI MONDAY/MONDAY
NIGHT...WITH SPC DAY 4-8 COMPOSITE OUTLOOK BRUSHING SOUTHWEST
WISCONSIN ON DAYS 4 AND 5.

SOME QUESTION AS TO EVOLUTION OF SYSTEM...12Z ECMWF SLOWLY OPENS
THE SYSTEM AND MOVES IT SOUTHEAST AS IT PHASES WITH A SHORT WAVE
DROPPING THROUGH EASTERN ONTARIO/WESTERN QUEBEC...WHILE THE GFS
HAS THE LOW FILL AND SHEAR OUT OVER THE WESTERN GREAT LAKES.
EITHER SOLUTION KEEPS THE MAJORITY OF THE EXTENDED WITH PCPN
CHANCES UNTIL THE REMNANT LOW/TROUGH DROPS SOUTHEAST BY
THURSDAY/THURSDAY NIGHT. SHOULD SEE MODE CHANGE FROM THUNDER TO
RAIN SHOWERS WEDNESDAY NIGHT AND THURSDAY AS MID-LEVEL OCCLUSION
PUSHES THE MORE UNSTABLE AIR MASS TO THE EAST.

AVIATION/00Z TAFS/...

VFR CONDITIONS WILL PERSIST THROUGH FRIDAY. SHOULD SEE MAINLY DRY
WEATHER THIS EVENING AND OVERNIGHT. THERE WILL BE A CHANCE FOR
SHOWERS AND STORMS FRIDAY...THE BEST CHANCE IN THE LATE MORNING AND
AFTERNOON WEST OF A FOND DU LAC TO JANESVILLE LINE.

&&

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

$$
MBK