Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 192026
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
326 PM CDT FRI SEP 19 2014

.TONIGHT AND SATURDAY...FORECAST CONFIDENCE IS MEDIUM.

AN UPPER LEVEL TROUGH WILL MOVE ACROSS MINNESOTA TONIGHT AND INTO
WISCONSIN SATURDAY MORNING...BEFORE REACHING LAKE MICHIGAN EARLY
SATURDAY EVENING. A 70 KNOT 250 MB JET EXTENDS ACROSS NORTHERN AND
CENTRAL WISCONSIN...WITH AN INCREASING SPEED MAX BEHIND THE TROUGH.
THE UPPER DIVERGENCE IS MAINLY WEAK...BUT DOES INCREASE SOME TOWARDS
MIDNIGHT...AND AGAIN IN THE FAR SOUTHEAST LATE SATURDAY EVENING. THE
850/700 MB WARM AIR ADVECTION CONTINUES TONIGHT WITH THE THERMAL
RIDGE PUSHING SOUTH AND EAST SATURDAY AFTERNOON. THE 700 MB UPWARD
MOTION IS ON THE WEAK SIDE.

700 MB RELATIVE HUMIDITY SATURATES BY NOON SATURDAY...MAINLY OVER
THE SOUTHEAST. THE 850 MB WINDS INCREASE THIS EVENING...BUT BY
MIDNIGHT THE JET MAX IS OVER EAST CENTRAL WISCONSIN AND MOVES OFF TO
THE EAST.  THEREFORE THERE IS LITTLE CONVERGENCE FOR THUNDERSTORM
DEVELOPMENT.  700 MB WINDS ARE SIMILAR...EXCEPT THEY REMAIN STRONG
ACROSS CENTRAL WISCONSIN AFTER MIDNIGHT WITH ONLY WEAK CONVERGENCE.

THE HIRES ARW AND NMN BRINGS SCATTERED SHOWERS ACROSS THE FORECAST
AREA LATE TONIGHT AND IS MAINLY DRY DURING THE DAY SATURDAY.  THE
NAM BRINGS MOST PRECIPITATION IN SATURDAY MORNING THEN SOUTHEAST
SATURDAY AFTERNOON.  AS A RESULT CONFIDENCE IS NOT HIGH WITH
PRECIPITATION TIMING AND EXTENT.  GIVEN LACK OF A STRONG LIFTING
MECHANISM...WITH HAVE MAINLY LOW TO MEDIUM CHANCES.  THE LOW LEVEL
CAP REMAINS AND WOULD LIMIT THE SEVERE WEATHER POTENTIAL. SHEAR IS
STRONG...BUT UNCERTAINTY OF THUNDERSTORM DEVELOPMENT REMAINS.

.SHORT TERM...SATURDAY NIGHT THROUGH MONDAY

SATURDAY NIGHT...FORECAST CONFIDENCE MEDIUM

FIRST SHORT WAVE EXITING TO THE EAST BY 00Z SATURDAY...WITH
SECOND...STRONGER WAVE DROPPING INTO NW WISCONSIN IN LEFT EXIT
REGION OF A 125 KT JET MAX THAT SAGS TO NEAR THE WI/IL BORDER BY
12Z SUNDAY THAT DEEPENS THE 500 MB TROUGH OVER THE WESTERN GREAT
LAKES.

SURFACE TROUGH TRAILING FROM LOW IN SW QUEBEC DOES NOT PUSH SE OF
REGION UNTIL 06Z...WITH LOW-LEVEL FRONTOGENESIS STRENGTHENING AS IT
MOVES ACROSS SRN WI.

WHILE MODELS FOCUS AXIS OF HIGHEST ML CAPE ACROSS IL/SRN LK MI INTO
LOWER MI...THE NAM IS SHOWING A ML CAPE GRADIENT OF 1000-1500 J/KG
ACROSS FAR SRN WI...ALONG AND SE OF A PORT WASHINGTON TO DUBUQUE
IOWA LINE...THAT SAGS TO THE SOUTHEAST BETWEEN 00Z AND 03Z EXITING
THE FAR SE BY 06Z. HOWEVER THE SURFACE DEW POINTS USED ON THE NAM
FORECAST SOUNDINGS ARE HIGHER THAN THE 2M DEW POINTS OR THOSE IN THE
MET GUIDANCE...SO HIGHER CAPE VALUES ARE SUSPECT. BOTH NAM AND GFS
HAVE 40KTS OF EFFECTIVE SHEAR DURING THIS TIME OVER SRN WI THAT
SHIFTS SE.

WILL KEEPING WITH A FASTER FRONTAL PASSAGE THAT MATCHES POP TREND
FROM THE SATURDAY DAY PERIOD...WITH ONLY SLIGHT CHANCES IN THE SE
AND EAST BETWEEN 00Z AND 03Z WITH DEPARTING FRONT AND INCREASING
CHANCE POPS FROM WEST TO EAST WITH SECOND STRONG WAVE. MODERATE MID-
LEVEL LAPSE RATES AND CAPPING AROUND 15K FT WILL LIMIT
INSTABILITY... SO WILL GO WITH CHANCE SHOWERS/SLIGHT CHANCE
THUNDERSTORMS.

SUNDAY AND MONDAY...FORECAST CONFIDENCE MEDIUM

MODELS DIFFER WITH DEGREE OF SECONDARY DEVELOPMENT ALONG SURFACE
TROUGH ASSOCIATED WITH DEPARTING SHORT WAVE. THIS AFFECTS QPF AMOUNTS
AND COVERAGE FOR SUNDAY. WILL USE A BLENDED SOLUTION THAT KEEPS A
SLIGHT CHANCE IN THE NORTHEAST CWA SUNDAY MORNING...WITH THE
ENTIRE CWA DRY SUNDAY AFTERNOON.

OTHERWISE...QUIET WEATHER FOR THE REST OF SUNDAY THROUGH MONDAY
NIGHT WITH NORTHWEST FLOW AND A BROAD AREA OF HIGH PRESSURE MOVING
ACROSS REGION. CORE OF 850 MB AND 925 MB COLD POOLS PASS WELL NORTH
AND EAST OF STATE...SO NOT A HUGE COOL DOWN WITH HIGHS IN THE MID-
UPPER 60S SUNDAY AND THE BEGINNING OF WEAK WARM AIR ADVECTION
BRINGING HIGHS UP A FEW DEGREES FOR MONDAY. PATCHY TO AREAS OF FOG
SUNDAY NIGHT WITH LIGHT WINDS AND CLEAR SKIES ALLOWING RADIATIONAL
COOLING DOWN TO NEAR DEW POINTS.

.LONG TERM...TUESDAY THROUGH FRIDAY. FORECAST CONFIDENCE MEDIUM

THE STRENGTHENING HIGH WILL DOMINATE THE WEATHER FOR MOST OF NEXT
WEEK AS IT SLOWLY DRIFTS EAST. SOUTHERLY FLOW BRINGS NEAR NORMAL TO
ABOVE NORMAL TEMPS TO THE FORECAST AREA...WITH COOLER READINGS IN
THE EAST DUE TO MORE OF A SOUTHEAST FLOW THERE...BUT STILL NEAR
SEASONAL NORMALS. GFS AND ECMWF BRUSH NORTHWEST CWA WITH PCPN
WEDNESDAY NIGHT INTO THURSDAY AS A CENTRAL PLAINS TROUGH SHEARS OUT
AS IT LIFTS NORTHEAST INTO THE BROAD RIDGE COVERING MOST OF THE
EASTER U.S. WILL GO WITH THE BLENDED LOW CHANCE/SLIGHT CHANCE POPS
FOR WED NIGHT AND KEEP THURSDAY DRY. DRY TREND CONTINUES THROUGH
FRIDAY...WITH ABOVE NORMAL TEMPS IN PERSISTENT SOUTHERLY FLOW ON
WESTERN FLANK OF EASTERN HIGH.

&&

.AVIATION/00Z TAFS/...

VFR CONDITIONS THROUGH EARLY TONIGHT WITH A SLOW INCREASE IN
MID/HIGH CLOUDS.  A STRONG LOW LEVEL CAP HAS KEPT WIND GUSTS DOWN.
HOWEVER THIS WILL ALSO BRING SOME LOW LEVEL WIND SHEAR POTENTIAL AS
SOUTHWEST WINDS INCREASE AT 2 THSD FT.

THERE IS A CHANCE OF SHOWERS WITH ISOLATED THUNDERSTORMS AFTER
MIDNIGHT AS A WEAK COLD FRONT APPROACHES. EXPECT SOME MVFR
CIGS/VSBYS AROUND OR AFTER SUNRISE DUE TO THE INCREASING MOISTURE
AHEAD OF THE FRONT. THERE COULD ALSO BE A BRIEF PERIOD OF IFR CIGS
MAINLY WEST OF MADISON.  THE CHANCE FOR THUNDERSTORMS WILL CONTINUE
THROUGH SATURDAY AS THE WEAK FRONT MOVES ACROSS SOUTHERN WISCONSIN.

&&

.MARINE...

SOUTH WINDS WILL REACH SMALL CRAFT ADVISORY LEVELS THROUGH MID
AFTERNOON ON SATURDAY...BUT A LOW LEVEL INVERSION IS REDUCING THE
STRONG WIND POTENTIAL. WAVES WILL BE ON THE INCREASE INTO TONIGHT.

WINDS WILL SHIFT TO THE WEST IN THE WAKE OF A WEAK PASSING COLD
FRONT SATURDAY AFTERNOON...THUS WIND/WAVE CONDITIONS WILL BE
IMPROVING BY THEN.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 PM CDT SATURDAY FOR LMZ643>646.

&&

$$

TONIGHT/SATURDAY AND AVIATION/MARINE...HENTZ
SATURDAY NIGHT THROUGH FRIDAY...REM


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