Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 010153
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
853 PM CDT TUE SEP 30 2014

.UPDATE...
PESKY LOW CLOUDS TRAPPED UNDER THE LOW LEVEL INVERSION WILL CONTINUE
TO BE A PROBLEM FOR THE OVERNIGHT HOURS. THEY/VE CLEARED OUT OF
PORTIONS OF SOUTH CENTRAL WI...BUT REMAIN LOCKED IN OVER THE
SOUTHEAST. GUIDANCE SUGGEST IT WILL EXPAND BACK TO THE WEST...OVER
THE AREAS THAT CLEARED...LATER ON TONIGHT. NOT ENTIRELY CONVINCED
OF THAT THOUGH. THEN ALL THE CLOUDS WILL SCOUR OUT WEDNESDAY
MORNING AS THE SFC WINDS INCREASE OUT OF THE SOUTHEAST TO SOUTH.

THE OTHER PROBLEM TONIGHT HAS BEEN AN UNEXPECTED ROUND OF DRIZZLE
ACROSS THE SOUTHEAST. IT APPEARS A COMBINATION OF SPEED/MECHANICAL
CONVERGENCE OF THE LOW LEVEL WINDS...ALONG WITH STEEP LAPSE RATES
/WEAK CAPE/ WITHIN THE CLOUD LAYER HAS HELPED TO PRODUCE SOME
DRIZZLE. H8 ANALYSIS ALSO SHOWS A WEAK BUT SHARP TROF AXIS
DROPPING THROUGH THE SHORELINE AREAS EARLY THIS EVENING. VSBY AT
KMKE ACTUALLY WENT DOWN TO 2 1/2 MILES BRIEFLY...AND THEY
MEASURED WITH /.01/. THE PRECIP SHOWED UP NICELY ON THE TERMINAL
DOPPLER RADAR AND MUCH LESS OBVIOUSLY ON OUR LARGER WAVELENGTH
DOPPLER. TRENDS BOTH IN THE SHORT RANGE SOUNDINGS AND RADAR
SUGGEST THIS SHOULD END BY MIDNIGHT.

TEMPS ARE IN THE BALLPARK SO LITTLE CHANGE NEEDED THERE.

&&

.AVIATION/06Z TAFS/...

MOISTURE TRAPPED UNDER A LOW LEVEL INVERSION WILL LIKELY KEEP MVFR
CIGS IN KMKE/KUES/KENW THROUGH WEDNESDAY MORNING. KMSN SCATTERED
OUT THE MVFR CLOUDS BY MID EVENING...BUT THERE IS CONCERN THEY
WILL SPREAD BACK IN DURING THE OVERNIGHT HOURS. SO...UNCERTAINTY
IS MUCH GREATER AT KMSN. ALL THE LOWER CLOUDS WILL LIFT NORTH BY
MID DAY ON WEDNESDAY...LEAVING VFR CONDITIONS FOR THE REMAINDER
OF THE TAF PERIOD. A BAND OF SHOWERS WILL LIKELY SPREAD INTO SOUTH
CENTRAL AREAS DURING WEDNESDAY EVENING...AHEAD OF AN APPROACHING
TROF OF LOW PRESSURE.

&&

.PREV DISCUSSION... /ISSUED 248 PM CDT TUE SEP 30 2014/

TONIGHT AND WEDNESDAY...CONFIDENCE - HIGH.

BIGGEST FORECAST ISSUE TONIGHT IS CLOUD COVER. MODELS ARE
SPLIT...WITH SOME CLEARING THINGS OUT ACROSS THE WESTERN TWO-
THIRDS...WHILE OTHERS REMAIN MOSTLY CLOUDY. HAVE TRENDED TOWARD THE
CLOUDIER SOLUTIONS BASED ON HOW SLOW CLOUDS HAVE ERODED TODAY...AND
MORE DEVELOPMENT POSSIBLE TONIGHT VIA THETA-E ADVECTION. WENT A
DEGREE OR TWO MILDER FOR LOWS DUE TO INCREASED SKY COVER IN THE
FORECAST.

IT WILL LIKELY REMAIN DRY THROUGH WEDNESDAY MORNING...WITH A CHANCE
FOR SHOWERS IN THE WEST DURING THE AFTERNOON UNDER WARM ADVECTION
ALOFT AHEAD OF AN APPROACHING SHORTWAVE. DID NOT CHANGE HIGH TEMPS
MUCH FOR TOMORROW...WITH HIGHS EXPECTED TO BE NEAR NORMAL VALUES
AWAY FROM LAKE MICHIGAN. SOUTHEAST WINDS WILL KEEP IT COOLER NEAR
THE LAKE.

WEDNESDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE - MEDIUM.

SHORT TERM GUIDANCE GRADUALLY SETTLING ON SLOWER MOVING AND HIGHER
AMPLITUDE LONG WAVE TROF DEVELOPING OVER THE UPPER MIDWEST AND
NORTHERN PLAINS AND SPREADING EWD INTO THE WESTERN GTLAKES BY THE
END OF THE PERIOD.  SECONDARY SURGE OF THETA-E ADVECTION LATER
WEDNESDAY NIGHT TIED TO PIVOTING LOW LEVEL JET INTO SRN WI ARE
EXPECTED TO RESULT IN ENOUGH LIFT AND MOISTURE TO GENERATE NUMEROUS
-SHRA.  WEAKENING RIGHT ENTRANCE REGION OF UPPER JET WILL ADD
ENHANCED SYNOPTIC LIFT AT THE TIME AS WELL.  WL CONTINUE TO TREND
POPS TO LIKELY WORDING WED NIGHT.  ELEVATED INSTABILITY WEAK BUT
MUCAPES APPROACHING 500 J NEAR THE IL BORDER SO WL CONTINUE T
CHANCE.

MAY BE BREAK IN PRECIP THU MRNG DUE TO WEAK SHORT WAVE RIDGING
BETWEEN EXITING LIFT TO THE NORTHEAST AND REDEVELOPING ENHANCED LIFT
TO THE SOUTHWEST.  THIS SECONDARY LIFT WL BE DUE TO UPSTREAM
CYCLOGENESIS ALONG BAROCLINIC ZONE DRAPED ACROSS IA/MN ON THU.
REAMPLIFICATION OF LOW LEVEL JET AHEAD OF THIS AMPLIFYING WAVE WL
RESULT IN ANOTHER PERIOD OF FAVORABLE CONVERGENCE SPREADING INTO WI
LATER THU.  BULK SHEAR OF 35 TO 45 KNOTS THU AFTN AND EVE BUT
QUESTION OF HOW UNSTABLE AIR MASS WILL BECOME.  AT THIS POINT
THINKING WIDESPREAD CLOUD COVER SHOULD RESTRICT INSTABILTY BUT
ENOUGH SYNOPTIC SCALE FORCING TO RESULT IN SCT TO NMRS STORMS
EMBEDDED IN SHRA ACTIVITY.

COOLER AIR BEHIND SFC FRONT WL SETTLE IN LATER THU NIGHT WITH
REINFORCING PUSH OF COLD AIR ON FRI.  VIGOROUS SHORT WAVE TROUGH
MOVES ACROSS REGION ON FRIDAY WITH STRONG 400MB POTENTIAL VORTICITY.
MID-LEVEL LAPSE RATES INCREASE TO 7.5 DEGREES WHICH WILL RESULT IN
ENHANCED LIFT. WL BUMP UP POPS BUT KEEP IN CHANCE CATEGORY AT THIS
POINT.  NOT IMPOSSIBLE THERE COULD BE SMALL HAIL FROM ANY SHOWERS ON
FRIDAY DUE TO LOW FREEZING LEVEL AND VIGOROUS LIFT.

FRIDAY NIGHT THROUGH TUESDAY...FORECAST CONFIDENCE - MEDIUM.

MEDIUM RANGE GUIDANCE COMING INTO BETTER AGREEMENT ON SLOWER MOVING
AND HIGHER AMPLITUDE LONG WAVE TROUGH LINGERING OVER WESTERN AND
CENTRAL GTLAKES EARLY IN THE PERIOD.  DURING THIS TIME...
UNSEASONABLE COLD AIR WILL SETTLE OVER SOUTHERN WI ON BRISK
NORTHWEST WINDS THROUGH A DEEP COLUMN.  85H TEMPS FALL TO BETWEEN 0
AND -5C BY SAT...WITH THE COLD TEMPS LINGERING INTO EARLY NEXT WEEK.
925H TEMPS FALL TO 0 TO 5C OVER THE WEEKEND WITH MINOR WARMING MON
AND TUE.  HENCE BELOW NORMAL TEMPS LIKELY THIS PERIOD.  TIMING ONCE
AGAIN DIFFICULT ON WEAK SHORT WAVES ROTATING AROUND DEEP UPPER LOW
EXTENDING FROM HUDSON BAY SOUTH TO THE GTLAKES.  THEREFORE WL
CONTINUE SMALL POPS GOING FRI NGT WITH ANOTHER THREAT FOR LIGHT
PRECIP SUN NGT INTO MON.  GFS OUTLIER ON COLD THERMAL PROFILE AND
CRITICAL THICKNESSES FRI NGT AND AGAIN SUN NGT HINTING AT POTENTIAL
MIX OF LIGHT PRECIP.

HOWEVER GEM AND ECMWF NOT QUITE AS COLD IN LOW LEVELS.  FOR NOW...WL
CONTINUE LIQUID PRECIP FOR THESE PERIODS.  STEERING FLOW TO REMAIN
NORTHWEST THROUGH THE END OF THE PERIOD RESULTING IN WELL BELOW
NORMAL TEMPS.  CPC 8-14 DAY 500H VALID OCT7-13 HAS GRADUALLY WEAKING
BROADSCALE TROF OVER NORTHERN TIER OF CONUS AND CAN WITH BELOW
NORMAL HEIGHTS OVER GTLAKES.  ONLY A MATTER OF TIME WHEN LIGHT WINDS
AND CLEARING WL RESULT IN FROST FORMATION AND NIGHT TIME FREEZING
TEMPS.

AVIATION/00Z TAFS/...

THERE ARE A LOT OF HOLES IN THE CLOUDS ACROSS THE REGION THIS
AFTERNOON...BUT CLOUDS REMAIN PRETTY WIDESPREAD OVER MOST OF THE
FORECAST AREA. SATELLITE TRENDS SUGGEST SOME CLEARING IN AT LEAST
THE SOUTHWEST HALF OF THE FORECAST AREA LATER THIS AFTERNOON INTO
THE EVENING...THOUGH SOME AREAS MIGHT HANG ON TO MVFR CONDITIONS
INTO WEDNESDAY. WILL CONTINUE TO MONITOR SATELLITE AND ADJUST TAFS
PER TRENDS.

DRY WEATHER IS EXPECTED TONIGHT THROUGH WEDNESDAY MORNING...WITH A
CHANCE OF SHOWERS WEST IN THE AFTERNOON.

MARINE...

LET THE SMALL CRAFT ADVISORY EXPIRE EARLY THIS AFTERNOON...AS WINDS
CONTINUE TO EASE. WAVES ARE LIKELY GENERALLY FOUR FEET OR LESS...AND
WILL CONTINUE TO SUBSIDE THIS AFTERNOON INTO THE EVENING.

SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY AGAIN FRIDAY AS WESTERLY
WINDS PICK UP BEHIND DEPARTING LOW PRESSURE.

&&

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

$$

UPDATE...DAVIS
TONIGHT/WEDNESDAY AND AVIATION/MARINE...DDV
WEDNESDAY NIGHT THROUGH TUESDAY...MBK


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