Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 160145
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
845 PM CDT FRI MAY 15 2015

.UPDATE...

A MID LEVEL SHORT WAVE OVER IOWA WILL LIFT NORTHEAST ACROSS
WISCONSIN OVERNIGHT...BUT THE OVERALL FLOW IS VERY WEAK...LACKING
ANY MEANINGFUL FORCING TO SUPPORT ANYTHING OTHER THAN SOME
REMNANT SHOWERS FROM CONVECTION UPSTREAM EARLIER IN THE DAY. THE
LAKE BREEZE HAS PUSHED INLAND BY A FEW MILES AND THIS IS SETTING
THE STAGE FOR SOME LOW CLOUDS AND FOG TO LIKELY SPREAD INLAND
OVERNIGHT AS THE HIGH DEWPOINT AIR SATURATES OVER THE COLD LAKE
MICHIGAN WATERS. WE MAY END UP NEEDING A DENSE FOG ADVISORY FOR
SOME LAKE COUNTIES...ESPECIALLY NORTH OF MILWAUKEE...SO WILL BE
KEEPING AN EYE ON THAT.

OTHERWISE FAIRLY QUIET OVERNIGHT.

&&

.AVIATION/06Z TAFS/...

A SATURATING COLD MARINE LAYER COULD BRING SOME MVFR/IFR CIGS
VSBYS TO THE LAKE SHORE AREAS...INCLUDING THE KMKE/KENW/KUES TAF
SITES OVERNIGHT. THERE IS PLENTY OF UNCERTAINTY ABOUT HOW LOW
CONDITIONS MAY GO. BUT..WITH THE HIGH DEWPOINT AIR COMBINING WITH
THE COLD LAKE MICHIGAN AIRMASS PUSHING INLAND ON A VERY LIGHT
EASTERLY BREEZE...IT WOULD SUGGEST A GOOD PROBABILITY OF LOW
CONDITIONS FORMING AFTER 06Z SATURDAY. THIS COULD PERSIST THROUGH
ABOUT 14-15Z SATURDAY BEFORE DEEPER MIXING CLEARS THINGS UP.

IT LOOKS LIKE ANY PRECIP BEFORE SUNRISE SATURDAY MAY JUST BE
SHOWERS AND NOT THUNDERSTORMS. THUNDERSTORMS CHCS WILL LIKELY HAVE
TO WAIT UNTIL SATURDAY AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 358 PM CDT FRI MAY 15 2015/

SHORT TERM...

TONIGHT AND SATURDAY... FORECAST CONFIDENCE MEDIUM.

THERE ARE FINALLY SOME BREAKS DEVELOPING IN THE CLOUDS THIS
AFTERNOON AS DRIER AIR ALOFT SPREADS INTO THE AREA IN THE WAKE OF A
LOW PRESSURE TROUGH. EXPECT THE LOW CLOUDS TO SCATTER OUT TOWARD
SUNSET. THEN HIGH CLOUDS WILL STREAM INTO SOUTHERN WI OVERNIGHT AS A
500MB SHORTWAVE APPROACHES. A FEW MESOSCALE MODELS SPREAD SHOWERS
INTO FAR SOUTHERN WI BEFORE MIDNIGHT DUE TO THE REMNANTS OF THE
UPSTREAM CONVECTION OVER NORTHERN MO AND SOUTHERN IL. THE MAJORITY
OF MODELS KEEP THE AREA DRY... SO I HELD OFF THE POPS UNTIL AFTER
MIDNIGHT.

THERE WILL BE ANOTHER SHORTWAVE TRACKING THROUGH CENTRAL AND
NORTHEAST ILLINOIS DURING THE DAY SATURDAY. VORTICITY ADVECTION FROM
THIS SHORTWAVE WILL COMBINE WITH WEAK 850MB FRONTAL TROUGH SLIDING
THROUGH SOUTHERN WI TO PRODUCE DECENT MOISTURE CONVERGENCE AND SOME
UPWARD MOTION. ANY STORMS THAT DEVELOP WILL BE SLOW-MOVING. WITH
PRECIPITABLE WATER VALUES OVER 1.5 INCHES AND TALL-SKINNY CAPE OF
AROUND 1000 J/KG WITH WEAK SHEAR... STORMS WILL BE HEAVY-RAIN
PRODUCERS.

THE TIMING AND COVERAGE OF THE SHOWERS AND THUNDERSTORMS ON SATURDAY
IS THE UNCERTAINTY.

EXPECTING PLENTY OF CLOUDS OVER THE REGION... BUT ANY BREAKS WILL
ALLOW TEMPERATURES TO RISE TO AROUND 80 BY SAT AFTERNOON GIVEN THE
WARM AIR MASS.

SATURDAY NIGHT THROUGH MONDAY...FORECAST CONFIDENCE MEDIUM.

THE WEAK SHORTWAVE TROUGH THAT WILL AFFECT THE AREA ON SAT WILL
HAVE MOVED TO THE EAST BY SAT EVE WHILE THE 850 MB WARM FRONT
WILL HAVE MOSTLY LIFTED INTO CENTRAL WI. THUS ONLY WENT WITH LOW
POPS FOR SHOWERS/TSTORMS SAT NT. A WEAK BUT MOIST SELY FLOW WILL
ALSO SUPPORT AREAS OF FOG ESPECIALLY IN AREAS THAT GET RAIN ON
SAT.

FOR SUN...THE OCCLUDED LOW WILL MOVE TO THE BORDER OF MN AND THE
DAKOTAS WHILE A TRAILING UPPER TROUGH AXIS AND PREFRONTAL SFC
TROUGH WILL SWING NEWD THROUGH SRN WI LATE SUN AFT AND EVE. AHEAD
OF THESE FEATURE WILL BE THE WARM CONVEYOR BELT WITH A BAND OF
SHOWERS AND TSTORMS FROM THE LATE MORNING IN THE WRN CWA SPREADING
EWD FOR THE AFTERNOON. THE DEEP LAYER SHEAR AND LOW LEVEL WIND
SHEAR WILL INCREASE THROUGHOUT THE AFTERNOON PEAKING BY LATE
AFTERNOON AND EARLY EVENING...WITH VALUES OF 40-50 KTS AND 20-25
KTS RESPECTIVELY. DESPITE CLOUDS AND PCPN THE TEMPS ALOFT ARE COLD
ENOUGH TO STILL SUPPORT MLCAPE REACHING AT LEAST 1000
J/KG...ALTHOUGH WILL PROBABLY BE HELPED BY SOME BREAKS IN THE
CLOUD COVER AT TIMES. OVERALL...BELIEVE THE CONVECTION WITH THE
WARM CONVEYOR BELT DOES HAVE SOME POTENTIAL TO BECOME SEVERE BUT
THE BIGGER CONCERN IS THE NEW DEVELOPMENT WITH THE PASSAGE OF THE
UPPER TROUGH AXIS AND SFC TROUGH. THE NAM SHOWS SCT DEEP
CONVECTION WITH THE LATEST ECMWF HINTING AT THE NEW DEVELOPMENT AS
WELL. THIS NEW DEVELOPMENT COULD INCLUDE SUPERCELLS WITH A TORNADO
THREAT PRESENT.

THE COOL FROPA WILL THEN ARRIVE EARLY MON AM WITH COLD ADVECTION
THROUGHOUT THE DAY BUT DRY ENOUGH FOR PARTLY CLOUDY SKIES. BREEZY
AND MILD CONDITIONS ARE EXPECTED.

LONG TERM...

TUESDAY THROUGH FRIDAY...FORECAST CONFIDENCE MEDIUM.

POLAR HIGH PRESSURE AND WNWLY FLOW ALOFT WILL THEN PREVAIL THE
REMAINDER OF THE WEEK. BELOW NORMAL TEMPS ARE EXPECTED BUT WILL
REBOUND BY THE END OF THE WEEK. NO PCPN IS FORECAST.

AVIATION/00Z TAFS/...

BROKEN MVFR/VFR CIGS WILL FINALLY SCATTER OUT EARLY THIS EVENING.
LOOK FOR HIGH CLOUDS TO SPREAD INTO SOUTHERN WI TONIGHT. SHOWER AND
THUNDERSTORM CHANCES INCREASE AFTER MIDNIGHT... BUT ESPECIALLY
DURING THE DAY SATURDAY. THUNDERSTORMS WILL LIKELY BE SCATTERED IN
NATURE... BUT SLOW MOVING AND HEAVY RAIN PRODUCERS.

MARINE...

LIGHT EASTERLY WINDS WILL PERSIST NORTH OF PORT WASHINGTON FROM
TONIGHT THROUGH SATURDAY NIGHT AND LIKELY INTO SUNDAY MORNING UNTIL
WINDS BECOME STRONGER OUT OF THE SOUTH MIDDAY SUNDAY. A MARINE DENSE
FOG ADVISORY IS IN EFFECT.

THERE IS A CHANCE THAT THE MARINE FOG COULD EXPAND SOUTHWARD TONIGHT.


&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...DENSE FOG ADVISORY UNTIL 10 AM CDT SUNDAY FOR LMZ643.

&&

$$

UPDATE...DAVIS
TONIGHT/SATURDAY AND AVIATION/MARINE...MRC
SATURDAY NIGHT THROUGH FRIDAY...GEHRING


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