Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 170154
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
854 PM CDT SAT MAY 16 2015

.UPDATE...PULLED TRIGGER ON DENSE FOG ADVY FOR MILWAUKEE...OZAUKEE
AND SHEBOYGAN COUNTIES. VISIBILITIES CRASHED EARLY THIS EVENING AS
DIURNAL MIXING ABATED AND SFC WINDS TURNED A BIT MORE NORTHEAST
PULLING DENSE FOG OVER LAKE INLAND. VISIBILITIES BOUNCING LAST
HOUR OR SO...BUT EXPECT AREAS OF DENSE FOG TO PERSIST ACROSS THE
LAKE SHORE COUNTIES FOR MUCH OF THE NIGHT. VISIBILITIES MAY
INCREASE LATER TONIGHT AS BOUNDARY LAYER WINDS BECOME MORE
SOUTHEAST AND INCREASE SLIGHTLY. MAY NEED TO EXPAND ADVY INTO
RACINE AND KENOSHA COUNTIES.

ISOLATED SHOWERS AND STORMS HAVE ENDED WITH LOSS OF DAYTIME
HEATING AND WEAK MID-LEVEL WAVE PASSING THRU. WL CONTINUE SMALL
CHANCE SPREADING IN FROM THE WEST LATER TONIGHT AHEAD OF
INCREASING LOW LEVEL MOISTURE CONVERGENCE AND LOW LEVEL JET.
BETTER CHANCE SUNDAY MORNING WITH STRONG TO SEVERE STORMS STILL
LIKELY IN THE AFTN AND EVE.

&&

.AVIATION/06Z TAFS/...BOUNDARY LAYER MIXING AND LOW LEVEL MOISTURE
CONVERGENCE SHOULD RESULT IN STRATUS DEVELOPING OVERNIGHT INTO
SUNDAY MORNING. FOG WILL CONTINUE TO CAUSE IFR OR LOWER VSBYS AT
KMKE...POSSIBLY AFFECTING KENW AND KUES. WL MAINTAIN BEST CHANCE
FOR T IN THE MID AFTN INTO THE EVE ON SUNDAY.

&&

.MARINE...DENSE FOG ADVY WILL CONTINUE INTO SUNDAY MORNING. LIGHT
SFC WINDS AND WARM...HUMID AIR OVER THE COLD LAKE MICHIGAN WATERS
WILL CONTINUE TO CAUSE DENSE FOG. LOW LEVEL WINDS WILL VEER TO THE
SOUTH TO SOUTHEAST LATER TONIGHT AND SUNDAY MORNING AND INCREASE
WHICH SHOULD HELP THIN THE FOG.

&&

.PREV DISCUSSION... /ISSUED 412 PM CDT SAT MAY 16 2015/

SHORT TERM...

TONIGHT THROUGH SUNDAY AFTERNOON...FORECAST CONFIDENCE MEDIUM.

WIDELY SCATTERED THUNDERSTORMS PERSIST THROUGH LATE AFTERNOON. THESE
ARE BEING TRIGGERED BY A WEAK MID LEVEL SHORTWAVE APPROACHING FROM
IA/IL. MODEL SOUNDINGS AND RAP SPC MESOSCALE ANALYSIS ARE SHOWING
TALL SKINNY CAPE VALUES OF 1000 TO 2000 J/KG INLAND FROM THE
LAKESHORE THIS AFTERNOON. THERE IS NOT MUCH SHEAR... SO ONLY BRIEF
SMALL HAIL WOULD BE POSSIBLE IN ANY STRONGER STORMS. THE MAIN THREAT
WILL BE BRIEF HEAVY RAIN SINCE PRECIPITABLE WATER VALUES ARE AROUND
1.3 INCHES TODAY.

THESE THUNDERSTORMS WILL DIMINISH AFTER SUNSET THIS EVENING. LIGHT
WINDS AND SMALL DEWPOINT DEPRESSIONS WILL LEAD TO PATCHY FOG AND LOW
CLOUDS ACROSS SOUTHERN WI OVERNIGHT. THERE IS A CHANCE THAT MARINE
FOG WILL SPREAD INLAND ONCE AGAIN. THE CLOUDS WILL LIKELY LINGER
INTO THE MID SUNDAY MORNING HOURS.

SURFACE LOW PRESSURE OVER THE DAKOTAS WILL TRACK INTO MINNESOTA
TONIGHT AND STALL THROUGH SUNDAY AS IT OCCLUDES. THE 850 MB WARM
CONVEYOR BELT... OR WARM MOIST AIR TRANSPORT... WILL LIFT THROUGH
SOUTHERN WI SUNDAY MORNING INTO THE EARLY AFTERNOON. THIS WILL BRING
A BAND OF NUMEROUS SHOWERS AND THUNDERSTORMS THAT SHOULD MARCH
NORTHEAST ACROSS SOUTH CENTRAL AND SOUTHEAST WI. THERE IS SOME
CONCERN THAT AN EMBEDDED THUNDERSTORM COULD BECOME SEVERE DURING THE
AFTERNOON AS THE ATMOSPHERE BECOMES LESS STABLE. MODELS ARE HINTING
AT SOUTHEAST WI AND LAKE MICHIGAN HAVING THE GREATEST THREAT FOR
ENHANCED THUNDERSTORMS ON THE BACK EDGE OF THIS FIRST ROUND.

TEMPERATURES WILL RISE INTO THE UPPER 70S... SIMILAR TO TODAY.
LAKESHORE TEMPS WILL BE A LITTLE COOLER THAN INLAND GIVEN A SLIGHT
EASTERLY COMPONENT. WINDS WILL BE STRONG OUT OF THE SOUTH DUE TO A
TIGHT PRESSURE GRADIENT WITH THE APPROACHING SURFACE LOW.

LATE SUNDAY AFTERNOON THROUGH TUESDAY...FORECAST CONFIDENCE
MEDIUM.

THE OCCLUDED LOW OVER NW MN WILL WEAKEN TO A BROAD W-E SFC TROUGH
STARTING LATE SUNDAY NIGHT AND THROUGH MONDAY AS IT MOVES ACROSS
LAKE SUPERIOR AND INTO CANADA. BEFORE IT WEAKENS...THE PASSAGE OF
A TRAILING UPPER TROUGH AXIS AND A PREFRONTAL SFC TROUGH WILL
LIKELY INITIATE A NEW ROUND OF SCATTERED CONVECTION LATE SUNDAY
AFTERNOON AND THROUGH THE EVENING. THE NAM AND SOME MESOMODELS
ARE SHOWING WHAT WILL LIKELY BE DISCRETE SUPERCELLS DEVELOPING
FROM THE MS RIVER EWD. A 60-65 KT 500 MB JET STREAK WILL
ACCOMPANY THE UPPER WAVE...SUPPORTING 0-6 KM BULK SHEAR OF 50
KTS AND A SUPERCELL POTENTIAL WITH MLCAPE VALUES UP TO 1500 J/KG
OVER SOUTH CENTRAL WI. A TORNADO RISK WILL BE PRESENT DUE TO
0-1 KM SRH OF 150-200 M2/S2 AND 0-1 KM BULK SHEAR RISING TO 25
KTS. LCL HEIGHTS WILL ALSO BE AT OR BELOW 1 KM WITH THE LFC ONLY
SLIGHTLY HIGHER. SPC HAS UPGRADED TO AN ENHANCED RISK OF SEVERE
TSTORMS OVER MUCH OF WESTERN AND CENTRAL WI...MENTIONING THE
POSSIBILITY  OF STRONG TORNADOES. CAPE VALUES WILL REMAIN BELOW
1000 J/KG OVER ERN WI AND THE STORMS MAY NOT ARRIVE UNTIL THE
MIDDLE TO LATE EVENING...THUS THE SLIGHT RISK THERE. HOWEVER SHEAR
VALUES DO BECOME STRONG AS WELL.

THE ACTUAL COLD FRONT WILL GRADUAL MOVE ACROSS SRN WI ON
MONDAY...THUS 70 DEGREE HIGHS ARE EXPECTED. NWLY FLOW AND COLD
ADVECTION WILL THEN PREVAIL FOR MONDAY NIGHT AND TUESDAY. SRN WI
APPEARS TO BE FAR ENOUGH SOUTH TO AVOID THE BROKEN STRATUS ON
MONDAY BUT SOME STRATUS WILL BE POSSIBLE MONDAY NIGHT INTO
TUESDAY. A CANADIAN AIRMASS AND LINGERING CLOUDS INTO TUE
AFTERNOON WILL KEEP HIGH TEMPS ONLY IN THE 50S.

LONG TERM...

TUESDAY NIGHT THROUGH SATURDAY...FORECAST CONFIDENCE MEDIUM.

A LARGE SFC HIGH WILL EXTEND FROM THE GREAT PLAINS TOWARD THE OHIO
RIVER VALLEY FOR THIS PERIOD. A RELATIVELY WEAK WNWLY FLOW ALOFT
WILL PREVAIL WITH BELOW NORMAL TEMPS EXPECTED IN THE BEGINNING OF
THE PERIOD BUT QUICKLY REBOUND TO SEASONAL NORMALS. NO PCPN IS
EXPECTED.

AVIATION/00Z TAFS/...

DENSE MARINE FOG MAY SPREAD INLAND TO KMKE AND KRAC LATE THIS
AFTERNOON. WILL NOT ADD INTO THE MKE TAF YET... BUT BE AWARE FOR THE
POTENTIAL. DENSE FOG WILL BE A POSSIBILITY ONCE AGAIN AT KSBM...
KMKE... KRAC AND KENW TONIGHT.

SHOWERS DISSIPATED THIS MORNING. MVFR CUMULUS CLOUDS ARE DEVELOPING
FROM SOUTH TO NORTH EARLY THIS AFTERNOON. A FEW WIDELY SCATTERED
THUNDERSTORMS WILL BE POSSIBLE ACROSS SOUTHERN WI THIS AFTERNOON.
SMALL HAIL IS POSSIBLE FROM MADISON AND WEST... BUT BRIEF PERIODS OF
HEAVY RAIN IS THE MAIN THREAT.

LOOK FOR A PERIOD OF SHOWERS AND THUNDERSTORMS TO TRACK ACROSS SOUTH
CENTRAL AND SOUTHEAST WI MIDDAY SUNDAY INTO SUNDAY AFTERNOON. THERE
IS A CHANCE FOR ISOLATED SEVERE THUNDERSTORMS LATE SUNDAY AFTERNOON
AND SUNDAY EVENING.

MARINE...

A MARINE DENSE FOG ADVISORY FOR ALL OF THE NSH ZONES IS IN EFFECT
UNTIL 15Z SUNDAY. NOT ANTICIPATING MUCH CHANGE IN CONDITIONS DUE TO
LIGHT WINDS ALLOWING FOR DENSE FOG TO CONTINUE OVER THE COOL LAKE
WATERS.

SOUTHERLY WINDS WILL APPROACH SMALL CRAFT ADVISORY LEVELS SUNDAY
AFTERNOON AS LOW PRESSURE STALLS OVER MINNESOTA. EXPECTING WINDS AND
WAVES TO REMAIN JUST BELOW CRITERIA SO NO HEADLINE AT THIS TIME.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 10 AM CDT SUNDAY FOR WIZ052-060-066.
LM...DENSE FOG ADVISORY UNTIL 10 AM CDT SUNDAY FOR LMZ643>646.

&&

$$
UPDATE...MBK


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