Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 171658 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1158 AM CDT SUN MAY 17 2015

.UPDATE...

THE STORM PREDICTION CENTER REMOVED THE UPPER MISSISSIPPI RIVER
VALLEY...INCLUDING SOUTHERN WI... FROM THE ENHANCED RISK FOR SEVERE
WEATHER. WE ARE STILL IN AN AREA OF SLIGHT RISK FOR SEVERE WEATHER.
THIS IS DUE TO LESS INSTABILITY THAN FORECAST.

THE FIRST CONCERN IS THE PRECIP POTENTIAL WITH THE INITIAL WAVE OF
ENERGY LIFTING THROUGH SOUTHERN WI FROM LATE MORNING INTO EARLY
AFTERNOON. THE HRRR/RAP SHOW NUMEROUS SHOWERS/THUNDER DEVELOPING IN
SOUTH CENTRAL WI RIGHT AWAY PRIOR TO 18Z... WHILE THE 12Z NAMNEST
AND 00Z WRF-ARW/NMM DELAY THE DEVELOPMENT. GIVEN CURRENT RADAR
TRENDS... BACKED OFF FROM THE LIKELY POPS THROUGH 19Z. ALL OF THE
MODELS SHOW ENHANCED REFLECTIVITY OVER SOUTHEAST WI 20Z-23Z... SO I
KEPT THE LIKELY POPS FOR THAT TIME PERIOD. EXTENSIVE LOW CLOUDS WILL
INHIBIT WIDESPREAD DEVELOPMENT OF PRECIP... SO POPS COULD BE REDUCED
WITH LATER UPDATES.

AS FOR THE SEVERE POTENTIAL WITH THIS FIRST ROUND... THE CLOUDS ARE
REALLY PUTTING A DAMPER ON STORM DEVELOPMENT. WE WILL NEED SOME
BREAKS IN THE CLOUDS IN ORDER TO INCREASE THE INSTABILITY. HIGHER
INSTABILITY WOULD ALLOW FOR STRONGER STORMS. IT DOES NOT LOOK LIKE
WE WILL HAVE ENOUGH INSTABILITY WITH THIS FIRST ROUND TO PRODUCE
SEVERE WEATHER. ONE MORE CONCERN IS A MID LEVEL WARM LAYER THAT
COULD LIMIT THE INSTABILITY/CAPE AS WELL. BULK SHEAR LOOKS
STRONG THROUGH THE DURATION.

THE MAIN FEATURE THAT WE HAVE BEEN KEYING ON FOR PRODUCING OUR
SEVERE THUNDERSTORM POTENTIAL IN SOUTHERN WI IS AN UPPER LEVEL WAVE
AND A SURFACE PRE-FRONTAL TROUGH ASSOCIATED WITH AN OCCLUDING LOW
PRESSURE SYSTEM OVER THE EASTERN DAKOTAS AND WEST CENTRAL MN. THE
UPPER WAVE NOW LOOKS LIKE IT WILL COME THROUGH SOUTHERN WI A LITTLE
AHEAD OF THE PRE-FRONTAL TROUGH... SO STORMS MAY END UP BEING MORE
SCATTERED IN NATURE RATHER THAN CONCENTRATED IN A SINGLE LINE OF
STRONG CELLS.

SPC REMOVED SOUTHERN WI FROM THE ENHANCED RISK OF SEVERE STORMS FOR
THIS AFTERNOON/EVENING. THE CLOUDS WILL LIMIT OUR SURFACE HEATING
TODAY. THE SMALLER CAPE VALUES EXPECTED AROUND 500 J/KG COULD STILL
PRODUCE SOME LOW-TOPPED THUNDERSTORMS AND THE DECENT BULK SHEAR
COULD ALLOW FOR SOME ISOLATED SUPERCELLS. THIS WOULD MEAN AN
ISOLATED RISK FOR LARGE HAIL AND DAMAGING WIND GUSTS. 0-1 SHEAR IS
NOW LOOKING A LITTLE WEAKER THAN PREVIOUS FORECASTS AS WELL... SO
THE TORNADO RISK IS ALSO A LITTLE LOWER... BUT STILL THERE.


&&

.AVIATION/18Z TAFS/...

IFR CIGS ARE SLOWLY LIFTING TO MVFR LATE THIS MORNING. THERE ARE
SIGNS OF CLEARING LOW CLOUDS OVER FAR SOUTHWEST WI AT 11 AM. FOG
WILL ALSO REMAIN AN ISSUE NEAR THE LAKE THROUGH MID AFTERNOON.

AN AREA OF SHOWERS AND THUNDERSTORMS DEVELOPING OVER SOUTHWEST WI
AROUND THE NOON HOUR SHOULD EXPAND AS THE AREA TRACKS INTO SOUTH
CENTRAL AND SOUTHEAST WI EARLY THIS AFTERNOON. THIS WOULD BE ABOUT A
2 HOUR PERIOD OF PRECIP.

SHOWERS AND STORMS WILL BECOME MORE SCATTERED IN NATURE LATE THIS
AFTERNOON INTO THE EVENING. THE RISK FOR SEVERE WEATHER HAS
DECREASED DUE TO EXTENSIVE CLOUD COVER THIS MORNING. ISOLATED SEVERE
STORMS ARE STILL POSSIBLE.

SHOULD SEE DRY WEATHER RETURN BY MIDNIGHT...WITH DECREASING CLOUDS
OVERNIGHT.

&&

.MARINE...

DENSE FOG ADVISORY WAS EXTENDED UNTIL 21Z/ 4PM THIS AFTERNOON WITH
PERSISTENT SOUTHEAST WINDS AND WARM AND HUMID AIR OVER THE LAKE.
MAY NEED TO EXTEND FOR AREAS NORTH OF MILWAUKEE THROUGH TONIGHT.

&&

.PREV DISCUSSION... /ISSUED 342 AM CDT SUN MAY 17 2015/

TODAY AND TONIGHT...FORECAST CONFIDENCE...MEDIUM

LATEST MODELS CONTINUE TO INDICATE THAT THUNDERSTORMS ARE LIKELY
TODAY. CONSENSUS OF SOLUTIONS POINTS TO THE AFTERNOON AND EARLY
EVENING AS THE BEST WINDOW TO SEE SOME STORMS. SEVERE STORMS REMAIN
A POSSIBILITY...WITH LATEST SPC OUTLOOK HIGHLIGHTING AN ENHANCED
RISK WESTERN HALF OF THE FORECAST AREA AND SLIGHT RISK EAST. ONE
CONCERN IS THE AMOUNT OF CLOUD COVER TODAY AND HOW MUCH THIS WILL
INHIBIT STORM DEVELOPMENT. MESOSCALE MODELS FIRE STORMS BY AROUND
NOON IN THE SOUTHWEST...SPREADING ACROSS THE FORECAST AREA DURING
THE AFTERNOON HOURS. SEEMS KIND OF EARLY TO BUILD A DECENT AMOUNT OF
INSTABILITY GIVEN THE CURRENT CLOUD COVER...SO WILL HAVE TO KEEP AN
EYE ON CLOUD TRENDS. OTHERWISE...WIND PROFILES SUPPORT THE
POSSIBILITY OF SUPERCELLS...WITH HAIL...WIND...AND A FEW TORNADOES
ALL CONCERNS.

COULD SEE A SECOND ROUND OF STORMS DURING THE EVENING HOURS...LIKELY
DEPENDING ON HOW MUCH RECOVERY OCCURS AFTER THE FIRST ROUND. MODELS
GENERALLY SHOW WANING INSTABILITY DURING THE EVENING...SO NOT TOO
EXCITED ABOUT THE LATER STORMS. LOOKS TO TURN DRY BY
MIDNIGHT...WITH DRY WEATHER THEN EXPECTED OVERNIGHT.

ANOTHER CONCERN TODAY IS THE FOG THAT LINGERS NEAR LAKE
MICHIGAN...MAINLY FROM MILWAUKEE NORTHWARD. MILWAUKEE OBS AND
WEBCAMS NOT LOOKING TO BAD AT THE MOMENT...BUT CONDITIONS CONTINUE
TO BOUNCE AROUND A BIT. THUS WILL KEEP THE DENSE FOG ADVISORY GOING
FROM MILWAUKEE COUNTY NORTHWARD. MAY NEED TO EXTEND THROUGH LATE
MORNING OR INTO EARLY AFTERNOON FARTHER NORTH AS LOW LEVEL MOISTURE
CONTINUES TO INCREASE AND WINDS REMAIN ONSHORE.

KEPT HIGH TEMPS TODAY A BIT BELOW WHAT 925 MB TEMPS WOULD SUGGEST
WITH GOOD MIXING...MAINLY BECAUSE OF THE EXPECTED CLOUD COVER AND
AFTERNOON STORM CHANCES. TEMPS TONIGHT SHOULD REMAIN ON THE MILD
SIDE AHEAD OF THE APPROACHING FRONT.

MONDAY - CONFIDENCE...MEDIUM
SURFACE LOW VCNTY LAKE SUPERIOR SHIFTS RAPIDLY EAST. 850 CAA IS
STEADY THOUGH RATHER MILD 925 TEMPS LINGER. STILL A WARM DAY AS
GUSTY WEST WINDS IN GRADIENT REGION IN WAKE OF LOW ALLOWS FOR
MIXING OF THESE LINGERING MILDER 925 TEMPS...RANGING FROM 10C IN
THE NW CWA TO THE TEENS CELSIUS IN THE SE. SO EXPECTING HIGHS WELL
INTO THE 70S ESP IN THE SE CWA.

TUESDAY - CONFIDENCE...MEDIUM
COLD ADVECTION CONTINUES INTO THE MORNING WITH STILL A DECENT
PRESSURE GRADIENT IN PLACE. COLDEST 925 TEMPS OF AROUND 0C ARE
EXPECTED...THOUGH THE NAM SHOWS DOWN TO -3C. HIGH PRESSURE WILL
BUILD IN AND EASE THE WIND REGIME WITH A MUCH COOLER DAY EXPECTED
FROM MONDAY. SOME FROST POTENTIAL IN PARTS OF SRN WI TUESDAY NIGHT
WITH LIGHT WIND REGIME ASSOCIATED WITH HIGH COMBINES WITH
LINGERING EFFECTS OF COOLER AIRMASS.

WEDNESDAY - CONFIDENCE...MEDIUM
SURFACE/850 ANTICYCLONE LOOKS TO BE THE DOMINANT FEATURE THIS
PERIOD WITH GRADUAL WARMING TEMPERATURES. HOWEVER ONSHORE FLOW
WILL KEEP EASTERN AREAS COOLER. MID LEVEL SHORTWAVE LIFTS OUT OF
THE ROCKIES WITH THE ECMWF A BIT MORE TO THE NORTH ON THE PRECIP
SHIELD ASSOCIATED WITH THIS FEATURE. THE GEM AND GFS KEEP THIS
SYSTEM FAR ENOUGH TO MAINTAIN THE DRY LOOK. SO WILL SIDE WITH THE
SUPERBLEND POPS AND KEEP THE POPS IN LINE WITH THE CONSENSUS OF
THE GFS/GEM.

THURSDAY AND FRIDAY - CONFIDENCE...MEDIUM
PRETTY GOOD AGREEMENT THAT HIGH PRESSURE WILL KEEP THINGS QUIET.
DECENT MODIFICATION IN OVERALL THERMAL PROFILE...THOUGH NE WINDS
IN WAKE OF AN EAST/WEST ORIENTED TROUGH/FRONT ARE EXPECTED TO TURN
THINGS COOLER LAKESIDE ON FRIDAY.

SATURDAY - CONFIDENCE...LOW
THE HIGH IS PROGGD TO THE EASTERN SEABOARD WITH A WAA PATTERN
SETTING UP. THE GFS IS A BIT MORE PROGRESSIVE ON THE LOW MOVING
INTO THE CENTRAL PLAINS WITH THE ECMWF SLOWER. NEVERTHELESS THE
ECMWF IS STILL BRINGING THE EASTERN EXTENT OF PRECIP INTO WRN CWA
SO WILL LEAVE SUPERBLEND POPS AS IS FOR NOW.

AVIATION/12Z TAFS/...WILL CONTINUE TO DEAL WITH LOW CLOUDS MOST
PLACES INTO THE MORNING HOURS. FOG WILL ALSO REMAIN AN ISSUE NEAR
THE LAKE...MAINLY FROM MILWAUKEE NORTHWARD. SHOULD SEE AN IMPROVEMENT
IN CIGS BY EARLY OR MID AFTERNOON...WITH VSBY NEAR THE LAKE LIKELY
IMPROVING SOUTH TO NORTH THROUGH THE MORNING HOURS.

THUNDERSTORMS ARE LIKELY TODAY...THE HIGHEST CHANCE DURING THE
AFTERNOON AND EARLY EVENING HOURS. SEVERE STORMS REMAIN A POSSIBILITY.
SHOULD SEE DRY WEATHER RETURN BY MIDNIGHT...WITH DECREASING CLOUDS
OVERNIGHT.

MARINE...WILL KEEP DENSE FOG ADVISORY AS IS FOR NOW. MAY NEED TO
EVENTUALLY EXTEND FOR AREAS MAINLY NORTH OF MILWAUKEE THOUGH...AS
LOW LEVEL MOISTURE CONTINUES TO INCREASE...WHILE SURFACE WINDS REMAIN
FROM THE EAST TO SOUTHEAST. IF THE FOG DOES CONTINUE...SHOULD SEE
IMPROVEMENT DURING THE AFTERNOON AS WINDS BECOME MORE SOUTHERLY.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...DENSE FOG ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR LMZ643>646.

&&

$$

UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...DDV
MONDAY THROUGH SATURDAY...COLLAR


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