Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 040223
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
923 PM CDT THU SEP 3 2015

.UPDATE...SCT STORMS CONTINUE TO FIRE IN VICINITY OF SOUTHWARD
SAGGING COLD FRONT WHERE DEEP INSTABILITY IS LOCATED. MLCAPE UP TO
4000 J/KG IN SOUTHWEST CWA. INSTABILTY AXIS WILL SHIFT SOUTHWEST
AS COOLER...MORE STABLE AIR CONTINUES TO GRADUALLY FILL ACROSS THE
REST OF SOUTHERN WI. WEAK BOUNDARY LAYER MIXING AND COOL...MOIST
FLOW WILL RESULT IN BLEND OF FOG AND SCT-BKN STRATUS THROUGH THE
LATE NIGHT.

&&

.AVIATION/06Z TAFS/...COOL...MOIST LOW LEVEL FLOW AND WEAKER
BOUNDARY LAYER MIXING MAY RESULT IN CONTINUED EXPANSION OF MVFR
CLOUDS OVERNIGHT. WL LIKELY INCLUDE A TEMPO PERIOD IN 00Z TAFS.
OTRW...EXPECT AREAS OF FOG TO DEVELOP AS WELL.

&&

.MARINE...LAKESHORE WEBCAMS NOT SHOWING ANY REDUCED VISIBILITIES
AT THIS POINT DUE TO FOG. WITH LOW LEVEL WINDS SFC WINDS EXPECTED
TO TURN MORE NORTH TO NORTHWEST...EXPECT MOST OF THE THICKER FOG
TO HOLD OFFSHORE. WILL HOLD OFF ON DENSE FOG ADVY FOR NOW...BUT
MAY BE NEEDED IN LATER PERIODS DUE TO PERSISTENT LIGHT FLOW.


&&

.PREV DISCUSSION... /ISSUED 335 PM CDT THU SEP 3 2015/

SHORT TERM...TONIGHT THROUGH SUNDAY

TONIGHT AND FRIDAY...FORECAST CONFIDENCE...MEDIUM

COULD BE A FEW SHOWERS OR STORMS TOWARD THE ILLINOIS BORDER LATE
AFTERNOON INTO TONIGHT AS A SURFACE BOUNDARY DRIFTS SOUTHWARD. AN
AXIS OF 700 MB WARM ADVECTION AND HIGHER RH IS PROGGED TO LIFT
NORTHEASTWARD INTO THE FORECAST AREA TOMORROW...WITH A FEW AFTERNOON
SHOWERS/STORMS NOT OUT OF THE QUESTION. OVERALL THOUGH...EXPECT MOST
PLACES TO REMAIN DRY THROUGH THE DAY TOMORROW.

CLOUDS CONTINUE TO DECREASE THIS AFTERNOON DUE TO DAYTIME MIXING.
SOME MODELS SHOW CLOUDS REFORMING TONIGHT...WHILE OTHERS FOCUS ON
FOG DEVELOPMENT UNDER LIGHT WINDS AND MOSTLY CLEAR SKIES. CONSENSUS
OF MODELS SEEM TO POINT TOWARD THE FOG POTENTIAL...SO KEPT FOG
MENTION IN THE FORECAST.

TEMPS FRIDAY WILL REMAIN WARM AND HUMID...LIKELY JUST A DEGREE OR
TWO SHY OF HIGHS OBSERVED TODAY.

FRIDAY NIGHT THROUGH SATURDAY...FORECAST CONFIDENCE MEDIUM

UPPER RIDGE CONTINUES TO AMPLIFY AHEAD OF DEEPENING WESTERN U.S.
TROUGH WITH THE RIDGE AXIS MOVING OVER THE REGION SATURDAY NIGHT.
MODEL SOLUTIONS HAVE SLIGHT VARIATIONS TO THE LOCATION OF THE 500 MB
CUT-OFF CIRCULATION FROM NRN LOWER MICHIGAN TO EAST-CENTRAL LAKE
MICHIGAN AT 00Z SATURDAY. THIS CUT-OFF WEAKENS AS IT LINGERS OVER
THE REGION THROUGH SATURDAY MORNING BEFORE OPENING UP AND PUSHING
NORTHEAST IN DEVELOPING SW 500 MB FLOW AS THE WESTERN TROUGH MOVES
INTO THE INTERMOUNTAIN WEST.

WEAK FORCING BETWEEN THE CVA FROM THE CUT-OFF AND INCREASING 925-850
MB WARM ADVECTION RESULTS IN PERSISTENT LAYER Q-VECTOR CONVERGENCE
IN THE EAST FRIDAY NIGHT INTO SATURDAY...AND SOME UNDERLYING
CONVERGENCE/WEAK FRONTOGENETIC RESPONSE NEAR THE LAKE WITH DEVELOPING
LATE SATURDAY MORNING/AFTERNOON LAKE BREEZE...WILL KEEP SLIGHT
CHANCES FOR SHOWERS/STORMS IN THE FORECAST. INSTABILITY WITH
AFTERNOON CAPE VALUES AROUND 1000J/KG...BUT WEAK MID-LEVEL LAPSE
RATES AND MINIMAL SHEAR WITH WEAK FLOW THROUGH THE COLUMN WILL
PRECLUDE ANY CHANCE FOR STRONG/SEVERE THUNDERSTORMS.

MUGGY LOWS IN THE UPPER 60S MAY LEAD TO SOME FOG FRIDAY NIGHT. 925
MB TEMPS SUPPORT UPPER 80S TO NEAR 90 IN THE WEST WITH DEVELOPING
LAKE BREEZE KEEPING EASTERN AREAS IN THE LOW-MID 80S. HEAT INDEX
VALUES IN THE WESTERN TWO-THIRDS OF THE CWA COULD REACH 90 TO 95
DEGREES. CLOUDIER SKIES THAN EXPECTED AND ANY PCPN COULD REDUCE HIGH
TEMPS A FEW DEGREES.

SATURDAY NIGHT THROUGH SUNDAY NIGHT...FORECAST CONFIDENCE MEDIUM

BROAD AREA OF SURFACE LOW PRESSURE IN THE PLAINS DEEPENS AND
CONSOLIDATES AS STRONG VORTICITY MAXIMUM MOVES THROUGH BASE OF
WESTERN TROUGH AND LIFTS NORTHEAST AS A CLOSED 500 MB LOW. NEARLY
STACKED SYSTEM LIFTS TO NEAR LAKE WINNIPEG...DRIVING A COLD
FRONT/SURFACE TROUGH INTO CENTRAL WISCONSIN BY 12Z MONDAY.
PRECIPITATION STAYS TIED TO BEST FORCING ALONG THE FRONT SO WILL
KEEP MAJORITY OF FORECAST AREA DRY SUNDAY...WITH ONLY A
COLLABORATIVE SLIGHT CHANCE IN THE FAR NW AFTER 18Z.

HUMID CONDITIONS CONTINUE WITH LOWS AROUND 70...THOUGH INCREASING
CLOUDS IN THE AFTERNOON WILL KEEP SUNDAY HIGHS IN THE UPPER 80S WITH
SSW WINDS TURNING INLAND IN THE AFTERNOON HOLDING LAKESHORE
LOCATIONS IN THE MID 80S. HEAT INDEX VALUES AWAY FROM THE LAKE WILL
BE IN THE 90 TO 93 DEGREE RANGE

POPS INCREASE NW TO SE DURING SUNDAY NIGHT WITH FRONT MOVING INTO
THE AREA...WITH SHOWERS AND STORMS LIKELY IN THE NW HALF. LITTLE IN
THE WAY OF CAPE OR 0-6KM BULK SHEAR WITH STRONGER UPPER LEVEL WINDS
STAYING BACK TO THE NORTHWEST SO LITTLE CHANCE OF SEVERE.

LONG TERM...MONDAY THROUGH THURSDAY...FORECAST CONFIDENCE MEDIUM

REST OF THE LABOR DAY FORECAST DEPENDS ON HOW FAR SOUTHEAST THE
FRONT WILL MOVE AFTER REACHING THE FAR EASTERN CWA/LAKE MICHIGAN
AROUND 18Z MONDAY. ECMWF HANGS IT UP OVER SRN WI WHILE THE GFS AND
GEM PUSH IT INTO IL/IN BEFORE STALLING. WILL KEEP CHANCE POPS FOR
THE DAY AND KEEP THEM IN THE SOUTHERN-MOST COUNTIES ALONG THE IL
BORDER...WITH SLIGHTS TO THE NORTH MONDAY NIGHT.

WILL HAVE CHANCE POPS MOVE BACK INTO THE ENTIRE AREA AS 850 MB
TROUGH SLOWLY MOVES ACROSS THE WESTERN GREAT LAKES AS CLOSED LOW
MEANDERS INTO WESTERN ONTARIO...WITH MODELS SHOWING A SHORT WAVE
CROSSING IL/WI BORDER AREA TUESDAY. COLDER AIR MOVES IN BEHIND THE
850 MB TROUGH WITH HIGH PRESSURE AT THE SURFACE. SLIGHT CHANCE POPS
REMAIN WEDNESDAY DUE TO 500 MB SHORT WAVE TROUGH ON GFS AND WEAKER
SHORT WAVE ENERGY CROSSING THE REGION ON THE ECMWF BUT WITH PW/S OF
0.50 INCH OR LESS LATER SHIFTS MAY BE ABLE TO ELIMINATE.

AVIATION/00Z TAFS/...

COULD SEE A FEW STORMS TONIGHT AND FRIDAY...BUT MOST PLACES SHOULD
REMAIN DRY THROUGH FRIDAY.

CLOUDS CONTINUE TO DECREASE THIS AFTERNOON DUE TO DAYTIME MIXING.
SOME MODELS SHOW CLOUDS REFORMING TONIGHT...WHILE OTHERS FOCUS ON
FOG DEVELOPMENT UNDER LIGHT WINDS AND MOSTLY CLEAR SKIES. CONSENSUS
OF MODELS SEEM TO POINT TOWARD THE FOG POTENTIAL...SO KEPT FOG
MENTION IN THE FORECAST.

IF FOG DOES FORM TONIGHT...IT SHOULD CLEAR OUT FRIDAY MORNING. VFR
CONDITIONS THEN GENERALLY EXPECTED THROUGH THE REMAINDER OF THE
DAY.

MARINE...

STILL SEEING A LITTLE FOG ON SATELLITE BETWEEN PORT WASHINGTON AND
NORTH POINT LIGHT. WITH ONSHORE WINDS PERSISTING THROUGH
FRIDAY...COULD SEE SOME MORE FOG AT TIMES AS WARM AND MOIST
CONDITIONS REMAIN IN THE AREA.

&&

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

$$

UPDATE...MBK


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