Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 050304
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1004 PM CDT FRI SEP 4 2015

.UPDATE...EXPANDED THE DENSE FOG ADVISORY OVER LAKE MI EARLIER PER THE
WEBCAMS AND SATELLITE IMAGERY. SOME OF THE FOG HAS EXPANDED
SLIGHTLY INLAND AND EXPECT MORE FOG TO DEVELOP ACROSS SRN WI BUT
MORE WIDESPREAD OVER THE EAST WITH ALREADY LOW DEWPOINT
DEPRESSIONS. WILL HOLD OFF ON A DENSE FOG ADVISORY OVER LAND AS
MOST MOS GUIDANCE LIMITS THE DENSE FOG.

OTHERWISE VERY LOW PROBS OF SHOWERS WILL CONTINUE OVER THE FAR
WESTERN CWA GIVEN ITS CLOSE PROXIMITY TO THE SHOWERS OVER MN. ALSO
VERY LOW PROBS FOR A SHOWER OVER THE FAR EASTERN CWA DUE TO ITS
CLOSE PROXIMITY TO THE UPPER LOW OVER WESTERN LOWER MI. SLIGHT
CHANCES OF TSTORMS WILL CONTINUE FOR ERN WI SAT AFT WITH WEAK
CAPPING...A LAKE BREEZE...AND THE UPPER LOW TO THE EAST. BELIEVE
IT WILL STAY DRY OVER SOUTH CENTRAL WI ON SAT AS THE UPPER RIDGE
BUILDS ONCE AGAIN. VERY WARM AND HUMID CONDITIONS WILL CONTINUE
THIS WEEKEND.


&&

.AVIATION/06Z TAFS/...DENSE FOG WILL PREVAIL NEAR LAKE MI WHILE
VSBYS WILL RANGE 1/2 MILE TO 2 MILES AT KMKE AND KENW FOR THE
EARLY MORNING HOURS OF SAT BUT COULD BE LOWER AT TIMES. CIGS OF
200-500 FEET WILL ALSO PREVAIL DURING THIS PERIOD FOR KMKE AND
KENW. VSBYS WILL DROP TO 2-3 MILES INLAND INCLUDING KUES AND KMSN
WITH LOCALLY DENSE SPOTS INCLUDING LOCAL CIGS BELOW 1 KFT. THE FOG
AND STRATUS WILL THEN GRADUALLY DISSIPATE DURING THE MIDDLE TO
LATE MORNING HOURS. VFR CONDITIONS WILL THEN PREVAIL WITH SCT
CUMULUS. THERE WILL BE A SLIGHT CHANCE OF TSTORMS OVER ERN WI DUE
TO THE LAKE BREEZE POSSIBLY TRIGGERING A SHOWER OR STORM.


&&

.PREV DISCUSSION... /ISSUED 320 PM CDT FRI SEP 4 2015/

SHORT TERM...TONIGHT THROUGH MONDAY

TONIGHT AND SATURDAY...FORECAST CONFIDENCE IS HIGH.

A VERY WEAK LOW FROM THE SURFACE TO THE MID AND UPPER LEVELS OF THE
ATMOSPHERE OVER LOWER MICHIGAN IS EXPECTED TO GRADUALLY WEAKEN AS IT
MOVES SOUTHEAST.  MEANWHILE THE UPPER RIDGE WILL EXTEND NORTHEAST A
LITTLE MORE INTO WISCONSIN...AS A STRONG TROUGH BEGINS TO EXIT THE
PACIFIC NORTHWEST.  THE MID/UPPER LEVEL WIND FLOW IS VERY WEAK.
LITTLE IN THE WAY OF TEMPERATURE CHANGE IN THE LOWER AND MID LEVELS
OF THE ATMOSPHERE.

THE WEAK EAST FLOW IS EXPECTED TO BECOME SOUTHWEST SATURDAY WITH A
LAKE BREEZE NEAR LAKE MICHIGAN.

SURFACE BASED CAPE AROUND 2500 JOULES/KG IN AREAS MAINLY SOUTH AND
WEST OF A DELLS TO MADISON TO JANESVILLE LINE LATE THIS AFTERNOON...
IS EXPECTED TO BE AROUND 1500 JOULES/KG ACROSS SOUTHERN WISCONSIN ON
SATURDAY.  HOWEVER WITH LITTLE OR NO FORCING...ANY
SHOWERS/THUNDERSTORMS WOULD BE ISOLATED.

MAIN FORECAST PROBLEM IS THE ERODING STRATUS IN AREAS NORTH OF
MILWAUKEE TO FOND DU LAC INTO EARLY THIS EVENING...THEN SOME
INCREASE IN COVERAGE AGAIN TONIGHT ALONG WITH AREAS OF FOG
DEVELOPING.

LOW CLOUDS/FOG SHOULD ERODE WITH DAYTIME HEATING SATURDAY.

SATURDAY NIGHT THROUGH SUNDAY...FORECAST CONFIDENCE HIGH

LOOKING DRY AS UPPER RIDGE HOLDS OVER REGION WITH UPPER
DIFFLUENCE/DIVERGENCE STAYING WELL NORTH OF FORECAST AREA AS JET
STREAK LIFTS FROM NEAR THE FOUR CORNERS REGION TO SOUTH DAKOTA/WRN
MINNESOTA BY 00Z MONDAY.

WITH THE JET STREAK NEGATIVELY TILTING THE THE WESTERN TROUGH AND
CLOSING IT OFF OVER THE CANADIAN PRAIRIE PROVINCES...LEAD SHORT WAVE
ENERGY EJECTING OUT AHEAD OF THE MAIN TROUGH...AS WELL AS THE
FOCUSED WARM AIR ADVECTION WITH THE LOW-LEVEL JET AND SURFACE
TROUGH/COLD FRONT ALL STAY NORTH AND WEST OF FORECAST AREA THROUGH
SUNDAY.

AFTER MUGGY LOWS IN THE UPPER 60S SATURDAY NIGHT...INCREASING 925 MB
TEMPS INT EH SW FLOW SUPPORT UPPER 80S/90 DEGREE HIGHS THAT PRODUCE
HEAT INDEX VALUES OF 90 TO 95.

SUNDAY NIGHT THROUGH MONDAY...FORECAST CONFIDENCE MEDIUM

WILL MOVE LIKELY POPS INTO THE WEST BETWEEN 00Z AND 06Z...THEN INTO
CENTRAL SECTIONS BETWEEN 06Z AND 12Z WITH CHANCE POPS IN THE EAST
AS 500 MB SHORT WAVE TROUGH DRIVING THE FRONT PUSHES THROUGH REGION
SUNDAY NIGHT WITH WEAKENING SHORT WAVE AND ASSOCIATED OMEGA AND
MOISTURE COVERING THE SOUTHEAST HALF OF FORECAST AREA BY 12Z MONDAY.
SLOWING FRONT PUTS LIKELY POPS IN THE FAR EAST MONDAY MORNING WITH
CHANCE POPS TAPERING TO THE WEST. THE SLOW MOVEMENT OF THE FRONT
KEEPS THE WARM AND HUMID AIRMASS OVER THE REGION WITH LOW TEMPS
HOLDING IN THE UPPER 60S AND LOWER 70S.

LATEST NAM MOST AGGRESSIVE PUSHING THIS FORCING SOUTHEAST OF AREA BY
MONDAY AFTERNOON...WHILE OTHER MODELS ARE SLOWER AND STALL A MORE
DIFFUSE BOUNDARY...AND KEEP ASSOCIATED SHOWER/STORM CHANCES...OVER
THE FAR SOUTH. NAM 850-700MB LAYER FRONTOGENESIS DOES LINGER OVER
THE SOUTHEAST THROUGH THE AFTERNOON...WITH SHOWERS GENERATING IN
AXIS OF FRONTOGENETIC RESPONSE ALONG SURFACE BOUNDARY JUST SOUTH OF
THE WI/IL BORDER MONDAY AFTERNOON. WILL HAVE A TIGHT NORTHWEST TO
SOUTHEAST INCREASING GRADIENT OF POPS TO ACCOUNT FOR THE CONTINUING
CHANCES ASSOCIATED WITH THE MAJORITY SLOWER SOLUTIONS. LOOKING FOR
HIGHS IN THE UPPER 70S TO LOW 80S WITH COOLER AIR HOLDING OFF TO
THE NORTHWEST.

LONG TERM...TUESDAY THROUGH FRIDAY...FORECAST CONFIDENCE MEDIUM

PCPN DEVELOPS AND EXPANDS ALONG STALLED BOUNDARY AS SHORT WAVE
RUNNING UNDER CLOSED CANADIAN LOW MOVES ACROSS IOWA MONDAY NIGHT AND
OVER SRN WI/NRN IL TUESDAY. WEAK SECONDARY WAVE ROTATING AROUND MAIN
LOW HAS BLENDED SOLUTION KEEPING LOW CHANCE POPS GOING FOR TUESDAY
NIGHT AND SLIGHT CHANCES INTO WEDNESDAY...THOUGH ECMWF AND CANADIAN
GEM ARE DRY AND LOW POPS MAY BE PULLED IF LATER RUNS CONTINUE TO
SHOW DRY HIGH PRESSURE BUILDING IN.

MODELS STRAY AFTER WEDNESDAY WITH TIMING/STRENGTH DIFFERENCES WITH
STRONGER SHORT WAVE TROUGH AND RESULTING SURFACE PRESSURE
DEVELOPMENT IN THE PLAINS. GFS BRINGS SURFACE LOW PRESSURE ACROSS
THE STATE THURSDAY AND EAST OF THE AREA BY 06Z FRIDAY...WHILE ECMWF
BRINGS A WEAK SURFACE TROUGH ACROSS THURSDAY AFTERNOON AND
NIGHT...WITH PCPN LINGERING INTO FRIDAY EVENING AS IT BRINGS A
SURFACE WAVE UP THE TROUGH. BLENDED SOLUTION HAS SLIGHT CHANCE POPS
OFF AND ON FROM WEDNESDAY THROUGH FRIDAY. COOLER TEMPERATURES FOR
THE EXTENDED THAT WILL START OUT A BIT ABOVE NORMAL ON TUESDAY...
COOLING TO AROUND NORMAL FOR WEDNESDAY AND THURSDAY AND THEN BELOW
NORMAL FOR NEXT FRIDAY.

AVIATION/00Z TAFS/...

THE STRATUS WAS MAINLY MVFR FROM NORTH OF MILWAUKEE TO NEAR
FOND DU LAC.

EXPECT THE STRATUS AND FOG TO EXPAND AGAIN TONIGHT WITH
IFR/LIFR...ESPECIALLY IN THE CURRENT STRATUS AREA...WITH MORE
SCATTERED IFR/LIFR FOG TO THE SOUTHWEST...AND PATCHY IFR/LIFR
SOUTHWEST OF MADISON.

LOW CLOUDS SHOULD ERODE SATURDAY WITH DAYTIME HEATING AS THE LOW
LEVEL FLOW BECOMES MORE SOUTHWEST.  HOWEVER A LAKE BREEZE IS
EXPECTED NEAR LAKE MICHIGAN.

MARINE...

A DENSE FOG ADVISORY IS IN EFFECT UNITL 1 PM FOR THE WESTERN SHORE
OF LAKE MI. DENSE FOG WILL CONTINUE TO BE A THREAT OVER THE
NEARSHORE WATERS THROUGH THE WEEKEND DUE TO A HUMID AIRMASS OVER
THE RELATIVELY COOL WATERS OF LAKE MI.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...DENSE FOG ADVISORY UNTIL 1 PM CDT SATURDAY FOR LMZ643>646.

&&

$$

UPDATE...GEHRING
TONIGHT/SATURDAY AND AVIATION/MARINE...HENTZ
SATURDAY NIGHT THROUGH FRIDAY...REM



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