Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 231530 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1030 AM CDT SAT AUG 23 2014

.UPDATE...

VISIBILITIES HAVE IMPROVED ACROSS SOUTHERN WISCONSIN...SO LET THE
DENSE FOG ADVISORY EXPIRE.

IN THE PROCESS OF UPDATING POPS TO REFLECT CURRENT CONVECTION
APPROACHING FROM THE SOUTHWEST. LOOKS LIKE THESE STORMS SHOULD
HOLD TOGETHER FAIRLY WELL TO ABOUT A LINE FROM THE WISCONSIN DELLS
TO MADISON TO BURLINGTON...WITH MESOSCALE MODELS DIMINISHING THE
CONVECTION AFTER THAT. THIS IS A SLOW MOVING COMPLEX AND IS
PRODUCING A LOT OF CLOUDINESS IN THE AREA. STARTING TO LOOK LIKE
HIGH TEMPS WILL NEED TO BE LOWERED A BIT FOR THE AFTERNOON AS
THERE IS NOT SIGNIFICANT CLEARING BEHIND THIS LINE.

&&

.AVIATION/18Z TAFS/...

VSBYS AND CIGS WILL CONTINUE TO GENERALLY IMPROVE THIS MORNING
OUTSIDE OF SHOWERS/STORMS. THE EXCEPTION WILL BE NEAR THE LAKE
MICHIGAN SHORE WHERE SOME LOWER CONDITIONS WILL PROBABLY LINGER
THROUGH AT LEAST LATE MORNING DUE TO THE STRATUS/FOG OVER LAKE
MICHIGAN. COULD SEE SOME MORE FOG TONIGHT INTO SUNDAY MORNING.

CURRENTLY MONITORING A LINE OF STORMS APPROACHING THE AREA. LOOKS
LIKE THESE STORMS SHOULD HOLD TOGETHER FAIRLY WELL TO ABOUT A LINE
FROM THE WISCONSIN DELLS TO MADISON TO BURLINGTON...WITH
MESOSCALE MODELS DIMINISHING THE CONVECTION AFTER THAT. WILL SEE
VISIBILITIES COME BACK DOWN QUITE FOR A SHORT TIME IN AREAS OF
HEAVY RAINFALL...PROBABLY LOCALLY 1/2SM TO 1 SM.

COULD SEE A STRAY SHOWER OR STORM TONIGHT AND SUNDAY...BUT
OTHERWISE IT LOOKS MAINLY DRY THROUGH TOMORROW AFTER THIS
CONVECTIVE COMPLEX PUSHES THROUGH.

&&

.MARINE...

EXTENDED THE DENSE FOG ADVISORY UNTIL 3 PM CDT BASED ON LATEST
WEBCAMS...SATELLITE IMAGERY...AND FORECAST MODELS. CONDITIONS
REMAIN FAIRLY GOOD NEAR THE SHORE FROM PORT WASHINGTON TO
SHEBOYGAN...BUT SATELLITE IS SHOWING FOG JUST OFF SHORE THAT MAY
PUSH BACK IN. COULD SEE SOME MORE FOG TONIGHT INTO SUNDAY MORNING.

&&

.PREV DISCUSSION... /ISSUED 338 AM CDT SAT AUG 23 2014/

TODAY AND TONIGHT...FORECAST CONFIDENCE IS HIGH.

THE MID/UPPER LEVEL RIDGE BUILDS ACROSS WISCONSIN TODAY AND
TONIGHT. THERE IS SOME WEAK UPPER DIVERGENCE THIS AFTERNOON AND
EVENING...ALONG WITH MAINLY WEAK UPPER MOTION AT 700 MB. LITTLE IN
THE WAY OF A CAP ON THE NAM FORECAST SOUNDINGS...SO THE 2000
JOULES/KG OF ZERO TO 1 KM MIXED LAYER CAPE ALONG WITH THE UPWARD
MOTION AND UPPER DIVERGENCE SHOULD BE ENOUGH FOR SCATTERED
SHOWERS/THUNDERSTORMS. THERE WILL BE A LAKE BREEZE BOUNDARY THAT
MAY ACT AS A TRIGGERING MECHANISM. WITH THE WEAK FLOW THE STORMS
COULD CAUSE SOME ISOLATED HEAVY RAINS.

THE MAIN CONCERN IS THE MOIST AIR OFF LAKE MICHIGAN CAUSING DENSE
FOG AND STRATUS. LOWEST VISIBILITIES ARE IN THE COUNTIES BORDERING
THE LAKE. THE LIGHT EAST FLOW WILL PERSIST TONIGHT...SO MORE FOG
AND STRATUS...ESPECIALLY NEAR LAKE MICHIGAN IS EXPECTED.

ANOTHER CONCERN IS HEAT INDEX VALUES. FOR THE MOST PART THEY
SHOULD BE IN THE MID 90S...ALTHOUGH A FEW AREAS...LIKE THE
WISCONSIN RIVER VALLEY COULD APPROACH 100.

SHORT TERM...SUNDAY THROUGH MONDAY NIGHT...FORECAST CONFIDENCE IS
MEDIUM.

MODELS TAKING SURFACE LOW FROM NORTH DAKOTA INTO MANITOBA CANADA
SUNDAY AND SUNDAY NIGHT. THIS ALLOWS FOR SOUTHEAST WINDS TO OCCUR
OVER THE AREA...WITH GRADUAL WARM AIR ADVECTION. THIS SHOULD ALLOW
FOR A CAPPED AIRMASS OVER THE AREA...NAM MORE AGGRESSIVE WITH THE
CAP THAN THE GFS. THUS...NAM/CANADIAN ARE DRY SUNDAY...WITH LIGHT
QPF ON GFS/ECMWF BY 00Z MONDAY. OPTED TO MAINTAIN DRY FORECAST
SUNDAY GIVEN LACK OF DECENT FORCING FOR UPWARD VERTICAL MOTION.

COLD FRONT APPROACHES THE AREA FROM THE WEST SUNDAY NIGHT...SO
KEPT LOWER END POPS THERE. MODELS THEN DIFFER WITH THE FRONTAL
BOUNDARY PLACEMENT OVER THE REGION MONDAY INTO MONDAY NIGHT.
GFS KEEPS STALLED BOUNDARY NORTH OF THE AREA...WITH THE NAM AND
ECMWF NEAR OR OVER THE AREA...WITH THE CANADIAN TO THE SOUTH. LOW
LEVEL JET TRIES TO POINT TOWARD THE AREA MONDAY INTO MONDAY
NIGHT...THOUGH THERE ARE DIFFERENCES HERE AS WELL BETWEEN THE
MODELS.

FOR NOW...KEPT CHANCE POPS GOING FOR MONDAY INTO MONDAY NIGHT.
GOOD AMOUNT OF MEAN LAYER/ELEVATED CAPES DURING THE SUNDAY TO
MONDAY NIGHT PERIOD WITH RELATIVELY WEAK DEEP LAYER SHEAR SEEN ON
AREA FORECAST SOUNDINGS. HIGH PRECIPITABLE WATER VALUES SUGGEST
HEAVY RAINFALL IS POSSIBLE WITH ANY OF THE STORMS...WITH SOME HAIL
AND GUSTY WINDS POSSIBLE IN THE STRONGEST STORMS.

HIGHS SUNDAY AND MONDAY SHOULD REACH INTO THE UPPER 80S TO LOWER
90S WELL INLAND...WITH COOLER VALUES NEAR LAKE MICHIGAN INCLUDING
THE MILWAUKEE METRO AREA WITH ONSHORE WINDS. DEW POINTS IN THE 70S
SUGGEST HEAT INDEX VALUES IN THE 95 TO 103 DEGREE RANGE
SUNDAY...WITH 95 TO 99 ON MONDAY. CLOUDS WITH POSSIBLE
SHOWERS/STORMS MAY LIMIT THE HEAT SOMEWHAT ON MONDAY. STILL...A
HEAT ADVISORY MAY BE NEEDED IN LATER FORECASTS FOR MAINLY SOUTH
CENTRAL WISCONSIN FOR EACH DAY.

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

GFS/ECMWF TRYING TO SHOW QPF OVER THE REGION WITHIN AN AREA OF
LOW LEVEL FRONTOGENESIS RESPONSE TUESDAY INTO WEDNESDAY. GFS
TAKING SURFACE LOW NORTHEAST THROUGH THE AREA WEDNESDAY INTO
THURSDAY...WITH DRIER AIR FOR THE END OF THE WEEK. THE ECMWF KEEPS
THE BAROCLINIC ZONE NEAR THE AREA THROUGH THE END OF THE WEEK.

FOR NOW...WILL CONTINUE WITH CONSENSUS BLEND OF MODELS FOR POPS
AND TEMPERATURES FOR THIS PERIOD. LOOKS LIKE A GOOD SHOT AT
SHOWERS AND STORMS FOR TUESDAY NIGHT AND WEDNESDAY. GOOD MEAN
LAYER/ELEVATED CAPES WITH DECENT DEEP LAYER SHEAR SUGGESTS A
POSSIBILITY FOR STRONG/SEVERE STORMS TUESDAY NIGHT INTO
WEDNESDAY. PRECIPITABLE WATER VALUES REMAIN HIGH...SO HEAVY
RAINFALL WOULD ALSO BE POSSIBLE DURING THIS TIME.

AVIATION/12Z TAFS/...

AREAS OF IFR/LIFR OVER SOUTH CENTRAL WISCONSIN...WITH WIDESPREAD
LIFR OVER THE SOUTHEAST...ESPECIALLY WITHIN 40 MILES OF LAKE
MICHIGAN. THE FOG/STRATUS WILL GRADUALLY LIFT LATER THIS MORNING
WITH MOST AREAS EXPECTED TO SCATTER OUT TO VFR. HOWEVER SOME LOWER
VISIBILITIES/STRATUS MAY PERSIST ALONG LAKE MICHIGAN WITH THE
LIGHT EAST WINDS.

CHANCES FOR THUNDER INCREASE THIS AFTERNOON AND EVENING WITH AN
APPROACHING WARM FRONT.

MORE IFR/LIFR CONDITIONS IN FOG ARE EXPECTED TONIGHT...ESPECIALLY
NEAR LAKE MICHIGAN.

MARINE...

DENSE FOG ADVISORY IN EFFECT FOR ALL MARINE NEARSHORE ZONES UNTIL
10 AM FOR WIDESPREAD FOG WITH VSBYS OF 1 MILE OR LESS. THE MOIST
FLOW WILL CONTINUE WITH LIGHT EAST WINDS AND SOME FOG IS EXPECTED
IN THE AFTERNOON AND EVENING...THEN BECOMING MORE WIDESPREAD AND
DENSE AGAIN LATER TONIGHT.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...DENSE FOG ADVISORY UNTIL 3 PM CDT THIS AFTERNOON FOR LMZ643>646.

&&

$$

UPDATE...DDV
TODAY/TONIGHT AND AVIATION/MARINE...HENTZ
SUNDAY THROUGH FRIDAY...WOOD


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