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September 3rd-5th Severe Weather Threat


Brewers

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Some pretty good cells south of La Crosse.

MKX's take on thunderstorms:

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

THE RIGHT ENTRANCE REGION OF A 80 KT JET STREAK AND A WEAK SHORTWAVE

TROUGH OVER THE CENTRAL ROCKIES WILL MOVE ACROSS SRN WI TNT. IN THE

LOWER LEVELS OF THE ATMOSPHERE...VERY WEAK AND UNORGANIZED FLOW IS

EXPECTED WITH THE EXCEPTION OF THE LAKE BREEZE TODAY AND EARLY THIS

EVENING. TEMPS NEAR 90 F AND DEWPOINTS WELL INTO THE 60S WILL BOOST

MLCAPES TO 1500 J/KG LATER THIS AFTERNOON WITH ELEVATED CAPE AROUND

1000 J/KG FOR TNT AS TROPOSPHERE MOISTENS AHEAD OF THE AFOREMENTIONED

UPPER FEATURES. THE FEATURES DO APPROACH THE FAR WRN CWA BY EVENING

WITH LITTLE TO NO CAP IN PLACE SO HAVE CHANCE POPS WEST OF MADISON

WITH SLIGHT CHANCE POPS FROM EAST CENTRAL WI INTO SOUTH CENTRAL WI.

FCST SOUNDING SHOW LITTLE TO NO CAP ALONG THE LAKE BREEZE TOWARD

FLD...HENCE THE SLIGHT CHANCE THERE THIS AFTERNOON.

THEN WENT WITH 50 POPS FOR TNT WITH SOME UNCERTAINTY SINCE LOW TO

MID LEVELS SHOWS VERY WEAK FLOW AND NO QG LIFT...HOWEVER VARIOUS

MESO MODELS PRODUCE ABUNDANT CONVECTION FOR TNT. SOME STORMS COULD

BE STRONG GIVEN CAPE VALUES AND INCREASING EFFECTIVE SHEAR TO AROUND

30 KTS AS THE JET STREAK MOVES INTO WI.

TUESDAY AND WEDNESDAY...FORECAST CONFIDENCE...MEDIUM

SHOULD SEE CONVECTION FROM MONDAY NIGHT WINDING DOWN ACROSS THE

SOUTHEAST HALF OF THE FORECAST AREA AS THE SHORTWAVE EXITS TO THE

EAST. TUESDAY AFTERNOON LOOKS TO BE MAINLY DRY...WITH A FAIR AMOUNT

OF SUNSHINE WARMING TEMPS BACK UP INTO THE 80S. DID KEEP A SLIGHT

CHANCE FOR SHOWERS AND STORMS IN THE AFTERNOON...AS SOUNDINGS ARE

FAIRLY UNSTABLE AND MODELS TRYING TO SHOW A WEAK WRINKLE IN THE

FLOW...ALONG WITH NEARBY CONVECTION.

KEPT THE SLIGHT CHANCE GOING INTO TUESDAY EVENING...WITH INCREASING

POPS OVERNIGHT BECOMING LIKELY WEDNESDAY MORNING AS A STRONGER

SYSTEM APPROACHES. MODELS HAVE SPED UP THE TIMING OF THE SURFACE

COLD FRONT WEDNESDAY...SO EXPANDED LIKELY POPS TO THE LAKE IN THE

MORNING...AND TAPERED POPS A BIT QUICKER IN THE WEST FOR THE

AFTERNOON. MODELS HAVE THE BULK OF CONVECTION TO THE EAST BY EARLY

OR MID AFTERNOON...WITH SOME SUNSHINE POSSIBLE LATER IN THE DAY.

SEEMS LIKE A DECENT CHANCE TO RECOVER TO AROUND 80 BY LATE AFTERNOON.

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New day 2 outlook

day2otlk_0600.gif

...UPPER GREAT LAKES/MIDWEST...

SHOWERS AND SCATTERED THUNDERSTORMS SHOULD BE ONGOING AT THE START

OF THE PERIOD ACROSS PORTIONS OF THE UPPER MIDWEST/UPPER MS

VALLEY/WRN UPPER GREAT LAKES REGION...ALONG AND AHEAD OF THE

ADVANCING COLD FRONT. AS THE FRONT PROGRESSES EWD INTO A

DESTABILIZING WARM SECTOR...AN AFTERNOON INCREASE IN CONVECTION CAN

BE EXPECTED -- AIDED BY MODERATELY STRONG WNWLYS ALOFT SPREADING EWD

ATOP THE FRONTAL ZONE. WITH TIME...EVOLUTION OF AT LEAST A

SEMI-ORGANIZED LINE OF STORMS APPEARS LIKELY FROM WI SWD INTO

IL...WITH LOCALLY DAMAGING WINDS AND HAIL ACCOMPANYING BOTH THE LINE

AS WELL AS OTHER/MORE ISOLATED STORMS/STORM CLUSTERS.

SOME THREAT SHOULD CONTINUE INTO THE EVENING AS STORMS SPREAD ACROSS

WI AND IL AND INTO LOWER MI. EVENTUALLY HOWEVER...THE LOSS OF

DIURNAL HEATING/INSTABILITY WILL RESULT IN A SLOWLY DIMINISHING

SEVERE THREAT.

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First thunderstorm warning for Southern Ontario in a while including Peel Region, York Region, and the city of Toronto.

SEVERE THUNDERSTORM WARNING

ISSUED BY ENVIRONMENT CANADA

AT 11:47 AM EDT TUESDAY 4 SEPTEMBER 2012.

---------------------------------------------------------------------

SEVERE THUNDERSTORM WARNING FOR:

=NEW= CITY OF TORONTO

=NEW= MISSISSAUGA - BRAMPTON

=NEW= CALEDON

=NEW= VAUGHAN - RICHMOND HILL - MARKHAM.

---------------------------------------------------------------------

==DISCUSSION==

AT 11:45 RADAR INDICATES A THUNDERSTORM NEAR TORONTO AIRPORT MOVING

NORTHEASTWARDS AT 35 KM/H. STRONG WINDS INTENSE LIGHTNING AND

RAINFALL AMOUNTS IN EXCESS OF 50 MM IN 1 HOUR IS POSSIBLE.

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New day 2 outlook

day2otlk_0600.gif

...UPPER GREAT LAKES/MIDWEST...

SHOWERS AND SCATTERED THUNDERSTORMS SHOULD BE ONGOING AT THE START

OF THE PERIOD ACROSS PORTIONS OF THE UPPER MIDWEST/UPPER MS

VALLEY/WRN UPPER GREAT LAKES REGION...ALONG AND AHEAD OF THE

ADVANCING COLD FRONT. AS THE FRONT PROGRESSES EWD INTO A

DESTABILIZING WARM SECTOR...AN AFTERNOON INCREASE IN CONVECTION CAN

BE EXPECTED -- AIDED BY MODERATELY STRONG WNWLYS ALOFT SPREADING EWD

ATOP THE FRONTAL ZONE. WITH TIME...EVOLUTION OF AT LEAST A

SEMI-ORGANIZED LINE OF STORMS APPEARS LIKELY FROM WI SWD INTO

IL...WITH LOCALLY DAMAGING WINDS AND HAIL ACCOMPANYING BOTH THE LINE

AS WELL AS OTHER/MORE ISOLATED STORMS/STORM CLUSTERS.

SOME THREAT SHOULD CONTINUE INTO THE EVENING AS STORMS SPREAD ACROSS

WI AND IL AND INTO LOWER MI. EVENTUALLY HOWEVER...THE LOSS OF

DIURNAL HEATING/INSTABILITY WILL RESULT IN A SLOWLY DIMINISHING

SEVERE THREAT.

Less risk for Wayne County this time. Didn't have any hope of any severe weather.

Also hello everyone! :tomato:

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I am liking the prospects for tomorrow, the NAM has pretty good shear/instability overlaying the warm sector across Michigan.

Yeah I don't really agree with the SPC outlook cutting off the eastern portion. Looks like DTX doesn't either

RESIDUAL LOW LEVEL MOISTURE RESIDING OVER LOWER MI COMBINED WITH

DAYTIME HEATING /TEMPS POSSIBLY HITTING 90/ WILL RESULT IN 0-1KM ML

CAPE NEAR 2K J/KG. WHILE THE SFC PATTERN OVER SRN MI WILL BE RATHER

CHAOTIC THROUGH MUCH OF THE DAY...THERE ARE INDICATIONS IN RECENT

MODEL SOLUTIONS IN SOME ENHANCED BOUNDARY LAYER CONVERGENCE

RESULTING FROM A WEAK WARM FRONTAL FEATURE LIFTING NORTH AND

ENHANCED TROUGHING IN THE LEE OF LAKE MICHIGAN. WHILE THESE FEATURES

MAY TOUCH OFF SOME SCATTERED CONVECTION EARLY IN THE AFTERNOON...THE

MORE PROBABLE TIME PERIOD FOR THUNDERSTORMS WILL BE LATE IN THE

AFTERNOON THROUGH THE EVENING. THIS WILL BE FOR THE POTENTIAL FOR

TSTMS TO ADVANCE INTO SE MI FROM THE WEST. DAYTIME DESTABILIZATION

ALONG/AHEAD OF THE SFC FRONT...DIFFLUENT FLOW ALOFT AND A 60 KT MID

LEVEL JET SHOULD LEAD TO ROBUST CONVECTIVE DEVELOPMENT ACROSS THE

WRN GREAT LAKES WED AFTERNOON. THE EXPECTED INSTABILITY /THETA E

RIDGE/ OVER SRN MI AND THE EASTWARD ADVANCEMENT OF THE MID LEVEL JET

SHOULD LEAD TO SOME FORWARD PROPAGATION OF UPSTREAM CONVECTION AND

CONTINUES TO SUGGEST THE CHANCE OF SEVERE WEATHER LATE IN THE DAY

WED. AS THE SHEAR INCREASES LATE IN THE DAY...MODEL SOUNDINGS

SUGGEST BOTH LINEAR AND SUPERCELLULAR MODES OF CONVECTION.

Actually one of the better timing events we've had. Always gotta be wary of moring/early afternoon convection limiting the destabilization...but so far the RAP doesn't show anything through 12z

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Yeah I don't really agree with the SPC outlook cutting off the eastern portion. Looks like DTX doesn't either

RESIDUAL LOW LEVEL MOISTURE RESIDING OVER LOWER MI COMBINED WITH

DAYTIME HEATING /TEMPS POSSIBLY HITTING 90/ WILL RESULT IN 0-1KM ML

CAPE NEAR 2K J/KG. WHILE THE SFC PATTERN OVER SRN MI WILL BE RATHER

CHAOTIC THROUGH MUCH OF THE DAY...THERE ARE INDICATIONS IN RECENT

MODEL SOLUTIONS IN SOME ENHANCED BOUNDARY LAYER CONVERGENCE

RESULTING FROM A WEAK WARM FRONTAL FEATURE LIFTING NORTH AND

ENHANCED TROUGHING IN THE LEE OF LAKE MICHIGAN. WHILE THESE FEATURES

MAY TOUCH OFF SOME SCATTERED CONVECTION EARLY IN THE AFTERNOON...THE

MORE PROBABLE TIME PERIOD FOR THUNDERSTORMS WILL BE LATE IN THE

AFTERNOON THROUGH THE EVENING. THIS WILL BE FOR THE POTENTIAL FOR

TSTMS TO ADVANCE INTO SE MI FROM THE WEST. DAYTIME DESTABILIZATION

ALONG/AHEAD OF THE SFC FRONT...DIFFLUENT FLOW ALOFT AND A 60 KT MID

LEVEL JET SHOULD LEAD TO ROBUST CONVECTIVE DEVELOPMENT ACROSS THE

WRN GREAT LAKES WED AFTERNOON. THE EXPECTED INSTABILITY /THETA E

RIDGE/ OVER SRN MI AND THE EASTWARD ADVANCEMENT OF THE MID LEVEL JET

SHOULD LEAD TO SOME FORWARD PROPAGATION OF UPSTREAM CONVECTION AND

CONTINUES TO SUGGEST THE CHANCE OF SEVERE WEATHER LATE IN THE DAY

WED. AS THE SHEAR INCREASES LATE IN THE DAY...MODEL SOUNDINGS

SUGGEST BOTH LINEAR AND SUPERCELLULAR MODES OF CONVECTION.

Actually one of the better timing events we've had. Always gotta be wary of moring/early afternoon convection limiting the destabilization...but so far the RAP doesn't show anything through 12z

Yeah I would agree with this. Btw side note College of Dupage's website as of today's 18Z run of the NAM now has 3 hour increments for their maps centered on the Great Lakes. I definitely like this a lot.

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Don't know...I'm on the north end of the city and it looks like it might just plow through downtown ... Not much rain so far, lots of lightning... very dark.

There's definitely some broad rotation on the southwest side of the storm. Won't threaten you, but areas to the south will have to keep an eye on that to make sure it doesn't tighten up any more. Looks like the cell is digging a bit, so it's moving to the right. Luckily it looks like the worst of the hail core will miss you to the south.

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There's definitely some broad rotation on the southwest side of the storm. Won't threaten you, but areas to the south will have to keep an eye on that to make sure it doesn't tighten up any more. Looks like the cell is digging a bit, so it's moving to the right. Luckily it looks like the worst of the hail core will miss you to the south.

Looks fairly tight to me but not that strong, 50-60 kt. Could easily drop an EF0 or 1 though if it's really as organized as reflectivity suggests.

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Gonna have to watch the lake breeze closely when it interacts with the storms for weak tornado potential.

Also I wonder if all the smoke being ingested into the storm is increasing hail potential, definitely increases cloud condensation nuclei so you get more rain drops and that's probably a better environment for hail growth. Hard to know if that's negligible or significant though. http://whirlwind.aos...snvisflash.html

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