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June 1-5th Severe Weather


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You guys think they will hatch the day 1 outlook?

I'd lean no but it's close. I'm not sure whether sig hail or sig wind is more likely. Guess convective mode will play a role.

I don't know. If I had to choose one or the other, I would hatch hail given the high-res models' tendencies for semi-discrete/discrete structures for part of the event, though I would probably hatch both. I also would make sure there is a 5% tornado for northern IL in case the winds stay more backed/lake breeze sets up.

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I don't know. If I had to choose one or the other, I would hatch hail given the high-res models' tendencies for semi-discrete/discrete structures for part of the event, though I would probably hatch both. I also would make sure there is a 5% tornado for northern IL in case the winds stay more backed/lake breeze sets up.

Exactly what I was thinking 30% hatched hail and wind and 5% probs for tornadoes.

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Sure enough, looking more closely at the SPC WRF, it's got a damn boundary coming off the lake, inducing the winds to back ahead of it and substantially increasing low-level shear just ahead of those initial discrete cells at 23z. Damnit that had better not happen or there will be hell to pay for someone.

today_1h_f23.gif

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I don't know. If I had to choose one or the other, I would hatch hail given the high-res models' tendencies for semi-discrete/discrete structures for part of the event, though I would probably hatch both. I also would make sure there is a 5% tornado for northern IL in case the winds stay more backed/lake breeze sets up.

Pretty much the entire model suite advertising mid level lapse rates approaching 8 C/km too. Throw the rotating updraft together with high CAPE supporting a large portion of it being in the -10 to -30 C zone and I would say big hail is a threat.

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Pretty much the entire model suite advertising mid level lapse rates approaching 8 C/km too. Throw the rotating updraft together with high CAPE supporting a large portion of it being in the -10 to -30 C zone and I would say big hail is a threat.

Yeah I could totally see some unGodly hail sizes coming out of this region tomorrow...

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tornado threat looks pretty low imo, unless we can somehow lay down a boundary that can increase the low level srh. Hail is the big threat and possible bowing sections of a line, but winds aren't unidirectional with storm movement so i'll lean with some 1.5-2.0 inch threat for hail being the big news. If winds somehow find a way to back or at least go southerly i could see a quick spin up, certainly not a long track sort of day.

edit: actually wind threat is decent, I didn't check some of the local soundings I thought we had some rapid SE moving storms, a W-E moving storm along the front can bow out and go nuts so wind-hail should probably be a 30-30 threat.

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WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP INVOF FRONTAL ZONE FROM SRN APPALACHIANS NWWD ACROSS MID MS VALLEY REGION...COVERAGE BECOMING MORE UNCERTAIN/ISOLATED WITH NWWD EXTENT FROM MS RIVER. ADDITIONAL FOCI MAY CONSIST OF OUTFLOW BOUNDARIES FROM CONVECTION PREVIOUS NIGHT OR ON MORNING OF DAY-2. ANY MCV LINGERING FROM PREVIOUS ACTIVITY ALSO MAY DEVELOP AND INFLUENCE CONVECTIVE POTENTIAL OVER THIS CORRIDOR.

CONDITIONAL SUPERCELL THREAT EXISTS...ESPECIALLY FROM OH RIVER REGION WNWWD WHERE BACKED SFC WINDS...SLIGHTLY ENLARGED LOW-LEVEL HODOGRAPHS...STG DIRECTIONAL SHEAR AND LARGE CAPE ARE EXPECTED. LACK OF MORE ROBUST MID-UPPER LEVEL FLOW ACROSS THIS AREA INDICATES POTENTIAL FOR HEAVY-PRECIP CHARACTER AND UPSCALE/CLUSTERING DEVELOPMENT SOON AFTER INDIVIDUAL TSTMS MATURE. RESERVOIR OF RICH LOW-LEVEL MOISTURE WILL BE CONCENTRATED INVOF FRONTAL ZONE...WITH RELATIVELY DEEPENED BOUNDARY LAYER CONTAINING SFC DEW POINTS UPPER 60S TO LOW 70S F...SUPPORTING MLCAPE 3000-4000 J/KG UNDER AREA OF RELATIVELY STEEP LAPSE RATED FROM INDIANA WWD. HOWEVER...THOSE STEEP LAPSE RATES ARE RELATED TO ELEVATED MIXED-LAYER AIR MASS THAT ALSO WILL PROVIDE PROGRESSIVELY STRONGER CAPPING AND MORE UNCERTAINTY REGARDING CONVECTIVE INITIATION...ESPECIALLY FROM MO/IA BORDER REGION WWD TO NEB.

day2.prob.gif

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The 10z RUC is quite scary if it were to verify...It pops a discrete supercell between DBQ and FEP at 20z and slowly moves southeastward staying discrete in a very unstable environment under 500mb flow of 45kts...by 22z the storm is between DKB and RFD with the lake breeze starting to move west across chi metro...I'm still not sure on the tornado threat but FWIW..the RUC increases 0-3km EHI's to around 4-6 along the I-80/88 corridors by 22z.

20z

22z

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Pretty quiet start to the morning convection wise, including no southeast MCS present across Wisconsin, which i had suspect might sends a lake enhanced outflow boundary down the lake and stabilize far northeast Illinois. Also ot seeing much out there to discount the rather extreme CAPE forecast for the area, heck sbcape is already 2500 with an LI of -8 over far southern Wisconsin and it's not even 7am.

The 0z SPC WRF solution screems urban flash flood threat with embedded marbles. I was hoping to hang and watch some towers fire up to my south, but my concern is growing....just don't think the lake front comes through in time. Fun forecast either way.

btw, gotta love free AC

temperature rising to near 87 by noon, then falling to around 65 during the remainder of the day.
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The 10z RUC is quite scary if it were to verify...It pops a discrete supercell between DBQ and FEP at 20z and slowly moves southeastward staying discrete in a very unstable environment under 500mb flow of 45kts...by 22z the storm is between DKB and RFD with the lake breeze starting to move west across chi metro...I'm still not sure on the tornado threat but FWIW..the RUC increases 0-3km EHI's to around 4-6 along the I-80/88 corridors by 22z.

IMO the tornado threat is pretty real for a narrow corridor across northeast Illinois away from the lake. We've seen enough spinups in super high CAPE environment cells encountering lake fronts to know what can happen. IF discrete action is heading into the area later and if there is a lake front pushing west, i'm sure LOT and the SPC will be all over it.

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Pretty quiet start to the morning convection wise, including no southeast MCS present across Wisconsin, which i had suspect might sends a lake enhanced outflow boundary down the lake and stabilize far northeast Illinois. Also ot seeing much out there to discount the rather extreme CAPE forecast for the area, heck sbcape is already 2500 with an LI of -8 over far southern Wisconsin and it's not even 7am.

The 0z SPC WRF solution screems urban flash flood threat with embedded marbles. I was hoping to hang and watch some towers fire up to my south, but my concern is growing....just don't think the lake front comes through in time. Fun forecast either way.

btw, gotta love free AC

You can see the lake breeze boundary in the instability gradient at 22z, will be interesting watching the develop of this..

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You can see the lake breeze boundary in the instability gradient at 22z, will be interesting watching the develop of this..

22z is a pretty typical time from a lake breeze to have come through, just not sure convection can hold off until then...unlikely actually.

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:popcorn:

SEVERE WEATHER BULLETIN

ISSUED BY ENVIRONMENT CANADA

AT 8:56 AM EDT SATURDAY 4 JUNE 2011.

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

WATCHES/WARNINGS IN EFFECT FOR SOUTHERN ONTARIO...

SEVERE THUNDERSTORM WATCH FOR:

=NEW= HURON COUNTY - PERTH COUNTY

=NEW= WATERLOO REGION - WELLINGTON COUNTY

GREY COUNTY - BRUCE.COUNTY

..SEVERE THUNDERSTORMS POSSIBLE THIS MORNING..

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