April 14-17 Severe Prospects

[Hoosier]

Yeah I am not following the logic on this one at all. I thought for sure we'd see 30% risks and maybe even hatched areas up in WI. Even the discussion part mentions the risk as being pretty good yet only 15%.

If it were me I probably would've connected the 2 slight risk areas and maybe put a 30% up north. Based on the disco it seems like they aren't discounting the NAM's higher instability. That combined with the very strong wind field would at least point to a decent damaging wind threat especially with any linear type organization.

[Stebo]

If it were me I probably would've connected the 2 slight risk areas and maybe put a 30% up north. Based on the disco it seems like they aren't discounting the NAM's higher instability. That combined with the very strong wind field would at least point to a decent damaging wind threat especially with any linear type organization.

The last 2 outlooks read as if they are following the GFS and nothing else... To me this is a dangerous notion. I would agree with your thought of a 30% north 15% connecting down to other 30%. I would agree it isn't a slam dunk for a tornado outbreak, but that kind of wind shear plus instability plus a front would at least argue a good shot at some convection. Not to mention anything that moves in from the SW from Saturday's stuff.

[RCNYILWX]

Yeah I am not following the logic on this one at all. I thought for sure we'd see 30% risks and maybe even hatched areas up in WI. Even the discussion part mentions the risk as being pretty good yet only 15%.

This set-up looks uncannily similar to 4/10/11, so not sure either why a larger area is not outlooked, and as you mentioned, at least some hatched areas where the greatest tornado risk exists in Wisconsin. If anything, the wind fields appear on the modeling appear to be even more extreme than on 4/10/11. I don't think the tornado threat is zero over northern Illinois either, if there can be discrete development ahead of the cold front late Sunday afternoon or early evening, but a severe squall line is certainly possible if the primary convective development remains just ahead of or along the front. Furthermore, with such extreme shear, couldn't rule out mesovortices along a squall line.

[RCNYILWX]

If it were me I probably would've connected the 2 slight risk areas and maybe put a 30% up north. Based on the disco it seems like they aren't discounting the NAM's higher instability. That combined with the very strong wind field would at least point to a decent damaging wind threat especially with any linear type organization.

Completely agree with this, I'm very surprised the outlook wasn't really changed from the Day 3. There's more than an enough instability on the NAM, which appears to be the much more realistic solution, to cause problems, given the strong wind field.

[Stebo]

I expect revisions to the day 2. NAM showing higher instability up there this run and the SREF starting to pop bigger numbers

[daddylonglegs]

La Crosse's thinking....

THE FOCUS THEN GOES TO THE TORNADO/SUPERCELL POTENTIAL ON SUNDAY

AS THE CLOSED MID LEVEL LOW LIFTS NORTHEAST ACROSS THE PLAINS AND

A RESULTANT SURFACE LOW MOVES FROM NEBRASKA INTO MINNESOTA. THE

SETUP HAS NOT CHANGED MUCH WITH THE SURFACE LOW GETTING INTO

SOUTHERN MINNESOTA SUNDAY MORNING. MOST OF THE OVERNIGHT WARM AIR

ADVECTION STORMS SHOULD HAVE LIFTED UP TO THE NORTH OF THE

FORECAST AREA WITH THE WARM SECTOR WELL IN PLACE EARLY ON SUNDAY.

IT APPEARS THAT THERE WILL BE AN EASTERN WING OF CONVECTION THAT

DEVELOPS ALONG THE EASTERN RIM OF THE 925-850MB MOISTURE TRANSPORT

IN THE MORNING/AFTERNOON WHICH COULD PRODUCE SOME HAIL/WINDS...BUT

THE MAIN SHOW SHOULD BE WITH THE CONVECTION THAT DEVELOPS ALONG

THE DRY LINE FURTHER WEST. AS THIS FIRST LINE OF STORMS FORM AND

MOVE INTO EASTERN WISCONSIN LATE MORNING/EARLY AFTERNOON

SUNDAY...THE AIR MASS WEST OF IT WILL REMAIN UNSTABLE IN THE

1000-2000 J/KG RANGE. THE DRY LINE SHOULD ACT AS A FORCING

MECHANISM TO GET STORMS TO DEVELOP IN THE AFTERNOON. BASED ON THE

TIMING OF THIS FEATURE OFF OF THE 14.00Z NAM/GFS AND HI-RES ARW-

EAST/NMM-EAST...IT APPEARS THAT THE DRYLINE WILL COME THROUGH

SOUTHEAST MINNESOTA/NORTHEAST IOWA IN THE PEAK HEATING HOURS. WIND

SHEAR PROFILES STILL LOOK FAVORABLE FOR STORM ORGANIZATION WITH

MORE CURVATURE TO THE LOW LEVEL PORTION OF THE HODOGRAPH FURTHER

EAST IN WISCONSIN. THEREFORE...AM THINKING THAT THE MAIN TORNADIC

THREAT WILL START IN SOUTHEAST MINNESOTA/NORTHEAST IOWA IN THE MID

TO LATE AFTERNOON BEFORE SHIFTING INTO WESTERN WISCONSIN IN THE

EARLY EVENING HOURS. HOW LONG THE STORMS CAN STAY DISCRETE WILL

DETERMINE HOW LONG THE TORNADO THREAT LASTS WITH MCS DEVELOPMENT

POSSIBLE IN THE EVENING. WITH 0-6KM SHEAR VECTORS NOT VERY

PERPENDICULAR TO THE BOUNDARY...THINKING THAT THE WINDOW WILL BE

SOMEWHAT SHORT LIVED FOR THE SUPERCELLS TO FORM BEFORE MORPHING

INTO A LINE.

[SpartyOn]

Terrible event getting ready to unfold in NEB and KS. Prayers guys!

[trapperman]

This set-up looks uncannily similar to 4/10/11, so not sure either why a larger area is not outlooked, and as you mentioned, at least some hatched areas where the greatest tornado risk exists in Wisconsin. If anything, the wind fields appear on the modeling appear to be even more extreme than on 4/10/11. I don't think the tornado threat is zero over northern Illinois either, if there can be discrete development ahead of the cold front late Sunday afternoon or early evening, but a severe squall line is certainly possible if the primary convective development remains just ahead of or along the front. Furthermore, with such extreme shear, couldn't rule out mesovortices along a squall line.

They had enough to deal with last night for today. I think honestly this is the reason. Be willing to bet a 30% pops up there in the next update

[ChiWxWatcher]

Prayers to everyone in the path of the high risk today, and to the storm chasers- they are going to need it.

[oldlogin]

http://www.kokomo-weather.com/RUC/

Another tool for severe Wx .. We have used it before but with so much data available it sometimes get forgotten

[TimChgo9]

Some clouds this morning, no rain present. LOT seems to think storms of some kind for the northern half of the CWA for today. However, the situation in the Plains looks frightening. I am wondering if SPC may update the Day 2 and push the thread a bit farther east for tomorrow? LOT seems to have some concerns for tomorrow. High winds, at the very least, seem to be on tap for tomorrow for SE WI, NE IL, NW IN and areas a bit farther south.

SUNDAY AND SUNDAY NIGHT....WINDS...SEVERE CHANCES...AND TEMPS ARE

THE MAIN CONCERNS FOR SUNDAY/SUNDAY EVENING. THE UPPER TROUGH WILL

BE LIFTING INTO EASTERN SOUTH DAKOTA WITH THE SURFACE LOW MOVING

INTO SOUTHERN MINNESOTA. THE WARM FRONT WILL BE WELL TO THE NORTH OF

THE AREA LEAVING STRONG SOUTH TO SOUTHWESTERLY WINDS AND VERY WARM

AND SOMEWHAT HUMID AIR IN PLACE ACROSS THE AREA. MODELS SEEM TO BE

HAVING TROUBLE HANDLING THE DEGREE OF MIXING AND THE AMOUNT OF CLOUD

COVER IN PLACE WHICH WILL COMPLICATE THE WIND FORECAST. LOW LEVEL

WINDS STEADILY INCREASE THROUGH THE DAY...ESPECIALLY LATE IN THE

AFTERNOON. WITH GOOD MIXING WIND GUSTS TO AROUND 30 KT ARE QUITE

POSSIBLE THROUGH EARLY AFTERNOON BEFORE GUST POTENTIAL INCREASES

LATE AS SPEEDS INCREASE TO AROUND 40 KT AT 1500 FT BY LATE AFTERNOON

AND TO 50+ KT AT 2000 FT BY EVENING. END RESULT MAY BE A NEED FOR A

WIND ADVISORY. WITH THE STRONG SOUTHWESTERLY WIND TEMPS SHOULD WARM

TO THE UPPER 70S AND LOWER 80S ACROSS THE AREA. THE SURFACE LOW WILL

MOVE INTO NORTHERN WISCONSIN SUNDAY EVENING WHILE THE THE ATTENDANT

COLD FRONT CROSSES THE AREA. A PRONOUNCED DRY SLOT WILL BE LIFTING

NORTHWARD AHEAD OF THE UPPER TROUGH. IT ALSO APPEARS THAT THERE MAY

BE A SHORTWAVE LIFTING NORTHEASTWARD FROM THE LOWER MISSISSIPPI RIVER

VALLEY JUST AHEAD OF THE FRONT. MODERATE INSTABILITY IS EXPECTED TO

BE IN PLACE AND LATEST GUIDANCE SHOWS FORCING FROM THE FRONT AND

THIS WAVE ARRIVING OVER THE AREA BY EARLY EVENING. DEEP LAYER SHEAR

WILL BE INCREASING AS THE LOW LEVEL WINDS INTENSIFY LATE IN THE DAY

WITH 0-6 KM VALUES IN THE 50-60 KT RANGE AHEAD OF THE FRONT BY EARLY

EVENING. 0-1 KM SHEAR INCREASES FROM 25-30 KT TO AROUND 35 KT DURING

THE EARLY EVENING. THE SHEAR PROFILE INDICATED BY FORECAST SOUNDINGS

IS PRETTY UNIDIRECTIONAL AND AN ISALLOBARIC TURNING TO INCREASE

DIRECTIONAL CHANGE MAY BE MITIGATED BY THE FACT THAT THE LOW LOOKS

TO BE ON A WEAKENING TREND. HOWEVER...THERE VERY GOOD ACCELERATION

OF WINDS IN THE FIRST 2 KM. IN ADDITION...A FAIR AMOUNT OF

INSTABILITY CONTINUES TO BE INDICATED IN THE LOWEST LEVELS DURING

THE EARLY EVENING. IT/S A BIT EARLY TO RELY HEAVILY ON THESE

SPECIFICS BUT THEY DO PROVIDE INSIGHT ON THE SEVERE THREAT. GIVEN

ALL OF THIS IT DOES APPEAR THAT THERE WILL BE A GOOD CHANCE FOR

INITIATION OVER THE CENTRAL OR WESTERN CWA BY SUNDAY EVENING WITH

THE STRONG WIND PROFILES POINTING TO QUICK EVOLUTION TO A LINEAR

ORIENTATION. WITH SUCH STRONG WINDS IN THE LOW LEVELS IT WOULD NOT

TAKE MUCH TO GET DAMAGING WINDS TO THE SURFACE...WITH STRONG GUSTS

EXPECTED WITHOUT STORMS IF MIXING PANS OUT. AT THIS POINT AN

ISOLATED TORNADO THREAT DOES EXIST AT LEAST FOR A TIME GIVEN THE LOW

LEVEL WIND FIELDS AND POTENTIAL FOR GOOD LOW LEVEL INSTABILITY BUT

DIRECTIONAL SHEAR MAY BE A LIMITING FACTOR. OVERALL THERE IS A GOOD

THREAT BUT DO HAVE A FEW RESERVATIONS ON EXTENT OF DEVELOPMENT GIVEN

THE SURFACE AND UPPER LOW BEING DISPLACED TO THE NORTH AND WEAKENING

AND POTENTIAL FOR DRY SLOT TO SPREAD FURTHER EAST /THOUGH THIS MID

LEVEL DRYING COULD ALSO HELP THE THREAT/ AND ALSO THE ANTICYCLONIC

SIDE OF THE UPPER JET BEING OVERHEAD. ANY ACTIVITY SHOULD EXIT THE

AREA BY OR DURING THE OVERNIGHT HOURS.

[tornadotony]

The 12z NAM is significantly more intense and farther SW than previous runs, in line with the trends we've been seeing out on the plains over the past 24h.

[A-L-E-K]

The 12z NAM is significantly more intense and farther SW than previous runs, in line with the trends we've been seeing out on the plains over the past 24h.

not at all surprising.

[hm8]

There we go...

[Geos]

Prayers to everyone in the path of the high risk today, and to the storm chasers- they are going to need it.

Yes!

If your chasing stay safe and don't take unnecessary risks!

[TimChgo9]

There we go...

Just saw this a couple of minutes go. Not at all surprised. After looking things over today, I kind of figured the update would at the very least put NE IL in the SLGT. Could be an interesting day for someone.

My son is planning on chasing tonight, or tomorrow. Not sure where he is going to go, but he mentioned it yesterday.

[A-L-E-K]

I won't clutter the main svr thread but plains action seems to be congealing into a massive MCS awfully early, this kind of thing can play havoc with forecasts.

[tornadotony]

I won't clutter the main svr thread but plains action seems to be congealing into a massive MCS awfully early, this kind of thing can play havoc with forecasts.

Idk, those look mostly like semi-discrete supercells to me. I would certainly not say "massive MCS" yet.

[A-L-E-K]

Idk, those look mostly like semi-discrete supercells to me. I would certainly not say "massive MCS" yet.

sure, it just looks awfully cluttered for not even 2pm

EDIT: not by any means calling bust and mostly just wondering about potential outflow effect overnight.

[trapperman]

Regarding tomorrow... I can't believe how many times I have seen a setup like this in the last 5 years! It's getting to be almost a regular occurence. I should be able to step out on my patio about noon-1 tomorrow and watch cells literally explode to my southeast.

I remember vividly this day: http://www.spc.noaa.gov/products/outlook/archive/2007/day1otlk_20070607_1630.html

http://www.spc.noaa.gov/climo/reports/070607_rpts.html

I didn't know what a dryline was back then, we went from low 70s at 10am to 92 and sunny with a screaming southwest wind at 1pm. I remember watching the Lacrosse cell that destroyed everything with 6-7 inch hail blow up and go severe warned in less than 10 minutes. To this day I have never seen anything shoot up that fast. This was the cell that developed right on the nose of the strongest theta-e and where the winds backed the most and rode it all the way to Lake Michigan with the ridiculous long track ef3. Tomorrow is a little bit different but not much.

[SpartyOn]

Regarding tomorrow... I can't believe how many times I have seen a setup like this in the last 5 years! It's getting to be almost a regular occurence. I should be able to step out on my patio about noon-1 tomorrow and watch cells literally explode to my southeast.

I remember vividly this day: http://www.spc.noaa.gov/products/outlook/archive/2007/day1otlk_20070607_1630.html

http://www.spc.noaa.gov/climo/reports/070607_rpts.html

I didn't know what a dryline was back then, we went from low 70s at 10am to 92 and sunny with a screaming southwest wind at 1pm. I remember watching the Lacrosse cell that destroyed everything with 6-7 inch hail blow up and go severe warned in less than 10 minutes. To this day I have never seen anything shoot up that fast. This was the cell that developed right on the nose of the strongest theta-e and where the winds backed the most and rode it all the way to Lake Michigan with the ridiculous long track ef3. Tomorrow is a little bit different but not much.

This

You are a good poster.

[trapperman]

Actually I stand corrected, I got my cells mixed up lol. Went back and read a chase account from that day. But you get the idea.

[wisconsinwx]

Regarding tomorrow... I can't believe how many times I have seen a setup like this in the last 5 years! It's getting to be almost a regular occurence. I should be able to step out on my patio about noon-1 tomorrow and watch cells literally explode to my southeast.

I remember vividly this day: http://www.spc.noaa....70607_1630.html

http://www.spc.noaa....70607_rpts.html

I didn't know what a dryline was back then, we went from low 70s at 10am to 92 and sunny with a screaming southwest wind at 1pm. I remember watching the Lacrosse cell that destroyed everything with 6-7 inch hail blow up and go severe warned in less than 10 minutes. To this day I have never seen anything shoot up that fast. This was the cell that developed right on the nose of the strongest theta-e and where the winds backed the most and rode it all the way to Lake Michigan with the ridiculous long track ef3. Tomorrow is a little bit different but not much.

Gutsy comparison but can't deny that tomorrow has potential for much of Wisconsin, and maybe areas of Iowa and Minnesota just west of the Mississippi.

[trapperman]

I should back off on the comparison a little, lol. A little bit different with a 979mb (!!!) low in June and this setup. But it's just the same type setup 3 times in the last 5 years that blows me away...

[wisconsinwx]

I should back off on the comparison a little, lol. A little bit different with a 979mb (!!!) low in June and this setup. But it's just the same type setup 3 times in the last 5 years that blows me away...

I assume the third similar event you are referring to was April 10, 2011? That definitely does remind me of this one; same time of year, same day of the week, almost the exact same region it looks like, but this probably won't be quite on that level. It will be close, though, probably.

[Geos]

Weather Channel just mentioned Tor Con 6 for southern Wisconsin tomorrow!

A product of severe weather > severe rains tonight?

[BowMeHunter]

straight up big prob out

[trapperman]

I assume the third similar event you are referring to was April 10, 2011? That definitely does remind me of this one; same time of year, same day of the week, almost the exact same region it looks like, but this probably won't be quite on that level. It will be close, though, probably.

Yeah that was the other. Only difference last year was the 700mb low crapped the setup (thankfully I am not sorry to say) and the surface winds did not back. If they had...

Izzi had a stellar write up/presentation on the April 10 event last year and why it fizzled.

[tornadotony]

sure, it just looks awfully cluttered for not even 2pm

EDIT: not by any means calling bust and mostly just wondering about potential outflow effect overnight.

I wonder if you won't see leftover waves/boundaries from this maybe modulate the threat/increase it tomorrow.

[wisconsinwx]

Right now if I had to pick an ideal spot for tomorrow afternoon and evening if I were a chaser, LaCrosse and just to the east is looking like the prime spot right now, if ongoing convection doesn't muddle the situation.