May 19-22 Severe Weather Threat

[Stebo]

It looks like that run sends an outflow boundary through the area early in the day and uses that as an excuse to keep redevelopment at bay. Looking at current radar, there is a boundary showing up quite clearly on DVN though it's running a bit ahead of where the model had it at this time. I'm curious to see how they handle the 6z outlook.

Yeah I am not sure, I don't think that boundary would kill everything for the rest of the day, that would be shocking tbh.

[turtlehurricane]

Winning

 

[Stebo]

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0100 AM CDT MON MAY 20 2013

VALID 201200Z - 211200Z

 

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF OK/SOUTHEAST OK/SOUTHERN MO/NORTHWEST AR...

 

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SOUTHERN PLAINS TO THE MIDWEST/GREAT LAKES REGION...

 

...SYNOPSIS... YET ANOTHER ACTIVE/RELATIVELY WIDESPREAD SEVERE WEATHER DAY IS LIKELY ACROSS PORTIONS OF THE SOUTHERN PLAINS TO MIDWEST TODAY AND TONIGHT. A PROMINENT CENTRAL CONUS UPPER TROUGH WILL CONTINUE A GENERAL EASTWARD ADVANCEMENT THROUGH TONIGHT...WITH A LEAD/CLOSED UPPER LOW PIVOTING OVER THE DAKOTAS/UPPER MIDWEST. A SOUTHERN STREAM SHORTWAVE TROUGH/MODERATELY STRONG POLAR JET WILL EJECT EAST-NORTHEASTWARD OVER THE SOUTHERN ROCKIES TO THE SOUTHERN PLAINS/OZARKS...WITH SEVERE TSTMS INCREASINGLY LIKELY BY PEAK HEATING AND CONTINUING INTO TONIGHT.

 

MEANWHILE...A LINGERING UPPER LOW OVER THE COASTAL SOUTHEAST STATES WILL CONTRIBUTE TO ANOTHER DAY OF WIDELY SCATTERED TO SCATTERED TSTMS OVER THE REGION...SOME OF WHICH MAY AGAIN BE STRONG OR SEVERE.

 

...SOUTHERN PLAINS/OZARKS/MIDDLE MS VALLEY... UNDER THE INFLUENCE OF BROAD/MODERATELY STRONG CYCLONIC FLOW ALOFT...THE AIRMASS IS EXPECTED TO AGAIN BECOME QUITE UNSTABLE ACROSS MUCH OF THE REGION BY THE AFTERNOON BENEATH AN ELEVATED MIXED LAYER EXTENDING ACROSS THE SOUTHERN PLAINS INTO PARTS OF THE OZARKS AND LOWER/MIDDLE MS VALLEY. MIDDLE/UPPER 60S AND SOME LOWER 70S F SURFACE DEWPOINTS WILL BE QUITE COMMON WITHIN A SPATIALLY BROAD WARM SECTOR AHEAD OF A COLD FRONT EXTENDING FROM AN EASTERN DAKOTAS/MN SURFACE LOW SOUTHWESTWARD TO NEAR THE KANSAS CITY AREA/EASTERN KS AND WESTERN OK...AND AHEAD OF A DRYLINE EXTENDING FROM SOUTHWEST OK SOUTHWARD INTO WESTERN NORTH TX/WEST-CENTRAL TX.

 

OUTFLOW REMNANTS FROM OVERNIGHT/EARLY DAY CONVECTION ACROSS THE OZARKS/MIDDLE MS VALLEY WILL LIKELY BE A FACTOR INTO THIS AFTERNOON...POSSIBLY AS A RENEWED FOCUS FOR SEVERE TSTM REDEVELOPMENT...WITH THE MOST AGGRESSIVE HEATING/DESTABILIZATION ON THE WESTERN FRINGES OF THIS ACTIVITY ACROSS THE SOUTHERN PLAINS AND PERHAPS LOWER MO VALLEY JUST AHEAD OF THE TRUE SYNOPTIC COLD FRONT. SEVERE TSTMS CAPABLE OF HAIL/DAMAGING WINDS AND SOME TORNADO THREAT WILL BE POSSIBLE ALONG THIS FRONTAL ZONE ACROSS EASTERN KS/NORTHERN MO INTO THE UPPER MS VALLEY...WITH A PERSISTENT/EAST-NORTHEASTWARD DEVELOPING SEVERE THREAT INTO THE EVENING.

 

THAT SAID...THE MOST INTENSE/MOST PROBABLE SEVERE STORMS ARE ANTICIPATED A BIT FARTHER SOUTH-SOUTHWEST ACROSS THE SOUTHERN PLAINS/OZARKS BY MID/LATE AFTERNOON INTO TONIGHT. THIS INCLUDES A PORTION OF THE SYNOPTIC FRONT AND/OR OUTFLOW ACROSS FAR SOUTHEAST KS/SOUTHWEST MO...AREAS ROUGHLY PARALLEL AND NORTHWEST OF THE I-44 CORRIDOR...BUT ESPECIALLY SOUTH-SOUTHWESTWARD INTO MUCH OF THE MIDDLE PART OF OK /POTENTIALLY INCLUDING OKC METRO/...TO NEAR THE HEAT-AIDED SURFACE LOW AND SOUTHWARD-EXTENDING SHARPENING DRYLINE INTO THE WESTERN PART OF NORTH TX/WEST-CENTRAL TX. IN THIS CORRIDOR...MLCAPE VALUES ARE LIKELY TO EXCEED 2500-3000 J/KG BY AFTERNOON WITHIN THE WARM SECTOR ACROSS OK AND WEST-CENTRAL/NORTH-CENTRAL TX...AND PERHAPS INTO PARTS OF SOUTHEAST KS AND MO. WITH BROAD/MODERATELY STRONG CYCLONIC MID-HIGH LEVEL FLOW /50+ KT AT 500 MB/ OVER THE REGION...40-50 KT OF EFFECTIVE SHEAR WILL COINCIDE WITH THE MAJORITY OF THE EFFECTIVE FRONTAL ZONE AND/OR DRYLINE ACROSS OK/EXTREME NORTH TX INTO SOUTHEAST KS AND THE OZARKS.

 

THE DEGREE OF SHEAR AND MOISTURE/INSTABILITY WITHIN THE WARM SECTOR WILL FAVOR SCATTERED TO NUMEROUS SUPERCELL STRUCTURES...AT LEAST THROUGH MID-EVENING OF THE CONVECTIVE CYCLE. VERY LARGE HAIL AND TORNADOES ARE POSSIBLE WITH SUPERCELLS...WITH AN EARLY EVENING PEAK TORNADO THREAT /PERHAPS A COUPLE OF STRONG TORNADOES/ BOOSTED BY A NOCTURNALLY STRENGTHENING SOUTHERLY LOW LEVEL JET AND ASSOCIATED LOW-LEVEL HODOGRAPH ENLARGEMENT. ULTIMATELY...ONE OR MORE MCS/S SHOULD EVOLVE ALONG NOSE OF STRENGTHENING LOW LEVEL JET OVER OK AND EVENTUALLY INTO THE OZARKS BY LATE EVENING/OVERNIGHT. DAMAGING WIND POTENTIAL WILL LIKELY INCREASE IN ASSOCIATION WITH MCS DEVELOPMENT THIS EVENING....ASIDE FROM A SEVERE HAIL AND CONTINUED TORNADO RISK...BUT ON AN INCREASINGLY ISOLATED BASIS INTO LATE EVENING/OVERNIGHT.

 

...UPPER MIDWEST/GREAT LAKES... MID-LEVEL SHORTWAVE TROUGH/SPEED MAX WILL PIVOT NORTHEASTWARD OVER THE UPPER MIDWEST/UPPER MS VALLEY DURING THE AFTERNOON...WITH ASSOCIATED FORCING FOR ASCENT OVERSPREADING A RELATIVELY MOIST/UNSTABLE BOUNDARY LAYER TO THE SOUTH OF A WARM FRONT EXTENDING FROM THE EASTERN DAKOTAS/MN SURFACE LOW EASTWARD TO NORTHERN PORTIONS OF THE GREAT LAKES REGION. TWO GENERAL SCENARIOS FOR SEVERE TSTM DEVELOPMENT SEEM PROBABLE THIS AFTERNOON. ONE BEING PARTS OF IA/UPPER MS VALLEY ON THE EASTERN PERIPHERY OF THE UPPER LOW AND UPPER JET EXIT REGION AS IT COINCIDES WITH THE SYNOPTIC FRONT. MEANWHILE...FARTHER EAST...PROPAGATION OF REMNANT OUTFLOW /EVEN SUBTLE REMNANTS INTO AFTERNOON/ ARE A PLAUSIBLE INFLUENCE FOR RENEWED TSTM DEVELOPMENT INTO A VERY UNSTABLE AIRMASS ACROSS THE GREAT LAKES REGION. OVERALL...THIS INCLUDES POTENTIAL FOR SOME SUPERCELLS ASIDE FROM SUSTAINED LINEAR STRUCTURES...WITH BOUTS OF DAMAGING WINDS/SEVERE HAIL AND A COUPLE OF TORNADOES ALL POSSIBLE ACROSS THE REGION.

 

...SOUTHEAST STATES/FL... THE AIRMASS SHOULD STRONGLY DESTABILIZE THIS AFTERNOON...ESPECIALLY IN AREAS NEAR AND WEST-SOUTHWEST OF THE APPALACHIANS...WITH DIURNALLY INCREASING/INTENSIFYING TSTM DEVELOPMENT FURTHER AIDED BY A PERSISTENT UPPER LOW OVER THE REGION. BOUTS OF DAMAGING WINDS AND SOME HAIL WILL BE POSSIBLE AS STORMS GENERALLY DRIFT SOUTHWARD THROUGH THE AFTERNOON/EARLY EVENING HOURS.

 

 

 

 

[Torchageddon]

For those in SW Ontario wondering, it does extend into that part of the Provence before winding down around midnight not before making it to the Kitchener/Waterloo area. 

 

This model absolutely nailed the convection today both in mode and location. I have pretty high confidence that tomorrow will play out like this model among others show for Michigan.

 

What's funny is as I was reading the top of your post, I was about to reply and ask what it will be like for SW Ontario until I scrolled down to see that you covered it  . Midnight seems pretty late, would rather storms take advantage of daytime heating and get pop up cells during the day. The airmass last night was like soup, dense patches of fog everywhere in an unusual fashion.

[A-L-E-K]

looks like at least some minor crapvection this morning (no shocker there)...still not bullish on today. 

[hawkeye_wx]

Wind gusted hard here around 11pm last night, at least 60 mph.  We quickly lost power, although the lights stayed on a couple blocks away.  One of the neighbor's lost a big limb off one of his trees, but other than that it's just a lot of small debris scattered around.  My garden made it through unscathed.

[Gilbertfly]

DVN update...

 

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
648 AM CDT MON MAY 20 2013

.UPDATE...
ISSUED AT 624 AM CDT MON MAY 20 2013

THE NOCTURNAL MCS WILL CONTINUE TO SLOWLY DISSIPATE THROUGH MID
MORNING AND MOST OF THE AREA SHOULD SEE DRY CONDITIONS THROUGH MID
DAY. AFTER MID DAY NEW CONVECTION WILL RAPIDLY DEVELOP ONCE
CONVECTIVE TEMPERATURE IS ACHIEVED.

DATA INDICATES DISCRETE CELLS WILL INITIALLY DEVELOP THAT EVOLVE
INTO ONE OR MORE LINEAR MCS EVENTS BY EARLY EVENING AND WILL
CONTINUE INTO THE LATE EVENING.

THERE IS STILL A GOOD POTENTIAL FOR SEVERE STORMS THIS AFTERNOON
AND EVENING. THE MORNING UA FLIGHT THAT IS UNDERWAY SHOWS
CONSIDERABLE SPEED SHEAR UP THROUGH 2KFT AGL. THE KEY TO
EVERYTHING WILL BE HOW THE UPPER JET ROTATING UP FROM THE SOUTHERN
PLAINS WILL INTERACT WITH LOWER LEVEL FEATURES.

BASED ON THE PROGGED PLACEMENT OF THE JET STRUCTURE AND
INSTABILITY AXIS...SEVERE STORMS APPEAR TO BE PROBABLE DURING THE
AFTERNOON AND EVENING HOURS. IF SEVERE STORMS OCCUR...DAMAGING
WINDS AND LARGE HAIL ARE A GIVEN. BASED ON PROGGED SHEAR PROFILES
AND BUOYANCY WITH INPUT FROM THE IN PROGRESS 12Z UA FLIGHT...
TORNADOES ARE ALSO POSSIBLE. IF TORNADOES DEVELOP WITH THE
DISCRETE CELLS...SIGNIFICANT TORNADOES MAY BE POSSIBLE.   ..08..

 

[Powerball]

Perfect!!!

 

[Stebo]

Perfect!!!

 

Yeah looks pretty good to me, lots of sunshine, should percolate nicely today, I also see several bands that could be the forcing mechanism for convection later this afternoon. 

[wisconsinwx]

Perfect!!!

 

 

This is complete and utter BS, especially after Chicago and Milwaukee did not get really a drop of rain last night.  I can deal with leftover rain showers and thunderstorms because at least you get precip, but thick cloud debris with no precip is the worst.

[RCNYILWX]

Perfect!!!

 

 

This is complete and utter BS, especially after Chicago and Milwaukee did not get really a drop of rain last night.  I can deal with leftover rain showers and thunderstorms because at least you get precip, but thick cloud debris with no precip is the worst.

It's 9am. Plenty of time for the debris clouds to clear enough to destabilize.

Sent from my SCH-I535 using Tapatalk 2

[Stebo]

It's 9am. Plenty of time for the debris clouds to clear enough to destabilize.

Sent from my SCH-I535 2

 

Some people never learn lol

[A-L-E-K]

This is complete and utter BS, especially after Chicago and Milwaukee did not get really a drop of rain last night.  I can deal with leftover rain showers and thunderstorms because at least you get precip, but thick cloud debris with no precip is the worst.

 

 

there really isn't that much debris

[Stebo]

there really isn't that much debris

Yeah and what is out there is incredibly thin and negligible.

[Gilbertfly]

It's 9am. Plenty of time for the debris clouds to clear enough to destabilize.

Sent from my SCH-I535  2

yup....I can still feel the heat from the suns rays through the debris warming things slightly already....definitely more of an unstable feel to the air then during other leftover MCS stabilizing scenario mornings....slight risk seems about right for the moment still

[A-L-E-K]

Yeah and what is out there is incredibly thin and negligible.

 

looks like all systems go for ample clusters in the region but i'm not overwhelmed by the supercell prospects this far northeast

[Gilbertfly]

looks like all systems go for ample clusters in the region but i'm not overwhelmed by the supercell prospects this far northeast

clearing for us looks timed well with the cap breaking apart....boundaries should show themselves...I agree with your thoughts on the sup cell threat up here...prolly similar to what central/northern Iowa saw yesterday for us today....perhaps some rotation here and there

[wisconsinwx]

It's 9am. Plenty of time for the debris clouds to clear enough to destabilize.

Sent from my SCH-I535 2

 

I'm not saying the day is shot, but I've seen this movie enough.

[frostfern]

I'm feeling good about Michigan today.  It is positively soupy for May (67 degree dewpoint) and already getting warm.  Anything that pops up has the potential to become a hailer and wet microbursts will definitely be possible given the soundings.  Areas west of US 131 might miss out this afternoon due to being west of the lake breeze (the typical problem) but there will probably be another MCS tonight that at least gives everyone rain.

[A-L-E-K]

I'm not saying the day is shot, but I've seen this movie enough.

 

 

debris really doesn't look like an isssue at all, the current canpoy is thinning nicely...it's not like we're dealing with at a large MCS/cold pool pusing into Western Illinois.  1500-2000 sbcape should be widespread by 16-18z.

[RCNYILWX]

Yeah and what is out there is incredibly thin and negligible.

looks like all systems go for ample clusters in the region but i'm not overwhelmed by the supercell prospects this far northeast

Deep layer shear will be sufficient to get some supes but we'll probably have mixed mode. Great point about the already thinning cloud debris. If anything, the presence of scattered leftover debris can serve as differential heating boundaries that provide a focus for convection.

Sent from my SCH-I535 using Tapatalk 2

[wisconsinwx]

Deep layer shear will be sufficient to get some supes.

Sent from my SCH-I535 2

 

What do you think are the most likely triggers?  LOT thinks a wave moving N/NE into C Illinois this afternoon, but then there are also some leftover boundaries from last night's convection.

[Gilbertfly]

Deep layer shear will be sufficient to get some supes.

Sent from my SCH-I535  2

temp rose like 7 or 8 degrees in like 15 minutes here after that thicker deck rolled through....filtered sunshine warming things nicely

[frostfern]

Deep layer shear will be sufficient to get some supes.

Sent from my SCH-I535 2

 

I think so.  I think hail and downbursts will be the biggest threat here over MI.  The tornado threat is a bit of a stretch here but when is it not.

[Harry Perry]

Getting a little excited here in SWMI...

Sun is out, dewpoints are pushing 70, and the HRRR is getting me very excited for whats to come later on this afternoon.

[RCNYILWX]

What do you think are the most likely triggers?  LOT thinks a wave moving N/NE into C Illinois this afternoon, but then there are also some leftover boundaries from last night's convection.

Since convective temperature on the 12z DVN sounding is 84 degrees, we should pretty easily become uncapped to surface based and mix layered parcels this afternoon, so any (even subtle) shortwave energy rounding the upper trough, leftover boundaries or differential heating boundaries could serve as triggers. The RAP seems to be keying on positive vorticity advection from a midlevel vort lifting northeast from Missouri early-mid afternoon.

[wisconsinwx]

Lol, Milwaukee and Racine already feeling a lake breeze, SE winds and dropping temps at MKE since the last observation.

[A-L-E-K]

Lol, Milwaukee and Racine already feeling a lake breeze, SE winds and dropping temps at MKE since the last observation.

 

 

sucks for you guys, i'm becoming increasingly bullish, very humid out here in the loop.

[RCNYILWX]

sucks for you guys, i'm becoming increasingly bullish, very humid out here in the loop.

Interestingly, the RAP turns a lake breeze even for Chicago, but I'm thinking that would be more likely to only affect northeastern Lake County. We'll see how the HRRR does, the 13z run has a cluster headed for Chicagoland at 21-23z. It actually did very well with the storms yesterday evening.

 

[A-L-E-K]

Interestingly, the RAP turns a lake breeze even for Chicago, but I'm thinking that would be more likely to only affect northeastern Lake County. We'll see how the HRRR does, the 13z run has a cluster headed for Chicagoland at 21-23z. It actually did very well with the storms yesterday evening.

 

In some ways, a lake breeze is almost inevitable if we're going to have any kind of backed flow but the fetch should be small enough this far south that it shouldn't be a total deal breaker.