Apr. 6-8 Severe Risks

[snowlover2]

8 minutes ago, IWXwx said:

Enhanced Risk Incoming

Quote

 
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1122 AM CDT TUE APR 07 2020  
 
VALID 071630Z - 081200Z  
 
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF  
SOUTHERN LOWER MICHIGAN...NORTHEAST INDIANA...AND NORTHERN OHIO...  
   
..SUMMARY  
 
SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON THROUGH TONIGHT  
ACROSS SOUTHERN PORTIONS OF THE GREAT LAKES REGION INTO THE OHIO  
VALLEY AND MID ATLANTIC. THE STRONGEST STORMS WILL POSE A THREAT  
FOR VERY LARGE HAIL, DAMAGING WIND GUSTS, AND A COUPLE OF TORNADOES.  
   
..SOUTHERN GREAT LAKES/OH VALLEY THIS EVENING INTO TONIGHT  
 
A PROGRESSIVE SHORTWAVE TROUGH IS NOTED IN WATER VAPOR IMAGERY OVER  
SD, WITH AN ASSOCIATED SURFACE COLD FRONT MOVING ACROSS MN/WI. THIS  
FRONT WILL MOVE INTO LOWER MI/SOUTHEAST WI BY MID-AFTERNOON, WHERE  
POCKETS OF STRONG HEATING AND LOW-LEVEL MOISTENING WILL RESULT IN  
MLCAPE VALUES OF 1000-2000 J/KG. 12Z MODEL GUIDANCE IS IN STRONG  
AGREEMENT THAT STORMS WILL FORM IN THE 3-5PM PERIOD ALONG THE FRONT  
AND TRACK RAPIDLY SOUTHEASTWARD INTO PARTS OF IN/OH. A COMBINATION  
OF STEEP MIDLEVEL LAPSE RATES AND STRONG DEEP-LAYER SHEAR WILL  
PROMOTE SUPERCELL STORM STRUCTURES CAPABLE OF VERY LARGE HAIL AND  
DAMAGING WINDS GUSTS. A TORNADO OR TWO IS POSSIBLE WITH EARLY  
STORMS, BUT FRONTAL FORCING SHOULD CONTRIBUTE TO UPSCALE  
ORGANIZATION DURING THE EARLY EVENING WITH INCREASING DAMAGING WIND  
RISK. THE CORRIDOR OF HIGHEST CONFIDENCE HAS BEEN UPGRADED TO ENH  
RISK. PRESENT INDICATIONS ARE THAT STORMS WILL PERSIST OVERNIGHT  
AND MOVE INTO PARTS OF WV/PA WHERE NOCTURNAL COOLING WILL SLOWLY  
DIMINISH THE SEVERE THREAT.

 

[geddyweather]

Aaaand there she is. 30% hatched for hail. Also leaves the 5% TOR along the OH/MI/IN border. 

Can't remember the last time we had such a widespread hail setup recently. 

[frostfern]

This is a pretty crazy setup for southern Lower Michigan.  Reed Timmer is in weeny mode.

[madwx]

almost full sunshine except for some altocumulus racing northeastward, dews up to 60 and temps near 70.  it feels nice to have spring weather with a legit chance at thunderstorms

[janetjanet998]

It will be interesting to see how  the lake created lower level instability void will be a factor as storms develop over eastern WI 

 

How long will they take to become  fully surfaced based again over MI

[geddyweather]

71/63 and Mostly Sunny imby, wind SSW at 12mph. Can I just say how AMAZING it is to have a clean warm sector for once? 

[Indystorm]

12 minutes ago, geddyweather said:

71/63 and Mostly Sunny imby, wind SSW at 12mph. Can I just say how AMAZING it is to have a clean warm sector for once? 

Yep, clean warm sector and EML cap, although not thermonuclear like sometimes in summer, might just be enough of a pressure cooker given these lapse rates to produce humungous hail when it breaks.   Stay safe my friends in nw Ohio, northern IN, and Chi town area.

[WestMichigan]

Just hit 70 here.  Lake shadow will probably limit things here, but no guarantee.

[sbnwx85]

9 minutes ago, Indystorm said:

Yep, clean warm sector and EML cap, although not thermonuclear like sometimes in summer, might just be enough of a pressure cooker given these lapse rates to produce humungous hail when it breaks.   Stay safe my friends in nw Ohio, northern IN, and Chi town area.

Biggest hail I've ever seen was golf ball size. Quite frankly, that's big enough. 

[Tim from Springfield (IL)]

Huge Day 2 update for tomorrow.  Slight risk basically extended along/south of I-74 in Illinois--and a hatched for large hail (albeit still 2/15/15 probs at this time).  Maybe at least an enhanced from NE MO/W IL to SE MO tomorrow.

https://www.spc.noaa.gov/products/outlook/day2otlk.html

 

 Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1236 PM CDT Tue Apr 07 2020

   Valid 081200Z - 091200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE
   MID MS VALLEY AND OVER PORTIONS OF CENTRAL TX...

   ...SUMMARY...
   Scattered strong to severe thunderstorms are possible over parts of
   central Texas Wednesday afternoon and the Middle Mississippi Valley
   on Wednesday evening and overnight. Large hail, damaging gusts, and
   perhaps a couple of tornadoes are the primary hazard.

   ...Synopsis...
   A split-flow pattern is forecast to be in place across the CONUS
   early Wednesday morning. Primary features within this pattern will
   be a northern-stream shortwave trough, which is expected to progress
   southeastward through the northern Plain and Mid/Upper MS Valley,
   and a southern-stream closed low, which is expected to slowly drift
   eastward over southern CA. More pertinent to the severe weather
   threat, a low-amplitude shortwave trough is expected to progress
   through the southern-stream over the southern Plains and Lower MS
   Valley. Confluence of the two streams will occur over the MS River
   Valley, with relatively strong flow aloft persisting, and then
   increasing late in the period, over the eastern CONUS. 

   Primary feature within the surface pattern will be a cold front that
   is expected to surge southeastward from the northern Plains/upper MS
   Valley into the central Plains/mid MS Valley by Wednesday evening,
   continuing eastward/southeastward through the southern Plains,
   Mid-South, and TN/OH Valleys by Thursday morning. Moist
   southwesterly low-level flow will advect high theta-e air into the
   mid MS Valley ahead of this front while maintaining the moist air
   mass already in place from east TX through the Southeast. 

   ...Mid MS Valley into portions of the OH/TN Valleys...
   A somewhat broad area of Slight-risk equivalent severe weather
   probabilities will exist over much of the region Wednesday. This is
   due to different model depictions of low-level moisture return,  cap
   strength, and frontal timing as well as at least some modest risk
   for pre-frontal development.  The general expectation is for
   thunderstorms to initialize along the front during the afternoon and
   then push southeastward throughout the evening. Initial storm mode
   will likely be cellular, with the thermodynamic and kinematic
   profiles supporting the threat for very large hail. Given the linear
   forcing, a quick linear transition is anticipated, with the severe
   threat also transitioning from hail to damaging wind gusts. Tornado
   threat will be non-zero, but relatively weak and veered low-level
   flow suggests low potential for development.  

   The overall threat appears highest across northeast MO and adjacent
   western IL southeastward into southern IL and southeast MO although
   not high enough to delineate higher probabilities with this outlook.
   An upgrade may be needed in subsequent outlooks if a corridor of
   higher risk appears more likely. A more conditional severe threat
   exists south in AR, where frontal timing will be less favorable but
   more moist low-level conditions will exist. Any storm within this
   environment would likely be severe.  

   ...TX Hill Country/Central TX...
   Low-amplitude, southern-stream shortwave trough mentioned in the
   synopsis will likely provide enough ascent to foster thunderstorm
   initiation over the region during the afternoon. Thermodynamic
   environment will be characterized by ample low-level moisture (i.e.
   dewpoints in the upper 60s/low 70s) beneath steep mid-level lapse
   rates. Resulting strong buoyancy coupled with deep-layer shear
   around 40-50 kt should be more than supportive for organized storm
   structures. Initial threat will be large hail, with some instances
   of very large hail possible. The initially cellular mode will likely
   transition more linear quickly, with the primary threat then
   transitioning to damaging downburst winds resulting from
   water-loaded downdrafts. An initial supercell mode will also result
   in a low-probability threat for an isolated tornado, although
   low-level winds do not appear overly favorable for low-level
   rotation.

   ...Southeast into the Mid-Atlantic...
   Residual boundaries from antecedent showers and thunderstorms will
   likely act as an impetus for additional convective initiation
   Wednesday afternoon. Relatively deep and strong northwesterly flow
   aloft would likely support organized storm structures and an
   attendant severe weather threat. Mesoscale nature of this threat
   precludes any corridors of higher potential on this outlook, but
   updgrades may be needed in following outlooks once mesoscale
   features become more predictable.

   ..Mosier.. 04/07/2020

[frostfern]

16 minutes ago, sbnwx85 said:

Biggest hail I've ever seen was golf ball size. Quite frankly, that's big enough. 

I saw 2.25" stones melting on the ground while chasing behind a storm here in Michigan.  May 2013.  Don't know if that counts.  I couldn't afford to total my car.  As for falling hail, I've seen quarter or slightly larger a few times....  from safely indoors.

[Spartan77]

26 minutes ago, sbnwx85 said:

Biggest hail I've ever seen was golf ball size. Quite frankly, that's big enough. 

When I lived in Colorado Springs there was a hail storm that came off the mountains in August of 2018. I was pumping gas when baseball hail started falling. Don't ever want see that again. Literally punched holes in all the cars.

[OHweather]

Heh, for once the morning convection didn't do anything it wasn't supposed to do...

Definitely a few question marks remaining...

Not sure on if there's initiation in time for N IL or not...the HRRR barely breaks the cap, the NAM doesn't but is close, most of the CAMs just start developing storms over NE IL before they move ESE. The frontal circulation itself should intensify a bit soon as it pushes into an area that's seen better heating over IL/SE WI, and the ascent ahead of the mid-level impulse just begins overspreading the front before it clears NE IL.  I think a storm or two likely develops over N IL (like, 60/40 for one or two cells)...not really a tornado risk, but could be supercellular with a hail risk.  It's a highly conditional, but perhaps locally significant hail threat.

It seems that last night's models that insisted on initiation over the southern Great Lakes were on the right track, and the lack of unexpected ongoing convection certainly adds confidence in sufficient destabilization through the rest of the afternoon into the evening ahead of the cold front.  The low-level flow begins to accelerate this evening, though aside from perhaps local turning ahead of the weak surface low over parts of southern MI and perhaps immediately adjacent NW OH, remains fairly veered with marginal helicity.  That said, there may be enough of a combination of low LCLs and SRH in that vicinity, assuming the winds do back a bit, for a short-duration tornado risk.  I can't really argue with the 5% risk as it's placed. 

The hail risk is fairly straight-forward initially, as the speed shear will favor mid-level updraft rotation in an environment with very steep mid-level lapse rates and fairly low wet bulb zeroes.  Any discrete or semi-discrete cells will be prone to severe hail, with over 2" quite possible with any supercells.  The only question is, how quickly does upscale growth occur as activity starts spreading E/SE across northern and central IN and into much of OH?  This will determine when we go from an impressive hail risk to more of a wind risk.  The front gradually becomes sharper this evening as the low intensifies and the front surges southeast, which favors upscale growth...and there is some large-scale ascent as the mid-level impulse/speed-max moves overhead.  However, with some capping and shear vectors somewhat orthogonal to the front, it may not be immediate. 

While most CAMs generally show fast upscale growth, not all do immediately (in particular, the HRRR and NSSL WRF look somewhat cellular longer).  There will undoubtedly be gradual upscale growth and a transition from a primarily hail threat to more of a damaging wind risk, but whether it takes a couple of hours or a few hours I'm not quite sure.  I'm still curious to see if the relatively stable low-levels temper the wind risk at all.  The EML will promote strong downdrafts, and upscale growth would likely result in enough clustering of those downdrafts to punch through the inversion, but most models do maintain at least some inversion tonight beneath the EML over IN/OH...especially farther NE where the surface is cooler.  I'm sure an organized bowing segment would punch through it, but widespread damaging winds may be asking a lot otherwise.

Definitely will be interesting to watch play out and I think the SPC outlook is fair as it is given some of the remaining uncertainty, but also the parameters that are in place.

[LansingWeather]

29 minutes ago, frostfern said:

I saw 2.25" stones melting on the ground while chasing behind a storm here in Michigan.  May 2013.  Don't know if that counts.  I couldn't afford to total my car.  As for falling hail, I've seen quarter or slightly larger a few times....  from safely indoors.

Was that the year of the EF-3 in Dexter?

My friend and I went out chasing hail cores, ended up being right at the formation of the TOR which moved over Dexter, AFAIK I am the only one who go tthe formation of that TOR on video. Was a huge highlight of my adventures.

[frostfern]

24 minutes ago, LansingWeather said:

Was that the year of the EF-3 in Dexter?

My friend and I went out chasing hail cores, ended up being right at the formation of the TOR which moved over Dexter, AFAIK I am the only one who go tthe formation of that TOR on video. Was a huge highlight of my adventures.

No.  That was the year before (2012).  I didn't chase anything that day.  May 20, 2013 there was a small cell that developed in southern Newaygo county then moved into Mecosta county.  I just kind of watched it go by to the north then drove in behind to look for hail on the ground.  You were lucky to get that.  I've never seen a real tornado, just waterspouts.

[frostfern]

25 minutes ago, LansingWeather said:

Was that the year of the EF-3 in Dexter?

My friend and I went out chasing hail cores, ended up being right at the formation of the TOR which moved over Dexter, AFAIK I am the only one who go tthe formation of that TOR on video. Was a huge highlight of my adventures.

I don't know how you chase hail.  It seems if you get in front of a hail core it's pretty damn hard to find shelter.  A gas station canopy is usually a really bad idea and an underpass is even worse.  One time I left my car under the gas station canopy and went in the store.  Wasn't expecting the car to be spared if golfballs did fall.  That time it didn't get bigger than nickel size but I was kind of worried based on the radar and didn't think I could drive away fast enough since it was more of a bow than a cell.

[Chicago Storm]

Think we eventually see initiation somewhere in the NE IA/SW WI/NW IL area. The front is more NE-SW oriented currently, instead of N-S....and will becoming more ENE-WSW oriented with time. That will likely lead to a positive in eroding the cap, with some "CAA" occurring aloft moving into the aforementioned area, which looks to overlap the front due to its previously mentioned orientation. Add in the main disturbance and jet streak will be nosing into that area shortly as well. Seems to be a nice spot to watch for starters. Already seeing a nice/healthy/agitated CU field across this area as well.

Probably will have some initiation in other areas as well, but that is one area that sticks out for now.

[LansingWeather]

17 minutes ago, frostfern said:

I don't know how you chase hail.  It seems if you get in front of a hail core it's pretty damn hard to find shelter.  A gas station canopy is usually a really bad idea and an underpass is even worse.  One time I left my car under the gas station canopy and went in the store.  Wasn't expecting the car to be spared if golfballs did fall.  That time it didn't get bigger than nickel size but I was kind of worried based on the radar and didn't think I could drive away fast enough since it was more of a bow than a cell.

I chase them in beater cars. Follow the high VIL rating. We had actually intercepted 3 storms with ~quarter sized hail. The last one we were getting hailed on when the TORWARN was issued for what would become the Dexter tornado.

This was just to the NE of Jackson and south of Fowlerville. Not sure if it was in Jackson or Washtenaw county.

[yoda]

Mesoscale Discussion 0295
   NWS Storm Prediction Center Norman OK
   0306 PM CDT Tue Apr 07 2020

   Areas affected...eastern WI...northern IL/IN and western MI

   Concerning...Severe potential...Watch likely 

   Valid 072006Z - 072200Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Isolated elevated thunderstorms may produce large hail
   across eastern WI near Green Bay over the next hour. Additional
   storms are expected to develop further south over the next couple of
   hours, posing a threat for damaging wind gusts, large hail and
   perhaps a couple of tornadoes, while spreading eastward across
   southern Lower Michigan/northern Indiana this evening.

   DISCUSSION...Isolated elevated thunderstorms have developed north of
   the warm front. Very steep midlevel lapse rates and strong shear
   will support large hail potential in this elevated convection.

   Further south, strong warm advection is resulting in modest
   increases in boundary layer moisture south of the warm front, with
   dewpoints mainly in the mid-50s to near 60 F south of the boundary.
   Very steep lapse rates atop a weakening capping inversion and strong
   vertical shear will favor semi-discrete cells capable of large hail
   initially. Strong heating into the low and mid 70s is aiding in
   rapid erosion of this cap. As a result, expect isolated to
   widely-scattered surface-based thunderstorm development over the
   next couple of hours across southeast WI. In addition to damaging
   wind and large hail, a couple of tornadoes are possible, especially
   in the vicinity of the warm front where low level shear is enhanced.


   With time and as frontal forcing increases this evening in
   conjunction with a low level jet, convection will likely grow
   upscale into one or more bowing segments as storms shift east over
   Lake Michigan and into southern Lower Michigan toward 00z. This will
   increase potential for damaging winds across parts of southern Lower
   Michigan into northern Indiana this evening.

   ..Leitman/Hart.. 04/07/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...DTX...APX...IWX...GRR...GRB...LOT...MKX...

[yoda]

https://www.spc.noaa.gov/products/md/md0295.html

[frostfern]

I see initiation just north of MKX.  Tops already at 40k ft.  

[frostfern]

This pocket of cells is just barely north of the surface warm front.  Have to see what it does when it moves out over the lake.

[Sydney Claridge]

5 minutes ago, frostfern said:

I see initiation just north of MKX.  Tops already at 40k ft.  

And so it looks like things are starting to ramp up.  Shouldn't be too long before it goes severe at this rate.  Temperatures just to the south are in the mid-70s, although the prior poster said storms are just north of the warm front.

[geddyweather]

SPC thinking Srn MI has the best chance for discrete activity, and I tend to agree with them. Thinking the unidirectional wind profile plus rapid upscale development pushes this linear earlier than expected. 

[frostfern]

2 minutes ago, BrandonC_TX said:

And so it looks like things are starting to ramp up.  Shouldn't be too long before it goes severe at this rate.  Temperatures just to the south are in the mid-70s, although the prior poster said storms are just north of the warm front.

Barely north.  The boundary seems to be directly over MKX at the moment.  

[Sydney Claridge]

West Bend and Port Washington, WI are now under a severe thunderstorm warning.  Surface-based activity could be possible I guess, given the proximity of the warm front and plentiful SBCAPE, but it won't be too much longer before this storm goes over Lake Michigan (and becomes elevated as a result).

West Bend, WI seems to be reporting 73 degrees as well.  Port Washington is at 54 degrees, so the storm will have to become elevated just before it reaches the lakeshore I guess; there may be a lake-breeze boundary near I-43 around Grafton given temperature differentials there.  Further south, the warm air is reaching all the way to the lakeshore.

EDIT: I'm also watching that hook near Jackson, WI as well.  It does not look to be anything too concerning at the moment (it seems to be broad/weak rotation).

EDIT 2: another severe thunderstorm warning has gone up in southeastern Ohio as well, with a storm approaching the I-77 corridor.

[Chicago Storm]

1 hour ago, Chicago Storm said:

Think we eventually see initiation somewhere in the NE IA/SW WI/NW IL area. The front is more NE-SW oriented currently, instead of N-S....and will becoming more ENE-WSW oriented with time. That will likely lead to a positive in eroding the cap, with some "CAA" occurring aloft moving into the aforementioned area, which looks to overlap the front due to its previously mentioned orientation. Add in the main disturbance and jet streak will be nosing into that area shortly as well. Seems to be a nice spot to watch for starters. Already seeing a nice/healthy/agitated CU field across this area as well.

Probably will have some initiation in other areas as well, but that is one area that sticks out for now.

Significant initiation attempts occurring in the mentioned area now, just NW of DBQ.

[the ghost of leroy]

What a tiny and pathetic discussion. I’m surprised that I rolled in here this late in the day and things are this quiet. 

[Chicago Storm]

Several 2-2.50" hail reports from that sup that moved north of MKE a bit ago.

[Indystorm]

Gotta get that 700 mb cap eroded in nw IL which I believe will happen in the not too distant future and then we'll be seeing some storms.