Severe Weather Threat 7/15/24 - Midwest (Moderate Risk)

[Ledian]

Moderate risk for Eastern Iowa and Northern Illinois now

 

[James S]

The latest HRRR run is very intense

 

[kevinrock]

Brief spin up on the TOR possible SVR south of Rochester NY? Seemed to be a small cc drop with a peak on velocity just for a scan or 2

 

[Aaron Rider]

Brief spin up on the TOR possible SVR south of Rochester NY? Seemed to be a small cc drop with a peak on velocity just for a scan or 2

I was just sent this photo. I'm told it was near Mt Morris, which is on the Genesee just north of beautiful Letchworth Park and south of Rochester

 

[Taylor Campbell]

​ Forecast Discussion

SPC AC 152000 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Mon Jul 15 2024 Valid 152000Z - 161200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN IOWA...EXTREME SOUTHERN WISCONSIN...NORTHERN ILLINOIS...AND FAR NORTHWEST INDIANA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL PLAINS...AND ACROSS PARTS OF NEW YORK...PENNSYLVANIA AND FAR NORTHERN NEW JERSEY... ...SUMMARY... Severe thunderstorms are expected through this evening across portions of the Midwest, central High Plains, lower Great Lakes, and Arizona. The greatest potential for severe gusts is over eastern Iowa into Illinois and Indiana. ...Midwest... Both tornado and wind probabilities have been increased with the 20z update to 10 percent, and 45 percent SIG, respectively. Latest satellite imagery shows a modified outflow boundary draped across far eastern IA into northern IL. A very moist airmass with dewpoints in the mid/upper 70s amid strong heating is resulting in a corridor or strong to extreme instability across the region. Favorable vertical shear will support initial supercells, organizing into a bowing MCS with time as low-level flow remains orthogonal to the developing band of storms. The greatest severe wind potential is expected along the instability gradient in the vicinity of the remnant outflow boundary, extending from far eastern IA into extreme southern WI, northern IL, and far northwest IN into this evening. Widespread gusts of 60-70 mph are expected, with some gusts to 85 mph possible. Given favorable low-level shear, mesovortex tornadoes are likely along and near the apex of the developing bow late this afternoon into evening. For short term details on severe potential across this area, reference MCD 1630. ...NY/PA and the Central High Plains... No changes have been made with the 20z update. Reference Severe Thunderstorm Watch 538 regarding severe potential across NY/PA, and previous outlook discuss for more details. ..Leitman.. 07/15/2024 .PREV DISCUSSION... /ISSUED 1131 AM CDT Mon Jul 15 2024/ ...Midwest... A broad upper trough is digging southeastward across northwest Ontario and MN today, with strengthening mid level flow across much of the Midwest. Rapid thunderstorm development is expected to occur by mid afternoon across portions of WI/northeast IA, with storms tracking rapidly east-southeastward into northern IL and eventually parts of IN/Lower MI. 12z CAM guidance remains in general agreement that a large bowing complex is likely, although details of the corridor of greatest risk vary between solutions. Regardless, an active severe event is expected for this region, with the potential for isolated instances of significant damaging winds. ...NY/PA... Thunderstorms have begun to intensify over eastern Lake Erie, ahead of a strong upper trough and remnant MCVs. These storms are expected to increase in coverage and spread eastward through the day, possibly as far east as southeast NY and northern NJ by evening. Damaging winds and hail are the main concerns with these storms. ...Central High Plains... Scattered high-based thunderstorm development is expected this afternoon from western NE southward into parts of northeast CO and western KS. The combination of a deeply mixed boundary layer, sufficient CAPE, and 30+ knots of westerly mid level flow will pose a risk of locally damaging wind gusts in the stronger cells.

 

[eep]

 

[warneagle]

Derecho szn

 

[notsoencrypted]

Three tornado warnings on this system currently:

 

[notsoencrypted]

Lots of hail reports on MPING with this system, as well.

 

[warneagle]

There's also a random tornado warning up in the UP, basically in the middle of nowhere.

 

[TornadoFan]

Tornado watch up for large parts of Illinois and NW Indiana. 90/80 probs on severe winds.

 

[notsoencrypted]

Now even more parts of the system are tornado warned. The bit connected to the warning just south of Madison seems to have some pretty strong rotation on radar, and a good inflow notch?

 

[cniemczura]

268 wind reports? Wow - seems like a lot from the line in SW NY/Northern PA

 

[lake.effect]

Main bow taking dead aim at Chicago. Let's see if stays the course.

 

[Maxis_s]

Holy cow.

 

[Maxis_s]

Radar is losing its ming and showing a max gust of 200mph.

 

[Equus]

That is such an incredibly classic derecho presentation with the warm advection wing over Lake Michigan and the rear inflow jet behind.



Davenport sounding earlier was incredibly volatile; RAP has this over Chicago as the bow moves in. Still quite the impressive environment and plenty volatile enough for this to keep trucking on into the night.

 

[warneagle]

TORR including Plainfield.

 

[Maxis_s]

At least a half a dozen areas of rotation moving into the Chicago area.

 

[warneagle]

Almost 2.5 million people under a tornado warning, also includes the airport