March 26-28 Severe Threat

[twistingtornado]

5 minutes ago, andyhb said:

Look at the VWP from DMX before deciding that.

Wasn't talking about Iowa, was talking about the area highlighted for long track tornadoes in Missouri in Mesoscale Discussion 250. Currently isn't in a watch.

[janetjanet998]

20Z 
JEFFERSON CITY FAIR      76  64  66 S22G35 

[Indystorm]

3 minutes ago, geddyweather said:

20z gonna be late. Weeeeeee.

Meanwhile, interesting looking cell trying to take shape NW of Indy along the warm front. Getting to the time of the day where wind profiles in this area were going to start growing more favorable IIRC. 

That cell is just on the eastern edge of the insane helicity in Illinois within the PDS watch area.

[WeatherMonger]

69/67 KSPI

[snowlover2]

Moderate again maintained.

[yoda]

Mod risk remains at 20z

[WeatherMonger]

No High Risk

[snowlover2]

Quote

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0306 PM CDT SAT MAR 28 2020  
 
VALID 282000Z - 291200Z  
 
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF  
NORTHERN/CENTRAL IL AND FAR EASTERN IA...  
   
..SUMMARY  
 
A SEVERE-WEATHER OUTBREAK IS EXPECTED FOR PORTIONS OF THE MIDWEST  
THIS AFTERNOON AND EVENING. A FEW LONG-TRACKED, SIGNIFICANT  
TORNADOES ARE POSSIBLE, ALONG WITH LARGE, DAMAGING HAIL AND SEVERE  
GUSTS.  
   
..20Z UPDATE  
 
NUMEROUS SHOWERS AND THUNDERSTORMS EARLIER THIS MORNING AND EARLY  
AFTERNOON HAVE HAMPERED SUBSTANTIAL DESTABILIZATION ACROSS PARTS OF  
IL AND EASTERN IA SO FAR TODAY. EVEN SO, INSTABILITY IS STILL  
FORECAST TO GRADUALLY INCREASE THROUGH THE REMAINDER OF THE  
AFTERNOON INTO THIS EVENING AS MODEST DIURNAL HEATING OCCURS IN  
TANDEM WITH MOISTENING LOW LEVELS AND COOLING MID-LEVEL TEMPERATURES  
WITH THE APPROACH OF THE UPPER TROUGH. SHEAR PROFILES WILL BE QUITE  
FAVORABLE FOR SUPERCELLS, AND THE POTENTIAL FOR BOTH TORNADOES AND  
LARGE HAIL REMAINS EVIDENT. HOWEVER, THERE IS CONCERN THAT  
INSTABILITY MAY NOT REACH LEVELS PREVIOUSLY FORECAST DUE TO THE  
PERSISTENT CLOUD COVER AND EARLIER/ONGOING PRECIPITATION.  
REGARDLESS, WILL MAINTAIN THE MODERATE RISK AREA ACROSS PARTS OF  
NORTHERN/CENTRAL IL AND FAR EASTERN IA WITH NO CHANGES GIVEN THE  
VERY STRONG SHEAR PROFILES AND DEVELOPING CONVECTION ACROSS PORTIONS  
OF MO AND SOUTHERN/CENTRAL IA.  
 
A 30% WIND AREA HAS BEEN INTRODUCED FOR PARTS OF THE MID MS VALLEY  
AND MID-SOUTH INTO IN. CONVECTION GRADUALLY INCREASING IN INTENSITY  
ACROSS AR ALONG THE COLD FRONT WILL SHIFT NORTHEASTWARD ACROSS THIS  
REGION THROUGH THE AFTERNOON AND EVENING AS LOW-LEVEL FLOW  
STRENGTHENS. A LINEAR MODE WILL LIKELY DOMINATE WITH DAMAGING WINDS  
THE MAIN THREAT, BUT EMBEDDED SUPERCELLS AND QLCS MESOVORTICIES WITH  
SOME TORNADO POTENTIAL ALSO APPEAR POSSIBLE. ACCORDINGLY, THE  
ENHANCED RISK HAS BEEN EXPANDED SOUTHWARD/EASTWARD TO ACCOUNT FOR  
THIS POTENTIAL.  
 
A MODEST EXPANSION OF THE MARGINAL AND SLIGHT RISK AREAS HAS BEEN  
MADE FROM PARTS OF THE SOUTHEAST INTO THE TN VALLEY AND LOWER OH  
VALLEY TO ACCOUNT FOR BANDS OF CONVECTION CAPABLE OF PRODUCING  
ISOLATED DAMAGING WINDS AND PERHAPS A COUPLE TORNADOES LATE THIS  
EVENING INTO THE OVERNIGHT HOURS. INSTABILITY SHOULD SLOWLY WANE  
TOWARDS THE END OF THE PERIOD, AND A GRADUAL REDUCTION IS STORM  
INTENSITY SHOULD OCCUR WITH EASTWARD EXTENT.  
 
THE MARGINAL AND SLIGHT RISK AREAS HAVE BEEN EXPANDED A LITTLE  
EASTWARD INTO PARTS OF WESTERN PA AND VICINITY TO ACCOUNT FOR  
ONGOING STRONG TO SEVERE CONVECTION CAPABLE OF MAINLY LARGE HAIL AND  
DAMAGING WINDS. THIS ACTIVITY SHOULD WEAKEN WITH EASTWARD EXTENT  
INTO CENTRAL PA WHERE INSTABILITY IS MUCH MORE LIMITED.  
 
FINALLY, SEVERE PROBABILITIES HAVE BEEN REDUCED ACROSS PARTS OF TX  
AND AR BEHIND AN EASTWARD-MOVING COLD FRONT/DRYLINE.  
 
..GLEASON.. 03/28/2020  

 

[CoalCityWxMan]

Looks like SPC is holding serve. Seems like a good choice 

[snowlover2]

 

 

[janetjanet998]

a little late to the party 
..20Z UPDATE  
  
 HOWEVER, THERE IS CONCERN THAT  
INSTABILITY MAY NOT REACH LEVELS PREVIOUSLY FORECAST DUE TO THE  
PERSISTENT CLOUD COVER AND EARLIER/ONGOING PRECIPITATION.  

[geddyweather]

"Given existing uncertainties due to ongoing precipitation/cloud cover, and
anticipated/rapid changes in the environment as the warm front lifts
northward and clouds thin/clear from the west, confidence remains
too low to delineate a potentially concentrated area of greatest
risk, which would otherwise support high risk upgrade."

Yeahhhh, kinda saw that one coming. It's the right call IMO, and it actually somewhat explains the decision making behind the PDS watch a bit.

[Quincy]

Is central Iowa going to explode soon?

[IMADreamer]

Sun just peaking out here finally.  We've jumped three degrees in the last hour or so.  I think the game may be a foot. 

[andyhb]

Too much shear for the updrafts currently. Dewpoints not where they need to be.

[cyclone77]

If I was out I'd wanna be on that cell coming up towards Quincy.  Winds nicely backed ahead of it, and moisture levels in that area are pretty nice.

[Chicago Storm]

IA has produced under my expectations thus far, kind of surprised actually.

I think that's not a good sign overall. 

For now looks like too much shear for the lacking instability.

[Chicago Storm]

Just now, andyhb said:

Too much shear for the updrafts currently. Dewpoints not where they need to be.

Literally beat me by a minute.

[jpeters3]

I've done work in this area.  Strong shear makes convection deepen at a slower rate:

https://journals.ametsoc.org/doi/abs/10.1175/JAS-D-18-0296.1

[StormChaser4Life]

Yea these dew points are drastically lower than models depicted. I'm surprised. There was a good reservoir of mid to upper 60 dews in the lower mid Mississippi Valley last night. Really thought those would advect north quickly. I think the EML ended up being less robust and maybe some mixing near dry slot. IL has been in training showers and clouds all day. Dry slot is finally progressing east but not sure we will have enough time to recover much. Definitely wasn't expecting all this crapvection to persist so long

[janetjanet998]

the is some late clearing NW of STL ..ahead of what appears to the a convergence line  with some CU

note: not talking about the spoke of CU over southern IA into N MO

 

[Chicago Storm]

On 3/28/2020 at 3:32 PM, jpeters3 said:

I've done work in this area.  Strong shear makes convection deepen at a slower rate:

https://journals.ametsoc.org/doi/abs/10.1175/JAS-D-18-0296.1

While true, if it is a continued issue, it has also proven to also be a mitigating factor in significant/sustained severe.

...Which we have seen plenty of times before.

[jpeters3]

6 minutes ago, Chicago Storm said:

While true, if it is a continued issue, it has also proven to also be a mitigating issue in significant/sustained severe.

...Which we have seen plenty of times before.

I agree, I think it might be mitigating development in this case.

 

Edit: now seeing tops approach 35 Kft in the vicinity of Des Moines, and storms are looking healthier.  We shall see.

[Jackstraw]

Golf balls 15 miles to my south, they can have them.

[geddyweather]

Next 2-3 hours are possibly gonna be the make or break stretch. Radar clearing quickly from Champaign, IL to St. Louis, MO but idk if its going to be enough.

Meanwhile, interesting string of cells erupting N and E of Des Moines...

[nwohweather]

Feel bad for Chicago, Detroit and Toledo who are mired north of the front due to convection and the Lakes. It’s 87° here in the Charleston area currently

[WeatherMonger]

Newest watch, has 50/20 probabilities

 

[Jackstraw]

Just now, nwohweather said:

Feel bad for Chicago, Detroit and Toledo who are mired north of the front due to convection and the Lakes. It’s 87° here in the Charleston area currently

You're about a month away from 95/75 every day with 90% humidity lol

[WeatherMonger]

About 7 hours late but sun shining here in KSPI

[Hoosier]

Decently wide area of backed low level flow, though instability obviously lacking with northward extent.