2020 Short/Medium Range Severe Thread

[hlcater]

Conditional setup tomorrow for eastern Iowa that should deliver a nice QLCS with some locally gusty winds at a minimum. Shear is quite good and more than sufficient for a supercell/tornado threat by itself however shear vectors relative to the boundary, degree of forcing on said boundary and risk for cloud cover or a near surface inversion all suggest that risk is low if existent at all, despite the shear/instability that should be present. That said, if additional clearing is realized, there could be a brief window for something if there is a discrete storm around to tap into the 250+ 0-1km SRH/300+ 0-3km SRH. I don’t think this setup has what it takes personally but I probably still get suckered into chasing it due to the 0 minute drive to the target area.

 

Plan would be to just find the warm front and just hope for the best

[cyclone77]

1 hour ago, hlcater said:

Conditional setup tomorrow for eastern Iowa that should deliver a nice QLCS with some locally gusty winds at a minimum. Shear is quite good and more than sufficient for a supercell/tornado threat by itself however shear vectors relative to the boundary, degree of forcing on said boundary and risk for cloud cover or a near surface inversion all suggest that risk is low if existent at all, despite the shear/instability that should be present. That said, if additional clearing is realized, there could be a brief window for something if there is a discrete storm around to tap into the 250+ 0-1km SRH/300+ 0-3km SRH. I don’t think this setup has what it takes personally but I probably still get suckered into chasing it due to the 0 minute drive to the target area.

 

Plan would be to just find the warm front and just hope for the best

Cedar Rapids is dead center in the middle of the slight risk today.  Cedar Rapids is killing it this year.  Derecho, multiple early season snows, epicenter of potential severe today.  If luck continues maybe you guys can breach the 1ft mark for a snowstorm this winter.

[Chicago Storm]

Today has no real threat overall, other than for a few hailers. Just about all activity will be post anafront.

[hlcater]

4 hours ago, Chicago Storm said:

Today has no real threat overall, other than for a few hailers. Just about all activity will be post anafront.

Yup that’s what I’m thinking. Would need a storm to separate itself to do much of anything and I just don’t think that happens 

[HillsdaleMIWeather]

5% TOR for SE lower Michigan

[Stebo]

This actually has the making of a solid potential, good instability, good shear, we aren't getting rained on in the morning. Timing is great, and a strong front to boot.

[nwohweather]

Could get dicey around 4-6 PM with storms. Instability isn't the greatest but if the SRH can get a little better, might get a couple spinners before this thing lines up

[Jim Martin]

Seconds before the storm hit here downtown. 60 MPH wind and some damage here in town.

[michsnowfreak]

quite a shelf cloud with that storm

[sojitodd]

Just about the last thing I expected to hear this early evening is tornado sirens going off. *sigh*  There will be no tornado.

[purduewx80]

Quote

 ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE OZARKS AND MID TO UPPER MISSISSIPPI VALLEY...

   ...SUMMARY...
   Thunderstorms associated with strong wind gusts and hail will be
   possible on Tuesday across parts of the Ozarks and mid to upper
   Mississippi Valley.

   ...Ozarks/Mid Mississippi Valley...
   An upper-level trough will move quickly northeastward on Tuesday
   from the Great Plains into the mid to upper Mississippi Valley. At
   the surface, a cold front will advance east-southeastward across the
   mid to upper Mississippi Valley. A line of thunderstorms is forecast
   to be ongoing along the front from eastern Iowa south-southwestward
   into western Missouri at the start of the period. As the upper-level
   trough approaches from the southwest, strong large-scale ascent will
   sustain the line during the day as it moves eastward across the mid
   to upper Mississippi Valley. Ahead of this line, surface dewpoints
   in the lower to mid 60s F will contribute to weak instability by
   afternoon. 

   Model forecasts over the last couple of runs have substantially
   increased forecast instability across the mid to upper Mississippi
   Valley. Current model solutions suggest that SBCAPE could peak in
   the 400 to 600 J/kg range in the afternoon from eastern Missouri
   into north-central Illinois. This combined with strong deep-layer
   shear of 60 to 70 kt, evident on forecast soundings, should support
   a marginal severe threat along the leading edge of the line. Strong
   wind gusts and hail will be possible with the more intense parts of
   the line. The line of storms is forecast to reach eastern Illinois
   and southern Lake Michigan by early evening.

 

Wise move on their part. Forecasts based on instability from the NAM or GFS the past few days are unrealistic given the former's bias of being too cool in the boundary layer (too cloudy/moist; temps 5-10F too cool in this warm spell) and the latter's lack of resolving temp/moisture profiles correctly. 

More importantly, with the dynamics in play and as we see with more classic 2nd season events, it's more about the instability and shear from the surface to 3km. From a pattern recognition perspective, a deepening low with 60-degree+ dew points and a 50KT+ LLJ in Nov tells us more than any one model can. It's possible there isn't a ton of lightning, but with the wind field in place I imagine some scattered wind damage could occur. The placement of SPC's 2% area for tornadoes looks good to me.

[Hoosier]

Certainly looks worthy of the marginal risk.  Not going to take much to get strong/borderline severe gusts at the surface.  Perhaps we can will a narrow slight risk out of this setup, but we'll see.  

[Chicago Storm]

Looks like a general marginal risk worthy day for the area the SPC has outlined.

110kt jet streak, strengthening SLP riding NE, large area of 60+ DP's...Only thing lacking is instability.

[Hoosier]

The 18z NAM and 21z RAP came in with higher CAPE.  If they look likely to verify, then a slight risk would be warranted imo.

[Chicago Storm]

The 18z NAM and 21z RAP came in with higher CAPE.  If they look likely to verify, then a slight risk would be warranted imo.

If that trend continues, I’d agree...for much of the Quad Cities CWA.


.

[Chicago Storm]

Looks like a general marginal risk worthy day for the area the SPC has outlined.
110kt jet streak, strengthening SLP riding NE, large area of 60+ DP's...Only thing lacking is instability.

0z guidance held serve.


.

[hlcater]

SPC goes 5% for wind/tor. Given degree of shear and really low level instability that isn't *awful*, I could see a few mesovort type tors in the line. HRRRs are pretty bullish, even exceeding 1000 SBCAPE. Storm mode looks poor overall here. Doesn't look especially chaseable even if there are tornadoes to be had.

[yoda]

4 hours ago, hlcater said:

SPC goes 5% for wind/tor. Given degree of shear and really low level instability that isn't *awful*, I could see a few mesovort type tors in the line. HRRRs are pretty bullish, even exceeding 1000 SBCAPE. Storm mode looks poor overall here. Doesn't look especially chaseable even if there are tornadoes to be had.

You mean 15% wind and 5% tor... SLGT risk

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1138 PM CST Mon Nov 09 2020

   Valid 101200Z - 111200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   NORTHEAST MO...EASTERN IA...NORTHERN IL AND SOUTHERN WI...

   ...SUMMARY...
   Thunderstorms capable of producing isolated strong to locally
   damaging winds and perhaps a few tornadoes are possible this
   afternoon and evening across portions of the Middle Mississippi
   Valley vicinity.

   ...Mid-Mississippi Valley Vicinity...

   A potent midlevel shortwave trough will become negatively tilted
   today as it ejects east/northeast from northern/central Plains to
   the upper Great Lakes. At the surface, low pressure will deepen at
   it track northeast from MO into eastern IA by midday. Strong
   southerly flow ahead of the surface low and eastward-advancing cold
   front will transport low 60s dewpoints as far north as southern WI
   and southern lower MI. While heating will be limited by cloudy
   skies, cooling aloft will result in steepening midlevel lapse rates
   and modest instability (generally less than 750 J/kg MLCAPE) is
   expected during the afternoon and early evening. Thunderstorms are
   first expected to develop and intensify during the afternoon across
   northern MO into eastern IA. Deep layer flow will generally be
   parallel to the cold front, supporting a more linear storm-mode with
   line segments/QLCS development expected. 

   Given the deepening surface low, some backing of near-surface winds
   is expected closer to the low from eastern IA into northern IL and
   southern WI. This could increase the potential for mesovortex
   formation within the broader QLCS/bowing segments. Forecast
   soundings indeed show enlarged, curved hodographs with both
   increasing directional and speed shear leading to 0-1 km SRH values
   greater than 250 m2/s2. As a result, a few tornadoes are possible,
   in addition to isolated strong/locally damaging wind gusts. The
   severe threat should decrease with time and eastward extent as the
   boundary layer stabilizes with the loss of daytime heating and
   strong forcing ejects northeast over the upper Great Lakes and
   Ontario.

[luckyweather]

LOT AM discussion:

Strong southerly flow ahead of the surface low has already advected
60 degree dewpoints into northern IL While heating will be limited
by cloudy skies, cooling aloft will result in steepening midlevel
lapse rates and modest instability (though impressive for our region
in November in spite of MLCAPE holding mostly under 750 J/kg) is
expected during the afternoon and early evening. The CAPE has some
vertical extent to it, and has shown some increase over the past few
days where it was appearing to be fairly minimal. Thunderstorms will
first develop during the afternoon across northern MO into eastern
IA. Deep layer flow will generally be parallel to the cold front,
supporting a more linear storm-mode with line segments/QLCS
development expected, with this line spreading eastward late this
afternoon into north central IL, and into the Chicago metro toward
evening.

Combine these forcing mechanisms with the fact that we are coming
out of a record breaking warm streak here in early November. We have
been overperforming on temperatures, underperforming on clouds,
and could see record highs yet again today. This pattern with a
negative tilted trough, strong upper jet and associated low/mid
level winds, strong cold front, and a deepening low to our
northwest in the presence of a warm and modestly unstable airmass
is an ominous one.

With all this in mind, a slight risk for severe weather has been
posted by the Storm Prediction Center. This is not unheard of in
November, but not super common also. Damaging winds is the first
concern The forecasted tornado risk area is fairly large in the 6z
issuance from SPC. We will attempt to target some of the messaging
for this, as there is likely a higher concern in northwest
Illinois and into north central Illinois. This area is juxtaposed
in an area with the best combination of forcing aloft, near the
low track and approaching cold front that will overlay the narrow
instability axis. Strong winds will still accompany the line of
storms as it moves east, but instability will wane a bit with
eastward extent suggesting some weakening as the line gets into
northwest Indiana. Winds may become locally backed ahead of the
low even though models are not depicting strong turning of the
surface winds. Still, forecast soundings depict enlarged, curved
hodographs given the strong low level wind fields. Speed shear is
present along with some directional shear above the near surface
layer, leading to 0-1 km SRH values greater than 250 m2/s2. As a
result, a few tornadoes are possible.

[purduewx80]

Mid-level lapse rates are as steep as 8.4C/km at DVN this morning; traditional 700-500mb lapse rates are a bit skewed due to the influence of the historic ridging (notice warm nose at 500-550mb). These lapse rates will adjust later as the upper wave brings cooling at both 500 and 700 mb.

This is an experimental high shear/low CAPE product being run at NC State. The red shading basically indicates areas that favor spinups either in the QLCS or in supercells that may develop.

[Indystorm]

Slight risk indeed, with 5% tor probs......could be an interesting afternoon and evening.  Washington IL tor was Nov. 17, 2013 so we know we can get svr in this second season. Cloud breaks over parts of IL will enhance insolation and instability. That was a high risk, PDS tor watch scenario however, as instability was much higher than what is expected today. Low pressure near KC is already prompting SPC discussion of an upcoming possible svr or tor watch for much for much of central to ne MO into west central IL.

[WaryWarren]

Tornado sirens just went off where I'm at. 

[CheeselandSkies]

14 minutes ago, WaryWarren said:

Tornado sirens just went off where I'm at. 

Which is where (no location given on your profile)? There are no tornado warnings currently in effect anywhere in the CONUS.

[Intensewind002]

When was the last time there was a legitimate tornado threat, minus hurricanes. I swear it's been months at this point

[CheeselandSkies]

Blue box out, doesn't extend north of the WI/IL border though.

Been overcast with sprinkles all morning, honestly thought we'd be trimmed out of the slight risk at 1630.

[CheeselandSkies]

Solid overcast, periodic rain and quite chilly in Madison early this afternoon. Although we were kept in the slight risk/5% TOR zone for 1630, pretty clear nothing is going to happen around here unless the warm sector abruptly gets yanked over us, but I don't believe this was supposed to be that kind of setup.

[StormfanaticInd]

We are getting plenty of sun today. 

[purduewx80]

4 minutes ago, CheeselandSkies said:

Solid overcast, periodic rain and quite chilly in Madison early this afternoon. Although we were kept in the slight risk/5% TOR zone for 1630, pretty clear nothing is going to happen around here unless the warm sector abruptly gets yanked over us, but I don't believe this was supposed to be that kind of setup.

Warm front has been retreating near the MS River but I agree that with the exception of far SE Dane County, you're probably in the clear there.

[purduewx80]

The surface low is back in the cold air in Iowa, but there is a meso-low in SE Iowa causing surface winds to back more SSE in the warm sector. The relatively highest tornado risk will be from the Quad Cities to near Rockford and perhaps far SE WI this afternoon, especially where showers ahead of the line feed into it.

[RyanDe680]

2020 looks to keep delivering the shots