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July 23-24 Severe Weather


MNstorms
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Already a day3 enhanced highlighted. Models hint this could be high end event.

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 ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE UPPER MIDWEST...

   ...SUMMARY...
   Scattered severe thunderstorms should occur Saturday across parts of
   the Upper Midwest. A few tornadoes, large to very large hail, and
   significant damaging winds all appear possible.

   ...Upper Midwest into the Great Lakes...
   A notable shortwave trough is forecast to progress from the northern
   Plains east-southeastward across the Upper Midwest and Great Lakes
   on Saturday. A belt of enhanced mid/upper-level flow will likely
   accompany this shortwave trough and act to organize thunderstorms
   that develop ahead of it through the day. There is reasonably good
   agreement in model guidance that a very moist low-level airmass will
   be in place ahead of a front across the Upper Midwest Saturday
   morning. Steepening mid-level lapse rates and robust heating of this
   airmass through the early afternoon should foster moderate to strong
   instability. Deep-layer shear will be more than sufficient for
   organized updrafts, and supercells with a threat for very large hail
   appear possible with initial convective development across MN.

   Most guidance also suggests that quick upscale growth into a MCS
   will occur Saturday afternoon/evening with eastward extent into
   western/central WI and northeastern IA. Given the degree of buoyancy
   available, at least scattered damaging/severe winds appear probable
   as this mode transition occurs. Some of these winds may be
   significant. Have included an Enhanced Risk where MCS development
   and propagation appear most likely. Enough low-level shear
   associated with a southwesterly low-level jet is also forecast to
   support a threat for a few tornadoes. This severe threat should
   continue into the Great Lakes region Saturday night, but lesser
   instability forecast with eastward extent should keep the overall
   severe threat fairly isolated.

 

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29 minutes ago, tuanis said:

7” of rain, 4 rounds of hail, somehow we didn’t flood but it came so damn close. I’m exhausted from preparing the house for water all night, and now another noisy cell pops overhead.

Looks like worst of it skirted just north of here and hammered Lake Co

Screenshot_20220723-082033_Samsung Internet.jpg

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MKX 15:15Z update said there was still some lingering convection over south-central WI, but seen nothing but sunshine out my window since getting up at 15Z.

Edit: Looks like things may be a bit ahead of schedule, wasn't expecting to be being considered for a watch (or just outside of the area being considered for a watch) this early.

https://www.spc.noaa.gov/products/md/md1563.html

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One of the most detailed severe weather AFDs I've seen from MKX in quite a while. Of course, also been a while since the core of a potential significant threat was focused over their CWA, with most of them in recent years setting up just to the north/northwest (6/15 and a few others this year) or south (northern Illinois).

Quote
000
FXUS63 KMKX 231515
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1015 AM CDT Sat Jul 23 2022

.UPDATE...
(Issued 1015 AM CDT Sat Jul 23 2022)

Looking like a troubling forecast for southern Wisconsin for this
afternoon and evening with confidence continuing to grow for a
significant severe weather event for the area. A lot of
ingredients are coming together to put all of the area at risk for
later today.

Initially focused on the lingering convection in south central
Wisconsin. This backbuilding band of convection is nicely marking
the low level thermal/moisture gradient in place there. The 23.13z
RAP shows the 925-850mb moisture transport currently pushing into
that area but then shunts it more to the east southeast later in
the morning which should mark the end of that development.
However, this transport quickly increases through the afternoon
with a convergence zone still angling from near La Crosse
southeastward toward far southeast Wisconsin...so wouldn`t be
shocked if this forcing is just enough to pop some other scattered
convection as that feature reintensifies this afternoon.

As for the severe threat later this afternoon into tonight, quite
a bit coming together to put together what looks to be a rather
significant severe weather event for southern Wisconsin. Current
23.14z mesoanalysis shows a surface low pressure system over
south central South Dakota with a warm front running east out of
it along the MN/IA border before tailing a bit to the southeast
into NW IL (well SW of the current convection in SW WI).
Convection that is currently ongoing in central Minnesota is
expected to be our focus for development later today.

This warm front is forecast to lift northward and setup from
southeast Minnesota on into southeast Wisconsin by this evening.
Initial surface dew point analysis is showing that the RAP/HRRR is
doing pretty well with showing low to mid 70F dew points along
this arching warm front while the 23.12z NAM seems to be pushing
those higher dew points way further to the north (GRB). Thus, will
be following more along the lines of the RAP/HRRR this morning.

As a result of these high surface dew points, sunny conditions
leading to high temperatures getting into the 90s, and steep mid-
level lapse rates in place, 23.14z RAP soundings show a fat CAPE
profile through the afternoon and evening hours with the RAP
showing about 4,000-5,000 J/kg of SB/MLCAPE along the warm front.
These soundings do show a very small cap in place around 800mb
which should hold things off from freely convecting through the
afternoon and allow for the destabilization to occur. The trigger
will come through in the form of the mid level shortwave
trough/sfc low/and-or the strengthening low level jet.

As for the wind shear, the 23.14z RAP profiles show a well
balanced increase in wind speeds and veering wind directions with
height which will lead to a very favorable effective wind shear
profile. Low level wind shear/helicity increases along the warm
front from late afternoon into the evening as the low level jet
strengthens across southern Wisconsin. Will be keeping a close eye
on any surges that happen with the expected QLCS for mesovort
development as it will be a favorable environment for it unless it
becomes outflow dominant.

While the main focus is on the potential for a destructive wind
event, can`t rule out the possibility of supercell thunderstorm
storm modes given the high instability and favorable wind shear
profile. Typically, the lines can be blurred with these events
being either a derecho or supercell environment. Regardless, all
hazard types are on the table for later today/tonight. More timing
details to fall out by this afternoon.

Halbach

 

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I’m out camping in NW IL this weekend, at White Pines State Park (Near Oregon, IL).

Didn’t see the same extent of training activity that the Chicago metro area did overnight/this morning, but did end up in a severe t’storm warning around 4:15AM with a stronger t’storm, and had a few other smaller t’storms nearby earlier this morning.

The aforementioned severe t’storm produced 50-60MPH winds, marble size hail and a great light show.

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They're late with the 1630...
Edit: Finally out, no moderate. default_huh.png

Seems like a good call to have stayed enhanced, at least for now.

There’s a lot of modified air over S WI/N IL/N IN/S MI, with an OFB pushing west and reinforcing in across SW WI and NW IL. We’ll see how it shakes out with time, but it could mean the maximized potential is in a small corridor across portions of NE IA/S WI/N IL.
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18 minutes ago, vortex said:

Caplan FB says confirmed touchdown in Naperville this morning.   

Yeah LOT confirmed it in a preliminary survey at about 8 am.  No rating yet though. 

This tornado was before 12z, so the valid outlook at the time didn't even have a 2% tornado area.  A reminder that tornadoes can still occur.

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17 minutes ago, Hoosier said:

Yeah LOT confirmed it in a preliminary survey at about 8 am.  No rating yet though. 

This tornado was before 12z, so the valid outlook at the time didn't even have a 2% tornado area.  A reminder that tornadoes can still occur.

Ahh. Missed that.  Thanks.  

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Didn’t rain here last night, but with strong southerly flow the modified air has settled in here. Dew points were briefly in the upper 50’s this morning, but have only slightly increased to 63° imby at the moment with a stern 15-20mph southerly wind. 18z guidance not handling the surface moisture at all. Plumes all showing 70-74° surface dpoints at the current hour. SB instability obviously not materializing as expected across southern lower Michigan so that’s probably why the slight makes that turn SE, betting that the strongest storms ride that gradient further south and most convection will weaken quickly this side of the lake tonight. 

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Watch being considered for portions of central/northern IL along the OFB.

https://www.spc.noaa.gov/products/md/md1565.html

Things seem to be evolving roughly as expected with the MN/Nrn. IA MCS, with no significant trends up or down.

 

Quote

The National Weather Service in La Crosse has issued a

* Severe Thunderstorm Warning for...
  Fillmore County in southeastern Minnesota...

* Until 315 PM CDT.

* At 205 PM CDT, severe thunderstorms were located along a line
  extending from near Stewartville to near Adams, moving east at 35
  mph.

  HAZARD...70 mph wind gusts and quarter size hail.

  SOURCE...Law enforcement reported 70+ mph wind gusts.

  IMPACT...Hail damage to vehicles is expected. Expect considerable
           tree damage. Wind damage is also likely to mobile homes,
           roofs, and outbuildings.

Anvil debris from that beginning to push overhead but still seeing filtered sunshine in west Madison at 1917Z.

For a :twister:threat, would have liked to see that OFB oriented more NW-SE instead of NNW-SSE as it appears to be.

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