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2023 Short/Medium Range Severe Weather Discussion


Chicago Storm
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This is what I meant with my (partially) tounge-in-cheek observation; that predictability of severe weather in the summer is such that even as recently as the overnight hours, today was looking like a wash for severe potential north of I-80 in IL.

The flip side of this of course, is that it makes it near impossible to plan chases/take PTO in advance. For me, it's local enough that I can head out with my 3A-noon shift.

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The SPC is a believer at least...

 

https://www.spc.noaa.gov/products/md/md1506.html

 

 Mesoscale Discussion 1506
   NWS Storm Prediction Center Norman OK
   0305 PM CDT Wed Jul 12 2023

   Areas affected...Northern Illinois and far southern Wisconsin

   Concerning...Severe potential...Tornado Watch likely 

   Valid 122005Z - 122130Z

   Probability of Watch Issuance...95 percent

   SUMMARY...A tornado watch is likely across northern Illinois and
   possibly southern Wisconsin by 21Z.

   DISCUSSION...The air mass is recovering rapidly across northern
   Illinois in the wake of the morning MCS. An EML, advecting eastward
   amid 40-50 knots of mid-level flow has cleared out cloud cover and
   allowed for surface heating across eastern Iowa and northwest
   Illinois. Temperatures in this area have warmed into the low 80s
   with dewpoints remaining steady, or even climbing slightly, into the
   low 70s. Temperatures remain in the 60s across northern Illinois,
   but expect this warm front to lift quickly northeast through the
   evening as a result of surface heating north of this front and
   strengthening low-level flow in response to the deepening surface
   cyclone across eastern Iowa.

   Additional heating, combined with cooling temperatures aloft ahead
   of the approaching shortwave trough should result in 1500 to 2000
   J/kg MLCAPE by this evening across northern and northeast Illinois.
   This instability will be co-located with a strong, veering wind
   profile (sampled by the 20Z LOT VWP). Expect a similar wind profile
   (featuring 200+ m2/s2 0-500m SRH) to remain along the outflow
   boundary/composite front through the evening. Supercells are
   expected to form along this boundary as ascent increases ahead of a
   digging mid-level shortwave trough and within the left-exit region
   of the upper-level jet. Southerly winds ahead of the surface low
   will provide sufficient low-level streamwise vorticity for a tornado
   threat. However, any storms which remain along or slightly
   north/east of the boundary, where more backed surface winds will be
   present, should ingest much higher SRH and will pose a greater
   tornado threat and even the potential for a strong tornado. In
   addition, large hail and damaging wind gusts will be possible.

   A tornado watch is likely by 4pm to cover this threat.

   ..Bentley.. 07/12/2023

 

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LOT afternoon update is spicy. 

 

Over the next few hours, explosive thunderstorm development appears
likely near the Mississippi River with the favorable thermodynamic
and kinematic parameter space supporting a quick evolution into
several supercells. Damaging winds and hail are likely with any
storm. Perhaps more concerning, Bunker`s right storm motion along
the warm front will provide unusually long residence times within
the high-magnitude low-level SRH environment, supporting an
unusually high threat for episodic strong tornadoes (EF2+) for our
local area
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