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October 2021 General Discussion


Hoosier
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This upper low lifting north through the western sub greatly over-performed around here.  Widespread 0.75-1.75" fell across the Cedar Rapids area last evening and overnight.  My total is 1.01".  I was just hoping for a tenth or two.  Monday's system should lay down another swath of good rain across eastern Iowa.  :raining::thumbsup:

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KIND :ph34r:

 

 

Models are starting to come to a better consensus for the first low
which will bring a line of thunderstorms along a cold (or really,
slightly cooler) front across the region from late Monday evening
into Tuesday. Tight pressure gradients ahead of this system will
bring breezy winds to the area during the day Monday as well. Will
have to keep an eye for the potential of severe weather Monday
night... seeing CAPE values around 1000 J/kg and bulk shear values
around 50. There is still much to be seen and refined until then,
but the potential for some embedded severe storms is not out of the
question.
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Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CDT Sat Oct 09 2021

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MID
   MISSISSIPPI/LOWER OHIO VALLEYS TO LOWER MICHIGAN...

   ...SUMMARY...
   Strong/locally severe storms -- including potential for hail,
   locally damaging winds, and a couple of tornadoes -- are expected to
   spread from the Mid Mississippi Valley region early,
   north-northeastward into the Upper Great Lakes into the
   evening/overnight hours Sunday and into early Monday.

   ...Synopsis...
   Western U.S. troughing will continue to dig south-southeastward
   Sunday, eventually evolving into a closed low surrounded by cyclonic
   flow which should encompass the entire Intermountain West by the end
   of the period.  Ahead of this digging system, a negatively tilted
   short-wave trough will eject north-northeastward across the Mid
   Mississippi and Lower Ohio Valleys, and into the Upper Great Lakes
   overnight.

   At the surface, a cold front ahead of the western trough will cross
   the Great Basin/northern Intermountain region during the first half
   of the period, reaching a position from the northern Plains to the
   Four Corners states by the end of the period.

   Farther east, a frontal wave will shift north-northeastward from
   Missouri to Wisconsin, while the cold front makes only minor
   eastward progress through the period.

   ...Lower Ohio/Mid Mississippi Valley northeastward to Lower
   Michigan...
   Showers and thunderstorms are forecast to be ongoing across the
   Lower Missouri/Mid Mississippi Valley area at the start of the
   period, with local severe risk possibly accompanying a few of the
   stronger updrafts.  As the upper trough sweeps north-northeastward
   in an increasingly negatively tilted manner through the day, and a
   surface frontal wave moves across Missouri to northern Illinois,
   surface heating beneath steep mid-level lapse rates ahead of ongoing
   convection through late morning should allow ample destabilization
   to foster redevelopment/reintensification of convection ahead of the
   low/front.

   Given strong flow with height ahead of the upper system, veering
   gradually through mid levels, shear will support updraft rotation,
   resulting in scattered strong/severe storms capable of producing all
   severe hazards.  Risk should gradually spread northward, across the
   Midwest and extending into lower Michigan through the evening and
   into the overnight hours.

   ..Goss.. 10/09/2021

image.png.1b0f94cf60605146574013df1a3645bb.png

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Monday is getting interesting 

 

KIND

 

The unseasonably warm weather will continue for much of the upcoming
week even as we transition back into a more active regime. A broad
upper trough will remain anchored over the Rockies and High Plains
through much of the first half of the week...with pieces of energy
aloft kicking out downstream of the trough.

The first of these pieces of energy will move into the western Great
Lakes late Monday into Monday night...helping to generate a surface
wave over the southern Plains late Sunday before lifting northeast
into Wisconsin by Monday evening. Expect a warm...breezy day for the
forecast area Monday with rain chances increasing by late day as a
trailing frontal boundary accompanies the surface low and swings
into the area Monday night. The overall model suite has come into
better alignment on the track of the features at the surface and
aloft with just timing differences now present. However...the
orientation and track of the system does present some potential for
convective impacts across central Indiana late Monday afternoon and
evening and a higher ceiling for severe weather as well with modest
BL shear and instability present ahead of the front.

At this point...potential setting up for predominantly linear
convection ahead of the front Monday afternoon and evening with
damaging winds. Model soundings though do show a nice amount of
directional shear through the boundary layer and storm relative
helicities over 200 m2/s2 in a narrow axis ahead of the front which
would support rotating updrafts and an elevated risk for tornadoes.
This will be something to monitor over the weekend as the parameters
associated with this system align further.
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NWS NORTHERN INDIANA 

 

"A vigorous upper low will be ejecting up from the
southwest during this period, bringing showers and thunderstorms to
the area Monday night into Tuesday morning. SPC now has the area in
a slight risk for severe storms with this system. This is definitely
plausible as a high shear, low CAPE situation. NAM sfc CAPE is less
than 2000 J/kg, but bulk shear increases to 50 kts Monday evening.
Damaging wind, hail, and even a few tornadoes will be possible."
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