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Tim from Springfield (IL)

May 13-19 Severe/Heavy Rain threats

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From ChicagoStorm in the general severe thread regarding tomorrow:

"Tomorrow definitely holds potential, but all hinges on tonight/tomorrow mornings activity.

SGT risk looks good for now, but could need upgrade to ENH in the morning once everything becomes clear."

 

Going to take the bait and start a thread for the upcoming storm system including tomorrow's severe threat.  This thread can also be a catch-all for other threats including the heavy rain expected in parts of the sub (especially MO/IL) through Sunday, as the system stalls.

Today's threat far west of the sub but SPC's Day 1 has consistently had a marginal up to along and west of the Illinois River:

https://www.spc.noaa.gov/products/outlook/day1otlk.html

 

 

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Day 2 for tomorrow:

https://www.spc.noaa.gov/products/outlook/day2otlk.html

...Eastern Kansas into the Mid Mississippi Valley, Midwest, Ohio
   Valley, and Lower Great Lakes...
   Showers and thunderstorms will likely be ongoing Thursday morning in
   a low-level warm advection regime across parts of the mid MS Valley
   into the Midwest and lower Great Lakes. A weak mid-level
   perturbation associated with this convection should continue to
   shift eastward across these regions through the day. In its wake, a
   more amplified shortwave trough should progress over the northern
   Plains to the Upper Midwest by Thursday evening. At the surface, a
   weak low initially over IA Thursday morning should develop
   northeastward to lower MI by the early evening, with a warm front
   lifting northward across much of the Midwest/OH Valley into the
   lower Great Lakes. A trailing cold front across the mid MS Valley
   into the central Plains is forecast to make only slow southeastward
   progress through the period.

   In the wake of the morning convection, low-level moistening, diurnal
   heating, and steepening mid-level lapse rates owing to an EML
   advecting eastward from the Plains will contribute to a
   destabilizing airmass by Thursday afternoon along/south of both the
   warm and cold fronts. Instability should be stronger from eastern KS
   into the mid MS Valley and perhaps IL, where MLCAPE may reach
   2000-3000+ J/kg before convective initiation. Storms should form
   along/near the cold front by mid to late afternoon, with large-scale
   ascent possibly being aided by another weak mid-level perturbation.
   The stronger mid-level flow associated with the northern
   Plains/Upper Midwest shortwave trough may remain generally displaced
   to the north of the warm sector. Still, there should be enough of a
   veering/strengthening wind profile through the low/mid levels to
   support organized storms. 

   Initial convective development along or just south of the front may
   pose a large hail threat given the steep mid-level lapse rates and
   marginal effective bulk shear values (around 30-35 kt) supporting
   occasional supercells. Although low-level flow is not forecast to be
   particularly strong, a couple tornadoes may also occur with these
   any semi-discrete storms. The Slight Risk has been expanded slightly
   northward across MO/IA/IL to account for better model agreement in
   the placement of the front Thursday afternoon. Damaging winds should
   become the primary threat with time as storms congeal into multiple
   east-southeastward moving clusters/bows through the evening. By late
   Thursday evening/overnight, this activity should weaken as it
   encounters increasing convective inhibition with southeastward
   extent across the warm sector.

   From roughly IN eastward into Lower MI and OH, low-level moisture
   and diurnal heating will probably remain more limited owing to
   morning convection. Still, enough instability should develop by late
   afternoon to pose some large hail/damaging wind threat along and
   south of the northward-moving warm front. Latest guidance suggests
   this front will probably extend across southern Lower MI by Thursday
   evening, with one or more clusters potentially moving eastward along
   or just south of this boundary. The Slight Risk for damaging winds
   has been extended eastward across more of northern/central IN,
   southern Lower MI, and into northwestern OH to account for this
   threat.

 

Also Heavy Rain this weekend including in central Illinois.  ILX's take:

Tab2FileL.png?cdd732dc292cbb4bc4065579c8ed8c6f

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getting quality garden variety this am, amazing how through all the ups and downs, consistently wet remains the name of the game

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5 minutes ago, RyanDe680 said:

morning convection never really a good thing for afternoon convection

not nec, stuff over the area now is irrelevant 

evolution of N MO stuff and wf position is what matters, everything looks as expected to me

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57 minutes ago, CheeselandSkies said:

Not even a flash/rumble here yet again...

I. Just. Want. To. Hear. Thunder. Once more in my life.

Same here.  I picked up 0.43" of rain, but the totals fell short of expectation as much of the action developed east and south.  There was no lightning/thunder here.  Much of today's action should also be south and east.

  • Sad 1

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Quality storms this morning around here.

1.28” rain at ORD this morning and 2.04” here.


.

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Detroit Update to the AFD:

Quote
Late morning satellite imagery indicates a perishable look to the low clouds over
that area which leans expectations toward the higher end of CAPE
estimates for this afternoon into early evening as the warm front
makes northward progress into Lower Michigan. Convection building in
from the west could then become surface based and present severe
weather potential to that portion of SE Michigan in the current
Slight Risk area. Damaging wind remains the primary hazard and the
currently advertised time period of 2 to 8 PM still looks on target.

 

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.62in this morning.  Nice thunder, a little small hail.  It is soupy right now out.  Definitely feels like more is in the offering later.  

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4 hours ago, CheeselandSkies said:

Not even a flash/rumble here yet again...

I. Just. Want. To. Hear. Thunder. Once more in my life.

Until this morning, Madison hadn't recorded a thunderstorm since March.  Meanwhile, Rockford just to the south, has had a half dozen days of thunder since March.  Time for this endless early/mid spring weather to turn more summery.

  • Sad 2

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9 minutes ago, Hoosier said:

Looks like the new outlook trimmed the northern edge of the slight risk.

Classic case of how morning convection screws up the possibility for anything fun in the afternoon.  Looks like a nighttime soaker.

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While there is a still a SLGT worthy severe risk for the area (even if SPC did trim it, they have been meh), the flood threat looks to steal the show overall.

Upwards of 1.00-2.50" of rain fell across a corridor within N Illinois last night/this morning. It looks like a good portion of that corridor will overlap with the heaviest for this afternoon/tonight, with upwards of another 2-5" of rain possible. Could be seeing final totals in that overlap region in excess of 6"...if things line up correctly.

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Midwestern farmers should invest in hydroponics the way rainfall has trended in the area the past 2 decades

  • Sad 2

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The latest Day 2 for tomorrow extends the slight back to central OH, and marginal to C/S IN.  Also a 5/30/15 Enhanced north of NYC:

https://www.spc.noaa.gov/products/outlook/day2otlk.html

...Northeast States and Ohio Valley regions...

   Shortwave trough now situated over ND near the international border
   will continue into the Great Lakes Friday, reaching the northeast
   states later Friday afternoon and evening. A low amplitude impulse
   may precede this feature. By late afternoon the accompanying cold
   front should extend from a surface low in upstate NY southwest into
   the lower Great Lakes and OH Valley. Warm front will extend from the
   surface low through southern New England. Modest low-level moisture
   with upper 50s to around 60 F dewpoints will advect through the
   pre-frontal warm sector and contribute to 1000-1500 J/kg MLCAPE as
   the surface layer warms during the afternoon. Thunderstorms are
   expected to redevelop along and ahead of the front by early to mid
   afternoon within the weakly capped, destabilizing warm sector. A
   mid-level jet within the base of the approaching shortwave trough
   will contribute to 35-45 kt effective bulk shear over the northeast
   U.S. supporting organized storms including a few supercells and
   bowing segments with damaging wind the main threat. The low-level
   jet is forecast to strengthen by late afternoon into early evening
   across the northeast U.S. with 0-1 km hodographs becoming sufficient
   for isolated tornadoes, especially with any storms interacting with
   the warm front across southern New England. Farther west across OH,
   deep-layer shear will be weaker, but wind profiles with 40-45 kt
   flow in the 700-500 mb layer will be supportive of a few damaging
   wind gusts as the boundary layer destabilizes during the afternoon. 

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WPC expanded the excessive rainfall moderate risk into southeast Iowa and basically the northern half of IL. Good write-up below. 

Day 1 Excessive Rainfall Forecast

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1223 PM EDT Thu May 14 2020
 
Day 1
Valid 12Z Thu May 14 2020 - 12Z Fri May 15 2020 

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM CHICAGOLAND 
TO NORTHERN MISSOURI...

...Moderate Risk Area...
A northern stream system skirting across the Midwest, with a 
developing upper level jet streak during convective maximum, 
21-06Z, will interact moderate instability along a slow moving 
frontal zone, to produce a multi-hour heavy rain event this 
afternoon/evening. Synoptic deep layer forcing becomes maximized 
along a zone from northern Missouri and southern Iowa toward 
northern Illinois and southwest lower Michigan. Many model QPFs 
align here, such as the NAM, NAM Nest, WRF-NMMB, and recent HRRR 
runs. The WRF-ARW is a bit of an outlier in how much southward 
propagation it produces, ending up considerably south of the 
rest... but the WRF-ARW2 perhaps represents a more resonable 
southward adjustment that may occur as a result of outflow from 
early-morning convection. Thus, there are still some placement 
challenges, especially toward Chicago where the lake breeze may 
also act to inhibit the northward rebound of instability later on 
today. 

Northern Illinois is, however, more hydrologically vulnerable - 
having received 0.50 to 1.50 inches of rain this morning. Parts of 
the Davenport area also received some local amounts up to two 
inches. Aside from the early-day event, much of the region has 
been running below normal on precipitation recently, with fairly 
dry soils. Thus a second challenge is whether the evening event is 
likely to produce impacts consistent with the Moderate Risk 
category. But there do appear to be enough overlapping factors to 
support Moderate Risk. Inflow of unstable low level air near and 
atop the effective surface front and other outflow boundaries will 
increase to 30-40 knots late this afternoon, with deep layer flow 
becoming quite parallel to the boundaries. We could see a several 
hour period of training, causing what is otherwise an average 
combination of PW and CAPE to produce a few spots of higher-end 
rainfall totals. The NMMB even signals a small 3-inch / 1-hour 
amount in Illinois, and the NAM Nest signals local 3 to 4 inch in 
3 hour totals, indicative of what could occur. This may lead to 
numerous flash floods and isolated higher-end impacts.

Thanks to the WFOs and RFCs for helping shape the updated Moderate 
Risk contour.
  • Thanks 1

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1 hour ago, wisconsinwx said:

Until this morning, Madison hadn't recorded a thunderstorm since March.  Meanwhile, Rockford just to the south, has had a half dozen days of thunder since March.  Time for this endless early/mid spring weather to turn more summery.

We did record one this morning? Not in my part of town. :(

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1 hour ago, RyanDe680 said:

 

Classic case of how morning convection screws up the possibility for anything fun in the afternoon.  Looks like a nighttime soaker.

imo, could still have some severe threat north of I-80, pending ability to recover.  I do think blaming the morning/current stuff is a bit simplistic because it has been happening south of I-80 too, where the SLGT still exists.

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I think the best chance for development remains in MO, with the ability to ride NE into central IL.  Wouldn't be shocked to see the slight risk trimmed further south.  CAPE isn't currently anywhere near substantial unless you are Springfield or south and the wind field is a mess.

 

We're gonna ride an axis with a crap ton of rain though.

 

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23 minutes ago, RyanDe680 said:

I think the best chance for development remains in MO, with the ability to ride NE into central IL.  Wouldn't be shocked to see the slight risk trimmed further south.  CAPE isn't currently anywhere near substantial unless you are Springfield or south and the wind field is a mess.

 

We're gonna ride an axis with a crap ton of rain though.

 

The whole area has the same kind of threat...No matter if you're in ORD, IKK or GBG.

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56 minutes ago, CheeselandSkies said:

We did record one this morning? Not in my part of town. :(

One of the airport's morning obs reported, but that was the southeast part of town per lightning data.

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