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Late April-Early May Heavy Rain/Severe Possibilities


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17 minutes ago, cyclone77 said:

12km NAM looks too far northwest with the heaviest rains.  Heavy convection/cold pools will keep the boundary well southeast of where it's showing the heavy rain corridor.  It's dropping way too much rain northwest of the front.  Doesn't look realistic at all.

I thought the same thing.  But there is a pretty stout and persistent LLJ into the area on that run.  IF by some chance it were to pan out, it would certainly be one of the more prolific cool side frontal rain events that I can recall.

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NAM and GFS dump 5-8" here, with the GFS on the heavier side.  Really impressive output but not ready to buy into super high numbers like that quite yet.



Did you happen to catch the comparison graphic my office put up for the 18z 12km and 3km NAM runs? The 3km NAM gets more rain into the metro area but still nowhere near close to the NAM and the globals. Obviously can't take the 3km NAM solution verbatim but it's been showing a reasonable depiction of how convection could rob moisture transport well north of the warm front. WPC seemed to be accounting for that in their placement of the day 3 excessive rain outlook.
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34 minutes ago, RCNYILWX said:

 


Did you happen to catch the comparison graphic my office put up for the 18z 12km and 3km NAM runs? The 3km NAM gets more rain into the metro area but still nowhere near close to the NAM and the globals. Obviously can't take the 3km NAM solution verbatim but it's been showing a reasonable depiction of how convection could rob moisture transport well north of the warm front. WPC seemed to be accounting for that in their placement of the day 3 excessive rain outlook.

 

Just checked it out.  Have to consider that lesser scenario of course.

Will also need to watch for a possible severe threat nosing into at least part of the LOT cwa, especially on Sunday.  The triple point should pass through the area and forecast soundings are showing quite a bit of shear but limited instability.

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5 minutes ago, Hoosier said:

Just checked it out.  Have to consider that lesser scenario of course.

Will also need to watch for a possible severe threat nosing into at least part of the LOT cwa, especially on Sunday.  The triple point should pass through the area and forecast soundings are showing quite a bit of shear but limited instability.

 

Speaking of severe. The kentucky part of our subforum should pay close attention tomorrow. 

Screen Shot 2017-04-28 at 1.47.06 AM.png

Screen Shot 2017-04-28 at 1.46.55 AM.png

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Just checked it out.  Have to consider that lesser scenario of course.

Will also need to watch for a possible severe threat nosing into at least part of the LOT cwa, especially on Sunday.  The triple point should pass through the area and forecast soundings are showing quite a bit of shear but limited instability.



Definitely agree on potential severe threat on Sunday. Very high shear, especially low level, low cape and very moist/low LCL setup, with NAM being on more bullish side with instability. If the low level cape is sufficient, an appreciable tornado threat could get into or near LOT CWA. Could see warm front being reinforced south by convection a bit and thus late to get into CWA. For that reason, my guess is SPC brings a slight risk up to ILX CWA and marginal into southern LOT CWA on day 3 outlook. Interested to see what they do.
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9 minutes ago, RCNYILWX said:

 


Definitely agree on potential severe threat on Sunday. Very high shear, especially low level, low cape and very moist/low LCL setup, with NAM being on more bullish side with instability. If the low level cape is sufficient, an appreciable tornado threat could get into or near LOT CWA. Could see warm front being reinforced south by convection a bit and thus late to get into CWA. For that reason, my guess is SPC brings a slight risk up to ILX CWA and marginal into southern LOT CWA on day 3 outlook. Interested to see what they do.

Been noticing the same for extreme southern lower MI on Sunday, with respect to the NAM and a warm frontal tornado threat. Something to monitor as there certainly would be enough forcing along the front to trigger storms and great convergence if something were to ride the boundary.

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Been noticing the same for extreme southern lower MI on Sunday, with respect to the NAM and a warm frontal tornado threat. Something to monitor as there certainly would be enough forcing along the front to trigger storms and great convergence if something were to ride the boundary.



Yep agree, was focusing on IL but the threat could extend farther east as well. The mid and upper winds are also a bit more veered with eastward extent as well. Hard to say if NAM is handling synoptic side well yet but it does typically do a better job depicting low level instability than GFS. Had pulled a sounding with >100 j/kg 3km CAPE from NAM in central IL and if storm mode can remain discrete that would get it done given magnitude of LL shear.

Sent from my SM-G935V using Tapatalk

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Just now, RCNYILWX said:

 


Yep agree, was focusing on IL but the threat could extend farther east as well. The mid and upper winds are also a bit more veered with eastward extent as well. Hard to say if NAM is handling synoptic side well yet but it does typically do a better job depicting low level instability than GFS. Had pulled a sounding with >100 j/kg 3km CAPE from NAM in central IL and if storm mode can remain discrete that would get it done given magnitude of LL shear.

Sent from my SM-G935V using Tapatalk
 

Yeah, my biggest concern with these types of setups, is that the atmosphere gets so worked over that Sunday will run out of gas due to poor lapse rates and lots of clouds/rain. Guess we will see what happens there.

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Yeah, my biggest concern with these types of setups, is that the atmosphere gets so worked over that Sunday will run out of gas due to poor lapse rates and lots of clouds/rain. Guess we will see what happens there.



100% valid concern, if cape is even less than what's being progged then any updraft attempt near WF/TP could get sheared apart. Also wondering if kinematics of mature and strengthening synoptic system help overcome the potential negating issues.
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Just now, RCNYILWX said:

 


100% valid concern, if cape is even less than what's being progged then any updraft attempt near WF/TP could get sheared apart. Also wondering if kinematics of mature and strengthening synoptic system help overcome the potential negating issues.

Yeah the plus side is the system isn't occluding so we do have that working for us. Also the atmosphere on the NAM for Sunday isn't exactly off the wall so it wouldn't be hard to achieve compared to something where we are expecting +4000J/kg coming in.

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That subtle impulse in the Ozarks referenced in today's 1300 Outlook is the player I'm watching for the mid MS/lower Ohio Valley later this afternoon as storms now elevated in sw MO may become surface based as they move ne and the warm front moves northward.  SPC expects initiation in the Midwest earlier today than back west in OK/TX area as mentioned in the discussion.  

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Between the upcoming outlooks at 1630, 2000, 0100 UTC in the evening. I really think an Moderate Risk for tornadoes is needed along the Ohio River from S OH to MO/AR.  I just got an feeling this could get bad. Even though people think today looks marginal, there is very high potential for widespread strong to severe thunderstorms from OK/N TX to W PA through the overnight

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Mesoscale Discussion 0577
   NWS Storm Prediction Center Norman OK
   0110 PM CDT Fri Apr 28 2017

   Areas affected...southeast Missouri and into southern portions of
   Illinois and Indiana and vicinity

   Concerning...Severe potential...Watch possible 

   Valid 281810Z - 282015Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Elevated storms developing over the southeast Missouri
   vicinity should gradually increase in coverage, and pose a severe
   risk -- mainly in the form of large hail.  WW may be required in the
   next 1-2 hours.

   DISCUSSION...Latest radar loop shows storms increasing across the
   southeast MO vicinity, likely associated with a zone of ascent
   associated with a weak/subtle wave evident in water vapor imagery
   moving northeast across eastern portions of KS/OK and into MO at
   this time.  A slow increase in storm coverage and intensity is
   expected over the next few hours given gradual mid-level
   destabilization in conjunction with the existing, amply sheared
   environment (and as hinted at by visible imagery and the latest HRRR
   runs).  As such, we will continue to monitor convective evolution
   and need for a possible WW.  Though risk would likely remain
   primarily hail, any storm development farther south -- i.e. nearer
   the warm front -- would require additional attention, with respect
   to possible surface-based severe risk.  While capping (with respect
   to a surface-based parcel) is expected to persist, we continue to
   monitor areas near/south of the boundary as well -- i.e. eastward
   across western and into central KY and vicinity.

   ..Goss/Grams.. 04/28/2017

mcd0577.gif

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Public Information Statement
National Weather Service Paducah, KY
800 PM CDT Thu Apr 27 2017

...NWS DAMAGE SURVEY FOR April 26 2017 TORNADO EVENT...

.Hickman - Graves County Tornado...

Rating:                 EF-1
Estimated peak wind:    95 mph
Path length /Statute/:  12.5 miles
Path width /Maximum/:   150 yards
Fatalities:             0
Injuries:               0

Start date:             April 26 2017
Start time:             712 PM CDT
Start location:         4.6 miles southeast of Clinton, KY

End date:               April 26, 2017
End time:               730 PM CDT
End location:           3.2 miles north northeast of Wingo, KY

At least 3 dozen homes and buildings sustained minor to moderate
damage consisting primarily of loss of shingles, siding and trim.
One home lost about a third of its roof and another had the back
porch blown off. A large chicken house lost approximately one
fourth of its roof structure. Several smaller outbuildings or
garages were destroyed. Hundreds of trees and tree limbs were
blown down. Four eyewitnesses reported seeing the tornado near
Fulgham. Most of the damage was concentrated around and just north
of Fulgham. The tornado weakened somewhat as it moved into Graves
County and the damage track became more intermittent there.

Straight line wind damage with peak winds up to 80 mph was
observed in areas adjacent to the tornado track.
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3 hours ago, Hoosier said:

LOT is calling for record flooding on some area rivers.  Obviously will depend on realizing some of those higher end amounts.

I'm not so sure I would be that aggressive yet just on models

record flooding from Morris to Henry and 29.0 feet here at PIA which would be the 3rd highest I believe

all locations are well below flood stage now

the heavy rain band would have to fall perfectly in the basin ....I'm not sure how much they are expecting to fall(I wish they would release that info when they make the river forecast) but a general 3-5 inch expected in other statements....IMO it would have to be more then 3-5 to get to those stages

This is assuming the bullseye won't shift 50-100 miles south 

translation: unless everything is perfect Huge bust potential

 

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