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Late April-Early May Heavy Rain/Severe Possibilities


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Also a Slight Risk today including part of MO:

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

Wednesday looking interesting in at least the south part of this subforum--SPC has a hatched area from AR all the way to St. Louis (Enhanced Risk), with most of central/S IL in Slight:

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

...Southern Plains and lower to middle Mississippi Valley...

   Strengthening low-level jet induced by the approaching shortwave
   trough will advect mid to upper 60s F boundary-layer dewpoints
   through the pre-frontal warm sector beneath 7-7.5 C/km mid-level
   lapse rates. These processes will contribute to moderate instability
   with 1500-2500 J/kg MLCAPE, despite the potential for widespread low
   clouds which will limit diabatic warming in some areas.
   Thunderstorms will likely be in progress within baroclinic zone and
   along warm conveyor belt from portions of OK into MO, and some of
   this activity could pose an ongoing modest risk for a few strong
   wind gusts and hail. However, primary development of severe storms
   is expected during the afternoon as storms intensify along and just
   ahead of the cold front and in association with a destabilizing warm
   sector. Strong dynamic forcing for ascent within frontal zone
   augmented by the negatively tilted shortwave trough and
   strengthening low-level jet will likely result in the initiation of
   numerous storms and an eventual upscale linear growth. Strong
   deep-layer winds, vertical shear and large low-level hodographs will
   favor organized storms including embedded supercells and bowing
   segments, with all severe hazards possible. 

   ...Illinois into the Great Lakes...

   Instability and low-level moisture will be less in this region
   compared to farther south but sufficient for an organized severe
   threat given favorable wind profiles. The stronger storms will
   likely expand into this region during the late afternoon and
   evening, with a few supercells and bowing linear segments capable of
   damaging wind, large hail and a couple of tornadoes.

   ..Dial.. 04/25/2017
 

Then marginal on Thursday before most of the severe possibilities appear to be to our south, or even in the southern fringes of our subforum, for the weekend.

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Enhanced area shifted north into SW IL for tomorrow.

Quote

  Day 2 Convective Outlook 
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Tue Apr 25 2017

   Valid 261200Z - 271200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS ARKANSAS
   AND INTO SOUTHERN MISSOURI AND SOUTHWEST ILLINOIS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE ARKLATEX
   AND LOWER MISSISSIPPI VALLEY NORTHWARD INTO ILLINOIS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IMMEDIATELY
   SURROUNDING THE SLIGHT RISK AREA...

   ...SUMMARY...
   Severe thunderstorms with damaging winds, a few tornadoes and some
   hail are expected across much of Arkansas and southern Missouri
   Wednesday. Isolated severe thunderstorms with damaging wind are also
   expected across Illinois during the day and across the lower
   Mississippi Valley overnight.

   ...Synopsis...
   A potent shortwave trough will move from the southern Plains
   northeastward across the middle MS valley with a surface trough
   extending from WI into AR at 00Z. Strong large-scale lift will exist
   resulting in widespread strong to severe thunderstorm activity
   throughout the day.  The most intense storms are expected over AR
   and across southern MO, beneath strong southwesterly flow aloft with
   activity focused along the advancing front. All modes of severe will
   be possible, with damaging wind the most prominent threat. A few
   strong bows may trek northeastward across much of Illinois as well.
   Southern portions of this front will progress across the lower MS
   valley overnight, focusing a damaging wind threat into MS and
   western TN with a slowly decreasing threat with eastward extent.

   ...Arklatex northeastward across Illinois...
   Storms are expected to be ongoing Wednesday morning along an
   outflow/front composite boundary extending from eastern OK into
   southwest MO. This activity should be elevated with hail, but
   damaging wind will also be possible with storms right on the
   boundary. With time, lift along the front will intensify as cooling
   aloft overspreads the area and the air mass destabilizes further.
   Strong mean winds and linear forcing suggest damaging serial bows
   are possible. Depending on storm motion relative to boundary
   orientation, a few storms could rotate with a tornado threat as
   low-level shear will remain sufficient and moisture will be
   abundant, especially over AR. A 50 kt low-level jet will extend
   northward into IL as well, supporting a few fast-moving bows into
   that area during the day. Instability will wane with northward
   extent, however, the favorable synoptic setup could yield severe
   wind to Chicago.

   ...Lower Mississippi Valley...
   A cold front/outflow boundary is likely to progress eastward across
   the lower MS valley Wednesday evening into the night, with a
   continued damaging wind threat. While the strongest activity should
   remain to the northwest closer to the main shortwave trough, ample
   moisture and instability will remain across the region. Some capping
   inversion is expected to precede the front, which should limit any
   severe storms to the squall line. As such, any tornado threat should
   be low/brief, as low-level winds will be more veered closer to the
   front where storms will exist. Storms should generally weaken into
   AL into Thursday morning, with the best chance of isolated damaging
   gusts across southern portions where instability will be greatest.

   ..Jewell.. 04/25/2017

 

day2otlk_1730.gif

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worried about flooding here....although its been dry the past week or so the IL river is still rather high from the wet start of the month..soil moisture is above average in NE IL

usually outflows will cause the set up to be a little more SE then modeled..the areas along the OH river seems to get these extreme rain events more then north central IL

one expection was april of 2013  that caused record flooding on the IL river here..when areas from PIA to ORD got back to back training events within  few days

If someone could post the EURO total precip from this morning that would be great

 

looks the the 1st event will could be the primer for this wekend

 

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Day 2 Outlook

  ..OHIO VALLEY AND GREAT LAKES     THE FEED OF RICHER LOW-LEVEL MOISTURE WILL BECOME LIMITED AS THE   CYCLONE OCCLUDES OVER THE GREAT LAKES REGION. HOWEVER, AT LEAST   MARGINAL INSTABILITY WITHIN A STRONG SHEAR ENVIRONMENT WILL EXIST IN   PRE-FRONTAL WARM SECTOR, AND STORMS MIGHT POSE SOME RISK FOR A FEW   INSTANCES OF ISOLATED DAMAGING WIND GUSTS AND HAIL AS THEY DEVELOP   EAST DURING THE DAY. THIS REGION WILL ALSO BE MONITORED FOR A   POSSIBLE SLIGHT RISK IN LATER UPDATES.    

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6 minutes ago, HillsdaleMIWeather said:

Nope, I think they actually did the opposite.

Removed the slight risk out of almost all of Illinois due to instability concerns. Definitely a potential issue.  I think the ongoing convection could push the severe threat east of earlier thinking, so if the slight risk comes back, it may come northeastward into parts of Indiana.  Make sense?  lol

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Friday (D3) bears watching in the south part of this sub--slight risk roughly along/S of I-70 in IL/IN, and in S MO, with enhanced reaching S IL and SE MO:

http://www.spc.noaa.gov/products/outlook/day3otlk.html

...Southern Plains through the Tennessee and Ohio Valleys...

   Shortwave trough will shift northeast through the OH Valley early
   Friday with upstream height rises in wake of this feature from the
   southern Plains into the TN Valley. A warm front will develop
   northward and by early evening should extend from the southern OH
   valley into northern TX or southern OK with a dryline evolving
   across west-central into northwest TX where it will intersect the
   front. Limited synoptic forcing for ascent and capping due to
   eastward expansion of EML may limit thunderstorm initiation during
   the day over much of this region. Some chance for initiation will
   exist at the intersection of dryline and front over northwest TX by
   late afternoon. Large CAPE and strong vertical shear would favor a
   conditional risk for supercells with very large hail and a few
   tornadoes should such initiation occur. Rich low-level moisture with
   large CAPE will reside south of warm/Quasistationary front. The best
   chance for more widespread thunderstorm initiation will occur during
   the evening into the overnight from OK into northern AR, MO and into
   the TN and OH valleys along and north of the warm front as
   strengthening, broad low-level jet enhances convergence and
   isentropic ascent along and north of this boundary. Strong vertical
   shear profiles and instability will support organized storms
   including supercells with large hail and damaging wind the main
   threats, though a few tornadoes may also occur with surface-based
   storms developing closer to the warm front.

   ..Dial.. 04/26/2017
 

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5 hours ago, KokomoWX said:

I've been seeing some impressive wind gusts on the euro for Sunday and Monday.  

Monday.jpg

Sunday.jpg

The post frontal period early next week may be mildly interesting if the system deepens as much as shown.  Trees leafed out with what will be wet soils.

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2 minutes ago, Hoosier said:

The GEM is crazy.  Band of 8-10" from ORD through STL.

Pretty good snowstorm, oh wait you are talking about rain haha. In all seriousness though someone in Missouri and Illinois will get crushed with this system starting today.

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