Late April-Early May Heavy Rain/Severe Possibilities

[janetjanet998]

7 minutes ago, RCNYILWX said:

Wanted to offer comment on the very high river forecasts that went out. This is not meant to throw the North Central River Forecast Center under the bus. However, all forecasts for this area are issued by NCRFC in collaboration with NCRFC. They decided to go with 72 hour qpf for this event to catch the storm total but the qpf used in their forecast hydrographs yesterday was extremely high. They went with that bullish forecast and we didn't have too much advanced notice of it, but what we did do is go with flood watches instead of warnings because the forecasts are entirely qpf driven. In hindsight, we could have done a better job of working with NCRFC to play things more conservatively to start out and then adjust upward as trends became more clear. For example, perhaps we could've requested to just use 48 hour qpf, or to adjust the qpf for the models down 25% or thereabouts. Given the potential impacts of the stages being forecast, I definitely understand the angst and criticism, especially if it doesn't work out due to convection south robbing the moisture transport.

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Ok thanks for your input...I thought something was fishy...

In the past the river forecast has said observed rainfall and forecast rainfall the next 24 hours

a couple questions 

1) how much rainfall was in the extremely high forecast to get to those levels(so we can determine if there's a chance for those levels)

2) do your river forecast usually take into account the nex 24 hours or 48 hours expected qpf

thanks in advance

[Hoosier]

6 minutes ago, RCNYILWX said:

Wanted to offer comment on the very high river forecasts that went out. This is not meant to throw the North Central River Forecast Center under the bus. However, all forecasts for this area are issued by NCRFC in collaboration with NCRFC. They decided to go with 72 hour qpf for this event to catch the storm total but the qpf used in their forecast hydrographs yesterday was extremely high. They went with that bullish forecast and we didn't have too much advanced notice of it, but what we did do is go with flood watches instead of warnings because the forecasts are entirely qpf driven. In hindsight, we could have done a better job of working with NCRFC to play things more conservatively to start out and then adjust upward as trends became more clear. For example, perhaps we could've requested to just use 48 hour qpf, or to adjust the qpf for the models down 25% or thereabouts. Given the potential impacts of the stages being forecast, I definitely understand the angst and criticism, especially if it doesn't work out due to convection south robbing the moisture transport.

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Thanks for the info.

[janetjanet998]

2013 record IL river flood event

 

 

 

[janetjanet998]

New crest for PIA on the IL river is 26.6 feet down from 29.0 which makes alot more sense for now

 

Henry 30.8 down from 33

Lasalle around 31 down from the record 36.5

 

[Chambana]

Whiffed to the north and south.  1.2" here. 

[RCNYILWX]

Ok thanks for your input...I thought something was fishy...

In the past the river forecast has said observed rainfall and forecast rainfall the next 24 hours

a couple questions 

1) how much rainfall was in the extremely high forecast to get to those levels(so we can determine if there's a chance for those levels)

2) do your river forecast usually take into account the nex 24 hours or 48 hours expected qpf

thanks in advance

1) I think the mosaicked basin average qpf had widespread 4-6" basin average amounts. There might be a way to check that on NCRFC page but not sure.

2) Most often, 24 hour qpf is used, with 48 hour some of the time and in rare cases 72 hour because qpf is so fickle/tough to forecast accurately. That's also a good reason why 48 hour may have been a better choice for this event.

[janetjanet998]

44 minutes ago, RCNYILWX said:

 

1) I think the mosaicked basin average qpf had widespread 4-6" basin average amounts. There might be a way to check that on NCRFC page but not sure.

2) Most often, 24 hour qpf is used, with 48 hour some of the time and in rare cases 72 hour because qpf is so fickle/tough to forecast accurately. That's also a good reason why 48 hour may have been a better choice for this event.

 

ok thanks

well this first wave seems like perfect hit a meso low thing is NW of STL moving ENE and a warm front feature has training storms and heavy rain right over me and moving NE

[RCNYILWX]

ok thanks

well this first wave seems like perfect hit a meso low thing is NW of STL moving ENE and a warm front feature has training storms and heavy rain right over me and moving NE

Yeah, looks like you'll end up with hefty totals there. Thankfully though it's been wet overall, it had been relatively quiet over the past week or so.

[Central Illinois]

Quarter size hail/60mph winds here in Mt Zion came down in buckets also had another inch of rain.. still raining moderately


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[cyclone77]

the HRRRx has a decent triple point play for tomorrow afternoon.  The main morning precip bumps far enough east to allow for some destabilization ahead of the incoming triple point.  It forecasts 500-1000J/kg surface cape immediately ahead of an arc of convection associated with the TP/cold front.  Very conditional setup, but it won't take much to develop that kind of cape and it should be enough given the strong dynamics.  Right now the area from northeast MO up through far southeast IA/west-central IL is looking pretty nice per the HRRRx.  Basically wherever the triple point ends up tracking is the place to be the way it looks at this point.   

[DaveNay]

Riiiight. What's a Cubit?

[janetjanet998]

3 to 3.5 inches around the area

 

 

Doppler radar really underestimating precipitation

[SchaumburgStormer]

Brutal drive home from peoria this evening. Multiple flooded roads, along with heavy rain and high winds making visibility near zero at times. Driving the interstate made it feel like mid-winter driving conditions, with the average speed of traffic <45mph.

 

2.00" on the nose today. 

[Hoosier]

Not completely sold on the severe threat around here tomorrow, but it looks tantalizing enough.  Guidance is suggesting perhaps a few hour break tomorrow afternoon.  Question on just how far north the warm front gets and it's possible it hangs around here somewhere until early evening.  Certainly will have enough low level shear to play with for some tornado risk.

[HillsdaleMIWeather]

40 minutes ago, Hoosier said:

Not completely sold on the severe threat around here tomorrow, but it looks tantalizing enough.  Guidance is suggesting perhaps a few hour break tomorrow afternoon.  Question on just how far north the warm front gets and it's possible it hangs around here somewhere until early evening.  Certainly will have enough low level shear to play with for some tornado risk.

Could easily be an over or under performer, quite tricky forecast and all details won't be clear until at least morning.

[cyclone77]

1 hour ago, Hoosier said:

Not completely sold on the severe threat around here tomorrow, but it looks tantalizing enough.  Guidance is suggesting perhaps a few hour break tomorrow afternoon.  Question on just how far north the warm front gets and it's possible it hangs around here somewhere until early evening.  Certainly will have enough low level shear to play with for some tornado risk.

These conditional setups are pretty frustrating since you can't really get too deep into analyzing anything until the day of.  I haven't chased since the backyard Feb 28th event and have been looking forward to getting back out.  The conditional nature of this event means that I still don't know if I'm heading out tomorrow or not.  The triple point play is probably worth a gamble even if it's looking sort of meh tomorrow morning.  I've become kind of picky in the last few years or so, so unless it's looking fairly decent I'll probably sit out yet again lol.

[HillsdaleMIWeather]

Day 1 Slight Risk, expanded way north

[Hoosier]

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1241 AM CDT Sun Apr 30 2017

   Valid 301200Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY AND TONIGHT
   NEAR/EAST OF THE MISSISSIPPI VALLEY THROUGH PORTIONS OF THE SOUTHERN
   GREAT LAKES...LOWER OHIO VALLEY AND CENTRAL GULF STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS AREAS
   SURROUNDING THE SLIGHT RISK...

   ...SUMMARY...
   Severe thunderstorms are possible today into tonight, from the
   vicinity of the Mississippi River eastward through portions of the
   the southern Great Lakes region, lower Ohio Valley and central Gulf
   states.  This includes a risk for storms capable of producing
   tornadoes, a couple of which could be strong.

   ...Synopsis...
   Models indicate that a belt of westerlies emanating from the
   mid-latitude Pacific will remain amplified through this forecast
   period, with large-scale ridging across the eastern Pacific into the
   Pacific coast, and across the Atlantic Seaboard into the western
   Atlantic, and large-scale troughing over much of the interior United
   States.  The large-scale troughing appears likely to take on an
   increasing negative tilt orientation, as a significant embedded
   short wave perturbation pivots northeast out of the central and
   southern Plains through the Mississippi Valley by late tonight.

   Substantive further deepening of a lower/mid tropospheric cyclone is
   forecast as it tracks northeast of the southern Plains.  At the
   surface, the low may occlude early in the period across and
   northeast of the lower Missouri Valley, with secondary low
   development likely migrating across northeastern Missouri through
   northern Illinois this afternoon and evening.

   Within the potentially broad warm sector of the cyclone, models
   indicate 50-70 kt southerly 850 mb will develop near/east of the
   Mississippi Valley today.  The core of a 100+ kt south/southwesterly
   500 mb jet may lag to the west of the warm sector, but mid/upper
   flow fields above the warm sector should still be more than
   sufficient to support potential for organized severe storm
   development, including supercells.

   Uncertainties abound concerning the extent to which thermodynamic
   profiles within the warm sector will become conducive to severe
   weather potential.  It appears that the northeastward advection of
   elevated mixed layer air will become disrupted or cut-off from much
   of the warm sector, and with the mid-level cold core lagging to the
   west of the surface cold front, mid-level lapse rates are not
   expected to become particularly steep.  Furthermore, considerable
   remnant pre-frontal convective development/cloud cover may be
   present early in the period, and drying associated with ridging
   centered off the Atlantic coast appears likely to slow boundary
   layer moistening across much of the Southeast into portions of the
   Ohio and Tennessee Valleys.

   ...Mississippi Valley to western slopes of the Appalachians...
   Taking into account the preceding discussion, uncertainties seem too
   large to allow for more than an outlook of a categorical slight risk
   at the present time.  But given the strength of the synoptic system
   and associated wind fields, and at least a corridor of pre-frontal
   boundary layer moisture characterized by surface dew points in the
   mid 60s to near 70F, it may not be out of the question that a window
   of opportunity for considerable severe weather potential could
   develop this afternoon and evening.  This seems mostly likely to be
   focused near or just east of the Mississippi Valley, and mostly in
   the wake of an initial north/south oriented band or two of
   thunderstorms spreading east of the Mississippi Valley, where
   guidance appears suggestive that breaks in the overcast could allow
   insolation to contribute to at least pockets of mixed layer CAPE on
   the order of 1000-2000 J/kg.  Of particular concern is that the
   environment could become conducive to at least isolated to widely
   scattered long lived discrete supercell development, initially
   anywhere from portions of eastern Missouri into Illinois, southward
   through portions of western Kentucky and Tennessee into northern
   Mississippi.  In the presence of clockwise curved low-level
   hodographs characterized by strong to extreme shear, some of these
   could become capable of producing strong tornadoes.

   It is possible thunderstorm activity could eventually consolidate
   into one or two organized eastward advancing lines, into portions of
   the southern Great Lakes region, and across the central Gulf states
   by late this evening.

   ..Kerr/Gleason.. 04/30/2017

[Stebo]

Some of the CAMs for tomorrow are pretty interesting across IL/IN and even Southern MI. Might be something where I take a roll down to the border if it looks decent enough tomorrow morning.

[Chicago Storm]

Today no longer looks interesting, or even chase worthy.

Way too much convective and cloud debris over the warm sector.

[Chicago Storm]

Likely was some sort of wake low feature with the MCV that moved across NE. IL last evening/night.

 

It enhanced rainfall and brought a period of wind gusts in the 40-60MPH range, along with some damage in the metro.

[cyclone77]

8 minutes ago, Chicago Storm said:

Today no longer looks interesting, or even chase worthy.

Way too much convective and cloud debris over the warm sector.

Since there's nothing in the next 7+ days I'm still considering heading for the triple point and hope for the best lol.  Cape looks very meager at maybe 500J/kg, but hoping it will be enough considering the environmental setup today.  If anything it will be nice to get out of this 40 degree awfulness we've had the last several days.  That in itself would be worth it lol.

Thinking of heading down to a little south of Macomb and meet up with the TP.  If something can fire a bit further east along the WF that may be worth a look as well, but TP would prob be the best play as there will likely be a little instability ridge it will feed off of.  

[janetjanet998]

The current river in MO is smashing 100 year old record crests in some places

 

[SchaumburgStormer]

11 minutes ago, janetjanet998 said:

The current river in MO is smashing 100 year old record crests in some places

 

 

[Hoosier]

1 hour ago, Chicago Storm said:

Likely was some sort of wake low feature with the MCV that moved across NE. IL last evening/night.

 

It enhanced rainfall and brought a period of wind gusts in the 40-60MPH range, along with some damage in the metro.

Was wondering about that.  It suddenly got pretty windy here.

[Hoosier]

Not too surprising, there are sig changes on the 1630z outlook.

[vortex]

1 hour ago, Chicago Storm said:

Likely was some sort of wake low feature with the MCV that moved across NE. IL last evening/night.

 

It enhanced rainfall and brought a period of wind gusts in the 40-60MPH range, along with some damage in the metro.

Had several large trees down around here and power was out here for three hours.

It was like a mini tropical storm.  Odd seeing winds gusting that high from the Northeast.  

 

[IMADreamer]

10 inches here so far.  I'd say 70% of my corn is drowned out right now.  We made the mistake of going out yesterday to do some shopping.  What's normally a 45 minute drive took an hour and a half because of the closed roads.  At least the river situation looks much improved from yesterday although I understand from St. Louis south the smaller rivers are in bad shape. 

[nwohweather]

I'm shocked no one is talking about the severe chances here. Pretty good instability building in ahead of the shear in west Ohio.

Crazy weather here currently as well 53° at my house in Perrysburg, 78° 30 miles south of here in Findlay

[Jim Martin]