June 11-17th Severe Weather

[homedis]

kamala.cod.edu/spc

I found it and deleted my comment, but thank you!!

[Stebo]

Glad they extended the Slight into Southern MI as well, I think there could be a chance of stuff during the afternoon along the moisture surge/pseudo warm front into the state. Most CAMs have been hinting at the potential, obviously the squall line later in the evening would be the bigger story potentially.

[Chicago Storm]

ARW is very siggy...

[hlcater]

After looking at model runs(especially on the NAM and NAM 3km) I have decided that the variable that will most likely make or break saturday is the organization of the convection Friday evening. If we get only 1 MCS/disorganized mulicell activity and it is confined over western IA, atmosphere should be able to recover. However, if we get more than 1 MCS or a strong cold pool, which would overrun most of the would-be warm sector, Saturday is likely to get shunted further south and east. This scenario is evident on the 00z NAM. Location and to a lesser extent intensity of saturday hinges on what storm mode transpires tomorrow evening.

[Stebo]

21 minutes ago, Chicago Storm said:

ARW is very siggy...

Usually the NMMB is the one that goes hard, so this is certainly something to monitor, as the ARW is normally subdued a bit.

[Stebo]

29 minutes ago, NWLinnCountyIA said:

After looking at model runs(especially on the NAM and NAM 3km) I have decided that the variable that will most likely make or break saturday is the organization of the convection Friday evening. If we get only 1 MCS/disorganized mulicell activity and it is confined over western IA, atmosphere should be able to recover. However, if we get more than 1 MCS or a strong cold pool, which would overrun most of the would-be warm sector, Saturday is likely to get shunted further south and east. This scenario is evident on the 00z NAM. Location and to a lesser extent intensity of saturday hinges on what storm mode transpires tomorrow evening.

Early HRRR runs out to 22z favor one MCS at that point in Northern IA.

[hlcater]

1 minute ago, Stebo said:

Early HRRR runs out to 22z favor one MCS at that point in Northern IA.

Doesn't look horribly organized either, which would be a good sign. But its also the HRRR at FH18, so take that with a grain of salt.

[Stebo]

Just now, NWLinnCountyIA said:

Doesn't look horribly organized either, which would be a good sign. But its also the HRRR at FH18, so take that with a grain of salt.

Yeah, it could easily change next run, but it is a view at this point going out.

[Paulie21]

Interning for Gilbert over the weekends so I'll have to convey uncertainty of what might happen. 
Anyway, Gil sounded pretty concerned and excited (to maybe chase) initial discrete potential. No doubt this thing will blow up into a beefy MCS eventually but that time window between initiation and MCS is up in the air between pattern recognition and CAMs. 
We'll see how next couple model suites will deal with sfc low placement and how much it deepens. Pressure falls will induce low level backing and give sky high eff. inflow layer helicities, however, if the flow will be more veered, storm mode should be pretty messy. Though Thundersnow12 said it reminds him of 6/12/13. Somewhat agree. Even with veered flow, with westerly jet aloft there could still be plenty shear for initial sups. 
Storm morphology will be everything.

[Tim from Springfield (IL)]

Might as well extend this thread to Sunday--SPC D3 includes a slight that includes SE OH/W PA/E KY:

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

 

...SUMMARY...
   Strong thunderstorms, mainly accompanied by the risk for potentially
   damaging wind gusts, are possible Sunday afternoon and evening
   across the lower Great Lakes region and upper Ohio Valley into the
   Cumberland Plateau.

   ...Discussion...
   While a subtropical high becomes increasingly prominent across the
   Four Corners region, models suggest that ridging within the
   mid-latitude westerlies may continue to build as it shifts inland of
   the British Columbia and Pacific Northwest Coast during this period.
   Downstream, further amplification of troughing may occur east of the
   mid/upper Mississippi Valley, between the western ridging and
   ridging within the subtropics and mid-latitude westerlies over the
   western Atlantic.  A mid-level closed low is forecast to develop
   over northwest Ontario, within the upper troughing, as low-level
   cyclogenesis proceeds northeast of the Great Lakes region.  

   Associated with the cyclone, a trailing cold front may advance into
   the lower Great Lakes region, the Ohio and middle Mississippi
   Valleys and the central Plains by late Sunday night.  However, even
   by early Sunday, it may be preceded by a significant conglomeration
   of convectively generated outflow, from portions of the lower Great
   Lakes and Ohio Valley into the south central Plains.

   This lead boundary may provide the primary focus for destabilization
   and strongest thunderstorm development Sunday through Sunday night. 
   It appears likely to tend to spread east and south of the stronger
   cyclonic mid/upper flow, but models do continue to indicate the
   potential for moderately large CAPE (1500 to as high as 3000 J/kg)
   to develop within a corridor along and ahead of it by Sunday
   afternoon.  This is expected to be sufficient to support
   thunderstorms accompanied by at least some risk for severe weather
   potential, and this could still be aided by 30-40 kt
   south/southwesterly flow in the 850-700 mb layer, particularly
   across parts of the Ohio Valley/Cumberland and Allegheny Plateau
   region into the lee of the lower Great Lakes.  This is where severe
   probabilities appear highest at the moment (mostly for potentially
   damaging winds), and sufficient for a categorical slight risk, aided
   by general difluent/divergent upper flow downstream of the
   amplifying upper troughing.

   Severe potential is still less certain across parts of the Tennessee
   Valley into the south central Plains, even as the remnant plume of
   elevated mixed layer air across this region erodes with mid-level
   cooling.  CAPE may initially be higher across this region though, in
   the presence of steeper mid-level lapse rates.  Once sub-synoptic
   developments/features become better resolved, it seems possible that
   severe probabilities may be increased (generally for severe hail and
   wind) across at least parts of this region in subsequent outlooks
   for this time period.

   ..Kerr.. 06/16/2017

[cyclone77]

Nice little snippet from DVN this morning..

Saturday/Saturday evening: A potent severe weather situation
appears to be shaping up for the afternoon and early evening
hours. SPC has an enhanced risk for much of the dvn cwa as a
deepening upper level trough/stronger cold front arrives. There
is the potential for a derecho or at least bowing segments forming
into a mature bowing squall line, along with possible spin-up
tornadoes (mesovortices). With the strong heating/instability and
mid level winds of 70-75 knots, there is the potential for 70-80+
mph very damaging winds. Highs will be in the 80s to lower 90s,
with heat index values in the mid to upper 90s, mainly south of
Interstate 80.

[Chinook]

NCAR short-term ensemble members have a few solutions that significantly impact Chicago tomorrow. Here is (maybe) the worst looking ensemble member at 22z tomorrow. The next hour (23z) shows a small-scale bow echo in Chicago.

 

[Stebo]

2 minutes ago, Chinook said:

NCAR short-term ensemble members have a few solutions that significantly impact Chicago tomorrow. Here is (maybe) the worst looking ensemble member at 22z tomorrow. The next hour (23z) shows a small-scale bow echo in Chicago.

 

You have a link to that model?

[IllinoisWedges]

3 minutes ago, Stebo said:

You have a link to that model?

https://ensemble.ucar.edu/images.php?d=2017061600&f=td2_mean&r=NGP

[Stebo]

Just now, IllinoisWedges said:

https://ensemble.ucar.edu/images.php?d=2017061600&f=td2_mean&r=NGP

Thanks

[Hoosier]

Variety of CAM solutions/viable outcomes doesn't inspire a ton of confidence for greatest threat area tomorrow.

[CheeselandSkies]

Looks like another 2017 convective mess forthcoming. Not nearly as enthused about chase prospects as I was 24 hours ago. Updated Day 2 is first valid for Saturday to even use the "T" word and only because it's Broyles.

[Chinook]

I always take a good look at the NSSL WRF, on Pivotalweather, because that seems to be kind of accurate in the 21-24 hour time frame. The 36-hr forecast from the NSSL-WRF has nothing in N. Illinois tomorrow afternoon. Of course, it cuts off at 36hr so there's no info at 37hr or 38hr. It has a bunch of storms in the St. Louis to central MO corridor.

[AppsRunner]

Watch being coordinated for Northern IA, far southern MN, and SW WI. Should be out in a minute

[homedis]

Really nice write-up by LOT at ~2pm (don't think anyone posted this yet)

 

 
"By late afternoon into the early evening, large scale ascent
really ramps up across the region. This is in response to digging
upper level trough with strong upper jet moving overhead, and with
increasing mid level energy and flow. This increase in upper
level flow, which will include flow at 500mb approaching 70KT or
higher, will support bulk layer shear quickly ramping up by early
evening to more than enough values supportive of organized
development. Attendant surface low expected to quickly deepen
during this time, with overall setup then favoring an increase in
thunderstorms. This is as most guidance is in agreement with
moderate/strong instability to be in place during this time.
However, situation gets really complicated, with low confidence
still in place for placement of this low and general surface
pattern. Increase in coverage likely during this time/evening,
with main development expected to be in and around surface low and
associated boundaries. Once again, confidence as to where this
main development will occur is low at this time. This is key as do
think initial thunderstorms will have the potential to be
discrete, with the quickly increasing wind fields. Soon there
after, setup would then favor a transition over to more linear
convection. A wind threat, quite possibly higher end, would then
be the more probable hazard in the evening. Given the extent of
the potential instability, large hail will also be possible, along
with heavy rainfall and localized flooding.
 
With low confidence as to the surface pattern and initiation,
don`t want to really put any focus on any one area across the CWA.
At this time, these hazards appear possible across the entire
area. The threat of storms and these hazards could continue
through late in the evening and quite possibly into a portion of
the overnight hours, before exiting the area. Area depicted by
SPC`s SWODY2 including the elevated risk area still appears valid
given the potential setup and also the uncertainty. After whatever
precip develops and then evolves tonight into early Saturday
morning, a more refined threat area including the main threats
should hopefully be realized.
 
Rodriguez"

[Harry Perry]

Excellent disco by LOT. Really hit the nail on the head. On the other side of the lake GRR is not nearly as impressed with tomorrow at all - even only mentioning an "isolated severe storm" amongst lots of convective debris limiting instability.  I do believe they make a good point about the potential lack of instability, however, being in the right entrance region of a 40-50kt LLJ, forcing from an approaching front and dews in the upper 60's to around 70 - I feel if our highs bust and only end up being 80° vs our progd 88°, temps would still be more than suffiencent for a potential severe weather event, especially after 18z. 

 

A good potential event to keep an eye on for sure. Main issue was convection this evening overturning the atmosphere for tomorrrow and that has not panned out - yet anyway. Guess we'll see.

[HillsdaleMIWeather]

19 minutes ago, Harry Perry said:

Excellent disco by LOT. Really hit the nail on the head. On the other side of the lake GRR is not nearly as impressed with tomorrow at all - even only mentioning an "isolated severe storm" amongst lots of convective debris limiting instability.  I do believe they make a good point about the potential lack of instability, however, being in the right entrance region of a 40-50kt LLJ, forcing from an approaching front and dews in the upper 60's to around 70 - I feel if our highs bust and only end up being 80° vs our progd 88°, temps would still be more than suffiencent for a potential severe weather event, especially after 18z. 

 

A good potential event to keep an eye on for sure. Main issue was convection this evening overturning the atmosphere for tomorrrow and that has not panned out - yet anyway. Guess we'll see.

Yeah, so far tonight it's much clearer than models we're progging 

[hawkeye_wx]

It's out of our subforum, but the Omaha NWS office just recorded an 88 mph wind gust.

[AppsRunner]

43 minutes ago, HillsdaleMIWeather said:

Yeah, so far tonight it's much clearer than models we're progging 

Still plenty of time for that to change with the LLJ kicking in. Will likely see a substantial MCS continue through tonight, but how much airmass recovery we get still remains a giant question mark. Recent trends have been to slow down/amplify the shortwave digging into the midwest, which should allow for a few more hours of recovery. It will be interesting to see how SPC plays it tonight. 

 

May end up chasing tomorrow since it's not too much of a drive.

[Hoosier]

1 hour ago, hawkeye_wx said:

It's out of our subforum, but the Omaha NWS office just recorded an 88 mph wind gust.

There was actually a measured 110 mph gust out that way.  One of the highest reports I've ever seen in an LSR and not a post-storm survey.

[homedis]

2 minutes ago, Hoosier said:

There was actually a measured 110 mph gust out that way.  One of the highest reports I've ever seen in an LSR and not a post-storm survey.

Wow, that's insanely powerful

[Radtechwxman]

So does anyone think the substantial outflow from the event tonight will push tomorrow's threat south? Some hi res models are hinting at this. Not building the cape as far north. 

[homedis]

So does anyone think the substantial outflow from the event tonight will push tomorrow's threat south? Some hi res models are hinting at this. Not building the cape as far north. 

 

 

Personally, I dont think the threat necessarily could be "pushed" south but could rather inhibited up north due to the convection/clouds tomorrow. But I'm honestly not sure what will end up happening, it seems like there should be adequate recovery tomorrow afternoon. Maybe some other more experienced members can chime in.

[OceanStWx]

In the FWIW category, the 00z NAM did fairly correctly initiate convection across the MO Valley and wipes out a big chunk of theta-e overnight. That being said, it also recovers the high theta-e air mass into parts of central/eastern IA by 21z. So based on that model forecast, recovery shouldn't be a problem as long the complex is somewhere south of I-70 by 12z tomorrow morning.

[homedis]

In the FWIW category, the 00z NAM did fairly correctly initiate convection across the MO Valley and wipes out a big chunk of theta-e overnight. That being said, it also recovers the high theta-e air mass into parts of central/eastern IA by 21z. So based on that model forecast, recovery shouldn't be a problem as long the complex is somewhere south of I-70 by 12z tomorrow morning.

That complex is moving at 65mph so that shouldn't be a problem haha.