June 9-11 Severe/Heavy Rain Threats

[A-L-E-K]

catching up...looks like hi-res CAM initiate a potential MCS late tonight over the twin cities and then ride it SE along the favored track into northern illinois.

 

 

 

 

this could certainly complicate things for later Thursday, you can see how the instability / axis of deep moisture gets shunted south

 

[OHweather]

Feeling more comfortable with not chasing Saturday. What I would like to see for Thursday is the CAMs explicitly showing some attempt at convection. 6z 4km tried but failed. Izzi mentioned that the NAM/GFS may be running too high with dew points, so I'd be uncomfortable if the CAMs did show convection. Euro/GFS/NAM all do try.

[A-L-E-K]

we're definitely going to be dealing with ongoing morning/midday clutter across northern illinois on thursday

 

[ClicheVortex2014]

Friday's looking like an all-or-nothing day. Parameters are certainly there for a pretty good event, just not seeing any convection to fire up. This time of year, you can hold hope for either an outflow boundary to set up or a June 29-like scenario. I'm not holding my breath.

[Chitown Storm]

The models definitely jumped north with the precip this evening. Yesterday the main action was in Iowa but the last few runs have it well north of there into C MN. That might muck things up tomorrow downstream if a right turning MCS rolls thru.

[ClicheVortex2014]

Friday's looking like an all-or-nothing day. Parameters are certainly there for a pretty good event, just not seeing any convection to fire up. This time of year, you can hold hope for either an outflow boundary to set up or a June 29-like scenario. I'm not holding my breath.

This would be nice

 

 

Better than nothing. Literally, at least it initiates something. But it's not good when the only model that gives you hope is the 4km NAM.

[madwx]

An MCS may actually be helpful if it can leave behind an MCV or lay down a differential heating boundary to help kick off some storms and help with low level rotation. 

My two biggest concerns with tomorrow's setup are:

1) How much are models overdoing dewpoints and

2) What will be the trigger for storm formation

 

Mean storm motion will parallel to the warm front which will be good if you want sustained rotating surface based storms

[Hoosier]

An MCS may actually be helpful if it can leave behind an MCV or lay down a differential heating boundary to help kick off some storms and help with low level rotation. 

My two biggest concerns with tomorrow's setup are:

1) How much are models overdoing dewpoints and

2) What will be the trigger for storm formation

 

Mean storm motion will parallel to the warm front which will be good if you want sustained rotating surface based storms

 

 

Good point there. 

[A-L-E-K]

some of the 12z models are hinting at convection riding down the west shore of the lake saturday evening ahead of the pneumonia front

 

we've seen some nice events in the past from similar setups

[Hoosier]

NAM/GFS have an area of dewpoints in the low 70s by 00z Friday in parts of IL/WI.  Normally that wouldn't be too difficult to pull off at this point in June but dews will be starting off fairly low so we'll see.

[A-L-E-K]

NAM/GFS have an area of dewpoints in the low 70s by 00z Friday in parts of IL/WI.  Normally that wouldn't be too difficult to pull off at this point in June but dews will be starting off fairly low so we'll see.

 

 

crops are decent upstream, plus pooling, plus wet surfaces from likely convection early thursday...not unreasonable

[Geos]

back south

 

these subtle shortwaves are hard to pick up at range and always end up reinforcing the boundary further south, so i'd hedge on it being even further south than this

 

 

So I might be looking at stratiform rain with occasional thunder.

[Geos]

Pretty good complex late morning tomorrow.

 

 

Convection firing over the lake, that's interesting.

 

 

[Hoosier]

New day 2 outlook:

 

 

..UPPER MS VALLEY/WRN GREAT LAKES/NRN OH VALLEY    NORTHWEST MID-LEVEL FLOW IS FORECAST TO BE IN PLACE THURSDAY FROM  THE UPPER MS VALLEY SEWD ACROSS THE GREAT LAKES REGION. AT THE  SFC...A QUASI-STATIONARY FRONT SHOULD BE LOCATED FROM SRN MN SEWD  INTO NRN IL AND NRN IND. THIS BOUNDARY SHOULD BE THE FOCUS FOR  THUNDERSTORM DEVELOPMENT DURING THE LATE AFTERNOON AND EVENING.  FORECAST SOUNDINGS NEAR THE BOUNDARY AT 00Z/FRI FOR CHICAGO SHOW MID  60S F SFC DEWPOINTS AND MLCAPE NEAR 2000 J/KG. IN ADDITION...0-6 KM  SHEAR VALUES ARE FORECAST TO BE NEAR 30 KT WITH SOME DIRECTIONAL  SHEAR IN THE BOUNDARY LAYER. THIS WOULD BE FAVORABLE FOR MULTICELLS  WITH STRONG WIND GUSTS AND HAIL. STORMS THAT PERSIST INTO THE  EVENING MAY BECOME ELEVATED AS A CAPPING INVERSION RE-ESTABLISHES  ITSELF ACROSS THE REGION. DUE TO THE AMOUNT OF INSTABILITY AND  ADEQUATE SHEAR ENVIRONMENT...PARTS OF THIS AREA MAY NEED TO BE  UPGRADED TO SLIGHT RISK IN LATER OUTLOOKS.  

[chase_stormz]

Considering Broyles wrote the outlook I'm surprised that HE didn't upgrade to a slight risk and at least mention an isolated tornado as a possibility haha 

 

New day 2 outlook:

[ClicheVortex2014]

I'm more excited for Friday than Saturday, I think.

 

[A-L-E-K]

let's do this, geos

 

[ajcaras2013]

Most recent forecaster's discussion from CLE office...

 

 

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/...

As if often the case, the weather extremes come quickly. We go
from unseasonably cool into the heat as the ridge from the middle
of the country moves east. The baroclinic zone will become the
battle ground for the differential advection showers and
thunderstorms. Derechos are a concern. The models tend to do
poorly at pin-pointing the origin and track of the thunderstorm
complexes more than a day or two in advance. The models are not
building the ridge as far east as earlier in the week. This means
the forecast area will likely end up near the eastern edge of the
hotter weather. A flatter ridge allows for an easier ride for
thunderstorm activity over the top of the ridge. Eventually the
forecast area will be in the cross hairs for a thunderstorm
complex or two (or three?). The activity initially may stay to
our west, especially on Thursday. Thunderstorms may get to
northwest Ohio by early morning on Friday. Saturday could be the
busiest day.

[Stebo]

DTX's thoughts

 

 

The central Great Lakes will remain on the periphery of upstream
convection in a similar fashion Thursday night through Friday. Slow
progression of the long wave pattern and eastward drift of the
surface high will support the next leg of the warming trend Friday
and a more confident thunderstorm scenario by Friday night. There is
good model agreement with the favorable alignment of large scale
features Friday night into Saturday that will support MCS
development and propagation. Mature surface low pressure and the
accompanying low level jet will easily initiate convection over the
upper Midwest Friday evening while the surface warm front and upper
ridge axis provide an avenue into lower Michigan. Downstream
moisture/instability will be adequate for MCS persistence based on
more reasonable ECMWF forecasts of 850 mb dewpoint temperature near
15C and surface dewpoint in the lower 60s. This helps produce 700-
500 mb lapse rates near 7 C/KM and 850 mb LI near -5C by 12Z
Saturday, more than adequate for persistence and in line with the
day 3 SPC marginal outlook for severe.

 

GRR is a bit more ho-hum about it

 

 

Then the warm front is progged to lift north across the CWA Friday
night. This will bring much more humid air to the region. Again we
may see an MCS ride along this front, but a real good trigger
remains to our west in the form of a low level jet. So this seems
to point toward the MCS dying out as it approaches us from WI. Again
feel the severe threat is not zero, but remains low.

Current expectation is that any nocturnal/low level jet related
convection will exit the area saturday morning. Then, the progged
low level westerly flow and lack of sfc convergence/trigger may make
it difficult to refire afternoon diurnally driven convection despite
capes in excess of 2000 J/KG at pk heating. This will be
particularly true for the lk mi shoreline counties so probably a dry
afternoon there with better chance of afternoon convection east of
highway 131.

[ClicheVortex2014]

ILN

 

.Long Term /Saturday through Wednesday/...
Dry conditions will start out the long term Saturday morning. There
is still some uncertainty and model variability with Saturday
evening. With plenty of sunshine expect temperatures to climb to
around 90 or the low 90s on Saturday. Confidence is pretty high
that thunderstorms (some potentially severe) will develop and move
across portions of Ohio. Confidence is lower however with exact
location of development and whether or not it will be east of the
forecast area. There is enough of a consistent signal with some of
the model output and subsequent pattern recognition with the CIPS
analogs to keep, and in some cases increase, previous precipitation
chances for Saturday evening. If severe weather were to occur
across the Wilmington forecast area Saturday evening the best chance
would be across central Ohio and the main threat would be damaging
winds.

 

I wish they would've said more about Friday. I think that looks more likely to be the story for our CWA

[ClicheVortex2014]

WPC QPF looks good for Friday

 

[Hoosier]

4 km NAM has Chicagoland mostly dry after some morning/early afternoon activity.  Obviously subject to change.

 

 

[A-L-E-K]

It's going to bust too far north

[purduewx80]

There is a strong signal for training convection Thursday evening into pre-dawn Friday across northeast IL and southeast WI. It's probably not going to matter if the surface warm front makes it through, which it won't given convection lingering into early afternoon in these areas. The 850 front will be overhead and is parallel to the upper flow, with the low level jet nosing in thru the night. Localized rainfall amounts of 5+" should occur along and just sw of the 850 front...likely very close to the Chicago metro. 

[A-L-E-K]

Badabababaa

[OHweather]

I think the early convection and how quickly it moves out may be the wild card in northern IL for Thursday's severe threat. I don't doubt elevated stuff developing northeast of the WF later Thursday evening as the LLJ ramps up...but with a lack of forcing, we may need several hours of destabilization to get new storms to fire during the late afternoon/early evening along the WF/remnant OFBs. The CAMs that move the convection out earlier...around 16z...such as the NSSL and ARW...have a couple of rotating cells go up along the WF before dark. CAMs such as the NMM and 4km NAM that are slower with the AM convection have no redevelopment until elevated stuff goes up NE of the front later in the evening.

 

The 18z NAM is running a few degrees too high on dews (I was as shocked as anyone at this diagnoses) and I really doubt 70+ dew points in northern IL pooling west of the WF...but, even with dews in the mid to upper 60s, LCLs should be low enough and at least moderate MLCAPE should develop. With 35+ knots of bulk shear and effective helicity of over 200 m2/s2 near the warm front on forecast soundings on the NAM and GFS, I like the potential for cells that go up along the front to be supercells with a hail risk and a half decent chance for something tornadic. But, I think this all hinges on the AM convection moving out quickly enough. The 4km NAM does have a bit of a warm nose that acts as a cap, but nothing else really has that right now.

 

Due to the prospect of a couple of slow moving supercells along the WF that may produce, I intend to chase in northern IL as long as the AM convection looks on track to clear out quickly enough. This is probably desperation but if a surface based storm goes, it may be a beaut...but I'll evaluate the early convection in the morning when I should be able to gauge better before leaving.

[A-L-E-K]

There is a strong signal for training convection Thursday evening into pre-dawn Friday across northeast IL and southeast WI. It's probably not going to matter if the surface warm front makes it through, which it won't given convection lingering into early afternoon in these areas. The 850 front will be overhead and is parallel to the upper flow, with the low level jet nosing in thru the night. Localized rainfall amounts of 5+" should occur along and just sw of the 850 front...likely very close to the Chicago metro. 

 

 

getting that look...

 

[A-L-E-K]

catching up on overnight runs but lots of the CAM are showing heavy training cells along the western shore of the lake from the north side of the city up into geos country

 

definitely going to see some urban flash flooding if anything like the above play out

[purduewx80]

Successive RPM runs in the past day have wavered a bit with the exact placement of that band, but it's consistently shown training cells within about 50 miles of Chicago, with up to 10" in some locations on a few runs. Guidance typically does better with placement for elevated convection, but I still suspect there will be a slight southward adjustment to the means as cells build into the better instability. That is not good for urban areas from Madison and Milwaukee to Chicago.

[IWXwx]

Northeast Illinois/southeast Wisconsin, the next southeast Texas?