November 5th, 2017 Severe Weather Event

[tornado_junkies]

3 minutes ago, Stebo said:

Sure random poster...

My bad lol. I have another account but i can't remember the user information. 

[Stebo]

1 minute ago, geddyweather said:

A day that I can think of where there was total overcast but still produced a fruitful outbreak was 8/24/2016.  Total overcast in most locations but temps in the upper 70s/low 80s, dews the 60/70s, good SRH, and ample deep layer vertical shear made for a very active day. Though not exactly applicable for November in terms of certain conditions, this is one day that comes to my mind where clearing played little to no role in the events that followed. 

What about the June 5th-6th 2010 event, I remember that day being cool and cloudy in MI and NWOH and we ended up with several tornadoes as well.

[hlcater]

3 minutes ago, geddyweather said:

A day that I can think of where there was total overcast but still produced a fruitful outbreak was 8/24/2016.  Total overcast in most locations but temps in the upper 70s/low 80s, dews the 60/70s, good SRH, and ample deep layer vertical shear made for a very active day. Though not exactly applicable for November in terms of certain conditions, this is one day that comes to my mind where clearing played little to no role in the events that followed. 

Dynamics trump clearing in some cases. This is pretty often this time of year and I believe this will be one of those cases. As Hoosier said, any clearing and additional instability is a bonus at this point.

[Stebo]

Just for comparison sake Saturday evening, GFS is most aggressive with return flow then the 4km NAM, the 12km NAM is the least aggressive looking at AR/MO area.

http://weather.cod.edu/forecast/?load=modcomp&modcompType=2017110212-NAM-MW-sfc-dewp-60

 

[Hoosier]

5 minutes ago, Stebo said:

What about the June 5th-6th 2010 event, I remember that day being cool and cloudy in MI and NWOH and we ended up with several tornadoes as well.

That event did have some clearing breaks in the initiation zone (IL area).

[Stebo]

Just now, Hoosier said:

That event did have some clearing breaks in the initiation zone (IL area).

Yeah for that area. But out this way things eventually bubbled up as the EML rode in that evening.

[geddyweather]

12 minutes ago, Stebo said:

What about the June 5th-6th 2010 event, I remember that day being cool and cloudy in MI and NWOH and we ended up with several tornadoes as well.

Yep, that is another good case. 8/24/16 just happened to be the first (likely due to its recency) to come to my mind. Like @NWLinnCountyIA said, this Sunday may be another example of when dynamics overcome otherwise unfavorable cloudy conditions. Events that do so are often interesting to study afterwards as well, atleast IMO...

[Stebo]

21 minutes ago, Stebo said:

Just for comparison sake Saturday evening, GFS is most aggressive with return flow then the 4km NAM, the 12km NAM is the least aggressive looking at AR/MO area.

http://weather.cod.edu/forecast/?load=modcomp&modcompType=2017110212-NAM-MW-sfc-dewp-60

 

Also for comparison sake, the 00z Euro was closest to the GFS.

[Radtechwxman]

Yea with the steep lapse rates and good moisture adequete cape can be realized despite cloud cover. However if we did have more clearing obviously the ceiling for the event could be raised with higher cape and already adequate shear. I personally would like to see a more developed sfc system. 

[Chambana]

53 minutes ago, Stebo said:

Not seeing much of the way in clouds other than low level clouds and those can be eroded over time. When checking the 700mb RH, things look very good for limiting mid level clouds.

That makes sense, thanks Stebo. None the less impressive setup incoming. 

[Hoosier]

12z Euro is farther south.  Surface low actually passes south of Chicago.

[HillsdaleMIWeather]

7 minutes ago, Hoosier said:

12z Euro is farther south.  Surface low actually passes south of Chicago.

What does that do to the instability? Higher or lower?

[IllinoisWedges]

3 minutes ago, HillsdaleMIWeather said:

What does that do to the instability? Higher or lower?

There's still around 2000 j/kg on the WF in IL. 

[HillsdaleMIWeather]

12 minutes ago, IllinoisWedges said:

There's still around 2000 j/kg on the WF in IL. 

Just renewed my Eurowx subscription to look, parameters look about the same to the 0z run 

[Stebo]

33 minutes ago, Hoosier said:

12z Euro is farther south.  Surface low actually passes south of Chicago.

Yeah that is quite a bit south, will have to see how the ensembles shake out in comparison.

[OHweather]

The Euro still really lights things up after 18z near the triple point and east along the wf over northern IN and northern OH, and then has heavy QPF along the cold front overnight over much of IN and OH.  The warm front will definitely be something to watch wherever it sets up...you don't think of warm front supercells in November this far north.

[Stebo]

11 minutes ago, OHweather said:

The Euro still really lights things up after 18z near the triple point and east along the wf over northern IN and northern OH, and then has heavy QPF along the cold front overnight over much of IN and OH.  The warm front will definitely be something to watch wherever it sets up...you don't think of warm front supercells in November this far north.

Yeah all this does is change the locations of chasing from 00z, the quantitative response is still the same.

[HillsdaleMIWeather]

UPPER TROUGH IN THE PACIFIC NORTHWEST TODAY...DEAMPLIFYING AND EJECTING INTO THE NRN PLAINS THIS WEEKEND... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z ECMWF / 12Z GFS / 12Z CMC GREATER WEIGHT TO THE 12Z ECMWF CONFIDENCE: AVERAGE THE 12Z NAM AND 12Z UKMET HAVE THE WAVE EJECTING THE FASTEST INTO CANADA...BUT ARE ALSO STRONGEST WITH THE ACCOMPANYING MID-LEVEL VORT MAX AND THUS SHOW STRONGER CYCLOGENESIS ACROSS SOUTHERN CANADA THIS WEEKEND. THIS SOLUTION DOES NOT HAVE MUCH SUPPORT FROM THE 00Z GEFS AND ECMWF ENSEMBLE CLUSTERS. THE REMAINDER OF THE MODELS SHOW SOME DIFFERENCES...BUT HAVE TRENDED MUCH CLOSER WITH THE 12Z CYCLE AS COMPARED TO THE 00Z CYCLE. THEREFORE...A BLEND OF THE ECMWF...GFS...AND CMC IS PREFERRED. THE GREATEST WEIGHT WILL BE PLACED ON THE ECMWF...WHICH IS ROUGHLY IN THE MIDDLE OF MODEL SPREAD IN TERMS OF TROUGH AMPLITUDE AND STRENGTH OF THE SURFACE LOW.

[CheeselandSkies]

Yech, if it's IN and OH I'm out of the game.

[HillsdaleMIWeather]

IWX doesn't sound too enthused 

There is also some concern for isolated severe/strong storms
(wind/iso tornado) later Sunday and Sunday evening given strong
flow/shear, an EML, and sfc dewpoints into the low-mid 60s (CAPE
values near 1000 j/kg). However...cloud contamination, potential
for ongoing precipitation, weak large scale forcing (shortwave
trough rather flat), and chance for CAPE to remain largely
elevated appear to be limiting factors for strong/severe
convection locally. Regardless... a conditional threat to monitor
going forward.

[Indystorm]

Nevertheless, i still hope ILX gets whatever parts are needed to fix their radar before Sunday.

[tornado_junkies]

ILX

Quote

A warmer and more humid air mass will be overspreading the region
on Saturday, with dew points in the upper 50s/lower 60s by
afternoon. Early morning showers will end during the afternoon as
the warm front lifts further north. By early Sunday morning, a
rather sharp upper wave will be digging southward into the
northern Plains, helping to strengthen the surface system over the
upper Midwest. Abundant shear (>60 knots from 0-6 km) will be
over central Illinois by Sunday afternoon. As temperatures reach
into the 70s, the GFS progs show surface CAPE value rising to
around 1500 J/kg. Potential for supercells remains in place in
this juicy air mass, with damaging winds, large hail and a few
tornadoes possible. Next SPC update for this potential will be in
toward 2-3 am tonight. The cold front is progged by the morning
model suite to be close to I-55 by early evening, exiting the
southeast CWA toward midnight. Residual showers and storms will
taper off over the southeast counties overnight.

 

[snowlover2]

IND

 

Quote

.LONG TERM /Sunday Night Through Thursday/...
Issued at 248 PM EDT Thu Nov 2 2017

Models are close enough that the model blend initialization was
accepted for most items.

The threat for severe weather looks to continue Sunday evening with
a potent cold front moving into the area. Models continue to bring
in instability with a good low level influx of moisture and mild
temperatures. Shear and mid level lapse rates look good as well, so
at this moment it appears that all severe weather types remain in
play. Of course this far out in the forecast there remains some
uncertainty in timing and location of where things will end up. Will
keep a close eye on how this unfolds

 

[OHweather]

3 minutes ago, HillsdaleMIWeather said:

IWX doesn't sound too enthused 

There is also some concern for isolated severe/strong storms
(wind/iso tornado) later Sunday and Sunday evening given strong
flow/shear, an EML, and sfc dewpoints into the low-mid 60s (CAPE
values near 1000 j/kg). However...cloud contamination, potential
for ongoing precipitation, weak large scale forcing (shortwave
trough rather flat), and chance for CAPE to remain largely
elevated appear to be limiting factors for strong/severe
convection locally. Regardless... a conditional threat to monitor
going forward.

That's a very bearish assessment given their entire CWA is in a 30% day 4 risk. 

Some of those issues are legit, though I don't think it's unreasonable to get past all of them. The clouds/ongoing precip issue is minimized by the GFS and euro still spitting out respectable instability despite clouds and ongoing precip.  An EML and high unseasonably high dew points will do that.  Given the dry mid-levels I wonder if there won't be a few more breaks in the low clouds than expected.  There is a cap at the base of the EML but most models show enough lift with the front to blast through that, and it's not that strong of a cap.  Any sun weakens the cap further.  There's decent lift under favorable jet dynamics...could be stronger but it's not like a July setup with no large scale lift.  

[HillsdaleMIWeather]

6 minutes ago, OHweather said:

That's a very bearish assessment given their entire CWA is in a 30% day 4 risk. 

Some of those issues are legit, though I don't think it's unreasonable to get past all of them. The clouds/ongoing precip issue is minimized by the GFS and euro still spitting out respectable instability despite clouds and ongoing precip.  An EML and high unseasonably high dew points will do that.  Given the dry mid-levels I wonder if there won't be a few more breaks in the low clouds than expected.  There is a cap at the base of the EML but most models show enough lift with the front to blast through that, and it's not that strong of a cap.  Any sun weakens the cap further.  There's decent lift under favorable jet dynamics...could be stronger but it's not like a July setup with no large scale lift.  

I think they are being intentionally over cautious until they see more runs, which isn't necessarily a bad thing being 4 days out.

[snowlover2]

ILN at least talking about it now.

Quote

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Aforementioned frontal boundary will be moving north as a warm front
on Saturday. Moist ascent (WAA/isentropic lift) will already be
ongoing, bringing a chance of showers to the region during the
morning hours. An embedded s/wv is expected to pivot from the
central Plains into the Great Lakes during the day. Best overall
forcing still looks to be to our west/northwest. However, there are
some hints that showers may become a little more numerous as the
warm front moves through our northern zones. Confidence is not quite
there yet for likely PoPs, so have given all locations a high chance
PoP of 50 percent. Temperatures will warm into the 60s region wide.

The s/wv and warm front will lift north of the region Saturday
night.  Will continue with a chance of showers, but this chance
should decrease from south to north overnight. Lows will not fall
that much, ranging from the upper 50s to the lower 60s.

Focus for Sunday into Sunday night will be on a mid level trough to
traverse southern Canada/the upper Midwest/northern Great Lakes. A
cold front will accompany this system, which is still forecast to
move southeast into the region Sunday night. Initially, we should be
warm sectored for most of the day on Sunday. There could be a low
chance of showers, mainly across our northwest in the WAA pattern.
It will become breezy as south winds gust between 20 to 30 mph
during the afternoon.  Despite considerable clouds, this WAA pattern
will boost temperatures into the lower and perhaps mid 70s. For
Sunday night, models are in fairly good agreement on frontal timing
and a weak surface low to ripple northeast through the Great Lakes.
Instability ahead of the front will increase due to warm, moist air
in the low levels combing with steepening mid level lapse rates as
the front approaches. This setup will provide for MLCAPEs to be
close to 1000 J/KG early on across our region, with a gradual
overall decreasing instability trend as the night progresses
(diurnal cycle). Low level convergent forcing is expected to be
decent along and ahead of the front which will result in the
likelihood of showers and embedded thunderstorms overnight. There is
some concern for a few storms to be strong or marginally severe,
particularly across our far northwest early on. The pros for
marginal and/or a small severe threat are the marginal instability
and sufficient deep layered shear for storm organization. The
precipitation will likely end up forming into line segments.
However,the threat for a decent QLCS doesn`t seem to be there given
slow frontal movement, weak surface low pushing quickly away to the
northeast, and an unfavorable 0-3 km shear vector angle to the
potential orientation of the convective line. As such, do not think
the severe threat will be as expansive as currently depicted in the
SPC day 4 product and have opted to keep the low hazard probability
threat in the HWO at this time. If a threat should materialize, it
would be mainly due to wind. Lows Sunday night will remain mild,
ranging from the mid 50s northwest to the lower 60s southeast.

 

[andyhb]

Tbh, I wasn't terribly impressed by the 12z Euro, surface low is too weak for more notable pressure falls and thus a stronger low level wind response.

[Hoosier]

This is a bit of an atypical fall setup to be honest.  I'm not really sure what other fall event to compare it to synoptically... would have to do some digging (or check out CIPS lol).  It has some characteristics of a fall system, but better instability and less overwhelming forcing than most.  This will come into play as far as convective evolution. 

[RCNYILWX]

A majority of 12z EPS members shifted a bit weaker and south with the surface low vs. the 00z run. Still a ways to go, but considering shift on operational Euro as well, not the trends you'd want to see for a more substantial event, particularly with northward extent in Illinois.

[Stebo]

30 minutes ago, OHweather said:

That's a very bearish assessment given their entire CWA is in a 30% day 4 risk. 

Some of those issues are legit, though I don't think it's unreasonable to get past all of them. The clouds/ongoing precip issue is minimized by the GFS and euro still spitting out respectable instability despite clouds and ongoing precip.  An EML and high unseasonably high dew points will do that.  Given the dry mid-levels I wonder if there won't be a few more breaks in the low clouds than expected.  There is a cap at the base of the EML but most models show enough lift with the front to blast through that, and it's not that strong of a cap.  Any sun weakens the cap further.  There's decent lift under favorable jet dynamics...could be stronger but it's not like a July setup with no large scale lift.  

I agree with this assessment.