Feb 28th - March 1st Severe Weather Outbreak

[hlcater]

5 hours ago, buckeye said:

It seems around here at least, storms associated with the warm front often over perform.    Meanwhile the main show severe threat that is suppose to occur with the cold front ends up being the dud.

Just something I've noticed throughout my years of weenie wx watching.

 

35 minutes ago, janetjanet998 said:

hints of a dry line bulge 

NAM has a more minor version but its there

Or if you're in iowa, they both bust and you get an HP conglomeration. Jokes aside, if that dryline bulge comes into fruition that really aids the tor potential. However, what are the odds of such a thing occurring so far east? Similar to those of any normal plains dryline?

[Indystorm]

00z NAM 4K looks ominous for I-70 corridor from Eastern IL into central IN Tues. night  03-06z as it shows a group of broken supercells advancing ne ahead of the developing squall line back to the northwest.

[Hoosier]

19 minutes ago, Indystorm said:

00z NAM 4K looks ominous for I-70 corridor from Eastern IL into central IN Tues. night  03-06z as it shows a group of broken supercells advancing ne ahead of the developing squall line back to the northwest.

Has some discrete looking cells in Chicago metro as well.  Here's a forecast sounding near Chicago out ahead of the cells:

I do think we still need to keep capping issues in the warm sector in mind.  If it takes forever to fully erode, then it will be tougher to realize the tornado potential out ahead of the cold frontal activity.

[Indystorm]

And soundings from PAH over to EVV look really foreboding with possible PDS tors.

[miller.b.time]

18 minutes ago, Hoosier said:

Has some discrete looking cells in Chicago metro as well.  Here's a forecast sounding near Chicago out ahead of the cells:

I do think we still need to keep capping issues in the warm sector in mind.  If it takes forever to fully erode, then it will be tougher to realize the tornado potential out ahead of the cold frontal activity.

Sorry for the complete noob question, but where on the CoD website does one find these soundings?

 

 

[Hoosier]

1 minute ago, miller.b.time said:

Sorry for the complete noob question, but where on the CoD website does one find these soundings?

 

 

Once you're on the model you want, just point and click for whatever hour and location.

[Chicago Storm]

CAMS all over the place for tomorrow/tomorrow night, not surprisingly.

SPC WRF with a sig run for many areas and is worth a loop.

Few images for local interests...

[hlcater]

54 minutes ago, Hoosier said:

Once you're on the model you want, just point and click for whatever hour and location.

Another noob question, Does CoD offer observational soundings on their site? I used to use the SHARPpy app, but it broke on my pc, and I really don't like the SPC site.

[IllinoisWedges]

2 minutes ago, Chicago Storm said:

CAMS all over the place for tomorrow/tomorrow night, not surprisingly.

SPC WRF with a sig run for many areas and is worth a loop.

Few images for local interests...

Could you link the site, or the reupload the pictures? I believe they got corrupted or something along those lines, at least for me. 

[Hoosier]

4 minutes ago, NWLinnCountyIA said:

Another noob question, Does CoD offer observational soundings on their site? I used to use the SHARPpy app, but it broke on my pc, and I really don't like the SPC site.

Yeah they do. Click on weather analysis tools near the top of the page, and then on analysis data.

[Chicago Storm]

Could you link the site, or the reupload the pictures? I believe they got corrupted or something along those lines, at least for me. 

http://www.emc.ncep.noaa.gov/mmb/mpyle/spcprod/00/

[IllinoisWedges]

Just now, Chicago Storm said:

http://www.emc.ncep.noaa.gov/mmb/mpyle/spcprod/00/

Thank you, I appreciate it! 

[Hoosier]

Izzi's thoughts:

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
909 PM CST Mon Feb 27 2017

.UPDATE...
909 PM CST

No big changes to going forecast, though did hit thunder harder in
the grids tomorrow night.

A warm front is situated across MO and downstate IL this evening,
poised to move northward tonight as cyclogenesis occurs over the
central plains. Strengthening low level flow will begin to quickly
advect higher theta-e air mass north tonight, with strengthening
isentropic ascent likely to result in some showers and
thunderstorms developing overnight. Guidance in fairly good
agreement on lifting this warm front rapidly north into Wisconsin
Tuesday morning. WAA driven showers and thunderstorms should lift
north out of the area with the warm front, however impressive
elevated mixed layer (EML) will be in place setting the stage for
potential elevated weak convection during the day in the warm
sector. Fairly extensive stratus deck already exists behind the
warm front across the Arklatex and this stratus deck should
rapidly advect north and blanket the area Tuesday.

The presence of stratus should prevent any substantial insolation,
so warming of the boundary layer will be driven largely through
advection. The stratus deck and impressive EML above the stratus
should provide for a formidable capping inversion limiting the
threat of any surface based convection through much of the day.
Secondary warm front/moisture discontinuity boundary is forecast
to develop over northern IL during the afternoon and some of the
convective allowing models (CAMs) do develop convection near this
feature. That scenario is certainly plausible, however the more
substantial threat of threat of surface based convection should be
delayed until very late in the afternoon or more likely during the
evening hours when guidance suggests that strong synoptic ascent
will result in a weakening MLCINH and an increasing chance of sfc
rooted convective development.

Continued transport of unseasonably warm/moist air mass (Tds in
the upper 50s to perhaps lower 60s) beneath seasonably cold air
aloft should result in unusually strong SB based instability for
this time of year. Assuming synoptic ascent is indeed enough to
lift through the low level inversion/inhibition, then potential
will exist for robust boundary layer rooted convection to develop.
Given the very strong shear profiles, if instability gets as
strong as guidance suggests it could, then potential would exist
for sizable severe weather risk. This would certainly be an out of
season event and there are many modes of failure, but there are
indications that we could be entering into a severe weather
parameter space in which significant severe weather occurs. CAMs
are offering a wide variety of solutions with respect to
convectivedevelopment and storm mode, so confidence isn`t
terribly high in how things will unfold. However, many ingredients
do appear to be coming into place for non-trivial severe weather
risk across the CWA, in particular southern CWA where confidence
is highest in instability being sufficient. The primary threat
should be large hail/damaging winds, but very strong low level
shear profiles and low LCLs could support a tornado risk well into
the evening hours if any sustained supercells can develop or with
any well developed QLCS.

Worth stressing that this is far from a high confidence set up,
however there does appear to be a non-trivial threat of
potentially respectable out of season severe weather event. For
this reason alone, heightened awareness of the weather is
encouraged tomorrow. Also, given the majority of the low level
destabilization is expected to be driven by advection rather than
insolation, the severe threat may not wane during the evening
hours, and in fact could increase at night as some models forecast
instability to increase during the evening hours. In summary,
while confidence isn`t yet great, there is some potential for a
night time, out of season severe event tomorrow evening/night.

Izzi

[cyclone77]

Just now, Hoosier said:

Izzi's thoughts:

Still pondering eh?

[Hoosier]

Just now, cyclone77 said:

Still pondering eh?

Damn formatting, lol

[Sidewinder]

New Day 1 thumbnail image is up, but the text isn't working yet. Or they re-upped the previous update. 

 

[yoda]

[yoda]

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1139 PM CST Mon Feb 27 2017

   Valid 281200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM AR TO
   IL/IN...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OK TO
   OH...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   TX TO WESTERN PA...

   ...SUMMARY...
   Severe thunderstorms are expected to develop from portions of the
   lower Mississippi Valley to the Ohio Valley Tuesday.  Large hail,
   damaging winds, and a few strong tornadoes are possible.

   ...Discussion...

   Ridging appears to be responsible for delaying meaningful convection
   across the MS Valley late this evening.  However, LLJ is beginning
   to increase across MO/IL and isolated thunderstorms are evolving
   within a corridor from the Bootheel of MO into central IL.  This
   activity should gradually expand in areal coverage as warm advection
   lifts north toward the Great Lakes region.  Given these trends,
   there is increasing confidence that much of the southern
   Plains/lower MS valley will remain convection-free into the
   afternoon hours.  As a result, significant boundary-layer recovery
   is expected into the OH Valley prior to frontal passage.

   Late evening model guidance continues to suggest a corridor of
   strong southwesterly flow aloft will extend from the southern
   Rockies, into the Great Lakes with 500mb flow expected to increase
   in excess of 80kt by early afternoon across western portions of the
   severe risk area.  Large-scale height falls will overspread the
   Mississippi Valley and several convective scenarios may ultimately
   evolve within a broad moistening warm sector.

   1.  Warm-advection corridor (northern IL):

   Strengthening LLJ over IL will aid northward advance of higher
   quality air mass as surface dew points rise through the 40s into the
   50s as far north as northern IL by late morning.  Warm advection is
   expected to induce scattered strong/severe thunderstorms early in
   the period as warm front lifts northward in advance of the primary
   surface wave.  Convection may be aided by a weak mid-level
   disturbance embedded within the stronger southwesterly flow. 
   Initial activity will be elevated in nature and hail is the primary
   risk with these storms.

   2.  Warm sector (AR/MO/IL):

   28/00z sounding from OUN exhibited a steep-lapse-rate environment
   with substantial low-level moisture.  Strong capping and
   neutral-weak subsidence will allow this air mass to advect northeast
   such that surface dew points should rise into the lower 60s across
   much of the warm sector south of I-70.  Breaks in cloud cover during
   the day should allow surface parcels to approach their convective
   temperatures from eastern OK into southwestern MO by mid-late
   afternoon.  Latest thinking is isolated supercells may evolve well
   ahead of the cold front along nose of a secondary branch of LLJ that
   will strengthening across AR during the day.  It's not clear how
   much storm coverage will be noted across this region but
   environmental shear and increasing instability/buoyancy favor robust
   supercells.  Forecast soundings suggest very large hail could
   accompany this activity and a few strong tornadoes are possible,
   especially if discrete structures evolve as it appears they may.

   3.  Cold front:

   Large-scale forcing will contribute to a convectively active cold
   front by early evening as the wind shift surges into an increasingly
   moist/unstable air mass from eastern IA into northern MO. 
   Thunderstorms are expected to mature into a strong squall line that
   will surge east across the mid MS Valley into the OH valley as 500mb
   flow increases to near 100kt by 01/12z.  Damaging winds should be
   noted with this frontal convection and tornadoes may also be
   embedded along the line.  Eastward momentum should easily allow this
   activity to spread across much of OH by sunrise Wednesday morning.

   ..Darrow/Picca.. 02/28/2017

 

[Chicago Storm]

Bumped the risk a bit north again.

Still fully expect it to be pulled even further north, to DBQ-MKE-GRR as I mentioned earlier today.

[Hoosier]

17 minutes ago, Chicago Storm said:

Bumped the risk a bit north again.

Still fully expect it to be pulled even further north, to DBQ-MKE-GRR as I mentioned earlier today.

I would've bet money on it getting to at least the IL/WI border on this outlook. Glad I didn't lol

[Chinook]

This might sound crazy, but I am a little worried that severe weather might hit northern Indiana at 5AM Wednesday, when nobody is ready for it. If it's just a 50mph wind gust, then not too much to worry about. But a tornado... oh boy. I have family members in Ft. Wayne and South Bend.

[Hoosier]

Since 1950, there's been only 1 February tornado in the LOT cwa, and it was back in 2006.  Right now the 10% hatched tornado area is in the southernmost portion of LOT and the 5% area covers a large chunk of the rest of LOT, save for the northern third or so.  Basically anything happening tornado wise in LOT's cwa would be giving the middle finger to climo, not only because of time of year but typically less favorable time of day as well.

[tornadohunter]

05z HRRR 22z within 50 miles SW of Chicago. 

05z HRRR has storms firing at the time as well. 

[Hoosier]

HRRR has that dewpoint bulge/mixout as well.

[Hoosier]

33 minutes ago, tornadohunter said:

05z HRRR 22z within 50 miles SW of Chicago. 

05z HRRR has storms firing at the time as well. 

Would be concerning. Right on a line into the southern suburbs.

[tornadohunter]

0z 3km NAM just says goodbye to the southern midwest. Thats a lot of UH tracks FWIW

[andyhb]

10 minutes ago, tornadohunter said:

0z 3km NAM just says goodbye to the southern midwest. Thats a lot of UH tracks FWIW

That's mostly from the linear convection along the front, not supercells.

[tornadohunter]

Just now, andyhb said:

That's mostly from the linear convection along the front, not supercells.

Agreed but doesnt that mean a decently elevated risk for QLCS spin ups?

[Thundersnow12]

The HRRR continues to paint a very scary and ominous scenario for northern Illinois and the Chicago metro area...early 22-0z, fairly discrete supercells or one single storm...and even if those storms are slightly undercut you're talking the threat for very large mail and strong damaging winds. 

And if they are surface based....well...have to be worried about a serious tornado threat. 

[Hoosier]

12 minutes ago, Thundersnow12 said:

The HRRR continues to paint a very scary and ominous scenario for northern Illinois and the Chicago metro area...early 22-0z, fairly discrete supercells or one single storm...and even if those storms are slightly undercut you're talking the threat for very large mail and strong damaging winds. 

And if they are surface based....well...have to be worried about a serious tornado threat. 

The environment near the city and south on the HRRR in the timeframe you mentioned is pretty impressive, with good turning in the low levels.  0-1 km shear of 50 kts, 0-1 km helicity of 400-600.  There's a bit of a low level inversion on the forecast soundings at face value.