snowlover2

2019 Short/Medium Range Severe Weather Thread

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2 hours ago, Hoosier said:

Interesting CIPS... there are a few big fall outbreaks in there, a couple smaller ones and quite a few that produced no severe wx in the region.  Take your pick lol.  

I'd probably lean away from the bigger ones toward one of the smaller ones at this point given the concern about instability/mid level lapse rates.  Usually it's sort of hard to reverse the mid level lapse rate problem on the models once it's there.  Maybe pure advection can drive the temps up above guidance and help out the instability a bit.

SPC talking about it some in the day 4-8.

Quote

..D5/FRIDAY: OH AND MS VALLEYS  
 
STRONG FORCING FOR ASCENT IS ANTICIPATED ALONG THE FRONT AS IT MOVES  
EASTWARD ACROSS THE LOWER/MIDDLE OH AND MID MS VALLEYS. A STRONG  
CONVECTIVE LINE IS EXPECTED ALONG THE FRONT AS A RESULT WITH SEVERE  
STORMS POSSIBLE FROM IL/IN INTO LA/MS. HOWEVER, THE COVERAGE AND  
INTENSITY OF THESE STORMS WILL DEPEND LARGELY ON THE EXTENT OF THE  
MOISTURE RETURN AHEAD OF THE FRONT. THE STRONGER ASCENT AND BETTER  
DYNAMICS WILL BE DISPLACED NORTH (I.E. FROM THE LOWER TO MIDDLE OH  
VALLEY INTO THE UPPER MIDWEST) OF THE BETTER LOW-LEVEL MOISTURE  
(ACROSS THE MIDDLE/LOWER MS). AREA OF OVERLAP BETWEEN THE FAVORABLE  
DYNAMICS AND FAVORABLE THERMODYNAMICS DIFFER AMONGST THE GUIDANCE  
AND MORE MODEL CONSENSUS IS NEEDED BEFORE DELINEATING ANY AREAS.

 

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After slowing down on earlier runs, the models have sped up the front a bit in the past couple days.

Instability continues to look like it will be on the lower end.  The modeled temps/dews (dews in the low to mid 60s) would be good enough for a decent amount of severe wx in a lot of setups at this time of year, but overall CAPE is limited by those meager lapse rates.  The better mid level flow also lags behind by more than I'd like to see, especially given the aforementioned problem with instability.  I was surprised to not even see a token 5% area on the day 3 outlook though.  

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10 hours ago, Hoosier said:

After slowing down on earlier runs, the models have sped up the front a bit in the past couple days.

Instability continues to look like it will be on the lower end.  The modeled temps/dews (dews in the low to mid 60s) would be good enough for a decent amount of severe wx in a lot of setups at this time of year, but overall CAPE is limited by those meager lapse rates.  The better mid level flow also lags behind by more than I'd like to see, especially given the aforementioned problem with instability.  I was surprised to not even see a token 5% area on the day 3 outlook though.  

Still nothing on Day 2, IWX is mentioning bowing segments though

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03z HRRR

 

03Z-20191021_HRRRCHI_prec_radar-14-18-10-100.gif.17110203f9980393520521bee9edd05a.gif

 

Instability is on the low side but this has better wind fields into the warm sector than the system from a week and a half ago.  Not looking for much but a northward expansion of the marginal risk on the new day 1 outlook may be in order.  I guess we'll see.

 

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IWX has been beating the strong wind threat for several days. SPC isn't playing ball. These high shear low CAPE fall systems have had a history of producing some blow semis over winds.

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5 hours ago, IWXwx said:

IWX has been beating the strong wind threat for several days. SPC isn't playing ball. These high shear low CAPE fall systems have had a history of producing some blow semis over winds.

Yeah I see their morning afd mentioned a possible severe threat.  

Saw some small branches knocked down around the area this morning without thunder, so even any low topped line that can get going may be able to get severe/borderline severe winds to the surface.

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On behalf of the lakeshore, glad the Euro was wrong in this case. It will be bad enough as-is!

.DISCUSSION...(Today through next Sunday)
Issued at 330 AM EDT Mon Oct 21 2019

Another fall storm system will affect the region over the course of
the next 36 to 48 hours. We finally have some consensus with the
depth of the low, in the 980`s mb`s, over Wisconsin. Yesterday a run
of the ECMWF deterministic had a 975mb low over Wisconsin. Now both
the GFS and ECMWF are in the low 980`s. Still a formidable low by
Great Lakes fall standards. A reason why this will be a bit more
impactful in terms of winds along the lakeshore is that the low in
Wisconsin pinwheels towards us late tonight into Tuesday morning.
this will place the tightest pressure gradient right over Lake
Michigan. See details in the marine section on the Gale Warning and
Lakeshore Flood Warning that are now in place. We may need to
consider a Wind Advisory on the land in the lakeshore counties for
especially on Tuesday. At this point holding off on that, but the
day shift may need to consider it.

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Low end severe threat Tuesday?  The thermodynamics are pretty lackluster but those are some impressive wind fields.  Might be able to force some strong winds to the surface with anything even semi-organized.

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37 minutes ago, Hoosier said:

Boy if we had better instability

 

gfs_z500_vort_ncus_18.thumb.png.fd06dca56e822eef04205f6b9f49aa8a.png

 

gfs_uv250_ncus_18.thumb.png.9ba534bb6a889ab24db1fe8942f314ec.png

Of course we get this now and not in the spring when we would have some instability.

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   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1140 AM CST Mon Nov 25 2019

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
   THE LOWER TO MIDDLE MISSISSIPPI VALLEY...

   ...SUMMARY...
   Isolated severe storms with a threat for mainly damaging wind and a
   couple of tornadoes will be possible over a portion of the lower to
   middle Mississippi Valley region Tuesday.

   ...Lower to middle Mississippi Valley region...

   A strong shortwave trough now approaching the Great Basin will
   emerge over the central and southern Plains early Tuesday. A
   mid-upper jet within base of this feature will strengthen to 120 kt
   as the shortwave trough ejects negatively tilted through the middle
   MS Valley region. Lee cyclone initially over the southern High
   Plains will deepen within exit region of the upper jet as it
   develops northeast through the middle MS Valley by Tuesday evening.
   Trailing cold front will advance east and southeast through the
   central and southern Plains and MS Valley. By the end of the period
   the front should extend from a surface low over upper Great lakes
   southwest through LA and the TX coastal area.

   The boundary layer over the northwestern Gulf is in the process of
   modifying with latest observations showing dewpoints already in the
   upper 60s F. Positive theta-e advection promoted by southerly
   low-level winds will persist through Tuesday contributing to surface
   dewpoints near 70 F as far north as southern AR with upper 50s F
   into central MO. Widespread clouds should limit diabatic heating in
   warm sector, but MLCAPE should approach 1000 J/kg over the lower MS
   Valley. Farther north from eastern KS into MO the development of
   steeper lapse rates with colder air aloft (-14 to -16 C at 500 mb)
   will contribute to marginal MLCAPE with 500-800 J/kg possible within
   a more shallow convective layer. Two primary zones of surface based
   thunderstorm development are possible Tuesday afternoon and evening,
   including along the warm conveyor belt from northern LA into AR,
   western MS and TN, and farther north within zone of stronger
   pre-frontal forcing ahead of the cold front from eastern KS into MO
   and western IL. Broken bands of storms including potential for a few
   supercells and bowing segments will be possible in both of these
   regimes where vertical shear profiles will be more than adequate for
   organized structures with sizeable 0-1 km hodographs and 50+ kt
   effective bulk shear. Primary limiting factor for higher severe
   probabilities is the expected marginal thermodynamic environment.
   Nevertheless, at least isolated damaging wind and a couple tornadoes
   will be possible with the stronger storms.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   5%     - Slight
   Wind:     15%     - Slight
   Hail:      5%     - Marginal

   ..Dial.. 11/25/2019

 

day2otlk_1730.gif.f28ef941bfd905610ee8cdeeaa9d7fe7.gif

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NAM ticked up a bit with instability.  May have a shot at some surface or near surface based activity farther north/east in IL/IN despite the overnight timing.  I'll say it again... boy if we had better instability with this setup.  Would've been a big severe wx outbreak.  

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Something I have noticed on the models is that the surface based instability (what amount there is) tends to lag behind the potential convective line on Tuesday night into early Wednesday.  There isn't really as much of a lag when using MLCAPE.  So what it means is that if temps can warm up a bit quicker out ahead of the front (which is a distinct possibility with the strong southerly/southeasterly low level flow) then some surface based instability could develop more quickly for any convection to try to take advantage of.

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Pulling forecast soundings from the IL/IN area and man, the speed shear is just phenomenal.  About as good as it gets.  0-6 km shear progged in the 100-110 kt range (may be a struggle to even get convective tops much past 6 km though).  

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Marginal and slight risk areas expanded on the new outlook

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1156 PM CST Mon Nov 25 2019

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE LOWER/MID MS VALLEY...

   ...SUMMARY...
   Isolated to scattered severe storms with a threat for damaging winds
   and a few tornadoes will be possible across parts of the lower to
   mid Mississippi Valley this afternoon and tonight.

   ...Synopsis...
   A powerful mid-latitude cyclone will strengthen further today as it
   acquires a negative tilt and ejects northeastward from the
   southern/central Rockies across the Plains, eventually reaching the
   Upper Midwest and Great Lakes region by the end of the period. A
   very strong mid/upper-level jet (100+ kt at 500 mb and 175+ kt at
   250 mb) will likewise develop from the southern/central Plains
   across the mid MS Valley by Tuesday night. Pronounced large-scale
   forcing for ascent preceding the mid/upper-level trough will
   encourage a surface low to deepen as it develops northeastward from
   the central High Plains to the Upper Midwest by late tonight. A cold
   front attendant to this low will sweep quickly eastward across the
   southern Plains through the day. This front should reach parts of
   the OH/TN Valleys into the Southeast by early Wednesday morning.

   ...Lower to Mid Mississippi Valley...
   South-southwesterly low-level winds will continue to transport Gulf
   moisture northward this morning across parts of central/east TX and
   the lower MS Valley. Latest short-term guidance is in reasonable
   agreement that low to mid 50s surface dewpoints should extend as far
   north as northern MO and southern/central IL by this evening.
   Greater low-level moisture characterized by mid 60s to near 70 F
   surface dewpoints will likely remain confined farther south to parts
   of AR/LA/MS and east TX. At least two corridors of isolated to
   scattered severe thunderstorms may occur today/tonight: one in close
   proximity to the mid-latitude cyclone from MO northeastward into
   eastern IA and IL, and the other from AR to the Mid-South, possibly
   extending as far south as southern/central MS.

   Convection should develop along/ahead of the front across MO by late
   afternoon/early evening as strong ascent overspreads this region.
   Even though low-level moisture should be somewhat more limited with
   northward extent, temperatures should rapidly cool at mid-levels as
   the upper trough approaches. MLCAPE of 250-750 J/kg should develop
   by the time convective initiation occurs, with some guidance
   suggesting MLCAPE may reach near 1000 J/kg. Very strong shear owing
   to rapidly increasing wind speeds through the cloud-bearing layer
   suggest supercells will be possible initially, with both a damaging
   wind and isolated tornado threat. Isolated large hail may also occur
   early in the convective life cycle given the modestly steepened
   lapse rates and very cold temperatures aloft. A small bowing cluster
   should develop by late evening and quickly race northeastward into
   parts of IL, with mainly a damaging wind risk possibly continuing
   into early Wednesday morning as far east as western IN.

   A somewhat separate area of convection may form across the open warm
   sector in AR and the lower MS Valley by late afternoon owing
   primarily to low-level warm air advection and weak confluence along
   a pre-frontal trough. Very strong effective shear (60+ kt) and
   500-1000 J/kg of MLCAPE will support supercell structures with any
   storms that can form in this regime. Isolated instances of damaging
   winds and a couple tornadoes should be the main threats with this
   convection. There is some uncertainty with overall coverage through
   early evening, particularly with southward extent across LA and
   southern/central MS, as these areas will remain displaced to the
   south of the stronger large-scale ascent. Still, some increase in
   thunderstorm coverage with an isolated severe threat may occur late
   in the period (early Wednesday morning) as the surface cold front
   approaches and a 35-50+ kt southwesterly low-level jet remains over
   this region.

   ..Gleason/Nauslar.. 11/26/2019

swody1_windprob.png.3864b8bed5ebea4aa65f753219c19153.png

 

swody1_tornadoprob.png.d1fc3236e1ae9e28f36834222a0b388e.png

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There's a bit of clearing in ne OK and sw MO which I will watch as it moves northeastward.  As has been stated, instability is really the issue today. but kinematics are awesome.   Enhanced now shifted south in afternoon update.

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VYS gusted to 63 mph a little while ago.  

 

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Chicago/Romeoville
103 AM CST Wed Nov 27 2019

The National Weather Service in Chicago has issued a

* Severe Thunderstorm Warning for...
  Kendall County in northeastern Illinois...
  Northeastern La Salle County in north central Illinois...
  Southern De Kalb County in north central Illinois...
  Northern Grundy County in northeastern Illinois...

* Until 145 AM CST.

* At 102 AM CST, severe thunderstorms were located along a line
  extending from near Earlville to near Naplate, moving northeast at
  55 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
  Oswego, Ottawa, Yorkville, Little Rock, Minooka, Plano, Sandwich,
  Marseilles, Serena, Montgomery, Sheridan, Somonauk, Earlville,
  Newark, Leland, Naplate, Millington, Lisbon and Boulder Hill.

Including the following interstate...
 I-80 between mile markers 84 and 105, and between mile markers 115
and 122.

This includes...Buffalo Rock State Park, and Grundy County Speedway
and Fairgrounds.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4161 8906 4163 8899 4163 8894 4164 8894
      4173 8860 4172 8860 4172 8826 4144 8825
      4129 8894
TIME...MOT...LOC 0702Z 235DEG 48KT 4157 8897 4128 8886

HAIL...<.75IN
WIND...60MPH

$$

Kluber

 

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46 degree truck temp heading north across the state line under clear, starry skies with some gorgeous lightning on the northern horizon.

Got my October and November local sled rides in and holiday weekend inbound.

Digging it.

Sent from my SM-N960U using Tapatalk

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