April 5 Severe Potential

[Hoosier]

SPC has an area outlooked for day 4/Wednesday, and it appears like there will be severe potential in the southern/eastern sections of the region.  

Moisture return could be better, but it looks adequate enough along with other favorable ingredients.  

[JoJo]

994mb low over Northern Indiana with an warm front east of that over Ohio and Western PA, type of set up could easily enhanced tornado risk near the main low, sort of an triple point

[LouWX]

If the moisture is there, the 0Z GFS Surface Low track through IN/IL and advancing warm front would be something to watch for sure.

[Indystorm]

Soundings from this Monday morning NAM run do look rather interesting for central and southern IL and IN for Wed. April 5 during the afternoon and evening.

[NTXYankee]

12z Euro not nearly as far south as prior runs moved north and more in line with GFS and NAM, strength of low about the same on all three.

[andyhb]

Large D2 moderate for the SE and a very large ENH area extending north to IN/OH.

[bjc0303]

Pretty synoptically classic system/evolution for outbreak scenarios east of the Mississippi.. Early day storm activity might throw a wrench in this one, however think some models are too aggressive with this activity..even in the wake of this the 3km shows discrete activity over an expansive area, possibly initiated in multiple corridors. 

 

 

[snowlover2]

17 minutes ago, andyhb said:

Large D2 moderate for the SE and a very large ENH area extending north to IN/OH.

And they mention possible strong tornadoes up here to Ohio.

Quote

  Day 2 Convective Outlook 
   NWS Storm Prediction Center Norman OK
   1238 AM CDT Tue Apr 04 2017

   Valid 051200Z - 061200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS WEDNESDAY INTO
   WEDNESDAY NIGHT ACROSS MUCH OF SOUTHERN AND EASTERN ALABAMA AND THE
   WESTERN FLORIDA PANHANDLE TROUGH GEORGIA AND PORTIONS OF WESTERN
   SOUTH CAROLINA...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
   SURROUNDING AREAS OF THE EASTERN GULF AND SOUTH ATLANTIC COAST
   STATES...NORTHWARD THROUGH THE TENNESSEE AND LOWER OHIO VALLEYS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SURROUNDING
   AREAS OF THE SOUTHEAST AND THE OHIO VALLEY INTO THE APPALACHIANS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS AS FAR WEST AS
   PORTIONS OF THE LOWER AND MIDDLE MISSISSIPPI VALLEY...AS FAR NORTH
   AS THE SOUTHERN GREAT LAKES REGION AND AS FAR EAST AS PORTIONS OF
   THE MID ATLANTIC COAST STATES...

   ...SUMMARY...
   An outbreak of severe thunderstorms is possible across much of the
   Southeast, northward along and west of the Appalachians into the
   Ohio Valley, Wednesday through Wednesday night.  This is expected to
   include supercell development with a risk for tornadoes, some of
   which could become strong and long-lived, particularly across parts
   of the Southeast.

   ...Synopsis...
   Amplification within the westerlies now appears underway across the
   eastern Pacific through the Pacific Coast region, and is expected to
   gradually translate eastward across and east of the Rockies through
   this forecast period.  As large-scale ridging builds across the U.S.
   Rockies and Canadian Prairies, large-scale downstream troughing is
   forecast to continue to evolve east of the high Plains through the
   vicinity of the Appalachians by 12Z Thursday.

   Models indicate that significant surface cyclogenesis will already
   be well underway by 12Z Wednesday across southern Missouri,
   associated with a vigorous short wave impulse within the southern
   stream of split westerlies, and forecast to turn northeast of the
   southern Rockies today.  Guidance indicates at least some
   interaction or phasing of the two streams is possible Wednesday into
   Wednesday night, with at least one northern stream impulse digging
   (across the northern Plains/mid Missouri Valley) into the evolving
   larger scale upper troughing by the end of the period.  This
   interaction remains a point of model uncertainty, and will have an
   impact on the track and rate of deepening of the surface cyclone.
   Regardless, the models generally indicate at least slow further
   deepening, as the low migrates through the lower Ohio Valley into
   the upper Ohio Valley/lower Great Lakes region by 12Z Thursday.

   South of the cyclone, an associated cold front is expected to
   eventually surge east of the Mississippi Valley through the
   Appalachians.  Low-level moisture will still be in the process of
   returning ahead of the front, in the wake of a prior system.  This
   remains the primary uncertainty which could temper the overall
   severe weather potential somewhat, as the environmental conditions
   associated with evolving synoptic system appear otherwise favorable
   for an outbreak of severe storms over a broad area east of the
   Mississippi Valley into the vicinity of the Appalachians.  And
   confidence in sufficient moistening and destabilization are
   increasing.

   ...Southeast...
   Greatest confidence in substantive boundary layer moistening still
   appears across portions of the eastern Gulf states into the south
   Atlantic Coast states.  Vigorous convective development may be
   ongoing at 12Z Wednesday inland of the northeast Gulf coast, in
   response to destabilization associated with the moistening, and
   large-scale ascent associated with low-level warm advection.  Models
   are suggestive that forcing for this activity will be aided by a
   high-level subtropical speed maximum, which may contribute to an
   increase in coverage through the day, within the northeastward
   advecting plume of richer precipitable water content.

   In the presence of at least modestly steep mid-level lapse rates,
   and wind profiles becoming characterized by strong deep layer shear
   and sizable low-level hodographs, considerable organized severe
   weather potential appears to exist.  This is expected to include
   discrete supercells accompanied by the risk for large hail and
   tornadoes.  In the wake of initial convective development expected
   to spread northward across and to the lee of the southern
   Appalachians during the day, guidance suggests new discrete storm
   development is possible within a low-level confluence zone across
   southern/eastern Alabama into western Georgia, with the environment
   ahead of this activity possibly becoming conducive to long-lived
   supercells with potential for strong tornadoes.

   Additional pre-frontal storm development is also possible to the
   west of this activity Wednesday afternoon into Wednesday evening.

   ...Ohio/Tennessee Valleys...
   Confidence is increasing in warm sector moisture return that will
   become supportive of weak to moderate CAPE, within at least a narrow
   pre-frontal plume overspreading the region from west to east
   Wednesday afternoon and evening.  Aided by forcing within the exit
   region of a 70-90 kt cyclonic 500 mb jet, and strengthening of
   southerly 850 mb flow to 30-50 kt within the warm sector, the
   environment is expected to become conducive to discrete supercell
   storm development, at least initially.  This is expected to be
   accompanied by a risk for large hail and a few tornadoes, some of
   which could be strong.  Eventually, large-scale forcing may support
   upscale growing lines or clusters of storms accompanied by a more
   substantive risk for damaging wind gusts.

 

[Quincy]

Definitely watch the area in the vicinity of the triple point tomorrow afternoon/early evening, beginning in southern IL and shifting into northern KY, southern IN and southwestern OH. 

Even assuming the NAM is a bit overdone with surface heating, the wind fields would certainly support a few supercells with a tornado threat. 

[snowlover2]

Enhanced area shifted farther west in KY/IN and mention of higher probs possibly being needed.

 

Quote

  Day 2 Convective Outlook 
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Tue Apr 04 2017

   Valid 051200Z - 061200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   AL/GA/SC AND THE FL PANHANDLE...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE OH/TN VALLEYS TO THE SOUTHEAST...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OH VALLEY
   TO THE SOUTHEAST AND MID-ATLANTIC...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   An outbreak of severe thunderstorms is likely Wednesday across much
   of the Southeast, continuing northward along and west of the
   Appalachians into the Tennessee and Ohio Valleys.  This will include
   supercell development with a risk for tornadoes, some of which will
   be strong and long-lived, particularly across the Southeast. Large
   to very large hail and damaging straight-line winds also appear
   likely.

   ...Synopsis...
   A highly amplified mid/upper-level trough will be present across the
   Plains at the beginning of the period, moving eastward to the MS
   Valley by Wednesday evening, and continuing to the OH/TN Valleys and
   Southeast by early Thursday morning. Two 100+ kt upper-level jets
   will be present across areas of severe potential Wednesday, one
   associated with the eastward-moving trough over LA/MS/AL/TN, and
   another 90-100+ kt sub-tropical jet nosing over southeastern AL, the
   FL Panhandle, and GA through Wednesday evening. Strong 50-80+ kt
   mid-level southwesterly winds will overspread much of the OH/TN
   Valleys and Southeast through the peak of the diurnal heating cycle,
   and these winds will then overspread much of the East Coast
   Wednesday evening through the end of the period.

   A strong southwesterly low-level jet is expected to advect rich Gulf
   moisture northward across portions of MS/AL/GA by Wednesday morning.
   This jet will shift eastward across GA/SC/NC/VA through the
   afternoon and early evening before strengthening further late
   Wednesday into early Thursday morning across the Mid-Atlantic. A
   somewhat separate corridor of strong southerly/southwesterly
   low-level winds will be associated with the mid/upper-level trough,
   and will overspread much of the OH/TN Valleys through the period. At
   the surface, an area of low pressure initially over southeastern MO
   will develop northeastward to IL/IN by Wednesday evening while
   deepening. This low will then slowly continue northeastward to the
   vicinity of the eastern Great Lakes by the end of the period. An
   attendant cold front will move eastward across the OH/TN Valleys and
   Southeast Wednesday, reaching the Mid-Atlantic by the end of the
   period.

   ...Southeast into the Mid-Atlantic...
   Warm air advection/LLJ related convection should form along the
   northward-moving warm front early Wednesday morning across parts of
   eastern MS, AL, and perhaps GA. This initial activity will pose a
   threat for all severe hazards, including tornadoes along/south of
   the front where surface-based convection will be more likely.
   Additional supercell development appears likely within the broad
   warm sector across the central Gulf Coast States, particularly
   across AL into GA/SC Wednesday morning/afternoon as large-scale
   ascent associated with the upper trough begins to overspread the
   Southeast. Forecast soundings across this region suggest strong
   tornadoes will be possible with any discrete storm that can form in
   this environment, in addition to very large hail and damaging
   straight-line winds. Severe probabilities have been
   increased/expanded westward slightly in western AL/eastern MS with
   latest model guidance showing convective development both Wednesday
   morning and another round associated with the large-scale forcing
   for ascent with the upper trough Wednesday afternoon ahead of the
   cold front.

   As the convection that develops Wednesday morning/afternoon moves
   across the Carolinas in the evening, a nocturnal increase in
   instability and resulting severe potential are possible across parts
   of the Carolinas into southeastern VA. This would occur in tandem
   with increasing low-level winds associated with a previously
   mentioned low-level jet, and strengthening mid/upper-level winds
   attendant to the approaching upper trough. If convection can become
   surface based in this region, then all severe hazards may occur,
   including a threat for tornadoes. Have accordingly
   expanded/increased severe probabilities across the Carolinas and
   southern/southeastern VA to account for this threat late Wednesday
   night into early Thursday morning.

   ...OH/TN Valleys...
   The northward advance of low-level moisture will be more limited
   across the OH/TN Valleys Wednesday, but will still be more than
   sufficient to support surface-based convection. A band of supercells
   appear likely per latest model guidance given the strength of low
   and mid-level winds coupled with weak to locally moderate
   instability. Large to very large hail and damaging winds appear to
   be the main threats, with a few tornadoes also possible. Given the
   forecast coverage of convection, it is not out of the question that
   higher severe probabilities may need to be considered in a later
   outlook update.

   ..Gleason.. 04/04/2017

 

[Anti tornado]

Yea...just going to leave this here

[snowlover2]

ILN very detailed concerning tomorrow.

 

Quote

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
The main concern for Wednesday is the potential for severe
weather -- possibly significant over at least a portion of the
ILN forecast area.

On Wednesday morning, a deep upper-level trough / mid-level low
will be moving east, roughly along the convenient Interstate 70
corridor into Illinois and Indiana. A combination of positive
vorticity advection ahead of this trough and favorable diffluent
flow in the upper levels will provide support for ascent ahead
of these features. At 850mb, strong warm advection will begin
occurring early in the morning, as a warm front glides northward
through Kentucky, Indiana, and Ohio. By late morning, the
entire ILN CWA is forecast to be in the warm sector at this
level. Near the surface, the scenario is slightly less clear,
but a surface warm front is eventually expected to move
northward into the ILN CWA -- perhaps translating most, but not
all of the way through the area. The warm sector at the surface
appears not as crisply defined, but mixing will combine with the
higher theta-e air aloft to allow for a change in air mass at
the surface. A model consensus was used for max temps, with a
fairly tight gradient (lower 60s in the northwest CWA, lower 70s
in the southeast CWA). However, dewpoints were input slightly
more carefully, as the GFS (lower 60s) appears too high, given
the ESE surface flow and modest deep-layer moisture transport. A
run through other models supports dewpoints peaking out in the
middle to upper 50s, which is more reasonable and in line with
recent events.

Aside from a chance of some showers in the northwestern CWA
during the early-to-mid morning, as the elevated warm front
clears through the region, the area is expected to remain dry
through early afternoon. Ahead of the slightly-occluding surface
low, as upper forcing and destabilization begin to combine,
convection is forecast to develop over Indiana during the early
to mid afternoon, entering the ILN CWA some time after 3PM. PoPs
are categorical as this area of precipitation moves through the
region from west-to-east (5PM-11PM). After this initial wave,
there is an apparent dry slot (a min in low-level forcing and
1000mb-500mb RH) before showery precipitation becomes more
widespread in the cooling air mass heading into Thursday
morning.

The thunderstorms that develop and move through the ILN CWA
tomorrow afternoon and evening will be within a very volatile
and concerning kinematic environment, easily supportive of a
range of severe weather threats. Instability and boundary-layer
air mass quality will potentially be a limiting factor to the
magnitude of the event, but it will not be a large-scale
deterrent, at least for a portion of the forecast area. Shear
for this event is expected to be strong and well-oriented.
Deep-layer SW to SSW flow aloft results in deep-layer shear
values (0km-6km) of potentially greater than 70 knots, easily
supportive of storm organization and supercell development. The
warm frontal presence across the area will lead to a notable
backing of flow near the surface, with southerly 850mb flow and
southeasterly winds near the surface -- remaining further
easterly with northward extent. The end result is that
hodographs will be well-curved, and SRH in the warm sector will
be around 150-200 0km-1km and 200-300 0km-3km, and near the
higher end of that scale (or slightly higher) in the less
unstable air close to the surface warm front. The orientation
of the deep-layer flow suggests that storms will have a notable
northward component to their motion (200-220), even as boundary-
layer inflow is significantly backed, especially below 925mb.
Ultimately, this environment is favorable for supercells, and
favorable for tornadoes with the right boundary layer
environment. Getting that boundary layer environment is the less
certain part of the equation for tomorrow, with aforementioned
concerns about the quality of low-level moisture return, and
uncertainty in breaks in the cloud deck in order to allow for a
degree of insolation. Though instability is nearly certain to
develop in the clear warm sector (up to 1000 J/kg MLCAPE near
and southwest of Cincinnati) it comes with less favorable
conditions near the surface, both in terms of RH and shear.
Where instability is more questionable, close to the warm front,
the other parameters line up to support the potential for
tornadoes in addition to other severe risks. 12Z WRF runs (ARW
and NMM) are tightly aligned in depicting lead cells moving into
the CWA around 21Z, possibly within the narrow window where the
most favorable shear and low level thermodynamics may overlap.
On the other hand, it is in this area where overall instability
is less certain to be sufficient.

The end result for the forecast is that severe weather is
expected, primarily in the southwestern half of the ILN CWA, and
focused especially on the SPC Day 2 ENH risk area. There will be
a narrow window where tornadic supercells will be possible to
occur, near the warm front at the northern periphery of the
stronger instability. South of this, a more significant
hail/wind threat may develop. North of the warm front, the
severe threat will quickly drop, and is very low to near-zero at
the far northern extent of the ILN CWA. As mentioned, the severe
risks outlined here are at least somewhat dependent on the
quality of moisture return and instability. Finally, there does
not appear to be a synoptic or mesoscale risk for flash
flooding, but heavier cores or training cells could result in
localized flood concerns. As instability wanes heading into the
late evening, the chances for strong storms will diminish, as
activity moves northeast through Ohio.

 

[andyhb]

That region of strongly backed flow near the triple point with a deepening surface low is prime territory for a cluster of cells to essentially go nuts assuming adequate destabilization reaches there (as Quincy highlighted yesterday). Won't take mid 60s dewpoints to yield that either with the degree of mid level cooling.

[snowlover2]

Confirmed tornado southeast of Joplin MO.

Quote

Severe Weather Statement
National Weather Service Springfield MO
701 PM CDT TUE APR 4 2017

MOC009-109-145-050045-
/O.CON.KSGF.TO.W.0024.000000T0000Z-170405T0045Z/
Newton MO-Barry MO-Lawrence MO-
701 PM CDT TUE APR 4 2017

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 745 PM CDT FOR EASTERN
NEWTON...NORTHWESTERN BARRY AND SOUTHWESTERN LAWRENCE COUNTIES...

At 701 PM CDT, a confirmed tornado was located 2 miles southeast of
Neosho, moving northeast at 45 mph.

HAZARD...Damaging tornado and golf ball size hail.

SOURCE...Law enforcement confirmed tornado.

IMPACT...Flying debris will be dangerous to those caught without
         shelter. Mobile homes will be damaged or destroyed. Damage
         to roofs, windows, and vehicles will occur.  Tree damage is
         likely.

Locations impacted include...
Neosho...                         Monett...
Granby...                         Pierce City...
Stotts City...                    Newtonia...
Freistatt...                      Wentworth...
Stark City...                     Ritchey...

This includes Interstate 44 between mile markers 33 and 41.

 

[JoJo]

I really do think due to the dynamics the storms will last through the evening into overnight, i don't think its gonna take much to get severe thunderstorms. Anywhere from SW PA to OH to E IN. i think is in the game. The warm front could cause some big trouble

[Hoosier]

[JoJo]

Eastern edge of the risk. I still think the Slight and Enhanced will need to be pushed northeast in OH/IN area to Extreme W PA. This system might have severe weather into the night in these areas from Eastern KY/WV/Central and Eastern OH/Extreme West PA. There are lots of convective uncertainties existing. Area in W OH/KY/SE IN does concern me for significant tornado potential in this thread area

[Hoosier]

6 minutes ago, JoJo said:

Eastern edge of the risk. I still think the Slight and Enhanced will need to be pushed northeast in OH/IN area to Extreme W PA. This system might have severe weather into the night in these areas from Eastern KY/WV/Central and Eastern OH/Extreme West PA. There are lots of convective uncertainties existing. Area in W OH/KY/SE IN does concern me for significant tornado potential in this thread area

You remind me a lot of a guy named northpittweather.

[JoJo]

42 minutes ago, Hoosier said:

You remind me a lot of a guy named northpittweather.

Who? honestly who is that?

[Jrad08]

Per the NAM... (Just north of CIN)

My concern here is the potential after dark for anything that stays discrete.

Sounding.pdf

[hlcater]

15 minutes ago, Jrad08 said:

Per the NAM... (Just north of CIN)

My concern here is the potential after dark for anything that stays discrete.

Sounding.pdf

Wouldn't those T/Td spreads and the inversion at 900mb cause issues for tornado development?

[Jrad08]

41 minutes ago, NWLinnCountyIA said:

Wouldn't those T/Td spreads and the inversion at 900mb cause issues for tornado development?

Agree 58 is a marginal dew however with this kind of setup at the triple point, it doesn't take dews north of 60+.

This setup is more conducive for low height storms generally EF0 - EF2 maybe EF3

But anything after dark is far more dangerous regardless of strength

*GFS has dew of 61 for the same timeframe

[Sidewinder]

SPC afternoon update going with a high risk from GA into SC. 
Significant tornado got moved way north too, pretty deep into Indiana. 

[josh_4184]

Large PDS watch issued, even in the Augusta area (Masters Tourney) could be a bad afternoon for those areas.

[Sidewinder]

Quite  the long track storm with tornado emergencies attached to it coming into the high risk area now. 

[Indystorm]

I have concern now for the cells starting to develop in far southern IL west of PAH and what that might portend later on for us farther east/ne.  This is a day when part of me wishes we would have a single thread for the storm in the various subregions.  Yet another part of me thinks it can get so active that it would rapidly become cluttered and best info specific to your area is easier to find in the subforums.

[Indystorm]

Concern also increasing for the Ohio River Valley.  Louisville is 81 degrees...effective shear up to 65 knots...0-3km helicity up to 400 already.  Tor watch issued from just north of Louisville to se Alabama.   Wow.

[Hoosier]

9 minutes ago, Indystorm said:

Concern also increasing for the Ohio River Valley.  Louisville is 81 degrees...effective shear up to 65 knots...0-3km helicity up to 400 already.  Tor watch issued from just north of Louisville to se Alabama.   Wow.

Going to need better moisture in the Ohio Valley (which should happen later). Dewpoints only around 50 in Louisville.  

[CoachLB]

Not decided on tornado or thunderstorm watch.

[snowlover2]

3 minutes ago, CoachLB said:

Not decided on tornado or thunderstorm watch.

Which I don't get because they mention in the disco that tornadoes are possible so they should just make it a tornado watch.