2024 Severe Weather General Discussion

[Kmlwx]

I'm interested to see if we keep getting dynamic systems into alter April and May. That could aid in increasing severe potential for our area. 

[Eskimo Joe]

7 minutes ago, Kmlwx said:

I'm interested to see if we keep getting dynamic systems into alter April and May. That could aid in increasing severe potential for our area. 

Yea if this trend keeps up, then May and early June could be interesting.

[high risk]

       While I'm modestly interested in Wednesday for areas south of DC, I'm actually intrigued a bit more (at least for those of us from DC to north) for Thursday.     Cold temps aloft will allow for some surface-based instability to be present, and with very low freezing levels, I think that some hail/graupel is likely with the stronger cells.    Downdraft CAPE is also present, meaning that some stronger gusts are possible too.   All of the CAMs have a good convective signal.    Maybe it won't quite require a MRGL, but it sure looks like an interesting afternoon.

[yoda]

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
134 AM EDT Wed Apr 3 2024

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Western Allegany County in western Maryland...
  Garrett County in western Maryland...
  Northern Grant County in eastern West Virginia...
  Mineral County in eastern West Virginia...
  Central Hampshire County in eastern West Virginia...

* Until 215 AM EDT.

* At 133 AM EDT, a severe thunderstorm was located near Thomas,
  moving northeast at 40 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Cumberland, Frostburg, Keyser, Mountain Lake Park, Oakland,
  Westernport, Romney, Bel Air, Bayard, Bittinger, La Vale, Fort
  Ashby, Lonaconing, Piedmont, Loch Lynn Heights, Deer Park, Elk
  Garden, Kitzmiller, Cresaptown, and Potomac Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

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

&&

[yoda]

SLGT risk of severe today from the BR and east... MRGL from just east of the i81 corridor to BR

2/15/15... but 5 tor probs for S MD

 

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1246 AM CDT Wed Apr 03 2024

   Valid 031200Z - 041200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE
   MID-ATLANTIC TO FLORIDA...

   ...SUMMARY...
   Strong to occasionally severe thunderstorms are possible on today
   from the Mid-Atlantic to Florida. Primary hazard is damaging gusts,
   but isolated hail and a tornado or two is also possible. Isolated
   hail and a strong gust or two are also possible from southeast
   Oregon into central Idaho.

   ...Synopsis...
   A mid-latitude cyclone is forecast to deepen/mature as it moves
   slowly eastward on today. Strong upper/mid-level flow will accompany
   this cyclone, with 120 kt of 500 mb flow extending throughout its
   eastern periphery from the Southeast through the Mid-Atlantic States
   during the afternoon and evening. Occluded surface low associated
   with this system currently over southern Lake Michigan will drift
   slowly eastward beneath the upper cyclone. 

   A secondary triple point low is currently developing to the
   southeast of the occluded low, and this low will likely be over the
   southwest VA vicinity later this morning. Expectation is for this
   low to progress northeastward throughout the day, while the cold
   front that extends southward from this low sweeps eastward.

   Farther west, a deepening upper trough will approach the Pacific
   Northwest coast late tonight/early Thursday morning. Enhanced
   southwesterly flow preceding this trough will spread gradually
   eastward across the Pacific Northwest into the northern Rockies.

   ...Mid-Atlantic southeastward to Florida...
   Thunderstorms will likely be ongoing along and ahead of the cold
   front mentioned in the synopsis, from the Mid-Atlantic southwestward
   into the eastern FL Panhandle. Air mass preceding this front will be
   characterized by ample low-level moisture (i.e. dewpoints in the
   mid/upper 60s), but poor lapse rates and relatively modest buoyancy.
   In contrast, robust wind fields will support strong vertical shear,
   with 0-6 km bulk shear likely around 60 to 70 kt. Consequently, even
   with limited buoyancy, a few stronger storms embedded within the
   broader convective line are possible. Damaging gusts are the primary
   severe risk, but isolated marginal hail and/or a brief tornado are
   also possible.

   The land area ahead of the front will be limited across GA and the
   Carolinas where the outflow-augmented front will likely push
   offshore by the early afternoon. Farther north in the Mid-Atlantic,
   additional storm development is possible near the surface low during
   the afternoon as moist southerly low-level flow facilitates air mass
   destabilization in the wake of the morning activity. Kinematic
   fields will remain very strong, and these storms will likely pose a
   severe risk as they move rapidly northeastward. Damaging gusts are
   the primary risk, but a tornado or two is possible as well. 

[CAPE]

From Mount Holly AFD early this morning-

Strong warm advection/isentropic lift and elevated instability will contribute to several rounds of showers, heavy at times, during the bulk of Wednesday as warm front moves northward aloft. That part is key...surface warm front, by contrast, looks likely to end up pretty stuck across the southern Delmarva through Wednesday. It may creep north slightly, but right now the I-95 corridor and points north still look most likely to stay in the relative cool sector, with highs in the 40s to lower 50s. Meanwhile, south of the front, highs surge into the 60s across southern Delaware and the lower eastern shore of Maryland. And this is what could make things more interesting in terms of severe potential as we get into the afternoon and early evening period as the triple-point low develops just to our southwest and tracks along the stalled front into the Delmarva and eventually far southern NJ.Depending on available instability, this could be a focal point for severe weather thanks to the enhanced shear along the warm front. SPC has placed a slight risk of severe weather across our extreme southernmost zones for Wednesday with the MARGINAL risk for severe weather extending a bit farther north through the remainder of Delmarva and then extending east through southern most NJ. Given the very strong shear, forcing, and "thick" CAPE values near 700 mb the set up could result in elevated supercells. Large hail and damaging winds look to be the biggest threats but we can`t rule out one or two tornadoes over southern Delmarva where there will be more in the way of surface instability.

[09-10 analogy]

The "triple point" is the severe season's kin to winter storms' "deformation zone."

[Eskimo Joe]

55 minutes ago, 09-10 analogy said:

The "triple point" is the severe season's kin to winter storms' "deformation zone."

Triple point with some EML ahead of it on a negatively tilted trough.

[yoda]

SLGT still up on 1300z SPC OTLK 

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0726 AM CDT Wed Apr 03 2024

   Valid 031300Z - 041200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   NORTHERN AND CENTRAL FLORIDA INTO SOUTHEAST GEORGIA AND FAR SOUTHERN
   SOUTH CAROLINA...AND FOR PORTIONS OF THE MID-ATLANTIC STATES...

   ...SUMMARY...
   Strong to occasionally severe thunderstorms are possible today from
   parts of the Mid-Atlantic states to Florida.  Damaging gusts and an
   isolated risk for a tornado or two are the primary hazards.

   ...Mid-Atlantic states into the coastal Carolinas and GA/FL...
   Morning water-vapor imagery shows a deep-layer cyclone centered over
   southern Lake Michigan and this feature will slowly migrate east
   into OH during the period.  Occluded low over southern Great Lakes
   will slowly fill as a secondary cyclone deepens as it moves from
   NC/VA this morning to south/east of Long Island late tonight.  A
   cold front will sweep east across the Southeast and through much of
   the FL Peninsula.  

   Strong to severe thunderstorm activity this morning concentrated
   over the FL Panhandle and southern GA will continue to progress east
   to the immediate southeast of an intense mid-level speed max over
   the southern Appalachians.  The airmass south and east of the front
   in north FL and southern GA will slowly heat/destabilize today
   despite relatively poor 850-500 mb lapse rates (reference 10z Cape
   Canaveral and 12z Tampa and Jacksonville raobs).  Strengthening and
   gradually veering flow with height will support organized line
   segments and occasional supercell structures embedded within the
   convective band.  A tornado or two and damaging gusts will be
   possible with the stronger activity through midday.  As this
   activity pushes southeastward over north FL into the central part of
   the Peninsula this afternoon, wind damage will likely become the
   primary severe hazard of concern.  

   Farther north, strong mid-level height falls and the aforementioned
   deepening of the low will invoke a strong mass response across the
   Mid-Atlantic states.  Relatively rich low-level moisture over NC
   this morning (low to mid 60s surface dewpoints) will advance
   northward in tandem with a warm front as the low develops northeast
   during the day.  Model guidance indicates a band of scattered
   thunderstorms will develop over central VA by early afternoon and
   move east towards the coast.  A few of the stronger storms will
   potentially evolve into supercells and/or organized line segments
   with damaging gusts/tornado as the main threats.  Farther south over
   central NC into northeast SC, some stabilizing influence from early
   morning convection (reference the 12z Charleston raob) and
   large-scale ascent focusing farther north lends uncertainty on
   coverage/magnitude of the severe risk near/south of VA/NC border. 
   Have lowered severe probabilities in parts of NC/SC to account for
   this observational trend and forecast scenario.  

[Kmlwx]

MUCAPE is on the rise per mesoanalysis...even if SBCAPE remains nada.

[yoda]

Sounds like a Tornado Watch coming soon per MCD 

[yoda]

1 minute ago, yoda said:

Sounds like a Tornado Watch coming soon per MCD 

Mesoscale Discussion 0368
   NWS Storm Prediction Center Norman OK
   1020 AM CDT Wed Apr 03 2024

   Areas affected...Portions of northern NC into VA...MD...and DE

   Concerning...Severe potential...Watch possible 

   Valid 031520Z - 031715Z

   Probability of Watch Issuance...60 percent

   SUMMARY...The threat for severe thunderstorms capable of producing
   damaging winds, a few tornadoes and perhaps some hail should
   gradually increase over the next couple of hours. Watch issuance
   will probably be needed.

   DISCUSSION...15Z surface observations show a front draped southwest
   to northeast across VA into MD/DE, with a surface low centered over
   southwest VA. This low is forecast to slowly deepen as it develops
   northeastward along the front towards central VA/MD by late this
   afternoon. Although clouds remain widespread across much of the
   Mid-Atlantic, a moist and gradually destabilizing airmass is present
   along/south of the front into NC. A lobe of ascent associated with
   the left exit region of a strong upper-level jet and a mid-level
   vorticity maximum over the central Appalachians will likely
   encourage additional convective development in the next 1-2 hours
   across western into central VA. This activity will likely become
   organized, with the potential for a mix of small bowing clusters and
   supercells possible given the presence of very strong deep-layer
   shear.

   Instability may tend to remain fairly muted given the widespread
   cloud cover. Still, MLCAPE around 500-1000 J/kg should eventually
   develop with continued low-level warming/moistening, and given
   steepened mid-level lapse rates noted on the 12Z RNK sounding.
   Damaging winds will be possible with any robust cluster that can
   develop and track northeastward. A tornado threat should exist with
   any supercell, as 0-1 km shear of 35-40 kt and ample effective SRH
   should encourage low-level updraft rotation. Isolated hail may also
   occur with any convection that can remain semi-discrete. Given
   expectations for a gradually increasing severe threat in the next
   1-2 hours, watch issuance will probably be needed.

   ..Gleason/Thompson.. 04/03/2024

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...PHI...AKQ...LWX...RAH...RNK...

[high risk]

No surprise that the tornado watch is for areas well south of DC.

[Terrapinwx]

Kinda surprised there isn’t at least a special weather statement for this line


.

[Eskimo Joe]

23 minutes ago, Terrapinwx said:

Kinda surprised there isn’t at least a special weather statement for this line.

I think the cool, stable surface airmass is mitigating the downward transport of wind. That line has passed over 2 mesonet sites, College Park and Baltimore City, and has not produced a wind gust greater than 10 mph.

[CAPE]

Surprised to see a tornado watch over here. With a temp of 50, socked in with clouds and light rain, clearly the warm front is still to the south. Remains to be seen if this marine airmass will budge.

Up to 2.42" for the event. Ditches overflowing and  lot of water lying around in low areas.

[Terrapinwx]

I think the cool, stable surface airmass is mitigating the downward transport of wind. That line has passed over 2 mesonet sites, College Park and Baltimore City, and has not produced a wind gust greater than 10 mph.

Yeah you nailed it, could hear the wind up above as the line came through but it didn’t mix down to the surface at all


.

[AlexD1990]

Surprised to see a tornado watch over here. With a temp of 50, socked in with clouds and light rain, clearly the warm front is still to the south. Remains to be seen if this marine airmass will budge.
Up to 2.42" for the event. Ditches overflowing and  lot of water lying around in low areas.

Storms down near Vienna kind of have that kidney bean look

Sent from my SM-F711U using Tapatalk

[AlexD1990]

And there's the tornado warning

Sent from my SM-F711U using Tapatalk

[CAPE]

Brief line of uneventful showers just came through here, and now blue skies and sun! Seems like forever lol.

[yoda]

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0359 AM CDT Sat Apr 06 2024

   Valid 091200Z - 141200Z

   ...DISCUSSION...
   An active severe weather pattern should persist through mid-week
   before diminishing towards next weekend. Primary feature of interest
   will be a southern-stream shortwave trough near the Southwest/Mexico
   border area at 12Z Tuesday. Non-GFS/GEFS guidance suggest this wave
   should eject east and amplify as it approaches the Lower MS Valley,
   before pivoting northeast ahead of a northern-stream shortwave
   trough digging towards the Upper Midwest. As this likely occurs,
   extensive convection is expected across the Gulf Coast region.
   Initially steep mid-level lapse rates and fast mid-level flow will
   support a broad severe weather area for D4/Tuesday across much of
   central/east TX and LA. Although mid-level lapse rates should be
   weaker on D5/Wednesday, the amplifying trough and resultant
   deepening of the surface cyclone, in conjunction with rich
   boundary-layer moisture, will support a continued severe threat area
   focused on the Sabine and Lower MS Valleys.

   D6/Thursday is the lower confidence forecast of the three days,
   given probable weak mid-level lapse rates with east/north extent.
   Still, there is enough signal in appreciable boundary-layer heating
   in the Southeast to warrant a severe area highlight within a highly
   sheared/weak CAPE environment. Flow fields throughout the
   troposphere will become quite strong across an even broader area
   farther north both east and west of the Appalachians. 00Z ECMWF
   ensemble data indicates a decent amount spread in timing/amplitude
   of the surface cyclone in the OH Valley/Midwest by Thursday, within
   a probable low CAPE environment. An area-of-interest for a future
   severe area highlight is evident in this region and into parts of
   the Northeast late Thursday or D7 Friday.

   ..Grams.. 04/06/2024

[Kmlwx]

12z CIPS guidance was honking pretty hard for the last panel (hr 132). One or two beefy events in there (including Apr 2011) 

[Kmlwx]

CIPS is more muted now but still a signal. The few beefy events it had have dropped down lower in the list. I think between timing issues and still early season this will be marginal at best for us. 

Still... Dynamic systems haven't shut off so if atmospheric memory exists it could still hint at an active late April/May. 

[Eskimo Joe]

Sub 1000 mb lows racing northeast from Ohio into NW Pennsylvania don't go quietly in the night. We could definitely see the first legit slight risk of the year Thursday.

[Kmlwx]

It's the NAM at range...and the 12k at that...but it has a formidable line of activity well to our west Thur evening. But the timing appears to suck. We'd need that to either speed up a bit or slow down by a day (to bump into Friday) to maximize potential. As it stands, still think this ends up as a typical "too early" even that *could* have been bigger. 

[yoda]

LWX AFD from this afternoon mentions the severe threat 

LONG TERM /THURSDAY THROUGH MONDAY/...

Potent low pressure in the southern stream will begin to phase with
northern stream energy as it tracks through the Midwest into the
Great Lakes Thursday, before moving into Canada Thursday night into
Friday. A strong cold front associated with this system will
approach the area Thursday before most likely passing through late
Thursday through Thursday night.

A strong southerly flow ahead of the system will allow for plenty of
moisture to advect into the area, causing widespread showers to
develop. There will be some instability, bringing the chance for
thunderstorms especially later Thursday into Thursday night (ahead
of the cold front). There is still low confidence regarding how
unstable it will get since clouds and rain will thwart diabatic
heating, but plenty of warm and moist air will cause at least some
instability. A line of heavier showers and thunderstorms may develop
late Thursday into Thursday night, bringing the threat for damaging
wind gusts. This will be dependent on how much instability can
develop an whether or not it will be rooted within the boundary
layer. Locally heavy rainfall may lead to isolated instances of
flooding during this time as well.

[Kmlwx]

18z NAM at range...(FWIW) - brings a line through around 6z Friday morning. That timing absolutely sucks. April 2011 was showing up on some of the analogs. Probably a very minor version of that...minus the like 12+ hours of Tornado Watches  

Had instability been better - or the timing maybe this could have been a bigger deal. We'll see if things shift/adjust at all as we close. 

[Kmlwx]

The 18z GFS suggests more like a 3z arrival of a "line" of storms on Thur night. That 3 hour difference could help a bit. 

[Kmlwx]

12z CIPS guidance is a lot of nothing and still a few eye opening ones lower on the list. Apr 16, 2011 is still showing up, February 2016 is showing up  and then a few less widespread events as well. 

[yoda]

 

Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0226 AM CDT Tue Apr 09 2024

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
   SOUTHEAST AND THE UPPER OH VALLEY...

   ...SUMMARY...
   Scattered severe thunderstorms are possible on Thursday across parts
   of the Southeast and the Upper Ohio Valley.

   ...Synopsis...
   A full-latitude mid/upper trough should be centered near the MS
   Valley at 12Z Thursday, comprised of two primary shortwave impulses.
   The southern-stream impulse should pivot northeast and accelerate as
   the northern-stream impulse becomes the dominant embedded feature. A
   steadily deepening surface cyclone should track northeast from the
   Lower OH Valley to the Lake Huron vicinity during the period. 

   ...Southeast...
   A convective swath should be ongoing from parts of the FL Panhandle
   into GA on Thursday morning. The southern portion of this activity
   will have the best chance to maintain a damaging wind and embedded
   tornado threat from late morning into the early afternoon as
   stronger boundary-layer heating occurs across FL. Large-scale ascent
   will weaken with southern extent through the day given the
   northeastward track of the surface cyclone, in addition to low-level
   winds becoming more veered in time over the FL Peninsula. 

   Farther north, fast 850-700 mb winds should be coincident with a
   plume of mid to upper 60s advecting north into the Carolinas.
   However, diabatic surface heating may be quite limited by abundant
   downstream cloudiness/stratiform rain north of the deeper convection
   in FL. Mid-level lapse rates will also be weak and overall
   instability may remain meager. Still, the high-shear/low-CAPE setup
   with at least low-topped convection likely persisting until it
   progresses off the coast will foster some threat for sporadic
   damaging winds and a few brief tornadoes, mainly midday through
   early evening. How far north and how long the severe threat persists
   into Thursday night is unclear, but low probabilities appear
   warranted through at least the Lower Mid-Atlantic States. 

   ...Upper OH Valley...
   A synoptically favorable corridor for a few supercells and organized
   clusters should develop east of the gradually deepening surface
   cyclone track. This region should have a period where an
   overspreading mid-level dry slot coincides with the diurnal heating
   cycle, before early afternoon convection develops within the
   left-exit region of the strong mid-level jet across the Southeast
   and southern Appalachians. While MLCAPE will remain weak, a
   meridional supercell wind profile should be present before low-level
   flow becomes veered from the southwest. A couple tornadoes, isolated
   to scattered damaging winds, and isolated severe hail are possible.

   ..Grams.. 04/09/2024