2024 Severe Weather General Discussion

[Kmlwx]

LWX mentions lack of instability...which we already knew would be the issue here. Few good analogs still showing up in CIPS at the 72hr frame. Better timing/better instability with this probably would have allowed for a pretty sizeable severe risk. I don't really see anything to suggest major changes from what we are expecting though. Gusty line of showers/storms Thur night seems like a good bet, though. 

[yoda]

Morning day 2 OTLK from SPC (no hail probs so skipped that image)

 

[yoda]

SPC AC 100551 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1251 AM CDT Wed Apr 10 2024 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN THE UPPER OH VALLEY AND PARTS OF THE SOUTHEAST... ...SUMMARY... Severe thunderstorms with a few tornadoes, scattered damaging winds, and isolated large hail are likely across the Upper Ohio Valley vicinity, mainly during Thursday afternoon. Scattered damaging winds and a few tornadoes will also be possible across southeast Georgia into central Florida, from Thursday morning into the afternoon. ...Synopsis... A full-latitude mid/upper trough will 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 will track northeast from the Lower OH Valley to the Lake Huron vicinity during the period. ...Upper OH Valley... A synoptically favorable corridor for a few supercells and organized clustering into short-line segments appears likely to 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 afternoon convection develops within the left-exit region of the strong mid-level jet across the Southeast and southern Appalachians. MLCAPE should reach 500-1000 J/kg amid a meridional supercell wind profile, before low-level flow becomes veered from the southwest. Consensus of 00Z CAM guidance supports the potential for a few supercells, with some upscale growth into a line segment as convection consolidates northeastward. This may be relatively short-lived as convection outpaces the weak buoyancy plume and likely weakens after dusk. A mesoscale corridor of greater severe probabilities, seemingly in the form of damaging wind, may be warranted in later outlooks. ...Southeast GA to central FL... Extensive deep convection should be ongoing from north FL into GA at 12Z Thursday. The southern portion of this activity will have the best chance to maintain a damaging wind and embedded tornado threat during the late morning into about mid-afternoon as stronger boundary-layer heating occurs across the FL Peninsula. Large-scale ascent will subside 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. ...Carolinas and VA... Overall severe threat appears rather conditional during the daytime hours given extensive convection across at least north FL and GA on Thursday morning. Diabatic surface heating should be quite limited by abundant downstream cloudiness/weak convection north of the deeper convection during the day. Consensus of guidance largely attempts to destabilize on the backside of early-day convection within a plume of at least mid 60s surface dew points. Overall threat will probably consist of sporadic damaging winds and up to a few brief tornadoes within lower-topped convection, mainly from midday through Thursday evening. With the expectation for lesser severe weather coverage relative to areas farther northwest and south, have opted to highlight much of this region with a cat 1-MRGL this cycle. ..Grams.. 04/10/2024

[yoda]

Updated morning AFD from LWX now mentions tornado threat

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Rain chances increase further Thursday morning as a frontal
system inches closer to the region, but the bulk of
precipitation likely arrives Thursday afternoon. Strong
southerly winds are expected to develop ahead of the approaching
cold front, which could reach 25 to 35 mph or so.

The upper trough that is currently digging into the MS River
Valley will lift northeastward towards the Great Lakes, becoming
negatively-tilted into Thursday evening/night. Given the amount
of pre-frontal showers and clouds, instability looks to be hard
to come by, especially with the timing looking to be later in
the evening into Thursday night. However, given height falls
aloft and anomalous low-level moisture, 200-400 J/kg ML/SBCAPE
still looks achievable. This, combined with increasing low-level
flow to 50+ kts at a few thousand feet AGL (especially late at
night Thursday into early Friday morning) could be enough for
low-topped convection capable of bringing down damaging wind
gusts or spinning up a brief tornado or two. The greatest
potential for any severe weather appears to be Thursday night.

[Kmlwx]

12z FV3 actually looks pretty good on sim reflectivity. 

[midatlanticweather]

Nadocast

https://x.com/nadocast/status/1778082581541752878 

 

 

[Kmlwx]

Bullish! 

[yoda]

Might get a slight risk upgrade at 1730z 

[high risk]

1 hour ago, Kmlwx said:

12z FV3 actually looks pretty good on sim reflectivity. 

definitely the best solution, but somewhat on its own.    Our best hope for SVR is focus in the early evening, as the potential for something if we have to wait later in the night is still fairly low, IMHO, despite some good wind fields

[yoda]

Still MRGL on 1730z SPC OTLK... but a small ENH risk was added in E Ohio into West Virginia with 10% tor probs added

[yoda]

SLGT risk moved into most of N VA and C MD on new Day 1 for 15 wind and 5 tornado 

[yoda]

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1247 AM CDT Thu Apr 11 2024

   Valid 111200Z - 121200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE UPPER OHIO RIVER VALLEY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE OHIO RIVER VALLEY AND NORTHERN FLORIDA TO SOUTHERN GEORGIA...

   ...SUMMARY...
   Severe thunderstorms with a few tornadoes, scattered damaging winds,
   and isolated large hail are possible across the upper Ohio River
   Valley and parts of the Appalachians this afternoon. Scattered
   damaging winds and a couple tornadoes will also be possible across
   southeast Georgia into northern Florida, mainly this morning through
   early afternoon.

   ...Synopsis...
   04 UTC surface observations depict a diffuse surface low over the
   lower MS River Valley. This low is forecast to deepen over the next
   24 hours as it lifts northward into the OH Valley/Great Lakes region
   in tandem with the phasing of an amplified upper-level trough over
   the MS Valley with an approaching upstream perturbation. A surface
   cold front currently draped across southeast LA will surge to the
   east/northeast as the low deepens, and should act to focus
   thunderstorm development through the late morning and afternoon
   hours across both the upper OH Valley and Southeast.

   ...Upper OH River Valley...
   Recent 925/850 mb analyses and surface observations show a
   consolidating warm frontal zone draped from the surface low over the
   lower MS Valley into the upper OH River Valley. The surface low will
   deepen along this corridor amid a combination of strong height falls
   and ascent within the left-exit region of a mid-level jet. A plume
   of low to mid-60s dewpoints will advect northward with the deepening
   low, establishing a focused warm sector ahead of the approaching
   cold front by early afternoon across parts of KY, OH, and WV. The
   current expectation is for sufficient destabilization within the
   warm sector to support surface-based convection by the 18-21 UTC
   time frame. A combination of strong synoptic-scale ascent and 40-50
   knot deep-layer shear vectors off the cold front should promote a
   mix of discrete cells and semi-discrete clusters - including the
   potential for a few supercells. Increasing southeasterly winds
   through the lowest 1-2 km should yield effective SRH values between
   150-300 m2/s2, which will support a tornado threat with the more
   robust/organized cells as well as a wind threat with more organized
   clusters. This threat appears greatest across southeast OH into
   western WV where latest guidance continues to show a focused
   convective signal. Further to the east into parts of northwest VA, a
   somewhat weaker convective signal is noted in most CAM guidance, but
   50-knot flow in the lowest 2 km will likely pose a substantial wind
   threat with any storms that can mature. Risk probabilities have been
   expanded into this region to account for this potential. 

   That said, this scenario appears to be conditional on achieving
   sufficient low-level warming within the warm sector. While an
   extensive dry slot is noted in water-vapor imagery across the
   Mid-South into central IN, the low/mid-level warm advection regime
   is maintaining mid-level stratus across the region with most ASOS
   stations reporting overcast skies and ceilings near 6 kft. It is
   unclear how much clearing will occur through early afternoon given
   persistent ascent, and a 10 F spread in afternoon high temperatures
   is noted across OH/WV in recent ensemble guidance. Based on forecast
   soundings, surface temperatures in the upper 60s may be required to
   realize 500+ J/kg SBCAPE with minimal inhibition. The median of the
   temperature distribution appears to reside in the upper 60s, but
   SBCAPE may still only reach 500-1000 J/kg per ensemble
   distributions.

[yoda]

Morning AFD from LWX on the threat

The upper trough will take on a negative tilt as it moves
overhead tonight. At the surface, low pressure will deepen as it
tracks into the Ohio Valley. Thunderstorms are expected to form
within the zone of strong forcing for ascent ahead of the
negatively tilted trough across OH/WV/SW VA late this afternoon
into early this evening. These storms should initially reach
far southwestern portions of the forecast area during the late
evening, before progressing northeastward across the remainder
of the forecast area between 10 PM and 4 AM.

Instability will increase through the evening as a low level
mass response occurs ahead of the approaching trough. CAPE
values are expected to increase to around 300-600 J/kg across
much of the area. When coupled with an impressive low- level jet
and ample deep layer shear present, some of the storms this
evening into the overnight may be on the strong to severe side.
Damaging winds should be the primary threat, but a brief tornado
can`t be ruled out given the strong low-level jet, 0-1 km SRH
values increasing to around 200-300 m2/s2, and STP values
climbing above 1. Weak stabilization evident on forecast
soundings right near the surface may potentially serve as a
limiting factor for both the damaging wind and tornado
potential. SPC currently has locations to the west of the Blue
Ridge outlooked in a Slight Risk for severe thunderstorms, while
locations to the east of the Blue Ridge are in a Marginal Risk.

[Kmlwx]

Meh

[yoda]

1300z SPC OTLK update

Mid-Atlantic states into Carolinas...
   A less focused and more conditional severe risk seems evident for
   the Carolinas later this afternoon and northward into the
   Mid-Atlantic states this evening as the upper trough encroaches on
   the general region.  A broad warm-air advection regime north of the
   FL/GA early-day MCS will slowly destabilize today, aided in part by
   lower 60 deg F dewpoints north, mid to upper 60s south.  Long
   hodographs will favor storm organization with any robust updrafts. 
   Isolated to widely scattered strong to severe storms capable of a
   threat for damaging gusts and a couple of tornadoes are possible,
   mainly over parts of western VA, with lower coverage expected
   farther east over the coastal plain/Delmarva.

 

[high risk]

5 hours ago, yoda said:

SLGT risk moved into most of N VA and C MD on new Day 1 for 15 wind and 5 tornado 

  You have a VERY generous definition of "central".     

[Kmlwx]

12 minutes ago, high risk said:

  You have a VERY generous definition of "central".     

I was thinking the same thing after I read his message and then looked at the map lol

[yoda]

Both 12z NAM and NAM NEST have some decent curved and looping hodographs around 06z in the region with 300 m2/s2 with 500 to 1000 SBCAPE 

[yoda]

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1019 AM EDT Thu Apr 11 2024

.SYNOPSIS...
Low pressure will track into the Great Lakes today, with an
associated cold front moving through tonight. Upper troughing
will linger overhead tomorrow, with a reinforcing cold front
moving through tomorrow evening. High pressure will build to our
south this weekend. A weak area of low pressure will track to
our north late Sunday night into early Monday, before high
pressure regains control early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
1030 AM Update: Showers are starting to approach the area late
this morning with some partial clearing happening across
western portions of MD and the eastern WV panhandle.
Temperatures are already climbing into the mid to upper 60s
across the lower elevations. It is worth noting a dry slot
building in behind the initial cold front passage affecting
areas further south of our CWA. Discrete cells and clouds should
begin building back in through the early afternoon with
increasing rain chances.

[high risk]

2 hours ago, Kmlwx said:

I was thinking the same thing after I read his message and then looked at the map lol

    The environment certainly does look a bit more favorable later tonight than it had been, but I'm not seeing any decent UH tracks in any of the CAMs.

[yoda]

30 wind added in SW PA/W WV on 1630z OTLK 

[yoda]

1630z OTLK disco

 

   ...Mid-Atlantic States and Carolinas...
   A less focused and less certain severe risk appears to exist across
   the region. Cloud cover remains prevalent at midday coincident with
   low-level upslope flow, although some clearing is noted early this
   afternoon across the southern Appalachians vicinity. Where modest
   destabilization does occur this afternoon, long hodographs would
   conditionally support storm organization with any robust updrafts.
   Isolated to widely scattered strong to severe storms capable of a
   threat for damaging gusts and a couple of tornadoes are possible,
   particularly near the mountains/Blue Ridge, with a lower
   probability/lesser anticipated storm coverage expected farther east
   over the coastal plain/Delmarva.

 

[Disc]

Still a lot of cloud cover and drizzle across much of Virginia leading to a lot of uncertainty. If we can start to break out of the clouds, I think this has a decently high ceiling considering the parameter space in place.

CAMs are rather impressive with discrete cells forming in NC around 21z and then moving into Virginia and congealing more into a broken line as they progress into Central and Northern VA by 00z - 03z. Some impressive helicity tracks are noted moving into Southern Virginia, but wane a bit as they move north of I64, where I'd say this becomes more of just a wind threat. 

The new RRFS has been the most robust with this advertising multiple discrete cells, but the HRRR and NSSL/WRF models have a similar idea. I believe the WoFS will be run starting at 17z which has proven to be quiet skillful in the near term.

[Eskimo Joe]

Latest HRRR is pretty ho hum. Maybe some gusty showers overnight.

[Eskimo Joe]

It's pathetic...we're wasting a really, really good setup here because of bad timing.

[Kmlwx]

1 minute ago, Eskimo Joe said:

It's pathetic...we're wasting a really, really good setup here because of bad timing.

You got me a little more enthused when you said this storm wouldn't go quietly...but yeah the timing sucks. It has looked pretty meh for us from the get go. 

[Eskimo Joe]

Just now, Kmlwx said:

You got me a little more enthused when you said this storm wouldn't go quietly...but yeah the timing sucks. It has looked pretty meh for us from the get go. 

If we had yesterday's clearing with today's setup I'd be happy. 

[Eskimo Joe]

 

 

[southmdwatcher]

The new SPC outlook has pushed the 5 percent Tornado risk eastward to western Montgomery County, Dulles AIrport and down through VA just west of I95 south of Richmond

 

[southmdwatcher]

Yeah, that couplet was passing north of Blacksburg along the ridge and had a CC drop as well.