Severe Weather 3-31 through 4-3-24

[cheese007]

Another early week system with a big D5 15% and a D6 15% for outside this subforum.

 

ZCZC SPCSWOD48 ALL ACUS48 KWNS 280900 SPC AC 280900 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Thu Mar 28 2024 Valid 311200Z - 051200Z ...DISCUSSION... ...Day 4/Sunday: Mid Mississippi Valley into the Central/Southern Plains... The upper trough/low over the western states should slowly advance eastward towards the Southwest and southern/central High Plains on Sunday. Upper ridging is forecast to remain over the central/ southern Plains through Sunday night, which in tandem with a low-level temperature inversion should tend to suppress most convection. One possible exception may be along a sharpening warm front across MO/IL, where some guidance suggests elevated convection may form either Sunday morning, and/or Sunday night with strong low-level warm advection/lift occurring. Steepening mid-level lapse rates are forecast to overspread the mid MS Valley from the southwest through the period. These lapse rates, along with increasing moisture/instability in the presence of strong deep-layer shear, may support a risk for isolated supercells with associated threat for large hail. Regardless, confidence remains too low in this mainly elevated convection occurring, given upper ridging persisting, to add a 15% severe area for Sunday along/near the warm front in MO/IL at this time. ...Day 5/Monday: Southern/Central Plains into the Mid Mississippi and Ohio Valleys... Even though some differences remain in medium-range guidance regarding the ejection of an upper trough over the central CONUS on Monday, confidence has increased in the general location of relevant surface features, including the primary low, position of a southward-extending dryline, and northward extent of the warm front into the OH Valley. Even though the overall upper trough orientation may remain somewhat positively tilted, most deterministic guidance shows that a mid-level speed max and associated shortwave trough will eject northeastward over the southern/central Plains through Monday evening. Low-level mass response should encourage the eastward development of a surface low to the OK/KS vicinity in a similar time frame. Favorable low-level trajectories emanating from the Gulf will act to increase low-level moisture in tandem with steepening mid-level lapse rates and daytime heating across a broad warm sector extending from the southern/central Plains into the lower/mid MS Valley and OH Valley. A favorable thermodynamic and kinematic environment for organized severe convection will exist across much of these regions, with supercells capable of producing large hail and tornadoes possible initially. With time Monday evening/night, some upscale growth seems probable across the mid MS and OH Valleys, as mid-level flow should become increasingly parallel to a surface cold front. Therefore, a 15% severe area has been introduced for Monday where confidence is greatest that robust convection will develop in a parameter space characterized by weak/moderate instability and strong deep-layer shear. A nocturnal minimum in severe convective potential may be realized Monday night into early Tuesday morning across parts of the lower MS Valley into Mid-South, given the positively tilted nature of the upper trough. ...Day 6/Tuesday: Ohio/Tennessee Valleys into the Appalachians... Some severe threat should continue Tuesday over parts of the OH/TN Valleys into the Appalachians as the upper trough continues eastward. Even though there is still some uncertainty with the exact placement of the primary surface low and evolution of the upper trough, enough confidence exists in a fairly narrow corridor across these regions to add a 15% severe area for Tuesday. Rich low-level moisture should be in place ahead of an eastward-moving cold front. Redevelopment and/or re-intensification of convection seems probable by Tuesday afternoon. Strong deep-layer shear and weak instability should be sufficient for organized severe convection posing some threat for damaging winds, and perhaps tornadoes given the forecast strength of a low-level jet focused over parts of the OH/TN Valleys. The northward extent of the severe risk across OH and vicinity remains uncertain, as the placement of the warm front varies in model guidance. Similarly, convection should eventually encounter a less unstable airmass across the Appalachians. But, an isolated severe risk may continue Tuesday evening into early Wednesday morning across the southern/central Appalachians into portions of the Southeast. ...Day 7/Wednesday and Day 8/Thursday... Predictability remains too low to include a 15% severe delineation for Wednesday across the Mid-Atlantic/Southeast along/ahead of a cold front. By this extended time frame, there are significant differences in model guidance regarding the evolution of the upper trough, including its possible interaction/merging with a northern-stream trough, and placement of relevant surface features. Still, at least an isolated severe risk may persist Wednesday along/ahead of the eastward-sweeping cold front. Once this front clears the East Coast, severe potential appears minimal across the CONUS next Thursday. ..Gleason.. 03/28/2024 CLICK TO GET WUUS48 PTSD48 PRODUCT

[cheese007]

Monday got part of the risk area bumped to 30% in the D4, primary threat being hail but tornadoes and strong winds also likely

 

[Ed, snow and hurricane fan]

My new favorite You Tube and Twitter follow...  No video yet, but one is surely coming.

 

 

[Ed, snow and hurricane fan]

SPC is Enhanced for Day 3 with a hatched SigSevere for the I-35 corridor in Oklahoma and a small part of SE Kansas and SW Missouri.  Parsing the language, hail seems to be the biggest concern in Oklahoma but all hazards are possible.  GFS doesn't look that exciting to me, nor the NAMs near the end of their range, but I'm assuming the SPC people know what they are talking about.  Speed shear (and a lot of it, 70-80 knots, possibly why language about hail), but little change in wind direction surface to 500 mb.  If models are right, I'd think any tornado threat would be tied to low level boundaries.  The only one obvious at this time is the cold front/dry line, and surface/850 mb winds aren't that impressive.

 

Not seeing the MCS SPC thinks will develop late afternoon and evening, but again, at the farther edges of meso model range.

[Chinook]

Top synoptic analogs vary greatly in severe weather coverage. Most analogs here have some severe weather reports in Arkansas. There are not necessarily a lot of tornado analogs. As for now, I am not sure what I might want to post with the models. Instability seems a bit low.

 

84-hours

[Wmsptwx]

2 hours ago, Chinook said:

Top synoptic analogs vary greatly in severe weather coverage. Most analogs here have some severe weather reports in Arkansas. There are not necessarily a lot of tornado analogs. As for now, I am not sure what I might want to post with the models. Instability seems a bit low.

 

84-hours

Damn another dud possible incoming 

[cheese007]

Slight added for D1 with D2 and D3 sitting at ENH as of this morning. D2 adds a sigtor countour for much of southern MO into IL 

 

[Ed, snow and hurricane fan]

I was never in a risk area, down in HOU we never get storms from a positive tilted trough except sometimes a 'squeegie line' (as the HGX mets call thin lines of showers or storms right on the front).  But even yesterday, when DFW was Slight and OKC Enhanced, I did not see the low level response, and thus week low level winds, that would have done that much with the fairly 'meh' instability.  I still think there might be a supercell or two with big hail and a non-zero tornado risk in N. Central Texas and Oklahoma.  Could have been a big event with 

 

Anything after dark that forms ahead of the squall line or in an embedded bow in E. Oklahoma might have a chance to go tornadic although CINH may be an issue.  LLJ also picking up after dark, reaching 50 knots which could mix down

[Chinook]

According to a couple of models, the southernmost supercells could be by Dallas (possibly without the higher storm-relative helicity values)

 

[Powerball]

The latest SPC Day 1 Outlook has expanded the enhanced risk area to include all of North Texas (includiing DFW), mainly for hail.

[Powerball]

Much of Central OK and some of the Texas counties along the Red River have been upgraded to a Moderate Risk, again mainly for hail (45% hatched).

 

[Powerball]

Still a pretty brutal cap on the 20z FWD cap.

We'll see if the storms can prevail through it post-peak heating

 

[Chinook]

storms with weak rotation have put out 2" hail and one 88mph wind gust this afternoon

[Sydney Claridge]

The storm between Springtown and Boyd bears watching as it moves into the DFW metro area. The hail intensity on radar seems to be increasing.

 

 

[Chinook]

this is a confirmed tornado outside of Tulsa

[Chinook]

possible tornado near Dallas Fort Worth, also, hail reports from other storms shown

[cheese007]

Ohio Valley under the gun today with a big 15% sigtor hatched risk. D2 also has a slight risk for parts of FL and the mid-Atlantic

SPC AC 020600

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Tue Apr 02 2024

   Valid 021200Z - 031200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO
   VALLEY...

   ...SUMMARY...
   A potentially substantial severe weather outbreak -- possibly
   including a few significant/long-track tornadoes -- is anticipated
   this afternoon and evening, with the highest probability centered
   over the Ohio Valley.  Severe risk exists as far south as the Gulf
   Coast, and as far east as western portions of Virginia and the
   Carolinas.

   ...Discussion...

   Strong northern-stream upper low, currently located over southern
   MB, is forecast to drop south across MN into northern IL late in the
   period. This evolution is driven in part by a 500mb speed max that
   will translate across the central Plains, increasing to near 100kt
   over eastern KS/OK by 03/12z. Intense 12hr midlevel height falls are
   forecast across much of the Great Lakes, OH/TN Valley, and the
   northern Gulf States, where values in excess of 200m are expected
   during the latter half of the period. Synoptic front that is
   currently draped across the OH Valley will be encouraged to
   gradually advance north due to the digging trough; however, an
   extensive corridor of convection currently extends across the MS
   Valley into the OH valley, which is maintaining cool boundary-layer
   conditions north of I-70.

   Latest water-vapor imagery suggests a southern-stream short-wave
   trough is progressing across eastern KS/eastern OK. This feature
   will progress downstream and likely aid early-day thunderstorm
   development near the confluence of the MS/OH Rivers. Seasonally high
   PW airmass currently extends across northern AR/southern MO into
   southern IL. NAM forecast sounding for JBR at 15z exhibits 60kt
   surface-6km bulk shear with SBCAPE on the order of 1500 J/kg.
   Discrete supercells may evolve ahead of this feature then
   spread/develop northeast across southern IN/KY into OH. Some
   uncertainty exists across northern OH/IN regarding destabilization.
   It's not entirely clear if ongoing convection will allow the warm
   front to lift appreciably north of its current position. However,
   large-scale pattern is quite dynamic and favors surface low
   deepening over southern Lake MI during the latter half of the
   pattern. NAM struggles to reflect this scenario, thus weaker
   instability is forecast at higher latitudes. Tornadoes, damaging
   winds, and large hail are expected with supercells that evolve
   across the warm sector. Some tornadoes may be long-lived and strong.


   Farther south, a bimodal severe threat may ultimately evolve with a
   secondary corridor of more concentrated severe across portions of
   the northern Gulf States. 500mb speed max is forecast to eject
   across northern Mexico into TX by 03/00z. This feature will
   intensify as it translates across LA into eastern TN by the end of
   the period. There is some concern that severe probabilities may need
   to be increased across this region to account for this low-latitude
   speed max during the evening/overnight hours. Strong shear will
   support supercells along with a threat for tornadoes, damaging
   winds, and hail.

   ..Darrow/Bentley.. 04/02/2024