March 7th-9th, 2024 Severe Weather

[cheese007]

SPC highlighting a multi-day severe event running from March 7th through the 9th. 15% contours have already been introduced for D4 into D5 with less certainty re: D6

ZCZC SPCSWOD48 ALL
   ACUS48 KWNS 041000
   SPC AC 041000

   Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CST Mon Mar 04 2024

   Valid 071200Z - 121200Z

   ...DISCUSSION...
   A multi-day severe event appears increasingly probable for the
   latter portion of this week into the early weekend. For Day
   4/Thursday, a 15% severe area has been introduced across parts of TX
   into the lower MS Valley for mainly a large hail threat Thursday
   night into early Friday morning. A southern-stream upper trough is
   forecast to eject across the Southwest/northern Mexico into the
   southern Plains in this time frame. Steep mid-level lapse rates
   should overspread the gradually destabilizing warm sector, with the
   ECMWF and its ensemble in particular suggesting that ample MUCAPE
   will be available Thursday night across parts of north-central into
   east TX. Any thunderstorms that can initiate in the strengthening
   low-level warm advection regime across this region should pose a
   threat for large hail given ample cloud-bearing shear to support
   elevated supercells. Some of this activity could become
   near-surface-based towards 12Z Friday morning across the lower MS
   Valley as surface dewpoints quickly increase into the mid/upper 60s.

   The severe threat will likely continue into Day 5/Friday, where a
   15% severe area has been introduced from east TX into the lower MS
   Valley and parts of the central Gulf Coast states. There is still
   some uncertainty in guidance regarding the ejection of the upper
   trough and placement of related surface features. Regardless, there
   is enough agreement that rich low-level moisture will advance inland
   across these areas to support a threat for surface-based convection
   ahead of whatever activity develops across north-central TX late
   Thursday night into early Friday morning. Forecast soundings from
   both the GFS and ECMWF show strong effective bulk shear that will
   support the potential for supercells producing large hail, damaging
   winds, and tornadoes. Convection may also grow upscale into bowing
   line segments while continuing to pose a threat for severe/damaging
   winds and a few tornadoes. The main uncertainty remains how far
   inland/north the warm sector will be able to advance, particularly
   across MS/AL. For now, have opted to remain conservative with the
   northward extent of the 15% severe area by highlighting where at
   least mid 60s surface dewpoints appear probable.

   Some severe risk may persist into Day 6/Saturday across parts of the
   Southeast towards the Carolinas. However, model guidance shows
   substantial spread in the evolution of the upper trough at this
   extended time frame. Convection may also have a tendency to outpace
   the developing warm sector with time. While parts of FL/GA/SC/NC
   will be monitored for possible inclusion in a 15% severe area in
   later outlooks, predictability for early this weekend remains too
   low at this time.

   ..Gleason.. 03/04/2024

[Ed, snow and hurricane fan]

MBY not included.  Positive tilt systems always mean I-10 area SAT to HOU is always capped.

 

WE could use the rain here, the drought has ended but it has been a dry 6 weeks.  Even into the Gulf Coast Friday, GFS seems to show capping that would be hard to break.

[Stx_Thunder]

On 3/4/2024 at 5:01 AM, Ed, snow and hurricane fan said:

MBY not included.  Positive tilt systems always mean I-10 area SAT to HOU is always capped.

12 Z runs yesterday and today on both GFS & Euro are starting to show a forecast trend in less convective CIN in S-SETX (including Houston area), Friday morning ahead of the initial Pacific front/dryline (dry, modest polar reinforcing front Friday night). But even though moisture, and DL shear is looking good (generally 60 kts) on both globals, forecast ML Lapse Rates aren’t (< 7) and seems to be trending lower. CAPE modest also (but sufficient). So that’s likely going to tamper atmospheric instability and severe hail, lightning threat a bit if storms happen. SRH values aren’t great also.

Timing of frontal passage and 700 MB Low track over the TX Panhandle on those 12 Z runs comparison seems to be slowing down a little too. That could allow for a little better dynamics aloft. And instability on Friday in the lower levels and surface if frontal passage is indeed later midday.

Will be interesting to see what CAMs (especially HRRR & ARW-2 as those have been doing the best lately), show when the time period comes into window tomorrow night. But since it is a positive-tilt (but formidable) incoming mid-upper trough being shown, I still wouldn’t be surprised if timing of shortwave energy ends up being somewhat out of sync with frontal passage in SETX. Though that’s usually a bigger problem with fronts further southwest in STX even if environment is favorable for storms. Especially this time of year.

 

[Ed, snow and hurricane fan]

1 hour ago, Stx_Thunder said:

12 Z runs yesterday and today on both GFS & Euro are starting to show a forecast trend in less convective CIN in S-SETX (including Houston area), Friday morning ahead of the initial Pacific front/dryline (dry, modest polar reinforcing front Friday night). But even though moisture, and DL shear is looking good (generally 60 kts) on both globals, forecast ML Lapse Rates aren’t (< 7) and seems to be trending lower. CAPE modest also (but sufficient). So that’s likely going to tamper atmospheric instability and severe hail, lightning threat a bit if storms happen. SRH values aren’t great also.

Timing of frontal passage and 700 MB Low track over the TX Panhandle on those 12 Z runs comparison seems to be slowing down a little too. That could allow for a little better dynamics aloft. And instability on Friday in the lower levels and surface if frontal passage is indeed later midday.

Will be interesting to see what CAMs (especially HRRR & ARW-2 as those have been doing the best lately), show when the time period comes into window tomorrow night. But since it is a positive-tilt (but formidable) incoming mid-upper trough being shown, I still wouldn’t be surprised if timing of shortwave energy ends up being somewhat out of sync with frontal passage in SETX. Though that’s usually a bigger problem with fronts further southwest in STX even if environment is favorable for storms. Especially this time of year.

 

Looking at Euro 24 hour precip Friday, there will be storms that track just N of us.  It looks better than the GFS for some needed rainfall but still showing SW flow in the 850-700 mb levels.  I fear a dry Spring leading to the feedback that produces another 2 months plus of 100F temps around here.  I think Euro's 250 mb RR entrance may be helping overcome a bit of the CINH, it would be nice if that whole thing edges a smidge S for better jet support.  In your neck of the woods, I'm waiting for the under forecasted severe storms that form over the mountains in Mexico and drift across the river in the evening.  I've seen pictures of big hail and damage from those storms.  And there is actually more than 1 image of the net of the bats in the W Hill Country getting ingested into supercells.  I found out they live under bridges in Houston as well after the last hard freeze stunned many, living in Austin late 80s/early 90s, I thought the bridge bats were unique to there.

[Chinook]

Severe weather outlooks for this week:  Honestly I'm not sure what so say regarding this. I don't think a lot will get going tomorrow in the daytime. There should be more severe activity popping up from 12z to 18z Friday, along with up to 65 kt of shear in Louisiana at that time. The GFS shows high storm relative helicity in Mississippi.

 

 

This is a sounding near Biloxi for Friday with low-CAPE, high humidity

 

[Chinook]

Friday night could have an enhanced risk for tornadoes

[Stx_Thunder]

On 3/5/2024 at 7:13 PM, Ed, snow and hurricane fan said:

Looking at Euro 24 hour precip Friday, there will be storms that track just N of us.  It looks better than the GFS for some needed rainfall but still showing SW flow in the 850-700 mb levels.  I fear a dry Spring leading to the feedback that produces another 2 months plus of 100F temps around here.  I think Euro's 250 mb RR entrance may be helping overcome a bit of the CINH, it would be nice if that whole thing edges a smidge S for better jet support.  In your neck of the woods, I'm waiting for the under forecasted severe storms that form over the mountains in Mexico and drift across the river in the evening.  I've seen pictures of big hail and damage from those storms.  And there is actually more than 1 image of the net of the bats in the W Hill Country getting ingested into supercells.  I found out they live under bridges in Houston as well after the last hard freeze stunned many, living in Austin late 80s/early 90s, I thought the bridge bats were unique to there.

GFS, Euro, and all CAMs holding onto eroded sfc-based CIN over SETX midday - late afternoon today (Friday).- - -

Wouldn’t hope for a dry spring too soon especially coming out of a fairly wet EN winter and active MJO pattern since the beginning of the year. GFS/Euro and their ensembles starting to latch onto a potentially more convectively active pattern later next week into next weekend over TX (and potentially through the early half of Spring). Looking at CFS longer range depictions also, it may not be useful in temp forecasting for a month out, but that is not necessarily the case regarding precip looking at its spring depictions since the past few years over TX. Keep in mind for later spring that May is typically spring MCS guarantee month also. Over the years, it rarely fails to have at least one or two good thunder systems impacting much of the state (especially eastern/southern half) during that month.

MJO activity was relatively inactive the past weeks. But is also forecast to ramp up again out over the tropical Pacific in the coming weeks with a new activity wave progressing eastward. So that will likely have an impact on convective activity (potential severe) over the state due to enhanced subtropical jet influence as well in the coming weeks.

The afternoon heat + orographically induced storms or discrete supercells out over the Mexican terrain (west of Laredo/Rio Grande) usually startup in March most years. The Euro is showing that could be happening mid-late next week as some more shortwave energy starts to come in from the west aloft in the southern stream, with hotter afternoon temps happening out there closer to or around 100 F on both GFS & Euro.

- - - - -
By the way, those bats you mentioned are called ‘Mexican free-tailed bats’ if I remember correctly. I do remember reading an article Austin/San Antonio NWS (as they’re very common in that region of TX) wrote about them back in the 2000s. Especially how they cause the donut-looking ground clutter depictions right around the radar site location on DFX & EWX radars like you referenced when the bats come out in huge numbers together at sunset during spring season.

* Found detailed info on those bats:

https://en.wikipedia.org/wiki/Mexican_free-tailed_bat