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BrandonC_TX

Severe Weather March 15-19

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There is still a lot of uncertainty concerning the extent of the severe thunderstorm threat that could materialize later this week (anywhere from the southern Plains to possibly as far northeast as the Great Lakes), such that SPC has not yet delineated a risk area for Thursday, the day which would probably have the highest severe storm risk.  Nevertheless, multiple weather models (GFS, Euro, Canadian, UKMET, plus the most recent NAM runs) all show lee cyclogenesis of a significant storm system over the Colorado vicinity.  All of these models have also shown a broad moist warm sector ahead of the storm system.

Given all this, it seems like there is going to be severe weather, but the intensity and extent of it is still uncertain.

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On Tuesday evening will have a dryline near the Pecos River, but perhaps not a lot will happen. The first interesting part of this could be Wednesday evening around Lubbock to Midland/Odessa. The low-level convergence there will be a weak cold front, with 50-55kt winds at 500mb over the region. The models have upper 40's dew points into SE New Mexico, that's why it won't be a dryline.

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The end of tonight's 0z NAM run definitely looks like it could be pretty amped I would say, with good ingredients for severe weather in place from NW TX and into western OK on Wednesday, not to mention decent helicity in place over the broad warm sector Thursday morning.  However, it also models precipitation within the warm-air advection from Texas to the KS/MO border region on Thursday morning, just like SPC said might act to temper the severe weather threat somewhat later in the day ("crapvection" I guess?).  It is just one model run, though, so I'll take it with a grain of salt. 

Nevertheless, the warm sector looks as if it will extend from Texas all the way up to Ohio.  GFS, Euro, GDPS and UKMET even suggest some instability could reach into the Northeast (mainly upstate NY and PA) by Friday.

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There is a cluster of warned severe thunderstorms out in far western Texas right now.  Some of the NAM, RAP, and HRRR runs have me a little bit concerned about the possibility of a "sleeper" severe thunderstorm and/or tornado threat in north-central Texas this evening into the overnight, as a boundary appears to stall over the DFW area with strongly backed surface winds along the boundary.  If this scenario verifies and a storm can latch on to that boundary, it might become a bit troublesome.

Interestingly enough, there is also a severe thunderstorm watch up for the island of Kauai in Hawaii.  (This isn't displayed on SPC's page as a watch since we are talking OCONUS here)

EDIT: a severe thunderstorm watch is now out for the areas around Lubbock.  Severe-warned storm west of Lubbock is taking on supercellular characteristics based on radar.

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4 hours ago, BrandonC_TX said:

There is a cluster of warned severe thunderstorms out in far western Texas right now.  Some of the NAM, RAP, and HRRR runs have me a little bit concerned about the possibility of a "sleeper" severe thunderstorm and/or tornado threat in north-central Texas this evening into the overnight, as a boundary appears to stall over the DFW area with strongly backed surface winds along the boundary.  If this scenario verifies and a storm can latch on to that boundary, it might become a bit troublesome.

Interestingly enough, there is also a severe thunderstorm watch up for the island of Kauai in Hawaii.  (This isn't displayed on SPC's page as a watch since we are talking OCONUS here)

EDIT: a severe thunderstorm watch is now out for the areas around Lubbock.  Severe-warned storm west of Lubbock is taking on supercellular characteristics based on radar.

Totally agree.  Not sure if you read NWS discussion but it mentions low level vorticity along the frontal boundary, which one normally wouldn't think to look at (usually 500mb is observed more frequently). Anyways it appears between 21-03Z that front lifts north, not only providing necessary lift, but also good WAA/Theta E advection and then throw in the increased shear in that timeframe could be an eventful evening.  Expecting storms to fire up south of I-20 after about 3-4pm.  Could see some become severe warned shortly thereafter as the environment they will be moving into becomes more favorable.  Looks like the front is currently just south of Corsicana which is also evident on radar too.

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Storms down by Corsicana could become a concern for the eastern half of DFW if they strengthen and continue their due-northward motion.  They are currently sub-severe, although there may be an increase in parameters for supercells with time.

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Might want to watch that area along the I-35E corridor between Italy and Waxahachie for the development of a potential hook.  Conditions are not particularly favorable for strong rotation (EHI values, both 0-1km and 0-3km, are between 1 and 2), but the storm may be taking on supercellular characteristics based on the radar signature.  This storm is also moving straight towards Dallas as well, and if it strengthens it could pose a severe thunderstorm threat.

Fortunately there is no velocity couplet, and the storm is sub-severe, but I will be watching the I-35E corridor.

92CF6E84-2610-4B5B-BC7F-27403122647D.png

 

Meanwhile, the severe storms north of Abilene (around Haskell and Stamford) look pretty healthy (albeit the one around Stamford seems outflow-dominant based on the radar), and appear to be riding the boundary, although EHI values there are similar to the storm south of Dallas.  The storm just SE of Haskell also appears to have broad rotation and needs to be watched.

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18 minutes ago, BrandonC_TX said:

Might want to watch that area along the I-35E corridor between Italy and Waxahachie for the development of a potential hook.  Conditions are not particularly favorable for strong rotation (EHI values, both 0-1km and 0-3km, are between 1 and 2), but the storm may be taking on supercellular characteristics based on the radar signature.  This storm is also moving straight towards Dallas as well, and if it strengthens it could pose a severe thunderstorm threat.

Fortunately there is no velocity couplet, and the storm is sub-severe, but I will be watching the I-35E corridor.

Yeah I'm tracking that storm right now on GR2. Had to go out and move my car in the garage I don't trust that thing lol.  Certainly has some hail in it but rotation isn't evident at this time however now is the time that wind shear is over us.

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18 minutes ago, It's Always Sunny said:

Yeah I'm tracking that storm right now on GR2. Had to go out and move my car in the garage I don't trust that thing lol.  Certainly has some hail in it but rotation isn't evident at this time however now is the time that wind shear is over us.

Fortunately it looks to be a disorganized mess right now, and they seem to have split into three cells.  Meanwhile, I’ll watch the storms out by Sweetwater (currently sub-severe) to see if they try to exploit that outflow boundary left behind from the previous storms.

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Looks like this supercell between Throckmorton and Newcastle might be trying to get ahead of the outflow boundary.

 

 

35647770-DD25-429D-8AB5-CCA09454ADE5.png
 

Meanwhile temperatures in the southern reaches of the DFW area (eg. Burleson) have warmed into the lower 70s as the boundary slowly moves north.  SPC lowered severe probabilities but if we can get a severe storm it could still be problematic.

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I know the HRRR can be aggressive at times with storm initiation and severe storm parameters, but I thought it was worth mentioning that tonight's 0z HRRR run puts isolated supercells through both the northwestern DFW and San Antonio metro areas around 10pm tomorrow evening.  I'm not focusing too much on the particular placement though, just the possibility that there might be storms in a potentially-favorable environment.  (For instance, if I remember correctly, I believe the HRRR did predict the tornadic supercells on October 20th, 2019, whereas some other models did not catch on to initiation prior to the overnight squall line; I'm not trying to say it will be as bad as 10/20/19 though, especially considering SPC currently says that the risk for DFW tomorrow is only marginal-to-slight)

refcmp_uh001h.us_sc.thumb.png.68c03145a123419ec213a2171043833f.png

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I'm currently (~4:45am) having constant rain in west Fort Worth with the occasional rumble of thunder.  All this rain is too much of a good thing, enough that I'm starting to get concerned about low-lying areas if we get too much more rain. Also glad the severe weather potential here has died down... for now.

Several HRRR runs (06z, 07z and 08z runs, plus the aforementioned 0z run) have consistently tried to initiate supercells in the DFW vicinity for this evening.  Other convection-allowing models (at least the ones on Pivotal Weather) are not really showing this potential, aside from the 0z run of the HRW-NMMB.  Some of the RAP runs may be trying to do something in north-central Texas as well, not to mention the 06z run of the NAM.

EDIT: the 09z HRRR struggles a bit more with early evening convective initiation around DFW.  The 10z HRRR run goes back to putting supercells over DFW, and with favorable parameters it could be scary if it verifies (though it is just one run of one model).

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Latest SPC outlook (midday Wed)

Primary change to previous outlook has been to increase tornado
   probabilities across west central into northwest through north
   central TX area. An old outflow boundary will persist in this
   region, but should become more diffuse with time. Several CAM runs
   and especially the HRRR continue to initiate storms in warm sector
   by late afternoon initially along the dryline across west central
   TX. This initiation would be in advance of primary zone of forcing
   associated with the shortwave trough currently moving through
   northern Mexico. While 0-1 km shear will initially be weak/modest,
   an increase in the low-level jet during the early evening within an
   otherwise favorable deep-layer shear environment will support
   potential for supercells with low-level mesocyclones, tornadoes and
   very large hail as storms move northeast toward central through
   northwest and north central TX this evening. Otherwise additional
   storms will likely develop across west TX along retreating dryline
   during the evening and spread east through TX and OK during the
   overnight. The shear/instability parameter space will support
   organized storms with potential for linear/bowing segments as well
   as supercells capable of all severe hazards. 

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7 minutes ago, JMT417 said:

Large upgrade area in new Day 2 outlook

Yeah I was literally just looking at that.  My biggest concern will be timing to destabilize after today's weather and then any cloud cover overnight and tomorrow morning. All the other ingredients are there though although I feel that mid-level lapse rates could be better but when you have that type of shear, low level moisture and CAPE exceeding 1000 J/kg lapse rates don't need to be as steep.

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Fortunately for the DFW area the HRRR runs have shifted the area of evening supercell initiation further west a couple of counties (compared to my earlier posts), so I am little bit less concerned about supercells in the Metroplex.  But I'm not going to discount the possibility either, especially with the east edge of the 10% hatched tornado risk in Tarrant and Denton counties.  And it seems the sun is trying to come out here in west Fort Worth.

I also shifted the date in this thread to better reflect the end of the severe weather threat for this subforum.

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As for the 20z HRRR, there is really only one major thunderstorm with a helicity track, and that's 2-4 counties west of Fort Worth. I expected the HRRR to have more of these.

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1 hour ago, BrandonC_TX said:

Fortunately for the DFW area the HRRR runs have shifted the area of evening supercell initiation further west a couple of counties (compared to my earlier posts), so I am little bit less concerned about supercells in the Metroplex.  But I'm not going to discount the possibility either, especially with the east edge of the 10% hatched tornado risk in Tarrant and Denton counties.  And it seems the sun is trying to come out here in west Fort Worth.

I also shifted the date in this thread to better reflect the end of the severe weather threat for this subforum.

WSI RPM 18Z model keeps cells over Wise/Jack counties which is similar to HRRR output but I'm still as equally concerned as earlier about cells getting close to the Metroplex.  Runs can flip-flop with how far east/west they want to bring the cells my main takeaway is the potential is there for storms in the Metroplex (not so much the placement).  Those leading cells on the HRRR are a little out of place in my opinion looks like it is sparking them off a little sfc convergence boundary that currently doesn't even exist on real time obs so it'll be interesting to see if they develop in the next hour or so.  The one south of MAF makes sense because that's where the boundary actually is.

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Last time I recall uncertainty like this was back on October 20, 2019, when we had tornadic supercells form over DFW.  That is very much the worst-case scenario though (not in terms of injuries/fatalities but monetary damages), and the effects from that day were more about where the tornado(es) hit, thus the high monetary damages were such due to damage in industrial parks and commercial properties along with affluent residential neighborhoods like Preston Hollow.  We don't even know where supercells will try to form until they go up, so I am not saying today's threat will wind up anything like 10/20/19, but in a situation where a supercell goes through the Metroplex with favorable parameters, the potential for a damaging hit is not completely out of the question.

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1 hour ago, BrandonC_TX said:

Fortunately for the DFW area the HRRR runs have shifted the area of evening supercell initiation further west a couple of counties (compared to my earlier posts), so I am little bit less concerned about supercells in the Metroplex.  But I'm not going to discount the possibility either, especially with the east edge of the 10% hatched tornado risk in Tarrant and Denton counties.  And it seems the sun is trying to come out here in west Fort Worth.

I also shifted the date in this thread to better reflect the end of the severe weather threat for this subforum.

I'm by TCU....wind here has picked up quite a bit in the last couple of hours

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1 minute ago, BrandonC_TX said:

Last time I recall uncertainty like this was back on October 20, 2019, when we had tornadic supercells form over DFW.  That is very much the worst-case scenario though (not in terms of injuries/fatalities but monetary damages), and the effects from that day were more about where the tornado(es) hit, thus the high monetary damages were such due to damage in industrial parks and commercial properties along with affluent residential neighborhoods like Preston Hollow.  We don't even know where supercells will try to form until they go up, so I am not saying today's threat will wind up anything like 10/20/19, but in a situation where a supercell goes through the Metroplex with favorable parameters, the potential for a damaging hit is not completely out of the question.

Yeah I agree not only was Dallas like that but the one in Nashville recently did the same exact thing where it was a severe warned thunderstorm then all of a sudden just dropped a tornado and it became instantaneously tornado warned.

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BULLETIN - EAS ACTIVATION REQUESTED  
SEVERE THUNDERSTORM WARNING  
NATIONAL WEATHER SERVICE SAN ANGELO TX  
538 PM CDT WED MAR 18 2020  
  
THE NATIONAL WEATHER SERVICE IN SAN ANGELO HAS ISSUED A  
  
* SEVERE THUNDERSTORM WARNING FOR...  
  CENTRAL CALLAHAN COUNTY IN WEST CENTRAL TEXAS...  
  NORTHEASTERN COLEMAN COUNTY IN WEST CENTRAL TEXAS...  
  
* UNTIL 630 PM CDT.  
  
* AT 537 PM CDT, A SEVERE THUNDERSTORM WAS LOCATED NEAR ROWDEN, OR 16  
  MILES SOUTH OF BAIRD, MOVING NORTHEAST AT 35 MPH.  
  
  HAZARD...TENNIS BALL SIZE HAIL AND 60 MPH WIND GUSTS.  
  
  SOURCE...RADAR INDICATED.  
  
  IMPACT...PEOPLE AND ANIMALS OUTDOORS WILL BE INJURED. EXPECT HAIL   
           DAMAGE TO ROOFS, SIDING, WINDOWS, AND VEHICLES. EXPECT   
           WIND DAMAGE TO ROOFS, SIDING, AND TREES.  
  
* THIS SEVERE THUNDERSTORM WILL BE NEAR...  
  ROWDEN AROUND 545 PM CDT.  
  CROSS PLAINS AROUND 600 PM CDT.  
  ATWELL AROUND 610 PM CDT.  

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