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Severe weather risk 3-28 and 3-29 2017


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Lets get this started

 

SPC has an day 3 enhanced and slight risk outlook for parts of NW/W TX on 3-28-17, and a day 4 outlook 15% severe covering large portion of Western/Eastern and Central Texas.  (Also included on day 4 are parts of  OK, LA and most of ARK.)

 

 

Edit: Tuesdays Map was updated during this post so will also post the new updated map.  I'll also will leave the original one here to compare if needed.

 

day3otlk_0730.gif?1490593773971

 

day4prob.gif?1490593829369

 

 

Update day 2 map

 

day2otlk_0600.gif?1490594174877

 

 

 

There are still uncertainties regarding the details of this setup. 
   Most models suggest that considerable thunderstorm activity will
   occur Tuesday morning over the TX Panhandle and northwest OK.  This
   will likely modulate the position of the warm front, and perhaps the
   northern extent of greatest threat.  Therefore will maintain the
   ongoing ENH risk, with consideration for upgrade to MDT risk in
   later outlooks.
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A few images from the 00z NCAR ensemble indicating the potential tomorrow has in W-Central TX. Seems reasonable to expect a southern shift given the possibility of earlier convection stalling the warm front.

23z neighbourhood probs of echo tops >35k feet within 25 miles of a point.

echotop_neprob_35000.0_f047_SGP.png

 

23z neighbourhood probs of UH >150 m2/s2 within 25 miles of a point (this is a substantial signal for 47 hours out).

hmuh_neprob_150.0_f047_SGP.png

 

00z probability of STP exceeding 3 within 25 miles of a point.

stp_neprob_3.0_f048_SGP.png

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2 hours ago, bjc0303 said:

not sure I'm sold on such a southward shift but the NCAR ensemble is interesting. initiates pretty early too.

Yeah, I wouldn't be sold on it; the NCAR ensemble seems to have problems being under-dispersive, where most or all the members will agree closely on scenarios that end up not verifying. That was the case with its 48 h moisture forecast for yesterday's OK event.

I can't get a good handle on tomorrow at all. Widespread early CI looks very likely (doing its best 2015 impression). Interestingly, both NCEP HRW runs develop scary supercells over SW OK by late afternoon that evolve out of storms that initiated much earlier in W TX. This is a true lifting warm front setup with rich moisture, something we don't see all that often in this region and may require some adjustment in expectations (e.g., I very rarely have much faith in Plains convection that initiates before 19-20z ever going on to become interesting).

The meridional component of midlevel flow over NW TX/SW OK varies enough between solutions to make a lot of difference in mode and SRH. If we can stay veered of SSW, I think the potential for at least a few tornadoes is substantial. Whether they're pretty or not is another matter.

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Hello all!! Ready for spring tornado season here in OK. I'm a bit of a noob on a few things although much thanks to many of you who have helped me on reading reports and models and what to focus on. 

 

Got a question in reference to abbreviations. 

 

 when someone posts CI are they referring to cirrus clouds or convective inhibition or initiation. I've most often seen Inhibiton as CINH. 

 

Thanks and keep up what everyone does here. It has helped me get over a lot of anxiety by understanding the forecasts better than watching the local mets and preparing friends and family who otherwise are too often don't pay attention living in OK all there lives despite some of the worst events over the years

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1 hour ago, Misstertwister said:

Hello all!! Ready for spring tornado season here in OK. I'm a bit of a noob on a few things although much thanks to many of you who have helped me on reading reports and models and what to focus on. 

 

Got a question in reference to abbreviations. 

 

 when someone posts CI are they referring to cirrus clouds or convective inhibition or initiation. I've most often seen Inhibiton as CINH. 

 

Thanks and keep up what everyone does here. It has helped me get over a lot of anxiety by understanding the forecasts better than watching the local mets and preparing friends and family who otherwise are too often don't pay attention living in OK all there lives despite some of the worst events over the years

Depends on context. In reference to what Brett was saying, I believe he is referring to "convective initiation". 

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Lots of early/ongoing convection on the HRRR....tomorrow reminds me a little like 5/16/15 in a sense, obviously with lesser moisture tomorrow among some other different things. I remember the night before the HRRR had morning convection but it was able to clear out to the northeast, just had to get as far south as possible with new storms developing south in the steep low level lapse rates. What is interesting is some of that HRRR convection on the souhern end is in fairly decent environment and you could have elevated storms early become suface based as warm front lifts north. Several scenarios on the table with this one tomorrow and not entirely sure which one will play out.

 

HRRRSGP_prec_radar_018.png.5b8b9c58cd48addb2a3bcab89b17af8a.png

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17 minutes ago, Thundersnow12 said:

Lots of early/ongoing convection on the HRRR....tomorrow reminds me a little like 5/16/15 in a sense, obviously with lesser moisture tomorrow among some other different things. I remember the night before the HRRR had morning convection but it was able to clear out to the northeast, just had to get as far south as possible with new storms developing south in the steep low level lapse rates. What is interesting is some of that HRRR convection on the souhern end is in fairly decent environment and you could have elevated storms early become suface based as warm front lifts north. Several scenarios on the table with this one tomorrow and not entirely sure which one will play out.

 

HRRRSGP_prec_radar_018.png.5b8b9c58cd48addb2a3bcab89b17af8a.png

HRRRX is pretty tame as far as morning convection goes.. And unless I'm mistaken lifts the warm front *well* into OK. Seems unlikley...

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It seems like most models have a very messy looking setup. Maybe you could get lucky targeting the southern end of the line or if a stray storm rides the warm front you could have a chance at seeing something but so far this is just a little too messy looking for me to want to try and chase. I'd take Sunday's setup over this one.

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8 minutes ago, WhiteoutWX said:

It seems like most models have a very messy looking setup. Maybe you could get lucky targeting the southern end of the line or if a stray storm rides the warm front you could have a chance at seeing something but so far this is just a little too messy looking for me to want to try and chase. I'd take Sunday's setup over this one.

Yesterday's?

 

I question some model output. As brett noted, some high res guidance is suggestive of serious potential. Models are forecasting an environment supportive of significant severe. NAM 3km in particular produces weak looking convection even for a line. Honestly not sure why - linear mode? Sure, but the storms look very benign for the environment they would be in. Forecast environments look very favorable for all modes of severe with an expected storm mode imo of a mixed mode event. Any discrete/semi-discrete storms would pose significant threats.

Short of an early day MCS wrecking the moist sector I cannot see some of these solutions panning out. Could I see a rapid upscale growth evolution? Sure. 

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37 minutes ago, bjc0303 said:

Yesterday's?

 

I question some model output. As brett noted, some high res guidance is suggestive of serious potential. Models are forecasting an environment supportive of significant severe. NAM 3km in particular produces weak looking convection even for a line. Honestly not sure why - linear mode? Sure, but the storms look very benign for the environment they would be in. Forecast environments look very favorable for all modes of severe with an expected storm mode imo of a mixed mode event. Any discrete/semi-discrete storms would pose significant threats.

Short of an early day MCS wrecking the moist sector I cannot see some of these solutions panning out. Could I see a rapid upscale growth evolution? Sure. 

Yes I meant yesterday. I'm not saying there won't be severe weather or even multiple tornadoes. I was speaking purely from a chasing perspective it looks really messy and could be hard to target any particular storm.

 I would much prefer a day with only a couple potential targets.

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24 minutes ago, WhiteoutWX said:

Yes I meant yesterday. I'm not saying there won't be severe weather or even multiple tornadoes. I was speaking purely from a chasing perspective it looks really messy and could be hard to target any particular storm.

 I would much prefer a day with only a couple potential targets.

It's looking more and more that way, as all the CAMs tonight have trended south with the WF and depict a repulsive convective evolution, despite embedded high UH swaths. It looks like a concoction of May 7-8, 2015, and April 9, 2008 (Breckenridge event). Really miserable stuff to be out in, I can say from experience. H5 flow is more meridional tomorrow than any of those events, so I'm still unsure on the substantial tornado potential, but I'd be very surprised if we see any classic, discrete supercells producing them.

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The convection-allowing models show storms popping at 19-20z. A couple of chasers may hit tornadoes if storms can become surface based early, before storms get too numerous and messy.  The WRF-ARW is very suggestive of large squall lines. Flooding may be an issue.

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44 minutes ago, monsoonman1 said:

New day 2 mentions strong tornadoes and MDT upgrade possible for AR/LA on Wednesday.

Day 2 (Wednesday) The NAM and 3km NAM show STP values up to 4, with SRH values of 400 m2/s2, for areas of extreme east Texas. That is within an environment of 70 temp, 70 dew point (near 100% RH)

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NCAR ensembles continue to like farther south, showing a strong signal for a cluster of supercells immediately ahead of an arcing dryline in the vicinity of ABI and points east. Unlike Sunday, moisture return will be more favorable leading up, (e.g. low to mid 60s dew-points at peak heating). The ensemble mean shows widespread >2000 J/kg MLCAPE through the warm sector. 

7925F6A9-5E90-4DD6-BDF4-485DA364A1FD-3283-00000233F35BA134.thumb.png.7ee9f16d6ea3a3205691dec0c931fc2e.png

8F372824-4A9D-4A05-9D46-4F5B5EB8C892-3283-0000023478240E55.thumb.png.5a8648c28225765d3b9cc77d6432d3f0.png

Another note is that short-term CAMs are less aggressive with morning convection, but still show a very messy evolution of storms up near the low and along the warm front during the afternoon. 

Things could still get messy with semi-discrete cells farther south, but the best parameter space should be found there. The HRRR is displaced a bit more NW of the NCAR prog below.

8213CB07-B2BC-4E24-88B4-DF912E5A0E04-3283-00000232CAD4C6C2.thumb.png.aa143e9534a06f58d1c065cf05053489.png

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Everyone will be targeting further north into Texas but man if a storm can go up in the HRRR progged environment from I-10 down to DRT...bulk shear, upper level flow, and shear vectors would favored discrete supercells and I bet the mountain range will fire some in Mexico. Could be a little later show down there and a gamble but very impressive environment and parameter space being modeled.

58da5cb8d10dd_delrio4.png.0912261bc8c54cf2e9ae6b2e69ff5e9d.png

58da5ca5c9721_delrio3.thumb.png.958fc4ea93c85078d99978380bfefc9d.png

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MOD risk issued for hail on 1300 OTLK

Quote

 ...Southern Great Plains...
   Rich gulf moisture characterized by mean mixing ratios to 14 g/kg
   per 12Z Del Rio, Corpus Christi, and Lake Charles RAOBs has become
   prevalent in the broadening warm sector over central/south TX. While
   diurnal mixing may yield pockets of lower dew points over
   central/east TX, a plume of lower to middle 60s surface dew points
   will be sustained along the dryline and warm front. Beneath a stout
   EML with very steep lapse rates to 9 degree C/km from 700-500 mb per
   12Z Del Rio RAOB, moderate to large buoyancy is expected ahead of
   the dryline. MLCAPE should reach 1500-3000 J/kg across the Edwards
   Plateau and Big Country. The leading edge of 50-kt 500-mb
   south-southwesterlies will spread east over this instability axis by
   late afternoon, yielding an environment favorable for supercells.

   While elevated storms will increase over the Texas Panhandle through
   midday, surface-based storms should develop towards mid-afternoon
   near the surface cyclone. Scattered storms will form farther south
   along the dryline late afternoon, with WAA-driven storms possible
   farther east over north-central TX. Initially discrete supercell
   mode should favor very large hail and localized severe wind gusts.
   Relatively high confidence in the coverage and location of storms
   warrants an upgrade to a hail-driven moderate risk from the Big
   Country into southwest OK. A few tornadic storms appear probable in
   this similar corridor. However, the temporal overlap of discrete
   cells with enlarging hodographs may be relatively short in the open
   warm sector. Low-level hodographs will be quite enlarged along the
   warm front, but should be coincident with modest low-level lapse
   rates and predominant cluster to linear mode. As such, an upgrade to
   15 percent tornado probabilities does not appeared warranted this
   outlook. 
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My play would be to sit along the warm front, probably somewhere along Childress to Wichita Falls corridor, and just hope a cell went tornadic as it went by. Fast storm motions plus messy storm mode means it will be very difficult to switch storm targets in any meaningful way.

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Two potential plays I'm considering today. Warm front around SPS and convection further west from Floydada to Childress. VBV looks to be an issue, but the HRRR seems to be backing off on how severe it looks. 14Z HRRR had two nice SUPs from NE of Lubbock toward Childress. Also of note and on the past several HRRR runs is a warm-front SUP that forms near SPS and eventually makes it up to Chickasha in the 23Z-02Z timeframe. 

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31 minutes ago, Zeromus-X said:

So let's say we didn't want to storm chase tornadoes today and didn't want to hit hailstorms, but we did want to get from Winslow Arizona to Indiana (by Friday). How far north is the risk of hitting this stuff effectively mitigated?

I-40 is under the gun from Amarillo to Oklahoma City through tonight (not much better with the southern I-20 route), so your best bet may be to leave after storms move east. After a break tomorrow morning, the I-44 corridor across the Ozarks will be in the line for severe storms late Wednesday, as well as the southern I-30 route. 

The northern route (after going north to Denver) doesn't look great either with heavy rainfall across much of Kansas through tomorrow. 

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