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Severe Weather for 4/19-4/23

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3 minutes ago, janetjanet998 said:

URGENT - IMMEDIATE BROADCAST REQUESTED  
TORNADO WATCH NUMBER 133  
NWS STORM PREDICTION CENTER NORMAN OK  
1055 AM CDT WED APR 22 2020  
  
THE NWS STORM PREDICTION CENTER HAS ISSUED A  
  
* TORNADO WATCH FOR PORTIONS OF   
  WESTERN LOUISIANA  
  EAST TEXAS  
  
* EFFECTIVE THIS WEDNESDAY MORNING AND AFTERNOON FROM 1055 AM  
  UNTIL 500 PM CDT.  
  
* PRIMARY THREATS INCLUDE...  
  A FEW TORNADOES LIKELY WITH A COUPLE INTENSE TORNADOES POSSIBLE  
  WIDESPREAD LARGE HAIL AND ISOLATED VERY LARGE HAIL EVENTS TO 2  
    INCHES IN DIAMETER LIKELY  
  SCATTERED DAMAGING WIND GUSTS TO 70 MPH LIKELY  
  
SUMMARY...THUNDERSTORMS ARE EXPECTED TO INTENSIFY AND SPREAD  
EASTWARD ACROSS THE WATCH AREA THROUGH THE DAY, WITH A FEW SEVERE  
STORMS LIKELY.  THE STRONGEST CELLS WILL POSE A RISK OF LARGE HAIL,  
DAMAGING WINDS, AND A FEW TORNADOES.  

Watch is already up

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26 minutes ago, TexMexWx said:

Question: If these storms do form in SE TX, would that limit the moisture/instability that can go up towards DFW and southern OK?

There are already dewpoints in the mid-to-upper 60s on the northwestern side of where these storms are expected to form.  I doubt they will have that much of an effect for later on, although I guess sinking air could suppress storm development behind them (Steve McCauley was referring to this possibility if morning storms formed over DFW, which has not happened).

We will probably get a separate watch later on.

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1 minute ago, BrandonC_TX said:

There are already dewpoints on the northwestern side of where these storms are expected to form.  I doubt they will have that much of an effect for later on

Okay, that makes sense.

2 minutes ago, BrandonC_TX said:

although I guess sinking air could suppress storm development behind them (Steve McCauley was referring to this possibility if morning storms formed over DFW, which has not happened).

Yeah, no storms so far but I think there were some showers extending from SW to NE across parts of Dallas county. May not have that much of an effect for later on though. Guess we'll keep waiting for how it unfolds. I really don't think I want any big storms coming through these populated areas.

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5 minutes ago, TexMexWx said:

Okay, that makes sense.

I meant to say dewpoints in the mid-to-upper 60s and edited my post accordingly.  A couple spots in central Texas (behind that area of developing storms) are reporting dewpoints around 70.  Provided that convective initiation occurs, I do not think storms will have any trouble turning severe with up to 4,000 J/kg of MLCAPE and 5,000 J/kg of SBCAPE modeled (although these high CAPE values are dependent on dews in the lower 70s).  A major hailstorm near or over DFW is a definite possibility this afternoon, and potentially a tornado or two (perhaps strong) as well.  Hopefully this does not happen.  There should be lower helicity along the dryline (compared to areas to the east) but there will be much higher CAPE.

I'm still socked in with clouds here in west Fort Worth at the current moment, but there does seem to be an area of clearing to the west just ahead of the dryline (precisely where the higher CAPE currently is).  As this area of clearing moves east I fully expect things to destabilize in DFW pretty quickly.  SPC Mesoanalysis forecast data (from the RAP) has the clearing arriving in DFW within the next two hours.

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A ~1430Z sounding from CLL has a strong cap with garbage low level lapse rates and rising theta-e wrt height in the boundary layer. Might be a little tough for storms in SETX to become surface based.

 

 

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14 minutes ago, 1900hurricane said:

A ~1430Z sounding from CLL has a strong cap with garbage low level lapse rates and rising theta-e wrt height in the boundary layer. Might be a little tough for storms in SETX to become surface based.

 

 

yep,

and you can see the stable wave clouds on Fort Hood radar like you  would usually on the visible

Plus they are training over each other, self defeating for any surface heating

 

got to move more east..

 

 

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No changes were made to the outlook graphic.

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   SOUTHEAST OKLAHOMA...NORTHEAST TEXAS...SOUTHERN ARKANSAS...AND
   NORTHERN LOUISIANA...

   ...SUMMARY...
   The greatest severe-weather threat extends from parts of
   central/eastern Oklahoma to north-central/east Texas, to the lower
   Mississippi Valley. Tornadoes, severe hail and damaging gusts are
   all possible.

   No changes have been made to the ongoing outlook areas.

   ...East TX into LA today...
   Scattered thunderstorms have begun to form in central TX beneath the
   sub-tropical jet.  A very moist boundary layer beneath steep lapse
   rates will provide ample CAPE for hail this afternoon in the
   strongest cells.  Considerable shear and helicity also pose an
   increasing risk of a few tornadoes this afternoon as storms spread
   into LA. Refer to MCD #436 for further details.

   ...Eastern OK/Western AR early this afternoon...
   Scattered strong to severe storms have been occurring over eastern
   OK this morning, in a region of strengthening low-level warm
   advection and lift ahead of an approaching shortwave trough.  The
   strong cells/clusters may continue to pose a risk of large hail
   through the early afternoon as they move into western AR and slowly
   weaken.  

   ...Central OK into North TX this afternoon/evening...
   A well-defined dryline is expected to develop this afternoon over
   southwest OK and western north TX - mixing eastward to roughly I-35
   by 22z.  Very steep lapse rates and dewpoints at least in the mid
   60s will yield a corridor of strong MCAPE with values over 3500 J/kg
   and little inhibition.  This will likely result in the development
   of a few supercells roughly between OKC and FTW.  Very large hail
   will be possible with this activity, as well as a few tornadoes
   (including strong tornadoes).  These supercells will likely persist
   into the evening and track across southeast OK and northeast TX.

   ...ArkLaTex overnight...
   Storms will likely congeal in the late evening over northeast TX and
   surge eastward overnight across parts of AR/LA and eventually into
   MS.  These storms will have an increasing risk of damaging winds,
   along with continued threats of hail and tornadoes.

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5 minutes ago, janetjanet998 said:

yep,

and you can see the stable wave clouds on Fort Hood radar like you  would usually on the visible

Plus they are training over each other, self defeating for any surface heating

 

got to move more east..

Yeah SE TX might not be doing much, for the time being at least, with the current obs + evolution and movement of convection

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Really like today's setup south of I-40 in OK. Likely a couple of outflow boundaries to interact with for storms coming off the dryline, plus winds (as of now) are remaining more backed than in model guidance. Residual capping may also encourage rather photogenic storm structure in addition to the tornado threat.

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Helicity doesn't look to be super high across north-central Texas, as was mentioned before, but the HRRR has been showing storms forming just west or maybe IN western parts of the DFW metro and tracking east over a still decent environment for the past few runs.

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Just now, TexMexWx said:

Helicity doesn't look to be very high across north-central Texas, as was mentioned before, but the HRRR has been showing storms forming just west or maybe IN western parts of the DFW metro and tracking east over a still decent environment for the past few runs.

well, i guess a positive outcome from this COVID thing is that a hail storm would potentially cause less damages across DFW now given there're much less business activities overall...

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Just now, vwgrrc said:

well, i guess a positive outcome from this COVID thing is that a hail storm would potentially cause less damages across DFW now given there're much less business activities overall...

Yeah... I would hope less cars are outside in general as well.

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12 minutes ago, TexMexWx said:

Helicity doesn't look to be super high across north-central Texas, as was mentioned before, but the HRRR has been showing storms forming just west or maybe IN western parts of the DFW metro and tracking east over a still decent environment for the past few runs.

The CAPE values should be quite high whenever storms do develop.  100-200 m2/s2 of SRH (that model is saying roughly the same for 0-1km and 0-3km SRH) should be sufficient for potentially tornadic storms with the high CAPE present.

 

7 minutes ago, vwgrrc said:

well, i guess a positive outcome from this COVID thing is that a hail storm would potentially cause less damages across DFW now given there're much less business activities overall...

Not necessarily.  People still have homes and are occupying them.  Not everyone has a garage (or sufficient space) to place all of their cars inside or under cover.  Unoccupied businesses still have value. A big hailstorm over DFW will be an insurance nightmare no matter where it hits in the metro.  There will be fewer people outside who could get injured (which is the bright side here), but insofar as monetary damages are concerned there would be little difference in my opinion.

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Outflow boundary setting up near norman and sagging southward a bit. could modify over the next hour or two and make things get real interesting around the Katie-Norman area.

Theoretical target: Pauls Valley

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4 minutes ago, BrandonC_TX said:

The CAPE values should be quite high whenever storms do develop.  100-200 m2/s2 of SRH (that model is saying roughly the same for 0-1km and 0-3km SRH) should be sufficient for potentially tornadic storms with the high CAPE present.

Oh yes, I definitely agree that with the CAPE present, storms wouldn't need very high amounts of helicity to intensify. In addition, when I said that, I had been looking more at the hodograph and was eyeballing, but afterwards I saw the values themselves which were showing possibly even upwards of 200 m2/s2 of SRH as well. Now I'm getting a little more concerned..

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2 minutes ago, Indystorm said:

Nice clearing rapidly moving in from the west on satellite.

Just had a downpour IMBY in Longview, TX. Now I have sunshine. If this line in E/SE TX can push east we should see more clearing...

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Still socked in with clouds in west Fort Worth, but the skies seem a little brighter compared to an hour ago.  Temperatures have warmed into the lower 70s as well.

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struggling SE TX storms

ESOSCALE DISCUSSION 0438  
NWS STORM PREDICTION CENTER NORMAN OK  
0110 PM CDT WED APR 22 2020  
  
AREAS AFFECTED...CENTRAL/EASTERN TEXAS AND WESTERN LOUISIANA  
  
CONCERNING...TORNADO WATCH 133...  
  
VALID 221810Z - 221915Z  
  
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 133 CONTINUES.  
  
SUMMARY...THE SEVERE THREAT CONTINUES ACROSS WW 133.  
  
DISCUSSION...LATEST CONVECTIVE TRENDS INDICATE THAT STORMS ARE  
STRUGGLING TO SUSTAIN PERSISTENT SEVERE INTENSITY SO FAR, WITH ONLY  
OCCASIONAL 1-1.5" HAIL REPORTS BENEATH THE STRONGEST CORES.  STEEP  
MID-LEVEL LAPSE RATES AND APPRECIABLE CLOUD-BEARING SHEAR WILL  
MAINTAIN THIS THREAT, THOUGH BASED ON POINT FORECAST SOUNDINGS IT  
APPEARS THAT MOST STORMS ARE ELEVATED ABOVE A RELATIVELY STABLE  
BOUNDARY LAYER AND UNABLE TO INGEST LOW-LEVEL SHEAR/VORTICITY NEEDED  
FOR MESOCYCLOGENESIS.  
  
THE THREAT FOR ISOLATED LARGE HAIL SHOULD CONTINUE THROUGHOUT THE  
DURATION OF THE WATCH, AND ANY RISK OF TORNADOES OR DAMAGING WIND  
GUSTS WILL LIKELY BE TIED TO ANY SURFACE-BASED CONVECTION THAT CAN  
ORGANIZE.  THE MOST LIKELY AREA FOR THIS CONDITIONAL THREAT WILL  
EXIST IN THE EASTERN HALF OF THE WATCH FROM THE LUFKIN VICINITY INTO  
WEST-CENTRAL LOUISIANA OVER THE NEXT FEW HOURS.  

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Mesoscale Discussion 0439
   NWS Storm Prediction Center Norman OK
   0112 PM CDT Wed Apr 22 2020

   Areas affected...Southern Oklahoma through north Central Texas

   Concerning...Severe potential...Tornado Watch likely 

   Valid 221812Z - 221915Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Severe storms expected to develop from southwest Oklahoma
   into northwest TX and spread east this afternoon into the early
   evening. A tornado watch will likely be needed soon. Very large
   hail, damaging wind and a few tornadoes are all possible.

   DISCUSSION...Early this afternoon a dryline extends from a surface
   low southward into northwest TX. A quasi-stationary front extends
   eastward from the low through southern OK. The boundary layer is
   destabilizing in dry slot region across northwest TX into
   southwestern OK where some clearing, steep lapse rates, and
   dewpoints in the upper 60s have contributed to 2000-2500 J/kg
   MLCAPE. Storms are in the process of developing near triple point
   across southwestern OK, and additional isolated storms are expected
   to develop farther south into northwest TX along sharpening dryline.
   Though low level winds are in the process of veering near the
   initiation zone, storms may encounter more favorable 0-1 km storm
   relative helicity for low-level mesocyclones as they move east
   through the warm sector. Strong (50+ kt) effective bulk shear will
   support supercells capable of very large hail, damaging wind and a
   few tornadoes.

   ..Dial/Hart.. 04/22/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...SHV...TSA...FWD...OUN...

   LAT...LON   33489825 34749837 34789661 34099516 32779537 32289793
               33489825 

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Convective initiation has now started in southwestern Oklahoma, west of Lawton.

And the brightening skies trend continues in west Fort Worth; I am now getting filtered sunshine on and off.  I'm assuming that the sunshine is filtered due to high-level clouds visible on satellite imagery.   SPC now says that a tornado watch is likely for N TX into S OK (see MD text in prior post).

EDIT: filtered sunshine became more consistent within the last few minutes.  I can now see blue skies off to the northwest; the clearing is now starting to affect the western portions of the DFW area.

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Disclaimer: a Still expecting a couple of intense supercells on either side of the Red River...

Cloudiness is socked in near and east of I-35. The HRRR has been trending somewhat narrower and a tick SW with the narrow warm sector for this afternoon. The best low-level shear is where there is dense cloud cover, while the cap is eroding farther west. An outflow boundary south of Norman is drifting south, which should keep the OKC metro area away from any intense storms.

With that said, seasonably rich boundary layer moisture (dews of 68-71F) has advected to about the Red River with a narrow tongue of strong instability. Deep layer wind profiles are favorable and low-level winds are backed to SSE along the I-35 corridor.

Two areas to watch:

1. Near the surface low/triple point. Concern here is a semi-discrete or clustered storm mode, but as @andyhb mentioned, they’re on target to approach multiple outflow boundaries, so there should be a notable tornado threat. Residence time for something photogenic may be tempered a bit due to storm modes and the narrow width of the warm sector, but we’ll see. 

2. An intense supercell or two will likely develop near or just north of DFW. Here, there will be large buoyancy and likelihood that the cap will break by 21-22z. I’d suspect large to very large hail will be likely here. Although low-level shear may be modestly less impressive, it will still be favorable for tornadoes.

You could still get a storm between these two areas, but if I had to narrow it down to two targets, there you go. 

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1 minute ago, 1900hurricane said:

Sharpening dryline is becoming evident in N TX with surface obs, rader, and visible imagery.

Definitely some agitated cumulus visible in the satellite imagery extending south of Wichita Falls.  If that extends under those high clouds (which it likely does) then this will be the area to watch for storm initiation that may affect the DFW Metroplex.

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Storm near altus is already going to town. Storm directly to the south of it looks to be weakening. If it can latch on to the OFB south of OKC, it could be game on. 

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SVR Warned Cell north of Altus has the 'Flying Eagle' look that always seems to show up with isolated TOR cells. Will be interested in seeing how it evolves.

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Lawton to Paul's Valley is the zone to watch ahead of that storm near the boundary. Boundary appears to still be edging southward, and does not appear to be much potential for modification on the north side of the boundary with clouds socked in. If storms cross the boundary the tornado threat is probably very low. 

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