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cheese007

Severe Weather April 6th-10th 2021

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Probably going to go out and give tomorrow along the dryline/triple-point in Western KS. Low-level moisture has trended upward a bit in guidance, and all CAMs develop convection along the dryline between 22-00z. Tornado threat is likely fairly minimal due to lack of richer low-level moisture and lingering CINh, but severe weather is quite likely with any sustained, strong updraft given background environment. Would not be totally surprised if a supercell did *try* to produce something around sunset as low-level hodographs will likely be more than sufficient -- 3CAPE is definitely a bit lacking, though, and again the concern for lingering CINh.

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On Wednesday, it looks like several severe storms developing along the Mississippi River, with some favorable parameters for tornadoes. At this point, I don't really know if this could be a more serious tornado threat, or perhaps just a modest threat for wind/hail. The 12km NAM and 3km NAM have some significant tornado parameter values of 2 to 5 for northwest Mississippi or southeast Arkansas.

rmfwFVo.png

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While there are very clearly issues with today's setup (eg. lingering CINH and seasonally marginal moisture) 12z CAMs are really hammering the area INVOF the triple point in southwest/central KS this evening for potential isolated supercell development. IF this does actually happen, it could get pretty interesting if the storm were to become surface-based and lower its base a bit as SRH will be quite conducive for low-level mesocyclones.

uh25_024hmax_nh075.cp.f02400.png

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Looks like some potential exists through the end of the week. D3 slight for Friday witth a sig hatch for DFW, 15% contour in AL/FL/GA for D4. Oh and obviously today's enhanced risk

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Fairly large 10 percent tornado contour for today. Not the most impressive wind profiles but we can probably get numerous weak spin-ups in the warm sector. 

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2 hours ago, cheese007 said:

D3 slight for Friday witth a sig hatch for DFW

Been a bit since we had the last billion-dollar DFW hailstorm, no? :axe:

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   Mesoscale Discussion 0322
   NWS Storm Prediction Center Norman OK
   1110 AM CDT Wed Apr 07 2021

   Areas affected...Parts of eastern/northeastern Texas through western
   Arkansas

   Concerning...Severe potential...Watch likely 

   Valid 071610Z - 071815Z

   Probability of Watch Issuance...80 percent

   SUMMARY...The initiation of strong to severe thunderstorms appears
   possible as early 1-2 PM CDT.  This may, at least initially, include
   discrete supercells, before a squall line tends to evolve, and a
   risk for tornadoes, one or two of which could be strong.

   DISCUSSION...Cloud cover is slowing moist, warm sector
   boundary-layer destabilization, but it appears the air mass is
   already potentially moderately unstable as the significant upstream
   short wave trough begins to take on a neutral to negative tilt
   across the central Great Plains.  Downstream of the base of this
   troughing, beneath increasingly difluent mid/upper flow,
   considerable model output suggests that erosion of inhibition
   associated with capping elevated mixed-layer air, coupled with at
   least some further boundary-layer warming, will allow for the
   initiation of thunderstorm development as early as 18-19Z. 
   Initially this may be largely discrete, and scattered, but focused
   within a zone of enhanced low-level convergence along an eastward
   advancing cold front.

   With the environment becoming characterized by wind profiles with
   strong deep-layer shear and sizable, clockwise-curved low-level
   hodographs, in the presence of a deep moist boundary-layer, it
   appears conducive to supercells capable of producing tornadoes. 
   This includes potential for a strong tornado or two, though the
   overall tornado potential could be mitigated somewhat by relatively
   modest high-level flow and the tendency for upscale convective
   growth along the cold front through the afternoon.

   ..Kerr/Hart.. 04/07/2021

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

   ATTN...WFO...LZK...SHV...TSA...HGX...FWD...EWX...

image.png

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Now that we are getting into severe season, is anybody else annoyed that the SPC mesoanalysis shows a composite radar much more in the realm of light green than bright orange, for ongoing larger storms?

ffhWl0i.jpg

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6 minutes ago, MUWX said:

A special update to upgrade D3. Don’t see that often. 

"AN ENHANCED RISK WAS ADDED TO PORTIONS OF NORTHEAST LOUISIANA AND   CENTRAL AND SOUTHERN MISSISSIPPI. A SOUTHERN STREAM MID-LEVEL   SHORTWAVE TROUGH IS FORECAST TO AMPLIFY DURING THE EVENING HOURS ON   FRIDAY ACROSS EAST TEXAS AND LOUISIANA. IN RESPONSE, THE LOW-LEVEL   JET IS EXPECTED TO INCREASE DURING THE EVENING/EARLY OVERNIGHT HOURS   ACROSS LOUISIANA AND MISSISSIPPI. THIS STRENGTHENING LOW-LEVEL JET   SHOULD INCREASE THE THREAT FOR DAMAGING WINDS AND TORNADOES DURING   THE LATE OVERNIGHT FRIDAY AND EARLY MORNING HOURS SATURDAY ACROSS   MAINLY CENTRAL AND SOUTHERN MISSISSIPPI."

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12 minutes ago, cstrunk said:

Well today looks like an Enhanced Bust.

Yep, AR activity has mostly remained anemic and disorganized. Not enough heating/more capping than anticipated?

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So if Friday continues to trend in the wrong direction (hopefully not an early morning severe wx outbreak), is this going to be the main thread or is a new thread gonna be made in the SE subforum? 

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Possible tornado near Galion/Bonita, LA was earlier reported radar confirmed, although the latest warning statement downgrades to the standard "radar indicated rotation" it still shows as a TORR on GR Level 3.

Cell down near Fort Polk, although only severe-warned at the moment, is fairly robust, discrete and might have the best chance of anything yet today.

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1 hour ago, MattPetrulli said:

So if Friday continues to trend in the wrong direction (hopefully not an early morning severe wx outbreak), is this going to be the main thread or is a new thread gonna be made in the SE subforum? 

 

Well, it still seems like there could be substantial severe weather in OK/TX/AR/LA. So this would be the place for that in my opinion.

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11 minutes ago, MUWX said:

Storm of the day at 10:00. Not ideal 

Looks like a couple of abortive cycles now but this last one got real close to a significant :twister:near Mansura.

POE_0247.png

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SPC did model disco in the new Day 2... went with the Euro over NAM/GFS and even over the ARW ... but they explained why

That's a whale of an enhanced risk too :lol:

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Latest HRRR, NAM 3K NEST, and GFS don't seem to support the threat around DFW and southward. Mostly seems to develop a MCS in SE OK that bows southeast overnight.

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7 hours ago, stormdragonwx said:

Yeah scratching my head on this one. Maybe we will have more clarity later today.

https://www.spc.noaa.gov/products/outlook/day2otlk.html

day2otlk_0600.gif

There was apparently quite a bit of correspondence with the NWS branches for this outlook, according to FWD..

Pretty ominous AFD from them, although I'm still not seeing it in the cards for the Metroplex due to capping...

542
FXUS64 KFWD 081058
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
558 AM CDT Thu Apr 8 2021
...Significant Severe Weather Episode Expected Across Most Of
North Texas Into Eastern Central Texas Late Friday Afternoon Into
Friday Night...

As has been discussed in recent long term discussions the past
24-48 hours, it appears a fairly significant severe weather
episode is taking shape for specifically areas east of US-281 in
North Texas into our East Texas counties late Friday afternoon
into Friday night, specifically the evening hours. Large to very
large hail will be the primary concerns to go along with an
additional risk for localized damaging winds and possibly a brief
tornado across our far eastern counties. First the hail threat.
A surface low with a trailing surface dryline to the south will
move progressively southeast from NW TX and the Big Country into
the Eastern Hill Country and western Central TX by 00z Saturday
(or early evening Friday). This will be in response to mid level
height falls out in advance of a vigorous shortwave expected to
arrive Friday evening. In advance of this feature, the left-exit
region of a 110-120 knot upper jet maximum will be moving from
the Permian Basin and across SCentTX into SE TX.

Impressive low level warm advection from 35-45 low level flow
within the 925mb-850mb layer will help to transport moisture-rich
air from the TX Coast and nearshore waters north-northeast across
areas along and east of I-35 corridor as evidenced by surface dew
point temperatures in the mid-upper 60s. Throw in warm spring
temperatures well into the 80s across most areas east of the
approaching dryline and we`re staring at late day SB/MLCAPE values
in excess of 2000 J/KG to go along with VERY STEEP mid level
lapse rates between 8-9 deg C/km aloft. Kinematically, this
thermodynamic environment will correlate with westerly deep layer
shear on the order of 40-45 knots. After correspondence with SPC
it was agreed that the European model would be the preferred model
on trends with the surface low, cold front, and dryline (not as
far east and mixing out surface moisture as much as the GFS and
not exhibiting too cool of a bias east of the dryline, thus
keeping the area more capped with less convective initiation
and/or keep storms strictly "elevated"). South of the surface low
and behind the dryline late Friday afternoon, hot temperatures in
the lower-mid 90s will correlate with very dry air and breezy
west or northwest winds for an elevated wildfire threat south of
I-20 and especially along and west of US-281. If not for the
latest green up the past month, we`d be likely looking at higher
ERC-G values and a more critical wildfire threat.

As all these variables and parameters come together, the initially
strong capping inversion in the 850mb-700mb layer should lift,
moisten, and weaken across much of the area during the evening
rush hour for at least isolated to scattered storms to begin
developing from the DFW Metro north and east. With the impressive
free lift noted in the hail growth zone (-10 to -30 deg C), we
are staring at the prospects of seeing intense updrafts aloft with
hail similar to what was seen in both the Denton to Wylie and
Dallas/Van Alstyne hail events of the past decade when it comes to
hail size. Might as well throw in the early April event of 2003
as well as historical analogs from forecast point soundings of
several models show events that contained golfball to even
baseball or softball size hail. Considering the curved low level
profile through 850mb veering and lengthening above that, and a
weakening cap from mid afternoon through early evening, discrete
supercell tstorms will be possible. I believe the cap should hold
most areas during this time for hail to be the main threat and
impact, though storms will approach becoming surface-based by
early Friday evening ahead of an advancing cold front arriving
from OK into North-Central TX.

The best bet for damaging winds and perhaps a tornado will be
east of the DFW Metroplex and across areas east of Hwy 75 in the
north and along and east of I-45 in Central Texas. The one
mitigating factor for higher tornado threat will be relatively
weak and veering low level 0-1 km flow 5-15 knots, as the strong
low level 40 knot+ winds migrate east of our the area by evening.
This will shift the greater tornado and damaging wind threat
further east toward the Piney Woods/AR-LA-TX east into the Lower
MS Valley, which is the eastern half of the newly issued Enhanced
Risk from SPC across this region. As we enter the nighttime hours
post- sunset, the vigorous mid level shortwave will be tracking
toward the LA/TX border region and help draw the strong cold front
over OK southward into North Texas through midnight. Previous
discrete modes will transform more into a squall line (or linear
MCS if you prefer) to track south- southeast from east of US
287/I-35W in North TX through our far eastern counties from mid
evening into the early pre-dawn hours. At this time, I expect
primarily a damaging wind threat to go along with lower end severe
hail in the range of quarter to possible half dollar size with
updraft strength not being quite as intense due to interruption
from other storms along the line.
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