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4/7-4/10 possible severe WX

SouthATLwx

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Addison, TX
Pretty ominous AFD from FWD, 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.
 

SouthATLwx

Member
Joined
Dec 9, 2018
Messages
1,318
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Location
Addison, TX
Pretty ominous AFD from FWD, 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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ForsythSnow

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I was about to say I see this thing looking like a derecho ... those are unpredictable until they fully form ... usually come in faster as well
Any MCS type system is hard to model. Often direction and strength don't get modeled as well as them simply existing. They can last longer than modeled or shorter depending on each stage they go through. Only way to know how far/where it goes is to see on that day.
 

MRStorm

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I've learned a lot over the years on this Board, but one thing I haven't is, where on a Hodo does it tell you where it is for. That may be a stupid question but I have looked as closely as I can and can't. All I see is Long and Lat numbers but that doesn't help me. If it is not on there, when you post could you just briefly put where it is for. Thanks in advance.
 

EV_WS

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10 Mi. SW of Winston Salem. Home NE Davie County.
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