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DanLarsen34

April 18, 19, 2019 Severe Event

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Thought I’d get a thread going on this in the forum. We’ve got an enhanced risk across MS and AL today. 

 

Damaging winds appear to be the most significant threat within the ongoing QLCS. However, SPC has mentioned the potential for significant tornadoes too, both within the line and with any warm sector supercell development ahead of the line. 

SPC has 10% hatched tornado probabilities across the aforementioned states.

3F58C11E-FC18-483F-8B7E-AAAF10F707D4.gif

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8 minutes ago, DanLarsen34 said:

Thought I’d get a thread going on this in the forum. We’ve got an enhanced risk across MS and AL today. 

 

Damaging winds appear to be the most significant threat within the ongoing QLCS. However, SPC has mentioned the potential for significant tornadoes too, both within the line and with any warm sector supercell development ahead of the line. 

SPC has 10% hatched tornado probabilities across the aforementioned states.

3F58C11E-FC18-483F-8B7E-AAAF10F707D4.gif

Even with just a 10% chance, downdrafts and hail are going to be a major problem and combined with heavy flooding, it will be a mess

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Keep an eye on the convection out ahead of the main line. Definitely some cellular looking activity already popping up. This cell west of Baton Rouge looks promising. 

78847CBF-C9C1-44FC-8397-FE20AAF1F9E0.png

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High UH track across the MS/AL border on the latest HRRR lines up nicely with what appears to be a boundary on visible sat (look at the bubbling cumulus to the south vs waves to the north) - was a similar example earlier on the LA/MS border that's now cloud-obscured, my post in the Central/Western forum thread for this event has the images for that one.

uh25_max.us_se.png

COD-GOES-East-meso-meso2.truecolor.20190418.161456-over=map-bars=.gif

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Looks like the low has trended further south in the last few HRRR runs - now centred over southern rather than northern MS by 00Z.

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Frankly I'm shocked SPC would use UH tracks as a tie breaker, but the text is right there. That said, I like punting MDT today.

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Quite frankly, the SPC wording isn’t all that doomsday like. They mention a few tornadoes with an enhanced wind threat. It looks like today is the worst of this 3 day outbreak.

 

 

.

 

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NWS SPCVerified account @NWSSPC 5m5 minutes ago

 

4/18 12:50 PM CDT: Looking ahead to the severe risk for tomorrow: Severe thunderstorms are expected from parts of Florida into the Mid-Atlantic on Friday with scattered damaging winds and a few tornadoes possible. #flwx #gawx #scwx #ncwx #vawx #mdwxD4dBUQ6XsAI4sH0.jpg

 

 ...Northern FL...Eastern GA...Carolinas...VA...
   A line of storms, possibly severe, will be ongoing Friday morning
   across central GA into the Florida Panhandle along the cold front.
   Strong winds veering with height will favor supercells embedded
   within the line producing damaging wind or tornadoes with dewpoints
   in the 68-70 F range. This line will likely remain severe into
   southeast GA into early afternoon, with a gradual decrease in threat
   with southward extent into FL. 

   Heating will occur ahead of the frontal line, leading to an axis of
   1000-1500 J/kg MLCAPE from FL to southern VA. Given the track of the
   upper low, there will not be much cooling aloft ahead of the cold
   front, leading to less favorable lapse rates aloft and marginal
   instability. Still, sufficient levels of instability will be
   attained given very strong southerly deep-layer mean winds and
   low-level shear to support supercells within the line. Swaths of
   damaging wind and a few tornadoes are expected as storms move
   rapidly northeastward during the day, mainly from GA into VA. 

   More isolated severe activity is expected across WV and PA, where
   wind profiles will also be strong but instability weak. However,
   daytime heating and steepening of low-level lapse rates may support
   at least shallow severe storms, perhaps a supercell.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   5%     - Slight
   Wind:     30%     - Enhanced
   Hail:     15%     - Slight
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Just now, ryan1234 said:


Quite frankly, the SPC wording isn’t all that doomsday like. They mention a few tornadoes with an enhanced wind threat. It looks like today worst of this 3 day outbreak.


.here in danville, the winds alone would cause a huge issue with how wet its been for the last 6 months. add in flooding potential and we are in it big time. we still have areas from michael that are nowhere near repaired and ,the runoffs would cause big issues. Just around our neighborhood we have street still missing chunks and drainage culverts and creeks not repaired to where they were before michael came thru. the last two bouts of rain have even caused local mudslides and power outages...it wont take much up here.

 

 

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19 minutes ago, nrgjeff said:

Frankly I'm shocked SPC would use UH tracks as a tie breaker, but the text is right there. That said, I like punting MDT today.

Especially when the HRRR has been showing some decent UH tracks today - guess the other HREF members didn’t agree.

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   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
   FLORIDA INTO THE MID ATLANTIC...

   ...SUMMARY...
   Severe thunderstorms are expected from the Florida into the
   Mid-Atlantic on Friday with damaging winds and a few tornadoes
   possible.

   ...Synopsis...
   An upper low will deepen as it pivots northeast out of MS/AL across
   eastern TN/KY, with a leading midlevel speed max in excess of 100
   kt. Meanwhile a cold front will strengthen and surge eastward across
   GA and the western Carolinas during the afternoon while 60s F
   dewpoints are maintained to the east. Shear profiles will be strong,
   with 50+ kt southerly 850 mb winds aiding potential damaging winds
   or tornadoes throughout the day.

   ...Northern FL...Eastern GA...Carolinas...VA...
   A line of storms, possibly severe, will be ongoing Friday morning
   across central GA into the Florida Panhandle along the cold front.
   Strong winds veering with height will favor supercells embedded
   within the line producing damaging wind or tornadoes with dewpoints
   in the 68-70 F range. This line will likely remain severe into
   southeast GA into early afternoon, with a gradual decrease in threat
   with southward extent into FL. 

   Heating will occur ahead of the frontal line, leading to an axis of
   1000-1500 J/kg MLCAPE from FL to southern VA. Given the track of the
   upper low, there will not be much cooling aloft ahead of the cold
   front, leading to less favorable lapse rates aloft and marginal
   instability. Still, sufficient levels of instability will be
   attained given very strong southerly deep-layer mean winds and
   low-level shear to support supercells within the line. Swaths of
   damaging wind and a few tornadoes are expected as storms move
   rapidly northeastward during the day, mainly from GA into VA. 

 

 

 

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Just now, Jackstraw said:

Yeah nws in Jackson is sheltering in place

totally unrelated to this post but....

 

tomorrow in southside va, we will be playing "oh the dreadful wind and the rain" and singing " if the thunder dont get ya, then the lightning will..."

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day2otlk_1730.gif?1555623749715A

A Severe line of storms is forecast to come through NC/SC/FL/GA Friday. Some of them could produce a few tornadoes. East of I-77 I am seeing increasing helicity values in SE NC. A few supercells may form along the line. I really want to see a tornado this time.

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All the regional forecast offices have pretty much the same wording, other than the timing of the showers/storms.

In addition to the aforementioned pre-frontal QLCS likely to be 
ongoing over the srn Appalachians, a plume of WAA-driven convection 
streaming nwd from the Gulf Stream Atlantic will likely also be 
ongoing over the NC Sandhills/Coastal Plain vicinity Fri morning. 
Destabilization via advective processes may offset a lack of early 
day diabatic heating owing to widespread low overcast, which may 
contribute to the realization of around 1000 J/kg of MLCAPE there 
through 15Z. Already strong, and strengthening deep layer flow would 
favor some organization with this even early day activity, including 
some rotating updrafts and risk of a brief/weak spin up. 

There may then be a brief lull in that morning activity that will 
subsequently continue newd and out of cntl NC, followed by scattered 
cellular development over the Piedmont, immediately ahead of what 
will likely be a strengthening QLCS from the early day convection 
initially over the srn Appalachians. All severe hazards would 
accompany any such scattered, discrete cells ahead of the QLCS, in 
an environment characterized by strengthening environmental shear/ 
lengthening hodographs, aided by both the strengthening wind fields 
aloft and increasingly backed surface flow in the warm sector. The 
QLCS will then pose a risk of widespread 35-50 kt winds, locally up 
to 60-65 kts, and a few mesovortices/tornadoes. Additionally, 
forecast environmental parameters suggest the potential for a 
significant tornado.  

Precipitable water values are forecast to be near 1.7" - around a 
monthly record high and 3-4 SD above climo. So while basin average 
rainfall amounts of one to two inches are anticipated, the unusually 
high PWAT values and related IVT courtesy of both that excessive 
moisture and a similarly anomalous LLJ, will favor convective 
rainfall rates, and amounts in especially urban areas, that may near-
exceed 1-2 FFG values over at least the NC Piedmont. A short-fused 
FFA may consequently be needed, though it was the collective 
decision by adjacent offices to hold off on issuance at this time. 

Lastly, warm sector winds may reach Advisory criteria outside of 
convection, but since this appears to be similar to most of our WAA 
wind regimes in that it will be sensitive to diabatic and mesoscale 
influences (clouds/early day convection), such issuance will 
similarly be passed to subsequent shifts as those details emerge.
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The Eastern part of NC could see 2 rounds of storms tomorrow.

HWO -

An isolated strong to severe thunderstorm will be possible Friday
morning through early afternoon, mainly between 10 AM and 1 PM. A
greater risk for severe thunderstorms will exists between 3 PM and 
10 PM. The main severe weather hazards will be damaging straight-line
winds, large hail, torrential downpours, and a few tornadoes. 
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From BMX

Concern is growing for areas along and south of Interstate 85 from
Montgomery to the AL/GA state line. This is where SBCAPE values 
have the best chance of reaching the 1000-1400 J/kg range before 
storms arrive. If this amount of instability is realized, 
effective storm relative helicity values of 400-500 m2/s2 will 
support a potential for strong tornadoes (EF2 intensity). 0-6 km 
shear vectors are supportive of a mixed mode of supercells and 
bowing line segments as the event unfolds overnight. Due to low 
confidence, we will refrain from messaging the potential for 
strong tornadoes in our products at this time and continue to 
monitor mesoscale trends. 
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Will be fun :

 

from NWS

Batten down the hatches! Appears the line of strong to severe storms is moving faster than expected into western GA. Could arrive into Polk, Haralson, Carroll and Heard Counties shortly after 10 PM. Be prepared for damaging winds, very heavy rain and frequent lightning.

 

 
   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 85
   NWS Storm Prediction Center Norman OK
   820 PM EDT Thu Apr 18 2019

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Eastern Alabama
     Western Georgia

   * Effective this Thursday night and Friday morning from 820 PM
     until 300 AM EDT.

   * Primary threats include...
     Scattered damaging wind gusts to 70 mph likely
     Isolated large hail events to 1 inch in diameter possible
     A tornado or two possible

   SUMMARY...A line of intense showers and thunderstorms will track
   eastward across the watch area this evening, posing a risk of
   locally damaging wind gusts.

   The severe thunderstorm watch area is approximately along and 60
   statute miles east and west of a line from 45 miles east northeast
   of Huntsville AL to 50 miles south southeast of Columbus GA. For a
   complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU5).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Severe Thunderstorm Watch means conditions are
   favorable for severe thunderstorms in and close to the watch area.
   Persons in these areas should be on the lookout for threatening
   weather conditions and listen for later statements and possible
   warnings. Severe thunderstorms can and occasionally do produce
   tornadoes.

   &&

   OTHER WATCH INFORMATION...CONTINUE...WW 83...WW 84...

  

FB97B639-5B68-4209-80B3-E20122CDBB60.gif

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Probabilities 

:  Click for Complete Product Text
Tornadoes

Probability of 2 or more tornadoes 

Low (20%)

Probability of 1 or more strong (EF2-EF5) tornadoes

Low (5%)

Wind

Probability of 10 or more severe wind events

Mod (60%)

Probability of 1 or more wind events > 65 knots

Low (20%)

Hail

Probability of 10 or more severe hail events

Low (20%)

Probability of 1 or more hailstones > 2 inches

Low (10%)

Combined Severe Hail/Wind

Probability of 6 or more combined severe hail/wind events

High (80%)

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