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Severe WX Severe Weather threat for 7/19-7/22/18

Do you think a moderate risk will come out of this threat?

  • Yes

    Votes: 10 45.5%

  • No

    Votes: 5 22.7%

  • An enhanced risk, but not a moderate

    Votes: 6 27.3%

  • It should be a high risk for the wind threat

    Votes: 1 4.5%
  • Total voters
    22
  • Poll closed .
MichelleH said:
Thank you for sharing that. That is an event I was not aware of, even after living here in North Alabama all of my life.
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The boat was owned by the CEO of SCI, Olin King. It was named the SCITanic.
 
Completely missed today, wasn't expecting anything like this out of it. Horrible news from Arkansas :(
My guesstimate for the Marshalltown, IA tornado is the official rating will be EF3, maximum intensity was probably EF4.
 
nam4km.uh25_max.us_ov.trend.gif
 
I don't like being that close to the apex of a derecho; gonna have to be glued to the radar tomorrow evening.

Man the 00z 3km NAM goes bonkers, it's one of the most intriguing model runs I've seen for these parts especially at this time of year. Fires a few discrete storms in MS tomorrow evening, brings the powerful MCS overhead from the north after midnight, then a second MCS from the NW near sunrise, then after a rapid airmass recovery, two waves of discrete cells that organize into a southward bursting MCS by Saturday evening/night. Things will change from that obviously, but wow what a setup for July.
 
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Equus said:
I don't like being that close to the apex of a derecho; gonna have to be glued to the radar tomorrow evening.
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North AL and MS is in trouble. Central AL and MS still need to watch this closely as an MCS is hard to forecast dissipation. All CAMs show a probable very intense Derecho.

Interesting enough, both NAM and GFS want to fire a cluster of nocturnal supercells over east AL and GA late Saturday.
 
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Great forecast discussion.

000
FXUS64 KBMX 192359
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
659 PM CDT Thu Jul 19 2018

.DISCUSSION...
Updated for severe weather threats on Friday night and Saturday.

An upper-level trough over the Great Lakes an attendant swath of
northwesterly 40-60kt 500mb flow will have an unusual impact (for
July) on our forecast area Friday night and Saturday. A synoptic
cold front located near the Ohio River should be the focus for
explosive thunderstorm development late Friday afternoon. This
activity should grow upscale in the presence of SBCAPE values of
4000-6000 J/kg and move southward into TN during the evening. It
appears that relatively lower amounts of boundary layer moisture
will be present over much of Alabama on Friday afternoon due to
low-level diffluence. This should begin to change during the
evening as the surface to 850mb wind fields respond to the
approaching upper-level jet streak. A mesolow associated with the
MCS may also enhance moisture transport especially across West
Alabama, leading to SBCAPE values of 3000-4000 J/kg as the MCS
arrives. This amount of instability combined with 500mb flow of
35-45kt should help maintain an enhanced damaging wind into the
northwestern part of the CWA, and possibly all the way to our
southern border through early Saturday morning. The damaging wind
threat may diminish with eastward extent due to lower CAPE values.

Another round of severe storms is possible on Saturday if the
airmass recovers. This will depend on the strength and placement
of the cold pool resulting from the MCS Friday night into Saturday
morning. Models suggest low-level westerly flow will become
established Saturday afternoon as 50-55kt northwesterly 500mb flow
overspreads this area. This may result in quality moisture
advection and SBCAPE values of 3500-4500 J/kg. Weak surface
convergence and boundaries leftover from prior convection could
serve to spark isolated to scattered supercell thunderstorm
development Saturday afternoon and evening. In addition to
damaging winds and quarter size hail, strongly veering surface to
700mb flow would support some tornado risk as well. The overall
setup is highly conditional, and forecast confidence is low at
this time.

87/Grantham
 
Moderate Risk for hail S IN, W KY, NW TN; wind probs at 30% (Enhanced) pulled further south into much of N AL. Also a Day Two Slight for much of east central AL. Possibility that tor probs in the MDT get bumped to 10% depending on mesoscale trends according to SPC. I would not be shocked to see a 45% hatched wind later if the derecho trend holds.

day1otlk_20180720_1200_prt.gif
 
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Equus said:
Moderate Risk for hail S IN, W KY, NW TN; wind probs at 30% (Enhanced) pulled further south into much of N AL. Also a Day Two Slight for much of east central AL. Possibility that tor probs in the MDT get bumped to 10% depending on mesoscale trends according to SPC. I would not be shocked to see a 45% hatched wind later if the derecho trend holds.

day1otlk_20180720_1200_prt.gif
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If the Derecho trend holds with the instability at what it is, they may need a High risk area.
 
Yeah. I've been just staring at model data for hours now being amazed at the CAPE values projected ahead of whatever develops. Never good news to get these shear profiles on days with such explosive instability.
 
FI6csKz.jpg


Pretty solid MLCAPE & wind shear. Especially around Memphis.
 
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