April 5-6 Severe Threat

[a5ehren]

26 minutes ago, kayman said:

I agree.  FFC seems to always take things too lightly and doesn't handle forecasting severe weather well at all.  I'm going to be monitoring what BMX, HUN, and James Spann take on the things as this system moves towards West and North Georgia.  I hope Metro Atlantans do not lull themselves into the false belief of never seeing a tornado because the conditions misses the area so often.

FFC's discussion seems perfectly reasonable for areas north of the Fall Line based on recent model performance:

Quote

Strong to severe thunderstorms are expected with the developing
convection overnight and Wednesday. Scattered showers and
thunderstorms will develop along and ahead of the northward moving
warm front overnight, becoming more widespread by daybreak. A brief
break in convective activity south of the warm front is possible,
but storms should fill back in as the cold front nears. This weather
system has the potential to be stronger than Monday`s system...with
the tornado and damaging wind threats a bit higher.

Wednesday`s system will be aided by much stronger dynamics aloft and
more shear. The only parameter to watch would be available moisture.
The airmass south of the warm front will be much more moist with
dewpoints well into the middle 60s and lower 70s. Model soundings
show that PWATS rapidly increase during the afternoon to near an
inch and a half from values below half and inch today. See no reason
why the warm front would get stuck across south GA, as the 15-20kt
BL winds will be sufficient to give it the push northward that it
needs. The only question will be how far the warm front makes it
northward during the day on Wednesday morning. With the warm front
moving north overnight, a non-diurnal trend was needed mainly along
and south of the Interstate 20 corridor.

As stated before, damaging wind gusts will be the primary mode of
severe weather. However, the potential for tornadoes will be higher
than with Monday`s system. Some large hail is also possible, with
moderately steep lapse rates. Also think that the potential for
localized flooding is a bit higher than with Monday`s system. The
CWFA received anywhere from a half an inch of rain to one and a half
inches of rain on Monday. Wednesday`s system does have the potential
for areas to receive more than one bout of rainfall - once with the
warm front and another round with the cold front. Not too confident
right now to pinpoint axis of heavier rainfall, but will continue to
monitor the situation.

 

[a5ehren]

2 minutes ago, NorthArlington101 said:

Sneaky 10% tor today in your subforum. Very small area highlighted in the MS enhanced risk. 

I'm not sure we actually have any south MS posters here, even if it is technically part of this forum's area. 

[LithiaWx]

3 hours ago, gman said:

Let's hope it does bust. Lives were lost yesterday. We don't severe weather that will take more lives. 

I pull for severe.  It doesn't matter how much I want it to happen.  The weather is going to do what's it's going to do no matter what I think. 

 

I just hope it's close enough to witness it.  If you are aware the chances of you getting hurt go way down.  Stay frosty. 

[NorthArlington101]

21 minutes ago, NorthArlington101 said:

Sneaky 10% tor today in your subforum. Very small area highlighted in the MS enhanced risk. 

Aaaaaand its gone. Dropped to a 5% and a slight.

[Steven_1974]

10 hours ago, LithiaWx said:

hopefully this one doesn't bust as bad as today did.

I hope it busts even more so than yesterday. We don't need death and destruction.

[Santa Clause]

Not going to stink up this thread, but the insinuations severe weather buffs love death and destruction can take a hike. All weather in extreme forms cause unwanted outcomes. Even the beloved flakes.

[frazdaddy]

8 minutes ago, Wmsptwx said:

Not going to stink up this thread, but the insinuations severe weather buffs love death and destruction can take a hike. All weather I'm extreme forms cause unwanted outcomes. Even the beloved flakes.

Well said, this is a WEATHER FORUM.

[a5ehren]

1 minute ago, frazdaddy said:

Well said, this is a WEATHER FORUM.

It's also a debate that we've had about 5 million times.

[Solak]

RAH HWO

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

A strong storm system may bring multiple rounds of strong to severe
thunderstorms to central NC late Wednesday afternoon through early
Thursday. All severe weather hazards, including damaging straight
line winds, isolated tornadoes, and large hail will be possible.

Windy conditions will develop behind a strong cold front that will
cross the region early Thursday. Southwesterly wind gusts between 35
and 45 mph are expected throughout the day.

 

 

[frazdaddy]

1 minute ago, a5ehren said:

It's also a debate that we've had about 5 million times.

Sadly true. Que Mr. Burns.

[Cold Rain]

If you hate severe weather, all you need to do is move inside the blue area for the season, and you'll be adequately protected.

[audioguy3107]

Another thing to watch here in Georgia is not only the speed but also the progression of the mass of storms that are going to fire and move north with the warm front overnight.  Some of the hi res models push the convection more to the NE while a couple of models keep the heaviest convection more the the west over central and eastern Alabama.  If that scenario plays out and misses a large chunk of Georgia, it would probably set up some outflow boundaries that would be a focal point of any supercells that fire with the main show.

[LithiaWx]

24 minutes ago, audioguy3107 said:

Another thing to watch here in Georgia is not only the speed but also the progression of the mass of storms that are going to fire and move north with the warm front overnight.  Some of the hi res models push the convection more to the NE while a couple of models keep the heaviest convection more the the west over central and eastern Alabama.  If that scenario plays out and misses a large chunk of Georgia, it would probably set up some outflow boundaries that would be a focal point of any supercells that fire with the main show.

Just like with winter storms the timing of the event here is critical.  I got sucked in yesterday.  Not ready to bite again just yet.

 

We dont get too too many setups like this.  Need to cash in on some supercell before the summer patterns set in.  

[audioguy3107]

10 minutes ago, LithiaWx said:

Just like with winter storms the timing of the event here is critical.  I got sucked in yesterday.  Not ready to bite again just yet.

We dont get too too many setups like this.  Need to cash in on some supercell before the summer patterns set in.  

You're right, the difference with this setup, at least for eastern Alabama and Georgia is that it looks like the timing will not be an issue.  The thing here is how fast the warm front makes it north and takes the first wave of convection with it.  Normally we're all socked in with cool cloud cover until 6 PM or so and by then there's no time for any destablilization to take place, especially if there's any CAD.  Depending on what fires tonight is gonna make the difference between a relatively substantial threat vs. a possible high risk day which is pretty rare for our neck of the woods.

- Buck

[jburns]

1 hour ago, frazdaddy said:

Sadly true. Que Mr. Burns.

Agreed.  If anyone wants to debate this again, please no, take it to the banter forum. 

[lj0109]

CAE Morning AFD with some fairly strong wording for Midlands / CSRA:

National Weather Service Columbia SC
719 AM EDT Tue Apr 4 2017

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...

 

The reprieve from the severe weather event on Monday will be short lived as another significant event is expected to unfold on Wednesday. A deepening surface low over the middle of the country will lift northeastward into the western Ohio Valley Wednesday with an associated closed upper low. Ahead of the system over the Gulf Coast states a lead shortwave will move over the region and increasing flow off the Gulf of Mexico will provide strong moisture transport/advection northeastward into the forecast area with a 50-55 knot low level jet helping to destabilize the atmosphere and push a warm front through the region. Large scale upper forcing will be present with diffluent 500mb flow over the area.

Forecast soundings indicate moderate to strong instability will develop with surface heating and sufficient 0-6km shear will be present with values around 60 knots supporting organized severe convection. Wind profiles on forecast hodographs indicate strong veering of winds with strong speed shear supporting rotating updrafts. This is shaping up to potentially be a more widespread and significant event than Monday, which was quite an event in and of itself! SPC has upgraded part of our area to a moderate risk in the latest Day 2 outlook with the risk of long lived supercell storms and strong tornadoes given the steep mid level lapse rates and deep layer shear. Have increased pops across the area late Wednesday through Wednesday night to likely/categorical range.

In addition to the severe threat, there is a moderate flooding threat as well given the widespread rain that occurred on Monday. Precipitable water values are forecast to reach around 1.70 inches which is nearly 200 percent of normal which will support efficient rain rates enhanced by any training of storms. It appears the convection could come in two waves, the first during the late morning to early afternoon hours with initiated by the lead shortwave, with a second round possible early evening into the overnight hours as the strong upper low approaches coincident with strong 500mb height falls and cooling mid level temperatures.

 

[downeastnc]

MHX still using pretty strong language in their AFD's, setup reminds me of the other fairly nasty outbreaks we have had but maybe not as strong with all the players....if it does play out with strong long lived tornados the timing is horrible being overnight etc...guess we will wait and see but the NAM3k paints a scary picture as well with several discrete super cells over the I-95 corridor and then east from there. 

 

MHX overnight write up..

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 430 AM Tue...The big story through the long term period
continues to be the threat for a severe weather outbreak with
potential life-threatening severe thunderstorms Wednesday night
into Thursday. Cooler air will move in Friday through the
weekend with a warming trend expected early next week.

Wednesday through Thursday...Dangerous severe weather continues
to be a threat during this period. Large scale upper trough
amplification is expected over the Eastern US Wed/Thur in
response to upstream flow and phasing jet streams. This will
result in powerful cyclogenesis across the central Appalachian
region to the lower Great Lakes through Thursday. Some timing
differences remain with exact placement of synoptic features
during this period, though it appears that a potentially
widespread severe weather outbreak could affect the region. The
aforementioned trough attains a strong negative tilt as it
swings through the SE US and as a result deep rich moisture
gets advected into the region in tandem with very strong
dynamics to support severe thunderstorms. Tremendous height and
pressure falls occur early Thursday as the sfc low deepens to
around 985MB to the north. Latest guidance suite continues to
indicate 850H flow of 50-70 kt aided by 110+ kt 300MB jet, and
PW values 1.25-1.5". Even with the timing of the severe threat
relegated to Wednesday night and early Thursday, instability
parameters are quite high due to the sharp height falls yielding
steep mid level lapse rates, and sfc TD`s rising through the
60s overnight Wednesday. Hodographs are concerning in that
strong SRH values aoa 400 M2/S2 are fcst by the NAM/ECMWF with
low LCLs present. If all these ingredients come together the
threat for a few strong tornadoes and strong damaging winds
would be present.

[kayman]

2 hours ago, a5ehren said:

FFC's discussion seems perfectly reasonable for areas north of the Fall Line based on recent model performance:

 

That's exactly what I'm referring to underestimation the possibly of severe weather, i.e. tornadoes (particularly supercells that produce long-tracked tornadoes).  North Georgia has seen its long-tracked tornadoes before.  The current SPC forecast shows Atlanta in the bullseye of the activity and this will be more wind shear (at least 10+ knots higher), higher instability values/helocity, and higher CAPE values over the northern third of Georgia than Monday's system.  These are all the ingredients for the recipe for a high risk severe weather day.   However, it seems like FFC is always the last NWS office in the SE to take the potential seriousness of strong, long-track tornadoes until there have been multiple confirmed tornadoes within their forecast area.

[audioguy3107]

Lastest SREF from the SPC has pretty much all the parameters maxed out over eastern Alabama and north Georgia late tomorrow afternoon into the evening.  Plenty of CAPE, LI approaching -9 and the significant tornado parameter values approaching 7.  Yikes.  It's been a long time since we've seen these values.

- Buck

[Tyler Penland]

13 minutes ago, kayman said:

That's exactly what I'm referring to underestimation the possibly of severe weather, i.e. tornadoes (particularly supercells that produce long-tracked tornadoes).  North Georgia has seen its long-tracked tornadoes before.  The current SPC forecast shows Atlanta in the bullseye of the activity and this will be more wind shear (at least 10+ knots higher), higher instability values/helocity, and higher CAPE values over the northern third of Georgia than Monday's system.  These are all the ingredients for the recipe for a high risk severe weather day.   However, it seems like FFC is always the last NWS office in the SE to take the potential seriousness of strong, long-track tornadoes until there have been multiple confirmed tornadoes within their forecast area.

They've been better in past years. 

Also I don't blame them for being a bit cautious. The last couple runs of the NAM fail progress the warm front north of I-20 which would mitigate any tornado risk north of there. Models tend to advance warm fronts too quickly in these set-ups, wouldn't surprise me at all if that happens this time too.

[LithiaWx]

13 minutes ago, kayman said:

That's exactly what I'm referring to underestimation the possibly of severe weather, i.e. tornadoes (particularly supercells that produce long-tracked tornadoes).  North Georgia has seen its long-tracked tornadoes before.  The current SPC forecast shows Atlanta in the bullseye of the activity and this will be more wind shear (at least 10+ knots higher), higher instability values/helocity, and higher CAPE values over the northern third of Georgia than Monday's system.  These are all the ingredients for the recipe for a high risk severe weather day.   However, it seems like FFC is always the last NWS office in the SE to take the potential seriousness of strong, long-track tornadoes until there have been multiple confirmed tornadoes within their forecast area.

Are you saying you think a high risk will be issued for tomorrow?

[yotaman]

1 hour ago, Cold Rain said:

If you hate severe weather, all you need to do is move inside the blue area for the season, and you'll be adequately protected.

Is day 2 Wednesday and day 3 Thursday? Or am I off a day?

[kayman]

Just now, Tyler Penland said:

They've been better in past years. 

Also I don't blame them for being a bit cautious. The last couple runs of the NAM fail progress the warm front north of I-20 which would mitigate any tornado risk north of there. Models tend to advance warm fronts too quickly in these set-ups, wouldn't surprise me at all if that happens this time too.

I understand why, but like BMX and HUN they are in a region where the topography can play an interesting role in the enhancement of tornadic supercells.  We have witnessed too many times where systems have setup in locations where supercells will develop quickly and override wedge of "stable air" that typically stays over North Georgia.  Think of the setup with the 2008 Atlanta tornado outbreak or 1994 Palm Sunday tornado outbreak where things can be pushed out very quickly although there was a "wedge".

[Cold Rain]

24 minutes ago, yotaman said:

Is day 2 Wednesday and day 3 Thursday? Or am I off a day?

Yeah, I think that's correct.

[kayman]

10 minutes ago, LithiaWx said:

Are you saying you think a high risk will be issued for tomorrow?

I going to say there a strong possibly there will be a high risk area with the SPC having 45% and significant potential areas hatched in across parts of the northern third of Georgia.  This system is bullseying on GA because it will have shifted further east than most other systems.  I wouldn't be surprised if tomorrow afternoon we see a boundary of QLCS and/or discrete supercells form over the eastern portion of the Greater Birmingham area and move east.

[LithiaWx]

6 minutes ago, kayman said:

I going to say there a strong possibly there will be a high risk area with the SPC having 45% and significant potential areas hatched in across parts of the northern third of Georgia.  This system is bullseying on GA because it will have shifted further east than most other systems.  I wouldn't be surprised if tomorrow afternoon we see a boundary of QLCS and/or discrete supercells form over the eastern portion of the Greater Birmingham area and move east.

Atlanta has five million people in the metro.  Hopefully the local tv mets tonight convey the full magnitude of the situation developing 

[monsoonman1]

Echoing some sentiments above, this has the potential to be a major event. Obviously there are some questions to be answered (degree of morning junkvection mainly) but if the higher end scenarios are realized this could be one of the highest impact days in years. Going to be interested to see the evolution tonight/tomorrow morning. 

[wxtrackercody]

17 minutes ago, kayman said:

I going to say there a strong possibly there will be a high risk area with the SPC having 45% and significant potential areas hatched in across parts of the northern third of Georgia.  This system is bullseying on GA because it will have shifted further east than most other systems.  I wouldn't be surprised if tomorrow afternoon we see a boundary of QLCS and/or discrete supercells form over the eastern portion of the Greater Birmingham area and move east.

45% seems like a stretch and should be saved for the truly rare setups. Based on everything I'm looking at, a 30% hatched area across eastern Alabama and western Georgia seems in order though.

[DixieBlizzard]

13 minutes ago, LithiaWx said:

Atlanta has five million people in the metro.  Hopefully the local tv mets tonight convey the full magnitude of the situation developing 

I am sure Glenn Burns will have all of the stormgasms you could possibly wish for. He will be all over it.

[LithiaWx]

2 minutes ago, TropicalAnalystwx13 said:

45% seems like a stretch and should be saved for the truly rare setups. Based on everything I'm looking at, a 30% hatched area across eastern Alabama and western Georgia seems in order though.

I'm in the west metro Atlanta. Douglas county just 41 miles from Alabama. 

 

Bullseye at my location it seems.