April 4-6 Severe Weather

[ATL_Militarypolice]

SPC mentions in the 4-8 day forecast more severe weather early next week across the Central Plains and eventually into the lower Mississippi River Valley and southern states.

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0355 AM CDT TUE MAR 29 2011

VALID 011200Z - 061200Z

...DISCUSSION...

MODEL CONSENSUS IS THAT PATTERN WILL REMAIN PROGRESSIVE IN THE 4-8

PERIOD WITH THE NEXT IN A SERIES OF SIGNIFICANT SHORTWAVE TROUGHS

LIKELY MOVING INTO THE PLAINS DAY 6-7. IT IS CERTAINLY POSSIBLE THAT

A SIGNIFICANT SEVERE EVENT COULD EVOLVE OVER THE PLAINS BY DAY

6-7...SPREADING INTO THE LOWER MS VALLEY AND SERN STATES DAY 7-8 AS

MOISTURE RETURNS NWD THROUGH PRE-FRONTAL WARM SECTOR.

HOWEVER...CONSIDERABLE RUN TO RUN INCONSISTENCIES EXIST WITH THE

DETERMINISTIC MODELS AND ENSEMBLE MEMBERS ARE DISPERSIVE BEYOND DAY

5 REGARDING AMPLITUDE AND TRAJECTORY OF THE SHORTWAVE TROUGH. AT

THIS TIME PREDICTABILITY REMAINS LOW...BUT PORTIONS OF THE PLAINS

INTO THE SERN STATES WILL PROBABLY NEED TO BE INCLUDED IN A RISK

AREA IN LATER OUTLOOKS FOR DAY 6-7.

Looking at the two major Global models there is extreme differences with the overall evolution/placement of the system. With the 0Z GFS tracking the low from southern Iowa Sunday afternoon towards the Great Lakes bringing what looks to be a MCS event along the front Monday into Tuesday. Where as the 0Z ECMWF has the low over the Texas Panhandle Sunday afternoon as a high pressure system drops in from Canada into the Central Plains this high suppresses the storm into Southern Texas Monday with thunderstorms developing out ahead of the developing system with what looks to be rapid destabilization as the 570 DM line pushes north of LA/AL/MS into northern GA. Come Tuesday afternoon the system closes off at 500MB over Arkansas with a very potent low-level jet as the low tracks into the Tennessee Valley.

[eyewall]

Hopefully NC will get in on this one. I have my eye on it as well.

[ryan1234]

Hopefully NC will get in on this one. I have my eye on it as well.

Im with you Eyewall! Bring on spring! NC style! lol

[lincolncent]

This one looks to be much more widespread than the last few. Climatology definitely supports a tornado outbreak in the first half of April so this is quite concerning.

[eyewall]

Well the GFS has decent timing for central and eastern NC on the 5th if it holds. I am sure it will change though.

[ATL_Militarypolice]

To me the GFS looks to be more of a linear storm threat as the low and overall dynamics are farther to the north and frontal boundary pushes toward the region. If the GFS trends the low further south much like the Euro this could be quite a significant threat and more widespread severe threat than the previous ones. The 0Z Euro had widespread 2000+ Capes for Monday afternoon from E TX into KATL then north over Western TN towards the KY border. Dew-points toward 70 degrees with a Theta-E ridge up to 350K that's an impressive warm sector per the models so far, and the severe threat does look to continue east into the Carolinas.

[eyewall]

Yeah you are right in terms of low placement. Ideally I would not mind seeing a triple point cross the piedmont at peak heating .

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[ryan1234]

Yeah you are right in terms of low placement. Ideally I would not mind seeing a triple point cross the piedmont at peak heating .

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When you go on a chase, do you normally stay in your area? Or is there a certain distance you are willing to travel? I hope that this go around all of NC see's something!

[audioguy3107]

To me the GFS looks to be more of a linear storm threat as the low and overall dynamics are farther to the north and frontal boundary pushes toward the region. If the GFS trends the low further south much like the Euro this could be quite a significant threat and more widespread severe threat than the previous ones. The 0Z Euro had widespread 2000+ Capes for Monday afternoon from E TX into KATL then north over Western TN towards the KY border. Dew-points toward 70 degrees with a Theta-E ridge up to 350K that's an impressive warm sector per the models so far, and the severe threat does look to continue east into the Carolinas.

Don't worry, I'm sure we'll have a wedge building in with temps in the upper 40s to low 50s while James Spann will be freaking out on the air over in Birmingham.

[downeastnc]

Well the GFS has decent timing for central and eastern NC on the 5th if it holds. I am sure it will change though.

Sweet I have that day off....this of course means it wont happen but we can hope. Really my truck needs a a few repairs done before I take it chasing. If this looks legit especially in the east we may need to hook up.

[ATL_Militarypolice]

Latest from SPC.

MONDAY /DAY 6/...POTENTIAL WILL EXIST FOR A MORE SUBSTANTIAL SEVERE THREAT AS MOISTURE ADVECTS NEWD THROUGH THE MS AND TN VALLEY REGIONS...EAST OF AMPLIFYING...BUT PROGRESSIVE UPPER TROUGH. STORMS MAY DEVELOP ALONG AND EAST OF SEWD ADVANCING FRONT ALONG ERN PERIPHERY OF WARMER EML PLUME. STRENGTH OF LOW-LEVEL JET AND DEEP SHEAR ALONG WITH ADEQUATE INSTABILITY COULD SUPPORT THE POTENTIAL FOR A SIGNIFICANT SEVERE EVENT.

IF MODEL SOLUTIONS CONTINUE TO CONVERGE...A RISK AREA WILL LIKELY NEED TO BE INTRODUCED IN THE NEXT 4-8 UPDATE...ESPECIALLY FROM THE MS VALLEY THROUGH THE SERN STATES AND POSSIBLY INTO SRN PARTS OF THE OH VALLEY.

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[eyewall]

When you go on a chase, do you normally stay in your area? Or is there a certain distance you are willing to travel? I hope that this go around all of NC see's something!

It depends on the risk level and storm type. I drove a couple of hundred miles last October to chase supercells near the VA border.

[eyewall]

Sweet I have that day off....this of course means it wont happen but we can hope. Really my truck needs a a few repairs done before I take it chasing. If this looks legit especially in the east we may need to hook up.

Well if it pans out I will be there. If the risk is good enough I will try and get out of work .

[ATL_Militarypolice]

12Z Models have come in a better agreement as far as track and timing of this system with the Euro just a little faster. Both models track the system through the TN Valley on Tuesday. 12Z Tuesday the Euro has 60-65 degree dew-points lifting all the way into Southern Ohio then from Eastern GA into the Carolinas, with 65-70 degree dew-points across Dixie Alley. By 18Z 65-70 degree Td move across Georgia, and by 0Z some 65 Td move into portions of the Carolinas. The Euro has a very potent low-level jet 55+ across the region as a whole at 12Z Tuesday. By 18Z 60+ KTs at 850 move in across Georgia and into the Carolinas by 0Z. Mid-levels do look to moist, this combined with cloud cover doesn't really help much in the way of destabilization, but I don't put too much confidence in instability parameters this far out especially with the global models. Needless to say we can't ignore an impressive widespread warm sector with a very potent low-level jet over 60Kts at 850MB. The GFS had SFC-500 MB shear above 70KTs. Looking at hodos they are impressive in the lowest of levels (0-1KM) with over 300 M2/S2 for majority of the region.

[Ellinwood]

Looks like the makings of a pretty big tornado outbreak to me... some of the instability needs to line up better to raise the confidence, but the synoptics and moisture are certainly primed. It's going to be a very dangerous system.

[ryan1234]

Looks like the makings of a pretty big tornado outbreak to me... some of the instability needs to line up better to raise the confidence, but the synoptics and moisture are certainly primed. It's going to be a very dangerous system.

Hopefully GA and the Carolina's can get in on this system. I hate watching storms fizzle as the cross in GA line.

[eyewall]

Looks like the makings of a pretty big tornado outbreak to me... some of the instability needs to line up better to raise the confidence, but the synoptics and moisture are certainly primed. It's going to be a very dangerous system.

bring on the chase day!

[FoothillsNC]

bring on the chase day!

Tues. is starting to look pretty good and there should be NO wedge at all this time. Its a very progressive front, and right now the timing looks pretty good for the Carolinas being peak heating Tues. PM. The unknown of course is instability, mid and high clouds, but as others pointed out, good dynamics along with dewpoint surge and low level jet.

[Marion_NC_WX]

Tues. is starting to look pretty good and there should be NO wedge at all this time. Its a very progressive front, and right now the timing looks pretty good for the Carolinas being peak heating Tues. PM. The unknown of course is instability, mid and high clouds, but as others pointed out, good dynamics along with dewpoint surge and low level jet.

Seems like for the last 10 years anytime we have a prime setup in place for severe weather, there is a wedge or stable layer that prevents the worst of weather from getting much farther north of I-20 or I-85.

[FoothillsNC]

Seems like for the last 10 years anytime we have a prime setup in place for severe weather, there is a wedge or stable layer that prevents the worst of weather from getting much farther north of I-20 or I-85.

Yeah, its never a shoe in for severe on this side of the Apps and esp. nearer the mountains you go. However, there is absolutely zero wedging or cold damming being shown on any models right now, theres no slight confluence in the Northeast, No high pressure, just pure southerly flow at all levels, and very warm 850's temps, and a full latitude trough, so, unless things change, I actually believe this is good for the Carolinas severe chances. 9 times out of 10, we'll have one of these ingredients missing, usually there's a residual stable layer present, like you said thanks in part to some kind of high pressure to our north, but that looks absent finally.

[ATL_Militarypolice]

SPC has day 4-6 outlined. Day 5 includes much of the south with day 6 including eastern Carolina's

[FoothillsNC]

Winds off the surface could be roaring, just in time for peak heating. This event could have a lot going for it to make a classic severe outbreak, but its still far enough out in time for some changes.

...DAY 5...

WIDESPREAD SEVERE STORMS ARE BECOMING INCREASINGLY PROBABLE DAY 5.

GULF MOISTURE WILL ADVECT NWD THROUGH LOWER-MID MS VALLEY...SERN

STATES AND OH VALLEY IN ASSOCIATION WITH VERY STRONG EWD MIGRATING

LLJ. MORE WIDESPREAD THUNDERSTORM DEVELOPMENT WILL BECOME PROBABLE

AS FORCING FOR DEEP ASCENT ATTENDING THE UPPER TROUGH SHIFTS EAST OF

STRONGER EML. THREAT WILL EXIST FOR SUPERCELLS AND LINE SEGMENTS

WITH TORNADOES...LARGE HAIL AND DAMAGING WIND.

[burkecountync]

I am excited about the possibilities with this storm. The models are doing their normal thing; however, I think that there will be some strong to severe storms on Tuesday in North Carolina. This could be one of the worst severe weather outbreaks we have seen in a long time across the Carolinas.

[ryan1234]

I am excited about the possibilities with this storm. The models are doing their normal thing; however, I think that there will be some strong to severe storms on Tuesday in North Carolina. This could be one of the worst severe weather outbreaks we have seen in a long time across the Carolinas.

I think so too. Lets hope it all works out. We are way over due for a significant severe weather outbreak. March of 2008 could of been it, but we had that stupid wedge in place all day.

[FoothillsNC]

Only the GGEM is not showing a severe outbreak now. There's still the off chance the GGEM or Euro initially had the right idea, but HPC is also going with a more progressive look, so the odds are this is going to be a big outbreak. Its a full-lat trough that goes neg. tilt toward the Southeast, the questions now assuming thats right, will be speed. The GFS is slightly slower now, but for whichever area is affected at prime time heating and with the incoming dynamics, it could become a memorable outbreak. As usual instability and shear values won't be known til much closer to the event. One thing striking is the Gulf inflow, anda lot of isobars wrapping in from the outflow of a Bermuda high, and how warm it is ahead of the front, throughout the warm sector which encompasses the southeast third of the country. The Carolinas a lot of time are spared outbreaks because of a low level cool, damp dome , some residual cad, but theres no hint of that on the GFS or ECMWF right now, just pure warm advection and a strong clash of cold air near a classic triple point and strongly developing low in the wstern part of Ky area. The GFS takes the perfect track and has the looks of really bad outbreak, the ECMWF not quite as bad, but still something most likely. If the Canadian is right, it would be more of a heavy rain threat like the ECMWF showed a few days ago. I think by 12z Sat we will have good agreement on this.

[ryan1234]

Only the GGEM is not showing a severe outbreak now. There's still the off chance the GGEM or Euro initially had the right idea, but HPC is also going with a more progressive look, so the odds are this is going to be a big outbreak. Its a full-lat trough that goes neg. tilt toward the Southeast, the questions now assuming thats right, will be speed. The GFS is slightly slower now, but for whichever area is affected at prime time heating and with the incoming dynamics, it could become a memorable outbreak. As usual instability and shear values won't be known til much closer to the event. One thing striking is the Gulf inflow, anda lot of isobars wrapping in from the outflow of a Bermuda high, and how warm it is ahead of the front, throughout the warm sector which encompasses the southeast third of the country. The Carolinas a lot of time are spared outbreaks because of a low level cool, damp dome , some residual cad, but theres no hint of that on the GFS or ECMWF right now, just pure warm advection and a strong clash of cold air near a classic triple point and strongly developing low in the wstern part of Ky area. The GFS takes the perfect track and has the looks of really bad outbreak, the ECMWF not quite as bad, but still something most likely. If the Canadian is right, it would be more of a heavy rain threat like the ECMWF showed a few days ago. I think by 12z Sat we will have good agreement on this.

That's what I want to hear! Let's hope the Canadian is wrong. I think now would be a good time for everyone to dust off there weather radio's and keep a close on this system through the weekend.

[FoothillsNC]

the warm buoyant air pushing ahead of this deep trough is pretty major. The NAM at 84 hour even has +24 at 850, which is unbelievable for early April, even in the southern Plains. It won't be that warm in the SE but will be +15 to +18, which is extremely impressive.

[ryan1234]

This system looks to have all the makings of a very dangerous severe weather outbreak. One that will go on for days. I know it's early, but how significant is the threat for EF4 and EF5 tornadoes?

[Gastonwxman]

It's rather disturbing of how this event is progged to occur around the time of the April 3-4 1974 Super Outbreak, though in this case I don't foresee a redux of that event happening with this setup but rather it will be severity of the storms themselves. I wasn't around during the time of that tornadic outbreak but I've heard that the damage was unimaginable across the OV and the SE. This year will mark the 37th Anniversary of that event.

For those of you not familiar with it, here's a link explaining why it occurred: http://www.april31974.com/The_storm.html

Aside from that, we already know what few things to consider here for next week's event, one of them being the CAPE values, which still seems to remain on the moderate to high side per the modeling and would suggest that the overall thermodynamics would affect a rather large portion of the southeast. We also have to look into how well the development of the upper level trough does for determination of potential scattered pre-frontal convection, combining those factors with the abundance of low level moisture, the potential for high lapse rates, etc. Lots of details to iron out but we will likely know for sure as we progress through the weekend, especially by the time this system materializes and gets its act together. I'm interested to see how well the verification of the modeling is compared to reality. Should make for a very interesting period throughout the day Tuesday.

[Marion_NC_WX]

the warm buoyant air pushing ahead of this deep trough is pretty major. The NAM at 84 hour even has +24 at 850, which is unbelievable for early April, even in the southern Plains. It won't be that warm in the SE but will be +15 to +18, which is extremely impressive.

The Gulf looks wide-a** open for business early next week. I like how that upper high sits over the Bahamas creating a strong pump of moisture...I would love to see that come late spring and early summer.