18-20 March 2012 severe prospects

[Thundersnow12]

I haven't seen such instability and shear co-located at the same time in quite awhile. Those are high risk caliber parameters.

1. I hope you mean in the TX PH..

2. I highly doubt tomorrow is a HIGH. I can see 10-15% hatched.

[andyhb]

1. I hope you mean in the TX PH..

2. I highly doubt tomorrow is a HIGH. I can see 10-15% hatched.

Yes, for the first point.

[Superstorm93]

I doubt tomorrow will be a high risk, unless things continue to look more favorable.

Probably will wind up being a high-end Moderate at best.

Just like 2007...

[ZackH]

The 00Z NAM run is impressive, but there are WAY too many questions still to even mention High Risk at this time. I still say a high end slight or low end moderate for tomorrow. We could see some tornadoes tomorrow and even one or two strong... but lets not overhype this too much. It could still be a significant event and I'm not downplaying it, but lets be real. I'm out chasing, so I hope we do see something surprising, but a lot more things have to come into the picture to even think about a High.

[brettjrob]

I agree that HIGH risk talk is premature. But, I honestly also feel like some people are underplaying this and have been all along. I think a SLGT would be just as unjustified as a HIGH with the new SWODY1. I fully expect a 10% hatched tornado risk, with 15% not out of the question. If things look similar (with continued positive trends on boundary layer moisture) tomorrow morning, I think a 15% hatched is fairly likely, but we shall see.

EDIT: The idea that seeing tornadoes, even before sunset, tomorrow in the Panhandles would be "surprising" baffles me after viewing the 00z soundings and NAM. But, in your defense, there's a solid contingent of fellow chasers and forecasters who seem to share your view right now. As I said a couple days ago, one of the more difficult Plains forecasts in awhile, right down to the eleventh hour.

[andyhb]

I agree that HIGH risk talk is premature. But, I honestly also feel like some people are underplaying this and have been all along. I think a SLGT would be just as unjustified as a HIGH with the new SWODY1. I fully expect a 10% hatched tornado risk, with 15% not out of the question. If things look similar (with continued positive trends on boundary layer moisture) tomorrow morning, I think a 15% hatched is fairly likely, but we shall see.

EDIT: The idea that seeing tornadoes, even before sunset, tomorrow in the Panhandles would be "surprising" baffles me after viewing the 00z soundings and NAM. But, in your defense, there's a solid contingent of fellow chasers and forecasters who seem to share your view right now. As I said a couple days ago, one of the more difficult Plains forecasts in awhile, right down to the eleventh hour.

Excellent post.

[tornadotony]

I agree that HIGH risk talk is premature. But, I honestly also feel like some people are underplaying this and have been all along. I think a SLGT would be just as unjustified as a HIGH with the new SWODY1. I fully expect a 10% hatched tornado risk, with 15% not out of the question. If things look similar (with continued positive trends on boundary layer moisture) tomorrow morning, I think a 15% hatched is fairly likely, but we shall see.

EDIT: The idea that seeing tornadoes, even before sunset, tomorrow in the Panhandles would be "surprising" baffles me after viewing the 00z soundings and NAM. But, in your defense, there's a solid contingent of fellow chasers and forecasters who seem to share your view right now. As I said a couple days ago, one of the more difficult Plains forecasts in awhile, right down to the eleventh hour.

Regarding the bolded, I've kinda been in that camp for awhile. I think it might still be a bit difficult up in the NE panhandle prior to sundown. If I were chasing, my target would either be Mangum, OK, or Shamrock, TX, in the far SE panhandle/far SW OK region. The NAM and GFS have both been consistent with developing some sort of wave along the dryline, which creates a bulge that allows for 1) localized increased backing and 2) greater moisture convergence along the dryline.

With all that said, looking at the 00z models, I think the situation might become EXTREMELY dangerous from Shamrock up to Liberal between 00z and 06z tomorrow night. The NAM shows the boundary layer slow to decouple, with an extreme low-level shear profile and very fat CAPE. I could easily see there being one or two after dark, violent wedges in the eastern panhandles into far SW KS.

For reference, NAM sounding for just east of Liberal at 03z tomorrow night (time-sensitive):

If that doesn't scream violent tornado potential to you, then you need a mesoscale meteorology review and fast.

[tornadotony]

This is 06z west of Woodward. To have that little of an inversion progged at 06z on the plains is ABSURD! Good Lord, if this verifies...

[baroclinic_instability]

Given the progged mass ascent associated with the elongating poleward oriented jet streak during the evening (especially after 00-03z), the NAM boundary layer progs seem much more realistic than the GFS.

[on_wx]

The outlook is in and it's just a 5% tornado and 15% slight risk area

[andyhb]

Hmmmm....

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1156 PM CDT SAT MAR 17 2012

VALID 181200Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE CNTRL AND

SRN PLAINS...

...SYNOPSIS...

A FULL LATITUDE UPPER TROUGH WILL GRADUALLY SHIFT EWD FROM THE GREAT

BASIN ACROSS THE ROCKIES DURING THE DAY...EMERGING INTO THE HIGH

PLAINS BY MON MORNING. WHILE THE PRIMARY VORTICITY CENTER WILL BE

MOVING ACROSS THE FOUR CORNERS AREA DURING THE DAY...A LEAD

SHORTWAVE TROUGH IS EXPECTED TO MOVE OUT OF NRN MEXICO NEWD ACROSS

TX EARLY SUN AND INTO OK AND KS FROM MID TO LATE AFTERNOON. BEHIND

THIS LEAD WAVE...GRADUAL HEIGHT FALLS WILL PERSIST WITH THE MAIN

BODY OF THE TROUGH.

AT THE SURFACE...A BROAD AREA OF LOW PRESSURE WILL CONSOLIDATE OVER

THE NRN HIGH PLAINS...WITH A DISTINCT LOW PRESSURE TROUGH EXTENDING

SWD INTO W TX AND A COLD FRONT DEVELOPING OVER WY...CO AND NM. AHEAD

OF THIS TROUGH...BROAD SLY FLOW WILL BRING LOWER 60S F DEWPOINTS AS

FAR N AS IA AND IL. AN EML WILL EXIST OVER THE WARM

SECTOR...PREVENTING SURFACE BASED DEVELOPMENT FOR MUCH OF THE DAY.

TO THE E...A WEAK VORTICITY CENTER...ENHANCED BY ONGOING CONVECTION

THIS EVENING OVER IL AND IND...WILL PERSIST AS IT TRAVELS EWD ALONG

AND N OF THE OH RIVER. THIS FEATURE IS LIKELY TO FOCUS ADDITIONAL

THUNDERSTORM DEVELOPMENT DURING THE DAY.

...OK INTO ERN KS MIDDAY INTO AFTERNOON...

LIFT WITH THE LEAD SHORTWAVE IS LIKELY TO RESULT IN SCATTERED RAIN

AND STORMS DEVELOPING OVER NWRN TX INTO OK NEWD INTO SRN/ERN KS BY

LATE AFTERNOON. FORECAST SOUNDINGS INDICATE THAT THIS ACTIVITY COULD

BE ELEVATED ABOVE THE CAPPING INVERSION...WHERE STEEP LAPSE RATES

WILL EXIST. EVEN SO...WITH FAVORABLE EFFECTIVE SHEAR...SOME OF THIS

ACTIVITY COULD PRODUCE SOME HAIL.

...NWRN TX INTO WRN OK AND KS...

CONVERGENCE ALONG THE DRYLINE IS EXPECTED TO INCREASE AFTER ABOUT

21Z AS MASS FIELDS READJUST TOWARD THE WRN TROUGH AND AWAY FROM THE

LEAD SHORTWAVE. WITH STRONG HEATING AND NEARLY DRY ADIABATIC LAPSE

RATES THROUGH A DEEP LAYER W OF THE DRYLINE...A NARROW ZONE OF

STRONG INSTABILITY IS EXPECTED FROM WRN KS INTO THE ERN OK/TX

PANHANDLE SWD INTO NWRN TX. HERE...SHEAR PROFILES WILL STRONGLY

FAVOR SUPERCELLS...CAPABLE OF LARGE...PERHAPS VERY LARGE

HAIL...DAMAGING WIND GUSTS AND A COUPLE TORNADOES. WHILE LOW LEVEL

HODOGRAPHS DO ENLARGE AFTER 00Z...SO WILL CONVECTIVE INHIBITION WITH

BACKING SURFACE WINDS BRINGING RELATIVELY COOLER...YET STILL MOIST

AIR NWWD MEETING WITH THE COLD FRONT AROUND 03Z. ADDITIONAL ACTIVITY

IS LIKELY DUE TO STRONG FORCING...BUT MORE OF A LINEAR STORM MODE IS

EXPECTED...WITH PERHAPS HYBRID SUPERCELLS AND BOWING SEGMENTS

CAPABLE OF WIND AND HAIL.

THE SEVERE THREAT APPEARS MORE CONDITIONAL FARTHER N INTO NEBRASKA

WHERE STORMS MAY BE MORE ISOLATED.

...IL...IND...OH...NRN KY...

CONVECTION WILL BE ONGOING ACROSS THE OH VALLEY EARLY SUNDAY...AND

MAY REJUVENATE ESPECIALLY ON THE WRN FRINGE AS SWLY 850 MB FLOW

MAINTAIN A MOIST AND UNSTABLE FEED OF AIR INTO THE BACK SIDE OF THIS

SYSTEM. AREAS OF HEATING ARE EXPECTED...AND OVERALL LAPSE RATES

PROFILES MAY FAVOR SEVERE HAIL IN THE STRONGER CORES...ESPECIALLY

NEAR PEAK HEATING. DEEP LAYER SHEAR WILL BE WEAK...SUGGESTING PULSE

OR MULTICELLS. AS SUCH...A SLIGHT RISK IS NOT WARRANTED.

..JEWELL/HURLBUT.. 03/18/2012

[andyhb]

I mean I know that is the first Day 1 of the day, but come on...even if you do get hybrid supercell/linear convection they will likely be full of embedded circulations with the progged low level shear in place...and the H5 shear vectors strongly favor discrete cells anyway.

[tornadotony]

I'm in awe. Even with a hybrid setup, if you get the parameters in place, you can get strong-violent tornadoes. Just ask Denning, AR residents.

[JoMo]

I did see the CIN rapidly increase but I'm a bit confused by the wording of the paragraph andyhb highlighted with only a 15% hatched hail and 15% wind.

[Superstorm93]

That's really interesting.

Completely contradicts everything that's been said on here.

[andyhb]

I'm in awe. Even with a hybrid setup, if you get the parameters in place, you can get strong-violent tornadoes. Just ask Denning, AR residents.

Or Vilonia/Hot Springs Village, AR...

[tornadotony]

For Monday:

[andyhb]

I'm thinking its a really bad idea to base their outlook on CIN increasing when it is virtually broken at 00z...

This hodograph off of the 00z NAM is in an uncapped area east of Lubbock at 03z:

[ZackH]

I agree that HIGH risk talk is premature. But, I honestly also feel like some people are underplaying this and have been all along. I think a SLGT would be just as unjustified as a HIGH with the new SWODY1. I fully expect a 10% hatched tornado risk, with 15% not out of the question. If things look similar (with continued positive trends on boundary layer moisture) tomorrow morning, I think a 15% hatched is fairly likely, but we shall see.

EDIT: The idea that seeing tornadoes, even before sunset, tomorrow in the Panhandles would be "surprising" baffles me after viewing the 00z soundings and NAM. But, in your defense, there's a solid contingent of fellow chasers and forecasters who seem to share your view right now. As I said a couple days ago, one of the more difficult Plains forecasts in awhile, right down to the eleventh hour.

Are you talking to me? Because I specifically said that I expect tornadoes tomorrow with one or two possibly strong. I absolutely never said anything about tornadoes tomorrow being "surprising." I said I hope we see something surprising... as in a stout regional tornado outbreak. Please do not misquote me. I was just addressing the high risk talk... its just downright ridiculous to think this could be a high risk setup ATM.

[tornadotony]

Now, they could be using the GFS thermos (which is rarely a good idea, especially 24h out). With that map above and the given mechanical overturning of the PBL you're going to see with a 50-55kt LLJ, you're likely gonna have no problem with sfc-based convection after dark.

[Ed Lizard]

NAM sim radar shows a generally linear feature West of Houston Tuesday morning, but with the LCLs, even with skinny CAPE that early, and the low level winds, I'd expect at least isolated spin ups with that line.

[andyhb]

NAM sim radar shows a generally linear feature West of Houston Tuesday morning, but with the LCLs, even with skinny CAPE that early, and the low level winds, I'd expect at least isolated spin ups with that line.

I'd be weary in trusting that, given the shear vectors and lack of unfavorable wind profiles for discrete supercells.

[baroclinic_instability]

Now, they could be using the GFS thermos (which is rarely a good idea, especially 24h out). With that map above and the given mechanical overturning of the PBL you're going to see with a 50-55kt LLJ, you're likely gonna have no problem with sfc-based convection after dark.

Partially true, but the nocturnal LLJ is partially in response to some amount of boundary layer decoupling in the absense of "dynamically" induced convergence/divergence patterns. But in this case it seems the combo activity of increasing cross-barrier mtn flow and and an increasingly elongating and intensifying/active upper jet will be the bigger factor in the strength of the increasing low level mass response. I generally agree that the NAM is likely more indicative of what the boundary layer will do given the setup.

Some guidance does develop weak inversions/isothermal layers above the boundary layer as the event goes on (possibly mesoscale driven subsidence...not sure). That would possibly cause issues with LCL-LFC RH values which may inhibit some development. Hard to say, the model solutions range from outbreak (CMC and to a degree NAM/GFS) to more isolated event (some of the convective allowing hi-res guidance). I will say I was a bit surprised to see what seemed to be a "downtrend" in the outlook though.

[Superstorm93]

Off the 00z ARW

Some insane updrafts

[andyhb]

That monster updraft in the E TX Panhandle would be bad news, to say the least (Of course it goes right over Canadian) and the parameters out ahead of it are nasty. I'd tend to think that even if we do only get a couple of discrete supercells, we could end up with a November 7th of last year type threat.

[Stebo]

I am a bit surprised at the modest wording on the Day 1 outlook. I think this certainly has the potential to be a lot stronger than they are currently forecasting.

[baroclinic_instability]

I am a bit surprised at the modest wording on the Day 1 outlook. I think this certainly has the potential to be a lot stronger than they are currently forecasting.

I think a hatched tor would have been more than acceptable given the incredible low level shear and near dry adiabatic lapse rates through such a deep layer. Coverage wise, at least in my opinion, seems to be the bigger question.

[Stebo]

I think a hatched tor would have been more than acceptable given the incredible low level shear and near dry adiabatic lapse rates through such a deep layer. Coverage wise, at least in my opinion, seems to be the bigger question.

I think a lack of a 30% hail threat is a bit surprising too.

[baroclinic_instability]

Off the 00z ARW

Some insane updrafts

Where did you get those ARW plots?

[brettjrob]

Are you talking to me? Because I specifically said that I expect tornadoes tomorrow with one or two possibly strong. I absolutely never said anything about tornadoes tomorrow being "surprising." I said I hope we see something surprising... as in a stout regional tornado outbreak. Please do not misquote me. I was just addressing the high risk talk... its just downright ridiculous to think this could be a high risk setup ATM.

Sorry about the misunderstanding. I latched onto your statement "I hope we see something surprising" and should have read the rest of your post more carefully. Our thoughts probably aren't too far apart... I'm just a touch more bullish for now.