Significant severe weather threats 4/8-10

[Srain]

Winds actually veer more west on 00Z GFS which would aid the supercell duration hopefully in central Texas. SFC-500 mb bulk shear is pretty decent too at 50-60 kt.

I believe locations from the Edwards Plateau on N and E into the Hill Country (Austin Area) may need to be monitored just ahead of the dry line late Tuesday into Wednesday. The cap looks erode even down here in the Houston Area Wednesday. That said I am becoming a bit more interested that a wide spread severe event may in fact be in the cards.

[It's Always Sunny]

I believe locations from the Edwards Plateau on N and E into the Hill Country (Austin Area) may need to be monitored just ahead of the dry line late Tuesday into Wednesday. The cap looks erode even down here in the Houston Area Wednesday. That said I am becoming a bit more interested that a wide spread severe event may in fact be in the cards.

I am a bit worried about the amount of widespread CIN as you move east but I'm hoping it erodes throughout the day to the point where we see widespread activity along the front.

[soonertrey]

Is anyone concerned about this trough developing into a closed-low?

[DaculaWeather]

EXTENDED FORECAST DISCUSSION

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

1228 AM EDT FRI APR 05 2013

VALID 12Z MON APR 08 2013 - 12Z FRI APR 12 2013

THE EUROPEAN CENTRE ENSEMBLE MEAN HAS BEEN QUITE STABLE OVER THE

PAST FOUR CYCLES, BOTH WITH THE TROUGH OVER THE WEST AND THE

LATITUDE OF THE POLAR FRONT OVER THE EAST. RELIED ON IT AS OPPOSED

TO ANY OF THE DETERMINISTIC SOLUTIONS--ECMWF INCLUDED--PRIMARILY

BECAUSE OF THE SENSITIVITY OF THE TEMPERATURE FORECASTS NEAR THE

INTENSE BAROCLINIC ZONE EAST OF THE MISSISSIPPI RIVER. THE PATTERN

IS ESSENTIALLY A NORTHWARD-SHIFTED VERSION OF THE MARCH FLOW

REGIME, WITH A CONTINUED FEED OF COLD AIR THROUGH CANADA FROM THE

ARCTIC REGION. THE NORTHWARD SHIFT IS ALLOWING MUCH BETTER INFLOW

FROM THE GULF OF MEXICO--A FACTOR WHICH WILL COME INTO PLAY AS

THE MAIN SYNOPTIC WAVE EMERGES ONTO THE GREAT PLAINS FROM THE WEST

BY MID PERIOD. EXPECT THE CONFLUENCE OVER SOUTHEAST CANADA TO

STRENGTHEN AND SHIFT SOUTHWARD FROM DAY 5 ONWARD, CAPPING THE

NORTHWARD PROGRESS OF THE PRIMARY SURFACE LOW OVER THE OHIO VALLEY.

CISCO

[LocoAko]

I was just referring to the 0-1 km layer, which is to the right of the MLLCL.

 

Regardless, that is a pretty classic Plains significant tornado sounding, assuming initiation of course.

 

Oh, I see it now. My bad.

[brettjrob]

Derided as it is in this range, it's always interesting to see the NAM speak on an event for the first time. In this case, it's a lot stingier on moisture for Monday than the GFS has been all along, something I've been concerned about. Partially as a result, the cap looks close to prohibitive along most of the dryline. On the other hand, it is much faster with the trough, and even ejects it cleanly in one piece Monday evening. The H5 map at H+84 is absolutely textbook for a significant outbreak over the southern High Plains, if moisture were only a little better and capping a little weaker. Both conditions could be met, although the ongoing drought (which hasn't been relieved as much out west) is not encouraging in these borderline situations.

 

If the NAM is fairly correct on timing (and honestly, I think the trend is in its favor since yesterday), large-scale ascent would arrive almost in time to erode the cap quickly Monday evening. It could be a late show, even primarily after dark perhaps, but still fairly significant.

[It's Always Sunny]

Derided as it is in this range, it's always interesting to see the NAM speak on an event for the first time. In this case, it's a lot stingier on moisture for Monday than the GFS has been all along, something I've been concerned about. Partially as a result, the cap looks close to prohibitive along most of the dryline. On the other hand, it is much faster with the trough, and even ejects it cleanly in one piece Monday evening. The H5 map at H+84 is absolutely textbook for a significant outbreak over the southern High Plains, if moisture were only a little better and capping a little weaker. Both conditions could be met, although the ongoing drought (which hasn't been relieved as much out west) is not encouraging in these borderline situations.

 

If the NAM is fairly correct on timing (and honestly, I think the trend is in its favor since yesterday), large-scale ascent would arrive almost in time to erode the cap quickly Monday evening. It could be a late show, even primarily after dark perhaps, but still fairly significant.

Winds appear to be too SSW behind the dry line for anything long lasting at that time. Aside from it being later, you have (like you said) that decent cap which will make it harder for things to fire off. Cape values begin to drop off as well. I do think Tuesday is going to be the better of the two though.

[andyhb]

12z GFS...going significantly north on Monday...

[brettjrob]

Winds appear to be too SSW behind the dry line for anything long lasting at that time. Aside from it being later, you have (like you said) that decent cap which will make it harder for things to fire off. Cape values begin to drop off as well. I do think Tuesday is going to be the better of the two though.

 

By SSW winds behind the dryline, I assume you mean sfc convergence looks less than impressive? If so, that's true, looking at the 84 hr panel.

 

I think Tuesday will certainly have more widespread convection and probably more severe reports. I'm still not sold on the "quality" of that setup, though, particularly if the NAM is anywhere near correct on its timing. Meridional upper winds are likely to be an issue, at least over part of the warm sector.

[David Reimer]

I've said it before and I'll say it again, the NAM is crap outside 72 hours. Be cautious when using it for the first two runs (12Z & 18Z). I've seen it make radical jumps in both timing and position many times in the long range. 

[It's Always Sunny]

By SSW winds behind the dryline, I assume you mean sfc convergence looks less than impressive? If so, that's true, looking at the 84 hr panel.

 

I think Tuesday will certainly have more widespread convection and probably more severe reports. I'm still not sold on the "quality" of that setup, though, particularly if the NAM is anywhere near correct on its timing. Meridional upper winds are likely to be an issue, at least over part of the warm sector.

Yup.

 

FWIW...

[It's Always Sunny]

I've said it before and I'll say it again, the NAM is crap outside 72 hours. Be cautious when using it for the first two runs (12Z & 18Z). I've seen it make radical jumps in both timing and position many times in the long range. 

You should see my 2013 Motto in my signature section. It's not the most reliable model but it's good to refer to when it "jumps on board" with another model and the timing of when that happens as well (whether it's 3 days out, 1 day out, etc.).

[Chicago Storm]

I've said it before and I'll say it again, the NAM is crap outside 72 hours. Be cautious when using it for the first two runs (12Z & 18Z). I've seen it make radical jumps in both timing and position many times in the long range.

This. Though even at 24+hrs out it has been quite terrible the past several months. I'm talking GGEM bad.

I see the GFS is coming in with yet another sig different solution.

[RCNYILWX]

This. Though even at 24+hrs out it has been quite terrible the past several months. I'm talking GGEM bad.

I see the GFS is coming in with yet another sig different solution.

Way different, the surface low is over western Wisconsin by 00z Tuesday evening. 

 

[andyhb]

Only a 600-700 mile shift between runs...

[David Reimer]

You gotta love the GFS and how it likes to try and please everyone with its wide array of solutions. I guess the only reasonable thing to do is go outside and enjoy the spring-like weather. 

[It's Always Sunny]

Only a 600-700 mile shift between runs...

Yeah it's crazy how one tick in upper atmosphere dynamics has such a large trickle down effect. These changes are obviously normal, and expected, but I think the anticipation is what is doing us in.

[RCNYILWX]

Only a 600-700 mile shift between runs...

Though the AO will likely be headed positive, with there being a decent chance on the ensembles of the NAO still being negative early-mid next week, not sure if the trough and surface low will be able to blast that far north. And until the UL system gets onshore, there's certain to be more shifts in the guidance.

[Ian]

I've said it before and I'll say it again, the NAM is crap outside 72 hours. Be cautious when using it for the first two runs (12Z & 18Z). I've seen it make radical jumps in both timing and position many times in the long range. 

 

Even that seems kind on its range.

[David Reimer]

Even that seems kind on its range.

I was being generous. In reality, outside of 48-60 hours is comparable to hour 224 on the GFS. 

[Ian]

I was being generous. In reality, outside of 48-60 hours is comparable to hour 224 on the GFS. 

 

yeah, makes sense. i like it if it is in general agreement by about 48 but usually more like 12-24.  

 

not sure what to think.. so many runs of a pretty solid trough location etc. time of year makes it a little suspect further west.. the SPC outlook is more a climo look even with an anomalous sys. i'd probably ride the euro .. the gfs is kinda iffy even in this range when it shifts markedly especially. 

[Ed Lizard]

GFS suggests a brief appetizer Sunday evening near/just East SPS.

[Ian]

one thing these systems do is point out how many people forecast for potential. it's pretty stupid how even the big guys at TWC start screaming major tornado outbreak 5+ days in advance. maybe it's just because it's been kinda quiet for a while (gulf coast stuff doesnt count. )

[brettjrob]

GFS suggests a brief appetizer Sunday evening near/just East SPS.

 

Worth keeping an eye on, even though the cap is unbreakable verbatim on that sounding. The GFS does show some erosion in SW OK, while the NAM says forget about it. While unlikely, it wouldn't completely shock me if we get a rogue storm Sunday evening and then cap bust Monday.

[It's Always Sunny]

one thing these systems do is point out how many people forecast for potential. it's pretty stupid how even the big guys at TWC start screaming tornado outbreak 5+ days in advance. maybe it's just because it's been kinda quiet for a while (gulf coast stuff doesnt count. )

Yeah but it's their attempt of notifying the public early because it's the best safeguard we've got to this point.

[JoMo]

Well, that run didn't really clear anything up. 

 

TWC and Reed Timmer screaming tornado outbreak as expected. 

[Ian]

Yeah but it's their attempt of notifying the public early because it's the best safeguard we've got to this point.

not sure i believe that but maybe im cynical. tornadoes are a big traffic draw.

 

no reason not to say next week looks like a severe weather week but the constant running to the high end of potential gets old and probably doesn't help in cases where we actually look extremely likely to reach that potential.. most of those aren't totally apparent at this range either i wouldnt think.

[brettjrob]

not sure i believe that but maybe im cynical. tornadoes are a big traffic draw.

 

no reason not to say next week looks like a severe weather week but the constant running to the high end of potential gets old and probably doesn't help in cases where we actually look extremely likely to reach that potential.. most of those aren't totally apparent at this range either i wouldnt think.

 

Agreed. Though I think there are two separate factors at work. The usual hypesters are at it for the same cynical reasons you suspect. But among chasers and enthusiasts, I think you're correct that there's an optimistic bias at the beginning of the season when the first solid setup shows itself. It's harder to keep perspective when you haven't even seen a trough with 60 dewpoints for 8 months, and I know I'm guilty of that, too. These model runs from the past few days, were it late May, probably would have been scrutinized more for potential modes of failure.

[Ian]

Agreed. Though I think there are two separate factors at work. The usual hypesters are at it for the same cynical reasons you suspect. But among chasers and enthusiasts, I think you're correct that there's an optimistic bias at the beginning of the season when the first solid setup shows itself. It's harder to keep perspective when you haven't even seen a trough with 60 dewpoints for 8 months, and I know I'm guilty of that, too. These model runs from the past few days, were it late May, probably would have been scrutinized more for potential modes of failure.

 

For sure. I don't really blame anyone in the area for that. I'd be pretty excited given the model runs of the past week or so.. any difficulties or bust potential aside. Hopefully it's a good sign moving forward..

[It's Always Sunny]

Agreed. Though I think there are two separate factors at work. The usual hypesters are at it for the same cynical reasons you suspect. But among chasers and enthusiasts, I think you're correct that there's an optimistic bias at the beginning of the season when the first solid setup shows itself. It's harder to keep perspective when you haven't even seen a trough with 60 dewpoints for 8 months, and I know I'm guilty of that, too. These model runs from the past few days, were it late May, probably would have been scrutinized more for potential modes of failure.

I agree. I was just saying how even though this may be a lot of hype, it is still the safe approach (on TWC/SPC) to tell the public that there is a possibility something can happen. Definitely a rating boost for TWC.