andyhb

3 minutes ago, jojo762 said:

00z GFS continues to be pretty solid for sunday. Hate that the LLJ is WAY veered, but shouldn't matter too much. Solid BL-moisture, strong/moderate instability, strong deep-layer shear, and more-than-sufficient low-level shear. Best thing though? Storms **should** be discrete per model QPF output. Little concerned that BL and low-level moisture may become a bit displaced from the DL though, owing to the veered low-level flow.

A veered low level jet to that degree would decrease convergence along the dryline and makes it harder for storms to form. Considering the forecasted EML, that would be a fairly substantial issue. If moisture is any less than forecast, that would really throw a wrench in it.

Can't say I'm not impressed with the 12z GFS on Tuesday in the PPA-CDS-FDR corridor. Those are some pretty hellacious looking soundings with a very high degree of turning between the surface and 6 km, very low LCL heights (we'll see how moisture behaves) and a pretty classic arcing dryline configuration. Synoptically, especially at 500 mb, there appear to be quite a few similarities to significant early season High Plains events in the past with a large, slow-moving ULL generally near/just east of the Four Corners. Dryline position will probably end up being west of where the GFS depicts it, and there seems to be some concern regarding displacement of the stronger 700 mb flow away from overlapping the effective warm sector.

Oh, and there's definitely some indication of after dark problems, of which this region is no stranger to with early season events.

Rather strong signal from the 00z WRF-ARW/NMMB and NSSL WRF for an intense supercell or two INVOF the Red River right on the northern periphery of the 60s Tds. Just ahead of the trough axis on the southern periphery of the mid level cold pool (i.e. a place where it would make sense assuming at least half-decent moisture verification).

2 minutes ago, Wmsptwx said:

Tomorrow is one of those sneaky days that has definite potential to have significant severe, but a ton of variables to sort through. 

It's not really "sneaky", people have been monitoring this for awhile.

00z CRP sounding looks fairly promising regarding moisture with a 72˚F sfc Td and the moist layer to about 850 mb. Low level jet does strengthen fairly substantially through the morning hours with the emergence of the shortwave from the Four Corners. Otherwise, antecedent synoptic conditions don't exactly lend a lot of confidence with the "ceiling" scenario, would've obviously helped if the system currently over Dixie hadn't taken a southern track.

00z Euro might have enough instability for an issue in W IA/NW MO on Monday just eyeballing it. 500-1000 J/kg would probably be enough for some fast moving/low-topped cells with a tornado threat if anything can get going in that highly sheared environment on the western periphery of the LLJ. Might also be worth watching further south down the dryline towards KS/OK although better moisture would certainly be appreciated.

GFS is too fast for the former threat.

Bumping this since it is the 5 year anniversary today and I've worked on some graphics in Python to display radar loops using both Level II and III data. One below is of the New Pekin/Henryville EF4 and then the West Liberty EF3 (two deadliest tornadoes of the outbreak).

Seems like a dipole severe event is possible Tuesday with the stronger vort coming through the Four Corners + dryline and then the lead low over the Lakes/OV. Cap does look breakable further SW and if you do get backing (deeper vort leading to stronger lee cyclone/etc.), the shear profiles become rather conducive for tornadic supercells. Deep layer shear is already on the high end across basically all of the warm sector.

Really going to come down to the strength/amplification of that polar shortwave dropping out of the Pacific NW and the incorporation of the ULL that is currently driving a rex block over AK and the Aleutians. This will largely determine whether the thing ejects in pieces and gets sheared out by the confluence resulting from the SE ridge (or the fact that the northern and southern streams are out of phase). Euro has definitely been raising my eyebrows for the past few runs though although the extent of the effective warm sector shrank a bit along with the strength of the LLJ with the 12z run.

Chiclet chart earlier was hitting next week hard, with the strongest hit being Tuesday unsurprisingly.

1 hour ago, JoMo said:

Tornado hit parts of/near San Antonio it sounds like.

Quite a bit of damage via the scanner traffic, was quite a strong signature associated with the QLCS now moving towards College Station/Bryan.

Seems to be a suggestion of severe potential increasing across the central Plains towards the beginning of next week. Broad cyclonic flow looks to become anchored across the western half of the country at 500 mb with periodic shortwaves passing through the flow leading to amplification of the LLJ. Should be sufficient instability for severe wx and perhaps supercells given the lack of linear forcing.

On 8/2/2016 at 8:16 AM, ZackH said:

Looks like a day with some real potential. If we can get sufficient clearing and the NAM forecast dewpoints the environment/kinematics will be impressive. Would not be surprised if we end up with an enhanced.

Well that verified nicely.

Wednesday might an interesting day in ND and perhaps the southern Prairie provinces. Don't see too many shortwaves with 70-80 kt 500 mb jet streaks in August.

Likely a strong tornado near Portage la Prairie, MB right now moving E/ESE.

Zack, I hope you're chasing tomorrow (or at least working at the office), could be a pretty significant event.

Pretty decently sized ENH risk/30% hatched for tomorrow nearly centered on the Twin Cities. 12z WRF-ARW/NMMB were pretty bullish with a few supercells across that area in the late afternoon, perhaps tracking near the warm front and its enhanced low level SRH.

Another quality tornado (and awesome structure to boot) just E of OMA this afternoon in a MRGL risk with no tornado probs. 2016...

More like Lieowa.

I'd definitely be chasing ND on Friday if I was out there. Moderate WSW flow aloft with strong instability and a well developed southerly LLJ feeding low 70s dewpoints into the area on both the GFS and NAM. Seems a couple of impulses ejecting ahead of the main upper low could provide enough forcing for ascent for CI.

Look out near AMA: http://www.spc.noaa.gov/products/md/md0900.html

That southern stream wave ejecting this upcoming Tuesday bears watching for the southern Plains and perhaps one last kick at the can for the chasers there. The last three runs of the Euro have shown a setup that looks conducive to tornadic supercells in KS and N OK with a moderate LLJ and a respectable, sub-1000 mb surface low along with 40-50 kt 500 mb flow (the latest run also increased the instability). I am really a fan of these kinds of lower amplitude waves that tend to not force major height rises to the east and create conditions favorable for VBV profiles.

The GFS is faster and less favorable, although it appears to be a progressive outlier among the full suite and even its ensemble mean to some degree.

The Pacific jet showing up in medium range guidance sure is nice looking. As others have alluded to across various media, this could help make things rather active later on in June.

If we get at least a piece of this ejecting into a typical June warm sector, yowza.

Couple of strong LEWPs and a nasty MCV in that MCS moving across S LA right now.

4/10-11/2001. High risk on 4/11 for IL/IA, fairly prolific tornado outbreak in the Plains/Middle-Upper MS Valley.

Well, there goes the Monday system on all four model runs tonight.

I'm keeping expectations for any big synoptically-evident days low, given the uncertainties about downstream blocking. But taking the 17/12z Euro verbatim says Monday could actually be that kind of day.

If that Euro run slows 6-12 hrs and the 144 frame turns out to be more around peak heating, can't ask for much more than a potent negatively tilted shortwave with a 60+ kt southwesterly/west-southwesterly H5 jet and H85-H7 flow of 40-50+ kts this time of year.