andyhb

Quote

...Lower/Mid Mississippi Valley to the lower Ohio/Tennessee Valley region... Strong upper trough will progress across the Rockies into the Plains by 11/00z then into the mid/upper MS Valley by the end of the period as an intense 500mb speed max (100-110kt) translates into IL late. In response to this feature a surface low will deepen as it tracks from southern KS to north of CHI by 11/06z then into northern lower MI by daybreak Saturday. Severe thunderstorms are expected to develop ahead of this strongly dynamic trough. Serious consideration was given to higher severe probabilities along the MS delta region of eastern AR into the lower OH River valley. Despite the nocturnal initiation, strong tornadoes are possible with supercells Friday night.

Southwesterly LLJ is expected to increase across eastern TX/lower MS early in the period. This southerly branch of the LLJ will encourage higher-quality boundary-layer air mass to advance north into the mid MS Valley ahead of the surging cold front. Early this morning, lower 70s surface dew points are noted as far north as PSN to IER over eastern TX/LA with lower 60s dew points into central AR. There is little reason to doubt moisture will advance into MO/IL ahead of the front as capping will prevent appreciable convection until mostly after sunset. Latest model guidance suggests moisture advection/cooling profiles aloft will result in destabilization ahead of the surface low such that surface-based parcels should become buoyant by 11/02-03z across MO. There is great disparity among the latest HREF regarding timing/spatial distribution of convection during the initiation phase after sunset. Based on forecast soundings have opted to increase severe probabilities farther west across the warm sector ahead of the surface front in MO. Latest thinking is scattered supercells could develop by 03z then track northeast within a very strongly sheared environment. With thunderstorms not expected to develop until after dark diurnal heating will not contribute appreciably to buoyancy across this region. Even so, parameter space appears very favorable for supercells, and with dew points expected to rise into the lower 60s, a few strong, longer-lived tornadoes seem plausible.

They considered a moderate risk, wouldn't be surprised to see one later given the size of that 10 hatched in the newest D1.

6 minutes ago, Chicago Storm said:

Likely would be some sort of severe potential with it, just glancing at a few things.


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The 12z Euro is probably an outbreak from MO and S IL southward given verbatim.

Period around next weekend has potential (that will probably be squandered). Certainly cold air available and a substantial baroclinic zone if we do indeed get a wave ejecting around that time.

So the October measurement for the PDO via NCDC was -3.06, which is extremely strong. Last time it was that strong per that calculation was 1955 (precursor to a major drought year on the Plains).

Not sure what Mantua's calculation has, but we've clearly transitioned out of the predominantly positive phase that was present since 2013 or so.

16 hours ago, StormchaserChuck! said:

Yeah, I wonder if that warm can break 180W. It seems to me that the La Nina is dead. 

Nothing about what raindance posted suggested the La Nina is dead.

Major tornado damage being reported north of Fredericktown and in St. Mary MO.

MO maybe into W IL also looks interesting on Sunday, especially closer to the triple point/warm front.

That's a nasty looking setup for MO/IA/IL next Tuesday on the 12z GFS, big change from earlier runs.

Meanwhile the 12z Euro says nada. Not much of a trough ejection.

Already seeing a few checkmarks starting to be ticked off in terms of a fall severe wx potential early next week across recent guidance. Not sure how far north/east it will extend, but it seems there could be a chance for an anomalously large warm sector to exist ahead of whatever ejects eastward from a developing longwave trough in the west. Obviously a lot that could go wrong as with any 8+ day prog, but seeing that moisture available along with a very strong Pacific jet streak making landfall has my eyebrows perked up a bit.

Looking towards the earlier part of next week, I wouldn't be surprised if we see another elevated period of severe potential relative to climatology for the Plains and perhaps eastward. Pattern looks quite conducive to moisture return and potentially quite anomalous moisture return in front of another large scale trough developing in the west on ensemble guidance.

Also I have quite a bit of concern that Norman is going to take on its second major hailstorm in less than 6 months tomorrow. Soundings near the triple point indicate very large cloud layer shear and plenty of CAPE in the hail growth zone.

Regardless of tornado potential, I will be heading to the Wichitas tomorrow to do some hiking in the late morning/early afternoon. That would put me in great position for whatever initiates in the 21-00z window.

I still have some very bearish opinions towards Sunday as a whole, mainly from the moisture standpoint. There is not a single model that shows anywhere near the moistening/destabilization that the NAM/NAM 3 km shows, especially pre-00z. Looks to me like most convection should be nocturnal and likely quasi-linear.

Bottom continues to fall out on the sub-surface readings. This is a pretty stout cooling occurring.

3 hours ago, Iceresistance said:

The 6z GFS was absolutely crazy on Next Tuesday's Setup, Supercell Composite is up to a 9 in Western Oklahoma

That doesn't really say a whole lot about whether there will be storms and of what mode.

That is a violent tornado.

Holy mother.

That's going to be a strong tornado in the northern burbs.

I don't like the looks of that supercell near the Chester/Delaware County line.

Have seen some damage pictures out of the area that look at least EF2.

There's the Edgewater tornado, probably significant given TDS height and peak VROT of 45 kts.

70/30 probs on that new watch for E MD/PA/NJ. Pretty stout probabilities for this region.

The cell south of Charlottesville has quite a meso on it, but that central VA radar hole is being a giant pain.