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Quincy

Short-Term Severe/Flooding Discussion

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I figured a threat like this would be helpful for filling in the gaps between larger events, particularly when small-scale threats may pop up. Aka, sleeper days. Also with the heavy rainfall over the past few weeks, we could lump some flooding discussion in here too.

 

Thursday appears to have some potential, even if it is over a rather focused part of western Texas along the dryline. I've been watching the models trends over the past couple of runs and there seems to be at least a marginal threat developing. There's a perturbation/vorticity maximum forecast to swing from eastern NM into western TX Thursday evening. At the surface, modest heating is projected to result in at least 1000-2000 J/kg SBCAPE. 0-6km shear appears to be around 30 knots, which is modest, but probably enough for at least some supercell potential. While the mid and upper level winds look rather weak, an increasing LLJ and backing winds by late-day may aid in developing a small tornado window around 00-03z Friday. The NAM/RGEM appeared more favorable than the GFS here, but even the GFS isn't that far off. The GFS shear values are slightly lower though. 

 

As far as today is concerned, more locally heavy rain has fallen across much of the southern Plains. Most of that was along or east of I-35 by mid-afternoon. Some strong to isolated severe thunderstorms are forming to the west. 

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Smokey-

Stop posting. You add nothing of value and no one has ever responded to your comments. Just follow along and look for pertinent info for your area to stay aware as many other people do.

Hopefully your precious soccer games don't get rained out

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Well thankfully we didn't get the monsoon called for entirely today none the less some hefty rain here for a bit though so that should help with flood waters easing on the rivers. Still concerned about this weekend especially if we get training storms and a bunch of boundaries everywhere.

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You worried about flooding or severe weather?

More flooding than anything as I'm not so sure about the severe weather aspect as I'm not that great reading model data, let alone trusting them this year. I think we could see a bit of both, last weekend we had our surprises and could very well see that happen again depending on how overnight convection goes. Instability and moisture will certainly be there along with the dynamics.

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Nebraska and Kansas are about 1/2 filled with light rain. It's just amazing how many rain events have happened on the plains. Maybe we could even get rid of some of the drought in Minnesota.

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Convection is firing from SE New Mexico into the Trans Pecos region of Texas. Driven by some subtle forcing aloft. The surface winds remain rather backed at SSE to SE near and just north of I-20 west of Abilene. There's actually been moderate destabilization with >2000 J/kg MLCAPE. Stronger shear is moving in, as its marginal at best at the moment. The main threat appears to be large hail, as LCLs are still rather high and the boundary layer flow is meager. However, as the low-level jet ramps up by late afternoon/early evening, there could be some isolated tornado potential, particularly with any discrete cells in vicinity of a mesolow/locally backed surface winds.

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Pretty spectacular sounding from AMA @ 00z Wed from the 12z NAM (with supercells in the area as well). Will start a thread on this later if some consistency is shown.

 

Screen+Shot+2015-05-17+at+12.23.14+PM.pn

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Interesting data for my town.

 

13.84" of rain for the month of May in Fort Smith as of 7am.

That is a NEW RECORD for most rain during the month of May on record. Wow..

 

 

If we get 3.80" more, it will be the wettest spring ever recorded since record keeping began back in 1883.

https://www.facebook.com/pages/Garrett-Lewis/288279856331

https://www.facebook.com/5NEWSJoe

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National Weather Service Forecast Discussion today talking about the potential for catastrophic flooding in SE Oklahoma and West Central Arkansas if the heaviest rain this weekend occurs along and south of I40.

If you live in this area, pay close attention to the forecast in the coming days, especially if you'll be outdoors for the Memorial Day holiday in the Ouachitas where flash flooding can literally occur in less than an hour in valleys.

Another 3-5" on top of the recent rainfall will cause major river flooding and many roads could become impassable.

Too early to know right now, and the models are actually shifting the heaviest axis closer to Northwest Arkansas which didn't see the super heavy rain last night but don't let your guard down from Sallisaw to Fort Smith to Clarksville and south to Waldron, Poteau, & Talihina. It could get really bad if the heaviest rain this weekend falls in these places.

https://www.facebook.com/pages/Garrett-Lewis/288279856331

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GFS/NAM are focused on a big time soaking for south central TX-one big round late Sat into Sun, then another Monday night. We have a lot more capacity for excess rain than N TX/OK, but 6"+ rain over this period would still cause some major problems and flash floods on the creeks that flow through much of Austin. There's also a severe risk with the late Saturday/Sun event due to the trough digging pretty far south and the potential for supercells/tornadoes if there can be any clearing during the day tomorrow.

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12Z NAM (6/10) expands Thursday area of interest south to the KS/OK border. We'll see what SPC thinks in about an hour. Friday looks like SLGT not MRGL, but we'll see. GFS concurs on wind fields but not qpf; I tend to favor hi-res NAM for qpf.

 

Thursday still looks ok in Iowa but storm mode and ongoing rain will be challenges. Shortwave timing is also an issue, but low level turning should remain near OFBs.

 

Now appears new shortwave ejects into High Plains in time Thursday afternoon, with no midday rain. Cap may hold in the TX Panhandle. Hailers may develop but a hot 700 mb looks to kill them shortly after 00Z. Meanwhile DL and SF intersect in southwest Kansas, under slightly less of a cap. Synoptic front must act as stationary or warm; a CF surge would destroy that set-up. Low level shear is less than ideal, but looks like 50kt+ upstairs. Could a boundary intersection get the job done?

 

Friday looks complicated. Upper shear relaxes a bit, but an upper low sits over CO/NM. One would expect downstream agitation in the Panhandles. CF surge remains a risk; however, low press appears to promote better low level wind backing. It is the Panhandle in June.

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Friday looks complicated. Upper shear relaxes a bit, but an upper low sits over CO/NM. One would expect downstream agitation in the Panhandles. CF surge remains a risk; however, low press appears to promote better low level wind backing. It is the Panhandle in June.

Despite the wind fields aloft not being terribly impressive, low-level shear and instability (via NAM) look strong enough to support some supercells, if storms can remain discrete.

New 12z analog guidance showed at least 50% of similar setups produced one or more tornadoes in the Texas panhandle. The threat would probably extend east into western Oklahoma if the latest data is correct. FWIW, the analog guidance would suggest a SLGT to ENH risk.

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Several storms are developing in the tornado watch area now. They all seem fairly ordinary, though.

20Z SPC D1SWO added a small ten percent TOR prob across the watch area.

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HRRR is advertising a relatively long squall line in TX and OK.

Looks like an initial risk for severe storms in western Texas quickly transitioning to more of a flash flood/damaging wind threat after dark via MCS.

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