Severe & Flooding Potential: May 3-6, 2015

[Quincy]

Starting today with large hail, some 2" in diameter, in a few storms from the central Plains to upper Midwest, a prolonged stretch of multiple severe weather threats is underway.

Monday, May 4th may be similar to Sunday, at least in terms of fairly spotty severe reports. With no significant forcing, near-neutral height tendencies and convective debris being a concern, it looks to be another slight risk day. There may be a somewhat enhanced, albeit still rather low, tornado threat in the vicinity of the Nebraska/Kansas border ahead of a weak surface low. Otherwise, isolated to widely scattered severe storms will be possible from the southern High Plains to central Plains and Midwest.

Tuesday, May 5th looks like another similar setup, at least in terms of only yielding spotty severe storms. Some subtle height falls are expected as we shift into a pattern characterized by eastern U.S. ridging and a digging trough across the West with two pieces of energy. The more prominent of which will be hanging back across the Pacific Northwest on Tuesday with a small piece ejecting eastward from the Four Corners region. The Texas/Oklahoma panhandles and far eastern New Mexico may be the spots to watch here for severe thunderstorm development.

Wednesday, May 6th has fairly unanimous support as being the potential biggest day of the set. Shortwave energy pivots east while an elongated low develops along the central to northern High Plains. While over-abundant moisture is a concern, the focus appears to be from north Texas to Oklahoma and Kansas. All severe threats appear possible, but the extent of destabilization and a lack of stronger flow aloft will probably be limiting factors.

(Moved to new thread)Thursday, May 7th holds some potential, but largely hinges on the speed and evolution of the system leading up to this point. Still, the models seem to be somewhat bullish on instability ahead of a cold front/dryline and anywhere from the Plains to the upper Midwest could get in on some action here.

If clouds and convective debris/overturning win out, flooding may ultimately be the biggest story here with a fairly widespread swath of 2-4"+ rains likely through the week across much of the central and southern Plains.

Beyond this, another severe threat may develop this weekend across the center of the country as the western trough continues to dig and push energy into the Plains. After a dull five day stretch, severe weather threats appear to be on the rise in the coming several days.

[Chinook]

Tomorrow:(5/4) the 4km NAM shows some activity around the northern Kansas/southern Nebraska/central Iowa area. It probably won't be too interesting from a tornado-chasing standpoint. The 30kt-40kt 0-6km shear values will be north (in Nebraska) of the higher CAPE values, which will be in Kansas, and western Missouri. Still, though, Kansas seems to be able to pull off some hail/wind in these situations. The convection may keep going into the night, with higher precip amounts highlighted in Iowa and northwest Illinois. SPC will most likely keep this at a slight risk, or maybe even bump it up to an enhanced risk.

[andyhb]

18z GFS looks fairly solid for Wed, low level shear is pretty darn impressive by 00z and there is better upper level flow on the northern periphery of the incoming upper jet near the KS/OK border and into NW OK. Despite the weaker upper winds, the KS/NE border and north central KS region seems to also warrant attention.

[jhamps10]

 

HPC 7-day QPF forecast dated late afternoon 5/4/2015

 

Flooding may end up being the big story here over severe weather

[Quincy]

Thunderstorms sort of training across portions of northeastern Kansas. Flash Flood Warning for Manhattan where 1.20" fell in the last hour alone and plenty more is on the way. No doubt that some areas could pick up over 5" of rain by Thursday.

[rolltide_130]

Some really good structure on that storm in SW Texas.

[Chinook]

Up to 4.15" at Manhattan KS as of recently (spotter report). That's quite a rainy day.

[Quincy]

Up to 4.15" at Manhattan KS as of recently (spotter report). That's quite a rainy day.

Pretty impressive pictures coming out from there. Some cars just about completely submerged under water in town.

[andyhb]

Pretty impressive pictures coming out from there. Some cars just about completely submerged under water in town.

 

Area south of Lubbock reported 8".

[Chinook]

Lubbock NWS tweeted:

 

The highest rainfall report so far has been 9.10" by our COOP observer in Tahoka.

[andyhb]

Roger Hill and co. just caught a very nice tornado that was down for ~15 min near Big Spring, TX.

[jhamps10]

Roger Hill and co. just caught a very nice tornado that was down for ~15 min near Big Spring, TX.

 

and got the weather channel to go gang busters over it too... brilliant when the only thing in it's path is tumbleweeds and wind turbines

[rolltide_130]

Roger Hill and co. just caught a very nice tornado that was down for ~15 min near Big Spring, TX.

Might get some nice pictures out of there later. He's one of the better photographers in the business IMO.

[Ian]

Sullivan got a pic of the year type shot. https://twitter.com/btsullivan91/status/595706210386579456

Too bad he's so annoying.

[David Reimer]

Sullivan got a pic of the year type shot. https://twitter.com/btsullivan91/status/595706210386579456

Too bad he's so annoying.

I'm surprised AccuWeather hasn't plastered it everywhere. Stupid early afternoon mini-supercell. 

[andyhb]

I'm surprised AccuWeather hasn't plastered it everywhere. Stupid early afternoon mini-supercell. 

 

Blame the outflow boundary that the storm clearly interacted with.

[David Reimer]

Blame the outflow boundary that the storm clearly interacted with.

 

Stupid sleeper days. Can you tell I'm a bit bitter about choosing to sit today out? Tomorrow looks quite interesting in Oklahoma. It's nice to see a continuation of the strong afternoon low level jet. I've chased too many setups since 2012 with marginal low level wind profiles. That won't be the case tomorrow. 

[Ian]

I'm surprised AccuWeather hasn't plastered it everywhere. Stupid early afternoon mini-supercell.

Great play by those who saw it. Unusual to get so early.. Must have been paying attention at least. Quality half accidents are often the best.

Low levels are really nice tomorrow for sure. Rising heights and weaker flow aloft not to mention early passage of shortwave are all questions but I haven't looked much closer than that. Good to see some real May showing up one way or another.

[jm1220]

Torrential slow moving storm here in Austin right now. Flood advisory in effect for 2-3" of rain. 

[1900hurricane]

The Travis County storm has caught my eye too. While the core of the heaviest rains may be very slowly progressing to the north and east, backbuilding has been occurring constantly across the heart of the county over and just west of Austin, right on the spine of the Balconies Escarpment. Moderate KDP, high CC, low Echo Tops, and low VIL all point to warm rain processes at play, and rain totals look to be adding up quite quickly. I wouldn't be surprised to hear things getting hairy over there pretty soon.

[jm1220]

3.25" at Camp Mabry now near downtown and more heavy rain building to the south. I'm on the southwest side of town and haven't seen that much rain but I'm in a heavy patch now. Again, much less on the east side but this new batch of rain is hitting areas further east. 

[1900hurricane]

 

MESOSCALE PRECIPITATION DISCUSSION 0055
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1054 PM EDT TUE MAY 05 2015

AREAS AFFECTED...CENTRAL TX

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 060253Z - 060653Z

...SUMMARY...

THERE IS AN INCREASING THREAT FOR FLASH FLOODING TO DEVELOP AND
INCREASE IN AREAL COVERAGE INTO THE OVERNIGHT HOURS.

...DISCUSSION...

CONCERN IS THAT HEAVY RAIN-PRODUCING CONVECTION WILL BECOME BETTER
ORGANIZED THROUGH THE LATE EVENING HOURS AND EARLY MORNING HOURS
AS 850 MB FLOW INCREASES TO BETWEEN 30 AND 35 KTS AT THE SAME TIME
A MID LEVEL TROF APPROACHES FROM THE WEST. INSTABILITY ON THE
ORDER OF 1500 TO 2000 J PER KG IS POISED UPSTREAM AND SHOULD BE
DRAWN INTO CENTRAL TX AT ABOUT THE SAME TIME THAT 700 MB OMEGA IS
MAXIMIZED. THE 00Z SOUNDING FROM CPR ALREADY INDICATED A DEEP
SATURATED LAYER IN PLACE TO THE REGION. THE TREND OF THE LAST 3
HRRR RUNS HAS BEEN TO FOCUS A QPF MAXIMUM BETWEEN 03Z AND 0730Z
ALONG A LINE FROM EAST OF TPL TO WEST OF PSN.

THE AREAL COVERAGE OF THE MPD WAS PULLED SOUTH OF THAT LINE TO
COVER THE POSSIBILITY OF ADDITIONAL HEAVY-RAIN PRODUCING
CONVECTION FORMING IN THE MOISTURE RICH INFLOW REGION.

ADDITIONAL RAINFALL AMOUNTS OF 2 TO LOCALLY 4 INCHES ARE POSSIBLE.

BANN

ATTN...WFO...EWX...FWD...HGX...SJT...

ATTN...RFC...WGRFC...

LAT...LON 32029717 31809595 31029553 29629618 29069789
29489885 31129847 

[andyhb]

Probably would sit somewhere just south of the KS/OK border west of I-35 this afternoon/evening. Initiation is questionable, but you won't have as many of the upper level wind/venting issues as you do further north into KS, and low level shear across all guidance still appears very favorable for tornadoes should a storm or two sustain itself. Convection/WAA precip early this morning seems to have cleared this area nicely.

 

Couple of screenshots I took earlier of the Big Springs, TX tornado (from Roger Hill's stream).

 

 

[David Reimer]

The 06Z NAM is suggesting an early show possibility like yesterday in Southwest Oklahoma and Northwest Texas around Wichita Falls. It suggests storms will fire up around 20Z in an environment with a 1KM EHI of 4.5. Something to watch just in case we end up with an early little teaser once again. Otherwise I can attest first hand the storms rolling through C. OK this morning have plenty of water with them. 

[Quincy]

Kind of an odd day today. Pros and cons in both directions and there seem to be two camps in play for storm potential. I am leaning a bit more toward the setup not really panning out, but all it takes is one storm and I would rather not miss out again like yesterday.

Northern target of north-central Kansas seems somewhat less favorable overall. While the convection-allowing models, particularly the HRRR, favor some semi-discrete and potentially strong convection up here, the thermodynamic environment is less impressive than further south. There's also the fact that some ongoing convection this morning could overturn things a bit. Upper level winds are fairly weak. Although that area is closer to the shortwave energy, even that is already moving through, thus out of sync with timing.

Southern target of south-central Kansas into western Oklahoma looks to become moderately to strongly unstable. Upper level winds are a bit stronger and they will be just ahead of where a weak surface low should develop. Conditions have already been clearing out here, so that should further assist in the destabilization process. The models vary, with the fire nest NAM showing a broken line of storms in central to south-central Kansas with the southern cell perhaps becoming most dominant. The HRRR doesn't seem to want to fire much of anything on the dryline.

Storm coverage should remain fairly isolated, so if any storms do fire, they may be able to remain fairly discrete for a while. Wind shear is favorable for supercell development and the wind profiles could support a tornado or two. I guess we'll look keep an eye on weak surface cyclogenesis near the southern CO/KS border for more clues. I wonder if SPC will maintain a fairly broad area of 5% tornado probs for 13z or narrow the focus a bit.

[nrgjeff]

Outflow boundaries OFB are noted in both southern Kansas and southern Oklahoma. Agree with Quincy that shear is better south. If the southern Oklahoma OFB can stay down there, without lifting north, it would be under better upper level jet stream winds and only giving up a little LLJ. All those stable looking clouds in Oklahoma could be a good thing if that southern OFB is not surging north. Although a north move could be even money per LLJ. My main point is to keep an eye on the southern most OFB or differential heating boundary. Be safe and good luck!

[Quincy]

I have my eyes between DDC and ICT. The area from the OK/KS border up to just about I-70. Skies starting to clear out now and a mighty decent overlay of parameters projected later on. It's not the best setup, but I expect at least a couple of tornadoes in KS. There are questions about initiation in western OK, but I could see a storm or two down by the Red River and slightly further south into Texas. Down there, there could be 3000-4000 J/kg of CAPE, so plenty of fuel.

[brettjrob]

A large majority of convection allowing models are showing isolated to scattered supercells through central KS and OK by 00z this evening. The only real weakness in the background environment is questionable flow aloft, mainly around H5 down south and H2-H3 up north. I'm very surprised at the lack of enthusiasm in the weather and chasing world today. It seems highly probable that at least one or two storms will initiate in a high-end environment; as the previous SWODY1 said, any sustained storm would be associated with a very real SigTor threat, even before 00z. I think we'll have several tornado reports by 8-9pm, and wouldn't be shocked if it were more than several. We shall see -- I'm very optimistic about this week as a whole, and seem to be an outlier among chasers/forecasters for now.

[andyhb]

We shall see -- I'm very optimistic about this week as a whole, and seem to be an outlier among chasers/forecasters for now.

 

You're an outlier of yourself currently, heh.

 

Edit: Double enhanced risk added in latest D1.

[yoda]