Severe threat: srn Plains states + IA / MO May 7-9

[Ground Scouring]

Now that model agreement among the GFS ensembles, the GFS operational, the ECMWF, and the ECMWF ensembles are coming into more general agreement re: the timing of our next severe threat, I've decided to start a thread. For starters, models are keying in on a general re-loading pattern over the next five to six days with a +PNA giving way to a -PNA and a broad Western trough setting up. At the same time the MJO is forecast to be in or entering into a weak Phase 1 state over the Atlantic and W Africa with little real change in the -NAO state. Models are showing a high-quality warm sector setting up over the srn Plains by days four and five with a Sonoran EML overspreading nrn TX, OK, and KS. By day five broad lee cyclogenesis is forecast to occur east of the Rockies, with a broad southerly return flow advecting a seasonably moist air mass north. While there are capping issues to contend with, especially with the positively tilted trough forecast to set up, overall the set-up would support about a three-day period for convection beginning perhaps with initation along the dryline as early as day four. Given relatively weak deep-layer shear the threat for tornadoes and severe wx generally is likely to be fairly localized, which could either be a bane or a boon to chasers depending on how the mesoscale sets up. Still, it's better than nothing!

 

SPC seems interested:

 

AS A WRN U.S. UPPER TROUGH EVOLVES/DEEPENS THROUGH EARLY NEXT
WEEK...SEVERE RISK WILL REMAIN LOW. HOWEVER...WITH HIGH-PLAINS LOW
PRESSURE EVOLVING AHEAD OF THE TROUGH THUS SUPPORTING WIDESPREAD SLY
LOW-LEVEL FLOW INTO THE CENTRAL CONUS...STEADILY MODIFYING GULF AIR
WILL CONTINUE BEING ADVECTED NWD THROUGH MIDWEEK. BY THE WED-FRI
TIME PERIOD /DAYS 6-8/...INCREASINGLY WIDESPREAD MODERATE CAPE
SHOULD BE AVAILABLE ACROSS A LARGE PORTION OF THE CENTRAL THIRD OF
THE COUNTRY...THUS SUPPORTING AN INCREASE IN SEVERE POTENTIAL.

WITH THAT BEING SAID HOWEVER...MAJOR MODEL DIFFERENCES PERSIST WITH
RESPECT TO EVOLUTION OF WRN U.S. UPPER TROUGHING. WHILE THE GFS
ADVANCES A LARGE TROUGH -- COMPRISED OF PHASED NRN- AND SRN-STREAM
SYSTEMS -- EWD INTO THE PLAINS THROUGH THE LATTER HALF OF THE
PERIOD...THE ECMWF DEPICTS A SIMILARLY-TIMED NRN STREAM TROUGH
ADVANCE INTO THE NRN PLAINS BUT A STATIONARY -- OR EVEN RETROGRADING
-- SRN-STREAM PORTION OF THE TROUGH. WITH SUBSTANTIAL VARIATIONS
ALSO THEREFORE MANIFEST IN THE SURFACE PATTERN ACROSS THE PLAINS
VICINITY...TEMPORALLY AND SPATIALLY DELINEATING RISK AREAS REMAINS
DIFFICULT ATTM. HOWEVER...AS UNCERTAINTY DIMINISHES WITH TIME AND
RISK AREAS BECOME MORE CLEAR...EXPECT SEVERE WEATHER PROBABILITY
AREAS TO BE INTRODUCED IN LATER FORECASTS ACROSS PORTIONS OF THE
PLAINS STATES AND VICINITY.

[nrgjeff]

I concur. Started a thread over in Tennessee Valley since I think it could end as a Mid South Mauler. The Plains: 12Z Euro just out has the DL going Wednesday. GFS seemed to do better last time delaying a day, which is does again this time, so maybe Thursday. When the 68-70 dews arrive without mixing out the DL will go. Dews will be directly related to upper jet poking out and LLJ picking up - all tied together. From late week through the weekend both models have a lot of overnight and morning convection. However in May one has to believe the pattern would promote afternoon redevelopment. Too early for even broad target states and days, but a sequence is possible from the southern Plains to the Mid South.

[PGM]

Day 6 severe risk issued for Chicago - Kansas City - Oklahoma City.

 

 DAY 4-8 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0400 AM CDT SAT MAY 03 2014   VALID 061200Z - 111200Z   ...DISCUSSION...   DETERMINISTIC MEDIUM-RANGE MODELS /PRIMARILY THE GFS AND ECMWF/ HAVE   COME INTO SOMEWHAT CLOSER AGREEMENT WITH RESPECT TO EVOLUTION OF THE   WRN U.S. UPPER TROUGH AS IT EJECTS EWD INTO THE CENTRAL CONUS   THROUGH THE MIDDLE OF NEXT WEEK.  STILL HOWEVER...DIFFERENCES WHICH   PERSIST -- PARTICULARLY FROM ROUGHLY DAY 6 ONWARD -- ARE EVEN MORE   PRONOUNCED WITHIN MREF ENSEMBLE MEMBERS.  AS A RESULT OF THESE   FACTORS...OVERALL PREDICTABILITY CONCERNS LINGER WITH THE   LARGE-SCALE PATTERN.   WITH THAT BEING SAID...ENOUGH SIMILARITY BETWEEN THE GFS AND ECMWF   EXISTS THROUGH DAY 6 SUCH THAT A FORECAST OF CONVECTIVE POTENTIAL   WITH A REASONABLE LEVEL OF CONFIDENCE CAN BE MADE.  ATTM...IT   APPEARS THAT A SURFACE LOW WILL LINGER OVER THE CENTRAL HIGH PLAINS   THROUGH MIDWEEK /I.E. DAYS 4-5/...WHILE PARTIALLY MODIFIED GULF   MOISTURE SPREADS NWD.  THE DEGREE OF MOISTENING HOWEVER APPEARS   UNLIKELY TO BE SUFFICIENT -- GIVEN WARMTH OF THE EML ABOVE THE   BOUNDARY LAYER AND LACK OF STRONG SYNOPTIC-SCALE UVV -- TO SUPPORT   ANY MORE THAN ISOLATED AFTERNOON WARM-SECTOR CONVECTION.    INSTEAD...MUCH OF THE CONVECTION WILL REMAIN ELEVATED WITHIN A   WARM-ADVECTION ZONE NORTH OF THE WARM FRONT -- I.E. ACROSS THE UPPER   MIDWEST/UPPER MS VALLEY/UPPER GREAT LAKES REGION.  WHILE SOME RISK   FOR LARGE HAIL MAY EXIST...RISK DOES NOT APPEAR TO WARRANT AREAL   INCLUSION ATTM.   AS MODELS BRING THE UPPER TROUGH EWD INTO THE PLAINS DAY 6 /THU 5-8/   HOWEVER...MORE COMPLETELY MODIFIED GULF MOISTURE APPEARS LIKELY TO   HAVE SPREAD INTO THE CENTRAL U.S. PERMITTING DEVELOPMENT OF MORE   SUBSTANTIAL CAPE.  AS THE SURFACE LOW SHIFTS NEWD ALLOWING A   TRAILING FRONTAL ADVANCE ACROSS THE CENTRAL PLAINS   VICINITY...DEVELOPMENT OF AFTERNOON SURFACE-BASED STORMS APPEARS   LIKELY.  WITH THE GREATEST JUXTAPOSITION OF FAVORABLE SHEAR AND   MODERATE CAPE LIKELY TO EXIST FROM ROUGHLY OK NEWD ACROSS KS/MO/IA   AND INTO IL AND SRN WI...IT APPEARS THAT INCLUSION OF A 30   PERCENT-EQUIVALENT RISK AREA CAN BE INTRODUCED ATTM WITH MODERATE   CONFIDENCE...WITH HAIL/DAMAGING WINDS LIKELY ALONG WITH SOME TORNADO   POTENTIAL.   BEYOND DAY 6...DIFFERENCES IN THE MODELS ARE SIGNIFICANT ENOUGH TO   PRECLUDE CONFIDENT ASSESSMENT OF CONVECTIVE POTENTIAL.   ..GOSS.. 05/03/2014

[Ground Scouring]

One place to look for tornado potential might be in IA on the afternoon of May 7. Deep-layer shear, according to the GFS, is projected to be stronger up there than in OK and the cap should be less pronounced. Mid-level lapse rates might also be steeper as a result of the reduced capping and moderate to strong instability of 3,000+ j/kg SBCAPE over much of IA (correct me if my interpretation or meteorology is wrong). Synoptically the set-up is a bit similar to that which produced the Parkersburg tornado on 05/25/2008.

[thewxmann]

One place to look for tornado potential might be in IA on the afternoon of May 7. Deep-layer shear, according to the GFS, is projected to be stronger up there than in OK and the cap should be less pronounced. Mid-level lapse rates might also be steeper as a result of the reduced capping and moderate to strong instability of 3,000+ j/kg SBCAPE over much of IA (correct me if my interpretation or meteorology is wrong). Synoptically the set-up is a bit similar to that which produced the Parkersburg tornado on 05/25/2008.

 

Eh, it's not that similar. There was a mobile shortwave impinging on MN/IA on 5/25/08. Here we just have a lumbering positive tilt trough.

 

If the GFS is right, May 8 has much bigger potential, but I would hesitate to say any more than that because the less progressive Euro solution would suggest a lesser threat.

[jojo762]

None of the days look all that impressive to be basing off of the GFS... However, may 8th does look potentially interesting given, sufficient shear, somewhat locally backed winds, moderate instability, ~70kt 500mb jet over the warm sector... But will have to see more consistency with this to be more impressed. As it looks now basing off of the 12z GFS I'd go with Large hail, damaging winds, and isolated tornadoes. Of course the tornado threat would depend on storm mode as well.

[brettjrob]

It's tough to get a big trough in May without Plains tornadoes, but this one is just sloppy, as some semblance of split flow continues next week. Northwest flow, albeit weak, dominates the GOM over the whole period, probably harming moisture quality to some degree.

Wednesday looks nice synoptically, but the timing is 6-12 hours out of phase again -- what can you do but laugh, anymore? Thursday clearly has the best potential for widespread storms, and the 12z GFS verbatim would suggest quite a favorable environment over the eastern Plains, but minor timing differences could squash that considerably.

At least both the GFS and Euro keep some southern stream energy in the SW late next week, with potentially some widespread rains over the S Plains.

[jojo762]

It's tough to get a big trough in May without Plains tornadoes, but this one is just sloppy, as some semblance of split flow continues next week. Northwest flow, albeit weak, dominates the GOM over the whole period, probably harming moisture quality to some degree.

Wednesday looks nice synoptically, but the timing is 6-12 hours out of phase again -- what can you do but laugh, anymore? Thursday clearly has the best potential for widespread storms, and the 12z GFS verbatim would suggest quite a favorable environment over the eastern Plains, but minor timing differences could squash that considerably.

At least both the GFS and Euro keep some southern stream energy in the SW late next week, with potentially some widespread rains over the S Plains.

Agree... I can't stand positive-tilt troughs at all either, they also lead to tons of capping, and tend to be late occasionally in getting over the warm sector. Moisture return does not appear to be a big issue for Thursday, and that has been the catalyst so far this year, will be interesting to see how that turns out seeing as to how models have over done moisture return a lot this year, but indeed Thursday does look interesting, if more instability were to develop then currently progged it could be pretty explosive IMO, lack of impressive shear speed could be a potential tornado-limiting factor though, albeit the wind-profile is at least somewhat favorable for tornadoes basing off of the 12z GFS. Haven't seen the EURO at all though...

[Ground Scouring]

Eh, it's not that similar. There was a mobile shortwave impinging on MN/IA on 5/25/08. Here we just have a lumbering positive tilt trough.

 

If the GFS is right, May 8 has much bigger potential, but I would hesitate to say any more than that because the less progressive Euro solution would suggest a lesser threat.

I'm not even sure that May 8 would necessarily be bigger based on the GFS…as the GFS initiates widespread convection overnight May 7-8 that continues through the early afternoon across the warm sector in OK and N TX. Ad verbatim, the run would suggest that the air mass would be so saturated that even afternoon recovery in May would not be enough to increase the threat. The erosion of the cap is poorly timed on the 12Z operational run even though deep-layer shear is oriented nearly perpendicular to the dryline. For that and other reasons, May 7, to me, looks better, particularly in IA rather than the srn Plains, if only convection can get going. But again, this will change as models continue to hone in on timing.

[tornadotony]

Eh, it's not that similar. There was a mobile shortwave impinging on MN/IA on 5/25/08. Here we just have a lumbering positive tilt trough.

 

If the GFS is right, May 8 has much bigger potential, but I would hesitate to say any more than that because the less progressive Euro solution would suggest a lesser threat.

The Euro nailed last week's tornado outbreak, but I get a little nervous with it when it's the less progressive solution.  From time to time, it has a tendency to amplify too much, especially over the desert SW.

[tornadotony]

I'm not even sure that May 8 would necessarily be bigger based on the GFS…as the GFS initiates widespread convection overnight May 7-8 that continues through the early afternoon across the warm sector in OK and N TX. Ad verbatim, the run would suggest that the air mass would be so saturated that even afternoon recovery in May would not be enough to increase the threat. The erosion of the cap is poorly timed on the 12Z operational run even though deep-layer shear is oriented nearly perpendicular to the dryline. For that and other reasons, May 7, to me, looks better, particularly in IA rather than the srn Plains, if only convection can get going. But again, this will change as models continue to hone in on timing.

lol wut

 

 

(That's for 00z Thursday evening on I-35 at the KS/OK border, FYI.)

[andyhb]

It's tough to get a big trough in May without Plains tornadoes, but this one is just sloppy, as some semblance of split flow continues next week. Northwest flow, albeit weak, dominates the GOM over the whole period, probably harming moisture quality to some degree.

Wednesday looks nice synoptically, but the timing is 6-12 hours out of phase again -- what can you do but laugh, anymore? Thursday clearly has the best potential for widespread storms, and the 12z GFS verbatim would suggest quite a favorable environment over the eastern Plains, but minor timing differences could squash that considerably.

At least both the GFS and Euro keep some southern stream energy in the SW late next week, with potentially some widespread rains over the S Plains.

 

Both the 12z GFS and Euro don't look nearly as bad in terms of splitting the trough. While obviously previous events won't prevent that from happening, it's of note that we have had a number of solid synoptic trough ejections that avoided this same fate this year, something that a year like 2012 could only dream of.

[tornadotony]

Both the 12z GFS and Euro don't look nearly as bad in terms of splitting the trough. While obviously previous events won't prevent that from happening, it's of note that we have had a number of solid synoptic trough ejections that avoided this same fate this year, something that a year like 2012 could only dream of.

Yeah huge change in the 12z Euro from its previous runs.  I'd wait for a bit more run-to-run consistency, but I believe it's likely that we're not going to see a closed low over the desert SW with this system.

[andyhb]

Both runs would appear to suggest that Thursday might be the day in the Southern Plains with the main trough ejection.

[jojo762]

If the 18z and 00z runs of both the EURO and GFS remain consistent with the 12z runs, I wouldn't be surprised to see the SPC start to mention a potentially more significant/substantial SVR threat for Thursday, just my opinion though... Looks to have decent potential, of course models have only recently started to show a potentially bigger day for Thursday, previous runs were bleh to say the least...

[andyhb]

The 18z GFS continues to indicate (despite the positive tilt trough overall) a strong ejecting speed/vort max on Thursday with a rather broad axis of moisture/instability developing to the east of the dryline. In addition to that, the LLJ ramps up to ~50 kts and the surface winds back significantly through the day in response to secondary surface cyclogenesis.

 

Previous convection/mesoscale/timing issues aside, it is a bit concerning to see the locations that look to be under threat here if this idea becomes more prevalent.

[Stebo]

Yeah huge change in the 12z Euro from its previous runs.  I'd wait for a bit more run-to-run consistency, but I believe it's likely that we're not going to see a closed low over the desert SW with this system.

Completely agree with you on this.

[Ground Scouring]

The 00Z GFS that's just coming out is still about 12 hours slower than the 12Z ECMWF and its ensembles are, but the pattern emerging is much more similar to that of the ECMWF--namely, a complete abandonment of the cutoff low solution, instead showing a consolidated (northern) shortwave trough ejecting over the Plains states on May 8. Moreover, the trough is much less positively tilted, meaning fewer problems with capping, making robust convection along a wide swath of the dryline from OK to IA possible. The possibility of a strung-out solution with possible low-level veering at times (at least until the secondary low develops and cranks up the low-level SRH) makes the mesoscale forecast very tricky and dependent on timing. While low-level shear may increase after sundown in OK late on May 8, rising heights behind the shortwave could lead to unfavorable low-level subsidence over the warm sector and/or a squashed-low scenario. Forecasting whether the best low-level shear will coincide with daytime heating / instability is potentially nightmarish in this case. However, with a broad warm sector likely to be in place the potential ceiling for a localized severe event is high, but whether it will be based to the north (in nrn MO and IA) or to the south (OK and N TX / Red River valley) is still a big question mark.

[andyhb]

First look at the 00z Euro for Thursday looks pretty darn troubling for the Central Plains into the Midwest, what an intense LLJ (50-60+ kts over a large area) for May with a broad longwave trough and powerful H5 vort ejecting towards the area and a mid 990s surface low near MSP. Let's just say that this verbatim would be no isolated event (assuming previous/leftover convection doesn't completely take over). Also looks to be some potential on Wednesday further SW although it might be a bit slow (sorry Brett) despite really textbook surface low placement and a rapidly developing LLJ towards 00z.

 

How far we have come in 24 hrs to say the least.

[jcwxguy]

 

 

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0400 AM CDT SUN MAY 04 2014

VALID 071200Z - 121200Z

...DISCUSSION...

MEDIUM-RANGE MODELS HAVE CONTINUED OVER THE PAST SEVERAL RUNS TO

COME INTO BETTER AGREEMENT WITH DEPICTION OF THE UPPER TROUGH

ADVANCE INTO THE CENTRAL U.S. DAYS 4-5 /I.E. WED.-THU./...WITH THE

GFS AND ECMWF NOW SHOWING STRONG SIMILARITY THROUGH DAY 5 BUT

DIVERGING GRADUALLY THEREAFTER.

BOTH MODELS ADVANCE A LONGITUDINALLY EXTENSIVE WRN TROUGH TO ROUGHLY

THE FRONT RANGE OF THE ROCKIES BY THE END OF DAY 4. WITH THE

EVOLVING PLAINS WARM SECTOR LIKELY TO REMAIN GENERALLY CAPPED

THROUGH THE AFTERNOON/EVENING OF DAY 4...MOST DEEP CONVECTIVE

ACTIVITY SHOULD REMAIN TO THE COOL SIDE OF THE WARM FRONT...AND THUS

SEVERE RISK SHOULD REMAIN LIMITED.

DAY 5....BOTH MODELS DEPICT A SHUNTING OF THE MOST ENERGETIC PORTION

OF THE UPPER TROUGH QUICKLY NEWD ACROSS THE CENTRAL PLAINS AND

EVENTUALLY THE UPPER MS VALLEY...AS IT IMPINGES ON A FAIRLY STOUT

ERN U.S. RIDGE. AS SUCH...A SIMILAR NEWD ACCELERATION OF A

DEEPENING SURFACE LOW...FROM ITS INITIAL POSITION OVER THE CENTRAL

PLAINS TO THE LK SUPERIOR VICINITY LATE IN THE PERIOD...IS EXPECTED.

AS THIS OCCURS...EWD ADVANCE OF A COLD FRONT ACROSS A

THERMODYNAMICALLY UNSTABLE WARM SECTOR WILL YIELD WIDESPREAD

WARM-SECTOR THUNDERSTORM DEVELOPMENT.

A COMPLICATING FACTOR WITH RESPECT TO EVOLUTION OF SEVERE RISK DAY 5

IS THAT BOTH MODELS ACTIVATE CONVECTION ACROSS TX LATE DAY 4 AND

INTO THE DAY 5 PERIOD. WHILE SOME SEVERE RISK WOULD EXIST WITH THIS

CONVECTION LATE DAY 4 ACROSS PARTS OF WRN AND CENTRAL TX...GREATER

RISK IS EVIDENT DAY 5 ACROSS PARTS OF N CENTRAL TX AND INTO THE ERN

HALF OF OK AND THE ARKLATEX REGION...AS THE MOISTENING BOUNDARY

LAYER DIURNALLY DESTABILIZES. HERE...SEVERE RISK -- INCLUDING SOME

TORNADO POTENTIAL -- IS EXPECTED.

THIS SRN BATCH OF CONVECTION MAY HAVE EFFECTS ON AREAS FARTHER N --

I.E. INTO PARTS OF NERN OK/SERN KS AND THE OZARKS...BUT A SECOND

AREA OF LIKELY SEVERE RISK IS EXPECTED ACROSS PARTS OF ERN KS/NRN MO

AND INTO IA/SRN MN -- NEARER THE SURFACE LOW WHERE THE STRONGEST

FLOW ALOFT/MOST FAVORABLE SHEAR IS EXPECTED. RISK FOR HAIL/DAMAGING

WINDS ALONG WITH ISOLATED TORNADOES IS EXPECTED IN THIS REGION

THROUGH THE AFTERNOON AND EVENING.

WHILE TWO DISTINCT AREAS OF SEVERE RISK MAY RESULT -- A NRN AND SRN

AREA -- ON LARGER RISK AREA WILL BE INCLUDED ATTM PENDING LATER

FORECAST DETAILS.

WITH THE UPPER TROUGH PROGGED TO CONTINUE QUICKLY NEWD INTO CANADA

DAY 6...LESSER SEVERE RISK IS PROGGED AND THUS NO RISK AREAS WILL BE

INCLUDED ATTM.

 

changes to area highlighted 

 

 

[jojo762]

12Z GFS showing backed srf winds from western Iowa/eastern Nebraska south all the way to southern ok/northern tx at 00z for Thursday... Environment looks pretty dangerous IF the atmosphere is able to recover from morning convection... The entire dryline could light up if that happened, the area around the low could be a bit messy though given the large amount of lift... Personally like eastern KS/ OK at this point for the biggest tornado threat. LLJ also ramps up a bit, and the Deep-layer shear increases to ~60kts across eastern Ks and NE Oklahoma... Will be interesting to watch this develop, and become more clear... Seem like the GFS has switched every run the last few over whether the srf winds will be back, or whether they will be Uni-directional.

[thewxmann]

If it weren't for progged morning-afternoon crap-vection across TX the Thursday setup would look pretty darn attractive. I blame the EPAC tropical stuff for that.

 

As someone mentioned earlier in the thread, at least the trough ejections this year have been legit, something 2012 could only dream about.

[Ground Scouring]

If it weren't for progged morning-afternoon crap-vection across TX the Thursday setup would look pretty darn attractive. I blame the EPAC tropical stuff for that.

 

As someone mentioned earlier in the thread, at least the trough ejections this year have been legit, something 2012 could only dream about.

Correct me if I'm wrong, but the models tend to overdo MJO-related convective feedback in the EPAC early in the year and have since backed off from the TC solution (at least as the ECMWF has). I don't think the EPAC moisture flux will be an issue. Furthermore, the 12Z ECMWF shows a shift toward the GFS's slower solution is a bit better timed re: diurnal heating / instability before the cap erodes. I think we might see more shifts in the mid-level pattern so that the cap will erode later early Thursday afternoon rather than earlier in the morning, thereby reducing morning convection with more of a mid-level dry punch.

[andyhb]

Regardless, the current poor timing of the shortwave is going to cause problems here, it is basically timed right now to screw up both Wednesday's setup (too slow) and Thursday's setup (too fast).

[tornadotony]

Regardless, the current poor timing of the shortwave is going to cause problems here, it is basically timed right now to screw up both Wednesday's setup (too slow) and Thursday's setup (too fast).

Assuming the timing stays the same.  This is still a D4-5 forecast...

[andyhb]

Assuming the timing stays the same.  This is still a D4-5 forecast...

 

Yes, it wouldn't take a large adjustment to bring something more threatening into the picture with a large/relatively potent system such as this.

[Ground Scouring]

Assuming the timing stays the same.  This is still a D4-5 forecast...

And now the 18Z GFS comes in with a noticeably faster lee cyclone Thursday morning. It also shows more of a warm temperature tongue (more southerly than westerly flow) at H7 that could suppress junk convection. That could potentially increase instability by early afternoon before steeper mid-level lapse rates arrive. Indeed, 18Z is noticeably more robust with a broader area of 1,500+ j/kg SBCAPE along the dryline by late Thursday afternoon. If this becomes a trend then Thursday is absolutely in the game in N TX / OK / srn KS.

[OUGrad05]

Glad a thread went up on this.  Given this time of year and what I've seen I'd rather have a few timing differences four or five days out then having a great system.  Last week ring a bell for any southern plains folks?

It won't take much to to have a svr threat several days in a row here in OK.  This overall looks to be a decent system and with a few timing adjustments could result in some good chase opportunities...

 

I agree the timing of the shortwave is off right now and as mentioned above there is the potential for morning convection and atmospheric recovery.  But generally I think the OK/KS border and (maybe 75 miles north) and off to the south will have the ability to recover.  Lots will change the next few days but so far this year has been a total flop here in OK and we've got another 5 or so weeks left of prime chase season...

[Ground Scouring]

The 00Z GFS is a bit faster and farther N with the mid-level cyclone by Day 4 and thus keeps the warm sector over N TX / OK / srn KS capped longer (vs. uncapped on the 12Z run), resulting in greater instability over the warm sector by Thursday afternoon, with at least moderately unstable lapse rates in place at that time. A big question concerns the rather anemic LLJ along the dryline despite the development of a secondary low and the relatively strong deep-layer shear that is almost perpendicular to the dryline. The 00Z GFS nudges the rear entrance region of the H85 jet a bit closer to the dryline than previous runs did at the time of the greatest instability. Overall the threat is going to come down to mesoscale factors but the threat of junk convection is decreasing in my view. Now the question of storm mode might be problematic given the back-veer-back H85-H5 crossover. But the key is that the model has trended over time toward a deeper shortwave due to a more consolidated mid-level vorticity maximum rotating around the base of the trough.

[brettjrob]

The shortwave timing is close to the worst-case scenario, and realistically at this range, it's probably not going to change enough to make a fundamental difference. We go through this so often, and 9 times out of 10, when something looks severely mis-timed even at 120-144 hours, it verifies as such.

 

When it comes to the effect of drought, I've often said that it typically doesn't dictate dryline placement to a huge extent; that to a larger extent, it just modulates vertical mixing (and thus BL moisture quality) of the airmass east of the dryline. I'm starting to question that, though. I don't see any synoptic reason besides drought that the dryline should be positioned so far east on Wednesday, and a similar pattern has emerged several days already this year. If the dryline were closer to the KS/CO border and the Panhandles/SW KS were in play, then perhaps the relatively late arrival of energy Wednesday evening wouldn't be a big problem. So, if we assume drought is partially responsible for the eastward dryline placement, this is just another way it can wreck potential setups.

 

For Thursday, I haven't completely given up, but it's on the rocks. I have to think given the calendar date that the GFS depiction of morning convection completely erasing instability up in IA is overdone, and there should be some potential in that area near the primary sfc low. For OK/TX, things will really hinge on whether a secondary shortwave can pivot through at the right time (and be of sufficient strength). The general pattern with a primary vortmax well north over the central Plains is one that often leads to frustration down here, but every once in awhile comes through (see the Binger/Cordell day in 1981).