5/08/06 FCST: KS, OK, TX, NE, IA

At the surface, primary surface cyclone will be over northern Minnesota/southern Canada, with resultant cold front arcing back south then south west into the central high plains where secondary surface cyclone will deepen to 999 mb by 0z. Dryline (which has become better defined with latest NAM run) is progged to stretch across central Kansas the south southwestward through western Oklahoma into western Texas by 0z. Latest NAM run also backs the surface flow more than with prior runs wich brings in mid sixties dew points at least through much of eastern Kansas and all of Okahoma. Marginal ssw 850mb flow atop sse surface flow will yield Helicity of up to 200 m2/s2 east of the dryline in Kansas as well as Forecasted CAPE of up to 2000-2500 j/kg across most of Oklahoma and central/eastern Kansas, and hints at a bullseye of 3000 j/kg in south central Kansas. So that all sounds great but things get kind of dicey in the middle and upper levels of the atmosphere. First, Models forecast 2 separate H5 waves to progress across the area Monday. One will push across the across the forecast area around 12z and followed by subsidence
Through much of the day until the next Wave approaches the area by 0z. A couple of concerns with this, 1) will the first Wave spark convection early in the day and keep clouds and rain across the target area for too long? 2) Will subsidence in wake of the first wave linger across the area to long and prevent deep convection from initiating?
Typical of rescent events (excluding 5/5/06) is the lack of speed shear in the atmosphere, even with good directional shear this could cause a problem with storm structure, not to mention the northwesterly upper level flow presents its own set of problems.
Now back to the possible early morning convection, one upside I can find in it is that if it does clear in time it could put out some outflow boundaries to aid in storm rotation. Another upside to it is that it could reduce mixing enough to keep dewpoints from mixing out along the dryline, and that combined with the early clouds/crapvection keeping temps down a bit will keep LCLs from being too high. Keep in mind that if temps stay down a bit it may not hurt us too bad as far as convective initiation goes since cap will be rather week in Kansas, in fact lower temps combined with subsidence in wake of first Wave may aid in holding down convection until the next upper waves kicks in later in the afternoon evening.

Overall I think a complex situation that I think has the possibility to be very good or be very bad depending some of the processes that I have talked about above.

Thoughts?
 
I would target Central KS, too, based on 00Z May 6 NAM. I'm only taking this with a grain of salt at this point. 500mb winds are more westerly over Central KS which should help prevent downdrafts being digested into the inflow which will be more problematic farther south. With the NW flow pattern in place (500mb temps <-15C) I can't help but think very large hail will be possible. NAM shows a little blob of 3000 J/kg CAPE over the KS/OK border. My main concern at this point is the 500mb wind direction. The 00Z GFS 500mb winds make me much happier with westerly winds from TX to the KS/NE border. It is also about 5F higher on the dewpoints with steady 70F dewpoints all the way into central OK, but I don't buy it right now. What is troubling me is the NAM showing overnight precip over central TX which could potentially severely limit moisture return for points northwards. The GFS also shows overnight precipitation over western OK and SE TX. This could be a good situation with W-E OFBs and westerly winds. Unlike April 24, the cells would be running parallel to the OFB.
 
Noticing Some significant model to model differences between gfs and nam concerning the Kansas Oklahoma setup in the latest run.

NAM- Proggs marginal at best dewpoint immediately along the dryline, with best dewpionts staying a good distance east of the dryline, CAPE also looks pretty bad. Also proggs somewhat weaker wind fields than GFS, and doesn't back surface flow as much, thus reducing helicity. Not to mention NAM forecasts more north westerly flow, while the GFS continues with a more westery and posibly wsw upper level flow. Basically if the NAM verifies, Storms will be highbased, outflow dominated storms and I will not be chasing.

GFS- Proggs much better moisture and CAPE along a more defined dryline, backs the wind at the surface, and proggs stonger 850-700mb windfields as well as doesn't veer the 850 flow as much as the NAM. Not to mention that upper flow remains more westerly especially in Kansas. If the GFS verifies I will chase the dryline in the Kansas, Oklahoma boarder region.

Bottom Line: Unless the gfs is dead on moisture will be a problem so can go ahead and anticipate moisture problems. If models continue to differ, day of event evaluation of the LCL's, instability, and wind fields will be key in forecasting the severity/tornado potential of any storms on Monday.

Hey its not the greatest setup ever bbut I haven't been able to chase the Texas stuff so I will take what I can get.
 
The difference with the NAM/GFS at 12Z doesnt really appear to be the location of the moisture, but the strength of the dryline, with the NAM being much more diffuse. This is going to be one of those setups where we won't know exactly what we're looking at until the morning of the possible chase. I'll take my History bluebook final tomorrow morning and at 10:15 see how things are looking, and either stay at work or go out. Since Saturday morning the possible chase region has shifted southwards almost into the west-central OK region with backed winds from SW KS into SW OK via GFS. NAM tends to verify on the location of the dryline, but thats where most of the verification ends. As mentioned above if NAM verifies: no chaseday for me, if GFS verifies: I'm all over it.
Honestly though, I'm having the gut feeling that a NWerly 500mb flow will be the case, and as mentioned above this has outflow-dominant written all over it.
Looking at the SPC Day2 convective outlook, my question is, why is the Slight risk so farth north?
 
Looking at the SPC Day2 convective outlook, my question is, why is the Slight risk so farth north?
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The Text in the Convective outlook for the Oklahoma Texas area (may have been yesterdays version, not sure) mention somthing to the affect that subsidence and upper ridging may hold things down in southern oklahoma and Texas.
 
Chase target:
10 miles west of McPherson, KS.

Timing:
Storm initiation 5 PM CDT.

Comments:
Isolated supercell storms between 6 PM and 8 PM, with storm motion to the east-southeast at 15 mph. Hail to golf-ball size will be the primary severe threat.

Discussion:
Today, a diffuse dryline will develop well to the west of the target area, and storms should initiate to the east of this feature as convective temperatures in the low-80’s are reached and a weak wave spreads over the area. WV imagery indicates a vorticity ribbon lifting out of eastern CO, and large-scale assent associated with this wave will aid in convection. Moist layers are around 150mb deep in CNTRL KS, with SFC dewpoints currently in the upper-50’s; and dewpoints will increase into the mid-60’s by mid afternoon. This moisture, in combination with SFC temperatures reaching the mid-80’s beneath steep lapse rates in the 800 to 600mb layer will contribute to MUCAPE’s to 3000J/kg. Wind fields are generally weak, with forecasted deep layer shear AOB 30kts; however a modest sfc-1km shear vector will develop as a 30kt LLJ develops over lightly backed 10kt SFC flow. This shear vector, in combination with T/Td spreads in the 15F range, may aid in tornadogenesis.

- bill
 
Today may be a tail end charlie day due to the southeast storm motions and westerly upper level winds. (Northern storms might get rained on) It also appears like the RUC is hinting at a dryline bulge near the OK panhandle this afternoon. We're targeting the DDC region hoping to catch the tail end charlie. This could be a late night because of the large instability and low level jet which develops towards and after sunset which will sustain storms and increase the low level helicity respectively.

I'm afraid the models may be once again too high with the surface moisture. The soundings for OUN and DFW show shallow moist layers and the outflow boundaries in TX (north and near Austin) are leading to easterly and northerly flow preventing the highest Td air from advecting north. It looks like the moisture is taking a westerly route up the TX plateau which was where the low level jet was located earlier this AM and last night. Low-mid 60's dewpoints with temps in the low 80's will be sufficient enough for tornadoes (decent LCLs) not to mention a moist RFD can substantially lower dewpoint depressions.

Another interesting feature is the E-W oriented outflow boundary just south of the red river. If the GFS dryline bulge verifies, this may be enough to break the stronger cap to the south and any storm that roots on that boundary will have large low level vorticity to ingest as well as abundant moisture.

Good luck to everyone chasing today.
 
Ok i dont have really a chase forecast...more of a nowcast....would make a now thread but it wouldnt be for tornadic potential...so if mods feel this is unfitting of chase forecast...then can be moved/renamed

Currently storms are xploding across southern, eastern, and central oklahoma. Presently isolated and elevated severe storm are ongoing across southern and SE Oklahoma in response to s/w and elevated moist axis [see SPC MD#790]. Looking outside of my apartment it looks as if the dryline is punching through when in reality its not. I say that b/c theres a nice line btwn towering cu/scud and clear sky that is pushing northward. One thing that has gotten my attention is the clear sky has got that hazy look to it now, you know how a clear or partly cloudy sky looks when its heavy with moisture. The sky doesnt have that rich blue color..its more of a light blue b/c of moisture moving in. Its really cool to see these storms exploding right over top and pushing northward.

Now for the "forecast" or what im keeping an eye on that might happen:
Looking at current sfc obs Im seeing rich moisture just across the Red River on the warm side of the retreating cold front/warm front that is drapped e-w across central/eastern TX and central LA. I also see that winds are backed appreciably behind the boundary (south of it). As far as the next 36hrs are concerned, im going to be interested to see how far north that warm front makes it b/c having those backed winds combined with the rich mositure may make things interesting around here for a change. Unfortunately the big fly in the ointment is lack of shear. Checking area VAD wind profilers (those that were at least operational per COD site) surface winds to H50 are downright crap. However once you cross the front (south of it) upper level winds are very strong out of the west and H50 winds are modest. So theres is definately jet max along and south of the front. But overall from the surface to 500mb all across the region the winds are lacking for tornadic setup. Looking at VAD data in KS upper level winds are more NWly than westerly. And again surface winds leave much to be disired(sp). Even if mid level winds arent SWly but are instead westerly, I ll still take that for tornadoes just not NWly. The way the last month has been discounting the day of the El Reno tornado, Ill take what i can get. Really cant go out today with impt 8am final tomorrow morning but definately have my eye on tomorrow for sure.
 
Ok made a last minute decision to go out. I'm going to target Woodward and by the time I get there I'm sure I'll have a good idea as to whether I want to back farther south (GFS verification) or north to DDC (RUC verification) or maybe somewhere right in the middle (at Woodward) if I'm lucky. The E-W OFB across the RRV is interesting, but if RUC 500mb verifies it will be an outflow dominate fest with NWerly winds. 500mb per RUC appear to be more westerly over SW KS (and I hear this is some of the best chase terrain, I will find out..hopefully. :) Good luck to all chasing today, I'm not expecting a tornado but I'll take one. Hopefully I'll get to see some good storm structure.
 
Just wanted to mention this....VAD profiles from KICT and KVNX show a backing wind profile through the BL or right on top of it. Unfortunately the profilers in the area are busted, so can't look at those to see what's going on above the BL. Don't know what this means or where this is coming from, but just something of interest I thought I would bring up.
 
I'm currently in Salina, KS under partly cloudy skies and probably will head west shortly... SPC mesoanalysis shows > 2000 j/kg sbCAPE invof surface trough (with 75-100 j/kg 0-3km low-level CAPE developing as well) where strong diabatic surface heating has contributed to very steep low-level lapse rates. 0-6km deep shear is a bit weak (once again), but the 30-35kts should do -- with RUC showing low-level shear increasing later this evening ahead of the boundary -- supporting a threat for organized supercells with extremely large hail and at least a couple of isolated tornadoes. I think the slight limiting factor will be the relatively high LCLs across the moist sector (e.g. 1200-1400 m, per SPC mesoanalysis -- immediately near the boundary).
 
Sitting in McPherson, KS checking over things. I'm tempted to go further west now towards Great Bend. SRH is definitely going to need to come on this afternoon, but still a lot of good things going for today. I'm not too concerned about LCL's....figure anything <1600 is okay. The further east it goes, the better it gets.

Ugh.....decision time. Hold out for a while, get some rays and play it as it goes, or press on west.......
 
surface moisture continues to stream northward with dp's as high as 60 making into SE nebraska. Some cu has started developing around omaha and points westward with the boundary still well to out west in central NE but racing eastward. new md out for central and parts of western kansas stating that initiation may occur within the next 1-2 hours as continued heating further weakens the cap. Hopefully as low level flow with the forecast LLJ and the weak shortwave moving overhead we can get a few organized storms.

goodluck to all...
 
Sitting in Newton KS. Wind out of the straight south 15 - 20mph... air feels dryer than I would like. I think I will head NW, based on info from MD.
 
Sitting in DDC right now, today is shaping up to be exactly as I expected. Hopefully I'll get some good sunset photos. I can see the cells very clearly to the north and development to the WNW. I think the best tornadic potential will be at sunset or after, hopefully I can get some good lightning shots and maybe sneak a wall cloud in there. Tomorrow looks more interesting than today, but I have finals tomorrow so I'll take this no problem.
Anyways back to meteorology... Winds seem to back nicely in and near DDC by 0300Z (10pm, blah). Could be a late night, hopefully we can get a few embedded supercells in the line. Won't be the pretty lonely supercell in the middle of the plains tonight.
 
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