11/12/05 FCST: Upper Midwest through Southern Plains

[Mickey Ptak]

I have made broad forecast range due to the this date still being 5 days out and I am sure things will change. However, the past three GFS runs have been persistent with the shortwave in the TX PAN, OK, KS general area. GFS also continues to bring somewhat better surface moisture in to the area throughout Friday into Saturday with surface 60Tds and 850mb at 12c Tds. Not the greatest deep moisture but we have managed with worse.

I can’t get any BUFKIT GFS data so I have no idea how the forecasted hodographs look like but just based of the maps I would say directional shear and speed sheer look very good for supercells.

The best thing about it is it's on a weekend right after payday! Plans are already in the works.

Mick

 

[Brett Adair]

Looks like a descent dryline ejecting out with that kind of low level moisture, there would more than likely be some supercells with dewpoint depressions along the axis. The GFS has had a persistent ULL over the SW that tries to kick out. Looks like an interesting senario for some possible tornadic/large hail action.

 

[Jim Bishop]

Well the 00Z Nov. 8th GFS solution basically indicated a significant severe weather outbreak including supercells with tornadoes over Oklahoma and Kansas. Now the GFS is ejecting the system too fast and it doesn't at all look like the same setup. The end of the NAM run hints the same thing. But it's still 4+ days out, plenty of time for change.

 

[Justin Teague]

Well, the 12z GFS has presented the first real change, pushing the system a little further east by 0z. Everything else is still looking good, esp. moisture return with 60's Tds into the target area by 12z Saturday. Speed and directional shear look good, so if things hold up, supercells appear likely. I don't do any true "forecasting" this far out, but I am a little more excited about this event, as Saturday is my birthday. I have never chased, or expected to chase on my birthday, so this is really cool. I am a little concerned with instability, but that is always a problem with a dynamic systems in November.

 

[Angie Norris]

I know it's still just a bit far out, but I'm already going with a preliminary target of the Woodward area for Saturday. Shortwave coming through, decent moisture, nice shear...I know it's still essentially wishcasting at this point, but there are glimmers of hope there on GFS. If my car's out of the shop by then, I'm going looking for birthday tornadoes.
Angie

 

[Jonathan Whitehead]

I noticed this on the latest OUN AFD. But one thing im concerned about is moisture return. Now granted I havent looked at an model data but seeing these type situations before, I know what can happen that a lot of people dont anticipate happening. Look at the OUN AFD.

.PREV DISCUSSION... (ISSUED 227 PM CST TUE NOV 8 2005)

DISCUSSION...
WILL ALLOW RED FLAG WARNING TO EXPIRE AT 6 PM AS WINDS SHOULD COME
DOWN QUICKLY AROUND SUNSET.

STRONG FRONT TAKING SHAPE TO OUR NORTH THIS AFTN WILL MOVE SOUTH
ACROSS THE AREA ON WEDNESDAY. THIS FRONT WILL KNOCK TEMPS BACK
SOME 20 TO 30 DEGREES ACROSS MUCH OF CENTRAL INTO NORTHERN OK. THIS
WILL AT LEAST GET US BACK DOWN TO NEAR THE NORMAL MARK FOR THIS TIME
OF YEAR. SE OK WILL AGAIN SEE TEMPS REACH NEAR 80 BEFORE TEMPS COOL
DURING AFTN. UNFORTUNATELY... THE FRONT APPEARS THAT IT WILL GO
THROUGH DRY... AS MUCH OF THE UPPER SUPPORT WILL BE WELL REMOVED
FROM THE AREA. ALTHOUGH THIS SHOULD ALSO PUT AN END TO EXTREME FIRE
CONDITIONS... AT LEAST TEMPORARILY... THERE WILL BE STRONG NORTH
WINDS FOR MUCH OF THE DAY ON WED AND DRIER AIR WILL ALSO MAKE FOR
SOME LOWER RH ACROSS NORTHERN HALF OF AREA TOMORROW.

COOL...DRY SFC HIGH WILL MOVE INTO AREA AND ALLOW A COUPLE OF
PLEASANT DAYS BEFORE SOUTH WINDS RETURN ON FRI AS SFC HIGH SHIFTS
EAST. SFC MOISTURE WILL BEGIN TO MOVE BACK NORTH IN ADVANCE OF UPPER
STORM SYSTEM NOW OFF THE CALIFORNIA COAST. THIS DISTURBANCE WILL
BEGIN TO MOVE EAST AND IS EXPECTED TO BRING SHWRS/TSTMS TO THE AREA
BEGINNING FRI NIGHT THROUGH SAT. WILL INTRO SOME LOW POPS FRI NIGHT
AS STRONG LOW LEVEL JET AND WAA MAY ALLOW FOR A FEW ELEVATED TSTMS
TO DEVELOP OUT AHEAD OF MAIN WAVE. DRY LINE THEN SETS UP ACROSS TX
PANHANDLE SAT MORNING. THIS DRY LINE MARCHES EAST DURING THE DAY SAT
AS UPPER LOW OPENS UP AND EJECTS EAST ACROSS THE SOUTHERN PLAINS.
THE POTENTIAL DOES EXIST FOR SEVERE WX ON SAT. AS UPPER WAVE LIFTS
NE WITH SFC PACIFIC COLD FRONT MOVING THROUGH SAT EVENING WILL
REMOVE ANY POPS AFT SAT EVENING.

My concern is with this front thats scheduled to come through tomorrow and clean us out. If Saturday's s/w were to come through tonight, then Id be much happier but im not so sure that even with the return of the southerly flow that we will be able to bring back the magnitude of mositure that is needed in such a short time span. Look at the last few "events" around here lately and you see that moisture return was THE problem. But like everyone else, Ill say that it is a ways out. Right now, all are in wait and see mode

 

[Jim Bishop]

Moisture shouldn't be a problem with this setup as the cold front isn't going to have any impacts on the Western Gulf. This setup's looking more and more like a late morning/early afternoon tornado day for Southwest/Central Kansas. These are always very conditional setups!

There's a lot of uncertainty due to timing issues with the GFS & NAM. But I'd say if morning convection can move east early enough and allow some surface heating ahead of the surface low/dryline over Southwest/Central Kansas, then low topped supercells with tornadoes are possible. There would likely be a quick evolution into line segments (not a squall line) containing low level mesos and a couple more tornadoes, given really no speed or direction shear above 850mb. But there will probably be a 2-3 hour window for low topped supercells to produce tornadoes around noon.

 

[nickgrillo]

..

 

[Justin Teague]

The models are most likely ejecting this system too fast. They have done this with the past several systems, so my confidence in the current solution is low.

MORE OFTEN THAN NOT...IT SEEMS THAT THE
MODEL EJECT THESE SYS OUT OF THE SW TOO QUICKLY.

Source: http://www.hpc.ncep.noaa.gov/discussions/pmdhmd.html

 

[Jim Bishop]

At the point, the only area I could see a tornado happening would be in southeast KS and then back down into extreme eastern OK, and this would be shortly around sunset at 0z SUN ahead of the dryline.

Nick - You are correct in saying the GFS has trended faster in ejecting this shortwave. But with such intense upper support you will have strong mid-level cooling. Storms are going to fire early, and the GFS even breaks out precip by 18Z Saturday all over Eastern Kansas along the dryline.

But, I don't like how it shows the vort max becoming more elongated than before, and merges with the northern branch of the jet. For this type of setup, an elongated vort max = squall line. We'll see how the models change over the next few days.

 

[HAltschule]

in some marginal 200-250m2/s2 0-3km SRH.

Marginal??? That's pretty decent helicity, even for the 0-3km sector. 200-250 SRH is easily severe TRW criteria and borderline tornado.

 

[brody_clifton]

48hr NAM forecast CAPE/ 3km helicity currently pointing to a Wichita Falls, TX to Childress target area for Friday, just on the northern end of the best CAPE (500-800J/Kg) and the southern end of the helicity (~250m^2/s^2), but 175 miles southeast (vs. just ahead) of the 500mb jet streak. Moisture looks to be decent in the area, being on the northern surge of a ~330 thetae airmass, 18C surface temp, 60F dewpoint, and 13C 850mb dewpoint. Per NAM guidance, Saturday afternoon is looking even better for SE KS/NE OK with CAPE aoa 1000J/Kg and 0-1km helicity values approaching 250m^2/s^2, and with the intersection of a 35+ kt 850mb southwesterly LLJ and 60+ kt southwesterly 500mb jet. Surface winds projected to be from the south to slightly ssw at 10-15kts, so that may provide ample low level shear for a tornadic supercell or two. 0-6km shear values look good enough for supercells. From what I see, it Looks like things may start early Saturday, maybe 11AM or so - CIN looks to be not much of a player. All pending future model output evolution.
GFS showing the same but with faster progression of the 500mb jet into northern MO/southern IA Saturday afternoon. If thats the case the dynamics overrun the richer boundary layer conditions. If the NAM is more on track with the timing of this system, which it hasn't been lately, afternoon supercells are possible. Otherwise, the result will probably be a weak, fast moving squall line.

 

[Justin Turcotte]

Stretching the geography from the title but no use starting a separate thread. It's November and I see solid potential for a squall line and perhaps some embedded rotating storms in Iowa/Missouri and perhaps as far north as southern Minnesota Saturday afternoon and evening. This general area appears to have the best combination of forcing and moisture. Per 00z GEM and GFS: Deepening surface low moving northeast out of Nebraska to be centered in the MSP area by 00z Sun. No shortage of shear on the warm side of the front as upper-level winds are stong and increase with height. A 00z Sun DSM point sounding from the GEM reveals SRH of 400+. Mid to upper 50's Td are respectable for the area given the time of year. Looking ripe for a squall line and perhaps some embedded rotating cells. Would not at all be suprised to see an unusually late season tor report somewhere in this territory but it is looking like primarily a wind event.

 

[nickgrillo]

Strong SW LLJ with WAA will shift east across the central plains associated with massively negatively-tilted shortwave... This focus for ascent will contribute to a steadily increase in deep convection across the southern/central plains through the afternoon and evening. To the north, major airmass modification will be required across MN/WI and northern IA to support boundary layer convection... Thus, this activity, should remain elevated and largely driven by strong forcing along cold front with a threat for large hail and damaging wind gusts as warm front retreats into the region.

Further to the south, strong boundary layer moistening/heating will occur across the southern plains resulting in deep boundary layer thermals free to convect by the early-mid afternoon. Forecast soundings show steep mid-level lapse rates in dry slot... Ahead of the developing dryline (which should mix slowly eastward given deeper moisture)... With strong vertical shear through a deep layer supporting rotating updrafts. Strong mixed-layer CAPEs in excess of 1500J/KG across a narrow corridor supported by the steep mid-level lapse rates and increasing insolation should prove sufficiant for isolated supercells with large hail and damaging winds. There is some potential for a possible tornado or two near deepening surface low (given strong low-level flow resulting in moderate 0-1km SRH in excess of 150-200m2/s2) across eastern KS during the early-mid afternoon as any activity should remain isolated with initial development.

Overall, the NAM pretty much favors the eastern KS area... While the GFS favors areas a bit to the north.

 

[Bill Tabor]

Just looked over tomorrow's setup and also reviewed SPC's thoughts. I was thinking / hoping initially for something near Wichita Falls, or even from there to the DFW / Paris area down to perhaps Stephenville. Unfortunately it doesn't totally look that great the more I look. True that will be the tail end and the front / trough will slow / stall during the afternoon. However it appears even though there is some helicity and cape the EHI index doesn't seem to impressed with Tx south of the Red. Per NAM sometime after 18z the sfc low will continue moving east / northeast and elongating. Sfc pressures further south will increase and associated forcing pressures will weaken as well. Consequently expect sfc winds to fall off some from 18z highs and higher up 850 will weaken, veer, and with stronger winds in eastern OK. 700's and 500's as well will be stronger and more supportive of supercells in eastern OK (east of OKC) later in the day especially approaching 0z. It is interesting to note that NAM shows precipitation during the day but not convective. The 500mb shortwave appears to start influencing the area from OKC, SPS, DFW with a small preceding wave near 18z and continues to support some lifting through the afternoon though mostly a bit further west such as SPS and extending up into OK. Instability will be mostly stronger in OK as well though a small finger will extend down into TX with some reasonable for severe cape and -4 lifted.

With the shortwave and orientation of the mid level and sfc trough and sfc / 850 winds I expect further north from Tx that a squall line will form during the afternoon OK/KS/MO/AR. Probably precip will be ongoing by 18z at least. This will move slowly eseward while extending to the south. Tail end may be more discrete. I think a few supercells will be likely in OK especially nearing 0z - further eastern OK & these will be primarily embedded in the line, but a some could be near / ahead of it. I still think there is a long shot of something near the SPS / DFW corridor possibly of supercellur character. I'd probably put torn chances at 5% eastern OK and maybe 2% extending into northern TX. Still I usually prefer to chase discrete - non-linear storms so if anything was possible I'd probably be south at this time of year as saves gas and not as far to go for bust.

At this point unless the situation improves I probably wont chase as tail end looks weak. If I was in OKC already though I might consider following the development and might catch something as it moved east that was interesting though torn chances will be minimal with hail and wind likely.

Edit: I might mention that I pretty much cut off my forecast at the OK/KS border because that is beyond my chase area. So further north I didn't look at much although I expect squall to extend further north. Perhaps KS/MO may have a shot at something though I think I prefer combination of instabilty / shear in OK better. Also, it was an informal summary of my conclusions so I didn't elaborate on amount of cape, shear, etc.