10-29-04 FCST: Midwest & Plains

[David Draun]

I have low clouds moving in. T/Td: 66/64

CAPE at ILX is around 750 J/kg at this time. Expected to break 2500 J/kg this afternoon.
But, for surface based thunderstorms it needs to be 84 degrees.

 

[Glen Romine]

Interesting forecast today. Still seeing some reasonable chances for discrete cells in MN to WI along the slowing warm front - if they can get surface based is too tough to assess right now. I like the curved region outlined by SPC across central MN. RUC reluctant to move the low much during the day - and holding it further west - so I'd probably even lean toward western central MN at this time. Just south of this, the front should sweep rapidly around the low, perhaps kicking off the squall line near the MO River by early afternoon, 1-2 is my best guess right now give the cap strength shown OMA and adjusting based on RUC forecasts (though the model generates precip later than this). Given the shallow moisture depth across IA - and very strong winds of 40-50 knots at 850 mb - expect a strong cold pool to develop and agree that damaging winds will be a significant threat - though I'd extend the hatched region shown by SPC further west.

Glen

 

[Robert Dewey]

This system is moving slower than the previous forecast... I would target central and western IA and middle/southern MN (mini-supercells along the warm front)... Anywhere further east than that, and it will be getting dark by the time the storms arrive, and they will likely be linear by then. Instability looks good, as well as SRH of 200-300m2/s2, so a few tornadoes are certainly possible in the mentioned area...

For points further east... If the ETA has it's way, expect a line to roar through between 00Z and 06Z SAT... (Eastern IA around 00Z, and later points east)...

Also of GREAT concern is the ETAs' lack of QPF for the entire event across that area - That's how the last event portrayed things, and everyone discarded it... It still possible that forcing will be a little too difuse for the amount of shear...

I'm still stickin with my "virtual" target of central/southern MN, and western/central IA... RUC2 develops a line around 21Z, and pushes it through the eastern part of the midwest (southern WI/northern IL) after 00Z, so it will be dark (or at least getting very close to dark), so areas further west look good.

 

[Bill Schintler]

Chase target for today, October 29

Chase target:
Ortonville, MN.

Timing:
Storm initiation 5 PM CDT.

Storm type:
Isolated weak supercells, and possibly a weak short-lived tornado or two. Storm motion will be northeast at 20 mph.

Discussion:
Today is fun - this is more like an April or May discussion, and it’s almost November. The 12Z analysis shows a strong storm system moving into the upper Midwest. At the upper levels, a counter-clockwise fanning diffluent 60kt+ flow is lifting NEWRD through NEB towards the FA. A 996mb surface low is located near Chamberlain, SD; with an associated WF extending EWRD along an MML – HCD – RNH line. Impressive moisture for this time of year is in place in the warm sector, although the depth is shallow – the 12Z OAX sounding indicates a 50mb deep moist layer, with a surface Td of 65F. The depth of the moisture layer is a mixed blessing, as it has reduced the extent of the warm sector ST. In any event, MLCAPE’s today will be marginal for widespread severe weather – expect on the order of 1000 J/kG at best, although 500 will be typical in the FA.

Ongoing storms were lifting NWRD through SD – expect these to stay W of the FA. Expect new storm initiation along the WF around 22Z along an ATY – STC line. It appears as though a compact mesolow will develop along the WF E of the main low near ATY around 21Z, and locations just E of this feature will see enhanced LLVL directional shear. Further W, LLVL moisture profiles fall off rapidly. Additionally, 0-6km shear falls to less then 20 kts along the MN/SD border and points to the W.

bill

 

[Andy Wehrle]

Should we maybe start a NOW thread for this pretty soon since we are getting current conditions now? For example right now in GRB 63/62, foggy and cloudy as can be. Hopefully that warm front will make it through here shortly.

 

[Glen Romine]

Should we maybe start a NOW thread for this pretty soon since we are getting current conditions now? For example right now in GRB 63/62, foggy and cloudy as can be. Hopefully that warm front will make it through here shortly.

No. Please read the TA rules.

Glen

 

[David Draun]

Satellite shows a Cu field trying to develop in NW IL, E IA, and SW WI. Low clouds are obscuring this development, but it is clear on the visible satellite that there are Cu present. Now at 70/66, (wow that's a high Td for late Oct! :shock: ) Sun is trying to break through. There's a SWODY1 update in 10 minutes. Will we get that MDT upgrade?

Radar showing those Cu trying to fire into at least some showers.

EDIT: We have an upgrade! MDT risk out for much of IA/WI/MN. Includes 15% tornado, 35% signifcant winds. Could we have a late season sevwx outbreak on our hands?

 

[Jeff Piotrowski]

Chase Target NE/EC OKla.

Looking at the 15z ruc supercells form in advance of the dryline from MLC-FSM around18z-21z.The dryline storms from CNU-TUL around 21z should make for an interesting afternoon. I also like DSM after 21z.Good luck for all that chase today.

 

[Glen Romine]

Re: Chase Target NE/EC OKla.

Looking at the 15z ruc supercells form in advance of the dryline from MLC-FSM around18z-21z.

If you look at a current radar, you can see junk convection going in this region now. Strong deep moisture convergence in this region seems to be leading to some cells developing. I'd refrain from qualifying these as "supercells", and probably are not even surface based. Cells might develop later on the dryline, but surface winds are strongly veered in advance, and this is not only limiting convergence but reducing helicity. Look at a time series of the sfc obs and you'll see wholesale veering across OK, so the helicities in the current RUC analyses likely will collapse by this afternoon.

Glen

 

[Mike Peregrine]

MD 2365 issued for eastern Kansas and western Missouri http://www.spc.noaa.gov/products/md/md2365.html ...

ww will likely be issued in the next few hours - as afternoon continues - environment becomes more favorably sheared, and adequate llvl moisture availability appears suitable for supercells.

 

[Dan Cook]

*moved to nowcast thread*

 

[David Draun]

I'm still stuck in low clouds here, but it is 73/66. It feels like a cold day on a tropical island. Y'know, natives would feel cold, visitors would be comfortable or too warm. Well anyway, I digress. On the satellite picture, I see the clearing in W IL. I would hope that gets here soon. The hour of peak heating isn't too far off. Usually it's warmest at 3 or 4pm. Storms have been removed from the forecast here for the afternoon. But, I am still right on the edge of the moderate risk area. I don't see 80 happening today anymore, not even much more than 75.

 

[Mike Hollingshead]

More of a now/location cast but might be of interest. I'm starting to like this line of cu in eastern NE. I keep getting up and looking out the window as I'm right under it and getting more and more excited each time. Though I do not have a real idea what area of this line to target since it's on me and moving east with no convection. I would think an area of sw IA might be a decent op as the temps and cu down there seem more favorable then points furhter northeast in IA along it. The cu though are getting better and better. Colder air aloft must of hit the area pretty quickly as it formed really fast and 850 moisture had been getting scoured out. It was looking pretty down. I would expect radar returns along this boundary within an hour....jinx. It is really obvious they have their work cut out for them though with this amount of shear(85knt core at 500mb). Not overly excited about any tornado potential but convective potential at least looks pretty likely now(in this area).

Edit: Just issued... http://kamala.cod.edu/spc/0410291912.acus11.html