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7/19/04 FCST-IA

Ryan Pfannkuch

Hey, let's not get too far ahead of ourselves here :) ....any chance we can get a FCST thread going for Monday?

Tonight's ETA shows an interesting setup for the IA/MN/WI region with very high CAPE, at least decent shear, and a surface boundary sagging into the instability axis by 0z. Another big plus is that the cap doesn't look to be an overly big concern with only 7-10C progged over the eastern half of IA at 700mb.

With the way some of the recent setups have seemingly caught some folks "off-guard," I just wanted to bring some attention to this possible event.
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Ryan Pfannkuch
Iowa State University
 
Interesting setup for Iowa. The low level shear looks a little weak, but I will say the strong winds aloft should keep these supercells more classic than hp. That's more than I can say for the supercell that will probably be in eastern South Dakota on Tuesday, with very weak upper level winds.

Despite weak low level wind fields, there is strong turning in the lowest km, and the hodographs don't look bad. I'd say there's going to be a few tornadoes, especially given the incredible moisture and instability. The supercell's alone will probably be structurally incredible.
 
New Day1 outlook from the SPC shows that the tornado risk has shifted a little bit to the west and southwest towards the meeting of the Iowa/Nebraska/Missouri State Lines, but so far, its still in the air.

*crossing my fingers and hopes something develops*
 
This thread seems rather unpopular, but I think there is some reason to keep an eye on the supercell in SW WI this morning. While the RUC analyses don't paint this cell's environment as being very favorable - it appears to be doing quite well and is gradually intensifying. 12Z INL sounding probably more characteristic of its current environment than MPX sounding. Helicity ofr this cell is better than shown, as motion is clearly right of the forecast storm motion. So, if the convection persists another 1-2 hours, it might manage to make things interesting along the Miss. River valley.

Glen
 
180 degrees of turning doesn't do anything for me. Seems like the updrafts will be sucking in their own precip. This is much like Thur was. Also where spc put their tor probs has 12c temps at 700mb which I normally do not have a problem with. Today however the convergence looks rather weak at best. A strong cap can be overcome with strong sfc convergence, and I'm guessing that won't happen today in western IA. I like nw flow, but I've not yet been convinced to like north flow.

http://www.spc.ncep.noaa.gov/exper/mesoana...sis/s1/mcon.gif

Interesting convergence in NE though. Hopefully the convergence will become greater somewhere later in the day....mesolow perhaps?

http://www.spc.ncep.noaa.gov/exper/mesoana...ysis/s1/ttd.gif

It would be nice to get those warmer temps to nose ne(which they should) and give e NE, w IA a nice mesolow. Then we might be game.
 
Still looking at the area along the IA-MN border east of Mason City as a potential playground later this afternoon. There is nothing spectacular about the setup to be sure, but the combo of CAPE and shear is hard to pass up given it is within a few hours drive. Sure enough, SPC just issued an MCD for this area.
 
TORN Watch

NWS has issued a TORN watch for Eastern IA and portions of WI and IL:

NWS STORM PREDICTION CENTER NORMAN OK
140 PM CDT MON JUL 19 2004

THE NWS STORM PREDICTION CENTER HAS ISSUED A TORNADO WATCH FOR PORTIONS OF EASTERN IOWA NORTHWEST ILLINOIS SOUTHWEST WISCONSIN EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 140 PM UNTIL 700 PM CDT.

TORNADOES, HAIL TO 2.5 INCHES IN DIAMETER, THUNDERSTORM WIND GUSTS TO 80 MPH AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
 
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