4/30/07 FCST: IA / WI

[Travis Carlson]

I thought about chasing this one but a 4-hour drive for a SLGHT risk and with several uncertanties that are present with the setup including dew pts not making it to 60F with alot of mixing taking place I decided to hold off. Watch there will be a EF3 tornado up there today Good luck to everyone, my target was NE Iowa from this morning around Decorah, IA looked to be a potential hot spot.

 

[Bill Schintler]

Chase target for today, April 30

Chase target:
Albert Lea, MN.

Timing:
Surface-based convection will initiate at 5 PM CDT.

Storm mode:
All forms of severe weather, including tornadoes, will occur over a limited area.

Synopsys:

Noon SFC analysis indicated WF from Clinton IA through just north of Waterloo and just north of Sioux Falls, with strongest pressure fall bulls-eye located just north of Watertown, SD. Along and S of this boundary, dewpoints of 55-60F were continuing to pool while backing SFC flow was noted along and N of the front. Soundings from OAX, TOP, and ILX (apparently there was no 12Z DVN sounding) all indicated that this moisture was extremely shallow. Additionally, convective temperatures in the low- to mid-90’s were noted. Upstairs, the pattern resembles that of mid-summer with weak ridging in place and the strongest H5 flow near the CAN border. Meanwhile, WV imagery and H7/H5 charts indicated a subtle impulse translating E through the Dakotas.

Discussion:

The aforementioned shallow moist layer should rapidly mix out during the afternoon hours except for along and just N of the northward-moving front. Aiding the moisture situation are the recent rainfalls in excess of 2 inches which fell over most of IA late last week. One can be assured that SFC dewpoints would be in the 40’s in IA at best if this were not the case. By late afternoon, the SFC low should track just E of Brookings, SD. A narrow axis of moisture and modest instability will exist along the boundary extending E and SE of this feature while large hodograph curvatures will result from 35kt WRLY H7 flow over backed SFC flow along the boundary as it lifts slowly to the north into MN. Later today, outflow from ongoing elevated convection along and N of US-14 in MN will serve to reinforce convergence along the SFC boundary.

- bill

 

[Jim Zandonai]

Yeah NE IA around Decorah seems to be a 'historically' good place ..ie there always seems to be a good storm around there for some reason in situations like this..in anycase being in Rockford here and working till 530pm today we will hopefully catch something as it slides SE from WI. into our area later..we will see.

 

[Danny Murphy]

04/30/2007 NOW Stanley, Iowa

Most of the afternoon has seen temps in the mid 80's with clear skies and SE winds. Over the past 15 minutes or so winds have switched to the West and WSW and cumulus clouds have begun to develop. The temp has rose dramatically to near 89F by 3:35pm.

 

[Danny Murphy]

04/30/2007 NOW Stanley, Iowa

The front has been meandering right on top of us all day at one time it has been warm and in the low to mid 80's, then it moves a little to the NE and a surge of warm air with winds switching from SE to WSW and the temps rise to near 90F. At approximately 520pm I noticed a surge of cooler air, now the winds are SE again, but the temp has dropped from 89F to 75F which is what it is presently. The cumulus towers apparently hit the cap and go nowhere. Maybe with this surge of the front back to the SW it might let us get in on some developing thunderstorms to our north.