Alert archive / Wisconsin / Mesoscale Discussions in 2004

Mesoscale Discussion 1739

July 20, 200436 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Jul 20, 2004, 1:09 PM CDT for 36 counties in Wisconsin. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Jul 20, 2004, 1:09 PM CDT (18:09 UTC)
Expired: Jul 20, 2004, 3:15 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 36 counties

Adams County, WI, Barron County, WI, Buffalo County, WI, Calumet County, WI, Chippewa County, WI, Clark County, WI, Columbia County, WI, Dane County, WI, Dodge County, WI, Dunn County, WI, Eau Claire County, WI, Fond du Lac County, WI, Green County, WI, Green Lake County, WI, Jackson County, WI, Jefferson County, WI, Juneau County, WI, Lincoln County, WI, Marathon County, WI, Marquette County, WI, Monroe County, WI, Outagamie County, WI, Pepin County, WI, Portage County, WI, Rock County, WI, Rusk County, WI, Sauk County, WI, Taylor County, WI, Trempealeau County, WI, Walworth County, WI, Washington County, WI, Waukesha County, WI, Waupaca County, WI, Waushara County, WI, Winnebago County, WI, Wood County, WI

The radar

The La Crosse radar (KARX), 96 km from the middle of the area, began a volume at 18:10 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Green Bay/Straub, WI (KGRB), launched 12:00Z, 6.2 hours before the alert went out and 161 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 421 J/kg
Mixed-layer CIN: -65 J/kg
Mixed-layer LCL: 751 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 9 m²/s²
0-3 km storm-relative helicity: 55 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

002 
ACUS11 KWNS 201810
SWOMCD
SPC MCD 201809 
WIZ000-202015-

MESOSCALE DISCUSSION 1739
NWS STORM PREDICTION CENTER NORMAN OK
0109 PM CDT TUE JUL 20 2004

AREAS AFFECTED...NRN-ERN WI

CONCERNING...CONVECTIVE TRENDS 

VALID 201809Z - 202015Z

TSTMS SHOULD CONTINUE TO DEVELOP ACROSS NRN AND ERN WI THROUGH THE
AFTERNOON.  ISOLD DAMAGING WIND GUSTS/HAIL MAY OCCUR WITH THE
STRONGER TSTMS...BUT A WW IS NOT ANTICIPATED ATTM.

TSTMS HAVE BEGUN FORMING THIS AFTERNOON ALONG 1/ WEAK WARM FRONT AND
2/ DIFFERENTIAL HEATING BOUNDARIES SITUATED ACROSS NRN WI.  VSBL
IMAGERY ALSO SHOWS THE CU FIELD BEGINNING TO SHARPEN VCNTY LAKE
BREEZES IN ERN WI.  AIR MASS HAS BECOME ESSENTIALLY UNCAPPED AND
LOCALIZED CONVERGENCE WILL BE FAVORABLE FOR TSTM INITIATION THROUGH
THE AFTERNOON AS THE BOUNDARY LAYER CONTINUES TO HEAT. 

STEEPEST MIDLEVEL LAPSE RATES EXIST ALONG/WEST OF THE MS RVR PER
MORNING/CURRENT PROXIMITY RUC SOUNDINGS.  ALSO...VERTICAL SHEAR IS
GENERALLY AOB 25 KTS.  THESE MARGINAL PARAMETERS SUGGEST THAT THE
TSTMS WILL MAINLY BE MULTICELLS AND SOMEWHAT SHORT-LIVED.  ISOLD
STRONG TSTMS MAY PRODUCE MARGINALLY SEVERE WIND GUSTS OR HAIL... BUT
THE OVERALL SEVERE THREATS APPEAR SUCH THAT A WW WILL NOT BE
WARRANTED.

..RACY.. 07/20/2004

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...GRB...MKX...DLH...ARX...MPX...

42638963 43799031 44529226 45679235 45709083 45428929
43978809 42678811

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 5:35 PM CDT	Mesoscale Discussion	SPC	Dane, Green, Iowa, Lafayette, Rock, Walworth	55 min
Jul 20, 6:00 PM CDT	Severe Thunderstorm Watch	SPC	Dane, Grant, Green, Iowa, Jefferson, Lafayette and 2 more	4 hr
Jul 20, 6:08 PM CDT	Mesoscale Discussion	SPC	Dane, Green, Iowa, Lafayette, Rock, Walworth	2 hr

Nearby

Mesoscale Discussions in Wisconsin, 2004 Every mesoscale discussion in 2004

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.