Alert archive / Illinois / Mesoscale Discussions in 2004

Mesoscale Discussion 355

April 17, 200413 counties in Illinois; 5 counties in Wisconsin

The Storm Prediction Center issued this mesoscale discussion at Apr 17, 2004, 1:25 AM CDT for 13 counties in Illinois; 5 counties in Wisconsin. It was in force for 65 min.

The area

The outline as issued.

The facts

Issued
Apr 17, 2004, 1:25 AM CDT (06:25 UTC)
Expired
Apr 17, 2004, 2:30 AM CDT
In force
65 min
Issued by
the Storm Prediction Center

Counties Boone County, IL, Carroll County, IL, DeKalb County, IL, DuPage County, IL, Jo Daviess County, IL, Kane County, IL, Lake County, IL, Lee County, IL, McHenry County, IL, Ogle County, IL, Stephenson County, IL, Whiteside County, IL, Winnebago County, IL, Green County, WI, Kenosha County, WI, Lafayette County, WI, Rock County, WI, Walworth County, WI

The radar

The Milwaukee radar (KMKX), 96 km from the middle of the area, began a volume at 06:28 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

Davenport, (KDVN), launched 00:00Z, 6.4 hours before the alert went out and 125 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-pSkew-T log-p diagram, Davenport, at 00:00Z on 2004-04-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 428 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 00:00Z on 2004-04-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 35 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
428 J/kg
Mixed-layer CIN
-47 J/kg
Mixed-layer LCL
2694 m above ground
0-6 km bulk shear
39 kt
0-1 km storm-relative helicity
35 m²/s²
0-3 km storm-relative helicity
62 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.5

Open this sounding in Storm Lab

The text

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

625 
ACUS11 KWNS 170626
SWOMCD
SPC MCD 170625 
ILZ000-WIZ000-IAZ000-170730-

MESOSCALE DISCUSSION 0355
NWS STORM PREDICTION CENTER NORMAN OK
0125 AM CDT SAT APR 17 2004

AREAS AFFECTED...ERN IA/FAR SRN WI/NWRN-NRN IL

CONCERNING...SEVERE THUNDERSTORM WATCH 76...

VALID 170625Z - 170730Z

WW WILL BE ALLOWED TO EXPIRE AT 07Z AS SCHEDULED.  

OVERALL WEAKENING TREND IN ONGOING MCS ACROSS ERN IA IS EXPECTED TO
CONTINUE AS CLOUD BEARING SHEAR IS PROGGED TO DECREASE AS SHORT WAVE
TROUGH AND ASSOCIATED 50 KT SSWLY LLJ TRANSLATE ENEWD INTO LOWER MI
OVERNIGHT.  STRONG LOW-LEVEL WAA WILL...HOWEVER...SUPPORT
THUNDERSTORMS EWD ACROSS FAR SRN WI/NRN IL DURING THE NEXT 2-3
HOURS. THE STRONGEST STORMS...WITH AN ISOLATED SEVERE THREAT ARE
EXPECTED TO BE CO-LOCATED WITH AN MCV WHICH SHOULD LOCALLY ENHANCE
UPDRAFT STRENGTH/DEEP LAYER SHEAR FOR ORGANIZED STORMS.  HAIL/STRONG
WIND GUSTS WILL BE THE PRIMARY THREATS WITH THE STRONGEST
ACTIVITY...BUT MARGINAL NATURE OF SEVERE THREAT WILL PRECLUDE THE
ISSUANCE OF A NEW WW ACROSS NRN IL/SRN WI.

..PETERS.. 04/17/2004

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

ATTN...WFO...LOT...MKX...DVN...

42729040 42958971 42898786 42338760 41728813 41648938
41749009 42209038

Nearby

Mesoscale Discussions in Illinois, 2004Mesoscale Discussions in Wisconsin, 2004Every 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.