Alert archive / Iowa / Mesoscale Discussions in 2003

Mesoscale Discussion 489

April 18, 200330 counties in Iowa; 11 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Apr 18, 2003, 7:48 PM CDT for 30 counties in Iowa; 11 counties in Nebraska. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued: Apr 18, 2003, 7:48 PM CDT (00:48 UTC)
Expired: Apr 18, 2003, 9:15 PM CDT
In force: 87 min
Issued by: the Storm Prediction Center

All 41 counties

Adair County, IA, Audubon County, IA, Boone County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Crawford County, IA, Dallas County, IA, Greene County, IA, Guthrie County, IA, Hamilton County, IA, Hardin County, IA, Harrison County, IA, Ida County, IA, Jasper County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monona County, IA, Monroe County, IA, Polk County, IA, Pottawattamie County, IA, Sac County, IA, Shelby County, IA, Story County, IA, Warren County, IA, Webster County, IA, Woodbury County, IA, Burt County, NE, Butler County, NE, Colfax County, NE, Cuming County, NE, Dodge County, NE, Douglas County, NE, Madison County, NE, Saunders County, NE, Stanton County, NE, Thurston County, NE, Washington County, NE

The radar

The Omaha radar (KOAX), 94 km from the middle of the area, began a volume at 00:48 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

Omaha, NE (KOAX), launched 00:00Z, 0.8 hours before the alert went out and 95 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 588 m above ground
0-6 km bulk shear: 68 kt
0-1 km storm-relative helicity: 208 m²/s²
0-3 km storm-relative helicity: 254 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

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

325 
ACUS11 KWNS 190048
SWOMCD
SPC MCD 190048 
IAZ000-NEZ000-190215-

MESOSCALE DISCUSSION 0489
NWS STORM PREDICTION CENTER NORMAN OK
0748 PM CDT FRI APR 18 2003

AREAS AFFECTED...NERN NEB INTO CNTRL IA

CONCERNING...SEVERE THUNDERSTORM WATCH 127...

VALID 190048Z - 190215Z

A STRONG/SEVERE TSTM HAS DEVELOPED INVOF OLU AND APPEARS TO HAVE
DEVELOPED WITHIN SMALL WARM SECTOR WEDGE BETWEEN RETREATING WARM
FRONT AND DRY LINE.  THIS TSTM MAY PRODUCE LARGE HAIL OR POSSIBLY
A TORNADO IN THE NEXT HOUR...BUT SHOULD BECOME ROOTED ABOVE THE
FRONTAL INVERSION AS IT MOVES TOWARD EET.

OTHERWISE...SLY LLJ AXIS HAS REDEVELOPED ACROSS MO...WITH TSTMS
INCREASING ON THE NOSE OF THE JET AND NORTH OF THE WARM FRONT
ACROSS CNTRL IA. TRAJECTORIES SUGGEST PARCELS ARE ORIGINATING
FROM NEAR THE MO/KS BORDER AND MUCAPE VALUES ARE IN THE 500-750
J/KG RANGE...BASED OFF THE 00Z OAX RAOB.  SHEAR IN THE CAPE
BEARING LAYER WOULD BE SUFFICIENT FOR ORGANIZED SEVERE
STORMS...BUT SOMEWHAT WEAK BUOYANCY ATOP THE BOUNDARY LAYER WOULD
LIMIT THE SEVERE THREAT TO MARGINALLY SEVERE HAIL.  IF ACTIVITY
BECOMES STRONGER THAN ANTICIPATED...A WW MAY BE NEEDED ACROSS
CNTRL IA.


..RACY.. 04/19/2003

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

ATTN...WFO...DVN...DMX...FSD...OAX...

41959782 42559610 42419318 41529240 40969247 41239598
41079707

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 18, 7:33 PM CDT	Mesoscale Discussion	SPC	Fremont, Mills, Page, Taylor	57 min
Apr 18, 9:56 PM CDT	Mesoscale Discussion	SPC	Crawford, Harrison, Ida, Monona, Pottawattamie, Sac and 2 more	64 min
Apr 19, 12:15 PM CDT	Mesoscale Discussion	SPC	Benton, Black Hawk, Bremer, Buchanan, Cedar, Clinton and 20 more	3 hr

Nearby

Mesoscale Discussions in Iowa, 2003 Mesoscale Discussions in Nebraska, 2003 Every mesoscale discussion in 2003

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.