Alert archive / Nebraska / Mesoscale Discussions in 2003

Mesoscale Discussion 486

April 18, 20034 states

The Storm Prediction Center issued this mesoscale discussion at Apr 18, 2003, 5:15 PM CDT for 4 states. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Apr 18, 2003, 5:15 PM CDT (22:15 UTC)
Expired: Apr 18, 2003, 6:45 PM CDT
In force: 90 min
Issued by: the Storm Prediction Center

All 31 counties

Fremont County, IA, Atchison County, KS, Brown County, KS, Doniphan County, KS, Jackson County, KS, Jefferson County, KS, Nemaha County, KS, Shawnee County, KS, Andrew County, MO, Atchison County, MO, Buchanan County, MO, Holt County, MO, Butler County, NE, Cass County, NE, Gage County, NE, Hamilton County, NE, Howard County, NE, Johnson County, NE, Lancaster County, NE, Merrick County, NE, Nance County, NE, Nemaha County, NE, Otoe County, NE, Pawnee County, NE, Polk County, NE, Richardson County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE, York County, NE

The radar

The Omaha radar (KOAX), 123 km from the middle of the area, began a volume at 22:18 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 127Apr 18, 6:20 PM CDT

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 10.3 hours before the alert went out and 122 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: 637 m above ground
0-6 km bulk shear: 47 kt
0-1 km storm-relative helicity: 46 m²/s²
0-3 km storm-relative helicity: 120 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

000 
ACUS11 KWNS 182216
SWOMCD
SPC MCD 182215 
MOZ000-KSZ000-IAZ000-NEZ000-182345-

MESOSCALE DISCUSSION 0486
NWS STORM PREDICTION CENTER NORMAN OK
0515 PM CDT FRI APR 18 2003

AREAS AFFECTED...SERN NEB NERN KS EXTREME NWRN MO AND EXTREME
SWRN IA

CONCERNING...TORNADO WATCH 126...

VALID 182215Z - 182345Z

...A TORNADO OR TWO IS STILL POSSIBLE ACROSS THE AREA THIS
EVENING...

VSBL SATELLITE SHOWS ACCAS BECOMING BETTER DEFINED JUST NORTHEAST
OF MHK NWD INTO EXTREME SERN NEB.  WARM FRONT HAS JUMPED TO THE
NERN KS/SERN NEB BORDER WITH MHK TEMPERATURE IN THE LOWER 80S. 
SURFACE CONVERGENCE HAS SHIFTED NEWD COINCIDENT WITH THE ACCAS
AND AS TEMPERATURES WARM A COUPLE MORE DEGREES...TSTMS SHOULD
INITIATE IN THE BIE-TOP REGION.  LATHROP MO PROFILER DEPICTS A
HIGHLY VEERED PROFILE WITH 0-3 KM STORM RELATIVE HELICITY VALUES
OVER 400 M2/S2.  GIVEN VERY STRONG DEEP LAYER SHEAR...TSTMS WILL
TAKE A WHILE TO MATURE INTO SUPERCELLS...ESPECIALLY GIVEN
SOMEWHAT WEAK BUOYANCY.  HOWEVER...AS THE TSTMS MOVE TOWARD THE
HIGHER HELICITY VALUES...A TORNADO OR TWO ARE POSSIBLE ALONG WITH
LARGE HAIL.

FARTHER TO THE NORTH AND WEST...VORTICITY MAX IS MOVING ENEWD
INTO CNTRL NEB...PROGGED TO MOVE TOWARD THE OMA REGION LATER THIS
EVENING.  WHILE AN ISOLD TORNADO IS POSSIBLE BENEATH THIS VORT
FOR A COUPLE MORE HOURS...TSTMS SHOULD BECOME MORE ELEVATED IN
NATURE AS THEY MOVE NORTH OF THE WARM FRONT WITH MAINLY A LARGE
HAIL THREAT.  IF THE STORMS MAINTAIN INTENSITY OR INCREASE...A
NEW WW MAY BE REQUIRED FARTHER NORTH ACROSS ECNTRL NEB.

..RACY.. 04/18/2003

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

ATTN...WFO...EAX...OAX...TOP...GID...

38849578 39329612 39759646 40159692 40459740 40849810
41299895 41689821 41369645 40829548 39579442

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 18, 3:50 PM CDT	Tornado Watch	SPC	Fremont, Mills	6 hr
Apr 18, 6:20 PM CDT	Severe Thunderstorm Watch	SPC	Crawford, Harrison, Ida, Monona, Pottawattamie, Sac and 2 more	6 hr
Apr 18, 6:14 AM CDT	Mesoscale Discussion	SPC	Clay, Cloud, Dickinson, Ellsworth, Geary, Harvey and 13 more	2 hr
Apr 18, 2:52 PM CDT	Mesoscale Discussion	SPC	Atchison, Brown, Clay, Cloud, Coffey, Douglas and 15 more	113 min

Nearby

Mesoscale Discussions in Nebraska, 2003 Mesoscale Discussions in Kansas, 2003 Mesoscale Discussions in Missouri, 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.