Lala Approaching Hawaii; Flash Flooding Risks; Excessive Heat

Lala, may become a hurricane, is expected to impact Hawaii this weekend. Heavy rainfall, strong winds, dangerous surf and localized flooding are expected. Heavy rainfall and flash flooding concerns from the mid-Mississippi Valley, Ohio Valley into the central Appalachians continues, with the threat shifting toward the mid-Atlantic later this weekend. Record heat continues for areas of the South. Read More >

Overview

Through the day of April 1, a warm front lifted north and left much of the area in a warm, moist, and increasingly unstable airmass. This instability combined with strong vertical wind shear to support multiple waves of severe thunderstorms that tracked along and south of I-70 from the evening of April 1 through the early morning of April 2. Through the evening, thunderstorms took the form of isolated supercells producing large hail up to golf ball size (1.75" diameter) and hen egg size (2" diameter) and isolated damaging winds near the Missouri River into the western and northern St. Louis metropolitan area in addition to a brief EF0 tornado in Chesterfield, MO. Later into the evening and overnight, a gradual transition to clusters and lines of thunderstorms occurred accompanied by hail up to quarter size (1" diameter) and damaging winds. Lastly, these multiple rounds of thunderstorms, some with sustained heavy rain from training, yielded narrow swaths of 2–4" of rainfall which led to some instances of flash flooding primarily in the urbanized St. Louis metropolitan area.

A loop of KLSX radar data from the evening of April 1 through the early morning of April 2.

Tornado
Wind & Hail

Tornadoes

Tornado - Chesterfield, MO
ST. LOUIS COUNTY

Date	4/01/2024
Time (Local)	6:32 PM - 6:35 PM
EF Rating	EF0
Est. Peak Winds	85 mph
Path Length	2.01 miles
Max Width	332 yards
Injuries/Deaths	0/0
Summary: An EF0 tornado with peak winds of 85 mph touched down just northeast of the Interstate 64 and Highway 340 interchange. The tornado traveled 2 miles east-northeast for approximately 3 minutes before lifting just west of Highway 141. Several tree limbs were damaged with minor damage to the roofs of multiple residences.

Track Map


6:34 p.m. Radar Reflectivity	6:34 p.m. Radar Velocity	Snapped Tree near Appalachian Trail	Roof Damage near Appalachian Trail

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Wind & Hail:

Wind

Straight-line winds were responsible for damage to trees and power poles near Bonne Terre, Missouri and Chester, Illinois. There was also wind damage in western St. Louis County independent of the Chesterfield EF0 tornado.


Downed Power Poles Chester, IL Photo Credit: Sherri Fortman	Uprooted Tree Bonne Terre, MO	Snapped Tree Bonne Terre, MO	Uprooted Trees Chesterfield, MO

Hail

Golf ball (1.75") to hen egg (2.00") sized hailstones coated the ground in east-central Missouri including portions of the St. Louis metropolitan area.


Golf Ball Sized Hail Wardsville, MO Photo Credit: Sam Fleury	Quarter Sized Hail St. Charles, MO Photo Credit: Joseph Meyer	Half Dollar Sized Hail Harvester, MO Photo Credit: Philip Perrey	Golf Ball Sized Hail Wardsville, MO Photo Credit: Barry Gipe