Alert archive / California / Flash Flood Warnings in 1998

Flash Flood Warning 7, NWS Las Vegas, NV

July 20, 1998San Bernardino County, California

NWS Las Vegas, NV issued this flash flood warning at Jul 20, 1998, 2:09 AM PDT for San Bernardino County, California. It was in force for 111 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Jul 20, 1998, 2:09 AM PDT (09:09 UTC)
Expired
Jul 20, 1998, 4:00 AM PDT
In force
111 min
Issued by
NWS Las Vegas, NV
Area
Whole counties

County San Bernardino County, CA

The radar

The Edwards AFB radar (KEYX), 129 km from the middle of the area, began a volume at 09:08 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

Mercury/Desert R, NV (KDRA), launched 00:00Z, 9.2 hours before the alert went out and 198 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, Mercury/Desert R, NV at 00:00Z on 1998-07-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Mercury/Desert R, NV at 00:00Z on 1998-07-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 91 square meters per square second.1939Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
4616 m above ground
0-6 km bulk shear
13 kt
0-1 km storm-relative helicity
91 m²/s²
0-3 km storm-relative helicity
118 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 
TTAA00 KLAS 200927 COR
FFWLAS
CAC071-NVC003-201105-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING...CORRECTED
NATIONAL WEATHER SERVICE LAS VEGAS NV
209 AM PDT MON JUL 20 1998


*  FLASH FLOOD WARNING FOR
   CENTRAL AND SOUTHERN CLARK COUNTY IN SOUTHERN NEVADA
   EXTREME EASTERN SAN BERNARDINO COUNTY IN SOUTHEASTERN CALIFORNIA

*  UNTIL 400 AM PDT

*  SOME LOCATIONS AFFECTED
   ALL OF THE LAS VEGAS VALLEY INCLUDING NORTH LAS VEGAS
   HENDERSON...BOULDER CITY...AND THE LAS VEGAS METRO AREA.
   AND THE TOWNS OF PRIMM...NELSON...SEARCHLIGHT...COTTONWOOD
   COVE...GOODSPRINGS...SLOAN...CAL NEV ARI...SANDY...
   LAUGHLIN...BULLHEAD CITY...BAKER...HALLORAN SPRINGS...
   MOUNTAIN PASS AND NIPTON

*  THUNDERSTORMS OVER CENTRAL CLARK COUNTY ARE STARTING TO TREK
   SOUTH AND SOUTHWESTWARD TOWARD SOUTHERN CLARK COUNTY AND
   EXTREME EASTERN SAN BERNARDINO COUNTY.  THESE STORMS HAVE A
   HISTORY OF FLOODING IN CENTRAL NEVADA AND WILL LIKELY CAUSE
   FLASH FLOODING IN THE WARNING AREA.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODS AND FLASH FLOODS. IF FLASH FLOODING IS OBSERVED...
ACT QUICKLY. MOVE UP TO ESCAPE FLOOD WATERS. DO NOT STAY IN AREAS
SUBJECT TO FL$OODING WHEN WATER BEGINS RISING. IT IS VERY DIFFICULT
AT NIGHT TO TELL HOW MUCH WATER IS ON ROADS. MOTORISTS SHOULD NOT
DRIVE THROUGH WATER OF UNKNOWN DEPTH.

CORDERO

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Las Vegas, NV wrote its last area forecast discussion before this flash flood warning went out at Jul 20, 2:07 AM PDT, 2 minutes earlier.

Area forecast discussion, Jul 20, 2:07 AM PDT, 2 minutes before
MOJAVE DESERT/SOUTHERN GREAT BASIN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAS VEGAS NV
900 AM PDT MON JUL 20 1998

SYNOPSIS...THE UPPER LEVEL HIGH PRESSURE SYSTEM OVER SOUTHEAST UTAH
WILL MOVE VERY LITTLE THROUGH TUESDAY. THIS WILL ALLOW FOR MONSOONAL
MOISTURE TO FLOW NORTHWESTWARD ACROSS THE MOJAVE DESERT AND SOUTHERN
GREAT BASIN CONTINUING THE CHANCE OF LATE DAY THUNDERSTORMS.

DISCUSSION...UPPER RIDGE THAT HAS BEEN DOMINATE ACROSS THE AREA THE
LAST FEW DAYS HAD SHIFTED EAST TOWARD THE FOUR CORNERS AREA. THIS HAS
ALLOWED THE MOIST MONSOONAL FLOW TO SURGE NORTH INTO THE CWA. LOW
LEVEL MOISTURE HAD INCREASED...WITH LOW LEVEL DEWPOINTS INTO THE 50S
ACROSS THE NORTH AND 60S ACROSS THE SOUTH. MCS FROM LATE LAST NIGHT
AND EARLY THIS MORNING HAD DECREASED WITH A LEFT OVER CIRCULATION
CENTER APPARENT ACROSS SOUTHERN NEVADA. LOOKS LIKE THE 12Z ETA DID A
BETTER JOB OF INITIALIZING THIS FEATURE. VORT WILL LIFT NORTH-
NORTHWESTWARD THROUGH THE DAY TODAY AND HELP TO INITIATE FURTHER
CONVECTION. BEST INSTABILITY WAS PROGGED ACROSS SOUTHERN PORTIONS OF
THE CWA...WHERE LIFTED INDICES DROP TO -2. WILL BE MAKING SOME FIRST
PERIOD ADJUSTMENTS TO ZONES BASED ON CURRENT SATELLITE AND RA^DAR
TRENDS.

LAS 343. MATUSIEWICZ

The office that day

Everything else NWS Las Vegas, NV issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 20, 12:53 AM PDTSevere Thunderstorm WarningVEFSan Bernardino57 min
Jul 20, 3:45 AM PDTFlash Flood WarningVEFSan Bernardino2 hr

Nearby

Flash Flood Warnings in California, 1998Every flash flood warning in 1998

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.