Alert archive / Iowa / Flash Flood Watches in 2015

Flash Flood Watch 5, NWS Sioux Falls, SD

August 18, 2015Union County, South Dakota; 11 counties in Iowa; 5 counties in Minnesota

NWS Sioux Falls, SD issued this flash flood watch at Aug 18, 2015, 3:18 AM CDT for Union County, South Dakota; 11 counties in Iowa; 5 counties in Minnesota. It took effect at Aug 18, 2015, 7:00 AM CDT. It was in force for 6 hr.

The area

The counties it named.

The facts

Issued
Aug 18, 2015, 3:18 AM CDT (08:18 UTC)
In effect from
Aug 18, 2015, 7:00 AM CDT
Expired
Aug 18, 2015, 12:41 PM CDT
In force
6 hr
Issued by
NWS Sioux Falls, SD
Flood severity
None

Counties Buena Vista County, IA, Cherokee County, IA, Clay County, IA, Dickinson County, IA, Ida County, IA, Lyon County, IA, O'Brien County, IA, Osceola County, IA, Plymouth County, IA, Sioux County, IA, Woodbury County, IA, Cottonwood County, MN, Jackson County, MN, Murray County, MN, Nobles County, MN, Rock County, MN, Union County, SD

The radar

The Sioux Falls radar (KFSD), 93 km from the middle of the area, began a volume at 08:19 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, 8.3 hours before the alert went out and 215 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, Omaha, NE at 00:00Z on 2015-08-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 83 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, Omaha, NE at 00:00Z on 2015-08-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 80 square meters per square second.193958Sfc1 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
83 J/kg
Mixed-layer CIN
-271 J/kg
Mixed-layer LCL
937 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
80 m²/s²
0-3 km storm-relative helicity
271 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.2

Open this sounding in Storm Lab

What forecasters said that day

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

NWS Sioux Falls, SD wrote its last area forecast discussion before this flash flood watch went out at Aug 17, 10:33 PM CDT, 4 hours 45 minutes earlier.

Area forecast discussion, Aug 17, 10:33 PM CDT, 4 hours 45 minutes before
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Hazardous weather outlook, Aug 17, 5:22 AM CDT, 21 hours 56 minutes before
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
522 AM CDT MON AUG 17 2015

SDZ038>040-050-052>055-057>061-063>065-181030-
BEADLE-KINGSBURY-BROOKINGS-GREGORY-JERAULD-SANBORN-MINER-LAKE-
BRULE-AURORA-DAVISON-HANSON-MCCOOK-CHARLES MIX-DOUGLAS-HUTCHINSON-
522 AM CDT MON AUG 17 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
SOUTH DAKOTA...SOUTH CENTRAL SOUTH DAKOTA AND SOUTHEAST SOUTH
DAKOTA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED THROUGH THIS
EVENING...BECOMING MORE WIDESPREAD OVERNIGHT. SEVERE WEATHER IS
NOT EXPECTED AT THIS TIME...BUT INDIVIDUAL STRONG CELLS COULD
PRODUCE SOME ISOLATED HEAVY RAIN OVER A FEW SPOTS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

RAINFALL WITH EMBEDDED THUNDERSTORMS ARE EXPECTED THROUGH TUESDAY
NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY NOT BE NEEDED TODAY OR TONIGHT.

MNZ071-072-080-097-098-SDZ056-062-066>070-181030-
LINCOLN MN-LYON MN-MURRAY-PIPESTONE-ROCK-MOODY-MINNEHAHA-TURNER-
LINCOLN SD-BON HOMME-YANKTON-CLAY SD-
522 AM CDT MON AUG 17 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MINNESOTA...EAST CENTRAL SOUTH DAKOTA AND SOUTHEAST SOUTH DAKOTA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED THROUGH THIS
EVENING...BECOMING MORE WIDESPREAD OVERNIGHT. SEVERE WEATHER IS
NOT EXPECTED AT THIS TIME...BUT INDIVIDUAL STRONG CELLS COULD
PRODUCE SOME ISOLATED HEAVY RAIN OVER A FEW SPOTS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

WIDESPREAD RAINFALL WITH EMBEDDED THUNDERSTORMS ARE EXPECTED
THROUGH TUESDAY NIGHT. THERE IS A MARGINAL RISK OF SEVERE STORMS
TUESDAY AFTERNOON AND EVENING...AND ADDITIONAL HEAVY RAINFALL IS
ALSO POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY NOT BE NEEDED TODAY OR TONIGHT.

IAZ001>003-012>014-020>022-031-032-MNZ081-089-090-NEZ013-014-
SDZ071-181030-
LYON IA-OSCEOLA-DICKINSON-SIOUX-O'BRIEN-CLAY IA-PLYMOUTH-CHEROKEE-
BUENA VISTA-WOODBURY-IDA-COTTONWOOD-NOBLES-JACKSON-DIXON-DAKOTA-
UNION-
522 AM CDT MON AUG 17 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTHWEST
IOWA...SOUTHWEST MINNESOTA...NORTHEAST NEBRASKA AND SOUTHEAST
SOUTH DAKOTA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED THROUGH THIS
EVENING...BECOMING MORE WIDESPREAD OVERNIGHT. SEVERE WEATHER IS
NOT EXPECTED AT THIS TIME...BUT INDIVIDUAL STRONG CELLS COULD
PRODUCE SOME ISOLATED HEAVY RAIN OVER A FEW SPOTS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

WIDESPREAD RAINFALL WITH EMBEDDED THUNDERSTORMS IS EXPECTED
THROUGH TUESDAY NIGHT. THERE IS A SLIGHT RISK OF SEVERE STORMS
TUESDAY AFTERNOON AND EVENING...AND ADDITIONAL HEAVY RAINFALL IS
ALSO POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE THIS AFTERNOON AND EVENING.

The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 18, 4:19 AM CDTSpecial Weather StatementFSDGregory41 min
Aug 18, 4:41 AM CDTSevere Thunderstorm WarningFSDCharles Mix, Gregory49 min
Aug 18, 11:52 AM CDTRiver Flood WarningFSDWoodbury7 days

Nearby

Flash Flood Watches in Iowa, 2015Flash Flood Watches in Minnesota, 2015Flash Flood Watches in South Dakota, 2015Every flash flood watch in 2015

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.