NWS Flood Summary

Unseasonably Warm Temperatures in Pacific Northwest

Unseasonably warm temperatures have caused significant higher level snowmelt across Oregon, Washington, Idaho and Montana. These warm conditions are expected to continue through most of this week as a high pressure system dominates the area. Many rivers and creeks across the area are rising to and above flood stage.

Urban and Small Stream Flood Advisories and/or Flash Flood Warnings were issued during the past 24 hours for locations including:

(in alphabetical order, by state)

• Arizona:
• Monday: Persistent rains in a remote desert region off Interstate 10 caused some minor flooding as a Small Stream Flood Advisory was issued for the area 6 miles east of Quartzsite in the vicinity of Mitchell Mine Road.

• Montana:
• Friday: Flathead County.
• Warm temperatures continuing through the weekend will cause snowmelt runoff and keep the Little Bitterroot River running high.
• Saturday: Flathead County.
• The Small Stream Flood Warning continues in effect for Ashley Creek and the Bitterroot River.

• Sunday: Flathead County.
• The Small Stream Flood Warning continues in effect for Ashley Creek and the Bitterroot River. Unseasonable warm temperatures will persist through this week. This will allow significant snowmelt at the higher elevations resulting in continued increases on the rivers and creeks throughout northwest Montana.
• Monday: Flathead, Lincoln and Sanders Counties.
• Unseasonably warm temperatures persisting through the week will allow significant snowmelt and continued increases on the rivers and creeks throughout northwest Montana.

• Texas:
• Friday: Arkansas, Bastrop, Bee, Calhoun, Dewitt, Duval, Fayette, Goliad, Jackson, Jim Wells, Kleberg, Lavaca, Live Oak, Matagorda, Nueces, Refugio, San Patricio and Victoria Counties.
• Continued heavy rain from showers and thunderstorms drenched portions of South Texas Friday. The Midfield area in Matagorda County received more than 8 inches of rain. Rainfall rates were recorded at from 1 to 2 inches per hour, and street flooding was reported in Rio Grande City.

The Red River continues its fall. It will a week or more before some locations return to within banks. Even after streams in the Red River basin fall below flood stage, low areas will remain wet for an additional period.

A Flood Warning continues on the Missouri River from Omaha to below Rulo in eastern Nebraska and western Iowa. The river continues to overflow lowlands from the Omaha area downstream to Rulo. The river is expected to remain high through next week as releases from upstream Missouri River dams continue at high levels. At Atchinson and St. Joe Missouri, the river is expected to remain above flood stage for the next week or more, while other locations are expected to drop below flood stage by mid week.

The Mississippi River continues to remain near or slightly above flood stage at a few locations, including Hannibal, Louisiana and Clarksville Missouri.

Other rivers and streams with locations either above flood stage or expected to rise above flood stage include:

(in alphabetical order, by state)

• Alabama: the Tombigbee River.

• Arkansas: the Ouachita River.

• Georgia: the Savannah River.

• Idaho: the St. Joe, Snake, Henrys Fork and Portneuf Rivers.
• Warm conditions have allowed snowmelt to continue across the higher elevations of North Idaho. Although daily fluctuations of river levels will be apparent, the general trend is for rising conditions through this week.

• Iowa: the Wapsipinicon River.

• Louisiana: the Atchafalaya, Ouachita and Pearl Rivers, Bayou Bodcau Lake and Red Chute Bayou.
• A very slow fall on the Atchafalaya at Morgan City continues, with the river not expected to drop below flood stage until May 29th.

• Minnesota: the Minnesota River.
• The Minnesota River is dropping to near flood stage.

• Mississippi: the Pearl River.

• Montana: the Fisher, Yaak, Shields, Bitterroot and St. Regis Rivers.
• Rivers in western Montana are on the rise due to unseasonably warm temperatures causing significant snowmelt in the higher elevations. This trend is expected to continue throughout this week as high pressure dominates bringing sunny skies and above normal temperatures.

• North Dakota: the Souris River.
• River levels at Foxholm, Towner, Bantry and Westhope remain steady but continued above flood stage.

• Oregon: the Imnaha and Grande Ronde Rivers.
• Above normal temperatures continue to cause rapid snowmelt in the Wallowa and Blue Mountains through mid week. The snow packs are still above seasonal normals and runoff will continue to cause rivers in northeast Oregon to rise.

• South Carolina: the Great Pee Dee and Lower Santee Rivers.
• These rivers are expected to drop below flood stage today.

• South Dakota: the middle and lower James and Big Sioux Rivers.
• The James river is falling very slowly, at about a tenth of a foot a day. The river remains 4 to 5 feet above flood stage and will remain above flood stage for an extended period.
• The Big Sioux River below the Hamlin/Brookings County line has started to drop at a faster pace this past weekend. This was due to the mostly dry and windy conditions that prevailed. The river is about a foot above flood stage and should be back within its banks in 7 to 10 days.

• Texas: the Angelina, Neches, Sabine and Trinity Rivers.

• Washington: the Naches and Spokane Rivers.

Joanna Dionne

Comments are welcome at HIC@noaa.gov

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