Flood Outlook for Red River Valley Remains GrimAny thoughts of optimism for the Red River Valley were quickly dashed Thursday when a new forecast showed that the risk of major flooding for the southern valley of North Dakota and Minnesota is increasing, despite relatively dry weather throughout most of the region in the last month.
By: Dave Kolpack, Associated Press
MOORHEAD, Minn. (AP) — Any thoughts of optimism for the Red River Valley were quickly dashed Thursday when a new forecast showed that the risk of major flooding for the southern valley of North Dakota and Minnesota is increasing, despite relatively dry weather throughout most of the region in the last month.
The cities of Fargo and Moorhead have begun filling millions of sandbags in anticipation of a third straight major flood. Thursday's report shows about a 35 percent chance the river will exceed the record levels posted in 2009, when the river crested at just under 41 feet in Fargo. That's up from 25 percent in the mid-February outlook.
"Well, the numbers keep going up so we need to keep preparing," said Mark Bittner, a Fargo city engineer who attended the weather service briefing. "We were hoping that it would settle down. I'm disappointed, but we just have to continue on."
The report gives an 80 percent chance of matching last year's crest of just under 37 feet, the sixth-highest flood on record. Bittner said there are plans to protect Fargo structures to 43 or 44 feet.
Michael Redlinger, the Moorhead city manager, said he was taking the recent numbers in stride.
"I think this really validates why we wanted to start early," Redlinger said. "A sandbag that's made on March 10 is lot better than a bag that's made on March 25."
When asked whether there were any favorable things in the report, weather service meteorologist Greg Gust simply said, "Ouch." Gust noted that the area might be helped by an expected gradual thaw, although there's a greater chance for significant rain if the flood continues into April.
Key factors for major flooding, including soil moisture, continue to be high, Gust said. Although most of North Dakota has remained dry in the last few weeks, a storm around President's Day added about 1 inch of moisture to the snowpack near the Red River headwaters south of Wahpeton.
The climate outlook calls for cooler and snowier conditions. A significant winter storm is expected to brush the southern valley next week. Models show the storm track shifting toward the Red River Valley by the third week of March.
The weather service said It's likely that the Red River in Fargo-Moorhead won't crest until at least the first week of April. The thaw cycle is expected to begin around March 20.
The outlook shows the risk of major flooding has decreased slightly in the northern Red River Valley and along the Sheyenne River from Valley City into Lisbon. The outlook is also improved in many Minnesota tributaries, including the Red Lake River in Crookston and the Roseau River in Roseau.
There's a slight decrease in the prediction for Devils Lake, but it remains almost certain to surpass the record level of 1,452.05 feet above sea level set last June 27. The outlook shows about an 80 percent chance the lake this year will break that mark by 2 feet, down from about a 90 percent chance in mid-February.
Devils Lake, located in northeastern North Dakota, has risen nearly 30 feet and quadrupled in size since the state's current wet cycle began in 1993. The flooding has swallowed up farm land and caused hundreds of millions of dollars in damage.
Residents along many rivers in western North Dakota are also on guard. Thursday's report shows a flood risk "well above average" for many locations on the James, Knife, Cannonball and Little Missouri rivers, as well as for the Little Muddy, Apple and Beaver creeks. The weather service said many areas need well-below-normal precipitation and a gradual melt to escape spring flooding.
The Souris River looping through north central North Dakota also remains a big concern because of the high amount of water in the snowpack, the weather service said. Flooding also is likely along the Des Lacs River.
Full flood forecast:
Cutting to the chase - an overview of the numbers (see page 3 for table):
In general, the risk of major to record scale flooding has increased only slightly across
the headwaters areas and the southern Red River Basin, basically Fargo-Moorhead and points
south. For most all other areas including the mid to upper Sheyenne sub-basin, the northern Red
River basin, and the Devils Lake sub-basin the risk has decreased slightly.
These changes are mostly due to the singular significant snow event, the Washington’s
Birthday Holiday Weekend (Feb 20-21) storm, which mainly impacted that extreme southern
basin area. Otherwise, the remainder of the basin received only minimal new snowfall.
Also, recent and more extensive aerial and ground snow surveys now indicate a slightly
lower snow water equivalent (SWE) across the Devils Lake Basin and the northern Red River
Basin than was previously determined, leading to slightly lower inflows expected there.
Key points for the Red River Basin, from south to north:
- All points along the Red River still have a better than 90 percent risk of major flooding.
- Wahpeton and Fargo, both now have a roughly 35 percent risk of exceeding 2009 flood
levels. [in 2009 Fargo hit a flood of record at 40.84 ft, Wahpeton hit 3rd place at 17.5 ft]
- The ND Wild Rice at Abercrombie has close to a 20 percent risk of 2009 scale flooding.
- The risk levels along the Sheyenne River from Valley City into Lisbon have been
reduced by nearly a foot. Past Lisbon into Kindred, West Fargo, and Harwood the flood risks
have remained near 2006 and 2009 levels.
- The mainstem Red River flood risk at Halstad has reduced slightly, while the risk along
the MN Wild Rice at Hendrum remains near 20 percent for exceeding 1997’s record [33.85 ft].
- Both Crookston (on the Red Lake River) and Grand Forks (at the confluence of the Red
and Red Lake Rivers) have had their flood risk levels reduced around a foot.
- In the north, Drayton and Pembina (on the Red River) have had their flood risks
reduced by about half a foot. Grafton (on the Park River) and Roseau (on the Roseau River)
have also had their flood risks reduced by about half a foot.
Key points for the Devils Lake Basin: This outlook still indicates that Devils Lake and Stump
Lake will likely rise (80 percent probability) to a new record height in excess of a 1454.1 ft
elevation, which is two feet above their previous record set last summer. These lakes could rise
(20 percent probability) to a height in excess of a 1455.1 feet, or three feet above their previous
record. Overall risk factors have been reduced slightly for this update, largely due to below
normal snowfall through February. [Creel Bay gauge at 1451.73 on 3/3/11]
What has occurred since Feb 17th:
From one half inch to an inch of moisture was added to the headwaters snowpack. This area received nearly double their normal February precipitation, whereas most of the rest of the basin received roughly one half inch below February normals. Temperatures have plummeted well below seasonal normals. The average temperature for February was roughly 3 degrees below normal across the area, and well below freezing. Whatever snowpack warming and ripening (nearing 32F melt temperature) had occurred in early February has been lost, as overall snowpack has now cooled back into the mid-teens.
What will be occurring over the next few days:
The Otter Tail River (below Orwell Dam), the Bois de Sioux River, and the Red River from Wahpeton to Fargo will be rising to near minor flood stage. Reservoir releases at Orwell Dam and White Rock Dam will be at peak levels for the next week or two as these reservoirs are drawn down to winter minimum levels to provide maximum spring snowmelt storage. The Otter Tail River will likely have some breakout flow in mainly rural areas. Only slight rises are expected on the Sheyenne River near Valley City, as Baldhill Dam releases are nearly stabilized and Lake Astabula is near its projected winter minimum level.
What is likely to happen from next week into late March:
Temperatures should remain well below seasonal normals through the first three weeks of March. High temperatures could sneak above freezing around the weekend of the 20th or later. Precipitation this first week of March will remain slight, with light snow chances today (Thursday) and again this weekend.
A more significant winter storm is expected to impact the central and northern plains around this coming Tuesday, March 8th. Current storm tracks suggest that heaviest snowfall could impact South Dakota and southern Minnesota, but brush the southern Red River Basin.
By the third week in March, the NOAA Climate Prediction Center (CPC) outlook projects the storm track to be more distinctly across the Red River Basin, with below normal temperatures and above normal snow as the most likely outcomes in our area.
The overall CPC climate outlook for February calls for cooler and snowier conditions, while this active storm pattern is expected to persist well into April and possibly May.
How this may affect the spring snowmelt (a climatologically probable scenario):
A favorable thaw cycle is one in which daytime temperatures rise above freezing, but drop back below freezing at night… allowing for a slow but steady melt and runoff.
If a gradual thaw cycle begins around or after March 20th, as longer-range weather projections now suggest, we would expect higher elevation, headwaters areas, to thaw and start to flow in that last week of March, while most mainstem Red River locations would remain cooler with the river still frozen and local runoff slower to begin.
Then, from the end of March into the first week of April, southern basin locations could be opened and flowing with flood crests moving first along southern basin tributaries and then along the mainstem Red from Wahpeton into Fargo.
Local snowmelt would also be increasing in the northern Red River Valley, so that from the first into the second week of April, northern basin tributaries would be opened and sending their flood crests towards the mainstem Red. Around this same time, the flood wave along the mainstem Red would likely be progressing north from Fargo into Grand Forks and points north. In such a scenario, far northern mainstem sites, from Oslo northward to the Canadian border, would remain in flood from late April into early May.
Meanwhile, throughout April, local runoff would be increasing across the Devils Lake Basin. From late April into early May, inflows into Devils Lake and Stump Lake would be reaching their peak and the lakes would rise most rapidly.
The later into April that such a flood may persist, the increased chance there is for an excessive spring rain event to occur. A warm and heavy rain onto frozen ground or snowcover during the runoff period would speed up the overall process and likely increase the severity of flooding.