Wayne Byers Show – Evening – Feb 27

Bismarck  (National Weather Service) The National Weather Service on February 27, 2020 issued an updated Spring Flood and Water Resources Outlook update for the Missouri and James River basins of North Dakota and covers the period from late February through late May.

This outlook is the second in the Spring Flood and Water Resources Outlook series and will be updated again on 12 March. After those updates, the NWS

will revert back to the regular monthly issuance on the fourth Thursday of each month.

…Flood Outlook Highlights…

James River Basin:

Only the James River basin locations of Pipestem Creek near Pingree, the James River near Grace City, and the James River at LaMoure, have a significantly above normal risk of spring flooding due to the current snowpack.

This above normal risk is the direct result of wet soils, full wetlands, and three plus inches of SWE (Snow-Water Equivalent) common over large areas of the James River and Pipestem Creek watersheds.

 

However, while risk remains high across the larger James River basin, it has diminished over the past several weeks due to a very benign weather pattern that has not increased the SWE content. In fact, small amounts of melting, evaporation, and sublimation have probably reduced the overall SWE in the basin ever so slightly.

The Prairie Pothole region:

Sheridan, Wells, Kidder, Stutsman, Logan, McIntosh and Dickey counties have enough SWE to suggest overland flooding will be a concern going into spring. Most of these wetlands are already near their normal late spring high water marks and runoff from melting snow and spring rains are going to raise some of them enough to close nearby roads. Some of these road closures are expected to last for weeks, or maybe even months.

 

Other areas in the Spring Report:

Northwest corner of North Dakota: Streams like the Little Muddy

River have a somewhat below normal, but certainly not zero risk

of significant flooding. Other small streams in the area, such

as the White Earth River, Little Knife River, and Deep Creek in

McLean county should also be considered of having at least some

risk of flooding this spring, even though it is below normal. While

this area has little SWE at this point due to a couple of warm

weeks in January and February, flood risk is largely due to well

frozen and wet soils that will enhance runoff from any heavy rains

that may fall in March.

 

Southwest quarter of North Dakota: Much of the early winter

snow has already melted, and existing SWE values tend to be less

than an inch to slightly over one inch. Again, this amount of SWE

is generally unremarkable but does sit on abnormally wet and frozen

soils. In fact, many rivers and streams south and west of the

Missouri River have already experienced runoff. This should help

lower the risk of ice jams going forward as there may not be enough

SWE left to raise the rivers high enough to mobilize river ice.

The potential for any early to mid-March rains provide the bulk

of the existing flood risk.

 

East of the Missouri River and south of Highway 200: Apple Creek

near Menoken and Beaver Creek near Linton are near normal risk for

flooding. Other area streams such as Burnt Creek, Hay Creek, and

Painted Woods Creek are also at a near normal risk of flooding.

 

Missouri River: New this spring is the inclusion of the Missouri

River near Williston in the extended streamflow predictive modeling.

Modeling results suggest a near normal risk of Minor flooding along

the Missouri River west of of Williston. This risk is consistent

with a now slightly above normal snowpack in the Yellowstone and

Missouri River basins of Montana. One of the items of interest not

included in the tables below is the overall runoff for the Missouri

and Yellowstone Rivers. The Missouri River dams have near 100% of

their combined flood storage available and are expected to be able

to fully handle the existing conditions. The combination of a

nominal plains snowpack and that in the upper basin would suggest

a relatively normal runoff event given normal spring rainfall.

The possibility of ice jams along the Yellowstone and Missouri

west of Williston are still a concern, but there is no reason to

believe they pose a greater threat this year than in any other normal

year. The Missouri River below Garrison, down into the Bismarck/Mandan

area, is already open from Garrison to south of Wilton. Given the

near term weather forecast of favorable weather conditions, the

southward retreat of ice cover will continue. It is likely that

the ice cover through the Bismarck/Mandan area will mostly be gone

during the second week of March.

…Current Conditions…

The general consensus is that western and central North Dakota`s

snowpack sits atop a crust of fairly wet and frozen soil. This

creates a nearly impermeable surface and can enhance runoff from

a given snowpack. Most western North Dakota rivers and streams,

while ice covered, have already received some runoff. This suggests

a strong possibility that their ice cover has been deteriorated

over the past few weeks. This tends to decrease, but not eliminate,

the risk of ice jam related flooding along those streams.

 

A person`s visual meausuring of the snow across the state may give

a somewhat misleading estimate for how much SWE is on the ground.

Compaction, melting with subsequent ponding of water in low areas,

and widespread brown ground can be deceiving. Water hidden as a thin

sheet of ice in low-lying areas will still be available during the

eventual spring melt for producing runoff.

 

…Weather Outlook…

The near term 6-10 and 8-14 day outlooks hint at a mixture of near

normal to maybe slightly above normal temperatures and precipitation

over the period. Looking farther into the future, the week 3-4

outlooks suggest a cooler and drier than normal pattern. However,

one should remember that by the middle of March, the average

daytime high temperature is above freezing for western and central

North Dakota. The one-month outlook covering March, puts the entire

state in the equal chances category for above normal, near normal,

and below normal temperature and precipitation. Even longer term,

the three-month outlook for March, April, and May has a slight

favoring of below normal temperatures and above normal precipitation

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