Hydro Discussion and Red River Basin Spring Flood Talking Points - April 9th 2013 edition.
[corrected last line on 4/10/2013]
[corrected last line on 4/10/2013]
The overall hydrologic situation is still largely status quo from our April 4th Hydrologic Discussion.
There has been an additional measure of snow ripening and snowmelt across the Red River and Devils Lake Basins, so that there are more large areas of open/bare ground, mainly in east central ND counties and the southeastern ND uplands. There is still a substantial amount of snowpack across the far southern basin, north of Grant County and closer into the Red River, as well across the northern counties along the US-Canadian border.
In the middle Sheyenne River Basin and along the smaller tributary streams in east-central ND, where snowmelt has been most evident, there are scattered open areas where snowmelt water might be infiltrating into the top few inches of soil, making for mud on top of the still frozen deeper soil. However, large scale soil thaw has not yet occurred anywhere in the valley, and future frost action may make some of this soil moisture available for runoff into area ditches and streams. Meanwhile, ditch networks in these central basin locations are fairly open and available to handle whatever runoff may materialize. These are also areas where there has been a lesser concern for substantial flooding.
In the far southern Red River Basin, from southern Cass and Clay Counties into Richland and Wilkin Counties, there remains a substantial and very wet snowpack, with ditches filling from some localized melt and runoff while area streams and river channels still struggling to thaw and open up. Northern Traverse County has seen portions of the Mustinka River Basin (which empties into Lake Traverse – a regulated USACE reservoir) showing the beginnings of significant runoff and some overland flood issues. Flows were beginning to open up in the headwaters of the Rabbit and Buffalo Rivers and other smaller tributaries in west-central Minnesota as well. However, most all of this thaw and runoff will be stalled through the middle of this week, when temperatures again show daytime warming back above the freezing mark. Here, the risk for substantial overland and riverine flooding remains high. The likely runoff period looks like it will extend well into middle and late April.
Far northern border counties have yet to see substantial melt and runoff even begin, and snowpack ripening there is further hampered by the abnormally cold temperatures… averaging 10 to 15 degrees below seasonal normals. Where snowpack has been showing signs of warming in these north border counties, the next cold wave has slammed the fledgling thaw cycle back down. These areas still face a risk for substantial risk overland and riverine flooding from late April into early May.
The near term weather forecast calls for a slight warming trend through the later part of this week into early next week, with overall temperatures still 5 to 10 degrees below seasonal normals. Seasonal normals for this time period would have daytime highs from the upper 40s in the north basin to the lower 50s in the far south basin with lows in the upper 20s to around the freezing mark. Instead, our forecast temperatures are expected to rise to near 40 in the far north by Saturday, and into the lower and middle 40s in the far southern Red River Basin… nearest the South Dakota border. Nighttime low temperatures are still expected to drop below to well below freezing in most all locations.
The current very cold weather pattern has succeeded in shunting a string of heavy precipitation storms well to the south of our basin and across the Central Plains states. The NOAA/NWS Climate Prediction Center does expect slight warming through this weekend and into next week along with a general shift in this very active storm track, bringing it closer into our southern Red River Basin and perhaps even into the northern basin by next week. Thus the risk for substantial spring runoff flooding is flavored with existing snowmelt and with the possibility for additional precipitation through the runoff cycle.
Looking at the forecast points on the mainstem Red River, the following crests and dates are for the latest significant (within the top 15 crests) floods in which snow melt appeared to be the most significant contribution. Rainfall may have also contributed; however, it was not the primary water source for the flood.
Forecast points (from south to north)
Wahpeton, ND 15.44 feet on April 14, 1979
Fargo, ND 34.93 feet on April 19, 1979
Halstad, MN 39.00 feet on April 22, 1979
East Grand Forks, MN 48.81 feet on April 26, 1979
Oslo, MN 38.00 feet on April 23, 1997*
Drayton, ND 43.66 feet on April 28, 1979
Pembina, ND 54.94 feet on April 26, 1997
*Note, USGS records for Oslo have a break in the data between 1973 and 1984.