High flood potential for Missouri drainage system as warmth replaces the winter deep freeze and melts heavy snow pack

[Roger Smith]

The title is pretty much the post. There is a widespread 1 to 2 foot snow pack in the Dakotas, Minnesota, Montana, Wyoming and southern prairies of Canada. 

Guidance showing clear potential for very warm weather to develop after this weekend with highs into the 70s and low 80s over the snow covered areas. Would expect the Missouri to start filling up gradually all month and it could lead to severe downstream flooding by May and or June.

The Mississippi drainage may also increase levels fairly quickly although there is a smaller percentage of that basin currently snow covered. 

Further north the Red and Assiniboine may go into flood stage later this month with the usual problems for North Dakota and Manitoba. 

The past six weeks have been very cold with frequent snowfalls; Fargo ND has seen almost 70" for the season of which about 30" has fallen since March 1st. Grand Forks ND is similar. Snow cover maps show snow packs of 40-60 cm or 16-24 inches fairly widespread in the upper Missouri drainage, parts of Minnesota and all of the Red-Assiniboine drainage area. Severe flooding seems difficult to avoid especially if this warmth ends with rainfalls.   

[Roger Smith]

Rapid snow melt underway now, visible satellite shows bare ground in eastern MT and western ND and temps currently 77 F, snow remains over central and eastern ND, northeast SD, temps near 40 F. Further west, rain across parts of WA state into southeast BC, at my location current weather rain, dense fog and 47F. Snow melt here has increased from gradual to moderately fast and creeks are near bankfull status. Would imagine a lot of the snow removal over Dakotas is evaporation (sublimation) rather than runoff but even so, rivers will collect the equivalent of 1-2" of liquid and with ice jam potential some flooding may occur on smaller rivers soon. 

I was reading elsewhere that winter wheat crop in southern/central plains is largely a failure due to drought. While it has been cold and snowy further north, March and early April in western KS bone dry and more variable in temperatures. 

 

 

[Roger Smith]

Amazing temperature difference today, 91F at Huron SD and 43F at Aberdeen SD a few miles further north, almost entirely due to snow pack which has now been removed from all but northeast corner of SD and most of eastern two thirds of ND. Also currently 88F in southwest ND and mostly 40s in eastern ND. KBIS has lost about half its snow pack which was 18" earlier on the weekend. The same effects are evident in the southern prairies, where we find low 70s in border regions of SK and mid to high 30s in s MB. 

Rain has turned to wet snow here and we ended up with about 1.5" of rain, local creeks produced some minor flooding and are running near flood stage still. Snow line in this region has receded up to 2500' elevation from 1500' a few days ago (Columbia River valley is at about 1200' locally and was snow free in mid-March).