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Spring Flood Outlook. National Weather Service Chanhassen - Twin Cities North Central River Forecast Center. March 6, 2014 craig.schmidt@noaa.gov 952-368-2542. Summary Up Front. Overall, the spring flood threat west of the Mississippi remains near or below historical average

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spring flood outlook
Spring Flood Outlook

National Weather Service

Chanhassen - Twin Cities

North Central River Forecast Center

March 6, 2014

craig.schmidt@noaa.gov

952-368-2542

summary up front
Summary Up Front
  • Overall, the spring flood threat west of the Mississippi remains near or below historical average
  • East of the Mississippi, the St. Croix, Chippewa and Eau Claire basins have a higher probability of flooding (50-60%)
    • Due to higher water content in the snowpack over WI/northeast MN
  • As always…the true threat lies in how the spring temperatures and rainfall hit us – currently, long range models show a good likelihood of below normal temperatures and rainfall
background precipitation since last briefing feb 19
Background: Precipitationsince last briefing (Feb 19)

Since last outlook: added .50 – 1.0 inch of water to the snowpack

Almost no melting

background precipitation last 30 days
Background: PrecipitationLast 30 Days

About 1 to 2 inches of water equivalent has fallen over eastern MN/ WI during the last 30 days

Less than one inch in western MN

Shown as percent of normal precipitation

Source of map: Regional Climate Centers

background precipitation dec jan feb percent of normal
Background: PrecipitationDec/Jan/Feb Percent of Normal

Winter precipitation has been well above normal north and east of MSP (4 to 7 inches)

Below normal over western MN (1 to 3 inches)

Source of map: Regional Climate Centers

background precipitation snow water equivalent swe
Background: PrecipitationSnow Water Equivalent (SWE)

SWE on the ground:

  • < 2 in. west and southwest
  • 3-4.5 in. MSP area
  • 4-6 in. WI portion
background precipitation snow water equivalent swe ranking
Background: PrecipitationSnow Water Equivalent (SWE) Ranking

Summary of graphic: SWE falls in the middle of those observed (30-70 percent) over the past 60+ years for much of our area

Some basins in western/northern WI and northern MN near the most seen in 60+ years

weather outlook 8 14 days
Weather Outlook8–14 Days
  • Temperatures: likely below normal, somewhat moderate
  • Precipitation: No clear signal
weather outlook 90 days march through may
Weather Outlook90 days – March through May

Temps: Likely below normal through the spring

Precipitation (not shown): no clear indication of above or below normal

other factors
Other Factors

Soil Moisture: Near to below normal over most of area, but higher than last year at this time

Frost Depth: Generally 20 to 40 inches over the area, except well below 6-8 feet under pavement. Depth is greatest where snowpack is light or bare ground, shallower where snowpack has insulated the ground

River Ice: Thick layers of ice on most rivers; breakup jams will be a concern

flood outlook mar apr may 2014
Flood OutlookMar-Apr-May 2014
  • Orange: 50% or greater chance of minor flooding
  • Red: 50% or greater chance of moderate flooding (none in MPX area)
  • In MPX area …the main threats are:
  • Chippewa at Durand
  • Eau Claire at Fall Creek
  • St. Croix at Stillwater
  • Minnesota at Savage (backwater from the Miss. R.)
  • Flood threat is greater in the Red River of the North (but fairly typical)

Forecasts take into account all current conditions, 7-day forecast weather, and climatological normals for the remainder of the spring.

flood outlook durand wi
Flood Outlook – Durand WI

Black Line is current forecast: shows about a 75 percent chance of minor flooding, compared to about 50 percent chance in a normal year (blue line). About a 35 percent chance of moderate flooding, compared to 15 in a normal year.

flood outlook fall creek wi
Flood Outlook – Fall Creek WI

Black Line is current forecast: shows about a 55 percent chance of minor flooding, compared to about 30 percent chance in a normal year (blue line). About a 40 percent chance of moderate flooding, compared to 15 percent in a normal year.

flood outlook stillwater mn
Flood Outlook – Stillwater MN

Black Line is current forecast: shows about a 60 percent chance of minor flooding, compared to about 20 percent chance in a normal year (blue line). About a 40 percent chance of moderate flooding, compared to 17 percent in a normal year.

threat factors
Threat Factors

Main things to watch for that would increase flood threat…

  • Extended period of well above normal temperatures, staying above freezing at night
    • Normal highs in lower 30s early March, close to 50 by April 1
  • Moist air melts snow much faster than dry air, so look for dewpoints well above freezing when the air is warm
  • Any major rainfall event that adds a significant amount of water to wet snow

Things to watch for that keep the flood threat manageable…

  • Temps in the 30s to mid 40s, dropping below freezing at night
  • Below to average precipitation – light to moderate snow or light rain is fine
  • Dry air – dewpoints in the teens and 20s.
summary
Summary
  • Overall, spring flood threat over MPX area of responsibility is near to below historical average, but has increased slightly since late February
  • EXCEPTIONS are the Chippewa and Eau Claire basins in Wisconsin, and St. Croix in MN and WI
    • Also the lower Minnesota R around Savage due to backwater from the Mississippi R
  • As always…the true threat lies in how the spring weather unfolds
more info
More Info?
  • Text version of this outlook available at
    • http://forecast.weather.gov/product.php?site=NWS&product=ESF&issuedby=MSP
  • Weather information:
    • http://www.crh.noaa.gov/mpx/
  • River information:
    • http://water.weather.gov/ahps2/index.php?wfo=mpx
  • For further information or if you have questions, please contact us at the NWS Twin Cities office
    • 952-361-6671 (forecaster desk, 24/7)
    • 952-368-2542 (Craig Schmidt, Service Hydrologist)
    • craig.schmidt@noaa.gov