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2011 Spring Flood Outlook. Todd Shea Warning Coordination Meteorologist National Weather Service La Crosse, WI. March 3, 2011. Bottom Line. Normal to above average threat for flooding on Wisconsin rivers / tributaries Above to Much Above Risk on Mississippi River Outline…
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2011 Spring Flood Outlook Todd Shea Warning Coordination Meteorologist National Weather Service La Crosse, WI March 3, 2011
Bottom Line • Normal to above average threat for flooding on Wisconsin rivers / tributaries • Above to Much Above Risk on Mississippi River • Outline… • Setting the Stage for Potential Flooding • 2011 Spring Flood Long Range Probabilistic Outlooks • Outlooks updated….today!
Spring Snowmelt Flood Factors • Past precipitation / Antecedent soil conditions • Snow pack / liquid equivalent • Frost depth • Freeze / melt cycle • Future precipitation • Time of melt • Ice conditions
Spring Snowmelt Flood Factors ??? ??? ???
Setting the Stage Sept.23, 2010 Rainfall September 2010 Precipitation
Setting the Stage Fall 2010 Percent of Normal Precipitation Fall 2010 Precipitation
Setting the Stage 180 Day Percent of Normal Precipitation 180 Day Precipitation
Streamflow Prior to Freeze Up • Most rivers above or much above normal • Reservoirs and lowland areas are full. • River ice has efficiently formed. • Ice jams are possible.
Mississippi River @ La Crosse Stage on March 1st / Spring Crest
6-10 Day Outlook Temperature Precipitation
30 Day Outlook Temperature Precipitation
90 Day Outlook Temperature Precipitation
Probabilistic Outlooks Minor Flood
Probabilistic Outlooks Moderate Flood
Probabilistic Outlooks Major Flood
Probabilistic Outlooks AHPS Webpages • Soil Conditions Based on 3/3/11 • Model run from 3/7/11 – 6/5/11 • **60 year statistical analysis does not include 2009/2010 data.
Wisconsin River @ Portage Portage, WI 95% (90%) -MinorFlood Stage 93% (72%) - Moderate Flood Stage 78% (50%) - Major Flood Stage **Percentages in parenthesis denote probabilistic outlooks from 2/17.
Mississippi River @ La Crosse La Crosse, WI >98% (>98%) -MinorFlood Stage >98% (95%) - Moderate Flood Stage 82% (59%) - Major Flood Stage **Percentages in parenthesis denote probabilistic outlooks from 2/17.
Preliminary outlooks Summary of Outlooks **Percentages in parenthesis denote probabilistic outlooks from 2/17
Preliminary outlooks Summary of Outlooks **Percentages in parenthesis denote probabilistic outlooks from 2/17
Summary of Outlooks Preliminary outlooks **Percentages in parenthesis denote probabilistic outlooks from 2/17
Summary of Outlooks Preliminary outlooks **Percentages in parenthesis denote probabilistic outlooks from 2/17
Summary of Outlooks Preliminary outlooks **Percentages in parenthesis denote probabilistic outlooks from 2/17
Summary of Outlooks Preliminary outlooks **Percentages in parenthesis denote probabilistic outlooks from 2/17
Factors that Will Impact The Spring Flood • Additional precipitation occurs prior to the melt?
Factors that Will Impact The Spring Flood • Additional precipitation occurs prior to the melt? • Type of Melt • Slow (optimal)- • little to no rain/snow and dryer Relative Humidity. • temperatures – highs mid 30s to lower 40s, overnight lows 20’s(or colder) • Rapid (increases flooding threat) • Rain on snow increases melt rate and adds more water to the situation. • Temperatures – Highs mid 40s and warmer, lows around 30 and warmer (Colder overnight lows slows down or shuts off the melting process) • A delayed thaw increases the possibility of a faster melt and the likelihood that a rain on snow event would occur.
Ice Information to Report to the NWS River and Ice Jams • Location (lat and lon if available otherwise, general description, bridge, river, etc) • Duration if known • Is water rising behind the jam (quickly??) • Is water moving around the sides of the jam? • Is anything flooding/near to being flooded? • Is it a sheet of ice, lots of large ice chunks. • Is the ice moving, lifting, etc • What infrastructure is immediately downstream? • Estimate of the size or length of the jam.
