No Flooding? Pass the Salt Please.

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The Wall Street Journal has an article quoting NOAA's annual spring flooding forecast as calling for a lower than normal chance for flooding this year. Take it with a grain of salt. 


It is important to understand what is being forecast: The likelihood of snowmelt-driven flooding. I agree, the chance of that is lower than normal since snowfall across the contiguous 48 states is much below normal in most areas.


However, this forecast does not speak to the likelihood of flooding from recurring complexes of thunderstorms, so let's address that.  Take a look at the map below. The blues are areas of heavier than normal rainfall the last 90 days.


[caption id="attachment_7839" align="aligncenter" width="727" caption="NOAA data."][/caption]

In and of itself, this is little cause for worry. But, take a look at the forecast rainfall the next five days:


[caption id="attachment_7840" align="aligncenter" width="247" caption="NWS forecast."][/caption]

More heavy rain in some of the areas that are already too wet.  Again, this by itself, is not a major problem. But, when you take the forecast out an additional days, things start to rise to the level of concern:


[caption id="attachment_7841" align="aligncenter" width="955" caption="Ten day forecast rainfall from the ECMWF model. Courtesy of AccuWeather.com's Professional web site."][/caption]

That is a forecast of a huge area of rainfalls of five inches or more. Is this likely to be a perfect forecast? No, it is not. But, that is not the point. We've been seeing a trend recently for heavy rains to develop in the south central U.S. If it continues, spring flooding from the southern Plains into the Ohio Valley (which has also been wet recently) becomes a distinct possibility.


It is far too soon to explicitly forecast flooding. I just want to make sure readers of this blog are not mislead inadvertently by the WSJ story on spring flooding. 

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