Rainfall Projections for Saturday-Sunday…..Flash Flood Guidance

August 30th, 2012 at 10:28 am by under Chad's WLFI Weather Blog

1-3″ looks like a good forecast for the area with a couple isolated 4″ amounts total from Isaac Saturday-Sunday-Monday.  Right now, it does not look like flooding will be a big issue.  It appears showers/some storms will arrive Saturday (up to 70% coverage late) with some Saturday night & additional showers & few storms Sunday (50%).  A few showers/storms may pivot in Monday, but coverage then will run at 30%.  A passing cold front will bring 30% coverage of showers/storms Tuesday, followed by dry, cooler, pleasant weather Wednesday-Friday of next week.

Why am I not talking up the flooding?

Below in the first graphic is a flash flood guidance graphic showing how much rain we could take on in a 6-hour period before we see flooding.  You can see most of the area can handle 4″ in 6 hours, but anything above that in 6 hours would result in flooding.

In the second graphic, you can see that NOAA flash flood guidance shows that we could handle 3″ in 3 hours, but anything above that would bring flooding.

With largely 1-3″ over a 3-day period (isolated 4″ amount or two), such rainfall does not exceed the threshold for flooding in the area with current deficits & soil moisture (even with recent heavy rainfall).

6 Responses to “Rainfall Projections for Saturday-Sunday…..Flash Flood Guidance”

  1. weatherlover says:

    Hi chad,
    Just wondering why other news stations are saying more then 6inches and major flooding..but your saying 1-3 inches?

  2. Garrett says:

    Do you see any threats of isolated tornadoes during this event Chad?

  3. indiana_man says:

    Thank you! I’ve been waiting to hear from you after the dire 9″ forecasts in the newspaper. The confidence you exhibit on the flooding issue is quite impressive. Although everyone should be on alert, I’m now not quite so worried about a flooded basement.

  4. jim says:

    Chad is the best. But. The forecasts are still all over the map. Can’t tell if sat and sun are washouts or not? Maybe someone has a answer?

  5. Doug in Flora says:

    Don’t worry until you see a periscope poking out of the water! :-)

  6. alice says:

    In the paper this morning, the city engineer seemed to think the sewers might not be able to handle all the rain. Do you feel confident that 9 inches is not likely?

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