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February 20-21 Heavy Rain/Flooding/High Wind Threat


Hoosier

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It looks like a period of much warmer temperatures is on the horizon, which will lead to considerable melting snow.  There's a potential for very warm readings in some areas, which would lead to rapid snow melt should that transpire.  Exactly how this plays out is up in the air but at the very least it looks like a substantial flooding threat due to melting snow, with a threat of heavy rain and maybe even a severe threat as was mentioned in the med/long range thread (can start a thread for that later).

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HYDROLOGIC OUTLOOK  

NATIONAL WEATHER SERVICE INDIANAPOLIS IN  

824 AM EST THU FEB 13 2014  

   

..RIVER FLOODING POSSIBLE IN CENTRAL AND SOUTHERN INDIANA  

 

RIVER FLOODING MAY DEVELOP IN CENTRAL AND SOUTHERN INDIANA AFTER  

FEBRUARY 19 AND EXTEND INTO EARLY MARCH. AT THIS TIME IT IS  

UNCERTAIN HOW SERIOUS THE FLOODING WILL BECOME.  

 

SEVERAL FACTORS WILL PLAY INTO THE FLOOD RISK. AS OF FEBRUARY 13...  

SNOW DEPTH IN CENTRAL AND NORTHERN INDIANA RANGED FROM 4 TO MORE  

THAN 12 INCHES. THIS SNOW CONTAINED FROM 1 TO MORE THAN 2 INCHES OF  

WATER EQUIVALENT. ADDITIONAL WINTRY PRECIPITATION IS POSSIBLE  

THROUGH EARLY MONDAY.  

 

A THAW WILL BEGIN THE WEEK OF FEBRUARY 16 AND MAY CONTINUE THROUGH  

THE END OF FEBRUARY. INCREASED RUNOFF WILL OCCUR AS THE SNOW MELTS  

BECAUSE THE GROUND WILL STILL BE FROZEN. THIS MAY CAUSE FLOODING IN  

LOW LYING AREAS...BASEMENTS...SMALL STREAMS AND CREEKS. RIVER RISES  

COULD BE SIGNIFICANT AFTER FEBRUARY 19.  

 

SHOULD A SIGNIFICANT RAIN EVENT OCCUR BETWEEN FEBRUARY 19 AND  

FEBRUARY 24 ... THE SEVERITY OF THE FLOODING WOULD GREATLY INCREASE.  

THE POTENTIAL FOR THE BREAK UP AND DOWNSTREAM MOVEMENT OF THICK  

RIVER ICE COULD CAUSE ICE JAMS AND LOCALIZED SEVERE FLOODING.  

 

LOCAL CONCERNS SHOULD MONITOR WEATHER AND RIVER CONDITIONS DAILY  

THROUGH THE END OF FEBRUARY. LOCAL FLOOD PREVENTATIVE MEASURES  

SHOULD BEGIN AS SOON AS THE SNOW BEGINS TO MELT. FUTURE FLOODING IS  

A POSSIBILITY AT THIS TIME...NOT A CERTAINTY.  

 

FOR DETAILED FLOOD INFORMATION GO TO WEATHER.GOV/IND ON THE WEB. FROM  

THE BLUE MENU BAR ON THE LEFT SIDE OF THE PAGE...CLICK ON RIVERS AND  

LAKES.  

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Been watching this potential for the last week; call me a flood weenie but I'm a hydrologist by study and trade (sorta) and this sort of set up gets me going.

 

Lots of factors lining up this year. Thick ice on rivers (going to need a good torch to take advantage of this, given how thick ice is), ground frozen solid (likely deeper than most recent years), solid snowpack to work with (10-18" around here). Just need to meteorological conditions to line up. Heavy rain will certainly be the kicker for areas that get it. Some of the systems that have been showing up on the models look pretty deep and could carry a lot of moisture north.

 

Not sure if the warm up with extend far enough north to seriously affect us here in ON, but areas further south are certainly under the gun, particularly in the earlier stages of this pattern change. Ontario may not get hit too badly until we get into March.

 

6-10 day temp and precip outlook:

 

26gxu.gif

 

0d6zv.gif

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Hydrologic conditions interest me quite a bit too, especially with my educational background and all. It doesn't take much rain with mild conditions to turn things ugly along waterways and low lying areas. The ground is solid! 

 

I can't remember after what Christmas it was. There was about 12-14" of dense snow on the ground, the next day it rained and made it into the 50s and it wiped out all the snow pretty much. There was water in places I've never seen it before in my neighborhood. All due to the frozen ground not allowing any infiltration.

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The frost layer is much deeper than the usual one foot for this time of year and location.  As has been mentioned the potential is high for small stream and then large stem flooding if the storm the GFS and Euro forecasts comes to fruition late next week.  Water will have no where to go except to run off.  IWX has also posted a hydrologic outlook of concern until further notice.

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Not going to be pretty, if we get heavy rainfall.

 

Shades of the 2007-08 winter floods? Those were bad for some locales.

 

 

That might be a decent comparison but can't remember what the ice jams were like back then. 

 

This is almost a worst case scenario if we get rounds of heavy rain.  Then after that it looks like we go back into a colder pattern...frozen floodwaters? 

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A heavy rain situation for Northern IL and Southern MI would have the potential to be catastrophic, not only are the rivers and ground frozen solid, but the lakes are as well. There would literally be no where for the water to go. SW Lower Michigan would really be in trouble considering their snow pack holds about 5-6" of liquid in it.

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There isn't anywhere for the water to go, its really amazing to drive in the rural areas and see ditches that are 20 feet deep filled to the top with snow. Roadside ditches have feet of hard compacted piled snow in them from repeated plowing.  The small rivers around here have ice in spots that usually never freeze, the mouths have between 20-30 inches of ice on them. I've been ice fishing on spots that are nearly 30 inches thick that normally are a foot. a rapid thaw/rain would be a disaster.

 

A town just Sw of here is planning on using dynamite to blow up river ice on or around the 20th in hopes it will help with flooding when it finally does warm up. The problem is, even if you blow the 2 feet of river ice up, where does the chunks/rements go when the mouth flows into saginaw bay, which is froze across to nearly 3 feet in spots and they are driving trucks 12 miles out.

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Didn't White County experience flooding then frozen flood waters during that scenario?

 

I'm not sure to be honest.

 

Pic from January 2008 flood in White county IN

 

LOT write ups on the Jan 2008 flooding.

 

http://www.crh.noaa.gov/lot/?n=pontiacfloodingjan2008

 

http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=lot&storyid=13432&source=2

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If the NAM, GGEM, and EURO are correct about having heavy precip in the lower lakes, there will be hydrologic issues for sure in the lower lakes next week. Could get crazy by what I'm seeing on the models. 

 

12z EURO through late next Friday.

 

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The full Hydrologic statement LOT just put out.

 

 

HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
330 PM CST FRI FEB 14 2014 /430 PM EST FRI FEB 14 2014/

...INCREASING FLOOD POTENTIAL BEGINNING NEXT WEEK...

WITH TEMPERATURES EXPECTED TO WARM ABOVE NORMAL NEXT WEEK...THE
RISK FOR FLOODING WILL INCREASE. SNOW DEPTHS ACROSS NORTHERN
ILLINOIS AND NORTHWEST INDIANA RANGE BETWEEN 8 AND 18 INCHES. MORE
IMPORTANTLY...THE WATER EQUIVALENT OF THE EXISTING SNOWPACK IS
ESTIMATED BETWEEN 1 AND 4 INCHES...WITH THE HIGHER AMOUNTS
CONCENTRATED MOSTLY NEAR THE WISCONSIN STATE LINE. IN
ADDITION...FROST DEPTHS BELOW THE SNOWPACK RANGE FROM 12 TO 16
INCHES. A DEEP FROST LAYER CAN INHIBIT THE INFILTRATION OF
MELTWATER FROM SNOW AND INCREASE THE AMOUNT OF RUNOFF.

BASED ON CURRENT TEMPERATURE FORECASTS ALONE...RIVERS WILL LIKELY
START RISING DUE TO SNOWMELT DURING THE MID TO LATTER HALF OF NEXT
WEEK. THE SEVERITY AND TIMING OF FLOODING WILL DEPEND LARGELY ON
THE WEATHER CONDITIONS THAT OCCUR DURING THE MELT PERIOD. HEAVY
RAINFALL DURING THAT TIME WOULD INCREASE THE RATE OF RUNOFF AND
SUBSEQUENT FLOODING. IDEAL MELT CONDITIONS TO MINIMIZE THE DEGREE
OF FLOODING WOULD INCLUDE DAYTIME TEMPERATURES RISING MODERATELY
ABOVE FREEZING...AND OVERNIGHT LOWS FALLING BACK BELOW FREEZING.
THIS WOULD HELP TO REGULATE THE RELEASE OF SNOWMELT RUNOFF INTO
AREA STREAMS.

ANOTHER MAJOR CONCERN IS THE AMOUNT OF ICE COVER ON RIVERS ACROSS
THE AREA. NWS CHICAGO ICE SPOTTERS REPORT MANY RIVERS HAVE 100
PERCENT ICE COVER. AS THE RUNOFF BEGINS...FLOWS BENEATH THE ICE
COVER WILL BEGIN TO INCREASE WHICH WILL LIFT AND BREAK THE ICE. AS
THE ICE MOVES DOWNSTREAM...ICE JAMS ARE POSSIBLE. ICE JAMS CAN
RESULT IN RAPID RISES OF WATER LEVELS AND SIGNIFICANT FLOODING IN
THE VICINITY OF THE JAM.

PERSONS LIVING ALONG RIVERS AND IN FLOOD PRONE AREAS SHOULD
PREPARE NOW FOR THE POSSIBILITY OF RIVER FLOODING IN THE COMING
WEEKS. CONTINUE TO CLOSELY MONITOR THIS DEVELOPING SNOWMELT
SITUATION. ANY SIGNIFICANT CHANGES IN PRECIPITATION AMOUNTS OR
TEMPERATURES COULD AFFECT THE TIMING AND SEVERITY OF FLOODING.

FOR DETAILED RIVER FORECAST AND FLOOD INFORMATION GO TO
WEATHER.GOV/CHICAGO AND CLICK ON THE RIVERS AND LAKES LINK.

$

MORRIS

 

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Threat of mega torching seems to be waning but flooding threat still exists with melting snow and models indicating a potential axis of decent to heavy rain setting up somewhere.  Question is exactly where that sets up.

 

All you need is convective rains to cause a problem and an extended period of above freezing temps.

 

December 26-27th 2008 was a great example of that.

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But December 27, 2008 saw temps soar into the 60s...that is an example of a torch.

 

50s back here to west. 50s in February aren't so much of a torch compared to late December. Should say that's a great example of what the EURO was showing.

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