Friday, December 2, 2011

Potential heavy rain, flooding event for the Mid-South Sunday-Monday

After our first snow of the season earlier this week, the weather over the Mid-South has rebounded nicely with temperatures back in the 60s this Friday and snow a rather distant memory. However, the nice weather won’t be sticking around much longer as yet another cold front will be on the approach this weekend. Unfortunately, it’s another front that looks to stall over the region and set up a prolonged period of rainy conditions, with concern growing for a potential flooding event that may last through Monday night.

Before discussing our possible heavy rain event, some good news for those planning to run the St. Jude Memphis Marathon Saturday morning as weather conditions will be fantastic. Skies look to be partly sunny to mostly cloudy, with starting temperatures in the mid 40s, rising to around 60 by midday. Winds will be out of the south at 10 to 15 mph. Even as the race is ongoing, clouds will gradually be on the increase as moisture increases ahead of our cold front of interest.

The cold front will begin moving through Arkansas and Missouri Saturday night, with a large area of rain expected to be moving slowly east along and ahead of it. This rain will begin moving into the Memphis metro area by Sunday morning. As the front approaches our area, strong high pressure from the surface to aloft over the Southeast U.S. will further slow the front’s progress, eventually bringing it to a stall Sunday afternoon. Unfortunately, models are coming into agreement that the front’s stall will occur right over the metro area (see image below). As this happens, moderate to heavy rain will persist and train over the region through Sunday night and likely into much of Monday as well, bringing copious amounts of rainfall. Though periods of heavy rain are likely, thunderstorms are not expected at this time.

Surface weather map forecast from the National Weather Service for Sunday evening, showing the cold front stalling over the metro area. This will allow for rainfall, some heavy, to train over the region through the night into Monday.
Between Sunday morning and Monday evening, very heavy amounts of rainfall are possible, between 3 and 6 inches. Some areas may see amounts in excess of 6” (see image below). Combined with ground that is already quite wet from previous rain events, concern is increasing for flooding during this period. Flash flooding would be especially likely on roadways and in low-lying and poor drainage areas.  Because water levels on several area rivers, streams and creeks are elevated from previous rain events, flooding in these areas are a possibility as well, that may persist or increase even after rain ends.

Forecast total precipitation for the next several days from the National Weather Service indicates rainfall amounts in the metro in excess of 4”, with nearly 7” depicted in the heart of the metro area. The heaviest rain is expected Sunday and Monday. 
It appears the cold front will begin moving once again late in the day Monday, bringing in much colder air and allowing heavier rain to slowly move east of the region during the night. Temperatures will drop into the 30s by Tuesday morning, and some lighter precipitation may persist into part of the day. As this occurs, there is a chance some of the leftover rain may begin to mix with or turn over to very light snow. At this time, it is expected most of the moisture will have exited the region well before colder air arrives, so major winter weather issues are not anticipated. Much cooler temperatures are likely to persist through the remainder of next week behind the front.

As the threat of flooding increases, the National Weather Service has issued a Flood Watch for the entire area, which goes into effect Sunday morning and will last through Monday evening. Flash Flood and/or River Flood Warnings may be required as heavy rain develops Sunday into Monday. If you are in a flood prone area, you should remain especially aware of developments with this system. Remember, if you encounter a flooded roadway, Turn Around, Don’t Drown!

Stay in close touch with MemphisWeather.Net over the weekend for the very latest. Our MWN Storm Center and forecast page will have full and updated details, with social media nowcasting on Facebook and Twitter expected as well.

NOTE: MemphisWeather.Net’s StormView Radar will be unavailable during this event (and through approximately December 15) due to the ongoing upgrade of the NWS Doppler radar in Millington, TN to dual polarization technology. Alternate links from surrounding radars are available on our StormView Radar webpages, as well as on our mobile site (, and will be frequently advertised on our social media pages. On the MWN Android and iPhone apps, radar data will NOT be available due to programming restraints. We apologize greatly for this inconvenience.

--Kevin Terry, MemphisWeather.Net 

For weather information for Memphis and the Mid-South, where and when you need it, visit on the web, on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.

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