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 (m.memphisweather.net),
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