Sunday, December 27, 2015

One more round of strong storms early Monday, then winter arrives

If Mid-South weather could set it's "status" for this weekend, it would be "It's Complicated."

Wavering cold front

A cold front that originally came through Christmas Eve night, retreated to the north Christmas night to allow record-setting warm air to return the Mid-South on Saturday, has dropped south again earlier this morning. This has allowed temperatures in the 50s back into west TN, separating the northern Mid-South from the 70s just south of the metro. However, it's not done vacillating yet. It will pull back north of the metro once more later this evening and placing us in the warm sector one more time as - mercifully - a much stronger cold front arrives from the west early Monday morning, putting an end to the whimsical nonsense,

Metro temps as of 2:30pm Sunday, in the wake of a cold front that sits along the MS/TN state line.

Overnight weather details

As the Mid-South returns to the warmer airmass overnight, it will set the stage for one more chance of severe storms as the potent spring-ending cold front arrives from the west. Showers and a few thunderstorms are expected to be scattered as the front retreats back to the north this evening, then as we near dawn Monday, the front pushes a squall line into the region from AR. The squall line will be moving into an area that is favorable for strong thunderstorms, a few of which could be rotating.

Damaging wind along the line will be the most likely severe weather threat, along with very heavy rainfall and a chance of flash flooding, but a couple of tornadoes will be possible, mainly south and west of the metro in the wee hours Monday. The most likely timing for the squall line to pass through the metro is between 4am-9am Monday with a few strong storms also possible ahead of the line, after about 3am. A Flash Flood Watch is in effect for widespread 2-5" rainfall amounts from Sunday afternoon through Monday at noon.

Low pressure over the southern Plains will drag a cold front into the Mid-South early Monday, as a second cold front retreats just to our north overnight, placing the Mid-South in the warm sector one last time overnight. Map above valid at midnight.

Simulated radar from the HRRR model shows a squall line of storms advancing on the Mid-South overnight from AR and LA as snow and ice wrap around low pressure over the Southern Plains. Loop ends at 4am, just before the line moves through the metro. Graphic courtesy WxBell. Model data - timing may not be exact.

Monday - post-front weather

Behind the line, low pressure to our northwest and strong high pressure over the southeast U.S. will set up a scenario for very gusty wind throughout the day Monday. Southwest wind to 30-40 mph will be possible, resulting in the issuance of a Wind Advisory for the metro through 6pm Monday. All metro residents are encouraged to tie down or bring in any outdoor items that could blow away. Wind will diminish Monday evening to 10-15 mph.

Bottom line

To recap, scattered showers and storms are expected most anytime through the wee hours Monday morning. The severe weather threat begins after about 3am Monday and is most likely with a squall line of storms that should be over the metro between 4am-9am Monday. Damaging wind, small hail, and an isolated tornado (mainly southwest of the metro) is possible. Flash flooding is also possible due to very heavy rainfall and strong gusty southwest wind will continue throughout Monday.

The rest of the week

Once the system exits Monday, temperatures drop to much more seasonal levels with highs in the low 50s and lows in the 40s Tuesday and Wednesday, before dropping even further as we head towards New Year's Eve and the start of 2016. A chance of showers exists ahead of the reinforcing push of cold air on Tuesday night and Wednesday. Reference the MWN Forecast in our mobile app or at the links below for those details. We'll have any additional updates on our social media channels the next 24 hours.

Erik Proseus
MWN Meteorologist

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