Tuesday, December 18, 2012

Severe weather possible Wednesday night, then MUCH colder on Thursday

The unusually warm temperatures so far this month have meant a couple of chances of severe weather and it appears we have another one in store. A potent winter low pressure system will move out of the Rockies and into the southern Plains on Wednesday, then heads towards Chicago by Thursday morning.  A forecast of blizzard conditions across the central Plains into the Midwest portends a strong system and with the Mid-South in the warm sector of the system, we can expect equally impact-ful weather, only not of the white variety!

The low pressure system responsible for the significant storm will be over northern OK early Wednesday evening. Ahead of the low, wind at the surface and well overhead will increase and showers and thunderstorms will break out across eastern OK and TX into western AR and LA. The wind energy associated with this system will be the main ingredient that forces the development of a line of thunderstorms during the evening hours well to our west.

As the low moves towards central MO during the evening, storms will break out along and ahead of the cold front and organize into a broken line that will stretch across central AR and down I-30 into northeast TX by about midnight.  We expect this line to solidify and move through the metro in the early morning hours Thursday, or likely between 3-6am.

As for impacts, the main threat with the line will be strong to damaging thunderstorm wind gusts of up to 55-70 mph along the squall line.  With that much wind in place, both at the surface and above the region, an isolated tornado also cannot be ruled out, but the threat is minimal and seems to be focused over central AR.  However, the vast majority of the wind energy will be of the straight-line variety.

Storm Prediction Center severe weather outlook for Wednesday night. Click for larger image.
Outside of the severe weather threat, the Mid-South will also encounter a rapid and significant change in conditions behind the front on Thursday.  While temperatures will approach 70 on Wednesday with gusty southerly wind, Thursday will see daytime highs in the lower 50s occur around dawn, with temperatures falling into the lower 40s by mid-afternoon. In addition, west to northwest wind gusting as high as 30-40+ mph Thursday will produce a bad hair day, as well as make temps in the 40s feel downright brutal after upper 60s on Wednesday.

Behind the cold front, temps will fall into the 40s Thursday and wind will gust to 30-40 mph. Click for larger image
Plan ahead for how you will get severe weather information if power is disrupted or you are asleep.  Multiple ways to receive warnings is important, but you also need a way that will still work if the power goes out.  The MemphisWeather.net mobile app will give you the latest radar information, forecast, and current conditions, as well as access to our real-time storm nowcasting via links to MWN on Facebook and Twitter (links also below).  Add StormWatch+ to your app for severe weather notifications, including optional "wake-me-up" audio alerts in case of severe thunderstorms while you are asleep.

In the longer term (Christmas time), models are hinting at another strong system for the middle of next week.  While there is plenty of time to determine exact impacts to the Mid-South, don't be surprised to see a  wet forecast with the potential for thunder around Christmas. We'll monitor and keep you updated.

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