Arctic high brings prolonged sub-freezing conditions to the Mid-South

By now, most are aware that bitterly cold Arctic air will encompass the region for the latter half of the week thanks to a massive ridge of high pressure building into the region from western Canada. This will be the coldest air Memphis has experienced since last January, which featured two Arctic blasts of this magnitude - one about this time of the month that produced a low of 8 degrees, and another later in the month with a low of 9 (both recorded at Memphis International).

Wednesday night at midnight - cold high pressure dominates the center of the country with Arctic air all the way to the Gulf coast. Graphic courtesy WeatherBell Analytics.

Brutal cold temperatures and wind chills

Lows only drop into the mid 20s tonight as clouds increase due to an upper-level disturbance that fronts the Arctic air. However brisk northerly wind on Wednesday will put a halt to any daytime warming, even as skies clear by mid-day, resulting in temperatures slowly falling during the afternoon. A few flurries are also possible across the area during the morning hours but should have little to no impact.

Wednesday 6pm departure from normal temperatures per the GFS model. We'll be nearly 20 degrees below normal with portions of the midwest more than 30 degrees below normal. Notice the well above normal temps west of the Continental Divide. Graphic courtesy WeatherBell Analytics.

Thursday morning will bring the coldest temperature readings of the period across the central U.S., including the Mid-South. Not only will there be very cold temperatures, but wind that produces dangerous wind chill readings. In the metro, I expect single digit wind chills by Wednesday evening and even some negative single digit wind chills (0 to -5) early Thursday morning as lows drop into the upper single digits in the city and suburbs and possibly near 5 in outlying areas. A Wind Chill Advisory is possible for the area Wednesday night.

GFS modeled wind chills for Wednesday evening. The purple to blue-green transition represents will chills of 0. Graphic courtesy WeatherBell Analytics.

Thursday morning low temperatures from the GFS model. Red to purple transition marks the 10 degree line. Graphic courtesy WeatherBell Analytics.

Thursday 6am departure from normal temperatures per the GFS model. We'll be more than 20 degrees below normal. Graphic courtesy WeatherBell Analytics

Temperatures will remain below freezing on Thursday with highs in the upper 20s, though it won't be as cold Thursday night due to wind becoming southerly. Friday morning's lows will also be in the 20s. Finally, by Friday afternoon, we should see temperatures make it back above freezing for a few hours with highs in the mid 30s - ending a streak of 60+ hours of sub-freezing temperatures.

Near-record high pressure

In addition to the extremely cold temperatures, the strength of the high pressure system itself (as measured by sea level pressure readings) will get close to setting all-time readings as well (the highest high?). For Memphis, our all-time highest pressure reading is 30.96", or 1048 mb, set (coincidentally enough) 91 years ago yesterday (January 5, 1924). This week's high will weaken a bit as it builds south from the northern plains towards the Mid-South, but models are still forecasting a maximum pressure reading Wednesday night in Memphis near 1044 mb, just shy of our all-time record.

Surface weather map for January 5, 1924 when pressure readings set their all-time high in Memphis at 30.96". Map courtesy Joe Lauria, FOX4-TV in Kansas City.

Preparation

The brutal cold temperatures are worthy of preparation on the part of Mid-Southerners as single digit temperatures don't happen often here. We preach the "4 P's" of cold weather planning: people, pets, pipes, and plants. Make sure all are accounted for.

• Take care of any loved ones or friends who, for whatever reason, are susceptible to very cold temperatures. Bundle up the kids, drive them to the bus stop, and of course use your own warm weather gear - gloves, scarves, etc. Yes, it'll be that cold.
• Bring your pets in or SAFELY provide them a warm space wherever they stay. Frozen bowls of water and food are not appreciated by your furry friends. 
• Cover outdoor pipes and spigots and wrap interior pipes and/or leave water dripping in faucets on exterior walls (this is mainly for Wednesday night as we'll remain in the 20s tonight). 
• Finally, any plants that are near cold windows should be relocated. At this point, there are probably few outdoor plants that are not cold tolerant left standing!

We'll be monitoring conditions and providing updates on social media the next few days. In addition, we'll be carefully watching the next precipitation maker expected Sunday and/or Monday as cold air will be slow to retreat. Models are all over the board, but we have included a chance of wintry precipitation in our forecast for now with more fine-tuning to come.

Erik Proseus
MWN Meteorologist

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