Saturday, February 25, 2017

Warm February ends wet; TN Severe Weather Awareness Week

With four days left in the month, February is currently ranked as the warmest on record in Memphis (55.1°, which is a full 10° above the monthly average). Despite much cooler weather this weekend, we are projecting that the month will end as the warmest since records began in 1875, as the unusual warmth returns to end the month. We should also end "meteorological winter" (December-February) with as fourth warmest on record. Looking ahead to this week, it also appears that March will come in like a lion! Let's get into the details.

Memphis average temperatures by month for "meteorological winter," ordered by warmest season. This winter currently ranks #4.
A strong cold front that brought scattered severe storms to places that don't usually receive them in the winter (Upper Ohio Valley) also moved through the Memphis metro last evening. Though very little rain fell in the metro, it did usher in MUCH cooler temperatures. Most of us woke up to wind chills in the mid 20s with temperatures in the mid 30s this morning.

24-hour temperature differencefrom 9am yesterday to 9am today. You can clearly see areas that the front passed through in the past day! Purples indicate temperatures more than 30° cooler in 24 hours. (WxBell)
As high pressure moves directly overhead later today, wind dies down and temperatures remain cool despite sunny skies. We'll see highs near 50. With light wind, clear sky, and dry air in place tonight, expect the budded trees and flowers to shiver as the mercury falls below the freezing point - to near 30 in the city and mid to upper 20s in rural and suburban areas. If you need to cover plants to protect them, do so this evening. Outlying areas could see 6-8 hours of sub-freezing temperatures overnight!

Sunday begins the warm-up as high pressure shifts east. For the most part, it will be a sunny day with high clouds moving in by sunset in advance of the next quickly-moving weather system. Look for highs about 10° warmer than today, or near 60°. The month of February has also been dry with officially just over an inch of rain so far. That will change as the next weather-system arrives Sunday night. Low pressure organizes in the southern plains and a warm front approaches from the south. Upper level low pressure will trigger a rain event Sunday night into Monday morning with some rain potentially heavy early Monday morning. No thunder is anticipated from this event, which will move out during the morning hours Monday. Anticipate a wet morning commute.

The North American Model (NAM) prediction for rainfall from 6pm Sunday through 6pm Monday. (PivotalWx)
Monday night, the warm front moves through from south to north, ushering in very humid Gulf air and triggering scattered showers and a few thunderstorms. This puts the Mid-South in the warm sector of the next low pressure and frontal system. Tuesday will see very warm conditions and unstable air, but with little dynamics to trigger precipitation, only a few showers or thunderstorms are anticipated, and it could turn out dry. Highs will be back into the 70s with dewpoints near or above 60° and warm south wind.

The NAM model prediction for high temperatures on Tuesday afternoon, as warm, moist southwesterly breezes push highs well into the 70s. (PivotalWx)

Tuesday night into Wednesday morning, as March arrives, is when we'll feel the effects of that next front. It's too early to predict severe weather chances, but the front will be strong with decent upper level dynamics and will tap into plenty of moisture. The X-factor could be instability, which would peak during the warmest part of the day. If the front arrives as scheduled now (mid-day), sufficient instability will be a question mark. For now, plan on a stormy day Wednesday, particularly early. Behind the front, temperatures cool down again, but sunny skies prevail for the remainder of the week.

The American GFS model prediction for rainfall from 6pm Tuesday through 6pm Wednesday. Most of this falls late overnight into Wednesday morning locally. (PivotalWx)

Next week is also Severe Weather Awareness Week in TN and AR (this past week was awareness week in MS). As usual, we plan to have a full slate of information and education to help prepare you for severe weather season. In addition, we'll have some giveaways throughout the week, including free MWN apps (including our StormWatch+ severe weather alert app upgrade) and free weather radios from our severe weather awareness week partner, Midland Radio!

The week starts tomorrow with a discussion of SKYWARN and social media storm spotting and reporting and continues each day with a different topic. We also will be hosting a live video presentation (most likely Tuesday evening, weather-dependent!) with a panel discussion on multiple severe weather topics and a chance for you to ask questions. You can get all the details of our activities this week on our Severe Weather Awareness page on MWN.

Erik Proseus
MWN Meteorologist

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