A roller-coaster week as “real fall” approaches

As it turns out, the “fall weather” we had the week before last was simply a tease. Late summer returned in the past week and I for one have had enough. I think many of you agree. This week appears to be the real transition with airmasses fighting over the airspace in the southern U.S., and a major fall front finally, it appears, winning out by week’s end. Let’s dig into the details.

Early this week

Temperatures have been very warm this weekend and humidity has slowly crept up as well. Mid to upper 80s high temperatures are a good 10 degrees above normal. However, there are signs of a battle ensuing off to our west. Check out the severe weather outlook for today into tonight:
A major (for early fall) severe weather risk exists across the Southern Plains tonight (NWS/SPC)

A level 4 (Moderate) severe weather risk anywhere this time of year can only mean one thing: battle of the airmasses! A significant trough with chillier weather out west is approaching a hot and humid airmass over the southern Plains, resulting in what will likely be many severe thunderstorms and probably tornadoes in OK. 

The front that is pushing through that area will arrive in the Mid-South Monday. Fortunately, most of the strong upper level energy will pull well to our north, but we still expect scattered showers and a few thunderstorms tomorrow. Currently the Storm Prediction Center has us under a level 1 (Marginal) severe weather risk, but I think that is a stretch. 
The severe weather outlook for the Mid-South Monday places the area in a level 1 (Marginal) risk. (NWS/SPC)

It will be a gusty day with with south wind blowing over 30 mph at times so conceivably a thunderstorm could result in gusts higher than that, as wind energy will be present. However the other ingredients are meh. It won’t rain all day, but could just about anytime between 8am-3pm. Overall rainfall amounts should be limited to under one-quarter of an inch, but a few brief downpours are entirely possible. Look for highs in the lower 80s.
The mid-day Sunday HRRR model from 7pm Sunday to 7pm Monday projects strong storms to diminish over AR overnight tonight, then move through the Memphis metro Monday, mostly as showers with a few thunderstorms embedded. (WeatherBell)

Tuesday

The front will just barely move to our east before washing out, so we’ll see the dewpoints fall from the upper 60s to upper 50s Monday night, which will allow for a bit of a cooler wake-up call Tuesday with lows in the low 60s. However, with partly cloudy skies and not much cooler air behind the front, look for highs Tuesday again in the mid 80s. By Tuesday night, southerly flow will start to reestablish itself, which means a warmer night (near 70 for the low Wednesday morning) and more humidity again.

Wednesday/Thursday

We’ll be back in a warm, semi-humid airmass for mid-week with highs in the mid 80s, lows near 70, and some gusty south wind. Overall, the weather is just setting us up to appreciate the approaching fall front even more! A few showers will be possible by Thursday afternoon as it inches closer. We’ll see how that might affect the Memphis vs. Navy football game at the Liberty Bowl Thursday evening.

Friday

Friday looks like the next best chance of rain showers and possibly some thunderstorms, as a major system approaches. We’ll want to keep a close eye on this day as models still don’t have the specifics pinned down, but with a major pattern change incoming, we can’t rule out a few strong storms. That front arrives late Friday or Friday night, so Friday Night Lights could be wet. 
The forecast surface map Friday morning shows a front stretching from Canada to south Texas just to our west, poised to move through late in the day. Rainfall is likely ahead of it and much cooler temperatures will be found behind it. (Adapted from NWS/WPC)

Next weekend

Fall arrives! 
Right now it looks like rain is gone by Saturday morning and we’re setting up for a gorgeous weekend! Sunny skies, breezy north wind pushing all of the humid air back down to the Gulf beaches, and cool fall temperatures. The forecast for now calls for upper 50s Saturday morning and 70 degrees Saturday afternoon – or much of the day in the 60s – followed by lows Sunday morning near 50 in the city (that means some 40s are possible outside the city) and highs near 70 once again Sunday afternoon. This airmass also appears to have some staying power, as we’re looking at low 70s for highs into the following week.
Hang on Mid-South, fall is coming!
Erik Proseus
MWN Meteorologist

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