Sunday, June 6, 2021

Pesky upper low brings a wet & muggy pattern this week

The average first occurrence of 90 degrees in Memphis is May 24. This afternoon as I type this, on June 6, the temperature is 76 under cloudy skies with scattered showers over the region. We hit 89 twice near the end of May and really have not threatened it so far in June. And as you'll see from the forecast below, it's not likely to happen this work week either. Three cheers for less A/C (if you can tolerate the humidity that has arrived in its place)!

Atmospheric Overview

A large upper level low pressure system over the Southern Plains the past few days will lift slowly northeast into Missouri on Monday, then into the Ohio Valley mid-week as it weakens. A trough will extend south from the low into the Mid-South early this week before shifting east as high pressure aloft builds into the area from the southwest behind the weakened and departing low. 

This pattern has pushed summer heat well to our north - into the Northern Plains and east into the Northeast U.S. where highs are reaching the 90s to near 100 degrees in spots! Meanwhile, scattered to widespread showers and embedded heating-of-the-day thunderstorms cover the south-central portion of the country with rain chances having spread east into the southeaster U.S. this weekend. As the upper low shifts east, so do the higher rain chances, before diminishing later this week as high pressure overhead starts to regain control. Let's walk through the week day-by-day...

The upper level pressure pattern from the European model ensemble through Friday evening shows an upper level low weakening and lifting northeast this week, replaced by higher pressure. The blue colors indicate anomalously low pressure, while the orange anomalously high. (WeatherBell) 


Rain has been relatively hit and miss this weekend and I expect that trend to continue into Monday with scattered showers and thunderstorms during the warmer part of the day and lingering showers into the evening. You may or may not get wet - it's impossible to predict where and when the rain falls. However, we can be sure that southerly wind keeps the dewpoints elevated at or above 70, which is high enough to ruin your hair-do and considered very muggy. After a morning low near 70, afternoon highs reach the low 80s.


With the weakening upper low passing by to our north and the trough passing through our area, rain chances are a bit higher (in the 60-70% range) and may include more of the overnight hours as well, though any thunderstorms that occur are more likely to be in the afternoon/evening hours when peak heating occurs. Humidity remains gross as southerly wind continues to fetch Gulf moisture and throw it over the region. Lows remain at or above 70 (which honestly isn't that low) and highs top out in the low to mid 80s. 


As the low starts to move away to our east, high pressure aloft takes its place. However, lingering humidity and a bit more heating thanks to some sunshine breaking through means scattered shower and thunderstorm chances continue, though at lower probabilities (50% Thursday and about 30% Friday, as of now). Precipitation totals through Friday morning could reach the 2-3" range after multiple days of elevated rain chances, though the scattered nature on at least a couple of days could mean wide variances from place to place.

Forecast rainfall through Friday morning from the NWS Weather Prediction Center. 2-3" will be common across the Mid-South. (PivotalWx)

High temps will likely reach near average values in the upper 80s by Friday. With dewpoints remaining uncomfortably high, you should make sure your deodorant supply is in good shape to start the week. 

Next weekend

Early signs point to a bit of relief Saturday in the form of a cool front. If models are correct (that may be a 50/50 proposition six days out, but there is at least some agreement amongst them), then we'll see one more day of scattered thunderstorms. But we'd also receive a push of drier air into the region that will bring relief from high dewpoints and a breath of fresh air from the north, leading to a dry Sunday. 

One thing to consider though is that it won't necessarily be cooler behind the front. In fact, high pressure aloft looks like it might continue to build, so there's a decent chance that by next Sunday afternoon we will be looking the first 90-degree temperature of the year squarely in the eyes. And by mid-June, it's not only almost 3 weeks behind, but also perfectly normal to see 90 every day for a couple of months. Summer is on the horizon!

Erik Proseus
MWN Meteorologist

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