The pattern that has been prevailing over the past couple of days is going to continue, with some changes coming later on this week. More specifically, later this week we’re looking at a much hotter pattern to take hold over this region.
But first, we’ll start with the current weather and the short term forecast.
I wrote this last night, and some of these details are subject to change, but some portions of the Coastal reading area are under a Heat Advisory until 7pm tonight.
The Heat Advisory is in effect for the areas in orange, which includes Lousiana Parishes that are North of Lake Ponchartrain, and Pearl River and Hancock Counties in Mississippi.
In these areas, the Heat Index may reach 110F during the afternoon today, as a dangerous combination of heat and humidity persists across the area. This is pretty typical for this time of the year, but it is still definitely hot. They technically expire tonight but it would not surprise me at all to see them extended to at least tomorrow.
Even in the areas not under an official Heat Advisory, heat indices may reach 105F this afternoon, which can still be dangerous, just to a lesser extent. NWS Mobile has indicated that they don’t plan on issuing advisories yet.
This afternoon, most areas should stay dry, but an isolated storm is certainly possible. The current model consensus is that areas in South MS and AL are more likely to see storms than the Parishes of LA. Below, is just one model, the HRRR. The HRRR is much more isolated than other models, but does indicate that areas East of the Pearl River are more likely to see thunderstorms.
In Louisiana, where it’s hotter, the humidity is a bit lower as a result of higher temperatures. That drop in humidity makes it harder for storms to form, so it’s less likely to see rain in those areas.
With the combination of dry air aloft, and very humid air close to the surface, we’re going to have some strong storm threat for Southern MS/AL, with any storms that do form. Some strong winds will be possible. Very localized heavy rain is also a possibility, but flooding isn’t much of a threat for today.
The upper air charts for this morning show a weak trough (red dashed line) over the Southeast while major ridging (blue squiggly line) dominates the Southwest and Central Plains. Black arrows show the flow of the wind.
Generally, under the high pressure centers, the heat is very high, and it decreases as you move away from the center. In the ridge extensions though, you can have high heat as well, which is what’s happening today over East Texas and Oklahoma.
Skipping ahead to Thursday, we do see the pattern start to change. The ridge becomes stronger and is beginning to migrate East. This is where the pattern really starts to chance for much of the US.
More intense heat is forecast to enter the region, though in areas along the Coast will still have the sea breeze to moderate the temperature. Areas further inland will be dealing with much worse heat come the end of this week.
And looking ahead to next Sunday, we can see the new pattern taking shape – Very large High Pressure center over the Mississippi/Tennessee Valley region, and ridging stretching from the Four Corners out to the Carolinas, bringing intense heat to much of the Southern tier of the US.
Cool air usually swings down through troughs and other weather systems, but with such strong ridging, all the cool air is locked away in the Hudson Bay region in Canada.
With ridging building up over the Eastern Pacific, and Atlantic Ocean, this pattern isn’t in a big hurry to leave, so we’re going to be dealing with this for the extended future. The GEFS, the American model, shows this ridge staying strong even through the First of August!
Bottom line is, this hotter pattern is here to stay.
As far as what this means for us, it means that the heat is going to increase through this week as well as next.
This is the Temperature anomaly map for the remainder of this week, and more or less, for this area, the temperatures are forecast to be close to average, if not slightly above average.
Looking at next weeks, though, the heat is a lot closer, and centered over the Central Plains and Southern Midwest. We may not see crazy high temperatures here along the Coast, but it still will be plenty warmer above average.
Also due to the ridging, this week’s rainfall forecast isn’t really all that high. Area wide, the WPC isn’t really forecasting any more than 0.5” over the next week.
Now, a thunderstorm could sit over you for a while, and you’d have that amount in 45 minutes, but generally speaking, we should be drier than we have been over the past few weeks.
Day-to-Day Forecast
Today
Mostly sunny, with a 50-percent chance of thunderstorms in AL/MS, and a 30-percent chance in LA. Highs in the low-90s. The heat index may reach 110F in some spots. A Heat Advisory is in effect.
Tomorrow
Mostly sunny, with a 30-percent chance of afternoon thunderstorms. Highs in the mid-90s. The heat index may reach 106F. Beaches in AL/MS have a moderate rip current risk (2/3), per NWS Mobile.
Thursday
Mostly sunny, with a 30-percent chance of scattered afternoon thunderstorms. Highs in the mid-90s. The heat index may reach 107F. Beaches in AL/MS have a moderate rip current risk (2/3), per NWS Mobile.
Friday
Partly cloudy, with a 50-percent chance of afternoon thunderstorms. Highs in the low-90s. The heat index may reach 104F.
Saturday
Partly cloudy, with a 40-percent chance of afternoon thunderstorms. Highs in the low-90s. The heat index may reach 104F.
Sunday
Partly cloudy, with a 40-percent chance of afternoon thunderstorms. Highs in the mid-90s. The heat index may reach 106F.
Monday
Partly sunny, with a 60-percent chance of rain and thunderstorms. Highs in the low-90s.
