Saturday Night May Turn Stormy To End Summer Then Cooler Sunday

September 21 2024

With just a few hours left of summer, there is one last weather system that may try to work with the calendar. While it has been cloudy, it has also been a bit humid today. The next cold front has circulation spinning up this evening, which may enhance some of the rain and developing thunderstorms as it passes overnight. Below is a look at the short-range models, and I think this may be behaving a little faster than suggested.

The chance for severe limits is low, but some strong gusty winds over 58 mph may prompt a warming or two. Otherwise, this is about the downpours and lightning that could affect your plans or wake you up.

Following this system will be a cooler wind and a definite feel of fall on Sunday. Autumn officially begins tomorrow at 8:43 AM.

The chance for showers and thunderstorms will be this evening and a few rounds overnight. The final push will pass through Central Maryland before sunrise.

Here is a look at the setup and a comparison of the short-range models to see which one can handle this the best.

Live Radar Widget

See the set up and forecast below.

Saturday Evening Set Up

I’ve highlighted a ‘triple point’ with a red circle along the front. This is the circulation trying to spin up a new low pressure, which may enhance the developing thunderstorms overnight.

Let’s Back Up To 5 PM

I want to compare the actual Doppler Radar to the short-range models HRRR (High Resolution Rapid Refresh) and the NAM 3 Km to see how they have handled this so far.

Doppler Radar

This cluster of thunderstorms reached Chambersburg, PA, just north and west of Hagerstown, and there was much more activity in the mountains south of McHenry.

HRRR Model (Forecast for 5 PM)

This forecast was pretty close to what is displayed above.

NAM 3Km (Forecast for 5 PM)

This plot was slower, but I believe it better covered the cluster near Chambersburg. This product may handle the storms better tonight, but it may be as much as an hour too slow.

Radar Simulations

6 PM to 8 AM

These are SUGGESTIONS. There are subtle differences that I will highlight with snapshot time frames below.

HRRR Model Simulation

NAM 3 Km Model Simulation

This may be an hour too slow.

Snapshots

10 PM

HRRR Model 

NAM 3 Km

This may resemble the 9 PM radar…

Midnight

The DIRECTION of the showers will gradually SHIFT FROM THE NORTH!

HRRR Model 

NAM 3 Km

This may resemble the 11 PM radar…

4 AM

HRRR Model 

NAM 3 Km

This may resemble the 3 AM radar.

SUNDAY SEPTEMBER 22

NOTE:

Fall Begins At 8:43 AM Sunday

Morning Temperatures

Noon Snapshot

Wind Forecast

Light flow from the East will keep the damp and cool feel to the air.

Afternoon Temperatures

LOOKING AHEAD

GFS Model Forecast Animation

Monday Through Friday

The weather pattern will be nearly stalled during the week. Steadier rain will fall across the Ohio Valley and the mountains, sending waves of showers our way each day. The chance will be lower farther east.

The big question is the potential tropical system trying to form in the Gulf of Mexico and move onshore into next weekend.

Friday

It is too early to state how strong the storm in the Gulf of Mexico will be, let alone if it will be named. It will more than likely be sending tropical moisture north along the front, feeding rain into our region.

TROPICAL OUTLOOK

The National Hurricane Center 7-Day Outlook

40% chance for something to form in the Gulf of Mexico. This is a suggestion and not a promise. Remember the no-name storm we had off the South Carolina coast last week? It will more than likely still spread moderate to heavy rain our way during next weekend.

7 Day Forecast

A shift to cooler days in the 70s. Chance of showers almost every day. The better chance for rain will be in the mountains.

We will watch (not promise) something tropical trying to form in the Gulf of Mexico by the end of the week. If so, it may impact our weekend weather.

Please share your thoughts and best weather pics/videos, or just keep in touch via social media.

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I am aware there are some spelling and grammar typos and occasional other glitches. I take responsibility for my mistakes and even the computer glitches I may miss. I have made a few public statements over the years, but if you are new here, you may have missed it: I have dyslexia and found out during my second year at Cornell University. It didn’t stop me from getting my meteorology degree and being the first to get the AMS CBM in the Baltimore/Washington region.

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