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.
See the set up and forecast below.
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.
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.
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.
This forecast was pretty close to what is displayed above.
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.
These are SUGGESTIONS. There are subtle differences that I will highlight with snapshot time frames below.
This may be an hour too slow.
HRRR Model
NAM 3 Km
This may resemble the 9 PM radar…
The DIRECTION of the showers will gradually SHIFT FROM THE NORTH!
HRRR Model
NAM 3 Km
This may resemble the 11 PM radar…
HRRR Model
NAM 3 Km
This may resemble the 3 AM radar.
Light flow from the East will keep the damp and cool feel to the air.
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.
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.
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.
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.
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