Severe Thunderstorm Watch AND Flood Watch Until 10 PM Sunday

Sunday Afternoon, August 18, 2024

The atmosphere has become more unstable thanks to some breaks of sunshine. A few severe thunderstorms have developed, but the additional force will enhance the activity through tonight.

A small-scale Meso-Low Pressure located in Northern Virginia will get a boost into the evening. This will be the trigger for the storm development in metro areas around the Chesapeake Bay within a few hours before and after sunset.

Based on my prior report, the HRRR Model has performed the best, and the later timeline is why the Flood Watch has been extended until 10 PM. A Severe Thunderstorm Watch has also been added. One concern is slow-moving storms that may last a few hours in some spots, adding to heavy rainfall and flooding.

Alert Reminder

WATCH = POTENTIAL. This means it might happen but not promised. The ingredients are there to form these storms.

WARNING = PROBLEM. This means it IS HAPPENING AND BEING TRACKED.

Severe Thunderstorm Watch

Any storm may reach the criteria to produce:

• Flooding
• Wind Gusts Over 58 mph
• Large Hail Over 1-inch Diameter
• Isolated Tornadoes

NOAA Severe Storm Risk

This has been the priority focus since this morning.

Flood Watch

Heavy rainfall in slow-moving storm cells could produce rates of 1 to 2 inches per hour. This includes the western shore of the Chesapeake Bay in Maryland, from Annapolis through metro Washington, D.C., then up north through central Pennsylvania.

Sunday Afternoon Set Up

The Meso-Low is still located west of Washington, DC. This is where some strong to severe storms may develop any time through this evening. The other instigator in the atmosphere is a strong cold front, but that is farther west and will not pass through our metro areas until tomorrow. So, the movement of the storms with the Meso-Low may be slow and last over some areas for a few hours.

Behind it will be a Fall Preview of cooler temperatures.

Live Radar And Lightning Widget

Computer Models

HRRR Model Focus 5 PM SUN to 2 AM MON

NOTE:

This is a ‘suggestion’ and not perfect. There may be more activity (spotty showers outside of the main cells) on the real radar than what is shown here.

Snapshots

6 PM

8 PM

9 PM

This may be the peak time for metro Baltimore!

9 PM Lightning Flash Rate

This product shows the potential for frequent lightning of 3 to 5 flashes per minute.

10 PM

11 PM

LOOKING AHEAD

MONDAY AUGUST 19

The timing of the cold front and new airmass will bring a drop in temperatures and shift the focus of the rain during the afternoon.

Morning Temperatures

Noon Temperatures

This may be the peak temperature for the day in central Maryland and nearby areas, as the cold front will arrive and push south during the afternoon.

Radar Simulation Noon to Midnight

The cooler air will push the showers and storms to develop during the afternoon and evening.

6 PM Radar Suggestion

The cold front will be shifting south, moving the focus for strong or severe storms into Southern Maryland and Southeast VA. There will also be some leftover showers and storms North of Philadelphia into the Poconos.

The mountain showers will be in response to the cooler air arriving.

Jet Stream Sunday to Thursday

The animation shows the 500mb heights. This is around 18,000 ft and represents the warm and cool air in the atmosphere that responds to how high it is measured.

Here, we can see the influx and established Cool Pattern for much of the week.

Wednesday Morning Snapshot

The morning will be chilly, with a Deep Upper-Level Trough centered in New England and stretching down the East Coast.

Some inland areas will drop into the 40s.

7 Day Forecast

After the storms pass, an Early Fall-Like airmass will settle in for the week. While I am showing 50s for Baltimore metro areas on Wednesday morning, some inland areas will be in the 40s.

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RESTATING MY MESSAGE ABOUT DYSLEXIA

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.

One of my professors told me that I had made it that far without knowing and to not let it be a crutch going forward. That was Mark Wysocki, and he was absolutely correct! I do miss my mistakes in my own proofreading. The autocorrect spell check on my computer sometimes does an injustice to make it worse. I also can make mistakes in forecasting. No one is perfect at predicting the future. All of the maps and information are accurate. The ‘wordy’ stuff can get sticky. 

There has been no editor who can check my work while writing and to have it ready to send out in a newsworthy timeline. Barbara Werner is a member of the web team that helps me maintain this site. She has taken it upon herself to edit typos when she is available. That could be AFTER you read this. I accept this and perhaps proves what you read is really from me… It’s part of my charm. #FITF