April 30 Weather Possible Flooding and Severe Storms

April 30, 2023

Sunday Morning Update

Has anyone ever talked about April ‘going out like a lion’? If not, this may be a good time to start that. Our second storm is already moving in on our region. Perhaps you were awakened by loud thunder overnight. There is more on the way.

Compare the Live Radar Widget and Simulations below.

There will be a band of heavy rain this morning, then a lull, with a stronger line of thunderstorms forming near the lower Chesapeake Bay mid to late afternoon. The greatest risk for storms to turn severe will be after 3 PM across Southern Maryland and Southeast Virginia. See the timeline below.

Chilly air will follow for the rest of the week, and it will be cold enough for snow in the higher western mountains.

Flood Watch Sunday

NWS has part of Delmarva included in this, but I would suggest it’s safe to suggest flash flooding may affect other areas later today. This will depend on the set up of a slow moving strong storm line as you will see in the simulation below.

Severe Storm Risk

Most of Maryland is in the ‘Marginal’ or lowest level. This means that thunderstorms are possible, with a small chance for them to turn severe.

The SLIGHT RISK area in yellow has a higher chance for storms to produce damaging winds and large hail.

NOTE: I’ve seen recent events verify farther NORTH with the storms. ALSO – The line developing on the simulation below suggests that local flash flooding is still a possibility across Southern Maryland and around The Chesapeake Bay.

Morning Surface Weather

Our storm is moving northeast of Atlanta and being directed into Maryland around the larger upper level Low in the Great Lakes.

This track and conditions between the Atlantic Coast are favorable to increase the moisture supply.  The temperature contrast along the front is marginal, but can support a boundary conducive to slow moving heavy storms this afternoon.

Live Radar and Lightning Widget

Compare to the high resolution model forecast below.

Radar Simulation: 8 AM to 10 PM

Heavy rain this morning, then a lull, with that line of strong storms forming after 3 PM. This will be slow moving and is why I expect more areas could get flooding. I’ve posted key timeframes below.

Morning Snapshot

This signals the heavy band of rain near metro Baltimore and pushing north into Southern PA.

If you compare this to the live radar around 9 AM, you will get an idea that this model is on target of being too slow (which is a possible delay up to 1 hour).

Afternoon/Evening Snapshots

This ECMWF Model shows the core Low Pressure riding along that front. This will be the focus for the heavier rain and some strong/severe storms along and east of the track. The precise track does vary as you will see with the forecast totals below.

NAM 3 Km Snapshot Maps

This tracks shows that slow moving strong line of storms. Again, the timing may be up to 1 hours slower than what verifies.

5 PM

The location of this storm line will determine where potential flooding may occur. Here we see it along I-95 and into Southern Maryland to Southeast Virginia.

6 PM

At this time the slow moving heavy rain line crosses The Chesapeake Bay.

7 PM

The evening focus should be along the Bay and into the Eastern Shore.

8 PM

The intensity will diminish with sunset as the line slowly moves across Delmarva.

Rainfall Total Forecast Today: Compare Two High Resolution Models

You will see a different location for where the heavy rain band sets up. This may be critical for where possible additional flooding may occur.

HRRR Model

This follows the maps I showed above… It focuses the heaviest rain on Delmarva (and Southern Maryland).

NAM 3 Km

This model is farther west with the storm track and thus focusing the heaviest rain near and WEST of the Chesapeake Bay.

I will compare both models in my next update to see which one does a better job.

Temperatures

Morning Observations

Fairly uniform upper 50s to lower 60s with the damp weather.

Afternoon Forecast

Here we can see that marginally warm air near 70ºF into Southern Maryland. This is the boundary that will support the developing storms and heaviest rain later.

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CLIMATE DATA

TODAY April 30

Normal Low in Baltimore:  48ºF

Record 32ºF in 1961

Normal High in Baltimore: 72ºF

Record 92ºF 2010

Monday Morning  Temperatures

It will be chilly again, this time with the wind from the west.

Afternoon Temperatures

Remaining chilly with gusty winds. If you see sunshine, it will likely give way to more clouds and some rain showers.

Storm Animation: Sunday Through Wednesday

I backed up to this wider view to show the full circulation and orbit of weather systems around this cold upper level Low in the Great Lakes.

It will produce snow in the higher elevations, mainly ABOVE 2,000 Ft. Accumulation is possible, especially during the dark night hours across Garrett Co. MD and nearby West Virginia.

Yes, they have had snow in May before.

Snow Forecast

This is assuming a 10:1 ration and all the snow sticks… Most likely there will be melting and compression. We could safely assume totals may be half of what we see here.

7 Day Forecast

The entire week will remain cool. While we see showers on each day through Friday, these will be scattered showers with the unsettled chilly pattern. Most showers will be in the afternoon, and decrease later in the week.

OTHER REPORTS:

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April Heat Wave History

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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 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 predicting the future. All of the maps and information are accurate. The ‘wordy’ stuff can get sticky.  There has been no editor that can check my work when I needed it and 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 able. 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.

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