High pressure produced mainly clear skies and light winds on the early morning hours of the 29th. Radiational cooling led to areas of dense fog.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LWX wrote it up.
High pressure produced mainly clear skies and light winds on the early morning hours of the 29th. Radiational cooling led to areas of dense fog.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Baltimore/Washington wrote its last area forecast discussion before the first event at Apr 29, 2:48 AM EST, 1 hour 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 348 AM EDT SUN APR 29 2012 .SYNOPSIS... HIGH PRESSURE WILL BUILD ACROSS THE MID ATLANTIC TODAY...BUT WILL MOVE OFFSHORE ON MONDAY AS A WARM FRONT BEGINS TO MOVE NORTH ACROSS THE REGION. UNSETTLED WEATHER IS EXPECTED FOR THE REMAINDER OF THE WEEK AS SEVERAL UPPER LEVEL DISTURBANCES IMPACT THE AREA. && .NEAR TERM /THROUGH TONIGHT/... ULVL TROF AXIS CROSSING MID-ATLC TNGT...WITH DRIER NLY FLOW ESTABLISHING AS IT PASSES. SHWRS/ISOLATED TSTMS THAT DVLPD IN VICINITY OF H8-7 BAROCLINIC ZONE NOW MOVG S/E OF RGN...AND REMNANT PCPN SHUD END BY 10Z MOST LOCATIONS. TEMPS ERY THIS MRNG IN 40S. AS SFC RDG BUILDS SWD...CLEARING SKIES ARE FCST THIS MRNG FROM NE/SW. PORTIONS OF HIGHLANDS/SHEN VLY/FOOTHILLS WILL BE CLOSE ENUF TO STATIONARY FRONT FOR ELY FLOW...SO UPSLOPE-INDUCED CLOUDS WILL LIKELY PERSIST TDA. DONT THINK MOISTURE IS SUFFICIENT FOR ANY PCPN. TEMPS WILL BE ROUGHLY 5F BELOW NRML...WITH MAXIMA MOSTLY IN 60S. TNGT...LOPRES WILL ORGANIZE ACRS PLAINS...CAUSING BNDRY TO BULGE TO A MORE NW/SE ORIENTATION AND BEGIN LIFTING NWD TWD RGN. LATEST GUIDANCE HAS SPEED UP THIS PROCESS...RESULTING IN INCRG CLOUDS TNGT...ESPECIALLY WRN ZONES. CWA IS FCST TO STAY MAINLY DRY OVNGT...THO A FEW SHWRS COULD INFILTRATE SW ZONES BEFORE SUNRISE MON. MINIMA TNGT WILL RNG FROM UPR 30S ACRS NRN MD TO AROUND 50 NEAR && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... HIGH PRESSURE WILL MOVE OFFSHORE BY EARLY MONDAY AS A WARM FRONT BEGINS TO PUSH NORTH ACROSS THE MID ATLANTIC. THE BEST CHANCES FOR PRECIP ON MONDAY WILL BE IN THE WEST....CLOSEST TO THE WARM FRONT SO HAVE ADJUSTED POPS ACCORDINGLY. A FRONTAL BOUNDARY IS EXPECTED TO SAG SOUTH ACROSS CENTRAL PA MONDAY NIGHT. A STRONG MID LEVEL SHORTWAVE IS ALSO PROGGED TO MOVE EAST ALONG/NEAR THE BOUNDARY OVERNIGHT SUNDAY...WITH SCT PRECIP BREAKING OUT ACROSS THE CWFA. THE BEST CHANCE OF PRECIP WILL BE CLOSEST TO THE MASON DIXON LINE. && .LONG TERM /TUESDAY THROUGH SATURDAY/... UNSETTLED CONDITIONS ARE EXPECTED FOR THE REMAINDER OF THE WORK WEEK. OLD FRONTAL BOUNDARY WILL SET UP NORTH OF THE CWFA ON TUESDAY. LOW PRESSURE IS EXPECTED TO MOVE EAST ALONG THE BOUNDARY DURING THE DAY. THE FRONT SHOULD BECOME DIFFUSE BY THE END OF THE WEEK. HOWEVER...SEVERAL QUICK AND HARD TO TIME MID LEVEL SHORTWAVES ARE EXPECTED TO INTERACT WITH THE BOUNDARY THROUGH THURSDAY. SCT SHRA WILL BE POSSIBLE THROUGH THE PERIOD. A COLD FRONT IS EXPECTED TO APPROACH THE CWFA BY THE END OF THE WEEK INTO THE WEEKEND. NO CHANGES TO THE GRIDS PAST TUESDAY. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... DRIER AIR GRADUALLY MOVG INTO TERMINALS...BUT CURRENT CIG RESTRICTIONS...IFR AT KCHO...LIKELY TO PERSIST UNTIL SUNRISE. THEREAFTER...AS FRONT CONTS SWD AND HIPRES BUILDS TWD AREA...CLEARING SKIES ARE XPCD FROM N/S. KCHO MAY STAY IN VFR STRATUS FOR MUCH OF DAY DUE TO PROXIMITY TO FRONT. SIMILAR CONDS TNGT. WINDS TDA NLY...BCMG E TNGT. MID-AFTN GUSTS CUD REACH 15 KTS. A WARM FRONT WILL MOVE NORTH ACROSS THE MID ATLANTIC ON MONDAY. A FRONTAL BOUNDARY IS EXPECTED TO SET UP ACROSS CENTRAL PA THROUGH MUCH OF NEXT WEEK. PRECIP IS EXPECTED TO FOCUS ALONG AND SOUTH OF THIS BOUNDARY FOR MUCH OF THE WEEK. SUB VFR CONDITION IN SCT SHRA WILL BE POSSIBLE EACH DAY...AND CONVECTION WILL NOT BE DIURNAL IN NATURE. && .MARINE... LAST BATCHES OF PCPN MOVES ACRS WATERS NOW...THEN DRY CONDS XPCD THRU TNGT. NLY WINDS WILL RMN BELOW ADZY THRESHOLD THRU TNGT. A WARM FRONT WILL MOVE NORTH ACROSS THE MID ATLANTIC ON SUNDAY. THE WEATHER WILL REMAIN UNSETTLED FOR MUCH OF NEXT WEEK AS AN OLD FRONTAL BOUNDARY REMAINS STATIONARY ACROSS CENTRAL PA. SEVERAL UPPER LEVEL DISTURBANCES WILL MOVE EAST ALONG THE BOUNDARY...EACH ONE ACCOMPANIED BY SCT PRECIP. MODELS STILL SHOWING SOUTHERLY CHANNELING UP THE BAY MONDAY NIGHT...BUT HAVE BACKED OFF FOR TUESDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && KONARIK/LISTEMAA
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Service Notice</title>
<link rel="stylesheet" href="index.css">
</head>
<body>
<main class="wrap">
<section class="card" role="status" aria-live="polite">
<div class="status" id="status">Temporary Notice</div>
<h1 id="headline">This service is currently unavailable.</h1>
<p id="message1">
The site you requested is temporarily down for maintenance or an unexpected outage.
</p>
<p id="message2">
Please try again in a few minutes.
</p>
<p class="small" id="detail">
If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
</p>
</section>
</main>
<script src="index.js"></script>
</body>
</html>The national radar mosaic for the moment the first event began.
3 dense fog. Local standard time, as filed.
Visibility was around one quarter mile at Cumberland.
Visibility was around one quarter mile at Frederick.
Visibility was around one quarter mile at Hagerstown.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2012Every state in 2012This day in weather historyWarnings in Maryland, April 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 379569, 379568, 379566.