A moist and unstable atmosphere was in place in the Mid Atlantic. Scattered showers and thunderstorms developed and were very slow movers.
Every event with a place to put it. 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.
A moist and unstable atmosphere was in place in the Mid Atlantic. Scattered showers and thunderstorms developed and were very slow movers. Low level moisture and instability led to the tornadogenesis.
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 Aug 7, 2:31 PM EST, 2 hours 24 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 331 PM EDT TUE AUG 7 2012 .SYNOPSIS... WEAK HIGH PRESSURE WILL REMAIN OFF THE COAST MIDWEEK...PERMITTING SOUTHWEST FLOW TO BECOME ESTABLISHED. A COLD FRONT WILL ARRIVE LATE FRIDAY INTO SATURDAY. && .NEAR TERM /THROUGH WEDNESDAY/... 18Z SFC ANALYSIS SHOWS THE CENTER OF HIPRES HAS SHIFTED OFF THE MID-ATLANTIC COAST. REMNANT SFC DEWPOINT BOUNDARY STRETCHING FROM THE NRN PIEDMONT TO JUST SE OF I-95. THIS BOUNDARY WILL REMAIN NEARLY STATIONARY THIS AFTN. DEWPOINTS IN THE LOW AND MID 60S RESIDE NORTH AND WEST OF THE BOUNDARY...LOWER 70S TO THE SOUTH AND EAST. BLENDED SAT AND RAP ANALYSIS SHOWED A TIGHT NW TO SE PWAT GRADIENT...RANGING FROM UNDER INCH OVER THE ALLEGHENY FRONT TO JUST UNDER TWO INCHES OVER THE SRN MD CHSPK BAY. SCT SHOWERS AND TSTMS HAVE DEVELOPED ERY THIS AFTN SOUTH AND EAST OF DC. EXPECT AN UPTICK IN THE ACTIVITY MID AFTN IN THIS MOIST/UNSTABLE AIRMASS ALONG AND SOUTH/EAST OF THE BOUNDARY...WHERE MID-LVL LIFT IS LOCATED AHEAD OF A WEAK SHORTWAVE TROUGH MOVING THRU SRN MD. WITH LIGHT WINDS ALOFT...STORM MOTION WILL BE VERY WEAK. THE SETUP SUPPORTS A LOCALIZED THREAT OF FLASH FLOODING IN THE NRN PIEDMONT AND SRN MD. STILL CANNOT RULE OUT A PULSE SEVERE STORM OR TWO GIVEN THE FAVORABLE ENVIRONMENT FOR A WET MICROBURST... ALTHOUGH CLOUD COVER HAS LIMITED THE THREAT. LGT SLY FLOW WILL OVERTAKE ENTIRE REGION TNGT AS HIPRES MOVES AWAY FROM THE ERN SEABOARD. SIMILAR TO LAST NGT...CONVECTION WILL WANE AFTER SUNSET...BUT A COUPLE OF SHOWERS AND STORMS MAY LINGER OVNGT...ESPECIALLY IN SRN MD. ANOTHER MUGGY NGT IS EXPECTED WITH MIN TEMPS IN THE 60S WELL NORTH AND WEST OF THE DC AND BALTIMORE...LOW 70S IN THE NEARBY SUBURBS AND MID 70S IN THE CITIES. THE DIFFUSE BOUNDARY WILL REMAIN OVER THE REGION WED...BUT SHOULD START TO PROGRESS NWD. SHOWERS AND STORMS EXPECTED TO DEVELOP AGAIN IN THE WARM/MOIST AIRMASS...ESPECIALLY EAST OF THE BLUE RIDGE. GIVEN LACK OF SYNOPTIC LIFT... COVERAGE SHOULD BE ISO. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... AN UPPER-LEVEL TROUGH WILL APPROACH THE CWA DURING THE SECOND HALF OF THE WORK WEEK. THIS WILL PRODUCE SHOWERS AND THUNDERSTORMS...SOME OF WHICH COULD BE SEVERE...BOTH THURS AND FRI AFTERNOONS. CONTINUING SOUTHWEST FLOW INTO THE AREA WILL MAINTAIN A WARM HUMID AIRMASS THROUGH MIDWEEK. THIS COMBINED WITH THE PASSAGE OF A SHORTWAVE PRIOR TO THE MAIN UPPER-TROUGH WILL PROVIDE SUFFICIENT LIFT FOR TSTMS THURS AFTERNOON. BY FRI...A COLD FRONT LOOKS TO BE POSITIONED JUST TO THE REGION/S WEST WITH ANOTHER WIDER SPREAD ROUND OF SEVERE WEATHER IN THE AFTERNOON HOURS. BOTH DAYS HAVE BEEN OUTLOOKED BY SPC WITH A SLIGHT RISK FOR THE CWA DURING DAYS 3 AND 4. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... GUIDANCE DEPICTS THE ACTUAL FRONT TRANSITIONING ACROSS THE AREA DURING THE DAY SATURDAY WITH HIGH PRESSURE BUILDING IN BEHIND. THIS WILL LOWER TEMPS BY 5-10 DEGREES TO VALUES A LITTLE COOLER THEN NORMAL FOR THE BEGINNING OF AUGUST. PRECIP COULD LINGER THROUGH THE DAY SATURDAY AS THE FRONT SLOWLY MOVES OFFSHORE. HOWEVER...THE THREAT OF SEVERE STORMS WILL BE CONFINED TO THURS AND FRI. WIND WILL SHIFT TO NORTHWEST BRINGING DRIER AIR INTO THE REGION FOR THE BEGINNING OF THE WEEK. EXPECT MOSTLY DRY CONDITIONS WITH DAYTIME HIGHS IN THE MID 80S AND LOWS IN THE MID 60S FOR SUN THROUGH TUE. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... MVFR AND IFR VSBYS ARE EXPECTED ACROSS AREA TERMINALS TONIGHT AS A HUMID AIR MASS REMAINS OVER THE REGION. CHO SHOULD SEE THE BIGGEST DROP IN VSBY AS THE AREA COULD SEE SOME SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON. ELSEWHERE WITH THE EXCEPTION OF DCA...SHOULD SEE REDUCTIONS TO AROUND 3 SM. WIND WILL SLOWLY SHIFT FROM NORTHEAST TO SOUTHWEST THROUGH THE TAF VALID PERIOD. THE SOUTHWESTERLY SHIFT IN WIND DIRECTION WILL HELP TO MAINTAIN LOW LEVEL BUT VFR CIGS THROUGH THE DAY TOMORROW. AN UPPER LOW WILL DEEPEN OVER THE UPPER MIDWEST AND GREAT LAKES LATE THIS WEEK WHILE AN ASSOCIATED COLD FRONT MOVES THRU FRI NGT OR SAT. UNSETTLED WX WILL OCCUR DURING THIS TIME...WITH HIGH CHANCES FOR PRECIP THU-SAT. SOME STORMS MAY BE STRONG DURING THE AFTN HRS THU AND FRI. VSBY RESTRICTIONS IN STORMS LIKELY. && .MARINE... A RESIDUAL BOUNDARY REMAINS STATIONARY OVER THE CENTRAL MD CHSPK BAY....WITH SLY FLOW OCCURRING SOUTH OF NORTH BEACH AND NELY FLOW TO THE NORTH. THE BOUNDARY WILL SLOWLY LIFT NWD WED. ENHANCED SLY FLOW DUE TO CHANNELING SOUTH OF THE BOUNDARY WILL STILL REMAIN BELOW SCA THRESHOLD THRU WED. ISO SHOWERS AND STORMS MAY LINGER INTO THE NGT...THOUGH NOT AS STRONG AND WIDESPREAD AS THIS AFTN. THREAT OF STORMS CONTINUE WED. LOPRES AND ASSOCIATED COLD FRONT WILL APPROACH FROM THE WEST THU BEFORE MOVING THRU FRI AND SAT...RESULTING IN A PROLONGED PERIOD OF SHOWERS AND STORMS DURING THIS TIME. SOME OF THE STORMS MAY BE STRONG THU AND FRI AFTN. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && KLEIN/CLS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1010 AM EDT TUE AUG 7 2012 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 081000- CHESAPEAKE BAY NORTH OF POOLES ISLAND MD- CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT MD- CHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH MD- CHESAPEAKE BAY FROM NORTH BEACH TO DRUM POINT MD- CHESAPEAKE BAY FROM DRUM POINT MD TO SMITH POINT VA- TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD MD- TIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND MD- TIDAL POTOMAC FROM COBB ISLAND MD TO SMITH POINT VA- PATAPSCO RIVER INCLUDING BALTIMORE HARBOR- CHESTER RIVER TO QUEENSTOWN MD-EASTERN BAY- CHOPTANK RIVER TO CAMBRIDGE MD AND THE LITTLE CHOPTANK RIVER- PATUXENT RIVER TO BROOMES ISLAND MD- TANGIER SOUND AND THE INLAND WATERS SURROUNDING BLOODSWORTH ISLAND-DISTRICT OF COLUMBIA-NORTHERN BALTIMORE-HARFORD- SOUTHERN BALTIMORE-PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS- CALVERT-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX- ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA- KING GEORGE- 1010 AM EDT TUE AUG 7 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE MARYLAND PORTION OF THE CHESAPEAKE BAY...TIDAL POTOMAC RIVER...AND ADJACENT COUNTIES IN CENTRAL MARYLAND AND NORTHERN VIRGINIA AS WELL AS THE DISTRICT OF COLUMBIA. .DAY ONE...TODAY AND TONIGHT ONE OR TWO THUNDERSTORMS IN SOUTHERN MARYLAND AND CENTRAL VIRGINIA MAY PRODUCE LOCALLY DAMAGING WINDS THIS AFTERNOON. THE STORMS WILL BE SLOW-MOVING AND COULD PRODUCE HEAVY RAINFALL...WHICH MAY LEAD TO VERY LOCALIZED FLASH FLOODING. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ON THURSDAY AND NUMEROUS THUNDERSTORMS ARE EXPECTED ON FRIDAY. SOME OF THESE THUNDERSTORMS MAY BE SEVERE...CAPABLE OF PRODUCING DAMAGING WIND GUSTS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED ON THURSDAY AND FRIDAY...MAINLY DURING THE AFTERNOON AND EVENING HOURS. MDZ003>005-009-010-501-502-VAZ025>031-036>040-042-050-051-501>504- WVZ050>053-055-501>506-081000- WASHINGTON-FREDERICK MD-CARROLL-MONTGOMERY-HOWARD- EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-AUGUSTA- ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-NELSON- ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-LOUDOUN-ORANGE-CULPEPER- NORTHERN FAUQUIER-SOUTHERN FAUQUIER-WESTERN HIGHLAND- EASTERN HIGHLAND-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-HARDY- WESTERN GRANT-EASTERN GRANT-WESTERN MINERAL-EASTERN MINERAL- WESTERN PENDLETON-EASTERN PENDLETON- 1010 AM EDT TUE AUG 7 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN WEST VIRGINIA... NORTHERN AND CENTRAL VIRGINIA...AND CENTRAL AND WESTERN MARYLAND WITH THE EXCEPTION OF GARRETT COUNTY. .DAY ONE...TODAY AND TONIGHT ONE OR TWO THUNDERSTORMS IN CENTRAL VIRGINIA MAY PRODUCE LOCALLY DAMAGING WINDS THIS AFTERNOON. THE STORMS WILL BE SLOW-MOVING AND COULD PRODUCE HEAVY RAINFALL...WHICH MAY LEAD TO VERY LOCALIZED FLASH FLOODING. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ON THURSDAY AND NUMEROUS THUNDERSTORMS ARE EXPECTED ON FRIDAY. SOME OF THESE THUNDERSTORMS MAY BE SEVERE...CAPABLE OF PRODUCING DAMAGING WIND GUSTS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED ON THURSDAY AND FRIDAY...MAINLY DURING THE AFTERNOON AND EVENING HOURS.
The Sterling radar (KLWX), 88 km away, was scanning. The volume nearest the first event began at 21:56 UTC.
1 tornado. Local standard time, as filed.
There was a waterspout that formed over the Patuxent River near Benedict Bridge in Calvert County, MD.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2012Every state in 2012This day in weather historyThe tornado archive for Maryland, 2012Warnings in Maryland, August 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: 409451.