High pressure over the Mid Atlantic led to clear and calm conditions and dense fog formed across most of the region.
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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 over the Mid Atlantic led to clear and calm conditions and dense fog formed across most of the region.
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 20, 7:34 PM EST, 4 hours 41 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 834 PM EDT TUE AUG 20 2013 .SYNOPSIS... HIGH PRESSURE WILL REMAIN CENTERED NEAR THE MID-ATLANTIC COAST THROUGH WEDNESDAY. A COLD FRONT WILL PASS THROUGH THE AREA THURSDAY NIGHT INTO FRIDAY MORNING. HIGH PRESSURE BUILDS IN FROM THE GREAT LAKES THIS WEEKEND AND PERSISTS THROUGH MONDAY. && .NEAR TERM /THROUGH WEDNESDAY/... AS OF 00Z...SFC HIGH PRESSURE IS CENTERED JUST OFFSHORE WITH A LIGHT SLY FLOW. HIGH CLOUDS OVER CENTRAL VA AND SRN MD WHERE SWLY FLOW ALOFT IS DRAWING MID- AND HI-LVL CLOUDS NWD. UNDER LGT WINDS...ANOTHER ROUND OF RADIATIONAL FOG IS EXPECTED... PARTICULARLY FOR NRN VALLEYS WEST OF THE BLUE RIDGE/CATOCTIN MOUNTAIN AND PORTIONS OF THE PIEDMONT. SFC HIPRES AND THE UPPER RIDGE WILL PROGRESS OFF THE MID-ATLANTIC COAST ON WED AS AN UPPER LOW MOVES EWD OVER THE MIDWEST. PLUME OF MOISTURE WILL BE DRAWN NWD INTO THE MID-ATLANTIC REGION IN ADVANCE OF THE LOW /PWATS INCREASE TO 1.75 INCHES DURING THE AFTN/. A LEADING MID-LVL SHORTWAVE TROUGH AHEAD OF THE LOW WILL MOVE FROM SW TO NE DURING THE AFTN AS THE RIDGE DEPARTS. THE BEST FORCING FROM THIS TROUGH AND A AMPLIFYING LLVL THETA-E RIDGE WILL BE POSITIONED OVER THE MTS. POPS IN THE CWA DECREASE TO THE NE ACCORDINGLY. NONETHELESS...FORCING WILL BE WEAK SO EXPECT COVERAGE OF SHOWERS AND STORMS TO BE LOW. MODEST INSTABILITY/SHEAR PROFILES INDICATE A MINIMAL SEVERE STORM POTENTIAL. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... THE UPPER LOW WILL PROGRESS EWD FROM THE MIDWEST TO THE CENTRAL APPALACHIANS WED NGT. ONGOING CONVECTION FROM WED AFTN SHOULD DIMINISH AFTER SUNSET AS THE BOUNDARY LAYER STABILIZES. SCT SHOWERS MAY MOVE IN FROM THE WEST OR REDEVELOP IN THE MOIST AIRMASS OVERHEAD LATE IN THE NGT WITH DPVA/UPPER DIVG OVERSPREADING THE AREA AHEAD OF THE LOW. POPS STILL LIMITED TO LOW CHANCE THOUGH WITH CIN TO OVERCOME IN THE NOCTURNAL BOUNDARY LAYER AND NOT MUCH LIFT PRESENT BELOW THE LFC. CLOUDS AND A MOIST BOUNDARY LAYER WILL LIMIT RADIATIONAL COOLING WED NGT...WITH LOWS IN 60S IN THE MTS AND 70S ACROSS THE GREATER BALT/DC METRO. ON THU...THE UPPER TROUGH WILL MOVE THRU THE AREA...AND WILL INITIATE A LEE TROF AXIS ALONG I-95. GIVEN HUMIDITY...A FOCUSING MECHANISM...AND SUNSHINE HEATING FM ABOVE...THINK TSRA WL BE ABLE TO DVLP-- THE EXTENT OF WHICH WL BE DETERMINED BY EXACTLY HOW MUCH INSOLATION CAN BE REALIZED.POPS KEPT IN THE CHC RGN FOR THE TIME BEING...TRACKING SW TO NE COINCIDENT W/ THE BEST MID-UPR LVL SUPPORT. THRUT THIS PD...WONT HV ENUF INSTBY NOR SHEAR FOR STRONG TSRA. PCPN AMTS AND RATES WL BE A BIGGER ISSUE...BUT NOT SO BIG TO HIGHLIGHT IN THE HWO ATTM. THE SFC COLD FRONT IS FCST TO ADVANCE SEWD INTO THE AREA THU NGT. PRECIP CHANCES WILL DIMINISH THU EVE WITH THE LOSS OF DAYTIME HEATING AND ESPECIALLY OVNGT AS DRIER AIR STARTS TO FILTER IN BEHIND THE FRONT. && .LONG TERM /FRIDAY THROUGH TUESDAY/... THE CDFNT SHUD CLR AREA BY FRI MRNG...CLRG WAY FOR ANTHR PLEASANT SUMMER WKND. THE ONLY WRINKLE WUD BE THE RELATIVE POSITION OF SFC FNT AND H5 TROFFING ON FRI. CURRENT FCST FOR FRI IS DRY ALTHOUGH POPS MAY NEED TO BE ADDED IF THE FRONT STALLS NEARBY LIKE THE 12Z NAM INDICATES...WHICH WOULD PREVENT THE POST-FRONTAL PUSH OF DRIER AIR FROM MAKING IT THIS FAR SOUTH. GREAT LAKES HIPRES BUILDS IN FOR THE WEEKEND BEFORE MOVING OVERHEAD ERY NEXT WEEK...LEADING TO A TRANQUIL WX PATTERN FOR THE MID-ATLANTIC REGION. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... VFR CONDITIONS AND LGT WINDS THIS EVE. BR/FG WILL DEVELOP AGAIN OVNGT...MAINLY PIEDMONT AND WEST. MID AND HIGH CLOUDS WILL PERSIST SOUTH OF THE DC METROS THROUGH LATE TONIGHT...WHICH COULD LIMIT THE EXTENT OF FOG AT CHO. HIPRES MOVES OFFSHORE WED. SCT SHRA AND ISO TSRA MOVE IN ON WED...MAINLY DURING THE AFTN. THE BEST CHANCE FOR PRECIP WILL BE AT CHO. SCT SHRA/TSRA POSSIBLE AT ALL TERMINALS LATE WED NGT AND THU AS AN UPPER LOW MOVES THRU. BRIEF MVFR/IFR POSSIBLE IN HEAVIER SHOWERS AND IN ANY STORM...BUT IT/LL BE DFCLT TO PINPOINT WHEN/WHERE ATTM. CDFNT CROSSES TERMINALS THU NGT. THERE MAY BE SOME FOG BASED ON WET GRND...CONDITIONAL ON HOW QUICKLY DRY AIR CAN WORK SEWD. NW FLOW /AND VFR FLGT RULE/ BYD THAT INTO THE WKND. && .MARINE... HIGH PRESSURE IS CENTERED JUST OFF THE COAST WITH SLY CHANNELING UP THE BAY TO AROUND 15 KT. SLY RETURN FLOW CONTINUES WED WITH HIPRES PERSISTING OFF THE COAST. THINK MOST OF THE SHOWER/THUNDERSTORM ACTIVITY WILL REMAIN WEST OF THE WATERS ON WED...ALTHOUGH AN ISO ONE CANNOT BE RULED OUT DURING THE AFTN. CHANCES FOR SHRA WILL INCREASE LATE WED NGT AND PARTICULARLY ON THU AS AN UPPER-LVL TROUGH MOVES THROUGH. AFTER SUNRISE...THESE SHRA SHUD BE TRANSITIONING TO TSRA. AM NOT SEEING THREAT OF TOO MANY STRONG STORMS ATTM...BUT OF COURSE WITH ANY TSRA COMES A LTNG THREAT. SLY FLOW AOB 10 KT WITH A FEW GUSTS TO 15 KT AHD OF FNT WL VEER NW INVOF A CFP THU NGT-ELY FRI MRNG. HIPRES BLDG BY THE WKND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && SYNOPSIS...BAJ/JRK NEAR TERM...BAJ/JRK SHORT TERM...JRK/HTS LONG TERM...JRK/HTS AVIATION...BAJ/JRK/HTS MARINE...BAJ/JRK/HTS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 732 PM EDT TUE AUG 20 2013 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 211245- 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- 732 PM EDT TUE AUG 20 2013 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...TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. MDZ003>005-009-010-501-502-VAZ025>031-036>040-042-050-051-501>504- WVZ050>053-055-501>506-211245- 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- 732 PM EDT TUE AUG 20 2013 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...TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The national radar mosaic for the moment the first event began.
1 dense fog. Local standard time, as filed.
Visibilities of a quarter mile were measured at Warrenton Airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Virginia in 2013Every state in 2013This day in weather historyWarnings in Virginia, August 2013
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: 474292.