Surface high pressure built overhead during the early morning hours of the 9th. Mainly clear skies and light winds combined with high amounts of low-level moisture to produce areas of dense fog across portions of the Shenandoah Valley and Potomac Highlands.
Every event with a place to put it; 5 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.
Surface high pressure built overhead during the early morning hours of the 9th. Mainly clear skies and light winds combined with high amounts of low-level moisture to produce areas of dense fog across portions of the Shenandoah Valley and Potomac Highlands.
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 Jul 8, 7:00 PM EST, 6 hours 15 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 800 PM EDT FRI JUL 8 2011 .SYNOPSIS... A COLD FRONT WILL PUSH INTO THE CHESAPEAKE BAY THIS EVENING...AND OFF THE COAST OVERNIGHT. HIGH PRESSURE WILL BUILD IN FROM THE NORTH SATURDAY AND REMAIN IN PLACE THROUGH THE WEEKEND. A SECOND FRONT WILL PUSH SOUTH ACROSS THE MID ATLANTIC LATE MONDAY INTO TUESDAY...WITH HIGH PRESSURE RETURNING FOR THE SECOND HALF OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... SVR AND FLASH FLD WATCHES HV BEEN DROPPED. LATER TNGT FOG COULD BE A PROBLEM GIVEN THE LARGE AMTS OF LO LVL MOISTURE AVBL. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/... SATURDAY...COLD FRONT PUSHES INTO THE SOUTHERN MID ATLANTIC BY THE LATE MORNING. JUST LOW CHANCES FOR LINGERING SHOWERS SOUTH OF AN E-W LINE THROUGH DC FOR THE MID MORNING HOURS. OTHERWISE...LIGHT NLY FLOW BEHIND THE TROUGH WITH SKIES CLEARING BEFORE MIDDAY. ABUNDANT INSOLATION ALLOWS FOR SLIGHTLY ABOVE NORMAL MAX TEMPERATURES... AROUND 90F PER GRIDDED GFS MOS GUIDANCE. SATURDAY NIGHT THROUGH SUNDAY...SFC HIGH PRESSURE BUILDS SOUTH INTO THE CENTRAL MID ATLANTIC. DRY WITH A LIGHT ONSHORE FLOW WITH HIGH PRESSURE CENTER TO THE NORTH. MIN TEMPS LOW TO MID 60S INLAND...LOW 70S NEAR SHORE. MAX TEMPS AROUND 90F...THOUGH NO HEAT INDEX WITH DEW POINTS IN THE LOW TO MID 60S. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... SFC HIGH PRESSURE MOVES OFFSHORE WHILE A RIDGE OVER THE S-CNTRL CONUS DRIFTS EAST. SWLY LOW LEVEL FLOW BRINGS PLUME OF ABOVE NORMAL TEMPERATURE AIR FOR EARLY NEXT WEEK. MAX TEMPS SHOULD REACH INTO THE MID 90S WITH DEWPOINTS APPROACHING 70F. EXPECT HEAT INDICES IN THE UPR 90S. AN APPROACHING TROUGH MAY TRIGGER THUNDERSTORMS WEST OF THE BLUE RIDGE LATE MONDAY AFTERNOON. A COLD FRONT CROSSES TUESDAY...THE SLOWER 12Z GFS ALLOWS HEATING TO TAKE PLACE...WITH MAX TEMPS IN THE MID 90S AGAIN...WHILE THE 00Z ECMWF BRINGS THE TROUGH AXIS THROUGH BY DAYBREAK. CHANCE POPS MONDAY NIGHT INCREASE TO HIGH CHANCE TUESDAY. WITH THE LIFTED INDEX AROUND -5 AND DECENT SHEAR ALONG THE TROUGH...EXPECT THUNDERSTORMS. THE MAIN ACTIVITY WILL BE ASSOCIATED WITH THE FRONT...SO SPECIFICS ON PRECIP TIMING AND INTENSITY WILL BECOME MORE CLEAR IN THE COMING DAYS. HIGH PRESSURE FOLLOWS THE FRONT AGAIN...WITH TUESDAY NIGHT INTO THURSDAY LOOKING DRY. INCLUDED LOW CHANCES FOR THUNDERSTORMS ALONG THE ALLEGHENY FRONT AS RETURN FLOW COMBINED WITH TERRAIN CIRCULATIONS AIDING DEVELOPMENT. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... AREAS OF FOG PSBL OVRNGT AT MOST TAF SITES GIVEN THE QUANTITY OF RAIN THAT FELL DURG THE AFTN AND FACT THAT THERE WON'T BE STRONG WINDS COMING IN BEHIND THE FNT. VFR RETURNS BY MIDDAY SATURDAY MORNING WITH LIGHT NLY FLOW BEHIND THE COLD FRONT. VFR PREVAILS AS HIGH PRESSURE BUILDS FROM THE NORTH INTO SUNDAY OUTSIDE OF FOG POTENTIAL LATE SATURDAY NIGHT. COLD FRONT APPROACHES LATE MONDAY...CROSSING ON TUESDAY. HIGH CHANCES FOR THUNDERSTORMS ACCOMPANYING FRONT...LATE MONDAY NIGHT INTO TUESDAY. MORE HIGH PRESSURE THEN TUESDAY NIGHT INTO THURSDAY. && .MARINE... NLY FLOW 10 TO 15 KT SATURDAY BEHIND THE COLD FRONT. GUSTS MAY REACH 18KT...SO A SMALL CRAFT ADVISORY MAY BE NEEDED. HIGH PRESSURE THEN BUILDS FROM THE NORTH THROUGH SUNDAY...ALLOWING A LIGHT ELY FLOW/BAY BREEZE SUNDAY. RETURN FLOW LATE SUNDAY THROUGH MONDAY NIGHT MAY CHANNEL AND GUST INTO THE MARGINAL SMALL CRAFT ADVISORY ZONE. A COLD FRONT CROSSES THE BAY IN THE TUESDAY TIMEFRAME...WITH HIGH CHANCES FOR THUNDERSTORMS. HIGH PRESSURE THEN BUILDS FROM THE NORTH WITH NLY FLOW THROUGH MIDDLE NEXT WEEK && .HYDROLOGY... FLASH FLOOD WATCH HAS BEEN DROPPED. && .EQUIPMENT... PIKESVILLE NWR WENT DOWN LAST NGT DUE TO A LIGHTNING STRIKE ON A COMMERCIAL POWER TRANSFORMER. TECHS ARE WORKING THE ISSUE...AND WILL DO THEIR BEST TO RETURN SERVICE TODAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && UPDATE...WOODY! PRVS...HTS/BAJ
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 145 AM EDT SAT JUL 9 2011 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 091100- 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- 145 AM EDT SAT JUL 9 2011 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...SUNDAY THROUGH FRIDAY 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>506-091100- 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- 145 AM EDT SAT JUL 9 2011 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...SUNDAY THROUGH FRIDAY 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.
5 dense fog. Local standard time, as filed.
Visibilities were measured to be one quarter mile or less at the Shenandoah Valley Airport.
Visibilities were estimated to be around a quarter mile due to observations nearby.
Visibilities were measured to be one quarter mile or less at Luray.
Visibilities were estimated to be around a quarter mile due to observations nearby.
Visibilities were estimated to be around a quarter mile due to observations nearby.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Virginia in 2011Every state in 2011This day in weather historyWarnings in Virginia, July 2011
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: 338528, 338530, 338529, 338531, 338532.