An onshore flow continued to cause elevated water levels along the Tidal Potomac River near Alexandria.
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The episode as NWS LWX wrote it up.
An onshore flow continued to cause elevated water levels along the Tidal Potomac River near Alexandria.
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 May 20, 5:46 AM EST, 3 hours 8 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 646 AM EDT FRI MAY 20 2011 .SYNOPSIS... AN UPPER-LEVEL LOW WILL CONTINUE TO MOVE NORTHEAST OF THE AREA TODAY WHILE HIGH PRESSURE APPROACHES FROM THE WEST. HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT THROUGH SATURDAY BEFORE MOVING OFF THE EAST COAST SUNDAY. A RETURN FLOW WILL USHER IN WARM AND HUMID CONDITIONS EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... UPPER-LEVEL LOW PRESSURE JUST TO OUR NORTHEAST THIS MORNING WILL CONTINUE TO SLOWLY MOVE AWAY FROM THE REGION THIS AFTERNOON AS IT MOVES OFF THE JERSEY COAST. UPPER-LEVEL DISTURBANCES WILL ROTATE AROUND THIS SYSTEM PASSING THROUGH OUR REGION TODAY. INSTABILITY WILL REMAIN LIMITED DUE TO DRIER AIR MOVING IN BEHIND THE UPPER-LEVEL LOW. HOWEVER...THERE WILL BE ENOUGH INSTABILITY FOR SCATTERED SHOWERS/ISOLATED T-STORMS MAINLY DURING THE AFTERNOON HOURS WHEN INSTABILITY WILL BE HIGHEST. MAX TEMPS WILL RANGE FROM THE 60S IN THE MOUNTAINS TO THE 70S ACROSS MOST OTHER LOCATIONS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... HIGH PRESSURE WILL SLOWLY BUILD OVER THE REGION TONIGHT WHILE THE UPPER-LEVEL LOW CONTINUES TO MOVE AWAY FROM THE AREA. LEFTOVER CONVECTION THIS EVENING WILL DISSIPATE DUE TO THE LOSS OF DAYTIME HEATING AND THE APPROACHING SURFACE HIGH. MIN TEMPS WILL RANGE FROM THE 40S IN THE MOUNTAINS TO NEAR 60 IN WASHINGTON AND BALTIMORE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... UPPER LEVEL RIDGE AXIS ADVANCES EAST TOWARD THE MID ATLANTIC SATURDAY AND THEN MOVES INTO THE AREA SATURDAY NIGHT. WEAK TAIL OF A VORT MAX IN NORTHWEST FLOW ALOFT MAY SCRAPE THE NORTHEAST PORTION OF THE CWA WITH SOME CLOUDS ON SATURDAY BUT IT LOOKS LIKE ANY CONVECTION SHOULD STAY NORTHEAST OF THE CWA AND IT WILL BE A MIX OF SUN AND CLOUDS SORT OF DAY. HIGH TEMPERATURES MAY WARM BACK TO THE 80 DEGREE MARK. A BACKDOOR BOUNDARY WILL BE CLOSE...BUT LIKELY JUST NORTHEAST OF THE CWA SUNDAY MORNING. RIDGE AXIS OVERHEAD SLIDES EAST BY SUNDAY AFTERNOON ALLOWING SOUTHWEST FLOW ALOFT TO DEVELOP. THIS WILL CONTINUE THE WARMING TREND. IN ADDITION...SURFACE WINDS FROM THE SOUTH WILL LEAD TO INCREASING MOISTURE. MODELS SHOW A SHORTWAVE MOVING THROUGH IN THE AFTERNOON AND EVENING. THERE WILL LIKELY BE 500-1000 J/KG OF CAPE AS WELL...AND THUS HAVE INCREASED POPS INTO THE CHANCE CATEGORY FOR THE ENTIRE CWA FOR SHRA/TSRA DURING THIS TIME. UPPER FLOW FLATTENS OUT AND BECOMES NEARLY ZONAL FOR THE EARLY TO MID WEEK PERIOD. THERE WILL BE DISTURBANCES IN THIS FLOW BUT IT LOOKS LIKE THE GREATEST IMPACT WOULD ACROSS THE NORTHWEST. MEANWHILE...HAVE BOOSTED MAX T AS THE WARMING TREND SHOULD CONTINUE. FLOW MAY AMPLIFY MORE TOWARD THE END OF THE WEEK...WHICH COULD SEND A COLD FRONT THROUGH THE CWA WITH A BETTER CHANCE OF CONVECTION ACROSS THE ENTIRE CWA AS WELL. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS ARE EXPECTED ACROSS THE TERMINALS THIS MORNING. AN UPPER-LEVEL LOW WILL TRIGGER SCATTERED SHOWERS AND ISOLATED T-STORMS THIS AFTERNOON AND EVENING. HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT...BRINGING A RETURN OF DRY CONDITIONS. HIGH PRESSURE BUILDS IN SATURDAY. TROUGH OF LOW PRESSURE WILL BRING A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON. HIGH PRESSURE WILL BE OFF THE MID ATLANTIC COAST THROUGH MID WEEK...WITH UPPER LEVEL DISTURBANCES IN ZONAL FLOW PROVIDING A SMALL CHANCE OF MAINLY AFTERNOON THUNDERSTORMS. && .MARINE... UPPER-LEVEL LOW PRESSURE WILL SLOWLY MOVE AWAY FROM THE WATERS TODAY. SCATTERED SHOWERS/ISOLATED T-STORMS ARE EXPECTED THIS AFTERNOON AND EVENING. AN ISOLATED T-STORM MAY BRING GUSTY WINDS. HIGH PRESSURE WILL BUILD TOWARD THE WATERS TONIGHT. RIDGE OF HIGH PRESSURE MOVES IN FOR SATURDAY. BACKDOOR BOUNDARY SHOULD REMAIN NORTH OF THE WATERS...ALLOWING A SOUTHERLY FLOW FOR SUNDAY. SOUTHERLY FLOW COULD FLIRT WITH SCA CONDITIONS TOWARD LATE AFTERNOON/EVENING. IN ADDITION...MODELS SHOW A SHORTWAVE MOVING THROUGH WITH A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON/EVENING. HIGH PRESSURE WILL REMAIN ACROSS THE WESTERN ATLANTIC THROUGH THE MIDDLE OF NEXT WEEK. && .HYDROLOGY... MINOR FLOODING CONTINUES ACROSS MANY PORTIONS OF THE LOWER POTOMAC RIVER THIS MORNING. RIVER LEVELS HAVE CRESTED ACROSS ALL LOCATIONS AND WILL CONTINUE TO COME DOWN TODAY. HOWEVER...LEVELS SHOULD REMAIN ABOVE FLOOD STAGE FOR MOST OF THE DAY. MODERATE FLOODING AT POINT OF ROCKS WILL RECEDE TO MINOR FLOODING LATER THIS MORNING. ALL RIVER LEVELS SHOULD GO BELOW FLOOD STAGE BY LATE THIS EVENING. && .TIDES/COASTAL FLOODING... WILL CONTINUE WITH A COASTAL FLOOD WARNING FOR AREAS NEAR THE TIDAL POTOMAC RIVER IN WASHINGTON DC AND ALEXANDRIA THROUGH LATE THIS EVENING. FRESH WATER FROM THE POTOMAC RIVER CONTINUES TO PRODUCE MODERATE FLOODING ESPECIALLY NEAR WASHINGTON DC. WATER LEVELS CONTINUE TO REMAIN AROUND 8 FEET THIS MORNING AT WISCONSIN AVENUE. THE POTOMAC RIVER AT LITTLE FALLS HAS CRESTED EARLY THIS MORNING. THEREFORE...THE HIGHEST WATER LEVELS ARE LIKELY NEAR THE TIME OF HIGH TIDE LATE THIS MORNING. WATER LEVELS AT WISCONSIN AVENUE MAY APPROACH 9 FEET. MODERATE FLOODING WILL LIKELY CONTINUE THIS AFTERNOON INTO THIS EVENING...BUT WATER LEVELS MAY COME DOWN CLOSER TO 7 FEET AT WISCONSIN AVENUE BY THIS EVENING. MINOR FLOODING MAY CONTINUE OVERNIGHT INTO SATURDAY. ELSEWHERE...TIDAL ANOMALIES ARE AROUND ONE HALF TO THREE QUARTERS OF A FOOT ABOVE NORMAL EARLY THIS MORNING. A LIGHT OFFSHORE FLOW WILL LIKELY CAUSE ANOMALIES TO SLOWLY DECREASE. WILL CONTINUE TO WATCH WATER LEVELS DURING THE HIGH TIDE CYCLE THIS MORNING...BUT THEY SHOULD REMAIN JUST BELOW THRESHOLDS FOR MINOR COASTAL FLOODING. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...COASTAL FLOOD WARNING UNTIL 2 AM EDT SATURDAY FOR DCZ001. MD...NONE. VA...COASTAL FLOOD WARNING UNTIL 2 AM EDT SATURDAY FOR VAZ054. WV...NONE. MARINE...NONE. && SYNOPSIS...BJL/BPP NEAR TERM...BJL SHORT TERM...BJL LONG TERM...BPP AVIATION...BJL/BPP MARINE...BJL/BPP HYDROLOGY... TIDES/COASTAL FLOODING...
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 739 AM EDT FRI MAY 20 2011 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 211000- 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- 739 AM EDT FRI MAY 20 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...TODAY AND TONIGHT A COASTAL FLOOD WARNING IS IN EFFECT FOR WASHINGTON DC AND ALEXANDRIA. PLEASE REFER TO THE LATEST HAZARD MESSAGE /CFWLWX/ FOR DETAILS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY MINOR COASTAL FLOODING MAY CONTINUE INTO SATURDAY NEAR WASHINGTON DC AND ALEXANDRIA. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME. MDZ003>005-009-010-501-502-VAZ025>031-036>040-042-050-051-501>504- WVZ050>053-055-501>506-211000- 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- 739 AM EDT FRI MAY 20 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...TODAY AND TONIGHT MINOR TO MODERATE RIVER FLOODING WILL CONTINUE ALONG THE POTOMAC RIVER FROM POINT OF ROCKS SOUTHWARD. PLEASE REFER TO THE LATEST RIVER FLOOD MESSAGES FOR DETAILS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME. KRAMAR
The national radar mosaic for the moment the first event began.
1 coastal flood. Local standard time, as filed.
Water levels at Alexandria were above thresholds for moderate coastal flooding.
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, May 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: 314989.