High pressure centered overhead caused light winds. Light winds along with high amounts of low-level moisture allowed for areas of fog to develop during the early morning hours of the 2nd.
Every event with a place to put it; 1 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 centered overhead caused light winds. Light winds along with high amounts of low-level moisture allowed for areas of fog to develop during the early morning hours of the 2nd.
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 Sep 1, 8:12 PM EST, 6 hours 32 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 912 PM EDT THU SEP 1 2011 .SYNOPSIS... A RIDGE OF HIGH PRESSURE WILL REMAIN ALONG THE EAST COAST ON FRIDAY AND THEN MOVE OFFSHORE ON SATURDAY. A COLD FRONT WILL CROSS THE REGION SUNDAY INTO MONDAY FOLLOWED BY HIGH PRESSURE FOR THE MIDDLE PART OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... RDG OF SFC HIPRES CONTS ALONG THE ERN SEABOARD. HWVR...ALOFT THINGS ARE A-CHANGING. NOSE OF H8 THERMAL RDG POKING INTO GRTLKS...W/ A STRONG WAA PTTN STRETCHING FM ONT TO VA/NC. A H5 S/WV CRASHING DOWN ERN SIDE OF THIS RDG RESPONSIBLE FOR SHRA/TSRA ERLR TAFTN. UNFORTUNATELY...PRACTICALLY ALL GDNC /18Z SYNOPTIC AND MESOSCALE/WRF/HRRR/ SUGGESTING MORE PCPN POTENTIAL OVERNIGHT. CWFA SITUATED IN A LOCATION WHERE ITS LIABLE TO HAPPEN. 18Z GFS IS THE MOST OPTIMISTIC OF THE BUNCH...SUGGESTING THAT PTS N/NW MORE SUSCEPTIBLE THAN LCL AREA. HV ADJUSTED POPS IN DATABASE...AND WL BE RUNNING W/ CHC POPS OVNGT. 18Z NAM SUGGESTING WE/RE TOO STBL FOR THUNDER...AND 00Z LWX RAOB REVEALS MORE CIN THAN CAPE. THREFORE...TEND TO AGREE W/ GFS IMPLICATION THAT THE STRONGEST ACTIVITY WON/T OCCUR LCLLY...AND PCPN TYPE TILTED MORE TWD SHRA...IN SPITE OF VIGOROUS CELL IN N-CENTRL PA ATTM. HWVR...PCPN POTENTIAL WL...AT THE VERY LEAST... LEAD TO QUITE A BIT OF CLDCVR. HV BEEN CROSS CHECKING TEMPS/DEWPTS AGAINST LAMP...AND WL CONT TO DO SO. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... THE WX SHOULD BE RELATIVELY QUIET DURG THIS PERIOD AS A HIGH PRES RIDGE AXIS IS MAINTAINED OVER THE AREA AT THEE SURFACE AND ALOFT. NO SGFNT SHRTWVS OR FEATURES ALOFT ARE FCST TO AFFECT THE AREA. A SLGT CHCH FOR MAINLY DIURNALLY-DRIVEN SHRA/TSRA HAS BEEN MAINTAINED FOR THE WESTERN PART OF THE FCST AREA. MAX/MIN TEMPS ARE FCST TO BE NEAR NORMAL WITH JUST A LIGHT SELY WIND FLOW AROUND THE SURFACE RIDGE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... A COLD FRONT WILL MOVE TOWARD THE REGION THIS WEEKEND. AHEAD OF IT FEEL CONFIDENT A WARM AND MOIST AIRMASS WILL ADVECT INTO THE REGION LEADING TO HOT AND HUMID CONDITIONS, WITH THE CHANCE FOR URBAN AREAS TO REACH 90 COUPLED WITH A DEWPOINT AROUND 70. THIS MAY ALLOW THE HEAT INDEX TO FLIRT AROUND THE 95 DEGREE MARK THIS WEEKEND IN URBAN AREAS, FOR NOW WILL NOT ISSUE ANY STATEMENTS BUT WILL MONITOR TRENDS CLOSELY. THIS FRONTAL BOUNDARY WILL PROVIDE LIFT COUPLED WITH AMPLE INSTABILTY AND MOISTURE AHEAD OF THE FRONT FOR THE DELEVOPMENT OF SHOWERS AND THUNDERSTORMS FOCUSED ON THE TIME PERIOD FROM SUNDAY AFTERNOON AND LASTING INTO MONDAY, RAISED CHANCES TO LIKELY FOR SUNDAY NIGHT BASED ON HPC GUIDENCE AND GOOD AGREEMENT FROM THE ECMWF AND GFS. THIS FRONT MAY SLOW A BIT MONDAY NIGHT BUT FOR NOW FEEL ANY RAIN CHANCES WILL BE SOUTHEAST OF THE REGION. MARGINAL SHEAR AND SOME CIN MAY LIMIT A SEVERE THREAT. HOWEVER EVEN WITH LOW SHEAR IN AN UNSTABLE ENVIORNMENT MARKED BY MODERATE CAPE OF OVER 1000 J/KG AND STEEP LOW LEVEL LAPSE RATES ON MODEL SOUNDINGS SUNDAY AFTERNOON AND EVENING MAY ALLOW FOR SOME STORMS TO BECOME SEVERE WITH A THREAT FOR DAMAGING WINDS AND HAIL. AS A RESULT THE SPC HAS INCLUDED THE REGION IN A DAY 4 OUTLOOK. ANY POTENTIAL SEVERE THREAT WILL BE MONITORED OVER THE NEXT SEVERAL DAYS. WILL NOT ADD SEVERE PARAMETERS TO GRIDS AT THIS TIME GIVING FUTURE SHIFTS A CHANCE TO FINE TUNE THE THREAT. ONCE THIS FRONT PASSES THROUGH MONDAY NIGHT HIGH PRESSURE WILL MOVE INTO THE REGION THROUGHOUT THE REMAINDER OF THE WEEK WITH COOLER CONDITIONS AND FAIR SKIES. ONE POTENTIAL WRINKLE TO THIS FORECAST IS A TROPICAL DISTURBANCE EXPECTED TO FORM IN THE GULF WHICH MAY MOVE ALONG THE FRONTAL BOUNDARY SOMETIME NEXT WEEK CLOSE TO OUR REGION AS SHOWN ON SEVERAL OF THE GFS ENSEMBLE MEMBERS AND THE 12Z GFS. HOWEVER AT THIS TIME AGREE WITH HPC GUIDENCE ON THIS FEATURE KEEPING IT AWAY FROM OUR REGION AND THE FORECAST DRY. RAIN CHANCES MAY NEED TO BE ADDED LATER THIS WEEK IF OTHER GUIDENCE TRENDS TOWARD THE 12Z GFS. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... VFR SHUD GENLY PREVAIL THRU FRI. HWVR...THERE/S A POTENTIAL FOR SHRA/TSRA TO DVLP OVNGT. AM UNCERTAIN REGARDING CVRG IN TERMS OF A PT FCST...SO HV LEFT CIGS AT 4000 FT OVNGT...AND GNLY HVNT TAKEN ANY VSBY RESTRICTIONS. ANY POTENTIAL OVNGT PCPN ACTIVITY WUD CLEAR BY THE MRNG PUSH...W/ NO FLGT RESTRICTIONS ANTICIPATED THRU THE DAY. FLOW WUD PRIMARILY BE SLY/SELY...BUT WNDSPD SHUDNT BE A BIG OPERATIONAL IMPACT. BEYOND FRIDAY...THE MAIN POTENTIAL FOR FLIGHT RESTRICTIONS WOULD BE SCATTERED SHOWERS AND T-STORMS AHEAD OF AN APPROACHING COLD FRONT. THE FRONT IS FORECAST TO MOVE THOUGH ON MONDAY MORNING... FOLLOWED BY FAIR WX. && .MARINE... SLY FLOW 10-15 KT ATTM AHD OF UPA RDG. DO NOT ANTICIPATE SCA CONDS...BUT AT THE SAME TIME DONT XPCT A TRANQUIL NGT EITHER. SLY CHANNELING MAY DEVELOP AGN FRI AFTN AND OVER THE WEEKEND WITH THE HIGH PRESS AXIS SHIFTING A LITTLE MORE EWD. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && SYNOPSIS... NEAR TERM...HTS SHORT TERM...99PHI LONG TERM...99PHI AVIATION...HTS/CJL/99PHI MARINE...HTS/99PHI
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 551 AM EDT THU SEP 1 2011 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 021000- 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- 551 AM EDT THU SEP 1 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 NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE OVER PORTIONS OF THE TIDAL POTOMAC RIVER AND MARYLAND CHESAPEAKE BAY SATURDAY EVENING. .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>506-021000- 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- 551 AM EDT THU SEP 1 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 NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.
The national radar mosaic for the moment the first event began.
1 dense fog. Local standard time, as filed.
Visibility was reported to be around one quarter mile.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2011Every state in 2011This day in weather historyWarnings in Maryland, September 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: 347988.