High pressure across most of the Northeast and Mid Atlantic led to the development of dense fog across the region. Light winds and saturated low levels aided in fog development.
Every event with a place to put it; 6 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 across most of the Northeast and Mid Atlantic led to the development of dense fog across the region. Light winds and saturated low levels aided in fog development.
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 Dec 9, 10:43 PM EST, 3 hours 35 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1043 PM EST SUN DEC 9 2012
.SYNOPSIS...
A WARM FRONT WILL SLOWLY PASS THROUGH THE AREA LATE TONIGHT INTO
MONDAY. A COLD FRONT WILL PASS THROUGH THE AREA MONDAY NIGHT
BEFORE HIGH PRESSURE BUILDS OVERHEAD DURING THE MIDDLE AND LATTER
PORTIONS OF THE WEEK.
&&
.NEAR TERM /THROUGH MONDAY/...
...UPDATE TO ADD DENSE FOG ADVISORY FOR ALL LOCATIONS ALONG AND
EAST OF THE BLUE RIDGE MOUNTAINS AND ALSO FOR PORTIONS OF EASTERN
WEST VIRGINIA AND NORTHERN MARYLAND. VISIBILITIES ARE EXPECTED TO
DROP TO NEAR OR BELOW ONE QUARTER MILE AT TIMES...ESPECIALLY AFTER
MINIGHT. PREVIOUS DISCUSSION FOLLOWS...
LOW PRESSURE OVER THE OHIO VALLEY THIS EVENING WILL MOVE NORTHEAST
INTO THE GREAT LAKES OVERNIGHT. A WARM FRONT CURRENTLY EXTENDS
SOUTHEAST FROM THE LOW THROUGH EASTERN WEST VIRGINIA INTO CENTRAL
VIRGINIA. AN ONSHORE FLOW HAS LED TO PLENTY OF LOW CLOUDS ALONG
WITH AREAS OF FOG NORTH OF THE BOUNDARY OVER OUR CWA.
THE BOUNDARY WILL SLOWLY LIFT NORTH TONIGHT...BUT THE COOL AIR
NEAR THE SURFACE WILL LIKELY REMAIN TRAPPED...KEEPING LOW CLOUDS
AND FOG IN PLACE THROUGH THE OVERNIGHT. DESPITE THE STRATUS
DECK...VSBYS ARE EXPECTED TO DROP OVERNIGHT DUE TO THE DECREASING
DEPTH OF THE MARINE LAYER. A DENSE FOG ADVISORY IS IN EFFECT FOR
ANNE ARUNDEL...CALVERT AND ST MARYS COUNTIES AND THE DENSE FOG
ADVISORY MAY NEED TO EXPANDED FURTHER NORTH AND WEST INTO THE
WASHINGTON/BALTIMORE METROPOLITAN AREAS AS WELL AS NORTHERN VA AND
EASTERN WEST VIRGINIA. WILL CONTINUE TO MONITOR VSBYS LATE THIS
EVENING/OVERNIGHT.
AREAS OF RAIN/DRIZZLE ARE EXPECTED LATE THIS EVENING DUE TO A
STRENGTHENING LOW-LEVEL JET AND ISENTROPIC LIFT. COVERAGE OF
PRECIPITATION IS EXPECTED TO DECREASE OVERNIGHT AS MOST OF THE
FORCING/LIFT DRIFT OFF TO OUR NORTH.
ALTHOUGH THE INVERSION IS SHALLOW...AND THE SFC HIGH BY MONDAY
MORNING TAKES ON AN ORIENTATION THAT IS NOT AS IDEAL FOR THE
INVERSION TO BE ABLE TO PERSIST...I STILL DELAYED THE TAKEOVER OF
THE BOUNDARY LAYER AIRMASS BY SEVERAL HOURS. ANYWHERE THAT BREAKS
OUT DECENTLY COULD SEE HIGHS PUSHING 70...BUT JUST TO UNDERSCORE THE
UNCERTAINTY...I HAVE A 5 DEG F TEMP GRADIENT ACROSS SEVERAL OF OUR
COUNTIES...AND NEARLY A 20 DEG F GRADIENT ACROSS THE CWFA. PRECIP
CHANCES START OUT SMALL...BUT INCREASE STEADILY THROUGHOUT THE DAY
AS A COLD FRONT APPROACHES FROM THE WEST. ISOLATED THUNDER IS
POSSIBLE IN THE AFTERNOON.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
THE COLD FRONT WILL MOVE THROUGH MONDAY NIGHT...BRINGING COLDER
AIR THAT WILL CHANGE ANY UPSLOPE RAIN SHOWERS TO SNOW SHOWERS IN
THE WESTERN MOUNTAINS...WITH NOT MUCH SNOW ACCUMULATION EXPECTED.
HIGH PRESSURE BUILDS ACROSS THE AREA ON TUE
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
RELATIVE LONG STRETCH OF HIGH PRESSURE EXPECTED FOR THE MAJORITY
OF THE WEEK AS GUIDANCE IN PRETTY GOOD AGREEMENT ON HIGH PRESSURE
SETTLING ACROSS THE REGION TUE AND EXTENDING THROUGH FRI. THE
WEEKEND WILL SEE HIGH PRES RETREAT NORTHEAST AS LOW PRESSURE IN
THE SOUTHERN PLAINS DEVELOPS ON SATURDAY AND HEADS FOR THE UPPER
MIDWEST BY MONDAY. EXPECT ABOVE NORMAL TEMPS THROUGH THE EXTENDED
AND DRY CONDITIONS...WITH SOME FOG IN THE MORNINGS POSSIBLE THU-
FRI-SAT.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
IFR/LIFR CIGS/VSBYS THIS EVENING MAY DROP TO VLIFR CONDITIONS
OVERNIGHT. CIGS/VSBYS WILL GRADUALLY IMPROVE MONDAY MORNING AS A
WARM FRONT PASSES THROUGH THE AREA. SOUTHERLY WINDS WILL GUST
AROUND 20 KNOTS BEHIND THE WARM FRONT MONDAY AFTERNOON...BUT CIGS
AND VSBYS WILL REMAIN AT VFR/MVFR LEVELS.
SHRA/ISOLATED TSRA ARE EXPECTED MONDAY AFTN/EVENING AHEAD OF THE
NEXT COLD FRONT. A FEW SHOWERS AND MVFR TO LOCALLY IFR CIGS ARE
POSSIBLE WITH THE PASSAGE OF THE COLD FRONT MONDAY NIGHT INTO
TUESDAY. NW GUSTS OF AROUND 20 KT EXPECTED TUESDAY.
TUE THROUGH FRI...EXPECT HIGH PRESSURE/VFR THROUGH THE REMAINDER
OF WEEK...WITH LOW CHANCES OF LATE NIGHT AND EARLY MORNING FOG IS
POSSIBLE THU AND FRI.
&&
.MARINE...
SPLIT THE EXISTING SCA A BIT...TO START IT SOONER ON THE OPEN WATERS
THAN THE UPPER/MIDDLE TIDAL POTOMAC. ULTIMATELY THOUGH...SOUTHERLY
CHANNELING WILL CREATE SOLID SCA CONDITIONS ON ALL THE WATERS MONDAY.
THE COLD FRONT CROSSES MONDAY NIGHT...WITH SCA CONDITIONS EXPECTED
MON OVERNIGHT INTO EARLY TUE. HOWEVER GRADIENT IS EXPECTED TO
WEAKEN QUICKLY ON TUE...SO ATTM DO NOT PLAN TO EXTEND SCA BEYOND
TUE MORNING.
&&
.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES REMAIN AROUND ONE HALF TO THREE QUARTERS OF A FOOT
ABOVE NORMAL THIS EVENING. SOUTHERLY WINDS ARE EXPECTED TO DEVELOP
LATE TONIGHT AND INCREASE ON MONDAY...CAUSING TIDAL ANOMALIES TO
INCREASE.
FOR COASTAL FLOOD POTENTIAL...LITTLE CONCERN WITH THE HIGH TIDE
CYCLE OVERNIGHT INTO MONDAY MORNING SINCE IT IS THE LOWER OF THE
TWO ASTRONOMICAL HIGH TIDES AND THE SOUTHERLY FLOW WILL NOT HAVE
TAKEN OVER YET.
THE INCREASING TIDAL ANOMALIES AND SOUTHERLY FLOW DOES POSE A
THREAT FOR MINOR FLOODING ALONG THE WESTERN SHORE OF THE
CHESAPEAKE BAY AND THE SHORE OF THE TIDAL POTOMAC RIVER. A COASTAL
FLOOD ADVISORY MAY BE NEEDED FOR THE HIGH TIDE CYCLE LATE MONDAY
MORNING INTO MONDAY NIGHT.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR DCZ001.
MD...DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR MDZ003>007-
009>011-013-014-016>018.
VA...DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR VAZ036>040-042-
050>057-501-502.
WV...DENSE FOG ADVISORY UNTIL 9 AM EST MONDAY FOR WVZ051>053.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM MONDAY TO 7 AM EST TUESDAY FOR
ANZ530>534-537>543.
SMALL CRAFT ADVISORY FROM 9 AM MONDAY TO 7 AM EST TUESDAY FOR
ANZ535-536.
&&
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1046 PM EST SUN DEC 9 2012 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 101000- 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- 1046 PM EST SUN DEC 9 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...TONIGHT A DENSE FOG ADVISORY IS IN EFFECT TONIGHT FOR THE OUTLOOK AREA. PLEASE REFER TO THE LATEST HAZARD MESSAGE /WBCNPWLWX/ FOR FURTHER DETAILS. A SMALL CRAFT ADVISORY IS IN EFFECT LATE TONIGHT FOR THE CHESAPEAKE BAY AND LOWER TIDAL POTOMAC. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE DENSE FOG ADVISORY CONTINUES UNTIL MID MORNING. A SMALL CRAFT ADVISORY IS IN EFFECT MONDAY AND MONDAY NIGHT ON ALL WATERS OF THE CHESAPEAKE BAY AND TIDAL POTOMAC. THE SMALL CRAFT ADVISORY MAY NEED TO BE EXTENDED INTO TUESDAY. MINOR COASTAL FLOODING IS POSSIBLE MONDAY AROUND THE TIME OF HIGH TIDE ALONG THE WESTERN SHORE OF THE CHESAPEAKE BAY AND THE MOST SUSCEPTIBLE PORTIONS OF THE TIDAL POTOMAC. .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>506-101000- 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- 1046 PM EST SUN DEC 9 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...TONIGHT A DENSE FOG ADVISORY IS IN EFFECT TONIGHT FOR THE CENTRAL AND NORTHERN VIRGINIA COUNTIES EAST OF THE BLUE RIDGE...THE EASTERN PANHANDLE OF WEST VIRGINIA AND NORTH-CENTRAL MARYLAND. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE DENSE FOG ADVISORY CONTINUES UNTIL MID MORNING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The national radar mosaic for the moment the first event began.
6 dense fog. Local standard time, as filed.
Visibility was reported to be around one quarter mile at Cumberland Airport.
Visibility was reported to be around one quarter mile at Petersburg Airport.
Visibility was reported to be around one quarter mile at Petersburg Airport.
Visibility was reported to be around one quarter mile at Martinsburg Airport.
Visibility was reported to be around one quarter mile at Martinsburg and Cumberland airports.
Visibility was reported to be around one quarter mile at Martinsburg airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in West Virginia in 2012Every state in 2012This day in weather historyWarnings in West Virginia, December 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: 426821, 426822, 426823, 426820, 426824, 426825.