A surface trough was draped across the Mid Atlantic from the panhandle of WV through North-Central Maryland and Northern Virginia and then Southern Maryland. Northerly flow north of the surface trough led to a cold air damming where trapped low clouds and fog developed and persisted in Northern Maryland.
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.
A surface trough was draped across the Mid Atlantic from the panhandle of WV through North-Central Maryland and Northern Virginia and then Southern Maryland. Northerly flow north of the surface trough led to a cold air damming where trapped low clouds and fog developed and persisted in Northern Maryland.
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 7, 9:06 PM EST, 4 hours 12 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 906 PM EST FRI DEC 7 2012 .SYNOPSIS... THERE IS ONE AREA OF HIGH PRESSURE SOUTH OF LONG ISLAND AND ANOTHER NORTH OF MINNESOTA. IN BETWEEN IS A WEAK FRONTAL BOUNDARY EXTENDING FROM MICHIGAN TO TEXAS. THIS WILL MOVE SLOWLY TOWARDS THE EAST COAST SATURDAY EVENING. THE NEXT COLD FRONT WILL AFFECT THE REGION EARLY IN THE WEEK. HIGH PRESSURE WILL BUILD INTO THE REGION DURING THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/... THERE WL BE XTNSV CLD CVR OVR THE MID ATLC TNGT AND SAT AS A WEAK FNTL BNDRY SLOWLY WORKS ITS WAY TOWARDS THE AREA. AN AREA OF LGT RAIN IS PERSISTING OVER LWR SRN MD SO HV INCRSD THE POPS FM CHC TO LKLY THRU THE EVENG. EXPECT RAIN TO CONTINUE UP ALONG THE MASON-DIXON...PARTICULARLY WASHINGTON CO MD AND WEST. LIGHT SHOWERS AND SPRINKLES WILL CONTINUE TO LIFT FROM SRN VA ACROSS SRN MD THROUGH THIS EVENING WITH ISENTROPIC LIFT. IN BETWEEN /MAINLY ACROSS THE BALT-WASH METRO/LOW CLOUDS WILL DEVELOP AND DRIZZLE IS POSSIBLE TONIGHT. TEMPERATURES IN THE M40S OVERNIGHT. SATURDAY...LOW PRESSURE DEVELOPING TONIGHT OVER THE MIDWEST AHEAD OF THE UPR TROUGH AXIS WILL SEND A LOW LEVEL TROUGH THROUGH THE MID ATLANTIC. SWLY FLOW WILL HELP TO MIX DOWN 8C 850MB TEMPS. EXPECT MAX TEMPS INTO THE 60S ACROSS THE AREA...PERHAPS UPR 60S KCHO AND SOUTH. LITTLE PRECIP ACROSS THE AREA...LIMITED ONLY TO THE ALLEGHENY HIGHLANDS. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... COOL AND DAMP EAST/NORTHEAST FLOW WILL TAKE SHAPE SATURDAY NIGHT AND CONTINUE SUNDAY AS THE FRONT SLOWLY SEEPS SOUTHWARD ACROSS THE REGION AND HIGH PRESSURE SETS UP TO THE NORTH. WARM AIR ADVECTION WILL PERSIST ABOVE THE COOL SURFACE LAYER LEADING TO PERIODS OF LIGHT RAIN ESPECIALLY OVER WESTERN AND NORTHERN PORTIONS OF THE THE FORECAST AREA SUNDAY MORNING INTO THE EARLY AFTERNOON. TRENDED AFTERNOON HIGH TEMPERATURES DOWN FOR SUNDAY AFTERNOON WITH MUCH OF THE GUIDANCE INDICATING THAT HIGH TEMPERATURES WILL NOT MAKE IT OUT OF THE 40S IN MANY LOCATIONS. THIS WILL DEPEND ON HOW FAR SOUTH THE COLD FRONT PUSHES. LOW CLOUDS AND AREAS OF FOG WILL PERSIST IN EASTERLY FLOW SUNDAY NIGHT INTO MONDAY BEFORE THE FLOW VEERS TO SOUTHERLY AHEAD OF THE NEXT COLD FRONTAL PASSAGE. TEMPERATURES MONDAY WILL LIKELY RISE INTO THE 60S EAST OF THE BLUE RIDGE WITH 65-70 OVER DC AND SOUTHERN MD IF ENOUGH CLEARING TAKES SHAPE. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... THE COLD FRONT WILL SWEEP ACROSS THE FORECAST AREA MONDAY AFTERNOON INTO MONDAY NIGHT WITH RAIN SHOWERS LIKELY INCREASING IN COVERAGE FROM WEST TO EAST. MODELS INDICATE THAT AN AREA OF LOW PRESSURE MAY DEVELOP ALONG THE FRONT AND TRACK NORTHEAST OFF THE MIDDLE ATLANTIC COAST ON TUESDAY. THIS WOULD KEEP THE PRECIPITATION GOING INTO TUESDAY BEFORE THE ENTIRE TROUGH PUSHES EAST OF THE FORECAST AREA. BY MONDAY NIGHT...COLDER AIR WILL HAVE FILTERED INTO THE REGION AND THE RAIN SHOWERS MAY MIX WITH AND CHANGE TO SNOW SHOWERS OVER THE WESTERN FIVE. SOME VERY LIGHT ACCUMULATIONS MAY BE POSSIBLE OVER THE HIGHER ELEVATIONS. HIGH PRESSURE WILL BUILD ACROSS THE MIDDLE ATLANTIC THROUGH MID WEEK WHICH WILL HELP KEEP ANOTHER STORM SYSTEM PRESSED TO OUR SOUTH ON THURSDAY. LONG RANGE MODELS CONTINUE TO INDICATE A RATHER PROGRESSIVE UPPER LEVEL FLOW PATTERN ACROSS THE CONUS WITH SYSTEMS MOVING RAPIDLY EAST WITHOUT THE PRESENCE OF COLD AIR. ANOTHER IN A SERIES OF STORMS MAY IMPACT THE REGION FROM THE WEST NEXT WEEKEND. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... CIGS XPCTD TO RMN LOW TNGT W/ PDS OF RA/DZ PSBL. W/ OVC SKIES DO NOT BLV FOG WL BE HAT MUCH OF A PROB OVRNGT. LIGHT SFC SLY FLOW SOUTH OF THIS FRONT...LIGHT AND VARIABLE FLOW ALONG/NORTH OF THE BOUNDARY. SAT LOOKS TO BE CLDY...ALTHO CIGS SHOULD BE IN VFR RANGE. LOW CLOUDS AND SOME FOG WILL BE POSSIBLE SATURDAY NIGHT INTO SUNDAY AS WELL AS SUNDAY NIGHT INTO MONDAY. PERIODS OF LIGHT RAIN MAY ALSO HELP REDUCE CIGS AND VSBYS INTO THE SUB-VFR RANGE. A COLD FRONT WILL PUSH EAST ACROSS THE REGION BRINGING A MORE WIDESPREAD POTENTIAL FOR RAIN SHOWERS MONDAY INTO TUESDAY. VFR RETURNS FOR WEDNESDAY. && .MARINE... WINDS XPCTD TO RMN BLO SCA VALUES TNGT AND SAT. WINDS ARE EXPECTED TO REMAIN BELOW SCA LEVELS INTO EARLY MONDAY BUT MAY APPROACH ADVISORY LEVELS LATER MONDAY AND TUESDAY WITH THE COLD FRONTAL PASSAGE. && .EQUIPMENT... THE PIKESVILLE NWR TRANSMITTER IS NOW BACK IN SVC. IT WILL GO DOWN AGN TUESDAY DECEMBER 12TH AND WEDNESDAY DECEMBER 13TH FOR AN ANTENNA REPLACEMENT. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && UPDATE...WOODY! PRVS...BAJ/KRW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 526 AM EST FRI DEC 7 2012 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 081000- 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- 526 AM EST FRI DEC 7 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...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED MONDAY FOR THE WATERS. .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>506-081000- 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- 526 AM EST FRI DEC 7 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...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY 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.
8 dense fog. Local standard time, as filed.
Visibility was reported to be around one quarter mile at Hagerstown Airport.
Visibility was reported to be around one quarter mile at Baltimore Washington Airport.
Visibility was reported to be around one quarter mile at Baltimore Washington and York Airport.
Visibility was reported to be around one quarter mile at Baltimore Washington and Lancaster Airport.
Visibility was reported to be around one quarter mile at Baltimore Washington, Frederick, and York Airports.
Visibility was reported to be around one quarter mile at Baltimore Washington Airport.
Visibility was reported to be around one quarter mile at Baltimore Washington Airport.
Visibility was reported to be around one quarter mile at Frederick Airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2012Every state in 2012This day in weather historyWarnings in Maryland, 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: 425718, 425726, 425722, 425723, 425721, 425724, 425725, 425719.