Parent low pressure moved up the Tennessee Valley towards the Mid Atlantic. As precipitation moved over the area, surface temperatures were below freezing and a wintery mix of sleet and freezing rain occurred.
Every event with a place to put it; 19 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.
Parent low pressure moved up the Tennessee Valley towards the Mid Atlantic. As precipitation moved over the area, surface temperatures were below freezing and a wintery mix of sleet and freezing rain occurred. Low pressure continued to intensify across the Mid Atlantic and onward to New England. Wrap around moisture produced heavy snow showers in the higher elevations.
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 26, 3:56 AM EST, 4 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
356 AM EST WED DEC 26 2012
.SYNOPSIS...
LOW PRESSURE OVER THE TENNESSEE VALLEY WILL MOVE TO THE NORTHEAST
TODAY...CROSSING THE APPALACHIANS THIS AFTERNOON AND THEN MOVING
OFF THE MID-ATLANTIC COAST TONIGHT. HIGH PRESSURE WILL RETURN FOR
LATE IN THE WEEK BEFORE ANOTHER STORM SYSTEM IMPACTS THE MID
ATLANTIC SATURDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
LOW PRESSURE LOCATED OVER NORTHERN MISSISSIPPI WILL MOVE TO THE
NORTHEAST INTO THE CENTRAL APPALACHIANS TODAY...BEFORE A SECONDARY
LOW DEVELOPS ALONG THE MID-ATLANTIC COAST THIS EVENING AND MOVES
OFFSHORE LATE TONIGHT.
AT 07Z...DECK OF CLOUDS WAS ALREADY OVERHEAD AND THE FIRST ADVANCES
OF PRECIPITATION WELL AHEAD OF LOW PRESSURE ON THE LEADING EDGE OF
ISENTROPIC LIFT WAS MAKING IT INTO THE CENTRAL SHENANDOAH VALLEY.
EXPECT PRECIPITATION TO MOVE TO THE NORTHEAST/EXPAND IN COVERAGE
THROUGH THE MORNING HOURS. ONCE PRECIPITATION BEGINS...IT WILL BE
AROUND THROUGH THE DAY BEFORE TAPERING OFF FROM SOUTHWEST TO
NORTHEAST IN THE DRY SLOT TONIGHT.
PRIMARY CHALLENGE WITH THIS STORM WILL BE P-TYPE...AS VIRTUALLY ALL
P-TYPES ARE EXPECTED WITH THIS EVENT...AND THEIR SUBSEQUENT AMOUNTS.
MUCH OF THE MIXED/WINTRY PRECIPITATION WILL OCCUR WEST OF THE
INTERSTATE 95 CORRIDOR WHERE WINTER HEADLINES ARE ALREADY IN EFFECT.
THE MOST PROLONGED AREA OF WINTRY PRECIPITATION IS EXPECTED ACROSS
THE SHENANDOAH VALLEY AND ALLEGHENY/POTOMAC HIGHLANDS. THE ONLY
CHANGE TO WINTER HEADLINES WILL BE TO UPGRADE THE WINTER WEATHER
ADVISORY FOR THE EASTERN SLOPES OF THE ALLEGHENY FRONT /EASTERN
ALLEGANY...MINERAL...GRANT...PENDLETON...HIGHLAND/. WARNING IS
ALREADY IN EFFECT FOR SNOW/ICE FOR THE WESTERN SLOPES. EASTERN
SLOPES ARE NOT LIKELY TO REACH SNOW CRITERIA HOWEVER MODELS SUGGEST
A PROLONGED PERIOD OF FREEZING RAIN /WITH COLD AIR TRAPPED NEAR
SURFACE/ WHICH WOULD REACH WARNING CRITERIA. FOR EXAMPLE...BUFKIT
POINT FORECAST FROM THE GFS AT CBE SUGGESTS GREATER THAN ONE QUARTER
INCH OF ICING LATER TODAY/THIS EVENING. THEREFORE...HAVE ENOUGH
CONFIDENCE TO UPGRADE A TIER EAST.
ACROSS THE SHENANDOAH VALLEY /HARDY...HAMPSHIRE...ROCKINGHAM...
AUGUSTA/...THERE WILL BE FREEZING RAIN AS WELL BUT HAVE LOWER
CONFIDENCE IN REACHING WARNING CRITERIA AND THEREFORE WILL CONTINUE
ADVISORY FOR 0.10 TO 0.20 INCH OF ICE ACCRETION AFTER THE INITIAL
PERIOD OF SNOW/SLEET.
ANOTHER ASPECT OF THIS STORM WILL BE THE POTENTIAL FOR ISOLATED
THUNDERSTORMS ACROSS LOWER SOUTHERN MARYLAND AND THE LOWER
CHESAPEAKE BAY REGION WHICH MAY PRODUCE LOCALLY STRONG GUSTY WINDS.
CONVECTIVE ELEMENTS MAY ALSO BRING LOCALLY HEAVY RAINFALL.
FOR TEMPERATURES...USED A BLEND OF MAV/MET TO DERIVE MAX/MIN T.
TEMPERATURES MAY ACTUALLY TO CONTINUE TO INCREASE INTO THE EVENING
PARTICULARLY EAST OF THE BLUE RIDGE BEFORE THE SYSTEM DEPARTS.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
THE PRECIP PORTION OF THE STORM SYSTEM WILL EXIT OFF THE MID ATLC
COAST EARLY THU MRNG...BUT THE SECOND HALF OF THE SYSTEM WILL BE THE
DRY WINDY DAY LEFT BEHIND. A WINDY AND COLD THURSDAY FOR THE AREA
WHICH WILL HELP TO DRY OUT THE REGION BUT DO LITTLE TO WARM IT UP.
NW WINDS OF 30 TO 40 MPH WILL BE COMMON FROM SUN UP TIL SUN
DOWN...DROPPING OFF DURING THE EVE HRS. WIND CHILLS DURING THE DAY
HOWEVER WILL FEEL LIKE THE 20S ACROSS THE REGION AND ONLY IN THE
TEENS OVER THE CNTRL APLCNS. SIMILAR TEMPS ON FRIDAY W/ HIGHS BARELY
REACHING 40 BY MID AFTN...THOUGH IT IS NEAR SEASONAL AVERAGE - BUT
MUCH LIGHTER WINDS WILL NOT DROP THE WIND CHILLS DOWN MUCH FURTHER
THAN THE AMBIENT TEMP.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AFTER A QUIET FRIDAY...ANOTHER QUICK-HITTING LOW PRESSURE SYSTEM
WILL SLIDE ACROSS THE REGION FOR A GOOD PORTION OF SATURDAY. LONG
TERM SOLUTIONS BEGINNING TO TREND TOWARD A SIMILAR SOLUTION ON THE
FEATURES THAT WILL DRIVE THIS SYSTEM. THE GFS IS TREATING THIS
SYSTEM LIKE THE MONDAY SHORTWAVE THAT BISECTED THE CWA IN TERMS OF
TYPES W/ MOSTLY SNOW ACROSS THE WRN HALF AND RAIN OVER THE ERN HALF
- THOUGH A RAIN-SNOW MIX ALSO AFFECTED THE PIEDMONT PERIODICALLY.
LIGHT-MODERATE QPF AND A FAIRLY PROGRESSIVE SYSTEM W/ A RELATIVELY
WEAK SFC LOW AND ONLY MILD DYNAMICS DRIVING THE SHORTWAVE. ONCE THE
WAVE MOVES OFF THE COAST...THEN THE GULF STREAM INTERACTION RAPIDLY
INTENSIFIES THE STORM BUT NOT UNTIL IT IS LARGELY OFF THE COAST AND
AWAY FROM THE AREA. THE 00Z EURO HAS COME MORE IN LINE W/ THE LATEST
GFS DETRM/ENS RUN...WHEREAS THE 12Z WAS MUCH STRONGER AND MORE
IMPACTING. THE LATEST EURO ALSO SHOWING A LIGHT BATCH OF PRECIP THAT
SLIDES QUICKLY OVER THE AREA ON SAT...AGAIN W/ AN I-95 RAIN
REGIME...SNOW ACROSS THE WRN HALF AND A MIX IN THE MIDDLE.
FURTHER INTO THE LONG RANGE...IT LOOKS LIKE A BREAK THAT'S LONGER
THAN JUST A DAY WILL BE IN STORE FOR EARLY NEXT WEEK. EXTENDED
GUIDANCE DOES SHOW ANOTHER POTENT STORM SYSTEM DEVELOPING OVER THE
DESERT SW/SRN PLAINS BUT TOO FAR INTO THE FUTURE TO RESOLVE HOW
THE LATITUDINAL WAVES WILL AFFECT AND STEER THE SYSTEM.
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
PRECIPITATION WILL MOVE IN FROM THE SOUTH THROUGH THE MORNING
HOURS. WINTRY MIX IS MOST LIKELY AT CHO/IAD/MRB ALTHOUGH DCA/BWI MAY
EXPERIENCE A BRIEF PERIOD OF SN/PL AS WELL AFTER DAYBREAK.
SHORTLY AFTER PRECIPITATION BEGINS...EXPECT A DEGRADATION TO MVFR
THEN IFR CONDITIONS WHICH WILL LIKELY LAST THROUGH THE
AFTERNOON/EVENING.
SKIES WILL BEGIN TO CLEAR OUT THU MRNG...BUT THIS WILL BE FROM
STRONG LOW LEVEL WINDS PUSHING THE SYSTEM OUT TO SEA. A PORTION OF
THESE INTENSE BOUNDARY LAYER WINDS WILL BE MIXED TO THE SFC IN THE
FORM OF 25-35KT GUSTS PERIODICALLY FROM MID MRNG THRU LATE EVE.
WINDS WILL SUBSIDE THU NIGHT AND A MUCH LESS OMINOUS REPEAT ON
FRI...W/ AFTN BREEZES IN THE 10-20KT RANGE. THIS BRIEF RESPITE WILL
LAST ONLY UNTIL EARLY SAT WHEN ANOTHER LOW PRESSURE SYSTEM MOVES
ACROSS THE DEEP SOUTH AND OFF THE CAROLINA COAST SAT NIGHT. A WINTRY
MIX MAY AFFECT THE AREA BETWEEN I-95 AND THE NRN VA BLUE RIDGE...W/
SNOW ACROSS THE SHEN VLY AND MAINLY RAIN OVER THE DC/BALT METRO
REGIONS.
&&
.MARINE...
EAST/SOUTHEAST FLOW WILL CONTINUE TO INCREASE AHEAD OF LOW PRESSURE
TODAY. HIGH END SCA WILL BE LIKELY. WILL HAVE TO WATCH SOUTHEAST
FLOW ALONG THE LOWER TIDAL POTOMAC/LOWER MD CHESAPEAKE BAY REGION AS
SOUTHEAST WINDS CAN SOMETIMES BE STRONGER THAN FORECAST...IN THIS
CASE GETTING CLOSE TO GALES. LOW PRESSURE MOVES OVER THE WATERS
TONIGHT...WITH WINDS SHIFTING TOWARD DAWN.
IMMEDIATELY BEHIND THE OVERNIGHT RAINS FROM A STRONG SFC LOW PASSAGE
EARLY THU WILL BE A STRONG PRESENCE OF GUSTY WINDS DURING THE
DAYTIME HRS. PRECIP MAY END BUT THE WINDS WILL BE JUST BEGINNING TO
GUST OUT OF THE NW. LOW-END GALE GUSTS WILL BE PRESENT FOR MUCH OF
THE DAY...SO A GALE WRNG HAS BEEN ISSUED FOR THU OVER ALL THE
WATERS. A LESS WINDY DAY ON FRI...THOUGH STILL A FEW NEAR 15-20KT
BREEZES FOR A PORTION OF THE WATERS. ANOTHER LESS INTENSE LOW
PRESSURE SYSTEM WILL MOVE OVER THE AREA ON SAT.
&&
.TIDES/COASTAL FLOODING...
WATER LEVELS WERE ONLY A QUARTER TO HALF FOOT ABOVE NORMAL EARLY
THIS MORNING...BUT AS EAST AND THEN SOUTHEAST WINDS INCREASE EXPECT
ANOMALIES TO QUICKLY INCREASE. HIGH TIDE THIS MORNING WILL BE BELOW
MINOR TIDAL FLOODING LEVELS...BUT ITS POSSIBLE THAT THE LATE
AFTERNOON/EVENING HIGH TIDE MAY GET CLOSE TO MINOR TIDAL FLOODING
THRESHOLDS. THUS...A COASTAL FLOOD ADVISORY MAY BECOME NECESSARY.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR MDZ501-502.
WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR MDZ003>005.
VA...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR VAZ503-504.
WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR VAZ025>031-
036>040-042-501.
WV...WINTER STORM WARNING UNTIL 6 AM EST THURSDAY FOR WVZ501>506.
WINTER WEATHER ADVISORY UNTIL 6 AM EST THURSDAY FOR WVZ050>053-
055.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ530>532-
535-536-538>540.
GALE WARNING FROM 6 AM TO 6 PM EST THURSDAY FOR ANZ530>543.
SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ533-534-
537-541>543.
&&
SYNOPSIS...BPP/GMS
NEAR TERM...BPP
SHORT TERM...GMS
LONG TERM...GMS
AVIATION...BPP/GMS
MARINE...BPP/GMS
TIDES/COASTAL FLOODING...BPPHAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1005 PM EST TUE DEC 25 2012 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 261315- 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- 1005 PM EST TUE DEC 25 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 SMALL CRAFT ADVISORY IS IN EFFECT FOR THE THE LOWER PORTIONS OF THE MARYLAND CHESAPEAKE BAY AND TIDAL POTOMAC RIVER INLET OVERNIGHT. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY AND TIDAL POTOMAC RIVER ON WEDNESDAY AND WEDNESDAY NIGHT. A GALE WARNING MAY BE NEEDED FOR THE WATERS ON THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED THURSDAY NIGHT AND FRIDAY. COASTAL FLOODING IS POSSIBLE WEDNESDAY AFTERNOON AND NIGHT. A STORM SYSTEM WILL LIKELY IMPACT PORTIONS OF THE MID- ATLANTIC REGION THIS WEEKEND. AT THIS STAGE...RAIN OR SNOW IS POSSIBLE DEPENDING ON THE STORM TRACK. .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>506-261315- 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- 1005 PM EST TUE DEC 25 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 WINTRY MIX OF SNOW...SLEET AND FREEZING RAIN WILL OVERSPREAD THE AREA FROM THE SOUTH LATE TONIGHT. A WINTER STORM WARNING HAS BEEN ISSUED FOR THE WESTERN SLOPES OF THE ALLEGHENY MOUNTAINS. A WINTER WEATHER ADVISORY HAS BEEN ISSUED ALONG AND WEST OF THE BLUE RIDGE MOUNTAINS...INCLUDING THE EASTERN WEST VIRGINIA PANHANDLE AND THE SHENANDOAH VALLEY. SEE /WBCWSWLWX/ FOR DETAILS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY THE WINTER STORM WARNING AND WINTER WEATHER ADVISORY CONTINUES THROUGH WEDNESDAY NIGHT. THE NEXT STORM SYSTEM WILL LIKELY IMPACT PORTIONS OF THE MID- ATLANTIC REGION THIS WEEKEND. AT THIS EARLY STAGE...RAIN OR SNOW IS POSSIBLE DEPENDING ON THE STORM TRACK. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE REQUESTED TO REPORT SNOWFALL...SLEET AND ICE ACCUMULATIONS TO THE NATIONAL WEATHER SERVICE.
The national radar mosaic for the moment the first event began.
20 winter weather, 1 winter storm. Local standard time, as filed.
Snowfall accumulations averaged 2 to 3 inches in the county.
Snowfall accumulations averaged 2 to 4 inches in the county.
Estimated ice averaged a trace in the county.
Estimated ice averaged a trace and snowfall accumulations averaged 1 inch in the county.
Snowfall accumulations averaged 4 inches in the county.
Snowfall accumulations averaged 4 inches in the county.
Snowfall accumulations averaged 3 and 4 inches in the county.
Snowfall accumulations averaged 2 inches and were estimated by surrounding spotters.
Snowfall accumulations averaged between 4 and 8 inches across the zone.
Snowfall accumulations averaged 3 to 5 inches in the county.
Snowfall accumulations averaged 2 inches in the county.
Estimated ice averaged a trace and snowfall accumulations averaged 1 inch in the county.
Snowfall accumulations averaged 1 inch in the county during rush hour.
Snowfall accumulations averaged 1 inch in the county during rush hour.
Snowfall accumulations averaged 2 to 3 inches in the county.
Snowfall accumulations averaged 3 inches in the county.
Snowfall accumulations averaged 2 inches in the county.
Estimated ice was a trace and snowfall accumulations averaged 1 inches in the county.
Snowfall accumulations averaged 3 inches in the county.
Snowfall accumulations averaged 2 and 3 inches in the county.
Snowfall accumulations averaged 1 inch at rush hour in the county.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Virginia in 2012Every state in 2012This day in weather historyWarnings in 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: 425255, 425256, 425257, 425258, 425264, 425265, 425271, 425654, 425050, 425259, 425260, 425261, 425262, 425263, 425266, 425267, 425268, 425269, 425270, 425272, 425664.