Blizzard Warning 1, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
325 PM EST FRI DEC 18 2009

.SYNOPSIS...
LOW PRESSURE OVER THE SOUTHEASTERN STATES WILL INTENSIFY ALONG THE
CAROLINA COAST THIS EVENING. THE STORM WILL INTENSIFY AND MOVE
ALONG THE EAST COAST SATURDAY INTO SUNDAY MORNING. A WEAK
DISTURBANCE WILL CROSS THE MID-ATLANTIC REGION LATE MONDAY BEFORE
HIGH PRESSURE BUILDS IN FOR THE MIDDLE PART OF THE WEEK. A STRONG
UPPER DISTURBANCE IS EXPECTED TO IMPACT THE MID-ATLANTIC FOR
CHRISTMAS.

&&

.NEAR TERM /THROUGH TONIGHT/...
ACCUMULATING SNOWFALL BEGINS THIS AFTERNOON. REGIONAL RADAR MOSAIC
DEPICTS THE LEADING BANDS OF SNOW CURRENTLY STRETCHED FROM SOUTHERN
WV TO CAPE HATTERAS...INCLUDING HIGHLAND...AUGUSTA AND NELSON
COUNTIES. A FEW FLAKES MAY REACH DC AND BALTIMORE THIS EVENING...BUT
ACCUMULATING SNOW WILL BE A FEW HOURS LATER GIVEN SURFACE AND AIR
TEMPERATURES IN THE LOW 30S. GENERAL OVERNIGHT ACCUMULATIONS OF
2-4 INCHES WILL BE POSSIBLE IN THE METRO AREAS...5-10 INCHES IN
THE CENTRAL SHENANDOAH VALLEY AND CENTRAL FOOTHILLS.

&&

.SHORT TERM /SATURDAY/...
INTENSE SNOWFALL BEGINS THIS EVENING FOR SW ZONES THEN SPREADS
NORTHEAST THROUGH THE NIGHT AS THE CENTER OF THE LOW REACHES THE
GA COAST AND INTENSIFIES AS IT HEADS NE UP THE CAROLINA COAST
TONIGHT. EXPECTING THE STORM TO BE HALF OVER FOR THE SW ZONES BY
TOMORROW MORNING...WHILE JUST GETTING UNDERWAY FOR THE BALTIMORE-
DC METRO AREA. AS THE SYSTEM CROSSES CAPE HATTERAS EARLY SATURDAY...
WRAPAROUND SNOW BANDS SPREAD ACROSS THE CWA...PRIMARILY ALONG AND
EAST OF THE SHENANDOAH VALLEY. A TROWAL WITH EMBEDDED INSTABILITY
EXPECTED TO BE ALONG THE I-95 CORRIDOR THROUGH THE DAY SATURDAY...
PRODUCING INTENSE SNOWFALL. THE TROWAL AXIS PULLS EAST SATURDAY
NIGHT...THOUGH THE RATE AT WHICH IT MOVES EAST REMAINS TO BE SEEN.
HOWEVER...EXPECT SNOWFALL TO TAPER OFF FROM WEST TO EAST SATURDAY
NIGHT...ENDING ALONG THE WESTERN SHORE OF THE BAY SUNDAY MORNING.

WINDS OF 15 TO 20 MPH WITH GUSTS TO 25 MPH WILL BLOW THE HEAVY SNOW
AS IT FALLS...FURTHER DECREASING VISIBILITY. TRAVEL WILL BE VERY
TREACHEROUS AND IS GREATLY DISCOURAGED LATE TONIGHT THROUGH
SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
SNOW XPCD TO TAPER OFF SUN AS LOPRES MOVES QUICKLY AWAY FROM RGN.
WNWLY LOW-LVL FLOW AND APRCH OF A LOW-AMPLITUDE SHRTWV TROF WILL
PROMOTE UPSLP SNOW SHOWERS ALONG WRN SLOPES OF ALLEGHENY FRONT
THRU MON NGT.

COLD AIR RMNS PRESENT THRU MUCH OF NEXT WEEK OWING TO PERSISTENT
SNOW PACK. A STRONG CLOSED UPR LOW XPCD TO FORM OVER SRN PLNS MID
WEEK AND COULD RESULT IN PCPN THU-FRI. ATTM...MODELS SUGGEST A
TRANSITION FROM SNOW INITIALLY TO RAIN AS WARM AIR IS DRAWN INTO
THE SYSTEM.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
VFR CONDITIONS END THIS EVENING AS SNOW SPREADS NORTHEASTWARD. SNOW
INTENSIFIES FROM SW TO NE TONIGHT WITH HEAVY SNOW ALL DAY SATURDAY
BEFORE TAPERING OFF FROM SW TO NE SATURDAY NIGHT. NLY WINDS 15 KT
WITH GUSTS UP TO 25 KT DURING SNOWFALL SATURDAY.

MAIN PSBLTY FOR TERMINAL IMPACTS IN EXTENDED PDS IS THU-FRI NEXT
WEEK...WHEN A DEEP CLOSED UPR LOW WILL APRCH APLCNS AND COULD
GENERATE RAIN/SNOW OVER MUCH OF MID-ATLC RGN.

&&

.MARINE...
EASTERLY FLOW INCREASES THIS AFTERNOON WITH SCA STARTING SOUTH THIS
EVENING AND EXPANDING TO ALL WATERS BY MIDNIGHT. INTENSIFICATION
CONTINUES THROUGH THE NIGHT WITH GALES EXPECTED ACROSS THE WATERS
EXCEPT THE TIDAL POTOMAC ABOVE COBB ISLAND...THE PATAPSCO...AND
NORTH OF POOLES ISLAND. GALE FORCE GUSTS AND HEAVY SNOW ARE
EXPECTED SATURDAY AND SATURDAY NIGHT BEFORE THE STORM PULLS AWAY
FROM THE BAY SUNDAY MORNING.

&&

.TIDES/COASTAL FLOODING...
LOW PRESSURE WILL INTENSIFY OFF THE CAROLINA COAST TONIGHT...MOVING
NEAR THE MOUTH OF THE BAY LATE TONIGHT AND SATURDAY. PROLONGED
NORTHEASTERLY FLOW WILL BUILD EXCESS WATER INTO THE BAY...BRINGING
POSITIVE TIDAL DEPARTURES OF AROUND ONE FOOT TONIGHT AND SATURDAY.
NO COASTAL FLOODING IS EXPECTED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM EST SUNDAY
     FOR DCZ001.
MD...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM EST SUNDAY
     FOR MDZ003>007-009>011-013-014-018.
     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 AM EST SUNDAY
     FOR MDZ016-017-501-502.
VA...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM EST SUNDAY
     FOR VAZ042-053-054.
     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM EST SUNDAY
     FOR VAZ021-025-026-036>039-050-056.
     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 AM EST SUNDAY
     FOR VAZ027>031-040-041-051-052-055-057.
WV...WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM EST SUNDAY
     FOR WVZ051>053.
     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM EST SUNDAY
     FOR WVZ054.
     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 AM EST SUNDAY
     FOR WVZ050-055-501>504.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EST
     SATURDAY FOR ANZ531-532-539-540.
     GALE WARNING FROM 6 AM TO 10 PM EST SATURDAY FOR ANZ531>534-
     537-539>543.
     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
     SATURDAY FOR ANZ533-534-537-541>543.
     SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 10 PM EST
     SATURDAY FOR ANZ530-535-536-538.

&&

BAJ/KRAMAR

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
312 PM EST FRI DEC 18 2009

ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057-
191000-
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-
312 PM EST FRI DEC 18 2009

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...THIS AFTERNOON AND TONIGHT

LOW PRESSURE ACROSS THE SOUTHEASTERN UNITED STATES WILL EMERGE
INTO THE ATLANTIC OFF THE CAROLINA COAST TONIGHT. ACCUMULATING SNOW
WILL SPREAD ACROSS THE AREA TONIGHT WITH HEAVY SNOW EXPECTED. A
WINTER STORM WARNING IS IN EFFECT BEGINNING TONIGHT. PLEASE SEE
THE LATEST WINTER WEATHER MESSAGE /WSWLWX/ FOR DETAILS.

PROLONGED NORTHEASTERLY ONSHORE FLOW WILL POSE A THREAT FOR MINOR
COASTAL FLOODING TONIGHT.

A SMALL CRAFT ADVISORY IS IN EFFECT THIS EVENING FOR THE LOWER TIDAL
POTOMAC RIVER AND THE MARYLAND CHESAPEAKE BAY FROM NORTH BEACH TO
SMITH POINT. A SMALL CRAFT ADVISORY IS IN EFFECT LATE TONIGHT FOR
ALL OF THE MARYLAND CHESAPEAKE BAY AND TIDAL POTOMAC RIVER.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WINTER STORM WARNING CONTINUES THROUGH SATURDAY NIGHT.

PROLONGED NORTHEASTERLY ONSHORE FLOW WILL POSE A THREAT FOR MINOR
COASTAL FLOODING SATURDAY.

A GALE WARNING IS IN EFFECT FOR THE LOWER TIDAL POTOMAC AND
MARYLAND CHESAPEAKE BAY BELOW POOLES ISLAND SATURDAY AND SATURDAY
EVENING. A SMALL CRAFT ADVISORY IS IN EFFECT NORTH OF POOLES
ISLAND AND FOR THE REMAINDER OF THE TIDAL POTOMAC RIVER.

SMALL CRAFT ADVISORIES WILL LIKELY BE REQUIRED BEYOND SATURDAY
EVENING.

.SPOTTER INFORMATION STATEMENT...

ON-STATION SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.
HOWEVER...SKYWARN WILL BE OPERATING REMOTELY. PLEASE RELAY ANY
SNOW ACCUMULATION REPORTS TO THE NATIONAL WEATHER SERVICE.

MDZ003>005-009-010-501-502-VAZ021-025>031-036>042-050-051-
WVZ050>055-501>504-191000-
WASHINGTON-FREDERICK MD-CARROLL-MONTGOMERY-HOWARD-
EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-HIGHLAND-
AUGUSTA-ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-
NELSON-ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-FAUQUIER-LOUDOUN-
ORANGE-CULPEPER-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-PENDLETON-
HARDY-WESTERN GRANT-EASTERN GRANT-WESTERN MINERAL-EASTERN MINERAL-
312 PM EST FRI DEC 18 2009

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...THIS AFTERNOON AND TONIGHT

LOW PRESSURE ACROSS THE SOUTHEASTERN UNITED STATES WILL EMERGE
INTO THE ATLANTIC OFF THE CAROLINA COAST TONIGHT. ACCUMULATING SNOW
WILL SPREAD ACROSS THE AREA TONIGHT WITH HEAVY SNOW EXPECTED. A
WINTER STORM WARNING IS IN EFFECT BEGINNING TONIGHT. PLEASE SEE
THE LATEST WINTER WEATHER MESSAGE /WSWLWX/ FOR DETAILS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WINTER STORM WARNING CONTINUES THROUGH SATURDAY NIGHT.

IN THE WAKE OF THIS WINTER STORM...UPSLOPE SNOW SHOWERS WILL BE
POSSIBLE ALONG WEST-FACING SLOPES IN THE POTOMAC HIGHLANDS SUNDAY
AND MONDAY. ADDITIONAL SNOW ACCUMULATIONS CAN BE EXPECTED.

.SPOTTER INFORMATION STATEMENT...

ON-STATION SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.
HOWEVER...SKYWARN WILL BE OPERATING REMOTELY. PLEASE RELAY ANY
SNOW ACCUMULATION REPORTS TO THE NATIONAL WEATHER SERVICE.

KRAMAR