National Weather Service Raw Text Product

621 
FXUS61 KLWX 130309
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1009 PM EST WED FEB 12 2014

.SYNOPSIS...
LOW PRESSURE OFF THE SOUTHEAST COAST WILL WILL INTENSIFY TONIGHT
THROUGH THURSDAY NIGHT AS IT TRACKS UP THE MID-ATLANTIC COAST.
HIGH PRESSURE WILL BRIEFLY RETURN FRIDAY...BEFORE A COLD FRONT
PASSES THROUGH FRIDAY NIGHT. HIGH PRESSURE WILL BUILD OVERHEAD
SATURDAY FOLLOWED BY ANOTHER LOW PRESSURE TROUGH MOVING THROUGH
SATURDAY NIGHT INTO SUNDAY.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
NO CHANGES TO WINTER HEADLINES THIS EVENING...AND SNOWFALL
FORECAST REMAINS ON TRACK.

LOW PRESSURE WAS LOCATED OFF THE SOUTHEAST COAST...WITH THE
GREATEST PRESSURE FALLS OFF THE CAROLINA COAST. LOW PRESSURE WILL
TRACK NORTHWARD UP THE COAST THROUGH THURSDAY NIGHT.

INITIAL SNOWFALL HAS ALREADY PUSHED NORTHWARD TO THE MASON DIXON
LINE EARLY THIS EVENING. WARM ADVECTION/ISENTROPIC LIFT WILL
CONTINUE TO SUPPORT LIGHT TO MODERATE SNOW THROUGH THE REST OF THE
EVENING. MODERATE SNOW OVER THE SOUTHERN CWA AT 02Z LIKELY SPREADS
NORTH INTO DC-BALT BY 04Z. 

AFTER 06Z...WILL START TO SEE STRONGER FORCING AND BANDING
POTENTIAL ALONG WITH HEAVY SNOWFALL AT TIMES WHERE SNOWFALL RATES
OF 1 TO 2 INCHES PER HOUR MAY OCCUR. SNOW WILL ALSO START TO MIX
WITH OR CHANGE OVER TO SLEET/RAIN ACROSS ST MARYS/CALVERT
COUNTIES WHICH WILL CUT DOWN ON SNOWFALL ACCUMULATIONS BUT COULD
ALSO LEAD TO A BRIEF PERIOD OF ICING BEFORE SURFACE TEMPERATURES
RISE ABOVE FREEZING. 

SNOW CONTINUES HEAVY AT TIMES THURSDAY MORNING /FOR SIGNIFICANT
IMPACT DURING THE MORNING RUSH/...BUT THE RAIN/SNOW LINE IS
EXPECTED TO TILT FURTHER NORTHWESTWARD DURING THE DAYTIME AT LEAST
TO THE INTERSTATE 95 CORRIDOR PERHAPS EVEN FURTHER WEST. THOSE
AREAS THAT RECEIVE ALL SNOW WILL SEE THE HIGHEST ACCUMULATIONS AND THE
STRIP OF MOST SIGNIFICANT SNOW AMOUNTS APPEARS TO BE FROM THE
CENTRAL SHENANDOAH VALLEY/FOOTHILLS NORTHWARD ALONG THE BLUE
RIDGE.

THE LOW IS EXPECTED TO SLOW DOWN AS IT RAPIDLY DEEPENS ON THU
AFTN. THE 12Z ECMWF/NAM SHOWS A WELL-DEFINED TROWAL
DEVELOPING...RESULTING IN A MODERATE TO POTENTIALLY HEAVY SNOW
BAND AROUND THE BACKSIDE OF THE LOW. ACCUMULATING SNOW COULD
LINGER INTO THU EVE ACROSS THE SWRN HALF OF THE CWA AND LATE THU
NGT ACROSS THE NERN HALF. 

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
UPPER LEVEL RIDGING WILL ENTER THE MID ATLANTIC FRIDAY RESULTING IN 
DRY CONDITIONS. SNOWPACK ON THE GROUND WILL KEEP TEMPS FROM RISING 
TO THEIR FULL POTENTIAL BUT ARE EXPECTED TO REACH THE LOW 40S. SOME 
MELTING OF SNOW WILL OCCUR AND CAUSE REFREEZE ISSUES FRIDAY NIGHT AS 
TEMPS WILL DROP TO THE UPPER 20S. A CLIPPER SYSTEM WILL APPROACH 
FROM THE WEST RESULTING IN INCREASED CLOUD COVER FRIDAY AFTERNOON. 
SNOW SHOWERS ARE EXPECTED ALONG THE ALLEGHENY FRONT FRIDAY NIGHT. A 
FEW INCHES OF ACCUMULATION IS POSSIBLE IN THIS AREA. AS THE CLIPPER 
MOVES EASTWARD A TROUGH OF LOW PRESSURE WILL FORM ON THE LEE SIDE OF 
THE APPALACHIANS ACROSS THE MID ATLANTIC. SNOW SHOWERS WILL BE 
POSSIBLE EAST OF THE MTNS EARLY SATURDAY MORNING. THE TROUGH AXIS 
ALOFT WILL QUICKLY MOVE THROUGH TOWARDS SUNRISE SATURDAY AND 
SUBSIDENCE BEHIND IT WILL RESULT IN LITTLE TO NO ACCUMULATION WITH 
THE EXCEPTION OF THE ALLEGHENY FRONT.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A SERIES OF UPPER LEVEL STORM SYSTEMS WILL MOVE ACROSS THE REGION 
THROUGH THE FOUR DAY PERIOD. ONE SYSTEM SATURDAY MORNING...ANOTHER 
SUNDAY MORNING AND THE THIRD WILL BE MONDAY NIGHT. WHILE THERE COULD 
BE A FEW SNOW SHOWERS ACCOMPANYING THE SYSTEM SATURDAY MORNING...THE 
SECOND SYSTEM MAY END UP GETTING WASHED OUT IN THE UPPER LEVEL 
FLOW...WHILE THE THIRD SYSTEM MONDAY NIGHT SHOULD BRING A CHANCE FOR 
RAIN AND SNOW SHOWERS.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
INITIAL SNOW HAS SPREAD NORTHWARD TO THE TERMINALS. EXPECT SNOW TO
BECOME MODERATE 03Z-06Z...AND THEN PERIODIC HEAVY SNOW WITH VIS
DOWN NEAR 1/4SM APPEARS LIKELY LATE TONIGHT/EARLY THURSDAY
MORNING. RAIN/SNOW LINE TILTS NORTHWEST DURING THE DAY
THURSDAY...SO DCA/BWI MAY HAVE SOME IP/RA FOR A TIME BUT AS COLDER
AIR WORKS BACK IN ON THE TAIL END OF THE STORM A CHANGE BACK TO SN
MAY OCCUR THURSDAY EVENING. NORTHWEST WINDS ALSO INCREASE THURSDAY
WITH LOW PRESSURE DEEPENING OFFSHORE...GUSTS 25 TO 30 KT. 

LOW PRESSURE WILL MOVE AWAY FROM THE REGION THURSDAY NIGHT AND CIGS 
WILL IMPROVE FROM SW TO NE DURING THIS TIME. IFR CONDITIONS SHOULD  
PERSIST AT BWI-MTN THROUGH EARLY FRIDAY MORNING. GUSTY NW WINDS WILL 
SUBSIDE BY FRIDAY MORNING AND CLEARING IS EXPECTED TO OCCUR. A 
CLIPPER SYSTEM WILL MOVE ACROSS THE REGION FRIDAY NIGHT. CIGS WILL 
LOWER INTO SAT MORNING. SCT SN SHOWERS WILL BE POSSIBLE RESULTING IN 
LOW VSBYS.

MVFR CONDITIONS MAY EVOLVE WITH ANY SNOW SHOWERS SATURDAY MORNING 
AND AGAIN SUNDAY MORNING...OTHERWISE...VFR CONDITIONS THROUGH 
MONDAY. MVFR OR PERHAPS IFR CONDITIONS COULD DEVELOP WITH SNOW OR 
RAIN SHOWERS MONDAY NIGHT. VFR CONDITIONS ON TUESDAY.

&&

.MARINE...
SNOW HAS OVERSPREAD THE AREA...WITH VSBY RESTRICTIONS OF 1 NM OR
LESS AT TIMES TONIGHT. SNOW MIXES WITH OR CHANGES TO SLEET/RAIN
OVERNIGHT INTO THURSDAY MORNING. 

NORTHERLY FLOW IS FORECAST TO INTENSIFY TONIGHT AS THE GRADIENT
INCREASES WITH DEEPENING LOW PRESSURE OFF THE SOUTHEAST COAST.
THIS LOW WILL TRACK NORTH THURSDAY/THURSDAY NIGHT. SCA RAMPS UP TO
GALES ON THE CHESAPEAKE BAY SOUTH OF SANDY POINT AND LOWER TIDAL
POTOMAC. THIS CONTINUES INTO THURSDAY. 

A TIGHT GRADIENT WILL PERSIST THURSDAY NIGHT AND NW WINDS WITH
GUSTS UP TO 30KTS WILL BE POSSIBLE. A ADVISORY MAY NEED TO BE
ISSUED FOR THIS TIME. FLOW WILL BECOME W-SW 5-10MPH FRIDAY. A
CLIPPER WILL MOVE ACROSS THE AREA SATURDAY MORNING. GUSTY NW WINDS
WILL BE POSSIBLE SATURDAY AFTERNOON. SMALL CRAFT ADVISORIES MAY
BE NEEDED SATURDAY AND AGAIN MONDAY NIGHT.

&&

.TIDES/COASTAL FLOODING...
A NORTH-NORTHEAST FLOW WILL CAUSE ELEVATED WATER LEVELS LATE
TONIGHT AND THURSDAY AS A COASTAL LOW PASSES BY TO THE EAST.
AT THIS TIME...IT APPEARS THAT LEVELS WILL BE JUST UNDER MINOR
TIDAL THRESHOLDS BUT WILL NEED TO BE WATCHED AS THE GRADIENT
INTENSIFIES TONIGHT IN STEP WITH DEEPENING LOW PRESSURE. 

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER STORM WARNING UNTIL 3 PM EST THURSDAY FOR DCZ001.
MD...WINTER STORM WARNING UNTIL 9 PM EST THURSDAY FOR MDZ501-502.
     WINTER STORM WARNING UNTIL 3 PM EST THURSDAY FOR MDZ013-014-
     016.
     WINTER STORM WARNING UNTIL 5 AM EST FRIDAY FOR MDZ003>007-
     009>011.
     WINTER WEATHER ADVISORY UNTIL NOON EST THURSDAY FOR MDZ017-018.
VA...WINTER STORM WARNING UNTIL 9 PM EST THURSDAY FOR VAZ025>027-
     029-036>040-050-051-056-503-504.
     WINTER STORM WARNING UNTIL 3 PM EST THURSDAY FOR VAZ054-057.
     WINTER STORM WARNING UNTIL 5 AM EST FRIDAY FOR VAZ028-030-031-
     042-052-053-055-501-502.
WV...WINTER STORM WARNING UNTIL 9 PM EST THURSDAY FOR WVZ050-055-
     501>506.
     WINTER STORM WARNING UNTIL 5 AM EST FRIDAY FOR WVZ051>053.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EST THURSDAY FOR ANZ532-540-
     541.
     GALE WARNING FROM 2 AM TO 6 PM EST THURSDAY FOR ANZ532>534-537-
     540>543.
     SMALL CRAFT ADVISORY UNTIL 2 AM EST THURSDAY FOR ANZ533-534-
     537-542-543.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST THURSDAY FOR ANZ530-531-
     535-538-539.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST THURSDAY FOR ANZ536.

&&

$$
SYNOPSIS...BPP/JRK
NEAR TERM...BPP/JRK
SHORT TERM...HAS
LONG TERM...KLW
AVIATION...BPP/JRK/HAS/KLW
MARINE...BPP/JRK/HAS/KLW
TIDES/COASTAL FLOODING...BPP