Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 252042
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
342 PM EST SUN JAN 25 2015

.SYNOPSIS...
HIGH PRESSURE BUILDS INTO THE MID ATLANTIC STATES BRIEFLY TODAY.
LOW PRESSURE OVER IOWA WILL TRACK ACROSS SOUTHERN VIRGINIA
TONIGHT...STRENGTHENING AS IT MOVES UP THE COAST MONDAY AND TUESDAY.
HIGH PRESSURE IS THEN EXPECTED THROUGH MIDWEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
FIRST OFF...WATCHES/WARNINGS/ADVISORIES. THE WINTER STORM WARNING
REMAINS IN EFFECT FOR PORTIONS OF NORTH CENTRAL MD AND THE POTOMAC
HIGHLANDS. THE WINTER WEATHER ADVISORY REMAINS IN EFFECT FOR
BALTIMORE/DC METROS...NORTHERN VA...THE PIEDMONT AND SOUTHWEST TO
THE VA HIGHLANDS. BOTH ARE IN EFFECT TONIGHT THRU MONDAY. THE WINTER
STORM WATCH REMAINS IN EFFECT FOR THE COASTAL MD COUNTIES
IMMEDIATELY ON THE CHESAPEAKE FOR MONDAY NIGHT-TUESDAY.

LOW PRESSURE CURRENTLY OVER THE MIDWEST WILL SWING EAST AND DIP
SOUTHWARD TONIGHT...BRINGING WIDESPREAD PCPN TO THE REGION. 20Z
WATER VAPOR IMAGERY INDICATING THE LOW CENTERED OVER WESTERN KY. THE
12Z MODEL SUITE IS IN GOOD AGREEMENT WITH THE LOW THROUGH
TONIGHT...BRINGING THE CENTER JUST TO THE SOUTH OF THE AREA AND
PUSHING OFF THE CAROLINA COAST MONDAY. THIS PATH IS DICTATED WITH
UPPER LVL TROUGH DIPPING AS FAR SOUTH AS INTO THE GOM.

CONCERNING THE SENSIBLE WEATHER...PCPN PUSHES EAST INTO THE
AREA...FOLLOWING THE MASON DIXON LINE AS A SHORTWAVE LIFTS NORTH.
TIMED THE PCPN FOLLOWING A BLEND OF THE HIRES ARW/NMM...WHICH KEEPS
THE PCPN THIS EVENING MAINLY NORTH OF THE DC/BALTIMORE METROS. AS
THE LOW NEARS OVERNIGHT AND THE TROUGH BEGINS TO ROTATE HEADING TO
THE NEGATIVE TILT...THE PCPN OVERSPREADS THE AREA...COMING FROM A
SOUTH AND WEST POSITION. TEMPS INITIALLY IN THE UPPER 30S/LOWER 40S
THIS EVENING WOULD SUGGEST ALL RAIN...WITH SOME SNOWFLAKES MIXING
IN. AS THE BETTER DYNAMICALLY FORCING MOVES THROUGH...WILL SEE THE
PCPN CHANGING TO ALL SNOW FROM A N TO S PATH. 12Z NAM AND SREF
BUFKIT SOUNDINGS ARE THE COLDER SOLUTIONS...BUT REALLY LAG THE
CHANGE OVER. THE 12Z GFS...A MUCH WARMER SOLUTION...HOLDS ONTO THE
RAIN FOR MANY PORTIONS OF THE AREA WELL INTO MONDAY BEFORE THE CAA
REALLY TAKES HOLD. WAS INITIALLY IMPRESSED WITH 850MB TEMPS A COUPLE
DAYS AGO DROPPING TO -7 DEGREES CELSIUS...BUT NOW GFS/ECMWF AND NAM
ALL KEEP AROUND -2 DEGREES CELSIUS THRU MONDAY. THE THINKING IS IT
WILL TAKE THE HEAVIER QPF AMTS TO RESULT IN AN ALL SNOW SOLUTION AND
AS SUCH HAVE TIME THE CHANGE OVER TO CORRESPOND AS THE HEAVIER PCPN
MOVES IN. QPF AMTS WERE TRICKY...WITH GFS ON THE HIGHER END AND THEN
THE ECMWF AND NAM ON THE LOWER SIDE. TOOK A BLEND OF THE GFS/ECMWF
TO ACCOUNT FOR THE SPREAD. WHEN CALCULATING SNOW TOTALS...KEPT WITH
A 10:1 RATIO FOR TONIGHT. WOULD LIKE TO STRESS THAT THE TIMING OF
THE CHANGEOVER WILL BE CRUCIAL TO THE SNOW TOTALS FOR TONIGHT...WITH
SOME AREAS MAYBE GETTING NOTHING...AND SOME SEEING AN ADDITIONAL 1-2
INCHES.

THE LOW PUSHES OFFSHORE WITH THE UPPER LVL TROUGH BCMG NEGATIVELY
TILTED DURING THE DAY. AS THE LOW MOVES EAST...AN EASTERLY FLOW SET
UP WILL KEEP PLENTY OF MOISTURE BEING INJECTED IN OVER THE AREA
THROUGHOUT THE DAY. ON GOING PCPN DURING THE PERIOD AS THE UPPER LVL
ENERGY SHIFTS FROM THE WESTERN PORTIONS OF THE CWA AND ALIGNS ALONG
A LINE PARALLEL TO THE CHESAPEAKE BAY. HAVE TIMED OUT THE HEAVIEST
PCPN CORRESPONDING TO THE BETTER FRONTOGENETIC FORCING...WHICH HAS THE
LINE OF HEAVIEST PCPN LINING THE BLUE RIDGE IN THE MORNING. 12Z NAM
AND GFS HAVE CAPTURED THIS WITH THE ECMWF HINTING AT IT. CONTINUED
TO USE A BLEND OF THE GFS AND ECMWF FOR QPF TOTALS THROUGHOUT THE
DAY MONDAY. AS FOR PCPN TYPES...EXPECTING TO SEE ACTUALLY A LITTLE
WARMING IN THE MORNING...THEN SHOULD SEE DECREASING TEMPS HEADING
INTO THE AFTN AS THE COLDER AIR IS USHERED ON THE BACKSIDE OF THE
DEEPENING LOW...NOW OFFSHORE. THINKING THE TYPICALLY COLDER AREAS OF
BALTIMORE METRO EXTENDING TO THE SOUTH AND WEST OF DC METRO WILL
STAY COLDER DURING THE TIME AS A NORTHEAST FLOW SETS UP. SO WILL
KEEP THEM ALL SNOW...WITH RAIN/SNOW MIX TO THE SOUTH...OR POSSIBLY
EVEN A PERIOD OF ALL RAIN IN THE MORNING. AS THE TEMPS COOL IN THE
AFTN...EXPECTING EVERYWHERE BUT SOUTHERN MD TO BECOME SNOW.
AGAIN...SHOULD BE NOTED...ANY DIFFERENCE IN P-TYPE WILL CHANGE THE
SNOW TOTALS...ESP CONSIDERING THAT AS THE DAY PROGRESSES AND WE GET
COLDER AIR...SHOULD EXPECT TO SEE INCREASING SNOW RATIOS.


&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
OFFSHORE LOW PRESSURE STRENGTHENS RAPIDLY MONDAY NIGHT...WHILE AN
UPPER LOW MOVES ACROSS THE CWA INTO THE ATLANTIC OCEAN.
ENOUGH MOISTURE OVER THE AREA...COMBINED WITH TEMPS BELOW FREEZING
OVER MOST OF THE CWA...WILL RESULT IN CONTINUED SNOW. MAIN
QUESTION FOR MONDAY NIGHT PERIOD WILL BE WHETHER AN AXIS OF
HEAVIER SNOW WILL SET UP WEST OF CHESAPEAKE BAY BEFORE LIFTING OFF
TO THE NORTHEAST. A WINTER STORM WATCH HAS BEEN ISSUED FOR THE
MARYLAND COUNTIES ALONG THE WESTERN SHORE OF CHESAPEAKE BAY.
FURTHER WEST...ANOTHER INCH OR SO OF SNOW IS LIKELY ACROSS NORTH
CENTRAL MD...THE EASTERN WV PANHANDLE...THE WASHINGTON DC METRO
AND NORTHERN VA. REFRAINED FROM EXTENDING THE WINTER WX ADVISORY
AT THIS TIME DUE TO THE LIKELIHOOD THAT ADDITIONAL SNOW WOULD TAKE
PLACE AFTER EVENING RUSH HOUR...AND END BEFORE THE TUESDAY MORNING
RUSH. THE LOW WILL CONTINUE TO PUSH TO THE NORTHEAST
TUESDAY...ALTHOUGH GFS AND ECMWF DIFFER ON WHETHER IT PROGRESSES
FARTHER THAN LONG ISLAND. BEST CHANCE FOR ADDITIONAL SNOW
ACCUMULATION CONTINUES TO BE ALONG THE WESTERN SHORE OF CHESAPEAKE
BAY...WITH SNOW OTHERWISE ENDING FROM WEST TO EAST ACROSS THE CWA.
COLD AIR WILL ADVECT INTO THE REGION WITH NORTHERLY FLOW AROUND
THE BACK SIDE OF THE LOW...WITH GUSTY WINDS LIKELY, HIGH TEMPS
TUESDAY WITH BE IN THE 30S.

COMBINATION OF STRONG HIGH PRESSURE TO THE WEST AND THE OFFSHORE
LOW EAST OF NEW ENGLAND WILL CONTINUE BRING IN VERY COLD AIR FROM
CANADA TUESDAY NIGHT. LOW TEMPS WILL DROP INTO THE TEENS OVER MUCH
OF THE CWA...WITH LOW 20S ALONG AND EAST OF I-95. ANY REMAINING
PRECIP COMES TO AN END TUESDAY NIGHT...EXCEPT POTENTIAL UPSLOPE
SNOW OVER THE POTOMAC HIGHLANDS.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
HIGH PRESSURE WILL BUILD ACROSS THE REGION WEDNESDAY AND WEDNESDAY
NIGHT. DRY CONDITIONS EXPECTED WITH HIGH AND LOW TEMPERATURES ABOUT
10 DEGREES BELOW NORMAL.

HIGH PRESSURE WILL MOVE EAST THURSDAY TO ALLOW FOR A GREAT LAKES LOW
PRESSURE SYSTEM TO DRAG A COLD FRONT ACROSS THE REGION LATE THURSDAY
AND THURSDAY NIGHT. THERE WILL LIKELY BE A PERIOD OF LIGHT RAIN AND
LIGHT SNOW ALONG THE LOW`S WARM FRONT AND AHEAD OF THE LOW PRESSURE
SYSTEM. AS WE VENTURE INTO THURSDAY NIGHT AND THE LOW PASSES
OVERHEAD WITH A TRAILING COLD FRONT...SNOW SHOWERS ARE EXPECTED AND
COULD LEAD TO A SMALL ACCUMULATION. ADDITIONAL AND HIGHER
ACCUMULATIONS ARE EXPECTED ALONG THE WESTERN RIDGES IN THE POTOMAC
HIGHLANDS DUE TO UPSLOPE WIND. TEMPERATURES WILL REMAIN BELOW NORMAL
BY ABOUT 3 TO 5 DEGREES.

THERE IS A CHANCE FOR LINGERING SNOW SHOWERS FRIDAY...MAINLY IN THE
WEST AND NORTH AS AN UPPER LEVEL TROUGH OF LOW PRESSURE PIVOTS
ACROSS THE REGION. A DOWNSLOPING WIND OFF OF THE POTOMAC HIGHLANDS
AND BLUE RIDGE SHOULD SUPPRESS A LOT OF THE SNOW SHOWERS.

HIGH PRESSURE WILL BUILD INTO THE REGION LATE FRIDAY THROUGH
SUNDAY...ALLOWING FOR DRIER AND MORE PEACEFUL WEATHER CONDITIONS.
TEMPERATURES SHOULD REMAIN BELOW NORMAL.



&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
VFR CONDITIONS THIS AFTN WITH LOWERING CIGS HEADING INTO THIS EVENING.
WINDS LIGHT FROM THE SOUTH BCMG LIGHT/VRB IN THE AFTN AS THEY BACK
TO THE EAST.

SUB-VFR CONDITIONS FIRST HALF OF THE NIGHT...WITH IFR BCMG LIKELY
AFTR 06Z AS THE PCPN OVERSPREADS THE REGION. LIFR CONDITIONS PSBL AS
EARLY AS 09Z...AND LASTING THRU MON MORNING WITH PERIODS OF
HEAVIER SNOW. PCPN TYPE QUESTIONABLE AS PSBL RAIN/SNOW MIX OR ALL
RAIN AT KDCA/KBWI/KCHO AT FIRST...THEN BCMG ALL SNOW AFTR 12Z.
OTHER TERMINALS MORE LIKELY ONLY A BRIEF PERIOD OF RAIN/SNOW MIX
BCMG ALL SNOW OVERNIGHT.

ONGOING PCPN MONDAY WITH SNOW...IFR OR LOWER CONDITIONS LIKELY.
ANOTHER ROUND OF HEAVIER PCPN (ALL SNOW) MON NIGHT INTO TUES KEEPS
IFR OR LOWER CONDITIONS IN PLACE.

SUB-VFR CONDITIONS LIKELY WITH LIGHT SNOW MONDAY NIGHT. HEAVIER
MAY DEVELOP MONDAY NIGHT OR TUESDAY MORNING NEAR KBWI/KMTN WITH
N-NW WINDS GUSTING 20-25KT. SNOW MAY CONTINUE AT KBWI/KMTN
TUESDAY. ANY LEFTOVER SNOW AT THE OTHER TERMINALS SHOULD END.
GUST NW WINDS EXPECTED ACROSS THE REGION...AROUND 20-25KT...WITH
SOME 30KT GUSTS PSBL. VFR TUES NIGHT. GUSTY NW WINDS CONTINUE.

VFR CONDITIONS WEDNESDAY. HOWEVER...NORTHWEST WINDS WILL BE
GUSTING 20 TO 30 KNOTS.

IFR OR PERHAPS LIFR CONDITIONS COULD DEVELOP THURSDAY WITH PERIODS
OF LIGHT RAIN AND LIGHT SNOW NEAR THE TERMINALS WITH AN APPROACHING
LOW PRESSURE SYSTEM.
&&

.MARINE...
SUB-SCA CONDITIONS LATE THIS AFTN...WITH INCREASING WINDS TONIGHT.
THE SCA GOES IN EFFECT THIS EVENING...BUT THE BETTER CHC FOR GUSTS
TO 20 KTS LOOKS TO BE AFTER 06Z...AND ESPECIALLY THEN DURING THE DAY
MONDAY.

GUSTY N-NW WINDS EXPECTED ACROSS THE WATERS MONDAY NIGHT AS LOW
PRESSURE STRENGTHENS OFFSHORE. FOR NOW...SCA GUSTS LIKELY ON ALL
WATERS...EXCEPT OVER THE SOUTHERNMOST ZONES ON THE BAY AND TIDAL
POTOMAC WHERE A GALE WARNING HAS BEEN ISSUED. GALE MAY NEED TO BE
EXPANDED BY TUESDAY MORNING AS COLDER AIR ALOFT ALLOWS BETTER MIXING.

SMALL CRAFT ADVISORIES ARE LIKELY WEDNESDAY MORNING AS NORTHWEST
WINDS GUST 20 TO 30 KNOTS.

SMALL CRAFT ADVISORIES MAY BE NEEDED WEDNESDAY AFTERNOON...DEPENDING
ON HOW FAST NORTHWEST WINDS DIMINISH INTO THE OVERNIGHT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...WINTER WEATHER ADVISORY FROM 2 AM TO 6 PM EST MONDAY FOR
     DCZ001.
MD...WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM EST MONDAY
     FOR MDZ003.
     WINTER WEATHER ADVISORY FROM 2 AM TO 6 PM EST MONDAY FOR
     MDZ013-014.
     WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 6 PM EST
     MONDAY FOR MDZ004>006-011-503>508.
     WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY
     AFTERNOON FOR MDZ006-011-014-017-018-507-508.
     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM EST MONDAY
     FOR MDZ501-502.
VA...WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM EST MONDAY
     FOR VAZ028.
     WINTER WEATHER ADVISORY FROM 2 AM TO 6 PM EST MONDAY FOR
     VAZ039-051>054-502.
     WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 6 PM EST
     MONDAY FOR VAZ025>027-029>031-040-501-503>507.
WV...WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM EST MONDAY
     FOR WVZ051>053.
     WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 6 PM EST
     MONDAY FOR WVZ505-506.
     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM EST MONDAY
     FOR WVZ050-055-501>504.
MARINE...SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 6 PM EST MONDAY
     FOR ANZ530>543.
     GALE WARNING FROM 6 PM MONDAY TO 6 AM EST TUESDAY FOR ANZ534-
     537.

&&

$$
SYNOPSIS...SEARS/KCS
NEAR TERM...SEARS
SHORT TERM...KCS
LONG TERM...KLW
AVIATION...SEARS/KCS/KLW
MARINE...SEARS/KCS/KLW







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