-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 310537
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1237 AM EST SAT JAN 31 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS THE REGION FOR THE FIRST HALF OF
THE WEEKEND. LOW PRESSURE WILL IMPACT THE AREA LATE SUNDAY INTO
MONDAY. HIGH PRESSURE WILL RETURN FOR THE FIRST HALF OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
UPPER TROUGH HAS SWUNG EAST OF THE CWA WITH RIDGING BUILDING IN
FROM THE WEST. FAIRLY WELL ALIGNED NORTHWEST WINDS ARE IN
PLACE...THOUGH AS THE SFC HIGH BUILDS IN...PRESSURE GRADIENT WILL
GRADUALLY WEAKEN...ALLOWING FOR THE WINDS TO CONTINUE TO SUBSIDE
TONIGHT. WITH NO RECENT REPORTS OF ADVISORY LVL WINDS...AND THE
TREND OF DECREASING...HAVE ALLOWED THE REMAINDER OF THE WIND
ADVISORY TO EXPIRE. GOING WEST...WIND AND VERY COLD TEMPERATURES
WILL ALLOW WIND CHILL VALUES TO DIP NEAR 10 BELOW OVER THE POTOMAC
HIGHLANDS AND AS SUCH AM CONTINUING THE WIND CHILL ADVISORY
THROUGH THE MORNING HOURS.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
SAT HIGH PRES OVR THE AREA. E OF THE HIGHLANDS HIGHS SHOULD CLIMB
INTO THE 30S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
ZONAL FLOW WILL BE OVER THE AREA SATURDAY NIGHT AHEAD OF THE NEXT
APPROACHING SHORTWAVE TROUGH IN THE PLAINS...WHILE SFC HIGH PRESSURE
SLIDES OFF THE SE COAST. LITTLE OF NOTE OTHER THAN INCREASING MID
AND HIGH LEVEL CLOUDS. LOWS GENERALLY IN THE 20S.

THE LOW PRESSURE SYSTEM WILL TAKE SHAPE OVER THE OHIO VALLEY ON
SUNDAY. ISENTROPIC LIFT MAY ALLOW SOME LIGHT SNOW TO BEGIN TO BREAK
OUT...ESPECIALLY DURING THE AFTERNOON AND ALONG THE MD/PA BORDER.
COLUMN ALOFT WILL BE COLD ENOUGH FOR SNOW...BUT SFC TEMPS WILL TRY
TO EDGE ABOVE FREEZING AND IN FACT MAY RISE ABOVE 40 DEG SOUTH OF
US-50...SO SOME RAIN MAY MIX IN WITH SOUTHERN EXTENT. QPF WILL
BE VERY LIGHT THOUGH AND WHERE SNOW DOES FALL...AMOUNTS WOULD LIKELY
BE LESS THAN AN INCH.

30.12Z MODEL SUITE HAS HELD SERVE WITH THE TRACK OF THE LOW PRESSURE
SUNDAY NIGHT...WITH EVEN THE COLDER CANADIAN SOLUTION NOW ON THE
NORTHWARD TREND. PER COLLAB WITH WPC...THIS SEEMS TO BE A STABLE
TREND...AND IF ANYTHING MAY END UP BEING A BIT FURTHER NORTH. THIS
SENDS THE TRACK OF THE SFC LOW RIGHT OVER THE HEART OF THE CWA AND
DIMINISHES THE PROB OF A MORE SIGNIFICANT SNOW. THIS ALSO SEEMS
REASONABLE SINCE THERE IS NOT A STRONG BLOCKING HIGH POSITIONED TO
THE NORTH...RATHER AN EXTENSION OF A HIGH OVER THE PLAINS.
TEMPERATURES LIKELY HOLD FAIRLY STEADY SUNDAY NIGHT. GREATEST CHANCE
FOR ACCUMULATING SNOW WILL BE ALONG THE M-D LINE AND IN THE POTOMAC
HIGHLANDS. SOUTHERN CWA MAY EVENTUALLY BECOME ALL RAIN. IN BETWEEN
THE CONCERN WOULD BE FOR A LITTLE MIX OF EVERYTHING...AND WILL HAVE
TO WATCH OUT FOR MODELS TRYING TO KEEP TEMPERATURES TOO WARM ON AN
OVERNIGHT PRECIP EVENT WITH IN-SITU CAD/COLD AIR LOCKING IN PLACE IN
THE CLIMO FAVORED AREAS. THIS COULD RESULT IN FZRA WHERE MODELS
DEPICT IT BEING WARM ENOUGH FOR ONLY RAIN. DO HAVE SOME MINOR ICE
ACCUMS FROM SHENANDOAH VALLEY UP TO AND ALONG THE M-D LINE...WHERE
EVEN THEY WILL LIKELY MIX SOME AND LIMIT SNOW TOTALS. DC/BALT METROS
ARE RIGHT ON THE EDGE...SO PLEASE KEEP TRACK OF THE LATEST FORECASTS
AS THE EXACT TRACK OF THE LOW IS FINE TUNED. WILL HOLD OFF ON
ISSUING ANY SORT OF WATCH ON THIS FORECAST ISSUANCE DUE TO THE LOW
CONFIDENCE...LONG LEAD TIME...AND ONLY MARGINAL AMOUNTS FOR WARNING
CRITERIA ON THE NORTHERN TIER OF THE CWA.

A LOW PRESSURE SYSTEM NEAR METRO D.C. WILL QUICKLY MOVE OFFSHORE THE
EAST COAST BY MIDDAY MONDAY. THE THREAT FOR A PERIOD OF ACCUMULATING
SNOW OR PERHAPS A MIX OF RAIN AND SNOW EXISTS FOR THE REGION
THROUGHOUT THE DAY...ESPECIALLY OVER THE EASTERN HALF. HIGH AND LOW
TEMPERATURES MONDAY AND MONDAY NIGHT WILL AVERAGE 10 TO 15 DEGREES
BELOW NORMAL...ESPECIALLY LATE MONDAY THROUGH MONDAY NIGHT WITH LOWS
BOTTOMING OUT NEAR ZERO OR SINGLE DIGITS. AS FOR PRECIPITATION
MONDAY NIGHT...THERE IS A CHANCE FOR SOME GOOD UPSLOPE SNOWFALL IN
THE POTOMAC HIGHLANDS.

HIGH PRESSURE WILL DOMINATE THE REGION TUESDAY AND TUESDAY
NIGHT...BRINGING DRY CONDITIONS. TEMPERATURES WILL REMAIN NEARLY 10
DEGREES BELOW NORMAL.

A COLD FRONT WILL SAG SOUTH OUT OF THE GREAT LAKES WEDNESDAY AND
WEDNESDAY NIGHT BEFORE PUSHING ACROSS THE REGION THURSDAY.
THERE IS A CHANCE OF SOME LIGHT SNOW OR A MIX OF SNOW AND
RAIN...MAINLY WEDNESDAY NIGHT INTO THURSDAY. TEMPERATURES WEDNESDAY
THROUGH THURSDAY WILL NOT BE AS COLD AS RECENT DAYS...BUT WILL STILL
BE CHILLY.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
HIGH CONFIDENCE VFR CONDITIONS THROUGH SAT NIGHT. NW FLOW WILL
GRADUALLY DIMINISH TONIGHT...THOUGH GUSTS INTO THE 20S STILL
EXPECTED THRU DAYBREAK.

IFR CONDITIONS POSSIBLE FROM SUNDAY AFTERNOON INTO SUNDAY NIGHT
AS LOW PRESSURE CROSSES THE AREA. A MIX OF PRECIPITATION TYPES
WILL BE LIKELY AT ALL TERMINALS.

IFR OR LIFR CONDITIONS COULD START THE DAY MONDAY WITH PERIODS OF
LIGHT SNOW ACROSS THE TERMINALS. THERE COULD BE A LITTLE RAIN MIX IN
NEAR CHO. CONDITIONS SHOULD BECOME MVFR BY THE AFTERNOON BEFORE
IMPROVING TO VFR LATE IN THE DAY. WINDS SW BECOMING NW LESS THAN 10
KNOTS EARLY MONDAY THEN INCREASING NW 15 KNOTS WITH GUSTS 20 TO 30
KNOTS MIDDAY MONDAY AND MONDAY AFTERNOON.

VFR CONDITIONS MONDAY NIGHT AND TUESDAY. WINDS CONTINUING NW 15
KNOTS GUSTS 20 TO 30 KNOTS MONDAY BEFORE DIMINISHING N BECOMING S AT
5 TO 10 KNOTS TUESDAY.

&&

.MARINE...
GALES CONTINUE OVER THE WATERS THIS EVENING...WITH THE GALE
WARNING CONTINUING OVERNIGHT. EVENTUALLY THIS WILL BE DOWNGRADED
TO A SMALL CRAFT ADVISORY BUT THERE IS SOME UNCERTAINTY AS TO WHEN
GALES WILL END. IT/S POSSIBLE THEY CONTINUE UNTIL SATURDAY
MORNING...AT LEAST OVER THE LOWER MD BAY. IF THAT/S THE CASE THE
GALE WOULD NEED TO BE EXTENDED. OTHERWISE...SCA CONDITIONS LIKELY
SATURDAY.

WINDS ARE FORECAST TO REMAIN BELOW SCA CRITERIA FROM SATURDAY
NIGHT THROUGH SUNDAY NIGHT. LOW PRESSURE WILL BRING MIXED
PRECIPITATION...ESPECIALLY THE UPPER POTOMAC AND NORTHERN
BAY...SUNDAY AFTERNOON INTO SUNDAY NIGHT.

SMALL CRAFT ADVISORIES ARE LIKELY MONDAY AFTERNOON THROUGH MONDAY
NIGHT.

NO MARINE HAZARDS EXPECTED TUESDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WIND CHILL ADVISORY UNTIL 9 AM EST THIS MORNING FOR MDZ501.
VA...WIND CHILL ADVISORY UNTIL 9 AM EST THIS MORNING FOR VAZ503-504.
WV...WIND CHILL ADVISORY UNTIL 9 AM EST THIS MORNING FOR WVZ501-503-
     505-506.
MARINE...GALE WARNING UNTIL 4 AM EST EARLY THIS MORNING FOR ANZ530>543.

&&

$$