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000
FXUS61 KLWX 151311
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
911 AM EDT SAT JUN 15 2013

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE MID-ATLANTIC TODAY BEFORE MOVING
OFF THE COAST TONIGHT THROUGH SUNDAY. A COLD FRONT WILL SLOWLY
MOVE THROUGH THE REGION SUNDAY NIGHT INTO MONDAY NIGHT. A
DISTURBANCE MAY AFFECT THE AREA TUESDAY...THEN HIGH PRESSURE WILL
BUILD ACROSS THE REGION THROUGH THE MIDDLE PORTION OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE BUILDS OVER THE MID-ATLANTIC TODAY. ASIDE FROM A FEW
CIRRUS SNEAKING IN FROM THE WEST...HIGH PRESSURE SHOULD GUARANTEE
PLENTY OF SUNSHINE TODAY WITH HIGH TEMPERATURES WARMING INTO THE
LOWER TO MID 80S ACROSS THE CWA EXCEPT FOR 70S OVER THE HIGHER
ELEVATIONS.

HIGH PRESSURE WILL MOVE OFF THE COAST TONIGHT...BUT IT WILL
REMAIN CLOSE ENOUGH FOR MORE DRY CONDITIONS. MIN TEMPS WILL RANGE
FROM THE MIDDLE 50S IN RURAL AREAS AND SHELTERED VALLEYS TO THE
UPPER 60S AND LOWER 70S IN DOWNTOWN WASHINGTON/BALTIMORE. THERE
WILL BE SOME HIGH AND MID-LEVEL CLOUDS MOVING IN OVERNIGHT WELL
AHEAD OF AN UPPER-LEVEL DISTURBANCE OVER THE MIDWEST.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
LARGE SCALE FEATURES SUNDAY THROUGH MONDAY NIGHT ARE A BERMUDA
HIGH...A TROUGH OVER THE NRN GREAT LAKES...AND A WEAK COLD FRONT IN
BETWEEN SAGGING ACROSS THE EAST-CENTRAL STATES.

SUNDAY...CONVERGENCE ZONE/COLD FRONT SAGS SOUTH INTO THE CENTRAL
MID-ATLANTIC THROUGH THE DAY. POPS INCREASE THROUGH THE DAY AS
FORCING SHIFTS INTO THE AREA IN THE PEAK HEATING OF THE AFTERNOON.
SCALED BACK LIKELY POPS FOR ALONG THE ALLEGHENY FRONT... WITH
SCATTERED COVERAGE EAST TO THE BAY. SWLY FLOW MIXES 16C 850MB
TEMPS...EXPECT MAX TEMPS MID TO UPR 80S...A FEW DEGREES ABOVE NORMAL.

CONVERGENCE ZONE AND ASSOCIATED PRECIP PERSISTS ACROSS THE AREA INTO
MONDAY NIGHT UNTIL LOW PRESSURE OVER THE GREAT LAKES FINALLY EJECTS
EAST...AMPLIFYING THE UPPER-AIR PATTERN AND PUSHING THE COLD FRONT
INTO THE SRN MID-ATLANTIC. MAINLY DIURNALLY DRIVEN THUNDERSTORMS
THROUGH MONDAY EVENING. SIMILAR TEMPERATURES MONDAY WITH 16C 850MB
TEMPS AGAIN.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
00Z OPERATIONAL GFS PROGS A SHORTWAVE LOW TO EJECT FROM COLORADO
SUNDAY NIGHT...RIDGE ALONG THE FRONTAL ZONE...AND TRACK ACROSS THE
CENTRAL MID-ATLANTIC TUESDAY NIGHT. THIS WOULD BE A FAVORABLE TRACK
FOR TUESDAY AFTERNOON/EVENING SEVERE WEATHER...INCLUDING TORNADOES
AND DAMAGING WINDS. ANY SHORTWAVE IN THE 00Z ECMWF (AS WELL AS THE
PREVIOUS 12Z RUN) IS TOO WEAK TO DEVELOP A SURFACE FEATURE.
FURTHERMORE...MOST GEFS ENSEMBLE MEMBERS DO NOT FEATURE A LOW BELOW
1005MB IN THE MID-ATLANTIC ON MONDAY. THIS GREATLY LIMITS CONFIDENCE
IN THE SEVERE THREAT FOR TUESDAY. WILL CONTINUE TO REFRAIN FROM
MENTIONING THIS IN THE HWO.

OTHERWISE...SURFACE HIGH PRESSURE WILL SHIFT ACROSS THE REGION
THROUGH THE MIDWEEK WITH A REPRIEVE FROM THE ACTIVE WEATHER AND EVEN
A SHOT OF CANADIAN AIR AND BELOW NORMAL TEMPERATURES.

&&

.AVIATION /13Z SATURDAY THROUGH WEDNESDAY/...
HIGH PRESSURE BUILDS OVERHEAD TODAY...THEN MOVES OFF THE COAST
TONIGHT. NO FLIGHT RESTRICTIONS EXPECTED DURING THIS TIME...WITH
LIGHT W/NW WINDS BECOMING S THIS EVENING.

VFR CONTINUES INTO SUNDAY AS HIGH PRESSURE MOVES TO BERMUDA.
SCATTERED THUNDERSTORMS AHEAD OF A WEAK COLD FRONT SPREAD ACROSS THE
TERMINALS SUNDAY AFTERNOON WITH AN ACTIVE PERIOD THEN INTO MONDAY
EVENING WITH DIURNALLY DRIVEN CONVECTIVE STORMS.

&&

.MARINE...
NO MARINE HEADLINES ARE EXPECTED THROUGH TONIGHT. A NORTHWEST FLOW
WILL TURN ONSHORE BY LATE IN THE DAY. SOUTHERLY WINDS WILL INCREASE
TONIGHT AS HIGH PRESSURE MOVES OFF THE COAST...BUT WIND SPEEDS
SHOULD REMAIN BELOW SCA CRITERIA.

SLY/SWLY FLOW INCREASES SUNDAY WITH MORNING SLY CHANNELING AND
AFTERNOON SWLY FLOW GUSTING AROUND 25 KT AS INDICATED BY SCA
COVERAGE THAT BEGINS 6 AM FOR SRN MD WATERS...AND IS ACROSS ALL
WATERS BY 10 AM. SCA LIKELY EXTENDED FOR PORTIONS OF THE WATERS
FOR SUNDAY EVENING. ACTIVE WEATHER SUNDAY EVENING INTO MONDAY
NIGHT OVER THE WATERS AS A COLD FRONT SAGS THROUGH THE AREA.

&&

.TIDES/COASTAL FLOODING...
EVEN WITH A NORTHWEST WIND...POSITIVE ANOMALIES ARE BEING OBSERVED
ON THE CHESAPEAKE BAY WESTERN SHORE...ON THE ORDER OF 1 TO 1.4
FT. IT IS SURMISED THAT WATER THAT PILED UP OVER THE SOUTHERN BAY HAS
RETURNED NORTH RESULTING IN THE POSITIVE DEPARTURES.

HIGH TIDE HAS PASSED FURTHER SOUTH ALONG THE BAY SO THE COASTAL
FLOODING ADVISORY FOR ST MARYS COUNTY HAS BEEN CANCELLED. HIGH
TIDE WILL AFFECT AREAS ALONG CALVERT/ANNE ARUNDEL COUNTIES OVER
THE NEXT COUPLE HOURS. APAM2 HAS ALREADY SURPASSED ITS MINOR
THRESHOLD /2.4 MLLW/ AND HIGH TIDE OCCURS AT 1014 AM. WATER
LEVELS OF 2.8-2.9 FT MLLW CAN BE EXPECTED AT THIS TIME. THIS
RAISES CONCERN FOR SENSITIVE AREAS FURTHER NORTH ALONG THE WESTERN
SHORE OF THE BAY...PARTICULARLY BOWLEY BAR/BALTIMORE. IF ANOMALIES
STAY THE SAME...BLTM2 WILL REACH ITS MINOR THRESHOLD OF 3.0 FT
MLWW...AND FURTHER NORTH HDGM2 WILL GET CLOSE OT ITS 4.0 FT
THRESHOLD. THEREFORE HAVE EXPANDED THE ADVISORY FURTHER NORTH FOR
MINOR/NUISANCE TIDAL FLOODING AROUND HIGH TIDE. WILL ALSO HAVE TO
KEEP AN EYE ON THE UPPER TIDAL POTOMAC NEAR WASHINGTON D.C. BUT AT
THIS TIME BELIEVE WATER LEVELS WILL REMAIN JUST BELOW MINOR
THRESHOLDS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...COASTAL FLOOD ADVISORY UNTIL NOON EDT TODAY FOR MDZ014-018.
     COASTAL FLOOD ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR
     MDZ007-011.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT SUNDAY FOR
     ANZ530>533-535-536-538>542.
     SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EDT SUNDAY FOR ANZ534-
     537-543.

&&

$$
BPP/BJL/BAJ