Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 041309
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
909 AM EDT MON MAY 4 2015

.SYNOPSIS...
HIGH PRESSURE BECOMES ANCHORED OFF THE MID ATLANTIC COAST THROUGH
WEDNESDAY. A BACKDOOR COLD FRONT APPROACHES FROM THE NORTH
THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE HAS MOVED PRIMARILY OFF THE COAST AND HAS FLATTENED
OUT...WITH THE MORE DOMINANT CENTRAL PRESSURE FIELDS EXPECTED
ACROSS THE CAROLINAS TONIGHT. MEANWHILE...A TROUGH OF LOW PRESSURE
CROSSES NEW ENGLAND LATER TODAY THROUGH TONIGHT. THE PRESSURE
GRADIENT BTWN THESE TWO SYSTEMS WILL BEGIN TO TIGHTEN TODAY AS
WINDS BECOME MORE S-SW. EXPECT BREEZY WINDS THIS AFTN WITH GUSTS
OF 15-20 MPH. AMPLE SUNSHINE AND DECENT MIXING WILL ALLOW HIGHS TO
CLIMB INTO THE LOW-MID 80S (EXCEPT NEAR OCEAN CITY WHERE HIGHS
WILL ONLY REACH THE LOW-MID 70S DUE TO SLY ONSHORE WINDS ALONG THE
ATLANTIC COASTLINE OF MD). A MILD NIGHT AHEAD IN CONTINUED S-SW
FLOW. EXPECT LOWS IN THE UPPER 50S TO LOWER 60S.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
FLATTENED HIGH PRESSURE REMAINS ACROSS THE CAROLINAS TUESDAY AS
THE NEW ENGLAND TROUGH DRAGS A RELATIVELY FLAT FRONTAL BOUNDARY
ALONG THE MASON-DIXON LINE TUESDAY INTO TUESDAY NIGHT. LATEST
00Z MODEL CROSS SECTIONS ARE NOW SHOWING A SLIGHT INCREASE IN
AVAILABLE MOISTURE WITH SLIGHTLY STRONGER OMEGA FIELDS DURING THE
LATE AFTN/EARLY EVENING TIMEFRAME (OR DURING BEST DAYTIME
HEATING/INSTABILITY). HOWEVER...2-D PRECIPITATION FIELDS ALSO
INDICATE THAT AVAILABLE MOISTURE IS GETTING SHEARED APART AS IT
APPROACHES THE MID ATLANTIC REGION. WILL NEED TO KEEP AN EYE ON
WATER VAPOR TRENDS AS THE CURRENT COMPLEX IN THE MIDWEST SHIFTS
TWD NEW ENGLAND WITH THE TROUGH/SFC FRONTAL BOUNDARY. HAVE
THEREFORE HELD ONTO SLIGHT CHANCE POPS FROM LOUISA COUNTY TO THE
NRN NECK TO THE MD LOWER EASTERN SHORE BEGINNING LATE TUE AFTN...
INCREASING TO CHANCE POPS (NO HIGHER THAN 30%) TUE EVENING ACROSS
THE NRN NECK AND MD/VA EASTERN SHORE. SW WINDS AND TEMPS WARMING
INTO THE MID 80S FOR HIGHS WILL HELP TO DESTABILIZE THE ATMOSPHERE...
AND THUNDERSTORMS MAY BE POSSIBLE IN THE AFTN/EARLY EVENING. MODEL
CROSS SECTIONS INDICATE THAT MOISTURE FIELDS DIMINISH AFTER
MIDNIGHT TUESDAY NIGHT...HOWEVER LIGHT SHOWERS MAY LINGER OVER THE
MD LOWER EASTERN SHORE OVERNIGHT TUESDAY SO KEPT SLIGHT CHANCE
POPS HERE DURING THIS TIME. ANOTHER NIGHT WITH MILD LOWS IN THE
UPPER 50S TO LOWER 60S.

FORECAST MODELS THEN DIVERGE IN THEIR SOLUTIONS BEGINNING
WEDNESDAY. HIGH PRESSURE BUILDS DOWN FROM CANADA AND NORTH OF THE
RELATIVELY FLAT SFC FRONT NEAR THE MASON-DIXON LINE. MEANWHILE...
LOW PRESSURE DEVELOPING OFF THE EAST COAST OF FLORIDA IS EXPECTED
TO LIFT TWD THE SOUTHEAST COAST INTO WEDNESDAY NIGHT. THERE IS
SOME AGREEMENT AMONGST MODELS TO KEEP PRECIP OVER THE AREA THROUGH
WEDNESDAY AS THE SFC BOUNDARY SAGS SWD AND A LEESIDE TROUGH STARTS
TO DEVELOP. THE EXACT LOCATION AND TIMING OF PRECIP IS WHAT IS IN
QUESTION AND HAVE THEREFORE TRIED TO SPLIT THE DIFFERENCE BTWN THE
MORE AGGRESSIVE GFS...THE DRIER NAM...AND THE MIDDLE OF THE ROAD
ECMWF. THIS SHOULD KEEP LIGHT SHOWERS OVER THE NRN HALF OF THE FA
(NORTH OF RICHMOND) WEDNESDAY MORNING...WHICH SHOULD THEN SHIFT
WWD DURING WEDNESDAY AFTN/EVENING AS ADDITIONAL INSTABILITY
TRIGGERS SHOWERS NEAR THE LEE TROUGH BOUNDARY. THUNDERSTORMS ARE
POSSIBLE ONCE AGAIN WEDNESDAY AFTN/EARLY EVENING. ANY PRECIPITATION
THAT OCCURS IS EXPECTED TO TAPER OFF THROUGH THE EVENING WITH DRY
CONDITIONS OVERNIGHT. SE VA AND NE NC WILL REMAIN PRECIP-FREE ON
WEDNESDAY/WEDNESDAY NIGHT. HIGHS WEDNESDAY 80-84 INLAND...
MID-UPPER 70S AT THE IMMEDIATE COAST AND FOR THE MD/VA EASTERN
SHORE. LOWS WEDNESDAY NIGHT REMAIN MILD WITH LOWS IN THE UPPER 50S
TO LOWER 60S.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
FOLLOWED CLOSE TO WPC AND SUPERBLEND GUIDANCE FOR THE LONG TERM.
UPPER LEVEL RIDGING WILL PREVAIL OVER THE EASTERN CONUS. A BACK DOOR
COLD FRONT MOVES SOUTH OVER THE MID ATLANTIC STATES WEDNESDAY NIGHT
AND THEN WASHES OUT OVER SRN PORTIONS THURSDAY. A SURFACE HIGH
RIDGES INTO THE AREA FROM THE EAST. LOW PRESSURE MEANDERS OFF THE
CAROLINA COAST LATE IN THE WEEK. THIS LOW HAS THE POTENTIAL TO
BECOME A SUBTROPICAL STORM (SEE TROPICAL WEATHER OUTLOOK). DETAILS
OF THE PROGRESS OF THE LOW ARE UNCERTAIN BUT RIDGING IS EXPECTED TO
KEEP THE LOW AND ITS IMPACT TO THE SOUTH OF THE CWA.

DAILY CHANCES FOR SHOWERS WITH SCATTERED AFTERNOON THUNDERSTORMS ARE
EXPECTED DURING THE LONG TERM WITH POPS OF 20 TO 30 PERCENT...MAINLY
OVER SRN AND WRN PORTIONS OF THE CWA.

LOWERED TEMPERATURES A BIT THURSDAY BEHIND THE BACK DOOR FRONT.
OVERALL...HIGH TEMPERATURES ARE EXPECTED RANGE THROUGH THE UPR 70S
TO LWR 80S EXCEPT UPR 60S TO LWR 70S NEAR THE COAST. LOWS RANGE FROM
THE UPR 50S TO LWR 60S.

&&

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
HIGH PRESSURE IS CENTERED OFF THE MID ATLNATIC COAST. A COLD FRONT
EXTENDED NE TO SW IN THE UPPER MIDWEST.

AS OF 13Z...THE SKY WAS CLEAR ACROSS THE TAF SITES THIS MORNING. A
SW BREEZE WAS PRESENT. LITTLE CHANGE IS EXPECTED THROUGH TUESDAY
MORNING. WINDS MAY BECOME GUSTY AT TIMES THIS AFTERNOON AND SW
WINDS CONTINUE AROUND 5 TO 8 KNOTS OVERNIGHT INTO TUESDAY MORNING.

OUTLOOK: SIMILAR CONDITIONS INTO TUE...DRY/MOSTLY SUNNY WITH S/SW
WINDS. BY TUE EVENING/NIGHT THERE WILL BE THE POSSIBILITY OF A FEW
SHOWERS/TSTMS AT KSBY...AND A CHANCE ACROSS MOST OF THE AREA BY
WEDNESDAY AFTERNOON AND EVENING. WINDS GENLY SHIFT TO THE E/NE THU
WITH CONTINUED VFR CONDITIONS OUTSIDE OF ANY ISOLATED CONVECTION.

&&

.MARINE...
SEAS NOW DOWN TO 3-4 FT ON THE OCEAN. SFC HIGH PRESSURE IS
CENTERED ALONG/OFF THE NC COAST. SYNOPTIC PRESSURE GRADIENT TO
REMAIN FAIRLY WEAK TODAY...ALTHOUGH IT WILL STRENGTHEN A BIT THIS
AFTN/TONIGHT AS THE SFC HIGH BECOMES CENTERED OFF THE NC COAST
WHILE LOW PRESSURE MOVES THROUGH QUEBEC. WHILE THERE WILL LIKELY
BE SOME GUSTS TO 15-20 KT BY TONIGHT...THIS STILL LOOKS TOO
MARGINAL TO RAISE ANY HEADLINES IN THE BAY AS MIXING WILL NOT BE
OPTIMAL (VERY WARM AIRMASS OVER RELATIVELY COOL WATERS). SEAS IN
NRN COASTAL WATERS BUILD TO AROUND 4 FT...2-3 FT FARTHER SOUTH.
GRADIENT SLACKENS A BIT ON TUE...THEN INCREASES TUE NIGHT/EARLY
WED AS A BACKDOOR COLD FRONT APPROACHES FROM THE N. THE FRONT
LOOKS TO GRADUALLY PUSH INTO THE AREA ON WED AND DISSIPATE WED
NIGHT AS SFC HIGH PRESSURE BUILDS IN FROM THE N. COMBINED WITH SFC
LOW OFF THE GA/SC CST THERE COULD POTENTIALLY BE SOME INCREASE IN
WIND SPEEDS AS DIRECTIONS SHIFT TO THE E/NE. WHILE LATEST
WAVEWATCH GUIDANCE SHOWS INCREASE IN SEAS FOR LATER THU INTO
FRI...CURRENT TRACK OF SFC LOW STAYS TOO FAR SOUTH TO BRING ANY
SIGNIFICANT INCREASE IN SEAS AND WINDS TO THE LOCAL AREA (WILL
CONTINUE TO MONITOR TRENDS).

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...BMD
NEAR TERM...BMD
SHORT TERM...BMD
LONG TERM...LSA
AVIATION...LKB/DAP/LSA
MARINE...LKB



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