Area Forecast Discussion
Issued by NWS Upton, NY

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000
FXUS61 KOKX 301749
AFDOKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
149 PM EDT SAT AUG 30 2014

.SYNOPSIS...
HIGH PRESSURE ALONG THE NEW ENGLAND COAST WILL WORK FARTHER
OFFSHORE AS THE WEEKEND PROGRESSES. AT THE SAME TIME...LOW
PRESSURE ACROSS THE GREAT LAKES WORKS NORTHEAST AND INTO EASTERN
CANADA...SENDING A LOW PRESSURE TROUGH ACROSS THE AREA LATE
SUNDAY. WEAK HIGH PRESSURE BRIEFLY RETURNS BEFORE ANOTHER COLD
FRONT APPROACHES TUESDAY. THIS FRONT MOVES ACROSS LATE TUESDAY
NIGHT WITH HIGH PRESSURE BUILDING BACK IN FROM THE WEST FROM MID
TO LATE NEXT WEEK. ANOTHER COLD FRONT APPROACHES LATE NEXT FRIDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
BOTH HIGH PRESSURE ALOFT AND AT THE SFC TRACKS EAST OF THE AREA
WITH A RETURN SLY FLOW AND INCREASING LOW-LEVEL MOISTURE AS DEW
POINTS CLIMB INTO THE 60S. A SUBSIDENCE INVERSION WILL PUT A CAP
ON ANY CONVECTION.

PER SATELLITE...INCREASED SKY COVERAGE AS MOISTURE INCREASES
UNDERNEATH THE AFOREMENTIONED SUBSIDENCE INVERSION. PLENTY OF SC
FORECAST THIS AFTERNOON.

HIGH TEMPS WILL BE JUST BELOW NORMAL WITH READINGS IN THE MID TO
UPPER 70S. EXTRA CLOUD COVER MAY INHIBIT TEMPS FURTHER.

WITH INCREASING SOUTHERLY FLOW...THERE IS A MODERATE RISK OF RIP
CURRENTS THIS AFTERNOON/EVENING.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
WARM...MUGGY CONDITIONS DEVELOP AS A SLY FLOW SENDS DEW POINTS
THROUGH THE 60S TO AROUND 70 BY DAYBREAK SUN. THIS WILL RESULT IN
LOWS TONIGHT WELL INTO THE 60S.

MORE IMPORTANTLY....WARM ADVECTION IN A DEEP-LAYERED SW FLOW WILL
TRANSPORT TROPICAL MOISTURE FROM THE GULF COAST STATES NORTHWARD
INTO THE REGION WITH PW VALUES AROUND 2 INCHES SUN INTO SUN NIGHT.
THIS COMBINED WITH DAYTIME HIGHS IN THE 80S WILL ALLOW FOR A
DESTABILIZING AIRMASS WITH MDT-HIGH CAPES AND MARGINAL-MDT SHEAR.
A SHORT WAVE TROF ALOFT AND A SFC TROF ACROSS EASTERN PA WILL
LIKELY TRIGGER CONVECTION IN THE EARLY AFT WHICH WILL WORK INTO NE
NJ/LOWER HUDSON VALLEY IN THE MID AFT...THEN INTO NYC/CT/LI IN THE
LATE AFT/EVE HOURS. THERE IS SOME CONCERN THAT THE SFC TROF LAYS
DOWN ACROSS AREA DURING THE NIGHTTIME HOURS WITH THE POTENTIAL FOR
A CONVECTIVE COMPLEX AND TRAINING OF THUNDERSTORMS. THE PRIMARY
HAZARD WOULD BE FLASH FLOODING. RIGHT NOW...THE BEST CHANCE LOOKS
TO BE NEAR OR JUST EAST OF NYC AND ACROSS LI/COASTAL CT. THERE
STILL REMAINS A FAIR AMOUNT OF UNCERTAINTY WITH THE DETAILS AND
MODEL SOLUTIONS VARY WITH THE PROGRESSION OF THE SYSTEM.
OFTEN...IN AIRMASSES DEEP IN MOISTURE LIKE THIS...SUBTLE FEATURES
ARE ALL THAT IS NEEDED TO PROVIDE THE LIFT/FOCUS FOR HEAVY
RAINFALL. THE REAL CHALLENGE WILL BE PINPOINTING THE LOCATION.
SHOULD CONFIDENCE INCREASE WITH LOCATION AND TIMING...A FLOOD
WATCH MAY ISSUED LATER TODAY.

DEW POINTS WILL BE IN THE LOWER 70S SUN INTO SUN NIGHT...MAKING
FOR A VERY MUGGY SUN NIGHT. LOWS WILL RANGE FROM THE UPPER 60S TO
LOWER 70S.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
SCATTERED CONVECTION MAINLY MON MORNING DEPENDING ON WHERE THE SFC
TROF RESIDES. CONDITIONS ARE EXPECTED TO DRY OUT AFT/EVE WITH WEAK
HIGH PRESSURE NOSING IN FROM THE SW. WARM...MUGGY CONDITIONS TO
CONTINUE WITH HIGHS IN THE 80S AND DEW POINTS AROUND 70.

A LITTLE STRONGER PARENT LOW IN SOUTHEAST CANADA NEAR THE GREAT
LAKES MOVES INTO THE NORTHEAST TUESDAY NIGHT WITH AN ASSOCIATED
COLD FRONT MOVING IN OVERNIGHT INTO WEDNESDAY MORNING. THE FRONT
PUSHES EAST OF THE REGION WEDNESDAY WITH A WEAK HIGH BUILDING IN
FROM THE WEST THEREAFTER THROUGH EARLY FRIDAY. ANOTHER FRONT MAY
APPROACH FOR LATER NEXT FRIDAY.`

NEXT CHANCE OF CONVECTION WILL BE TUESDAY AFTERNOON THROUGH
TUESDAY NIGHT. MDT-HIGH CAPE ENVIRONMENT...BUT WEAKLY SHEARED.
THIS COULD RESULT IN A FEW STRONG STORMS.

FOR HIGHS THROUGH THE PERIOD....AROUND 4-7 DEGREES ABOVE NORMAL
WITH VALUES WELL INTO THE 80S FOR THE LONG TERM PERIOD. LOWS
GENERALLY 5-10 DEGREES ABOVE NORMAL SUNDAY NIGHT THROUGH TUESDAY
NIGHT AND A FEW DEGREES ABOVE NORMAL WEDNESDAY NIGHT THROUGH
THURSDAY NIGHT.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
HIGH PRES OFF THE NEW ENGLAND COAST WILL MOVE OUT TO SEA THROUGH
TONIGHT AS A TROUGH OF LOW PRES APPROACHES FROM THE WEST.

VFR WITH BKN CU TODAY. SLY WINDS AROUND 10 KT...OCNL GUSTS 16-19KT
FOR THE CITY TERMINALS AND KISP THIS AFTN. WINDS DIMINISH AFTER
SUNDOWN.

MVFR CONDS LATE NIGHT/EARLY AM SUN...RETURNING TO VFR IN THE LATE
MORNING/EARLY AFTN. SCT SHRA/TSTMS STARTING MID-LATE AFTN MAINLY
FROM CITY TERMINALS AND POINTS N/W.

.OUTLOOK FOR 18Z SUN THROUGH THU...
.SUN-MON NIGHT...MULTIPLE ROUNDS OF -SHRA/TSTMS AND OCNL MVFR.
.TUE-THU...MAINLY VFR.

&&

.MARINE...
SUB-ADVSY CONDS WILL PREVAIL INTO SUN. THERE IS SOME UNCERTAINTY
WITH MIXING OVER THE WATERS SUN AFTN/EVE...WITH THE POTENTIAL FOR A
WINDOW OF SCA GUSTS ON THE OCEAN WATERS. AM NOT CONVINCED THAT THIS
WILL OCCUR AND THINK THE LOW LEVEL LAPSE RATES IN THE NAM OVER THE
WATERS ARE TOO STEEP WHICH IS LEADING TO BETTER MIXING AND SCA
GUSTS. HAVE THEM JUST UNDER 25 KT...BUT WILL RUN WITH OCNL GUSTS UP
TO 25 KT FOR NOW.

SEAS ON THE OCEAN WILL ALSO BUILD IN RESPONSE TO AN INCREASING SW
FLOW. SINCE MARGINAL SCA SEAS ARE EXPECTED TO BEGIN LATE IN THE
THIRD PERIOD...WILL HOLD OFF ON ISSUING HEADLINES...ESPECIALLY SINCE
GUSTS ARE IN QUESTION. SEAS WILL LIKELY CONTINUE THROUGH SUN NIGHT
AND FALL BACK BLO ADVSY LEVELS MON MORNING.

WAVEWATCH INCREASES SEAS BACK TO SCA LEVELS MON NIGHT...BUT THINK
THIS IS OVERDONE CONSIDERING THE WIND FIELD...SO HAVE CAPPED AT 4 FT.
SUB-ADVSY CONDS ARE THEN EXPECTED FOR THE REMAINDER OF THE FORECAST
PERIOD WITH A WEAK PRES GRADIENT OVER THE WATERS.

&&

.HYDROLOGY...
DEEP MOISTURE IN PLACE WITH TROF APPROACHING SUNDAY AND INTO THE
REGION SUNDAY NIGHT AND MONDAY...SO ANY SHOWERS AND THUNDERSTORMS
WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY DOWNPOURS. LOCALIZED
FLOODING THREAT WILL REMAIN WHICH WOULD VARY FROM MINOR AND POOR
DRAINAGE TO POSSIBLY FLASH FLOODING.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...DW
NEAR TERM...DW/PW
SHORT TERM...DW
LONG TERM...JM/DW
AVIATION...JC
MARINE...24/PW
HYDROLOGY...DW






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