Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 301647 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1247 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/...
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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.
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&& .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 SCT TO BKN CU TODAY. SLY WINDS INCREASE LATE THIS MORNING INTO AFTN WITH OCNL GUSTS UP TO 20KT POSSIBLE AFT 19Z. MVFR CIGS/BR POSSIBLE TONIGHT...BUT PCPN SHOULD HOLD OFF UNTIL AFT 12Z SUN. .OUTLOOK FOR 12Z SUN THROUGH THU... .SUN-TUE NIGHT...MAINLY MVFR CIGS AND VSBY WITH MULTIPLE ROUNDS OF SHOWERS AND TSTMS STARTING DURING THE DAY SUNDAY. .WED-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/24 MARINE...24/PW HYDROLOGY...DW

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