Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 300836 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 436 AM EDT SAT AUG 30 2014 .SYNOPSIS... HIGH PRESSURE ALONG THE NEW ENGLAND COAST THIS MORNING 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 WORK EAST OF THE AREA TODAY 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. GENERALLY LOOKING FOR MOSTLY SUNNY SKIES BUT THERE COULD BE A PERIOD OF STRATA CU DEVELOPMENT ALONG THE COAST THIS MORNING WITH SKIES BECOMING PARTLY CLOUDY FOR A TIME. HIGH TEMPS WILL BE JUST BELOW NORMAL WITH READINGS IN THE MID TO UPPER 70S. LOW RISK OF RIP CURRENTS THIS MORNING THEN INCREASING SOUTHERLY FLOW WILL RESULT IN A MODERATE RISK BY AFT/EVE. && .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 /08Z SATURDAY THROUGH WEDNESDAY/... HIGH PRES OFF THE NEW ENGLAND COAST WILL MOVE OUT TO SEA THROUGH TONIGHT AS A TROUGH OF LOW PRES APPROACHES FROM THE WEST. TOUGH FORECAST INTO THE MORNING. MVFR CONDS ARE POSSIBLE...BUT SOME OF THE MODEL GUIDANCE IS NOT INDICATING THIS. HAVE MAINTAINED THE FEW-SCT MENTION OF LOW CLOUDS WITH THE EXCEPTION OF KISP FOR NOW WHERE A TEMPO HAS BEEN ADDED BETWEEN 12Z AND 15Z. 09Z TAFS WILL ADDRESS FURTHER...BUT 06Z OBS CAME IN WITH FEW-SCT CLOUDS AROUND 3K FT (BKN AT KJFK) SO MAY NEED TO AMEND SOONER. HAVE ALSO MAINTAINED TEMPO FOR MVFR VIS AT KGON/KSWF AFT 08Z. S WINDS INCREASE AFT 12Z. GUSTS UP TO 20KT POSSIBLE AFT 16Z...BUT NOT CONFIDENT ON THIS JUST YET. WILL ALSO ADDRESS FURTHER IN 09Z TAFS. MVFR CIGS/BR POSSIBLE AGAIN TONIGHT...BUT PCPN SHOULD HOLD OFF TILL SUNDAY MORNING. .OUTLOOK FOR 06Z SUN THROUGH THU... .SAT NIGHT-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 SHORT TERM...DW LONG TERM...JM/DW AVIATION...24 MARINE...24 HYDROLOGY...DW

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