Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 220049 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 849 PM EDT THU AUG 21 2014 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE PUSHES THROUGH THE NORTHEAST INTO THE WEEKEND...EVENTUALLY PUSHING SOUTH ON SATURDAY AS HIGH PRESSURE BUILDS DOWN FROM EASTERN CANADA. THIS HIGH WILL REMAIN NEARLY STATIONARY OVER THE NORTHEAST INTO TUESDAY...THEN WILL SHIFT SOUTH OF THE AREA AND SLIDE OFFSHORE THROUGH THURSDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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SHOWERS AND THUNDERSTORMS N AND W OF NYC ASSOCIATED WITH AN UPPER LEVEL TROUGH PIVOTING THROUGH THE NORTHEAST WILL BE WINDING DOWN OVER THE NEXT FEW HOURS DUE TO THE LOSS OF HEATING. 23Z LAPS DATA INDICATES A MORE STABLE AIRMASS IN NORTHEAST NJ SO EXPECT STORMS TO WEAKEN. HAVE ADJUSTED POPS AND WEATHER GRIDS THROUGH MIDNIGHT BASED ON LATEST RADAR DATA AND TRENDS. THERE IS LOWER CONFIDENCE IN POPS ACROSS EASTERN LI AND SE CT WITH THE STORMS WEAKENING IN THE MORE STABLE ATMOSPHERE. BECAUSE OF THIS...CAPPED POPS AT CHC FOR THE SECOND HALF OF THE NIGHT...AND DID NOT INCLUDE THUNDER AFTER 03Z. TEMPS RIGHT AROUND NORMAL TONIGHT WITH THE CLOUD COVER AND POTENTIAL FOR PCPN OVERNIGHT. USED A BLEND OF MET/MAV GUIDANCE.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... THE REGION REMAINS POSITIONED UNDER THE DEEPENING TROUGH ALONG THE EASTERN SEABOARD AS RIDGING ALOFT STRENGTHENS ACROSS THE CENTRAL US. AT THE SURFACE...LOW PRESSURE RIDES A NEARLY STATIONARY FRONT WELL SOUTH OF THE AREA...WITH HIGH PRESSURE DIPPING SOUTH FROM SOUTHEASTERN CANADA. SOME MODEL DISCREPANCY ON THE EXTENT OF PCPN DEVELOPMENT DURING THE DAY AND EXACTLY WHERE IT FORMS. ONCE AGAIN...HIGHER CONFIDENCE OF DEVELOPMENT OVER WESTERN AREAS WHERE A SHORTWAVE IS EXPECTED TO MOVE THROUGH AS IT ROUNDS THE TROUGH...SO MAINTAINING THE HIGHER CHC POPS THERE...WITH SLIGHT CHC OVER EASTERN AREAS WITH THE THINKING THAT THE PERSISTENT EASTERLY FLOW WILL WORK TO STABILIZE THE ATMO AND MINIMIZING THE CHC FOR SHOWER FORMATION. 12Z MODEL SUITE ALSO SUGGESTS THE STRONGER FORCING WITH ANOTHER SHORTWAVE REMAINING WELL EAST OF THE AREA TOMORROW AFTN INTO TOMORROW EVENING...KEEPING THE BULK OF THAT ASSOCIATED PCPN EAST OF THE AREA. FOR TOMORROW NIGHT...COULD SEE LINGERING SHOWERS MAINLY OVER WESTERN AREAS...CLEARING BY 06Z AS HIGH PRESSURE AT THE SURFACE NUDGES SOUTH. PATCHY FOG ALSO POSSIBLE WITH PLENTY OF MOISTURE BEING INJECTED IN THE LOWER LEVELS BY THE EASTERLY FLOW. TEMPS ON THE COOLER SIDE AGAIN WITH THE ONSHORE FLOW DURING THE DAY FRIDAY AS WELL INTO FRIDAY NIGHT. THERE IS A MODERATE RISK FOR RIP CURRENT DEVELOPMENT ALONG THE ATLANTIC OCEAN BEACHES DURING THE DAY FRIDAY. && .LONG TERM /SATURDAY THROUGH THURSDAY/... MODELS ARE IN GOOD AGREEMENT THAT THE H5 PATTERN ACROSS NOAM AT THE START OF THE LONG TERM PERIOD WILL CONSIST OF AN AMPLIFYING RIDGE EXTENDING FROM SOUTH CENTRAL CANADA THROUGH THE SE CONUS WITH A CUTOFF LOW OVER THE WESTERN US A SLOWLY WEAKENING BLOCKING PATTERN OVER EASTERN CANADA AND THE NORTHEAST. THE ANOMALOUSLY STRONG RIDGE OVER QUEBEC WILL GRADUALLY BREAK DOWN AND MERGE WITH THE AFOREMENTIONED RIDGE OVER THE US. THIS WILL RESULT IN A DIGGING TROUGH EAST OF NEW ENGLAND. SOME UNCERTAINTY WITH THE SPECIFIC DETAILS AND TIMING OF VORT ENERGY TRACKING THROUGH NEW ENGLAND ON SAT...BUT THE TROUGH AXIS SHOULD MOVE THROUGH SAT NIGHT. HAVE KEPT THE MAJORITY OF SAT DRY WITH JUST A SCHC OF SHOWERS EARLY. THERE COULD BE A FEW ADDITIONAL SHOWERS DURING THE AFTN IF THERE ARE ANY WEAKNESSES ALOFT...BUT CANNOT PINPOINT WHERE AND WHEN AT THIS POINT. MAY NEED TO ADD SLIGHT TO LOW CHC POPS IN SUBSEQUENT FORECAST PACKAGES TO ACCOUNT FOR THESE TIMING DIFFERENCES. ADDITIONALLY...THE AMOUNT OF CLOUD COVER ON SAT IS ALSO QUESTIONABLE AS A RESULT. OTHERWISE...EXPECT DRY SEASONABLE CONDS THROUGH THE MIDDLE OF NEXT WEEK AS HEIGHTS RISE ONCE THE TROUGH DEPARTS. SFC HIGH PRES WILL BUILD INTO THE NORTHEAST OVER THE WEEKEND AND REMAIN NEARLY STATIONARY INTO TUE. THIS WILL RESULT IN AN ELY FLOW CONTRIBUTING TO BELOW NORMAL TEMPERATURES THOUGH THIS TIME...BUT WITH HEIGHTS RISING TUE THROUGH THU...TEMPERATURES WILL REBOUND TO NEAR NORMAL LEVELS. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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WEAK LOW PRESSURE MOVES THROUGH THE AREA OVERNIGHT AND OFF THE DELMARVA FRIDAY MORNING. HIGH PRESSURE BUILDS FROM THE NORTHEAST DURING FRIDAY. SCATTERED THUNDERSTORMS AND SHOWERS MAY IMPACT THE TERMINALS MAINLY NORTH OF NYC. THERE IS A CHANCE OF THE THUNDERSTORMS MOVING INTO THE NYC TERMINALS HOWEVER THE STORMS WILL BE WEAKENING. MARGINAL VFR CEILINGS WILL BE LIKELY...MAINLY ALONG THE COAST...WITH A CHANCE OF MARGINAL VFR VISIBILITIES IN FOG. THERE WILL BE SOME IMPROVEMENT AFTER 14Z WITH VFR VISIBILITIES AND CEILINGS POSSIBLY LIFTING TO VFR. SOUTHEAST WIND 5 TO 10 KT WILL GRADUALLY BACK TO THE EAST AFTER 06Z AND REMAIN EAST TO NORTHEAST THROUGH FRIDAY. NY METRO ENHANCED AVIATION WEATHER SUPPORT... DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS CAN BE FOUND AT: HTTP:/WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE) KJFK FCSTER COMMENTS: A THUNDERSTORM COULD APPROACH THE TERMINAL AROUND 03Z. MARGINAL VFR CEILINGS DEVELOPING 02Z TO 03Z. IMPROVEMENT TO VFR AROUND 14Z...HOWEVER THERE IS A CHANCE MVFR CEILINGS REMAIN THROUGH THE DAY. KLGA FCSTER COMMENTS: A THUNDERSTORM COULD APPROACH THE TERMINAL AROUND 03Z. MARGINAL VFR CEILINGS DEVELOPING 02Z TO 03Z. IMPROVEMENT TO VFR AROUND 14Z. LOW CHANCE OF MVFR THROUGH THE DAY. KEWR FCSTER COMMENTS: A THUNDERSTORM COULD APPROACH THE TERMINAL 02Z TO 03Z. THERE IS A CHANCE OF MARGINAL VFR CEILINGS OVERNIGHT AND INTO EARLY FRIDAY MORNING...TIL 13Z. KTEB FCSTER COMMENTS: A THUNDERSTORM COULD APPROACH THE TERMINAL 02Z TO 03Z. THERE IS A CHANCE OF MARGINAL VFR CEILINGS OVERNIGHT AND INTO EARLY FRIDAY MORNING...TIL 13Z. KHPN FCSTER COMMENTS: A THUNDERSTORM COULD APPROACH THE TERMINAL 01Z TO 02Z. MARGINAL VFR CEILINGS DEVELOP OVERNIGHT AND LIKELY REMAIN THROUGH THE DAY FRIDAY...CEILINGS 1500 TO 2500 FT. KISP FCSTER COMMENTS: MARGINAL VFR CEILINGS 1500 TO 2500 FT LIKELY REMAIN INTO FRIDAY AFTERNOON AROUND 19Z WHEN CEILINGS LIFT TO VFR. THERE IS A CHANCE OF MARGINAL VFR FOG UNTIL 14Z. .OUTLOOK FOR 00Z SAT THROUGH TUE... .FRI NIGHT-SAT...MARGINAL VFR CEILINGS AND POSSIBLY VISIBILITIES IN FOG INTO SATURDAY MORNING...THEN IMPROVING TO VFR. SAT NIGHT-TUE...VFR.
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&& .MARINE... GENERALLY SUB-SCA CONDITIONS ON THE WATERS THROUGH FRIDAY NIGHT WITH HIGH PRESSURE BUILDING SOUTH AND LOW PRESSURE REMAINING WELL SOUTH OF THE WATERS. SCA FOR SEAS WILL BE POSSIBLE ON THE OCEAN WATERS SAT WITH A MODERATE ELY FLOW. CURRENT FORECAST KEEPS SEAS JUST BLO SCA LEVELS...BUT THERE IS THE POTENTIAL FOR THEM TO BE A FOOT OR SO HIGHER. SUB-ADVSY CONDS EXPECTED THEREAFTER AS THE PRES GRADIENT WEAKENS WITH HIGH PRES BUILDING OVER THE NORTHEAST. && .HYDROLOGY...
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SHOWERS WITH A FEW SLOW MOVING THUNDERSTORMS PRODUCING HEAVY RAINFALL WILL CONTINUE THIS EVENING IN INTERIOR NE NJ AND POSSIBLY INTO NYC. ONLY EXPECT MINOR URBAN AND POOR DRAINAGE ISSUES AT MOST. NO SIGNIFICANT RAINFALL IS THEN EXPECTED THROUGH THE MIDDLE OF NEXT WEEK.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$

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