Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 011739 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 139 PM EDT MON SEP 1 2014 .SYNOPSIS... A SURFACE TROUGH OVER THE AREA THIS AFTERNOON DISSIPATES AS IT SHIFTS EAST TONIGHT. A COLD FRONT WILL APPROACH THE AREA ON TUESDAY AND MOVES THROUGH TUESDAY NIGHT...WITH HIGH PRESSURE BUILDING IN FOR THE LATTER HALF OF THE WEEK. ANOTHER COLD FRONT WILL IMPACT THE REGION THIS WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MINOR CHANGES MADE WITH THIS UPDATE...MAINLY WITH CLOUD COVER AND HOURLY TEMPS. A SHORTWAVE PASSING TO OUR SOUTH DURING THE FIST HALF OF THIS AFTERNOON SHOULD PROVIDE SOME LIFT FOR AT LEAST THE SOUTHERN ZONES...BUT HAS NOT RESULTED MUCH IN THE WAY OF SHOWERS SO FAR. BUT MEANWHILE...WE CONTINUE TO DESTABILIZE WITH DAYTIME HEATING AND HIGH DEWPOINTS. MODERATE CAPE IN A LOW SHEAR ENVIRONMENT SHOULD RESULT IN SCT PULSE STORMS THIS AFTN. COULD BE A FEW STRONGER STORMS...ALTHOUGH DUE TO THE WEAK SHEAR NOT EXPECTING SEVERE. MORE IMPORTANTLY...PWATS WILL REMAIN AROUND 2 INCHES AND STORMS WILL BE MOVING SLOWER THAN YESTERDAY SO AN ISOLD FLASH FLOOD THREAT REMAINS...MAINLY IN URBANIZED AREAS. NOT WIDESPREAD ENOUGH FOR A WATCH HOWEVER. LOOKS LIKE WIDESPREAD HEAT INDICES FALL JUST SHORT OF 95 IN THE CITY THIS AFTN. THIS WILL NEED TO BE TAKEN INTO CONSIDERATION FOR A POTENTIAL ADVISORY. THE UNCERTAINTY OF CLOUD COVER THIS AFTN AND CONSEQUENTIAL HIGH TEMPS...PLUS MARGINAL CRITERIA INDICES FOR TOMORROW COMPLICATE THE FORECAST. THERE IS A MODERATE RISK OF RIP CURRENTS TODAY...DUE TO COMBINED 3 TO 5 FT SOUTHERLY WIND WAVES AND A BACKGROUND SE SWELL. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... SHRA/TSTMS DIMINISH AND SHIFT EWD DURING THE EVENING AS THE ATMOSPHERE STABILIZES AND MOISTURE CONVERGENCE AND LIFT MOVE EAST. THE HEAT AND HUMIDITY WILL CONTINUE THROUGH TUE WITH H85 TEMPS REMAINING AROUND 17-18C AND MIXING TO THIS HEIGHT. CLOUD COVER WILL INCREASE DURING THE AFTN AS A COLD FRONT APPROACHES FROM THE W...BUT WE SHOULD STILL MAX OUT IN THE UPPER 80S TO LOWER 90S ACROSS A GOOD PORTION OF THE FORECAST AREA. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... PCPN CHANCES DISSIPATE QUICKLY TUESDAY NIGHT AS AN UPPER LEVEL TROUGH SWINGS THROUGH THE NORTHEAST...WHILE THE SURFACE LOW LIFTS NORTH...DRAGGING ITS ASSOCIATED COLD FRONT THROUGH. GENERAL AGREEMENT BETWEEN THE 00Z MODEL SOLUTIONS WITH THE FRONT MOVING THROUGH BETWEEN 00-06Z. ALOFT...THE BETTER FORCING WITH THE SHORTWAVE LOOKS TO REMAIN WELL NORTH OF THE REGION...WITH ONLY A WEAK SHORTWAVE PASSING THROUGH DURING THE 00-06Z TIMEFRAME. AS SUCH...WILL CAP POPS AT HIGHER END CHC THROUGH 03Z OVER AREAS NORTH/WEST NYC METRO...THEN TAPER OFF WITH ALL AREAS BCMG DRY BY 06Z. LINGERING INSTABILITY UP TO 1000 J/KG COULD SEE AN ISO TSTM STILL PSBL TUES EVENING RIGHT AHEAD OF THE FRONT. HIGH PRESSURE QUICKLY BUILDS IN AT THE SURFACE WHILE A SEMI-ZONAL FLOW TAKES HOLD BRIEFLY ALOFT. BY WEDNESDAY SEEING DRYING CONDITIONS AS THE HIGH DEEPENS AND RIDGING BUILDS ACROSS THE EASTERN HALF OF THE US. NO PCPN EXPECTED WED-FRI UNDER SUCH A PATTERN. A QUICK SHOT OF COOLER AIR WED IN THE WAKE OF THE FRONT WITH THE NORTHERLY FLOW WILL PUSH TEMPS BACK A FEW DEGREES...THOUGH STILL REMAINING WELL ABOVE NORMAL. RISING HEIGHTS WITH THE BUILDING RIDGE WILL INCREASE TEMPS ONCE AGAIN BY WEEKS END...ESP WITH A STRONGER SURGE OF WARMER AIR WITH THE SOUTHERLY FLOW SETTING UP AHEAD OF THE NEXT APPROACHING COLD FRONT. 00Z GFS/CMC BEGIN APPROACHING THE COLD FRONT LATE FRIDAY...BRINGING IT THROUGH BY SAT MORNING WHILE THE ECMWF REMAINS THE SLOWER SOLUTION...MOVING THE FRONT THROUGH LATE SAT. QUESTION REMAINS TO WHAT EXTENT THE RIDGE BUILDS...WITH THE GFS/CMC ACTUALLY SIDING CLOSER TO MORE ZONAL FLOW WHILE THE ECMWF HAS A MORE PRONOUNCED RIDGE WHICH IN TURN TAKE LONGER TO WEAKEN. FOR NOW...SIDED MORE WITH THE ECMWF SOLUTION FOR TIMING...THOUGH EVEN THAT COULD BE A BIT SLOW AND RIDGING OVERDONE...WITH A GOOD COMPROMISE BEING SWINGING THE FRONT THROUGH SOMETIME SATURDAY. WITH THE UNCERTAINTY TOPPED POPS AT CHC DURING THE DAY SAT...AND INTO THE FIRST HALF OF SUNDAY NIGHT. BOTH THE GFS AND ECMWF HINT AT THE FRONT LINGERING JUST OFFSHORE DURING THE DAY SUNDAY...AND THE ECMWF EVEN ON INTO MONDAY. WILL MAINTAIN SLIGHT CHC POPS FOR SUNDAY MORNING TO ACCOUNT FOR THE FRONTAL PLACEMENT. TEMPS QUICKLY REBOUND TO NEAR NORMAL TO SLIGHTLY BELOW BY SUNDAY AS WELL WITH THE TROUGH USHERING IN MUCH COOLER TEMPS ALOFT. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... A SURFACE TROUGH WILL WEAKEN AS IT MOVES EAST TONIGHT. A COLD FRONT APPROACHES LATE TUESDAY. SHOWERS AND THUNDERSTORMS ARE DEVELOPING...AND WILL BE SCATTERED ACROSS THE AREA THROUGH 22-23Z. OTHERWISE...VFR THIS AFTERNOON WITH BROKEN CU. BY TONIGHT...PATCHY STRATUS AND FOG IS EXPECTED...ESPECIALLY LATER ON AT NIGHT. MVFR OR IFR POSSIBLE...ESPECIALLY OUTSIDE OF NYC METRO TERMINALS. VFR TUESDAY MORNING AS ANY MORNING STRATUS AND FOG BURNS OFF. SOUTH TO SOUTHWEST WINDS AROUND 10 KT THIS AFTERNOON LIGHTEN TONIGHT. SOUTHWEST WIND PERSISTS TUESDAY MORNING...GENERALLY UNDER 10 KTS. 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: AMENDMENTS FOR SCATTERED SHOWERS/ THUNDERSTORMS POSSIBLE THROUGH 22Z OR SO. KLGA FCSTER COMMENTS: AMENDMENTS FOR SCATTERED SHOWERS/ THUNDERSTORMS POSSIBLE THROUGH 22Z OR SO. KEWR FCSTER COMMENTS: WINDS ARE EXPECTED TO REMAIN SOUTH TO SOUTHWEST. HOWEVER...SOUTHEAST SEA BREEZE WILL APPROACH THE AIRPORT AND WILL NEED TO BE WATCHED AFTER 18-20Z. AMENDMENTS FOR SCATTERED SHOWERS/THUNDERSTORMS POSSIBLE THROUGH 22Z OR SO. KTEB FCSTER COMMENTS: AMENDMENTS FOR SCATTERED SHOWERS/ THUNDERSTORMS POSSIBLE THROUGH 22Z OR SO. KHPN FCSTER COMMENTS: AMENDMENTS FOR SCATTERED SHOWERS/ THUNDERSTORMS POSSIBLE THROUGH 22Z OR SO. KISP FCSTER COMMENTS: AMENDMENTS FOR SCATTERED SHOWERS/ THUNDERSTORMS POSSIBLE THROUGH 22Z OR SO. .OUTLOOK FOR 18Z TUE THROUGH FRI... .TUE AFTERNOON-TUE NIGHT...MAINLY VFR EXCEPT FOR SCATTERED LATE AFTERNOON AND EVENING SHRA/TSRA. .WED-FRI NIGHT...VFR CONDITIONS ARE EXPECTED. .SAT...SUB VFR POSSIBLE IN SCATTERED SHRA/TSRA. && .MARINE... GENERALLY SUB-SCA CONDITIONS THEN EXPECTED ON THE WATERS THROUGH FRIDAY UNDER THE HIGH PRESSURE. AN OCCASIONAL GUST TO 25 KTS MIGHT BE POSSIBLE ON THE OCEAN WATERS TUES EVENING RIGHT AHEAD OF THE COLD FRONTAL PASSAGE. WINDS INCREASE AHEAD OF THE NEXT FRONT LATE FRIDAY INTO SATURDAY...WITH POSSIBLE GUSTS REACHING 25 KTS DURING THIS TIME. WAVES/SEAS WILL BUILD IN RESPONSE TO INCREASING WINDS...THOUGH AT THE MOMENT EXPECTING SEA CONDITIONS TO REMAIN SUB-SCA. WAVEWATCH WAS QUICK TO BUILD THE SEAS...SIDING WITH THE QUICKER GFS SOLUTION...SO DROPPED GUIDANCE AROUND 1 FT FOR FRI NIGHT/SAT TO REFLECT A SLOWER SOLUTION. && .HYDROLOGY... BASIN AVERAGE RAINFALL IS EXPECTED TO BE AROUND 1/4 INCH TODAY. DUE TO THE CONVECTIVE NATURE OF THE RAINFALL DISTRIBUTION...THERE WILL BE AREAS THAT RECEIVE LITTLE TO NO RAINFALL...AND SOME AREAS THAT COULD SEE OVER AN INCH. MAINLY A MINOR URBAN AND POOR DRAINAGE FLOOD THREAT TODAY...ALTHOUGH ISOLD FLASH FLOODING IS POSSIBLE WITH A WATER LOADED ATMOSPHERE. NO SIGNIFICANT PRECIPITATION RESULTING IN HYDROLOGIC ISSUES IS CURRENTLY FORECASTED WED THROUGH THIS WEEKEND. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$

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