Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 011454 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1054 AM EDT FRI AUG 1 2014 .SYNOPSIS... HIGH PRESSURE REMAINS JUST OFFSHORE THROUGH SATURDAY AS A FRONTAL BOUNDARY OVER THE ATLANTIC COAST AND LOW PRESSURE TO THE SOUTH WILL IMPACT THE AREA THROUGH THE BEGINNING OF THE WEEK. HIGH PRESSURE THEN BUILDS INTO THE REGION ON TUESDAY...WITH A COLD FRONT PASSING THROUGH ON WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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TRENDED POPS BACK A BIT FOR THE REMAINDER OF THE MORNING INTO THE FIRST HALF OF THE AFTN. PLENTY OF INSTABILITY ALREADY FORMING AS INDICATED ON THE 14Z LAPS...WITH SOME AREAS ALREADY 500-1000 J/KG. HOWEVER...SOUNDINGS SHOWING SOME DRIER AIR STILL NEEDING TO BE OVERCOMES...COMBINED WITH THE LACK OF SFC LIFT AT THIS TIME. THINKING MAINLY DRY THROUGH 18Z...WITH AN ISO SHOWERS MAYBE INTERIOR AREAS. BY THIS AFTN...COULD SEE A SHORTWAVE PASSING COMBINING WITH DEVELOPED SEA BREEZES TRIGGERING ISO-SCT SHOWERS AND TSTMS. KEPT THE CHC POPS NYC METRO NORTH AND WEST...WITH LOW END SLIGHT CHC ELSEWHERE. BETTER CHC FOR PCPN WILL BE THIS EVENING/OVERNIGHT. NAM/MET GUIDANCE HAD A BETTER HANDLE ON THE SW FLOW WARMING INTERIOR AREAS SLIGHTLY MORE THAN COASTAL LOCATIONS. 13-14C 850 TEMPS LEND TO HIGHS IN THE LOWER 80S WHICH MATCHED WELL WITH GUIDANCE AND LEANED TOWARDS THE NAM NUMBERS. TEMPS ON TRACK FOR THE DAY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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NEXT FOCUS OF RAIN WILL BE THE STATIONARY FRONT BACKING IN FROM THE EAST WITH THE WESTERN ATLANTIC HIGH PRESSURE EXPANDING SLIGHTLY WESTWARD. SOME MODEL DIFFERENCES EXIST ON THE TIMING OF WHEN THE PRECIP WILL REACH THE AREA WITH THE NAM THE SLOWEST AND DRIEST FOR THE DAY ON SATURDAY. HIGHEST PRECIP AMOUNTS WILL BE LONG ISLAND AND SOUTHEAST CT WITH THE FRONT POSITIONED JUST TO THE SOUTH OF THE ISLAND. WILL CONTINUE CHANCE POPS ELSEWHERE THOUGH AS SHOWERS SHOULD STILL BE ABLE TO DEVELOP WITH UPPER JET AND MID LEVEL SHORTWAVE ENHANCEMENT. AS WELL...DEEP MOISTURE STREAMING FROM THE SOUTH WILL BE IN PLACE SO ANY SHOWERS WILL PRODUCE LOCALLY HEAVY RAINFALL. VERY LOW CONFIDENCE ON ANY THUNDER FOR SATURDAY. LITTLE TO NO INSTABILITY OR SHEAR...JUST MODERATE LIFT. EXPECT SHOWERS TO BE VERY TROPICAL IN NATURE AND MAYBE AN ISOLATED LIGHTNING STRIKE OR TWO. WIND PROFILES ALOFT ARE AGAIN LIGHT SO TRAINING OF CELLS IS LIKELY. AS FOR TEMPERATURES...NAM 2M TEMPS MUCH WARMER THAN ALL GUIDANCE FOR LOWS TONIGHT EVEN WITH SIMILAR CLOUD COVER FORECASTS. WENT WITH A BLEND OF MAV/MOSGUIDE FOR LOWS FOR TEMPS IN THE LOWER TO MID 60S. GUIDANCE FOR HIGHS ON SAT IS LOWER THAN PREVIOUS. POSSIBLY DUE TO THE MODELS COMING INTO AGREEMENT FOR A RAINY DAY. WILL LOWER HIGHS A FEW DEG FROM PREVIOUS FORECAST.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... A SHORTWAVE WEAKENS AT THE BASE OF A 500MB TROUGH AXIS AS IT APPROACHES THE FORECAST AREA...EVENTUALLY PASSING THROUGH SUNDAY NIGHT INTO MONDAY MORNING. THIS WILL HELP SLOWLY NUDGE THE OFFSHORE FRONTAL BOUNDARY FARTHER OUT TO SEA. SOME SYNOPTIC LIFT WILL BE PRESENT THROUGH MONDAY WITH THE RIGHT ENTRANCE OF AN UPPER JET STREAK IN THE VICINITY. LESS CERTAIN ARE THE TIMING AND POSITION OF LOW-MID LEVEL SHORTWAVES THAT PASS THROUGH/NEARBY THE CWA BEFORE THE TROUGH AXIS ALOFT PASSES THROUGH. POPS THEREFORE CAPPED AT CHANCE...WHICH IS CLOSE TO WHAT A MODEL BLEND WOULD PRODUCE. BEST OVERALL CHANCES OF RAINFALL WOULD BE SATURDAY NIGHT INTO SUNDAY MORNING AND CLOSER THE OFFSHORE FRONTAL BOUNDARY. MONDAY COULD EVEN TURN OUT TO BE COMPLETELY DRY...ESPECIALLY IF THE ECMWF IS CORRECT WITH THE TROUGH AXIS PASSING THROUGH SUNDAY NIGHT AND A LACK OF LOW-MID LEVEL SHORTWAVES TRAILING IT ON MONDAY. DO NOT HAVE ENOUGH CONFIDENCE TO REMOVE POPS ALTOGETHER ON MONDAY...SO HAVE LEFT THE PREVIOUS FORECAST OF SLIGHT CHC/CHC POPS. WEAK HIGH PRESSURE PROBABLY KEEPS TUESDAY AND THURSDAY DRY...BUT A COLD FRONT AND CYCLONIC FLOW ALOFT COULD BRING AN ISOLATED SHOWER/TSTM TO THE AREA ON WEDNESDAY. CLOUDS AND AN ONSHORE FLOW WILL HOLD HIGH TEMPERATURES ON MONDAY BELOW NORMAL...HIGHS OTHERWISE NEAR NORMAL FOR THE REST OF THE LONG TERM FORECAST. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/...
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HIGH PRESSURE WILL REMAIN OFFSHORE TODAY...WHILE A FRONTAL WAVE APPROACHES FROM THE S LATE TONIGHT. MAINLY VFR THROUGH 00Z. WHILE THE AIRMASS ACROSS THE REGION IS MODERATELY UNSTABLE...THERE ARE REALLY NO FOCUSING MECHANISMS OUTSIDE OF THE SEABREEZE. AN ISOLATED SHOWER/THUNDERSTORM IS POSSIBLE THIS MORNING/EARLY AFT ALONG THE SEABREEZE...BUT MORE LIKELY ACROSS LOCATIONS NORTH AND WEST OF THE NYC METRO TERMINALS WHERE INSTABILITY WILL BE THE GREATEST. LATEST CCFP LOOKS REASONABLE. WIND INCREASE OUT OF THE S/SE THIS AFTERNOON...WITH SEABREEZE DEVELOPMENT EXPECTED AT COASTAL TERMINALS AND LIKELY MOVING INLAND OF KEWR/KTEB IN AFT. INCREASING POTENTIAL FOR MVFR CONDS IN SHRA ACTIVITY AFTER MIDNIGHT INTO SAT MORNING. 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: S SEABREEZE DEVELOPMENT EXPECTED BY 17-18Z. KLGA FCSTER COMMENTS: S SEABREEZE DEVELOPMENT EXPECTED BY 18-19Z. KEWR FCSTER COMMENTS: SE SEABREEZE DEVELOPMENT LIKELY BY 18-19Z. LOW CONFIDENCE WHETHER SPARSE COVERAGE OF TSTMS BTWN 17Z AND 19Z WILL AFFECT TERMINAL. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: SSE SEABREEZE DEVELOPMENT LIKELY BY 18-20Z. LOW CONFIDENCE IN WHETHER SPARSE COVERAGE OF TSTMS BTWN 17Z AND 20Z WILL AFFECT TERMINAL. KHPN FCSTER COMMENTS: LOW CONFIDENCE IN WHETHER SPARSE COVERAGE OF TSTMS BTWN 17Z AND 19Z WILL AFFECT TERMINAL. KISP FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. .OUTLOOK FOR 12Z SATURDAY THROUGH TUESDAY... .SATURDAY-SAT NIGHT...SHRA WITH MVFR OR LOWER CONDS LIKELY. LOW PROB FOR TSRA. .SUN-SUN NIGHT...SHRA/TSRA POSSIBLE...MVFR OR LOWER CONDS POSSIBLE. .MONDAY-TUESDAY...VFR. MVFR POSSIBLE IN ISOLD SHRA/TSTMS IN THE AFTERNOON/EVENING.
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&& .MARINE... WITH A WEAK PRESSURE GRADIENT OVER THE WATERS...SUB-SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED ON THE WATERS THROUGH TUESDAY. && .HYDROLOGY...
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BRIEF HEAVY DOWNPOURS POSSIBLE IN SCATTERED SHOWERS AND THUNDERSTORMS TODAY...MOSTLY NORTH AND WEST OF NYC. LOCALIZED URBAN/POOR DRAINING FLOODING IS POSSIBLE DUE TO SLOW MOVEMENT. A SIMILAR SET UP EXISTS FOR THE WEEKEND INTO MONDAY WITH SHOWERS MORE NUMEROUS IN COVERAGE ACROSS THE AREA AND SLOW MOVEMENT OF CELLS. ALTHOUGH THUNDERSTORMS ARE UNLIKELY...THE MOIST AIRMASS WILL PRODUCE MODERATE TO HEAVY DOWNPOURS. THIS COULD ONCE AGAIN RESULT MAINLY IN URBAN/POOR DRAINAGE FLOODING.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...JC/LN NEAR TERM...LN/SEARS SHORT TERM...LN LONG TERM...JC AVIATION...DW MARINE...JC/LN/PW HYDROLOGY...JC/LN

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