Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 010840 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 440 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/... DEEP UPPER TROUGH CONTINUES TO ROTATE IN CANADA WITH A SURFACE HIGH PRESSURE AREA ANCHORED TO THE EAST. A SHORTWAVE WILL RIDE NORTH ALONG THE EASTERN SIDE OF THE UPPER TROUGH TODAY WHICH WILL SET OFF SOME SHOWERS AND POSSIBLY THUNDERSTORMS. EXPECT THESE WILL STAY NORTH AND WEST OF NYC WHERE MU CAPE RANGES ROM 1500-2000 J/KG EVEN THOUGH THERE IS NOT A LOT OF DEEP LAYER SHEAR. NOT EXPECTING SEVERE STORMS BUT SOME COULD BE STRONG WITH GUSTY WINDS AND LOCALLY HEAVY RAINFALL. WITH THE LIGHT SSW WINDS THROUGH THE LAYER...IT IS POSSIBLE THESE STORMS WILL MOVE SLOWLY AND TRAIN OVER THE SAME AREAS. KEPT A SLIGHT CHANCE OF POPS OVER LONG ISLAND AND SOUTHERN CT BUT CONFIDENCE IS LOW WE ACTUALLY SEE ANY SHOWERS OVER THE AREA WITH THE INSTABILITY AND LIFT FOCUSED MORE NORTH AND WEST OF NYC. 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. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... SHOWERS AND THUNDERSTORMS NORTH AND WEST OF NYC WILL LIKELY DIMINISH IN COVERAGE AFTER SUNSET WITH WANING INSTABILITY AND THE SHORTWAVE PASSING TO THE NORTH. NEXT FOCUS OF RAIN WILL BE THE COLD 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. && .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 /09Z FRIDAY THROUGH TUESDAY/... HIGH PRESSURE WILL REMAIN OFFSHORE TODAY...WHILE A WEAK FRONT AND WAVE APPROACH FROM THE SE LATE TONIGHT. MAINLY VFR THROUGH THE 24 HR TAF PERIOD...EXCEPT FOR MVFR STRATUS ACROSS EASTERN TERMINALS THROUGH AROUND 14Z. SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON INTO THE EARLY EVENING...MAINLY N&W OF NYC TERMINALS. ELSEWHERE LOW PROB OF AN ISOLATED SHRA/TSRA. WIND INCREASES OUT OF THE S/SE THIS AFTERNOON...WITH SEABREEZE DEVELOPMENT EXPECTED AT COASTAL TERMINALS AND LIKELY AT KEWR/KTEB. INCREASING CLOUDINESS WITH POTENTIAL FOR MVFR CONDS IN SHRA ACTIVITY LATE TONIGHT INTO SAT MORNING...PARTICULARLY FOR EASTERN TERMINALS. ...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 IN 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 06Z SATURDAY THROUGH TUESDAY... .SATURDAY-SAT NIGHT...SHRA LIKELY...MVFR OR LOWER CONDS POSSIBLE. 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. && .MARINE... WITH A WEAK PRESSURE GRADIENT OVER THE WATERS...SUB-SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED ON THE WATERS THROUGH TUESDAY. && .HYDROLOGY... LOCALLY HEAVY DOWNPOURS EXPECTED IN SCATTERED THUNDERSTORMS TODAY...MOSTLY NORTH AND WEST OF NYC. LOCALIZED URBAN/POOR DRAINING FLOODING IS POSSIBLE. 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. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...JC/LN NEAR TERM...LN SHORT TERM...LN LONG TERM...JC AVIATION...NV MARINE...JC/LN/PW HYDROLOGY...JC/LN

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