Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 311152 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 752 AM EDT SUN AUG 31 2014 .SYNOPSIS... LOW PRESSURE TRACKING ACROSS EASTERN CANADA WILL SEND A TROUGH ACROSS THE AREA LATE THIS AFTERNOON INTO THIS EVENING. ANOTHER TROUGH WILL THEN WORK ACROSS THE AREA MONDAY AFTERNOON AND EVENING. WEAK HIGH PRESSURE BRIEFLY BUILDS IN MONDAY NIGHT INTO TUESDAY MORNING. A COLD FRONT WILL THEN MOVE THROUGH TUESDAY NIGHT WITH HIGH PRESSURE BUILDING IN FROM THE SOUTH AND WEST THROUGH THURSDAY. THE HIGH MOVES OFFSHORE FRIDAY WITH ANOTHER COLD FRONT APPROACHING INTO THE BEGINNING OF NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... A FEW SHOWERS POPPED UP ACROSS NRN NJ BUT SINCE HAVE DISSIPATED. THIS WILL REMAIN A POSSIBILITY THROUGH THE REMAINDER OF THE MORNING HOURS. OTHERWISE...ONLY MINOR CHANGES MADE TO THE FORECAST TO ACCOUNT FOR CURRENT CONDITIONS. A SIGNIFICANT CHANGE IN THE WEATHER THE LAST 24H AS THE UPPER RIDGE AXIS HAS PASSED TO THE EAST WITH AN INFLUX OF TROPICAL MOISTURE FROM THE GULF COAST STATES. LATEST WATER VAPOR IMAGERY SHOWS THE MOISTURE TRANSPORT FROM THE WESTERN GULF OF MEXICO WITH MULTIPLE SHORT WAVES EMBEDDED IN THE FLOW. THESE LATER TODAY WILL INTERACT WITH A SFC TROF TO PRODUCE WIDESPREAD CONVECTION ACROSS THE NORTHERN MID ATLANTIC AND SOUTHERN NEW ENGLAND STATES. LATEST DAY 1 CONVECTIVE OUTLOOK FROM SPC HAS ALSO INTRODUCED A SLIGHT RISK OF SEVERE WEATHER ACROSS THE NY METRO AREA...FROM NYC AND POINTS NORTH AND WEST WHERE THE GREATEST INSTABILITY AND WIND SHEAR WILL RESIDE. HOWEVER...THE PRIMARY THREAT LOOKS TO BE LOCALIZED HEAVY RAINFALL LATE THIS AFTERNOON TO THE WEST OF NYC...THEN OVERSPREADING THE REST OF THE TRI-STATE AREA THIS EVENING. PW IN EXCESS OF 2 INCHES...MLCAPES OF 1000-1500 J/KG...AND 30-40 KT OF DEEP-LAYERED SHEAR SUPPORTS ORGANIZED CONVECTION WITH POSSIBLE LINE SEGMENTS AND STRONG/DAMAGING WINDS. THERE IS STILL SOME CONCERN FOR THE BOUNDARY TO LAY DOWN OR BECOME NEARLY STATIONARY EAST OF NYC...WITH THE POSSIBILITY OF TRAINING OF CELLS. THE 00Z MODEL GUIDANCE HAS SHOW MORE PROGRESSION THAN 24H AGO THOUGH. IN ADDITION...VERY WARM...MUGGY CONDITIONS WILL PREVAIL WITH HIGHS IN THE LOW TO MID 80S AND DEW POINTS AROUND 70. PREFERRED THE COOLER MAV GUIDANCE DUE TO THE EXPECTED CLOUD COVER TODAY. HOWEVER...SHOULD THERE BE SOME BREAKS THIS AFTERNOON...A FEW DEGREES CAN EASILY BE ADDED TO THESE HIGHS. OVERNIGHT LOWS WILL HAVE A TOUGH TIME GETTING TOO FAR BELOW THE 70 DEGREE MARK WITH CLOUD COVER AND AN ONSHORE FLOW. A MODERATE RISK OF RIP CURRENTS IS EXPECTED TODAY AT THE ATLANTIC FACING BEACHES...BUT THIS MAY INCREASE TO HIGH BY LATE IN THE DAY WITH INCREASING SOUTHERLY WINDS. && .SHORT TERM /MONDAY/... POTENTIAL EXISTS FOR ANOTHER ROUND OF STRONG AFT/EVE CONVECTION ON MON AS ANOTHER TROF SETS UP JUST WEST OF THE AREA AND THEN APPROACHES BY EARLY EVE. THIS TIME AROUND THOUGH WINDS ALOFT ARE NOT AS FAVORABLE FOR ORGANIZED CONVECTION. HOWEVER...MLCAPES OF 1000-1500 J/KG COUPLED WITH PW AROUND 2 INCHES WILL KEEP LOCALIZED HEAVY RAINFALL A THREAT. HIGHS MON ARE FORECAST TO BE A TOUCH WARMER WITH DEW POINTS REMAINING AROUND 70. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... THE DOMINANT PATTERN IN THE LONG TERM IS THAT OF RIDGING ON AVERAGE. ON A LARGE SCALE...AN UPPER LEVEL RIDGE IS APPARENT ON THE MODEL HEIGHT FIELDS ALOFT FROM QUEBEC TO THE MID-ATLANTIC. A RELATIVELY STRONGER UPPER LEVEL TROUGH PASSES NORTH OF THE REGION LATE TUESDAY INTO EARLY WEDNESDAY WITH SOME MORE HEIGHT FALLS AND A TRANSITION TO ZONAL FLOW. RIDGING RESUMES THEREAFTER WITH THE LARGE RIDGE ACROSS THE SOUTHERN U.S. PUSHING NORTH FROM WEDNESDAY THROUGH FRIDAY. AT THE SURFACE...A SURFACE TROUGH MOVING IN FROM THE WEST DISSIPATES WITHIN THE REGION WITHOUT MUCH UPPER LEVEL SUPPORT ON MONDAY. A WEAK PRESSURE GRADIENT IS LEFT IN ITS PLACE WITHOUT A STRONG PRESENCE OF HIGH PRESSURE. THE JET STREAM WILL BE LIFTING NORTH AWAY FROM THE REGION HELPING EXPLAIN THE LACK OF SUPPORT ALOFT. THE JET PUSHES BACK SOUTH TUESDAY NIGHT INTO EARLY WEDNESDAY...SO THIS WILL HELP PUSH A COLD FRONT THROUGH THE REGION. THIS WILL TRANSITION WINDS TO MORE OF A NORTHERLY FLOW FOR WEDNESDAY. THE FLOW WEAKENS THURSDAY...ALLOWING FOR SEA BREEZES TO DEVELOP AS HIGH PRESSURE BUILDS IN FROM THE SOUTH AND WEST. THE HIGH MOVES OFFSHORE FRIDAY INTO THE NEXT WEEKEND. ANOTHER COLD FRONT APPROACHES INTO THE BEGINNING OF NEXT WEEKEND. OUTSIDE OF WEDNESDAY...A GENERAL SOUTH TO SOUTHWEST FLOW DOMINATES NEXT WEEK. THIS WILL RESULT IN TEMPERATURES WELL ABOVE SEASONAL AVERAGES FOR THIS TIME OF YEAR. THE JET STREAM OVERALL KEEPS TO THE NORTH OF THE REGION. TEMPERATURES WILL BE GENERALLY 5-10 DEGREES ABOVE NORMAL MONDAY THROUGH WEDNESDAY AND A FEW DEGREES ABOVE NORMAL WEDNESDAY NIGHT THROUGH SATURDAY. ANOTHER CHANCE OF SHOWERS AND THUNDERSTORMS FROM NORTHWEST TO SOUTHEAST TUESDAY INTO TUESDAY NIGHT WITH A LITTLE MORE SHEAR TO WORK WITH. MAINLY DRY THEREAFTER WITH A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TOWARDS END OF THE WORK WEEK INTO THE NEXT WEEKEND WITH NEXT FRONT APPROACHING. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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A TROUGH OF LOW PRES APPROACHES FROM THE WEST TODAY AND MOVES ACROSS THE AREA TONIGHT. MVFR CIGS WILL LIFT BACK TO VFR THIS MORNING WHERE IT SHOULD REMAIN FOR THE MAJORITY OF THE DAY. TIMING MAY BE OFF 1-2 HOURS. HZ MAY DEVELOP THIS AFTN AND COULD LOCALLY RESTRICT VSBY TO MVFR IN SPOTS. ISOLATED SHRA/TSRA POSSIBLE ALONG SEABREEZE BOUNDARIES THIS AFTN BUT CHCS ARE TOO LOW TO INCLUDE. OTHERWISE...INCREASING CHANCE FOR SHRA/TSTMS LATE AFTN/EVE MAINLY FROM CITY TERMINALS AND POINTS N/W AS TROUGH APPROACHES. TIMING OF MAY NEED TO BE ADJUSTED A FEW HOURS. THESE INCREASING CHCS TRANSLATE EWD DURING THE EVE. MVFR TO LOCALLY IFR POSSIBLE IN CONVECTION. UNCERTAINTY IN HOW PROGRESSIVE RAIN IS ACROSS THE AREA AND MAY BE HOLDING ON TO IT TOO LONG. MVFR CONDS POSSIBLE AGAIN LATE TONIGHT INTO MON MORNING WITH A MOIST AIRMASS REMAINING IN PLACE...ESPECIALLY WHERE PCPN ENDS AND LIGHT WINDS DEVELOP. .OUTLOOK FOR 12Z MON THROUGH THU... .MON-MON NIGHT...ADDITIONAL SCT SHRA/TSRA POSSIBLE MON AFT/EVE. MVFR STATUS/FOG POSSIBLE LATE MON NIGHT. .TUE...SCT AFT/EVE SHRA/TSRA POSSIBLE. .WED-THU...MAINLY VFR.
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&& .MARINE... THE PRES GRADIENT WILL TIGHTEN TODAY AS LOW PRES PASSES TO THE N AND HIGH PRES CONTINUES TO DEPART OUT TO SEA. THIS WILL RESULT IN AN INCREASING SLY FLOW. SEAS ON THE OCEAN WATERS WILL BUILD IN RESPONSE WITH SCA CONDS EXPECTED TO BE MET THIS EVENING AND CONTINUE THROUGH THE NIGHT BEFORE SUBSIDING EARLY MON MORNING. THERE IS THE POTENTIAL FOR 5 FT SEAS TO LINGER A FEW HOURS LONGER E OF MORICHES INLET...BUT WILL END THE HAZARD AT 10Z FOR NOW. WIND GUSTS WILL ALSO COME CLOSE TO 25 KT AT TIMES...MAINLY THIS EVE. SUB-ADVSY CONDS ARE THEN EXPECTED THROUGH THE REMAINDER OF THE FORECAST PERIOD WITH A FAIRLY WEAK GRADIENT OVER THE AREA. && .HYDROLOGY... DEEP MOISTURE IN PLACE WITH A SERIES OF SHORTWAVES ALOFT AND SURFACE TROUGHS WILL INTERACT TO PRODUCE CONVECTION EACH AFT/EVE OVER THE NEXT COUPLE OF DAYS WITH THE POTENTIAL FOR LOCALIZED HEAVY RAINFALL. A LOCALIZED FLOOD THREAT REMAINS FOR FLASH FLOODING. ON AVERAGE...LOOKING FOR ABOUT AN INCH OF RAINFALL ACROSS THE BASINS...WITH SEVERAL INCHES POSSIBLE IN STRONGER MORE ORGANIZED CONVECTION. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT MONDAY FOR ANZ350-353-355. && $$ SYNOPSIS...DW NEAR TERM...DW SHORT TERM...DW LONG TERM...JM/DW AVIATION...24 MARINE...24 HYDROLOGY...DW

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