Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 300621 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 221 AM EDT THU JUL 30 2015 .SYNOPSIS... WEAK HIGH PRESSURE WILL SLIDE OFF THE MID ATLANTIC COAST TONIGHT. A COLD FRONT WILL APPROACH ON THURSDAY...AND MOVE ACROSS THURSDAY NIGHT. WEAK HIGH PRESSURE WILL RETURN FRIDAY THROUGH SATURDAY. A WEAK LOW PRESSURE TROUGH WILL MOVE THROUGH SATURDAY NIGHT INTO EARLY SUNDAY...FOLLOWED BY ANOTHER WEAK TROUGH SUNDAY NIGHT. A COLD FRONT WILL APPROACH MONDAY NIGHT...AND REMAIN NEARBY THROUGH MID WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... FORECAST OVERNIGHT REMAINS ON TRACK. UPDATED THE NEAR TERM GRIDS TO BETTER REFLECT TRENDS IN LATEST OBSERVATIONS AND MODEL DATA MAINLY WITH RESPECT TO TEMPERATURES AND DEWPOINTS. ADDED IN SOME PATCHY FOG TOWARDS DAYBREAK ACROSS EASTERN SECTIONS WHERE LOWER TEMP AND DEWPOINT DEPRESSIONS RESIDE. A LARGE CONSENSUS OF BOTH SYNOPTIC AND MESOSCALE MODELS POINTING TOWARDS SOME CONVECTIVE DEVELOPMENT NEAR AND WEST OF NYC AFTER 08Z. POPS WERE LEFT AS PREVIOUSLY FORECAST. WARM AND MUGGY TONIGHT WITH LOWS IN THE 70S FOR MUCH OF THE AREA ALTHOUGH A FEW SPOTS IN THE NYC METRO MAY STRUGGLE TO FALL BELOW 80 DEGREES. CONVECTION IN PARTS OF THE MID ATLANTIC AND CENTRAL APPALACHIANS ASSOCIATED WITH AN APPROACHING SHORTWAVE HAS LARGELY DISSIPATED OVER THE LAST FEW HOURS. NOT EXPECTING MUCH IN THE WAY OF CONVECTIVE ACTIVITY WITH THIS SHORTWAVE...BUT AN ISO SHOWER OR STORM CANNOT BE RULED OUT BEFORE DAYBREAK. THE LAST SEVERAL RUNS OF THE HRRR HINT AT THIS POSSIBILITY. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... COULD STILL SEE ISO TO WDLY SCT ELEVATED CONVECTION FROM NYC METRO NORTH/WEST IN THE MORNING AS THE LEADING SHORTWAVE MOVES THROUGH. APPROACHING COLD FRONT SHOULD BRING SCT TO NUMEROUS TSTMS FROM LATE AFTERNOON INTO THE EVENING AS AIR MASS DESTABILIZES...WITH SBCAPE UP TO 1000 J/KG. THERE SHOULD BE ENOUGH SHEAR TO SUPPORT AN ORGANIZED LINE OF STORMS OR MULTI-CELL CLUSTERS...AND GIVEN A SW LLJ UP TO 35 KT AS FCST PER NAM...THESE STORMS HAVE A BETTER CHANCE OF SURVIVING AS THEY MOVE PAST NYC METRO AND THE LOWER HUDSON VALLEY INTO LONG ISLAND AND CT. STRONGER CELLS HAVE POTENTIAL TO PRODUCE STRONG WIND GUSTS AND DUMP LOCALLY HEAVY RAINFALL AS PW INCREASES TO JUST OVER 2 INCHES. HIGHS ON THURSDAY SHOULD BE NOT QUITE AS WARM AS TODAY...GENERALLY 85-90...BUT WITH HIGHER DEWPOINTS MAX HEAT INDEX VALUES SHOULD STILL BE SIMILAR TO THOSE OF TODAY...STILL REACHING THE MID 90S EXCEPT IN THE HIGHER ELEVATIONS AND EASTERN COASTAL SECTIONS...SO THE HEAT ADVY WILL CONTINUE FOR NYC. THERE IS A HIGH RISK OF RIP CURRENTS AT OCEAN BEACHES ON THURSDAY. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... LONG WAVE UPPER LEVEL TROUGH WILL BE OVER THE NORTHEAST U.S. FOR MUCH OF THIS TIME PERIOD. AT THE SURFACE...A COLD FRONT WILL REMAIN JUST OFF THE EAST COAST FRIDAY...WITH WEAK HIGH PRESSURE BUILDING IN. SUBSIDENCE FROM THIS HIGH SHOULD KEEP THE AREA DRY THROUGH MUCH OF SATURDAY. A WEAK SURFACE TROUGH APPROACHES LATE SATURDAY...WEAKENING AS IT DOES SO. 12Z GFS DOES SEEM MORE POTENT AS OPPOSED TO THE 00Z ECMWF AND BRINGS THE TROUGH THROUGH LATE SATURDAY NIGHT WITH A BRIEF PERIOD OF SHOWERS AND THUNDERSTORMS. SOME INSTABILITY PRECEDING THE TROUGH...SO THUNDERSTORMS ARE POSSIBLE. HOWEVER...JET DYNAMICS LOOK WEAK...THOUGH LIFT WITH THE TROUGH AT LEAST EARLY IN THE NIGHT LOOKS DECENT ACCORDING TO THE 12Z GFS. HOWEVER...LIFT QUICKLY WEAKENS AS THE TROUGH MOVES EAST LATE SATURDAY NIGHT. WEAK HIGH PRESSURE BUILDS IN FOR SUNDAY AND MONDAY WITH A COLD FRONT APPROACHING MONDAY NIGHT. COLD FRONT SLOWS ITS APPROACH AND BECOMES NEARLY STATIONARY IN THE VICINITY MONDAY NIGHT INTO WEDNESDAY. AGAIN...SOME INSTABILITY OVER THE AREA AS THE FRONT MOVES THROUGH...MAINLY FOR EASTERN SECTIONS...SO THUNDERSTORMS ARE ONCE AGAIN POSSIBLE. LIFTED INDICES -8 TO -2 DURING TUESDAY NIGHT...WITH LIFT BEING PROVIDED BY THE FRONT. MOISTURE IS ALSO AVAILABLE...WITH SURFACE DEWPOINTS IN THE 60S AND PW RANGING FROM 1.25-1.50...THOUGH THEY ARE NOT EXCEPTIONALLY HIGH. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... A SOUTHERLY FLOW CONTINUES AROUND HIGH PRESSURE OFF THE MID ATLANTIC COAST AS A COLD FRONT THROUGH THE GREAT LAKES AND INTO OHIO SLOWLY APPROACHES. GENERALLY VFR THROUGH THE MORNING...ALTHOUGH ISOLD MVFR IN FOG/HAZE DEVELOPING. SEVERAL PIECES OF GUIDANCE INDICATING WDLY SCT SHOWER ACTIVITY DEVELOPING OVER CENTRAL/NRN NJ BETWEEN 09Z AND 12Z AND TRACKING TO THE NE THROUGH 15Z OR SO. HAVE INCLUDED VCSH AT MOST TERMINALS TO ACCOUNT FOR THIS...BUT WOULD LIKE TO SEE SOMETHING ON RADAR BEFORE ADDING IT INTO PREVAILING OR TEMPO. THE COLD FRONT AND A WEAK PRE-FRONTAL TROUGH WILL BE MOVING INTO THE TERMINALS AROUND 18Z TODAY AND MOVE THROUGH THIS EVENING. SCATTERED SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE FRONT WITH MVFR CONDITIONS...OR POSSIBLY IFR IN STRONGER STORMS. THERE IS A HIGHER CHANCE OF CONVECTION FROM THE NYC TERMINALS AND AREAS WEST. WILL CONTINUE TO INDICATE THE CHANCES WITH A PROB GROUP. HEAVY RAIN WILL LIKELY ACCOMPANY ANY SHOWERS THIS MORNING AND ESPECIALLY IN TSTMS THIS AFTN/EVE. THIS WILL DROP VSBYS TO IFR OR LOWER IN THE HEAVIEST ACTIVITY. MODERATE TO HIGH CONFIDENCE IN WIND FORECAST...GUSTS IN THE UPPER TEENS TO LOWER 20S POSSIBLE AT KJFK AS WELL AS OTHER COASTAL TERMINALS. .OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY... .THURSDAY NIGHT...MVFR CONDS IN FOG/HZ BECOMING VFR. .FRIDAY-MONDAY...VFR. && .MARINE... QUIET THROUGH THU MORNING. THEN AS SW FLOW INCREASES TO 15-20 KT WITH FAVORABLE FETCH...OCEAN SEAS SHOULD BUILD TO 5-6 FT THU AFTERNOON AND NIGHT. LOW LEVEL JET PASSING OHD SHOULD MIX TO THE SFC...WITH GUSTS UP TO 25 KT LIKELY ON THE OCEAN AND THE BAYS OF LONG ISLAND. SCA ISSUED FOR THESE HAZARDS. TSTMS WILL ALSO BE A HAZARD WITH A COLD FRONTAL PASSAGE THU AFTERNOON/EVENING. OCEAN SEAS COULD BUILD TO AROUND 5 FT SAT NIGHT INTO SUNDAY... AND AGAIN LATE SUNDAY INTO MONDAY MORNING. THEN A MORE PROLONGED PERIOD OF 5-FT OCEAN SEAS IS POSSIBLE FROM MON NIGHT INTO MID WEEK. && .HYDROLOGY... BASIN AVG QPF OF 1/2 TO 3/4 INCH POSSIBLE IN THE LOWER HUDSON VALLEY AND NE NJ...WITH UP TO 1/2 INCH ELSEWHERE. WITH PW OVER 2 INCHES THU AFTERNOON AND EVENING...LOCALLY HEAVY RAINFALL IS POSSIBLE WITH ANY STRONGER CONVECTION. MINOR URBAN/POOR DRAINAGE FLOODING IS THE MOST LIKELY OUTCOME. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR NYZ072>075-176- 178. HIGH RIP CURRENT RISK FROM 6 AM EDT THIS MORNING THROUGH THIS EVENING FOR NYZ075-080-081-178-179. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 8 PM EDT THIS EVENING FOR ANZ340-345. SMALL CRAFT ADVISORY FROM NOON TODAY TO MIDNIGHT EDT TONIGHT FOR ANZ355. SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EDT FRIDAY FOR ANZ350-353. && $$ SYNOPSIS...GOODMAN/JP NEAR TERM...GOODMAN/JM/DS SHORT TERM...GOODMAN/DS LONG TERM...JP AVIATION...24 MARINE...GOODMAN/JP HYDROLOGY...GOODMAN/JP

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