Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 260209 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1009 PM EDT FRI JUL 25 2014 .SYNOPSIS... HIGH PRESSURE WILL SHIFT OFFSHORE TONIGHT INTO SATURDAY. A WARM FRONT MOVES THROUGH SATURDAY NIGHT...FOLLOWED BY A COLD FRONT MONDAY. THE COLD FRONT MOVES ACROSS MONDAY NIGHT. HIGH PRESSURE THEN BUILDS IN BEHIND THE COLD FRONT BY MID WEEK NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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FORECAST REMAINS ON TRACK. WILL MAKE MINOR ADJUSTMENTS BASED ON LATEST SFC OBS. OTHERWISE...SFC HIGH PRES REMAINS OVER THE AREA AS AN UPPER LEVEL DISTURBANCE PASSES THROUGH THE REGION. S/SW FLOW OVER THE AREA WILL RESULT IN INCREASED MOISTURE OVER THE REGION THROUGH THE OVERNIGHT. LOWS WILL BE CLOSE TO NORMAL. PATCHY FOG WILL DEVELOP AWAY FROM THE CITY.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... FOR SATURDAY...THERE WILL BE A MODERATE RISK OF RIP CURRENTS ALONG ATLANTIC FACING BEACHES. AN APPROACHING UPPER LEVEL JET WILL LEAD TO SURFACE PRESSURE FALLS ACROSS THE EAST. MODELS GENERALLY SUGGEST A CORRIDOR OF FAVORABLE SURFACE CONVERGENCE DEVELOPING ACROSS NJ AND WEST OF NYC WHERE THUNDERSTORMS SHOULD INITIATE LATE IN THE AFTERNOON AS CINH ERODES. HIGH TEMPS WILL BE A FEW DEGREES WARMER THAN THE PREVIOUS DAY...PRIMARILY ACROSS THE INTERIOR WHERE THE MARITIME INFLUENCE WILL NOT BE FELT. BY SATURDAY NIGHT INTO SUNDAY MORNING...A WARM FRONT WILL FINALLY MOVE NORTHEASTWARD/POLEWARD THROUGH THE FORECAST AREA. A CONCURRENT SHORT WAVE ALOFT WILL AID IN THUNDERSTORM DEVELOPMENT OVERNIGHT INTO THE MORNING. AS LOW LEVEL MOISTURE INCREASES AND WEST-NORTHWEST FLOW ALOFT ADVECTS STEEPER MID-LEVEL LAPSE RATES INTO THE REGION...INSTABILITY WILL INCREASE OVERNIGHT. THE INCREASED INSTABILITY COMBINED WITH 30-40KT OF 0-6KM SHEAR MAY BE SUFFICIENT FOR ISOLATED SMALL HAIL. ALTHOUGH A WEAK INVERSION WILL EXIST AROUND 850 HPA...A BRIEFLY ROTATING STORM AND/OR WEAK TORNADO NEAR THE WARM FRONT...ESPECIALLY ALONG THE SOUTH SHORE OF THE NYC BOROUGHS AND LONG ISLAND CANNOT BE RULED OUT. ADDITIONALLY...PWAT VALUES NEAR 1.85 INCH INDICATE HEAVY RAIN POTENTIAL IN ANY THUNDERSTORMS THAT DEVELOP. && .LONG TERM /SUNDAY THROUGH FRIDAY/... RELATIVELY ACTIVE WEATHER PATTERN FEATURED IN THE LONG TERM AND HAS BEEN PRESENT AT OTHER TIMES THIS SUMMER...AN UPPER LEVEL TROUGH WILL BE SETTING UP ACROSS THE NORTHEAST. THIS LINGERS THROUGH MUCH OF THE LONG TERM PERIOD. AT THE SURFACE...A PARENT LOW MOVING ACROSS SOUTHERN QUEBEC INTO NORTHERN NEW ENGLAND WILL HAVE AN ASSOCIATED WARM FRONT MOVING ACROSS EARLY SUNDAY. THE ASSOCIATED COLD FRONT WILL STAY NORTH AND WEST OF THE REGION THROUGH THE REST OF SUNDAY AND SUNDAY NIGHT...WITH AN AREA OF LOW PRESSURE APPROACHING THE AREA ALONG THE FRONT. WITH SOME PATCHY FOG AND CONVECTION SUNDAY MORNING...THERE COULD BE A BRIEF RESPITE BEFORE ANOTHER ROUND OF CONVECTION DEVELOPS WITH AFTERNOON HEATING. SREF POPS WERE PREFERRED HERE AS THEY HAVE BEEN CONSISTENT FROM RUN TO RUN SHOWING HIGHER POPS ACROSS NYC AND THE INTERIOR. WE WILL BE IN THE WARM SECTOR. THE CONVECTION WILL SPREAD EASTWARD AT NIGHT ACROSS THE REST OF THE REGION INCLUDING THE COASTAL SECTIONS. THERE WILL BE HIGHER LAYER PW SUNDAY AND SUNDAY NIGHT WITH AROUND 1.5 TO 1.7 INCHES FROM SOUTHWEST ATMOSPHERIC FLOW. THE FLOW IS PARALLEL FROM LOWER TO MID LEVELS. THEREFORE...THERE COULD BE TRAINING OF CELLS AND SOME CELLS COULD PRODUCE HEAVY DOWNPOURS. IN TERMS OF SHEAR 0-6KM...25-30 KT SUNDAY ALONG WITH CAPE OF 1000-1500 J/KG WILL ALLOW FOR STRONGER CONVECTION TO DEVELOP. THE WINDS IN THE BOUNDARY LAYER WILL BE MORE ON THE LIGHT SIDE...MOSTLY BELOW 30 KT...SO SEVERE POSSIBILITY SEEMS MARGINAL AT THE MOMENT. BUT ANY HELICITY INCREASE FROM PERHAPS MORE VEERING LOW LEVEL PROFILES AS WELL AS ANY INCREASE IN THE SHEAR...WOULD INCREASE THE SEVERE POTENTIAL. THE WAVE OF LOW PRESSURE MOVES NORTHEAST OF THE REGION MONDAY AND THIS WILL EVENTUALLY DRAG A COLD FRONT ACROSS MONDAY NIGHT. AGAIN...THERE COULD BE ANOTHER LULL IN ACTIVITY BEFORE THE NEXT BATCH OF CONVECTION DEVELOPS AND MOVES IN. THIS WILL BE ASSOCIATED WITH THE COLD FRONT. SHEAR 0-6KM WILL BE A LITTLE HIGHER MONDAY WITH DEEPENING TROUGH MOVING IN WITH MAGNITUDE INCREASE OF ABOUT 5-10 KT COMPARED TO PREVIOUS DAY. COLDER AIR ALOFT WILL BE MOVING IN. CAPE THOUGH IS A LITTLE MORE LIMITED AND THIS IS LIKELY RELATED TO LESS MOISTURE FROM A LITTLE MORE WESTERLY FLOW. AFTER THIS...WEATHER PATTERN BEGINS TO STABILIZE WITH HEIGHTS BUILDING AS THE UPPER LEVEL TROUGH BEGINS TO LIFT NORTH OF THE REGION. AT THE SURFACE...HIGH PRESSURE WILL BEGIN TO BUILD IN FROM THE WEST. THE HIGH PRESSURE CONTINUES TO BUILD IN AND THE UPPER LEVEL TROUGH AMPLITUDE CONTINUES TO WEAKEN WITH TIME THROUGH THE REST OF THIS PERIOD. THIS WILL ALLOW FOR A DRY AIRMASS TO ENCOMPASS THE REGION. TEMPERATURES WILL NOT DEVIATE TOO MUCH FROM NORMAL. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
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HIGH PRESSURE OVER THE REGION WEAKENS SATURDAY AFTERNOON AS A SURFACE TROUGH AND WARM FRONT APPROACH FROM THE SOUTHWEST. VFR. A SOUTH TO SOUTHWEST FLOW WILL PREVAIL THROUGH THE FORECAST PERIOD...INCREASING TO 10 KT TO 15 KT SATURDAY. A FEW GUSTS UP TO 20 KT ARE POSSIBLE...HOWEVER GUSTS WILL NOT BE FREQUENT TO INCLUDE IN THE FORECAST. .OUTLOOK FOR 00Z SUN THROUGH WED... .SAT NIGHT-MON...VFR WITH A CHANCE OF SHRA/TSTMS WITH MVFR OR LOWER POSSIBLE. .TUE-WED...VFR.
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&& .MARINE... RELATIVELY TRANQUIL CONDITIONS EXPECTED ACROSS THE WATERS THROUGH SATURDAY. INCREASING SOUTHERLY FLOW AHEAD OF A WARM FRONT SATURDAY NIGHT IS EXPECTED...WITH SOUTHERLY WINDS CONTINUING SUNDAY INTO MONDAY AHEAD OF A COLD FRONT. WINDS SHIFT BEHIND THE COLD FRONT MONDAY NIGHT INTO TUESDAY. SEAS BUILD SATURDAY NIGHT IN RESPONSE TO THE INCREASING SOUTH FLOW. SCA SEAS ARE FORECAST TO BEGIN SUNDAY AFTERNOON AND CONTINUE THROUGH MONDAY NIGHT BEFORE SUBSIDING BELOW GOING INTO TUESDAY. WAVE WATCH III OUTPUT COULD BE TOO FAST WITH INCREASING SEAS SO FUTURE FORECASTS MAY HAVE THIS SCA POTENTIAL BEGINNING MORE SUNDAY NIGHT AS OPPOSED TO SUNDAY AFTERNOON. && .HYDROLOGY... UNSETTLED WEATHER WITH SCATTERED TO NUMEROUS SHOWERS/TSTMS ARE FORECAST SATURDAY NIGHT THROUGH MONDAY. ANY OF THESE STORMS HAVE THE POTENTIAL TO PRODUCE HEAVY DOWNPOURS. SIGNIFICANT UNCERTAINTY STILL EXISTS WITH TIMING AND AMOUNTS THOUGH. IT LOOKS LIKE THE HIGHER POTENTIAL FOR HEAVY RAIN IS SUNDAY AND SUNDAY NIGHT WITH HIGHER PWATS OF 1.5 TO 1.7 INCHES ACROSS THE REGION. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...MMD/JM NEAR TERM...MPS SHORT TERM...MMD LONG TERM...JM AVIATION...MET MARINE...MMD/JM HYDROLOGY...JM

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