Issued by NWS Upton, NY
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS61 KOKX 210536 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1236 AM EST SAT NOV 21 2009 .SYNOPSIS... HIGH PRESSURE WILL BUILD EASTWARD FROM THE OHIO VALLEY. THIS HIGH WILL RESULT IN FAIR AND DRY WEATHER THROUGH SUNDAY. THE STRENGTHENING HIGH WILL THEN BUILD INTO NORTHERN NEW ENGLAND AND THE CANADIAN MARITIMES SUNDAY NIGHT INTO MONDAY NIGHT...WHICH MAY ALLOW WEAK LOW PRESSURE TO SLOWLY MOVE UP THE COAST MONDAY THROUGH TUESDAY. FAIR WEATHER SHOULD RETURN ON TUESDAY. ANOTHER COASTAL LOW MAY APPROACH THURSDAY NIGHT INTO FRIDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... SECONDARY COLD FRONT WELL TO THE EAST ATTM. NW-W WINDS HAVE DIMINISHED...BUT REMAIN IN THE 5 TO 10 KTS RANGE. THESE WINDS SUFFICIENT TO PRECLUDE IDEAL RAD COOLING CONDITIONS. SO...IN SPITE OF MOSTLY CLEAR SKIES...MIN TEMPS TONIGHT WILL BE ON THE WARMER SIDE OF THE GUIDANCE...RANGING FROM THE 40S IN COASTAL AND URBAN SECTIONS...TO THE MID/UPPER 30S INLAND. IF WINDS DO FULLY DECOUPLE LATE TONIGHT...SOME INTERIOR LOCATIONS AND THE LI PINE BARRENS COULD DROP TO AROUND FREEZING. && .SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/... HIGH PRESSURE BUILDING FROM THE OH VALLEY WILL BE IN CONTROL THROUGH AT LEAST SUNDAY EVENING. DOWNSLOPE FLOW AND MIXING TO ABOUT 950 MB /2 KFT/ SHOULD BOOST HIGH TEMPS A LITTLE ABOVE MOST GUIDANCE...WITH LOWER 60S IN URBAN NORTHEAST NJ AND THE CT RIVER VALLEY...AND MID/UPPER 50S ELSEWHERE. AS THE HIGH BUILDS MORE SQUARELY OVER THE AREA SAT NIGHT...MINS WILL BE A LITTLE COOLER AND MORE LIKELY TO BOTTOM OUT AROUND FREEZING INLAND AND IN THE LONG ISLAND PINE BARRENS...BUT SHOULD REMAIN ABOVE FROST ADVISORY CRITERIA IN NYC AND HUDSON COUNTY NJ...THE ONLY REMAINING AREAS IN THE CWA WHERE THE GROWING SEASON HAS NOT YET OFFICIALLY ENDED. LOSS OF DOWNSLOPE FLOW AND AND LOWER 850-1000 MB THICKNESSES UNDERNEATH THE HIGH ARGUE FOR HIGH TEMPS A FEW DEGREES COOLER THAN THOSE OF SAT BUT STILL A TOUCH ABOVE GUIDANCE...MAINLY LOWER AND MID 50S. FORECAST UNCERTAINTIES BEGIN TO CREEP IN DURING SUN NIGHT-MON REGARDING THE APPROACH OF A WEAK COASTAL LOW. HIGH PRESSURE PASSING TO THE NORTH OF THE AREA BECOMES VERTICALLY STACKED AND STRENGTHENS SUN NIGHT-MON...WHICH MAY SUPPRESS THE LOW ENOUGH TO MAINTAIN FAIR WX. NAM/ECMWF AN SOME GEFS MEMBERS SUPPORT THIS IDEA...WHILE THE OPERATIONAL GFS AND CANADIAN GGEM REMAIN WET. HAVE BACKED OFF EARLIER LIKELY POP...BUT WITH THE AXIS OF SURFACE RIDGING NORTH OF THE AREA AND MAINTAINING A LOW LEVEL ONSHORE FLOW...AND A MID LEVEL SHORTWAVE UNDERCUTTING THE HIGH...THINK CHANCE POP IS STILL IN ORDER FOR MON...ESPECIALLY IN THE AFTERNOON. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... MODELS LACK CONSISTENCY RIGHT FROM THE BEGINNING OF THE PERIOD ON THE STRENGTH OF THE SOUTHERN STREAM CLOSED LOW SHEARING NE MON NIGHT...AND DISPLACEMENT OF STACKED RIDGING. THIS IS RESULTING IN DIFFERENCES IN THE NORTHWARD TRACK AND STRENGTH OF THE SURFACE LOW. WITH THIS UNCERTAINTY HAVE HELD POP TO CHANCE FOR MON NIGHT. FORECAST DETAILS CONTINUE SHAKY THEREAFTER...WITH UNCERTAINTY IN PROGRESSION OF PACIFIC SHORTWAVE FEATURES INTO THE LOWER 48. MODELS HINT AT A PERIOD OF RIDGING TUE INTO WED AS UPPER ENERGY DIGS OVER THE CENTRAL STATES...WITH LATE A WEEK COASTAL SYSTEM POSSIBLE AS UPPER ENERGY WORKS TOWARD THE COAST. HAVE CONTINUED WITH CHANCE POP FOR THIS PERIOD WITH UNCERTAINTY. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...-- Changed Discussion --VFR THROUGH THE DAY TODAY AS HIGH PRESSURE BUILDS TOWARD THE AREA. WEST WINDS INTO THE EARLY MORNING HOURS WILL VEER TO THE WEST/NW AT 5 TO 10 KTS FROM MID MORNING THROUGH THE AFTERNOON. THESE WINDS VEER FURTHER TO THE NORTH TOWARD EVENING AND CONTINUE OVERNIGHT. OUTLOOK 06Z SUNDAY THROUGH WEDNESDAY... SUN: VFR. MON: SUB-VFR. TUE AND WED...VFR LIKELY.-- End Changed Discussion --&& .MARINE... WINDS HAVE DIMINISHED BELOW 25 KTS...AND SEAS CONTINUE TO SUBSIDE. OVERALL...I EXPECT SEAS TO REMAIN BELOW 5 FT...ALTHOUGH THEY COULD TOUCH 5 FEET FROM TIME TO TIME. AS SUCH...SCA HAS BEEN CANCELLED FOR THE TWO EASTERN OCEAN ZONES. QUIET CONDITIONS SHOULD THEN BE THE RULE WITH HIGH PRESSURE IN CONTROL UNTIL LATE SUN NIGHT-MON NIGHT...WHEN INCREASING EASTERLY FLOW BETWEEN STRONG HIGH PRESSURE TO THE NORTHEAST AND A COASTAL LOW TO THE SOUTH COULD YIELD SCA CONDITIONS. WINDS SHOULD DIMINISH ON TUE AS HIGH PRESSURE BUILDS BACK IN... WITH SEAS SUBSIDING BELOW SCA THROUGH WED. && .HYDROLOGY... SPREAD IN MODEL QPF IS QUITE LARGE FOR POSSIBLE COASTAL SYSTEM SUNDAY NIGHT-MON NIGHT...WITH SUPPRESSED SOLUTIONS VIRTUALLY DRY AND STRONGER/WETTER SOLUTIONS BRINGING OVER AN INCH ESPECIALLY TO NYC METRO. CURRENT FORECAST LEANS TOWARD THE DRIER SIDE OF THE ENVELOPE...SO HYDROLOGIC/FLOODING ISSUES APPEAR UNLIKELY ATTM. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$
