Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 241816 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 116 PM EST WED DEC 24 2014 .SYNOPSIS... A WARM FRONT SLOWLY APPROACHES FROM THE SOUTH...THEN LIFTS TO THE NORTH THIS AFTERNOON. A COLD FRONT APPROACHES FROM THE WEST THIS EVENING...AND CROSSES THE TRI-STATE OVERNIGHT...WITH ITS ASSOCIATED LOW TRACKING INTO QUEBEC THURSDAY. HIGH PRESSURE THEN BUILDS INTO THE SOUTH OF LONG ISLAND THROUGH SATURDAY NIGHT...FOLLOWED BY A COLD FRONT EARLY SUNDAY. UNSETTLED WEATHER IS THEN POSSIBLE THROUGH THE MIDDLE OF THE WEEK AS A SERIES OF LOW PRESSURE SYSTEMS MAY IMPACT THE REGION. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MINOR CHANGES MADE TO THE FORECAST TO REFLECT THE LATEST TRENDS IN OBSERVATIONS. OTHERWISE...THE FORECAST APPEARS ON TRACK. WITH INCREASING LOW LEVEL FLOW FORECAST...ISENTROPIC LIFT WILL STRENGTHEN...WITH RAIN BECOMING MODERATE TO POSSIBLY LOCALLY HEAVY AT TIMES BY LATE MORNING. RAIN SHOULD TAPER OFF MID-LATE AFTERNOON ONCE THE SURFACE WARM FRONT LIFTS NORTH...AS YOU WILL NO LONGER BE SATURATED IN THE LOWEST LAYERS ISENTROPICALLY. TEMPERATURES WILL NOT MOVE MUCH THIS MORNING FROM CURRENT LEVELS...THEN RISE FAIRLY RAPIDLY THIS AFTERNOON BEHIND THE WARM FRONT. HIGHS BASED ON A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES - WEIGHED TOWARDS WARMEST GUIDANCE. VALUES SHOULD BE AROUND 15-20 DEGREES ABOVE NORMAL...AND COULD REACH NEAR RECORD LEVELS IN SOME LOCATIONS. REFER TO THE CLIMATE SECTION OF THE AFD FOR DETAILS. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... MAIN FEATURE TONIGHT IS FORECAST 6065 KT 950 HPA JET FORECAST TO PASS JUST S OF LONG ISLAND AHEAD OF COLD FRONT. SHOULD HAVE SUFFICIENT ELEVATED INSTABILITY - SHOWALTER INDICES AROUND 0 AND BUFKIT SOUNDINGS SHOW AROUND 150 J/KG OF ELEVATED CAPE - TO PRODUCE SOME RUMBLES OF THUNDER TONIGHT AHEAD OF THE COLD FRONT. GIVEN THE STRONG LOW LEVEL JET...HAVE A SMALL CHANCE OF MIXING DAMAGING WINDS TO THE SURFACE WITH STRONG CONVECTION...ESPECIALLY IF A FINE CONVECTIVE LINE FORMS AHEAD OF THE COLD FRONT. WILL ADDRESS THIS WITH SPECIAL WEATHER STATEMENTS AND SEVERE THUNDERSTORM WARNINGS IF/WHEN WARRANTED. OTHERWISE...LOW LEVEL INVERSION SHOULD KEEP THE BULK OF THE LOW LEVEL WINDS AT BAY...WITH GUSTS GENERALLY LIMITED TO AROUND 20 TO MAYBE 30 MPH. SHOWERS SHOULD TAPER OFF RATHER QUICKLY EARLY THURSDAY MORNING AS THE COLD FRONT EXITS TO THE EAST. REFER TO THE HYDROLOGY SECTION OF THE AFD FOR TOTAL QPF AND ANY IMPACTS FROM THIS SYSTEM. CHRISTMAS DAY SHOULD SEE FAIRLY RAPID CLEARING BEHIND THE FRONT...WITH GUSTY W WINDS TO 30-40 MPH...HIGHEST OVER HIGHER ELEVATIONS AND NEAR THE IMMEDIATE COAST. FOR NOW APPEARS SHOULD BE JUST BELOW ADVISORY LEVELS...HOWEVER GUIDANCE HAS TRENDED SLIGHTLY STRONGER WITH LOW LEVEL WINDS BEHIND THE FRONT...AND IF THIS TREND HOLDS...THEN A WIND ADVISORY COULD ULTIMATELY END UP BEING NEEDED. FOR LOWS TONIGHT...USED A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES. EXPECT RISING TEMPERATURES AHEAD OF THE COLD FRONT...THEN TEMPERATURES FALL OFF SOMEWHAT BEHIND IT. HOWEVER WITH THE COLD FRONT NOT MOVING THROUGH UNTIL AFTER 6Z...WILL NOT HAVE A LOT OF TIME FOR THE LOW LEVEL COLD AIR TO WORK ITS WAY IN OVER THE APPALACHIANS BEHIND THE FRONT. LOWS SHOULD BE AROUND 20-25 DEGREES ABOVE NORMAL...AND AROUND 10 DEGREES ABOVE THE NORMAL HIGH FOR THIS TIME OF YEAR. FOR HIGHS CHRISTMAS DAY A BLEND OF MIXING DOWN FROM 875-850 HPA FROM BUFKIT SOUNDINGS WITH NAM 2-METER TEMPERATURES AND A BLEND OF MAV/MET/ECS GUIDANCE WAS USED - WITH VALUES FORECAST TO BE AROUND 15 DEGREES ABOVE NORMAL. HIGHS SHOULD OCCUR IN THE MORNING...WITH TEMPERATURES FALLING OFF TO THE 40S BY LATE AFTERNOON. IT WILL CONTINUE TO BE BREEZY TO WINDY EARLY ON CHRISTMAS NIGHT...WITH GUSTS UP TO 30-40 MPH POSSIBLY EARLY IN THE EVENING. WINDS THEN DIMINISH...FALLING OFF TO 10 TO 15 MPH ACROSS THE NYC METRO AND NEAR THE COAST...AND TO 5 TO 10 MPH INLAND. THE CLEARING AND DIMINISHING WINDS INLAND...SHOULD ALLOW FOR SOME RADIATIONAL COOLING THERE...SO FOR LOWS USED A BLEND OF MAV/MET GUIDANCE WITH NAM 2-METER TEMPERATURES MIXED IN OVER THE NYC METRO AND NEAR THE COAST TO MINIMIZE THE AMOUNT OF RADIATIONAL COOLING TYPICALLY OVER DONE IN GUIDANCE IN THESE TYPES OF SITUATIONS. LOWS THURSDAY NIGHT SHOULD BE AROUND 5-10 DEGREES ABOVE NORMAL. && .LONG TERM /FRIDAY THROUGH TUESDAY/... MODELS IN FAIRLY GOOD AGREEMENT TO START THE LONG TERM. SURFACE HIGH PRESSURE AND UPPER LEVEL RIDGE NEAR THE REGION WILL KEEP CONDITIONS DRY. TEMPERATURES AT H85 WILL BE 4-7C...SO EXPECT DAYTIME HIGH SURFACE TO BE ABOVE NORMAL FRIDAY AND SATURDAY. GOOD RADIATIONAL COOLING WILL BE LIKELY AT NIGHT...KEEPING SOME TEMPERATURES CLOSER TO NORMAL OR EVEN BELOW NORMAL AT NIGHT. A MOISTURE STARVED COLD FRONT IS THEN EXPECTED TO MOVE ACROSS THE REGION SATURDAY NIGHT. WE START TO SEE SOME 00Z MODEL DIFFERENCES FROM SUNDAY THROUGH TUESDAY. WHILE THERE ARE SOME DIFFERENCES...THEY HAVE STARTED TO COME INTO SOME BETTER AGREEMENT. THE GFS ALLOWS COLD AIR TO CONTINUE TO INFILTRATE THE CWA ON SUNDAY...WHEREAS THE ECMWF STALLS THE FRONT OVER THE REGION HALTING ANY COLD AIR ADVECTION. FOR MONDAY AND TUESDAY...BOTH MODELS DEVELOP LOW PRESSURE ALONG THE FRONT...WITH SOME DIFFERENCES IN BOTH TIMING AND STRENGTH OF THE LOWS. FOR NOW...WILL LIMIT POPS TO CHANCE WITH A CHANCE. P-TYPE WILL HEAVILY DEPEND ON THE STRENGTH AND PLACEMENT OF THE LOW. FOR NOW WILL KEEP RAIN PRIMARILY CLOSER TO THE COAST AND SOME RAIN/SNOW FURTHER INLAND WHERE TEMPERATURES WILL BE COOLER. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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***HIGH IMPACT EVENT TODAY*** A WARM FRONTAL BOUNDARY WAS SOUTH OF LONG ISLAND...THROUGH SOUTHERN NEW JERSEY AND CONTINUES TO MOVE SLOWLY NORTH. THE FRONT POSSIBLY PASSES THROUGH LATE THIS AFTERNOON. MEANWHILE A COLD FRONT ACROSS THE MIDWEST WILL BE APPROACHING THIS EVENING. THE COLD FRONT CROSSED THROUGH THE AREA FROM AROUND 10Z TO 15Z THURSDAY. IFR TO LIFR CONDITIONS EXPECTED UNTIL THE COLD FRONTAL PASSAGE. CONDITIONS IMPROVE QUICKLY TO VFR WITH THE RAIN ENDING AS THE FRONT MOVES THROUGH. LIGHT TO MODERATE RAIN CONTINUES WITH PERIODS OF HEAVIER RAIN LATER THIS AFTERNOON AND INTO THE EVENING. A RUMBLE OF THUNDER IS POSSIBLE THIS EVENING...MAINLY EAST OF THE NYC TERMINALS. WIND WILL BE EAST TO SOUTHEAST 10 TO 15 MPH THROUGH THE DAY. A LOW LEVEL JET STREAM OF 50 TO 60 KT MOVES INTO THE AREA FROM THE SOUTH WITH LOW LEVEL WIND SHEAR. THE LOW LEVEL WIND SHEAR REMAINS UNTIL THE COLD FRONTAL PASSAGE. .OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY... .THU...VFR. WESTERLY WIND 15-20G30-35KT. CHANCE OCCASIONAL GUSTS 35-40KT. .THU NIGHT...VFR. WIND AND GUSTS DIMINISHING. .FRI-SAT...VFR. .SUN-MON...MARGINAL VFR. CHANCE OF RAIN AND SNOW.
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&& .MARINE... WINDS INCREASE ON ALL WATERS TO SCA LEVELS DURING THE AFTERNOON - ALREADY HAVE SCA LEVEL SEAS ON THE COASTAL OCEAN WATERS - THEN LIKELY WILL HAVE GUSTS TO GALE FORCE DEVELOP THURSDAY MORNING AND CONTINUE INTO EARLY THURSDAY EVENING. SCA GUSTS THEN EXPECTED FOR THE REMAINDER OF THE EVENING...TAPERING OFF TO BELOW SCA LEVELS AFTER MIDNIGHT FOR ALL BUT THE COASTAL OCEAN WATERS EAST OF MORICHES INLET. MAINLY SUB-SCA CONDITIONS ARE EXPECTED ON THE AREA WATERS THROUGH MONDAY. THE ONLY EXCEPTIONS WILL BE IF THERE AREA ANY LEFT OVER SCA CONDITIONS INTO EARLY FRIDAY MORNING...AND AGAIN ON SATURDAY NIGHT AS A WEAK COLD FRONT COULD INCREASE SEAS TO NEAR 5 FT..MAINLY ON THE EASTERN WATERS. A SERIES OF LOW PRESSURE SYSTEMS COULD IMPACT THE AREA WATERS EARLY NEXT WEEK. && .HYDROLOGY... A STRONG LOW LEVEL JET COUPLED WITH PRECIPITABLE WATERS AROUND 1 1/2- 1 3/4 INCHES LATE THIS AFTERNOON AND MOST OF TONIGHT SHOULD YIELD AROUND AN ADDITIONAL 1 1/4 TO 2 INCHES OF RAIN WITH LOCALLY HIGHER AMOUNTS...THROUGH EARLY CHRISTMAS MORNING. THE MAIN THREAT FROM THIS IS MINOR URBAN AND POOR DRAINAGE FLOODING LIKELY. MINOR SMALL STREAM FLOODING IS POSSIBLE FOR A FEW OF THE FLASHIER SMALL RIVERS/STREAMS IN NE NJ/LOWER HUDSON VALLEY/AND SW CT...IF HIGHER RAINFALL AMOUNTS ARE REALIZED. WITH CONVECTIVE POTENTIAL WED NIGHT...AND 1 HR FLASH FLOOD GUIDANCE OF 3/4 TO ONE INCH IN THIS AREA...THERE IS A LOW PROBABILITY OF FLASH/AREAL FLOODING. NO SIGNIFICANT PRECIPITATION IS EXPECTED FRI-SATURDAY NIGHT. A SERIES OF LOW PRESSURE SYSTEMS IMPACT THE HYDROLOGIC SERVICE AREA SUNDAY THROUGH TUESDAY...BUT THE TRACK AND INTENSITY IS TOO UNCERTAIN TO DETERMINE HOW MUCH PRECIPITATION WILL FALL. && .TIDES/COASTAL FLOODING... MINOR COASTAL BENCHMARKS LIKELY BE TOUCHED OR JUST EXCEEDED AT LOCALIZED AREAS ALONG WESTERN LONG ISLAND SOUND AND THE SOUTHSHORE BAYS OF NYC AND NASSAU COUNTY DURING THE HIGH TIDE LATE THIS MORNING/THIS AFTERNOON. HAVE EXTENDED THE COASTAL FLOOD STATEMENT TO ADDRESS THIS THREAT. ONLY A LOW POTENTIAL FOR LOCALIZED MINOR FLOODING DURING TONIGHT/S HIGH TIDE FOR THE SOUTH SHORE BACK BAYS...WITH STRONG SOUTHERLY WINDS...AS 2 TO 2 1/2 FT SURGE NEEDED FOR MINOR FLOODING. && .CLIMATE... RECORD HIGHS FOR TODAY...DECEMBER 24 LOCATION.......RECORD/YEAR....FORECAST HIGH NEWARK.............64/1990..........58 BDRIDGEPORT........57/1990..........54 CENTRAL PARK.......63/1996*.........57 LAGUARDIA..........63/1990..........58 JFK AIRPORT........58/1990..........56 ISLIP AIRPORT......57/1990..........57 * = AND IN PREVIOUS YEARS NOTE ON MAXIMUM MINIMUM FOR TODAY...ALREADY HAVE HAD LOWS BELOW THE RECORDS FOR ALL BUT JFK (46 SET IN 2003). SO IF CURRENT EXPECTATIONS HOLD...SHOULD SET RECORDS THERE - BUT WILL NOT OFFICIALLY BE ABLE TO DETERMINE UNTIL MIDNIGHT TONIGHT. RECORD MAXIMUM MINIMUMS FOR CHRISTMAS DAY... LOCATION.......RECORD/YEAR NEWARK.............47/1979 BDRIDGEPORT........45/1964 CENTRAL PARK.......50/1979 LAGUARDIA..........48/1964 JFK AIRPORT........46/1987 ISLIP AIRPORT......45/1987 THESE RECORDS LIKELY WILL NOT FALL AS TEMPERATURES ARE CURRENTLY FORECAST TO FALL TO AROUND 40 DEGREES AT OR BEFORE 11:59 PM ON THE 25TH. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. NY...NONE. NJ...NONE. MARINE...GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR ANZ330-335-338-340-345-350-353-355. SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ330-335- 338-340-345. SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ350-353- 355.
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&& $$

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