Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 070807 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 407 AM EDT TUE JUL 7 2015 .SYNOPSIS...
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HIGH PRESSURE OFFSHORE GIVES WAY TO AN APPROACHING WARM FRONT TODAY. THE FRONT MOVES ACROSS TODAY WITH A COLD FRONT MOVING THROUGH WEDNESDAY. THE COLD FRONT STALLS TO OUR SOUTH WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...WITH WAVES OF LOW PRESSURE RIDING ALONG IT. WEAK HIGH PRESSURE BUILDS IN FRIDAY THROUGH SATURDAY...THEN SLOWLY SLIDES OFFSHORE SUNDAY. A WARM FRONT SLOWLY APPROACHES FROM THE WEST SUNDAY NIGHT AND MONDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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NOT TOO MUCH CHANGE WITH HEIGHT FIELDS...AND HENCE NOT MUCH SYNOPTIC FORCING TODAY. ON A LARGE SCALE...UPPER LEVEL TROUGH LIFTS BECOMING DIFFUSE. THE LARGER SIGNAL IS A STRONG UPPER LEVEL RIDGE STRETCHING FROM THE SOUTH CENTRAL U.S. UP ALONG THE EASTERN SEABOARD. THE RIDGE AXIS IS OFFSHORE AS WELL AS THE SURFACE HIGH PRESSURE CENTER. INITIALLY SOME LOW STRATUS AND PATCHY FOG IN THE MORNING WILL QUICKLY DISSIPATE WITH DIURNAL WARMING. A WARM FRONT IS EXPECTED TO MOVE ACROSS TODAY WITH ACCOMPANYING WINDS SHIFTING FROM SE TO S-SW...FURTHER BOOSTING WARM AIR ADVECTION. A MAV/MET/EKD BLEND YIELDS HIGH TEMPS WELL WITHIN THE 80S...UPPER 80S FOR URBAN NORTHEAST NJ. CONCERNING SHOWERS AND THUNDERSTORMS...LOW CHANCES IN THE MORNING WITH RELATIVELY HIGHER CHANCES IN THE AFTERNOON. PRECIPITABLE WATERS OF NEAR 1.6 TO 1.8 INCHES WILL ENABLE FOR LOCALLY HEAVY DOWNPOURS WITH THE HIGHER MOISTURE CONTENT OF THE ATMOSPHERE DERIVED FROM THE CONTINUED WARM AIR ADVECTION.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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FOR TONIGHT...INSTABILITY LOWERS WITH THE LOSS OF DIURNAL WARMING AND WITHOUT MUCH SYNOPTIC FORCING...ANY LEFTOVER SHOWERS OR THUNDERSTORMS WILL DECREASE...GRADUALLY DIMINISHING IN AREAL COVERAGE. STILL EXPECTING ANOTHER ROUND OF LATE NIGHT/EARLY MORNING LOW STRATUS OR PATCHY FOG WITHIN THE REGION. THEREFORE...USED MAV/MET/GMOS AND ADDED ONE FOR LOWS CONSIDERING THE CONTINUED WARM AIR ADVECTION. THE TEMPERATURES WILL BE VERY MILD AND WITH DEWPOINTS ALSO INCREASING...HUMIDITY WILL INCREASE AS WELL. FOR WEDNESDAY...AFTER ANOTHER ROUND OF PATCHY FOG OR LOW LEVEL STRATUS...ANOTHER VERY WARM DAY IN STORE. THE CORE OF THE WARMEST AIR AT 850MB MOVES ACROSS WITHIN THE FIRST HALF OF THE DAY AND THEN LOWERS SLIGHTLY FOR THE REMAINDER OF THE DAY. THESE 850MB TEMPS WILL BE REACHING UP TO NEAR 18 DEGREES C. HIGHS AT THE SURFACE WELL INTO THE 80S AND NEAR 90 FOR PORTIONS OF NYC AND NORTHEAST NJ AS DAYTIME MIXING OCCURS WITHIN THE BOUNDARY LAYER. REGARDING THE SHOWERS AND THUNDERSTORMS...OVERALL HIGHER CHANCES WEDNESDAY DUE TO THE COLD FRONT MOVING ACROSS THE REGION PLUS SOME ADDITIONAL POSITIVE VORTICITY ADVECTION AT 500MB AS WELL AS AN APPROACHING JET STREAK AT 250MB. THE JET STREAK WILL BE WELL NORTH OF THE REGION BUT A LITTLE MORE IN THE WAY OF SHEAR WILL BE SEEN AND THIS SHOULD PROVIDE A LITTLE MORE ORGANIZATION FOR THUNDERSTORMS. HIGH PW VALUES AGAIN WITH FORECAST READINGS APPROACHING NEAR 2 INCHES SO HEAVY DOWNPOURS WILL BE A POSSIBILITY WITH ANY THUNDERSTORMS THAT DEVELOP. HIGHEST LIKELIHOOD N/W OF NYC WITH REGARDS TO CONVECTION.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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THE TRI-STATE WILL EXPERIENCE UNSETTLED WEATHER WEDNESDAY NIGHT INTO THURSDAY NIGHT WITH A FRONTAL BOUNDARY STALLED OUT JUST TO THE S AND MULTIPLE SHORTWAVES PASSING ALOFT. WEDNESDAY NIGHT SHOULD SEE THE BEST CHANCE FOR ANY EVENING SHOWERS AND TSTMS/OVERNIGHT SHOWERS OVER THE S 1/2 OF THE CWA CLOSER TO THE FRONT. POPS INCREASE TO CHANCE EVERYWHERE THURSDAY AND REMAIN SO INTO THURSDAY EVENING IN RESPONSE TO THE PASSING OF TWO DISTINCT 700-500 HPA SHORTWAVES. PRECIPITATION SHOULD TAPER OFF FROM W TO E LATE THURSDAY NIGHT AS THE LAST SHORTWAVES EXITS TO THE NE. WITH CAPE FORECAST TO BE MINIMAL AFTER WEDNESDAY EVENING...THROUGH THURSDAY NIGHT...LIMITED THUNDER POTENTIAL TO SLIGHT CHANCE FROM LATE WEDNESDAY NIGHT INTO THURSDAY NIGHT. THIS CORRESPONDS TO TIMES WHEN SHOWALTER INDICES WHERE GENERALLY AT OR BELOW 2 REFLECTING THE POTENTIAL FOR ELEVATED CONVECTION. THE NAM/ECMWF/CMC ALL SUGGEST THAT THE HEAVIEST RAINFALL SHOULD OCCUR WITH THE LAST SHORTWAVE THURSDAY AFTERNOON/EVENING...TOO SOON TO LATCH ONTO SUCH SPECIFICS...BUT WITH PRECIPITABLE WATERS FORECAST TO BE BETWEEN 2-2.25 INCHES WILL HAVE TO MONITOR FOR THAT POTENTIAL. REFER TO THE HYDROLOGY SECTION OF THE AFD FOR POTENTIAL IMPACTS FROM ANY RAINFALL WEDNESDAY NIGHT-THURSDAY NIGHT. FOR LOWS WEDNESDAY NIGHT USED A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES. LOWS SHOULD BE NEAR TO SLIGHTLY ABOVE NORMAL. A BLEND OF MAV/MET GUIDANCE...NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 950 HPA PER BUFKIT SOUNDINGS WAS USED FOR HIGHS ON THURSDAY...WITH READINGS 5-10 DEGREES BELOW NORMAL DUE TO CLOUD COVER AND EXPECTED RAINFALL. A BLEND OF MEX/MEN/EKD/ECE/ECM/WPC GUIDANCE AND NAM 2-METER TEMPERATURES WAS USED FOR LOWS THURSDAY NIGHT...WITH VALUES FORECAST TO BE NEAR TO SLIGHTLY BELOW NORMAL. THE REGION WILL BE UNDER WNW-NW FLOW ALOFT FRIDAY-MONDAY IN BETWEEN A MEAN TROUGH LOCATED OVER SE CANADA AND A CLOSED HIGH THAT SLOWLY RETROGRADES FROM THE DEEP SOUTH BACK TOWARDS THE TEXAS PANHANDLE/NEW MEXICO BY EARLY NEXT WEEK. WITH NO SHORTWAVES CURRENTLY FORECAST TO IMPACT THE AREA FRIDAY- SATURDAY NIGHT HAVE GONE WITH A DRY FORECAST IN THIS TIME FRAME. FROM SUNDAY-MONDAY HAVE SLIGHT CHANCE POPS TO REFLECT THE POSSIBILITY THAT SHORTWAVES GOING OVER THE TOP OF THE CENTRAL PLAINS RIDGE COULD IMPACT THE AREA. HOWEVER...MODELS HAVE GREAT DIFFICULTY WITH THE TIMING AND STRENGTH OF SHORTWAVES IN PATTERNS LIKE THIS...SO THIS IS ANOTHER REASON WHY CONFIDENCE IN ANY PARTICULAR SOLUTION IS LOW IN THIS TIME FRAME. FOR TEMPERATURES FRIDAY-MONDAY USED A BLEND OF MEX/MEN/EKD/ECE/ECM/WPC GUIDANCE...WITH VALUES GENERALLY EXPECTED TO BE NEAR TO SLIGHTLY ABOVE NORMAL.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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A WARM FRONT APPROACHES FROM THE SOUTHWEST AND LIFTS NORTH OF THE REGION TODAY. EARLY THIS MORNING...MVFR CONDITIONS LOWER TO IFR IN LOW STRATUS AND FOG. SOME LIFR CONDITIONS POSSIBLE. CHANCE OF SHOWERS FROM 13Z-20Z TODAY...ESPECIALLY ALONG AND WEST OF A KLGA-KSWF LINE. CHANCE OF THUNDER IS ALSO POSSIBLE...HOWEVER CHANCES ARE TOO LOW TO INCLUDE IN THE TAF AT THIS TIME. WINDS WILL BE OUT OF THE SE...GENERALLY 10 KT OR LESS THROUGH MIDDAY. THIS AFTERNOON...SOME GUSTS INTO THE TEENS OR EVEN LOWER 20 KT POSSIBLE EAST OF NYC. ...NY METRO ENHANCED AVIATION WEATHER SUPPORT... DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS CAN BE FOUND AT: HTTP://WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE) KJFK FCSTER COMMENTS: AMENDMENTS MAY BE NEEDED EARLY THIS MORNING FOR CHANGES IN FLIGHT CATEGORIES DUE TO LOW STRATUS AND FOG. AMENDMENTS MAY BE NEEDED LATE THIS MORNING AND EARLY AFTERNOON FOR TIMING OF ANY THUNDERSTORMS. OCCASIONAL WIND GUSTS POSSIBLE THIS AFTERNOON TO 20 KT. KLGA FCSTER COMMENTS: AMENDMENTS MAY BE NEEDED EARLY THIS MORNING FOR CHANGES IN FLIGHT CATEGORIES DUE TO LOW STRATUS AND FOG. AMENDMENTS MAY BE NEEDED LATE THIS MORNING AND EARLY AFTERNOON FOR TIMING OF ANY THUNDERSTORMS. KEWR FCSTER COMMENTS: AMENDMENTS MAY BE NEEDED EARLY THIS MORNING FOR CHANGES IN FLIGHT CATEGORIES DUE TO LOW STRATUS AND FOG. AMENDMENTS MAY BE NEEDED LATE THIS MORNING AND EARLY AFTERNOON FOR TIMING OF ANY THUNDERSTORMS. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS YELLOW...WHICH IMPLIES SLANT RANGE VISIBILITY 4-6SM OR GREATER OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: AMENDMENTS MAY BE NEEDED EARLY THIS MORNING FOR CHANGES IN FLIGHT CATEGORIES DUE TO LOW STRATUS AND FOG. AMENDMENTS MAY BE NEEDED LATE THIS MORNING AND EARLY AFTERNOON FOR TIMING OF ANY THUNDERSTORMS. KHPN FCSTER COMMENTS: AMENDMENTS MAY BE NEEDED EARLY THIS MORNING FOR CHANGES IN FLIGHT CATEGORIES DUE TO LOW STRATUS AND FOG. AMENDMENTS MAY BE NEEDED LATE THIS MORNING AND EARLY AFTERNOON FOR TIMING OF ANY THUNDERSTORMS. KISP FCSTER COMMENTS: AMENDMENTS MAY BE NEEDED EARLY THIS MORNING FOR CHANGES IN FLIGHT CATEGORIES DUE TO LOW STRATUS AND FOG. AMENDMENTS MAY BE NEEDED LATE THIS MORNING AND EARLY AFTERNOON FOR TIMING OF ANY THUNDERSTORMS. .OUTLOOK FOR 06Z WED THROUGH SAT... .TUE NIGHT...MVFR/IFR CONDITIONS POSSIBLE. .WED...SHRA/TSTMS POSSIBLE WITH MVFR OR LOWER CONDITIONS AT TIMES. .THU-FRI...CHANCE OF SHOWERS WITH MVFR OR LOWER CONDITIONS AT TIMES. .SAT...VFR.
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&& .MARINE...
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SEAS CURRENTLY ON THE OCEAN AT NEAR 2 FT. WAVEWATCH IS PREDICTING 3 FT FOR THE SAME TIME. THEREFORE THIS POSITIVE BIAS IN THE WAVE HEIGHT WAS TAKEN INTO ACCOUNT FOR THE FORECAST. BASICALLY 2 TO 3 FT SEAS TODAY AND A LONG FETCH DURATION OF SOUTHERN FLOW WILL BUILD SEAS UP TO 4 FT BY LATE TONIGHT. WINDS WITHIN THE BOUNDARY LAYER INCREASE AS WELL BUT WITH WARM AIR ADVECTING ALOFT...WILL HAVE DIFFICULTY MIXING DOWN TO THE SURFACE ESPECIALLY TONIGHT. THEREFORE GUSTS WILL BE CLOSER TO 20 KT WITH ANY 25 KT GUSTS BEING OCCASIONAL. HENCE...SCA CONDITIONS ARE NOT EXPECTED TO BE MET. IT IS NOT TOTALLY OUT OF THE QUESTION BUT DID NOT HAVE ENOUGH CONFIDENCE WITH THESE MARGINAL CONDITIONS TO HOIST SCA WITH THIS FORECAST. NEARLY THE SAME CONDITIONS PERSIST INTO WEDNESDAY BUT CONTINUING TO STAY BELOW SCA. A RELAXED PRESSURE GRADIENT OVER THE REGION WEDNESDAY NIGHT-SATURDAY SHOULD KEEP WINDS TO 10 KT OR LESS OVER ALL WATERS. SEAS WILL BE 1 FT OR LESS ON THE NON-COASTAL OCEAN WATERS AND 4 FT OR LESS ON THE COASTAL OCEAN WATERS AS A RESULT WEDNESDAY NIGHT-SATURDAY.
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&& .HYDROLOGY...
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SUMMER CONVECTION IS FORECAST FOR TODAY AND WEDNESDAY (MORE LIKELY) AFTERNOONS. WITH PRECIPITABLE WATER VALUES NEAR 2 INCHES...HEAVY RAINFALL IS POSSIBLE. WITH THE CONVECTION ALSO BEING RATHER SLOW MOVING...LOCALIZED URBAN AND POOR DRAINAGE FLOODING COULD OCCUR...WITH A LOW PROBABILITY OF FLASH FLOODING. PRECIPITABLE WATERS WEDNESDAY NIGHT ARE FORECAST TO BE AROUND 1.75-2 INCHES AND INCREASE TO AROUND 2-2.25 BY AROUND MIDDAY THURSDAY AND CONTINUE TO REMAIN HIGH INTO THURSDAY EVENING. AS A RESULT THERE IS THE POTENTIAL FOR LOCALLY HEAVY RAINFALL WITH ANY STRONGER CONVECTION WEDNESDAY NIGHT-THURSDAY EVENING. THERE IS SOME INDICATION THOUGH THAT THERE COULD BE SOME ORGANIZATION OF THE CONVECTION...MAKING THE POTENTIAL FOR HEAVY RAINFALL MORE WIDESPREAD. WHILE IT IS TOO EARLY TO SPECIFY ANY RAINFALL AMOUNTS...THERE IS THE POTENTIAL FOR AT LEAST MINOR URBAN/POOR DRAINAGE FLOODING WEDNESDAY NIGHT...WITH A LOW CHANCE OF FLASH FLOODING AS WELL THURSDAY/THURSDAY EVENING. WILL HIGHLIGHT THE THREAT OF FLASH FLOODING CWA WIDE IN THE HWO.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...JM/MALOIT NEAR TERM...JM SHORT TERM...JM LONG TERM...MALOIT AVIATION...BC MARINE...JM/MALOIT HYDROLOGY...JM/MALOIT

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