Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211443 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1043 AM EDT THU MAY 21 2015 .SYNOPSIS... WEAK HIGH PRESSURE QUICKLY MOVES EAST TODAY...GIVING WAY TO LOW PRESSURE THAT PASSES TO THE SOUTH AND EAST TONIGHT. A COLD FRONT MOVES THROUGH LATE FRIDAY. HIGH PRESSURE BUILDS ACROSS THE AREA ON SATURDAY...THEN MOVES OFFSHORE EARLY SUNDAY. A WARM FRONT WILL THEN SLOWLY APPROACH FROM THE SOUTHWEST LATE SUNDAY THROUGH TUESDAY. THE FRONT MAY LIFT TO THE NORTH WEDNESDAY MORNING...AND BE FOLLOWED BY A COLD FRONT LATER WEDNESDAY INTO THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... FORECAST UPDATE TO INCLUDE SLIGHT CHANCE/CHANCE POPS CWA WIDE FOR SOME LIGHT RAINFALL TODAY. OTHERWISE...PLENTY OF MID AND HIGH LEVEL CLOUDS THIS MORNING OUT AHEAD OF UPSTREAM SHORTWAVE WILL LOWER AND THICKEN AS THE DAY PROGRESSES. CLOUDY CONDITIONS ARE ANTICIPATED. AT THE SFC...LOW PRESSURE OVER THE APPALACHIANS TO OUR SOUTH WILL MOVE TOWARD THE MID ATLANTIC COAST LATE TODAY AHEAD OF THE SHORTWAVE. HIGHEST POPS REMAIN ACROSS SOUTHWEST ZONES/COASTAL ZONES FROM NYC EAST WILL MAINTAIN CHANCE POPS DURING THE AFTERNOON...WITH A GENERAL LOWERING OF POPS AS YOU HEAD NORTHWARD. WITH PLENTY OF CLOUD COVER IN PLACE...TEMPS WILL STRUGGLE THROUGH THE 50S...AND INTO THE LOWER 60S. THIS IS BELOW NORMAL BY 5 TO 10 DEGREES...AND IS SUPPORTED BY LATEST MOS NUMBERS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... LARGE UPPER TROUGH/LOW PRESSURE OVER EASTERN CANADA...WITH SHORTWAVE ENERGY PIN-WHEELING AROUND THE CLOSED LOW...WILL PREVAIL THIS TIME FRAME. STRENGTHENING SHORTWAVE ROUNDING THE BASE OF THE LARGE UPPER TROUGH QUICKLY TRAVERSES FROM WEST TO EAST TONIGHT...PASSING TO THE EAST OF THE AREA EARLY FRIDAY MORNING. IN RESPONSE...SFC LOW OFF THE MID ATLANTIC COAST IS EXPECTED TO DEEPEN SLIGHTLY...LOWERING A FEW MILLIBARS...AS IT TRACKS SOMEWHERE JUST SOUTH AND EAST OF THE 40N/70W BENCHMARK TONIGHT INTO EARLY FRIDAY. IN FACT...CONSENSUS IS OBSERVED IN LATEST NAM/GFS/SREF MEAN AND ECMWF WITH HANDLING OF THIS LOW. PRECIP SHIELD EXTENDS NORTH AND WEST OF THIS SFC LOW...AND EXPANDS AHEAD OF THE AFOREMENTIONED SHORTWAVE. AS FOR POPS...WILL CONTINUE TO CARRY HIGH CHANCE TO LIKELY POPS NEAR THE COAST. THIS BASED ON ANALYSIS OF GFS AND NAM STATISTICAL MOS...NCEP MODEL PLAN FIELDS...AND SREF PLUMES. IN GENERAL...COASTAL LOCALES TONIGHT COULD OBSERVE ANYWHERE FROM AROUND A TENTH OF AN INCH ON AVERAGE. ACROSS NORTHERN ZONES SUCH AS THE LOWER HUDSON VALLEY AND SW CT...POPS REMAIN LOWER AND QPF WOULD RANGE FROM A TRACE TO MAYBE A TENTH OF AN INCH. ANY RAIN DEPARTS EARLY FRIDAY...WITH DRY WEATHER EXPECTED THROUGH THE MORNING. CLOUDS GIVE WAY TO BRIEF SUNSHINE. BY AFTERNOON...A COLD FRONT AHEAD OF DIGGING TROUGH APPROACHES LATE. CLOUDS INCREASE AGAIN...AND A FEW SHOWERS ARE POSSIBLE. NAM MOST AGGRESSIVE IN DEVELOPING AT LEAST SCATTERED COVERAGE DURING THE LATE AFTERNOON HOURS...BUT WILL LEAN TOWARD SREF/ECMWF/GFS AND ONLY FORECAST SLIGHT CHANCE POPS ATTM. A COOL NIGHT IS EXPECTED TONIGHT...WITH LOWS IN THE 40S TO LOWER 50S. WEST FLOW AND BRIEF WAA FRIDAY WILL RESULT IN NEAR TO PERHAPS SLIGHTLY ABOVE NORMAL TEMPS IN THE 70 TO 75 DEGREE RANGE. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... PLEASANT WEATHER CONDITIONS ARE EXPECTED FOR THE WEEKEND AS HIGH PRESSURE BUILDS ACROSS THE AREA ON SATURDAY...THEN OFFSHORE SUNDAY MORNING. HIGH TEMPERATURES ON SATURDAY WILL BE IN THE MID TO UPPER 60S AND LOW TO MID 70S ON SUNDAY. A WARM FRONT LIFTS NORTH ON MONDAY BRINGING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS. INSTABILITY SLOWLY INCREASES THROUGH THIS TIME...SO MENTIONED CHANCE THUNDER ON TUESDAY FROM NYC NORTH/WEST. THE WARM FRONT SHOULD LIFT TO THE NE BY WEDNESDAY MORNING...BUT COULD BE FOLLOWED BY A WEAK COLD FRONT OR PRE-FRONTAL WEDNESDAY AFTERNOON INTO THURSDAY MORNING...WITH CHANCE OF AFTERNOON SHOWERS AND THUNDERSTORMS ONCE AGAIN WEDNESDAY AND THURSDAY. TEMPERATURES WILL SLOWLY WARM UP DURING THE WEEK. WITH TEMPERATURES STARTING OUT IN THE LOW TO MID 70S ON MONDAY...THEN LOW TO MID 80S BY MIDWEEK. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... WEAK HIGH PRESSURE GIVES WAY TO LOW PRESSURE PASSING WELL SOUTH AND EAST OF LONG ISLAND THROUGH TONIGHT. EXPECTING MAINLY VFR CONDITIONS DESPITE SOME SCT SHWRS AND SPRINKLES THIS AFTN. MVFR CANNOT TOTALLY BE RULED OUT AT TIMES DURING THE LIGHT RAIN LATER TODAY AND THIS EVENING. WINDS WILL BECOME MORE SOUTHERLY AT 10-15 KT BEFORE RETURNING TO A MORE NORTHERLY FLOW LATE TONIGHT WHICH WILL AGAIN LOWER TO LESS THAN 10 KT. 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: HIGHER CHANCES FOR LIGHT RAIN AND MVFR AFTER 21Z. KLGA FCSTER COMMENTS: HIGHER CHANCES FOR LIGHT RAIN AND MVFR AFTER 21Z. TIMING OF MORE SOUTHERLY WIND COULD BE OFF BY 1-2 HOURS. KEWR FCSTER COMMENTS: HIGHER CHANCES FOR LIGHT RAIN AND MVFR AFTER 21Z. TIMING OF MORE SOUTHERLY WIND COULD BE OFF BY 1-2 HOURS. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: HIGHER CHANCES FOR LIGHT RAIN AND MVFR AFTER 23Z. TIMING OF MORE SOUTHERLY WIND COULD BE OFF BY 1-2 HOURS. KHPN FCSTER COMMENTS: HIGHER CHANCES FOR LIGHT RAIN AND MVFR AFTER 03Z. TIMING OF MORE SOUTHERLY WIND COULD BE OFF BY 1-2 HOURS. KISP FCSTER COMMENTS: HIGHER CHANCES FOR LIGHT RAIN AND MVFR AFTER 22Z. TIMING OF MORE SOUTHERLY WIND COULD BE OFF BY 1-2 HOURS. .OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY... .FRI-FRI NIGHT...POSSIBLE MVFR EARLY MORNING AND IN AFTERNOON. OTHERWISE VFR. NW GUSTS 25-30 KT...LOWERING AT NIGHT WITH GUSTS 15-20 KT. .SAT-SUN NIGHT...VFR. W GUSTS 15-20 KT DURING DAY SAT. SW GUSTS 15-25 KT DURING DAY SUN AND INTO EARLY SUN EVE. .MON...POSSIBLE MVFR OR LOWER IN RAIN SHOWERS. && .MARINE... HIGH PRESSURE BRIEFLY BUILDS ACROSS THE WATERS TODAY. AS SUCH...TRANQUIL WINDS AND SEAS ARE FORECAST. BY TONIGHT...THE HIGH DEPARTS AND LOW PRESSURE APPROACHES AND TRACKS SOUTH AND EAST OF THE WATERS. THIS LOW MOVES NORTHEAST AS A COLD FRONT APPROACHES FRIDAY AFTERNOON. LIGHT NORTHERLY WINDS TONIGHT INTO FRIDAY MORNING TURN TOWARD BACK TO THE WEST AND INCREASE DURING THE AFTERNOON. THERE COULD VERY WELL BE 25 TO PERHAPS 30 KT GUSTS NEAR SHORE LATE IN THE AFTERNOON...ESPECIALLY NY HARBOR AND WESTERN LI SOUND. WILL HOLD OFF THOUGH ON ANY ADVISORIES ATTM DUE TO LATE 3RD PERIOD...AND MAINLY A NEAR SHORE CONCERN. TRANQUIL SEAS TONIGHT BUILDS LATE FRIDAY AFTERNOON IN RESPONSE TO THE STRENGTHENING WESTERLY WINDS. TRANQUIL CONDITIONS ARE EXPECTED SATURDAY AND SUNDAY MORNING...AS HIGH PRESSURE BUILDS ACROSS THE AREA WATERS. SOUTHWEST FLOW INCREASING TO 15-20 KT MAY BUILD OCEAN SEAS TO 5 FT SUNDAY AFTERNOON/EVENING...ESPECIALLY FARTHER EAST WHERE A LONGER FETCH WILL EXIST. OCEAN SEAS FALL BELOW SCA LEVELS BRIEFLY ON MONDAY...THEN BUILD BACK TO SCA LEVELS ON TUESDAY. && .FIRE WEATHER... TODAY WILL REMAIN MAINLY CLOUDY AND COOL WITH LIGHT WINDS. SOME RAIN IS EXPECTED LATE TODAY AND THROUGH TONIGHT...MAINLY ALONG THE COAST. THEN...DRY WEATHER RETURNS FRIDAY. WEATHER CONDITIONS ON FRIDAY MAY STILL BE CONDUCIVE TO GROWTH/SPREAD OF ANY FIRES THAT DEVELOP. MIN RH ARE FORECAST TO BE IN THE 20S AND W-NW WINDS WILL GUST TO 25-30 MPH FRI AFTERNOON. KBDI IS IN THE 100S ACROSS MOST OF SRN CT AND THE LOWER HUDSON VALLEY AND IN THE 200S ACROSS NYC METRO AND LONG ISLAND...BUT MAY NOT BE FULLY REPRESENTATIVE OF THE PERSISTENT DRY CONDITIONS THAT HAVE BEEN IN PLACE. && .HYDROLOGY... DRY THROUGH THIS MORNING. THEN THERE IS THE POTENTIAL FOR AROUND A TENTH OF AN INCH OF RAIN ON AVERAGE NEAR THE COAST. NORTHERN ZONES SUCH AS THE LOWER HUDSON VALLEY AND SRN CT...QPF WOULD RANGE FROM A TRACE TO MAYBE A TENTH OF AN INCH. THERE IS A CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS MONDAY INTO THE MIDDLE OF THE WEEK. MODEL UNCERTAINTIES ON TIMING/PLACEMENT OF ANY HEAVY RAIN ARE STILL TOO LARGE TO MERIT MENTION OF SPECIFIC AMOUNTS...AND MAY NOT EVEN PAN PER MODEL FORECASTS OUT GIVEN THE PERSISTENT DRY PATTERN THAT HAS BEEN IN PLACE. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...FIG/PW NEAR TERM...BC/PW SHORT TERM...PW LONG TERM...FIG AVIATION...JMC/JM MARINE...FIG/PW FIRE WEATHER... HYDROLOGY...FIG/PW

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