Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 170601 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 201 AM EDT FRI APR 17 2015 .SYNOPSIS... HIGH PRESSURE CONTINUES TO MOVE OFFSHORE TONIGHT. A WEAK COLD FRONT APPROACHES FROM THE GREAT LAKES FRIDAY...AND THEN PASSES THROUGH FRIDAY EVENING. HIGH PRESSURE BUILDS ACROSS THE AREA SATURDAY...THEN MOVES OFFSHORE SUNDAY NIGHT. A COASTAL LOW WILL THEN IMPACT THE LOCAL AREA MONDAY INTO TUESDAY. HIGH PRESSURE BEGINS TO BUILD TOWARD THE AREA ON WEDNESDAY...WITH ANOTHER COLD FRONT MOVING ACROSS WEDNESDAY NIGHT AND THURSDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... FORECAST REMAINS ON TRACK. AGAIN...JUST SOME SLIGHT ADJUSTMENTS TO TEMPERATURES AND DEWPOINTS TO BETTER MATCH OBSERVED TRENDS. HIGH PRESSURE WILL CONTINUE TO BUILD FARTHER OFFSHORE TONIGHT AS LOW-LEVEL WINDS BECOME MORE SOUTHERLY. THIS WILL ALLOW BOTH ATLANTIC AND GULF MOISTURE TO STREAM NORTHWARD AHEAD OF SHORT WAVE TROF AND WEAK COLD FRONT OVER THE GREAT LAKES. WARM ADVECTION PRECEDING THE FRONT WILL ALLOW FOR INCREASING CLOUDS THIS EVENING WITH RAIN LIKELY BREAKING OUT IN THE PRE-DAWN HOURS FROM WEST TO EAST. THE 12Z GFS AND NAM BOTH DEVELOP A WEST TO EAST ORIENTED RAIN AXIS WITH A QUARTER TO HALF AN INCH. THE DIFFERENCE ARISES IN PLACEMENT WITH THE NAM ACROSS NYC METRO/LI...AND THE GFS FARTHER NORTH ACROSS THE INTERIOR. THE 12Z ECMWF GENERATES A MORE UNIFORM...LIGHTER RAINFALL EVENT. PREFERENCE IS TOWARD THE LATTER DUE TO WEAK LIFT AND INSTABILITY. OVERNIGHT LOWS WILL RANGE FROM THE MID 40S INLAND TO THE LOWER 50S NYC METRO. THIS IS ABOUT 5 TO 8 DEGREES ABOVE NORMAL. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... RAIN ENDS BY EARLY FRI AFT FROM WEST TO EAST. THERE MAY BE A FEW INSTABILITY SHOWERS ACROSS NRN NJ AND THE LOWER HUDSON VALLEY IN THE AFT DUE TO LINGERING INSTABILITY AND DAYTIME HEATING. GENERALLY LOOKING FOR A QUARTER INCH OR LESS FOR THE EVENT. HIGHS WILL TOP OUT IN THE LOW TO MID 60S...WHICH IS A FEW DEGREES ABOVE NORMAL. SKIES WILL CLEAR FROM NW TO SE DURING THE AFT AND EARLY EVENING HOURS. SFC FRONT OR WEAK TROF MOVES THROUGH IN THE EVENING WITH A LIGHT NW FLOW IN ITS WAKE. LOWS WILL BE SLIGHTLY COOLER THAN THE PREVIOUS NIGHT...BUT STILL A FEW DEGREES ABOVE NORMAL. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... DRY AND SEASONABLE CONDITIONS ARE EXPECTED OVER THE WEEKEND...AS HIGH PRESSURE BUILDS INTO THE AREA SATURDAY...THEN MOVES OFFSHORE SUNDAY NIGHT. A COASTAL LOW WILL THEN MAKE ITS WAY UP THE COAST AND IMPACT THE LOCAL AREA MONDAY AND TUESDAY. THIS LOW HAS THE POTENTIAL TO PRODUCE ONE TO TWO INCHES OF RAINFALL AS IT INTERACTS WITH A TROPICAL MOISTURE PLUME STREAMING NORTHWARD UP THE COAST. ELEVATED THUNDER IS POSSIBLE LATE MONDAY EVENING. RAIN TAPPERS OFF TUESDAY EVENING AS THE LOW PRESSURE MOVES EAST OF THE AREA. HIGH PRESSURE BRIEFLY RETURNS LATE TUESDAY INTO WEDNESDAY...WITH ANOTHER SYSTEM APPROACHING FROM THE WEST WEDNESDAY NIGHT AND THURSDAY. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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WEAK COLD FRONT APPROACHES TODAY AND PASSES THROUGH THIS EVENING. VFR UNTIL 12-14Z...THEN MVFR. CHC TEMPO IFR CIGS FROM APPROX 14-16Z...BUT CONFIDENCE OF THIS OCCURRING IS NOT HIGH ENOUGH TO INCLUDE IN TAFS. -SHRA ALSO MIGHT NOT OCCUR FROM APPROX 13Z- 19Z...WITH POSSIBLE -SHRA DEVELOPMENT LATE THIS AFTN. MODERATE TO HIGH CONFIDENCE IN WIND FCST THRU THIS MORNING. CONFIDENCE LOWERS THIS AFTN. KJFK COULD BE CLOSER TO AVERAGING 190-180 MAG THIS AFTN AND COULD OCCASIONALLY GUST TO 20 KT. .OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY... .FRI NGT...VFR. .SAT...VFR. SFC WND NW 10-15KT INCREASING WITH G25-30KT LATE AFTN. .SUN...VFR. SFC WND LIGHT NE BECOMING SE 10-15 IN THE AFTN. .MON...MVFR BECOMING IFR. INCREASING ESE SFC WND. G35KT IN AFTN. .TUE...MVFR BECOMING VFR.
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&& .MARINE... HIGH PRESSURE CONTINUES TO MOVE OFFSHORE TONIGHT. A WEAK COLD FRONT APPROACHES THE WATERS FRIDAY WITH A STRENGTHENING SLY FLOW. A FEW WIND GUSTS MAY APPROACH 25 KT ON THE OCEAN WATERS FRI...AND 20 KT ELSEWHERE. SEAS WERE CAPPED ON THE OCEAN AT 4 FT AS WAVEWATCH GUIDANCE APPEARS TO BE OVERDONE IN THE S FLOW AT THE OCEAN SFC, NOT ENOUGH CONFIDENCE IN A WIDESPREAD SCA EVENT TO GO WITH ONE AT THIS POINT. SUB-SCA CONDITIONS ON THE AREA WATERS SATURDAY AND SUNDAY. SEAS BUILD TO SCA CONDITIONS ON MONDAY AS A COASTAL LOW MOVES UP THE COAST...WITH WINDS INCREASING OUT OF THE SE-S WITH GUSTS UP TO 30 KT. SEAS REMAIN ABOVE SCA CONDITIONS THROUGH TUESDAY. HIGH PRESSURE BRIEFLY BUILDS ACROSS THE AREA WATERS ON WEDNESDAY...ALLOWING SEAS TO FALL BACK TO BELOW SCA CONDITIONS. && .FIRE WEATHER... DRY WEATHER...MINIMUM RELATIVE HUMIDITY VALUES POSSIBLY BELOW 30 PERCENT AND A TIGHTENING PRESSURE GRADIENT THAT MIGHT PRODUCE GUSTY N/NW WINDS ACROSS THE AREA...COULD INCREASE FIRE WEATHER CONCERNS ON SATURDAY. && .HYDROLOGY... AROUND A QUARTER OF AN INCH OF RAIN IS EXPECTED LATE TONIGHT THROUGH FRIDAY. THERE IS STILL THE POTENTIAL FOR MORE SIGNIFICANT RAINFALL WITH AN APPROACHING FRONTAL SYSTEM MONDAY INTO TUESDAY. STORM TOTAL RAINFALL AT THIS TIME IS BETWEEN 1 TO 1.5 INCHES...WITH LOCALLY HIGHER AMOUNTS UP TO 2 INCHES POSSIBLE. FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEB SITE. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ AVIATION...JC

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