Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 271959 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 359 PM EDT FRI MAR 27 2015 .SYNOPSIS...
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A DEEP UPPER TROUGH WILL PUSH ACROSS THE REGION TONIGHT THROUGH SATURDAY. MEANWHILE...LOW PRESSURE OVER THE MID-ATLANTIC WILL TRACK TOWARDS THE CANADIAN MARITIMES ON SATURDAY. HIGH PRESSURE THEN BUILDS INTO THE REGION SATURDAY NIGHT INTO SUNDAY...FOLLOWED BY A SERIES OF FRONTAL SYSTEMS THAT WILL IMPACT THE AREA THROUGH THE UPCOMING WEEK.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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SOME MID-LEVEL SHORTWAVE ENERGY...AS WELL AS A SFC LOW PRES EAST OF THE 40/70 BENCHMARK...WILL TRACK TO THE NORTHEAST TONIGHT. ANY LIGHT...LINGERING SHOWERS...MAINLY ACROSS NYC/LONG ISLAND...WILL TAPER OFF THIS EVENING. MEANWHILE...A DEEP UPPER TROUGH WITH SEVERAL STRONG H5 SHORTWAVES WILL CONTINUE TO SLOWLY PUSHING INTO THE OHIO VALLEY AND TRACK TO THE EAST. ANOTHER SFC LOW...CURRENTLY OVER THE CAROLINAS...WILL BEGIN TO TRACK TO THE NORTHEAST...AND THIS INTERACTION WILL PRODUCE SHOWERS ACROSS THE REGION TONIGHT. PRIOR TO MIDNIGHT... TEMPS WILL BE WARM ENOUGH FOR PRECIP TO BE RAIN. AFTER MIDNIGHT... THERMAL PROFILES FALL BELOW FREEZING ACROSS THE CWA...AND PRECIP WILL MIX WITH AND CHANGE TO SNOW. THE BULK OF THE SNOW WILL FALL OVER EXTREME SOUTHEAST CT AND THE TWIN FORKS OF LONG ISLAND... WHERE THE BEST FORCING WILL OCCUR...AND 1/4 TO 1/2 INCH SNOW POSSIBLE BY DAYBREAK SATURDAY. LOWS TONIGHT WILL RANGE FROM THE UPPER 20S TO LOW 30S.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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UNSEASONABLY COLD AIRMASS SPREADS EAST FOR THE WEEKEND. WITH 850 MB TEMPS FROM -10C TO -12C AND 1000-500 MB THICKNESSES WILL FALL TO 515-520 DAM DURING THE DAY SATURDAY. THIS WILL SET UP CONDS FOR WINTRY WEATHER FOR MOST OF THE DAY. UPPER TROUGH SLOWLY MOVES EAST DURING THE DAY SATURDAY...AND THEN A CLOSED UPPER LOW WILL CUT OFF OVER THE NORTHEAST BY SATURDAY EVENING. MEANWHILE...SFC LOW OFFSHORE WILL CONTINUE TO TRACK TOWARDS THE CANADIAN MARITIMES DURING THE DAY...AND DEPARTS BY SATURDAY EVENING. AS THE LOW PASSES EAST OF CAPE COD...IT WILL FORM AN INVERTED TROUGH THAT WILL EXTEND BACK TOWARDS EASTERN CT AND EASTERN LONG ISLAND. OPERATIONAL MODELS ARE IN GOOD AGREEMENT WITH THIS OCCURRING...AND ARE INDICATING SOME BANDING THERE. WILL GO AHEAD AND BUMP UP POPS TO LIKELY/CATEGORICAL FOR THE FAR EASTERN ZONES...AND CURRENTLY EXPECTING ABOUT 1-3 INCHES OF SNOW BY SATURDAY EVENING. DO NOT THINK A WINTER WEATHER ADVISORY IS NEEDED...BUT SOME SPOTS COULD PICK UP CLOSE TO 3 INCHES ACROSS NEW LONDON COUNTY. OTHERWISE...SNOWFALL TOTALS SHOULD AVERAGE 1-2 INCHES. PRECIP TAPERS OFF SATURDAY EVENING AS INVERTED TROUGH MOVES INTO THE OPEN ATLANTIC WATERS AND CLOSED LOW/UPPER TROUGH TRACK EAST. MOST PRECIP SHOULD BE OVER BY DAYBREAK SUNDAY...AND ANY ADDITIONAL PRECIP OVER EASTERN ZONES SATURDAY EVENING WILL BE LIGHT. TEMPERATURES WILL BE ABOUT 15 DEGREES BELOW NORMAL WITH HIGHS GENERALLY IN THE MID 30S TO AROUND 40. LOWS SATURDAY NIGHT WILL BE QUITE COLD...RANGING FROM THE MID TEENS INLAND TO THE MID 20S NEAR THE COAST.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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A PROGRESSIVE...YET AMPLIFIED FLOW IS BEING ADVERTISED BY THE GLOBAL MODELS THROUGH NEXT WEEK. INITIALLY...A SERIES OF FAST MOVING PAC SYSTEMS RIDE OVER TOP THE RIDGE OVER WESTERN NORTH AMERICA... DROPPING SE ACROSS CENTRAL CANADA AND INTO THE NE QUARTER OF THE NATION. HOWEVER...TOWARD THE END OF THE WEEK...THERE ARE TIMING AND MAGNITUDE DIFFERENCES WITH PAC ENERGY MOVING INTO THE WEST COAST OF THE LOWER 48. THE 12Z ECMWF FOCUSES ON A TRAILING SECOND PIECE OF ENERGY...THUS SLOWING DOWN THE FRONTAL SYSTEM AT THE END OF NEXT WEEK. FOR THE TIME...WILL MAINTAIN A LOW CHANCE OF RAIN SHOWERS THU AND FRI WITH THE POSSIBILITY THAT THIS SYSTEM MAY BE SLOWER THAN CURRENTLY ADVERTISED. THE OTHER SYSTEM THAT MAY BE NOTEWORTHY IS A CLIPPER LOW THAT THE 12Z GFS TAKES JUST NORTH OF NYC AND LI TUE NIGHT...WHILE THE ECMWF IS SIGNIFICANTLY FARTHER SOUTH EMERGING OFF THE MID ATLANTIC COAST. THE LATTER SCENARIO HAS SOME SUPPORT FROM THE GEFS. THIS COULD RAISE CONCERNS FOR SOME WINTRY WEATHER...ESPECIALLY INLAND. FOR NOW..GOING WITH AN ALL RAIN FORECAST BASED ON CLIMO AND MODEL UNCERTAINTY. A MUCH WEAKER COLD FRONT WILL MOVE THE AREA MON WITH PERHAPS A FEW SHOWERS. AFTER AN UNSEASONABLY COLD START ON SUN WITH HIGHS 40 TO 45...BOTH HIGHS AND LOWS WILL REBOUND TO NEAR SEASONABLE LEVELS. THE ONE CAVEAT IS A FARTHER SOUTH STORM TUE NIGHT INTO WED.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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WEAK HIGH PRESSURE WILL GRADUALLY BUILD IN THROUGH THIS EVENING WHILE AN UPPER LEVEL DISTURBANCE SLIDES ACROSS. SURFACE LOW PRESSURE WILL THEN DEVELOP OFF THE COAST LATE TONIGHT AND PASS WELL TO THE SOUTHEAST ON SATURDAY. ANOTHER UPPER LEVEL DISTURBANCE AND WEAK SURFACE LOW PRESSURE TROUGH WILL MOVE ACROSS ON SATURDAY. DIFFICULT FORECAST FOR NYC METRO LATE THIS AFTERNOON AND EVENING. WEAK HIGH PRESSURE WILL BE BUILDING IN...BUT THE PASSING UPPER LEVEL DISTURBANCE IS LIKELY TO BRING ABOUT MOSTLY MVFR CIGS DURING THIS TIME. CIGS SHOULD LIFT BY LATE EVENING...THEN EXPECT ANOTHER ROUND OF MVFR CIGS AND ISOLD-SCT SNOW SHOWERS SAT MORNING. EXCEPTION TO THE ABOVE WILL BE AT KGON...WHICH SHOULD MAINTAIN MVFR CIGS INTO TONIGHT...THEN IS LIKELY TO SEE SOME LIGHT SNOW LATE TONIGHT INTO SAT MORNING...WITH RUNWAY ACCUMULATION OF 1-3 INCHES POSSIBLE. NNW WINDS GENERALLY LESS THAN 10 KT INTO MOST OF TONIGHT WILL INCREASE TO 10-15 KT WITH GUSTS EITHER SIDE OF 20 KT LATE TONIGHT INTO SAT MORNING AS THE OFFSHORE LOW DEVELOPS. ...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: OCNL VFR CIGS POSSIBLE LATE THIS AFTERNOON AND EVENING. KLGA FCSTER COMMENTS: OCNL VFR CIGS POSSIBLE LATE THIS AFTERNOON AND EVENING. KEWR FCSTER COMMENTS: OCNL VFR CIGS POSSIBLE LATE THIS AFTERNOON AND EVENING. KTEB FCSTER COMMENTS: OCNL VFR CIGS POSSIBLE LATE THIS AFTERNOON AND EVENING. KHPN FCSTER COMMENTS: OCNL VFR CIGS POSSIBLE LATE THIS AFTERNOON AND EVENING. KISP FCSTER COMMENTS: UNSCHEDULED AMD NOT EXPECTED. .OUTLOOK FOR 18Z SAT THROUGH TUE... .SAT AFTERNOON...CHANCE OF MVFR CONDS WITH ANY RAIN OR SNOW SHOWERS. NW WINDS G20KT. .SAT NIGHT...CHANCE OF MVFR CONDS WITH ANY SNOW OR RAIN SHOWERS... MAINLY IN THE EVENING. NW WINDS G20-25KT. .SUNDAY...VFR. .MON...VFR. W WINDS G20KT. .TUE...VFR. .TUE NIGHT...CHANCE OF MVFR CONDS WITH ANY RAIN SHOWERS. .WED...VFR.
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&& .MARINE...
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ROUGH SEAS WILL PERSIST ON THE OCEAN WATERS TONIGHT THROUGH SATURDAY MORNING...AND THEN AS LOW PRES PASSES EAST OF CAPE COD ON SATURDAY...THE NW GRADIENT WILL TIGHTEN UP...AND CAN EXPECT SCA GUSTS TO DEVELOP ON THE OCEAN ON SATURDAY...AND THEN ON ALL WATERS BY SATURDAY EVENING. WILL GO AHEAD AND HOIST SMALL CRAFT ADVISORIES FOR ALL NON OCEAN WATERS BY SATURDAY EVENING AND LASTING THROUGH SATURDAY NIGHT. WAVES DIMINISH TO SUB SCA ON SUNDAY...BUT BUILD TO ABOVE SCA CRITERIA ON A SOUTHERLY FLOW LATE SUNDAY NIGHT INTO MONDAY AHEAD OF AN APPROACHING WARM FRONT. WINDS MAINLY OVER THE OCEAN WATERS WILL GUST TO 25 KT LATE SUNDAY NIGHT INTO MONDAY NIGHT. WINDS AND WAVES WILL DIMINISH ON TUESDAY AS THE PRESSURE GRADIENT RELAXES WITH WEAK HIGH PRESSURE BUILDING IN. THERE IS THE POTENTIAL FOR MARGINAL SCA CONDITIONS TUE NIGHT INTO WED MORNING DEPENDING ON THE TRACK AND INTENSITY OF LOW PRESSURE NEAR THE WATERS. LEANING TOWARD SUB-SCA CONDITIONS AT THIS TIME.
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&& .HYDROLOGY...
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1/10 TO 1/4 INCH LIQUID EQUIVALENT POSSIBLE TONIGHT THROUGH SATURDAY NIGHT...WITH EASTERN CT AND EASTERN LONG ISLAND POSSIBLY PICKING UP CLOSE TO 1/3 INCH QPF. FOR MOST AREAS...PRECIP WILL FALL EITHER AS SNOW OR A RAIN/SNOW MIX...AND 1-3 INCHES OF SNOW IS POSSIBLE FOR EASTERN CT AND EASTERN LONG ISLAND SATURDAY AFTERNOON AND EVENING. NO SIGNIFICANT WIDESPREAD PRECIPITATION EXPECTED THROUGH THIS WEEKEND INTO NEXT WEEK. RIVERS AND STREAMS ARE EXPECTED TO REMAIN BELOW BANK FULL...BUT INCREASED RIVER/STREAM FLOW ACROSS THE LOWER HUDSON VALLEY AND SOUTHERN CONNECTICUT WILL CONTINUE ICE BREAKUP AND MOVEMENT INTO THIS WEEKEND. ISOLATED ICE JAMS ARE POSSIBLE...WHICH IF THEY OCCUR...COULD RESULT IN LOCALIZED FLOODING. SINCE ICE JAM FLOODING IS UNPREDICTABLE AND SUDDEN...INTERESTS ALONG ICE COVERED RIVERS SHOULD MONITOR NWS FORECASTS FOR THE LATEST INFORMATION. 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.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 PM SATURDAY TO 6 AM EDT SUNDAY FOR ANZ338. SMALL CRAFT ADVISORY FROM 6 PM SATURDAY TO 6 AM EDT SUNDAY FOR ANZ330-335-340-345. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ350-353-355.
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&& $$ SYNOPSIS...MPS/DW NEAR TERM...MPS SHORT TERM...MPS LONG TERM...DW AVIATION...GOODMAN MARINE...MPS/DW HYDROLOGY...MPS/DW

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