Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 152027 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 427 PM EDT TUE APR 15 2014 .SYNOPSIS...
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A STRONG COLD FRONT WILL MOVE THROUGH THE TRI-STATE AREA BY EARLY THIS EVENING...FOLLOWED BY HIGH PRESSURE BUILDING IN FROM THE OHIO VALLEY ON WEDNESDAY. THE HIGH THEN LIFTS UP INTO THE CANADIAN MARITIMES WEDNESDAY NIGHT INTO THURSDAY AND UP INTO THE NORTH ATLANTIC ON FRIDAY. A LOW PRESSURE SYSTEM DEVELOPS ALONG A STALLED FRONT TO THE SOUTH FRIDAY NIGHT AND PASSES EAST OF THE REGION ON SATURDAY. HIGH PRESSURE RETURNS SUNDAY INTO MONDAY BEFORE SHIFTING OFFSHORE WITH THE APPROACH OF A COLD FRONT ON TUESDAY.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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A STRONG COLD FRONT IS CURRENTLY MOVING ACROSS THE LOWER HUDSON VALLEY WITH OBS BOTH AT SWF AND MGJ SUPPORTING A WIND SHIFT TO THE WEST. TEMPERATURES WILL LIKELY FALL SOME 10 TO 20 DEGREES WITHIN A COUPLE OF HOURS OF THE FRONTAL PASSAGE. THE FRONT WILL PASS THROUGH THE NYC METRO AROUND 6 PM AND EASTERN LI/SE CT BY 8 PM. PRIOR TO THE FRONTAL PASSAGE...THERE WILL BE MULTIPLE BANDS OF SHOWERS WITH MODERATE TO HEAVY RAINFALL, ACROSS LONG ISLAND AND CT THE CONVECTION IS MAINLY ASSOCIATED WITH STRONG THERMAL FORCING AIDED BY A 65 TO 70 KT LOW-LEVEL JET. TO THE WEST...THE BAND ACROSS NW NJ AND THE LOWER HUDSON VALLEY IS ASSOCIATED WITH STRONG FRONTAL FORCING. WHILE THERE IS NO SURFACE BASED INSTABILITY...THERE IS ELEVATED INSTABILITY WITH THE POTENTIAL FOR ISOLATED WIND GUSTS UP TO 50 MPH IN THE STRONGEST CONVECTION. POST-FRONTAL PCPN IS THEN FILLING IN ACROSS EASTERN PA IN CONJUNCTION WITH AN AMPLIFYING UPPER TROUGH AND THE RRQ OF THE UPPER JET. BY THE TIME THE EVENT IS OVER LATE TONIGHT INTO THE EARLY MORNING HOURS WED...MUCH OF THE REGION WILL HAVE SEEN 1 TO 2 INCHES OF RAINFALL. STRONG COLD ADVECTION WILL ALSO ALLOW FOR THE TRANSITION OVER TO SOME WET SNOW THIS EVENING. THE BEST CHANCE FOR THIS TO OCCUR WILL BE IN THE NW SUBURBS WHERE A COATING TO AN INCH OF SNOW WILL BE POSSIBLE. THE TIMING OF THE CHANGEOVER WILL BE CRITICAL AS TO THE AMOUNTS. SHOULD THIS TRANSITION OCCUR EARLIER THAN FORECAST... THERE COULD BE AS MUCH AS 2 TO 3 INCHES OF SNOWFALL. THE CHANGEOVER WILL FIRST HAPPEN ACROSS ORANGE COUNTY IN NEW YORK AND PASSAIC COUNTY NJ AROUND 8 PM. A COATING ACROSS EASTERN AREAS WHILE UNLIKELY...IS STILL A POSSIBILITY. GUSTY SOUTH WIND EARLY WILL TURN AROUND TO THE NW THIS EVENING WITH GUSTS OF 40 YO 45 MPH. THERE COULD EVEN BE A FEW HIGHER GUSTS RIGHT BEHIND THE COLD FRONT DUE TO STRONG PRESSURE RISES. OVERNIGHT LOWS WILL BE IN THE MID 20S TO AROUND FREEZING. THUS... THE FREEZE WARNING HAS BEEN EXPANDED TO ALSO INCLUDE NYC...LONG ISLAND...AND COASTAL CT. THIS IS IN ADDITION TO MOST OF NE NJ AND ROCKLAND AND WESTCHESTER COUNTIES IN NEW YORK. GUIDANCE HAS BEEN TRENDING COLDER. BASED ON THE ANOMALOUSLY COLD AIR MASS...USED MODEL 2M TEMPS FOR LOWS...WHICH WAS SEVERAL DEGREES BELOW MOS GUIDANCE. LOWS WILL BE CLOSE TO RECORDS.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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HIGH PRESSURE BUILDS EAST FROM THE OHIO VALLEY ON WED WITH AN ANOMALOUSLY COLD AIR MASS. HIGHS WILL BE IN THE MID AND UPPER 40S...WHICH IS SOME 10 TO 15 DEGREES BELOW NORMAL. GUSTY NW WINDS WILL LINGER INTO THE AFT...MAKING IT FEEL MORE LIKE THE MID AND UPPER 30S. WED NIGHT WILL FEATURE ANOTHER POSSIBLE RECORD COLD NIGHT WITH MOST LOCATIONS OUTSIDE OF THE NYC METRO DROPPING BELOW FREEZING. ANOTHER FREEZE IS POSSIBLE.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
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AT THE BEGINNING OF THE LONG TERM ON THURSDAY AND FRIDAY...THE REGION WILL BE ON THE WEST SIDE OF UPPER LEVEL RIDGING ACROSS THE WESTERN ATLANTIC WITH A TROUGH ACROSS THE CENTRAL STATES. AT THE SURFACE...HIGH PRESSURE OVER NEW ENGLAND THURSDAY SHIFTS INTO THE CANADIAN MARITIMES BY FRIDAY. THIS PATTERN SETS UP AN EAST TO NORTHEASTERLY FLOW IN THE LOW LEVELS. THIS ONSHORE FLOW SERVES TO KEEP TEMPERATURES ON THE COOL SIDE WITH READINGS IN THE UPPER 40S AND LOWER 50S ON THURSDAY AND LOWER AND MIDDLE 50S ON FRIDAY. INCREASING LOW LEVEL MOISTURE LATE THURSDAY NIGHT INTO FRIDAY MORNING COULD PROMOTE DRIZZLE OR LIGHT RAIN...MAINLY ACROSS SOUTHERN ZONES. HAVE INCLUDED SLIGHT CHANCE POPS DURING THIS TIME. THE TROUGH ACROSS THE CENTRAL STATES APPROACHES FRIDAY NIGHT INTO SATURDAY WITH A WAVE OF LOW PRESSURE DEVELOPING ALONG A STALLED FRONT OFFSHORE. MUCH OF THE GUIDANCE KEEPS THE LOW FAR ENOUGH OFFSHORE TO PREVENT A WIDESPREAD PRECIP EVENT. THE MODELS DIFFER ON THE AMPLITUDE...TIMING...AND PLACEMENT OF THE VORT ENERGY WITHIN THE UPPER TROUGH HOWEVER. AT THE VERY LEAST...SATURDAY WILL BE MOSTLY CLOUDY AND HAVE CONTINUED A CHANCE FOR SHOWERS WITH THE UPPER TROUGH PASSAGE. DUE TO CLOUDS AND PRECIPITATION...TEMPERATURES CONTINUE BELOW NORMAL IN THE 50S. A GENERAL ZONAL FLOW SETS UP ON SUNDAY AND CONTINUES INTO MONDAY. SURFACE HIGH PRESSURE BUILDS BACK IN DURING THIS TIME WITH DRY CONDITIONS. SLIGHTLY BELOW NORMAL TEMPERATURES WILL CONTINUE ON SUNDAY AND THEN WARMING TO NEAR NORMAL ON MONDAY. A SHORTWAVE AND ASSOCIATED COLD FRONT MAY APPROACH ON TUESDAY BRINGING A CHANCE FOR SHOWERS. HIGH UNCERTAINTY EXISTS AT THIS TIME SO HAVE ONLY INCLUDED CHANCE POPS. TEMPERATURES SHOULD BE NEAR NORMAL IN THE 60S.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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COLD FRONT MOVING THROUGH EXTREME WESTERN TERMINALS CURRENTLY...WILL CONTINUES MOVING THROUGH THE REST OF THE TERMINALS THIS EVENING. WIDE VARIATIONS IN CONDITIONS. BREAKS IN SHOWERS WILL SEE SOME VSBY AND/OR CIG IMPROVEMENT...TO VFR IN SOME CASES. OTHERWISE...IFR CONDITIONS EXPECTED...ESPECIALLY WITH THE HEAVIER BAND OF PRECIPITATION MOVING INTO NORTHEAST NJ. LIFR STILL POSSIBLE IN THESE HEAVIER SHOWERS. AS OF 20Z...KJFK VIS DOWN 1/2SM. DO NOT THINK THIS WILL BE PREVAILING...BUT PUT IN A TEMPO GROUP THROUGH 00Z AS FLOW RIGHT OFF THE OCEAN IS LIKELY LEADING TO THE LOWER VSBY HERE. AS THE FLOW TURNS MORE SOUTHWESTERLY...VSBY SHOULD IMPROVE. GUSTS 30-35 KTS IN THE CITY TERMINALS EARLY THIS EVENING. OME ISOLATED GUSTS CLOSE TO 40KT POSSIBLE. WINDS WILL S -SW- NW DURING THIS TIME AS THE FRONT MOVES THROUGH 22Z-03Z. WINDS WILL TAPER OFF SLIGHTLY WITH THE FRONTAL PASSAGE...THEN INCREASE AGAIN AS THE WINDS SHIFT TO THE NW. GUSTS UP TO AROUND 35 KTS LIKELY TONIGHT WITH AN ISOLATED GUST TO 40 KTS POSSIBLE. LLWS ISSUES PERSISTING THROUGH LATE AFTN...WITH GENERALLY 50-60 KTS BETWEEN 1-2KFT. SLIGHTLY HIGHER LLWS OF UP TO 65 KT FOR EASTERN SECTIONS SUCH AS KISP AND KGON AS LOW LEVEL JET STRENGTHENS OVER THESE AREAS THIS MORNING. AS THE JET PUSHES EAST WITH THE APPROACH OF THE COLD FRONT...LLWS WILL DIMINISH THIS EVENING. 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) KEWR FCSTER COMMENTS: LIFR CONDITIONS PSBL THIS AFTN WITH HEAVIER RAIN...VFR PSBL IN BREAKS IN SHOWERS. LLWS SHOULD END AFTER FROPA...AFTER 22Z. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD. KJFK FCSTER COMMENTS: LIFR CONDITIONS PSBL THIS AFTN WITH HEAVIER RAIN...VFR PSBL IN BREAKS IN SHOWERS. LLWS SHOULD END AFTER FROPA...AFTER 22Z. KLGA FCSTER COMMENTS: LIFR CONDITIONS PSBL THIS AFTN WITH HEAVIER RAIN...VFR PSBL IN BREAKS IN SHOWERS. LLWS SHOULD END AFTER FROPA...AFTER 22Z. KTEB FCSTER COMMENTS: LIFR CONDITIONS PSBL THIS AFTN WITH HEAVIER RAIN...VFR PSBL IN BREAKS IN SHOWERS. LLWS SHOULD END AFTER FROPA...AFTER 22Z. KHPN FCSTER COMMENTS: LIFR CONDITIONS PSBL THIS AFTN WITH HEAVIER RAIN...VFR PSBL IN BREAKS IN SHOWERS. LLWS SHOULD END AFTER FROPA...AFTER 22Z. KISP FCSTER COMMENTS: LIFR CONDITIONS PSBL THIS AFTN WITH HEAVIER RAIN...VFR PSBL IN BREAKS IN SHOWERS. LLWS SHOULD END AFTER FROPA...AFTER 23Z. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY... .WED...VFR. N WIND G20-25KT PSBL. .WED NIGHT...VFR. .THURS...VFR. E WIND G 20-25KT PSBL. .THURS NIGHT-FRI NIGHT...VFR. .SAT...PSBL MVFR CONDITIONS WITH LOW CHANCE OF -SHRA. .SUN...VFR
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&& .MARINE...
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GALE WARNING IN EFFECT FOR ALL WATERS...PRIMARILY FOR THE NW FLOW TONIGHT BEHIND A STRONG COLD FRONTAL PASSAGE. GUSTS UP TO 40 KT POSSIBLE. HOWEVER...IN THE HOURS PRECEDING THE COLD FRONTAL PASSAGE EARLY THIS EVENING...THERE WILL ALSO BE MARGINAL GALE FORCE GUSTS IN THE SLY FLOW. MARGINAL SCA CONDITIONS ARE THEN POSSIBLE ON WED...MAINLY WITH LINGERING 5 FT SEAS. SCA WINDS AND SEAS LIKELY ON THURSDAY AS EASTERLY FLOW INCREASES. WINDS WILL TREND BELOW SCA LEVELS FRIDAY BUT SEAS ON OFFSHORE WATERS SHOULD STAY ABOVE SCA THROUGH FRIDAY NIGHT. WINDS AND SEAS WILL RELAX ON SATURDAY AS REGION WEAKER FLOW SETS UP OVER THE WATERS. SEAS AND WINDS COULD RETURN TO SCA LEVELS ON SUNDAY WITH INCREASED NORTHWESTERLY FLOW.
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&& .HYDROLOGY...
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RAINFALL OF 1 1/2 TO 2 INCHES...MAINLY ALL LIQUID...EXPECTED FOR THE EVENT TOTAL THROUGH LATE TONIGHT. THERE IS THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS IN ANY STRONG CONVECTION. LOW TO MODERATE POTENTIAL EXISTS FOR MINOR FLOODING OF URBAN/POOR DRAINAGE AREAS. ALSO LOW POTENTIAL FOR FLASHY SMALL STREAMS ACROSS NORTHEASTERN NEW JERSEY INTO THE LOWER HUDSON VALLEY TO REACH MINOR FLOOD LEVELS WITH 1 HOUR FLASH FLOOD GUIDANCE AROUND 1 INCH. NOTE...MINOR FLOODING CONTINUES ALONG THE CONNECTICUT RIVER. ADDITIONAL HEAVY RAINFALL WILL LIKELY CAUSE WATER LEVELS TO CONTINUE TO RISE THROUGH THE WEEK...WITH POTENTIAL FOR MODERATE FLOOD LEVELS TO BE REACHED. MONITOR THE LATEST FLOOD WARNINGS FROM NWS TAUNTON MA. NO SIGNIFICANT PRECIPITATION IS EXPECTED FROM THURSDAY INTO EARLY NEXT WEEK.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...FREEZE WARNING FROM 2 AM TO 10 AM EDT WEDNESDAY FOR CTZ009>012. NY...FREEZE WARNING FROM 2 AM TO 10 AM EDT WEDNESDAY FOR NYZ069>075- 078>081-176>179. NJ...FREEZE WARNING FROM 2 AM TO 10 AM EDT WEDNESDAY FOR NJZ004-006- 103>108. MARINE...GALE WARNING UNTIL 6 AM EDT WEDNESDAY FOR ANZ330-335-338-340- 345-350-353-355.
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&& $$ SYNOPSIS...DS/DW NEAR TERM...DW SHORT TERM...DW LONG TERM...DS AVIATION...JP MARINE...DS/DW HYDROLOGY...DS/DW

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