Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 290612 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 112 AM EST THU JAN 29 2015 .SYNOPSIS... HIGH PRESSURE BUILDS OVER THE AREA TONIGHT...THEN SLIDES OFFSHORE THURSDAY. A STORM SYSTEM APPROACHES FROM THE WEST THURSDAY EVENING...THEN CROSSES THE AREA LATE THURSDAY NIGHT AND FRIDAY MORNING...IMMEDIATELY FOLLOWED BY AN ARCTIC COLD FRONT. HIGH PRESSURE WILL BE SLOW TO BUILD EAST FROM THE OHIO VALLEY FRIDAY NIGHT INTO SATURDAY...WHILE LOW PRESSURE CONTINUES TO WRAP UP OVER THE CANADIAN MARITIMES. A WEAK COLD FRONT THEN MOVES THROUGH ON SUNDAY. LOW PRESSURE MOVES OUT OF THE MISSISSIPPI VALLEY ON SUNDAY...AND THEN RACES EAST TO OFF THE MID ATLANTIC COAST ON MONDAY. HIGH PRESSURE FOLLOWS FOR MONDAY NIGHT INTO WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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FORECAST IS ON TRACK. JUST SOME MINOR ADJUSTMENTS TO REFLECT LATEST OBSERVATIONS. OTHERWISE...DEEP LAYERED RIDGING BUILDS IN. ASSOCIATED SUBSIDENCE SHOULD KEEP THINGS DRY...AND ALLOW FOR A CLEAR SKY. WINDS BECOME LIGHT AND VARIABLE OVERNIGHT...THIS COMBINED WITH THE CLEAR SKY AND SNOW COVER WILL PROMOTE VERY STRONG RADIATIONAL COOLING. TOOK THE MINIMUM OF AVAILABLE GUIDANCE AND UNDERCUT BY 1-2 DEGREES FOR LOWS. LOWS SHOULD BE AROUND 10-15 DEGREES BELOW NORMAL - AROUND 0 TO AROUND 10 ABOVE. WITH WIND CHILLS GENERALLY WITHIN A FEW DEGREES OF...IF NOT THE AIR TEMPERATURE DUE TO THE LIGHT WINDS.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... THE DEEP LAYERED RIDGE SLIDES TO THE EAST THURSDAY...WITH ASSOCIATED SUBSIDENCE KEEPING THINGS DRY. WILL SEE INCREASING MID AND HIGH CLOUDS BY LATE IN THE DAY...ESPECIALLY OVER WESTERN ZONES AHEAD OF AN APPROACHING 700-500 HPA SHORTWAVE. FOR HIGHS THURSDAY USED A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 975-950 HPA PER BUFKIT SOUNDINGS. THEN SUBTRACTED A DEGREE OR TWO TO REFLECT THE IMPACT OF SNOW COVER. HIGHS SHOULD BE AROUND 5 TO 10 DEGREES BELOW NORMAL. A 700-500 HPA SHORTWAVE LIFTS NE THROUGH THE AREA THURSDAY NIGHT. THIS SHOULD BRING SOME LIGHT SNOW THURSDAY NIGHT TO THE ENTIRE CWA. THIS IS IMMEDIATELY FOLLOWED BY THE 700-500 HPA SHORTWAVE TROUGH ALONG WITH AN ARCTIC COLD FRONT AT THE SURFACE. SHOULD SEE SOME MORE LIGHT SNOW AHEAD OF THIS...MAINLY FRIDAY MORNING. SNOW TOTALS SHOULD RANGE FROM AROUND AN INCH OR LESS ACROSS NYC/LONG ISLAND AND PARTS OF COASTAL SE CT AND NE NJ...AND AROUND 1-2 INCHES ELSEWHERE - WITH 2 INCH AMOUNTS MOST LIKELY ACROSS THE FAR N TIER OF THE CWA. IT WILL TURN SHARPLY COLDER IN THE AFTERNOON OVER WESTERN AREAS BEHIND THE ARCTIC FRONT...WITH TEMPERATURES FALLING INTO THE MID- UPPER TEENS OVER FAR W ZONES...AND INTO THE LOW-MID 20S OVER THE REMAINDER OF THE WESTERN 1/2 OF THE CWA. THIS COULD CAUSE A FLASH FREEZE OF ANY MELTED SNOW ON UNTREATED SURFACES. FOR LOWS THURSDAY NIGHT...TOOK A BLEND OF MAV/MET/ECS GUIDANCE AND NAM 2-METER TEMPERATURES - WITH VALUES AROUND NORMAL IN NYC AND ITS IMMEDIATE NEIGHBORS TO AROUND 5 ABOVE NORMAL ELSEWHERE. HIGHS FRIDAY WERE DERIVED FROM A BLEND OF NAM 2-METER TEMPERATURES AND A BLEND OF MET AND ECS GUIDANCE. MAV NUMBERS SEEMED TOO WARM GIVEN EXPECTED PASSAGE OF ARCTIC FRONT. HIGHS SHOULD BE UP TO 5 DEGREES BELOW NORMAL. AS NOTED ABOVE...SHOULD HAVE A NON-DIURNAL TEMPERATURE TREND ON FRIDAY WITH HIGHS MAINLY IN THE MORNING...ESPECIALLY ACROSS WESTERN ZONES. BLENDED NAM 2-METER TEMPERATURES INTO HOURLY TEMPERATURES TO REFLECT THIS NON- DIURNAL TREND. IT WILL BECOME WINDY BY LATE AFTERNOON...DROPPING WIND CHILLS INTO THE SINGLE DIGITS OVER WESTERN ZONES AND TEENS OVER EASTERN ZONES. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... MEAN UPPER TROUGH WILL REMAIN ACROSS THE UPPER PLAINS SE TO THE EASTERN SEABOARD WITH SEVERAL SHORT WAVES MOVING THROUGH DURING THE PERIOD. THIS WILL MORE OR LESS KEEP THE FORECAST AREA BELOW NORMAL FOR TEMPS WITH SOME MODIFICATION AHEAD OF SEVERAL WAVES OF LOW PRESSURE. WHILE THE LATEST 12Z GUIDANCE SUPPORTS A MORE PROGRESSIVE...LESS AMPLIFIED FLOW...THERE IS ALWAYS SOME UNCERTAINTY WITH THE MAGNITUDE OF THE UPSTREAM ENERGY COMING ONSHORE WESTERN CANADA. THE BIGGEST CHANGE THIS MODEL CYCLE IS FOR A SUPPRESSED STORM TRACK SUN NIGHT INTO MON...WITH BOTH THE OPERATIONAL GFS AND ECMWF TAKING WEAK LOW PRESSURE TO THE SOUTH OF THE REGION. IN FACT...THE ECMWF IS DRY...WHILE THE GFS ONLY PRODUCES VERY LIGHT QPF ACROSS THE AREA. THESE SCENARIOS ARE COLD ENOUGH FOR ALL SNOW. AT THE OTHER END OF THE ENVELOPE IS THE GGEM...WHICH IS ABOUT 24 HOURS SLOWER WITH A MUCH MORE AMPLIFIED SYSTEM MOVING THROUGH THE NE MON INTO TUE. THIS SYSTEM WOULD RESULT IN DIFFERENT P-TYPES. THE 12Z GEFS STILL HAS A LARGE SPREAD IN LOW TRACKS...AS DID PREVIOUS GLOBAL MODEL ENSEMBLE RUNS. SO TO BE CONSERVATIVE AND NOT DISCOUNT THE SYSTEM...HAVE DROPPED OFF POPS SLIGHTLY AND WILL WAIT TO SEE IF THE 12Z CYCLE SHOWS MORE RUN TO RUN CONTINUITY BEFORE LOWERING POPS EVEN MORE. WHAT DOES SEEM MORE CERTAIN THOUGH...IS VERY COLD AND WINDY CONDITIONS FRI NIGHT INTO SAT WITH A POSSIBLE WIND ADVISORY EVENT AS GUSTS APPROACH 45 MPH. WIND CHILL VALUES WILL DROP BELOW ZERO AND A WIND CHILL ADVISORY IS NOT OUT OF THE QUESTION...ESPECIALLY NORTH AND WEST OF NYC. HIGH PRESSURE FOLLOWS SAT NIGHT INTO SUN WITH A WEAK COLD FRONTAL PASSAGE ON SUN. THE AFOREMENTIONED STORM SYSTEM MAY BRING SOME LIGHT SNOW TO THE REGION SUN NIGHT INTO MON BEFORE HIGH PRESSURE RETURNS FOR TUE AND WED. TEMPS DURING THE PERIOD WILL BE BELOW NORMAL AND MAY NOT EVEN REACH THE FREEZING MARK. THE COLDEST DAYS LOOK TO BE SAT AND TUE...WHERE HIGHS WILL STRUGGLE TO GET OUT OF THE LOWER 20S COAST AND THE UPPER TEENS INLAND. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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HIGH PRES OVER THE OH VALLEY MOVES OVERHEAD EARLY THIS MORNING AND DEPARTS TODAY. A CLIPPER LOW APPROACHES TONIGHT. VFR THROUGH THIS MORNING. INCREASING POTENTIAL FOR MVFR CIGS TO DEVELOP AFT 21Z ACROSS NYC/NJ AND WESTERN TERMINALS. IFR CONDITIONS POSSIBLE IN LIGHT SNOW AS EARLY AS 00Z...INCREASING PROB THROUGH 06Z. N WINDS BECOME LIGHT AND VARIABLE EARLY THIS MORNING. SE FLOW DEVELOPS LATE THIS AFTERNOON INTO EVENING. A PERIOD OF GUSTS TO 20 KT POSSIBLE CITY/COAST. INCREASING POTENTIAL FOR MVFR/IFR CONDITIONS IN LIGHT SNOW AFTER 00-03Z. .OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY... .LATE TONIGHT-FRIDAY MORNING...IFR CONDITIONS LIKELY IN SNOW. UP TO 1 INCH OF RUNWAY ACCUMULATION IS POSSIBLE FOR KNYC AND COASTAL TERMINALS...WITH 1-2 INCHES AT KHPN/KSWF. .FRIDAY AFTERNOON-FRIDAY EVENING...SCATTERED SNOW SHOWERS. FLASH FREEZE OF UNTREATED SURFACE POSSIBLE LATE AFTERNOON/EVENING. NW WINDS 20KT WITH 25-35 KT GUSTS. .FRIDAY NIGHT...VFR WITH DIMINISHING WINDS LATE. .SATURDAY...VFR. NW WINDS GUSTING 20-25 KT. .SUNDAY-MONDAY...CONDITIONS DETERIORATE LATE SUNDAY TO MVFR OR LOWER...INITIALLY IN SNOW. LOW CONFIDENCE ON PRECIPITATION TYPE AS PRECIPITATION COULD BECOME A WINTRY MIX SUNDAY NIGHT AND MONDAY DUE TO UNCERTAINTY WITH TRACK OF LOW. LOW CONFIDENCE WIND FORECAST AS WELL.
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&& .MARINE...
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WINDS AND SEAS HAVE FALLEN BELOW SMALL CRAFT LEVELS ON THE OCEAN WATERS. EXPECT SUB-SCA CONDITIONS FROM LATE TONIGHT INTO THURSDAY EVENING. WINDS INCREASE LATER THURSDAY EVENING IN RESPONSE TO A TIGHTENING PRESSURE GRADIENT...WITH SCA LEVEL GUSTS BY LATE EVENING OVER THE COASTAL OCEAN WATERS EAST OF FIRE ISLAND INLET...AND AFTER MIDNIGHT ON THE COASTAL OCEAN WATERS WEST OF FIRE ISLAND INLET. WIND GUSTS INCREASE TO SCA LEVELS ON THE REMAINDER OF THE WATERS ON FRIDAY MORNING...THEN GALE FORCE GUSTS DEVELOP ON ALL WATERS BY LATE AFTERNOON. GALE CONDITIONS ARE LIKELY FRI NIGHT INTO SAT BEHIND DEEPENING LOW PRESSURE OVER THE CANADIAN MARITIMES. SUB SCA CONDITIONS SHOULD DEVELOP ON ALL WATERS BY LATE SATURDAY NIGHT...AND CONTINUE ON SUNDAY...WITH HIGH PRESSURE BUILDING OVER THE REGION.
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&& .HYDROLOGY... NO SIGNIFICANT PRECIPITATION IS EXPECTED THROUGH FRIDAY...THOUGH SOME LIGHT SNOW IS EXPECTED THURSDAY NIGHT INTO FRIDAY...WITH NO HYDROLOGIC IMPACT EXPECTED. THERE IS THE POTENTIAL FOR LIGHT QPF SUN NIGHT INTO MON AS LOW PRESSURE PASSES TO THE SOUTH OF THE REGION. MODEL ENSEMBLES HAVE SHOWN LARGE SPREADS WITH THE LOW TRACK. THERE IS THE POTENTIAL FOR A MORE SIGNIFICANT SYSTEM...BUT TRENDS IN THE 12Z RUN HAVE BEEN FARTHER SOUTH AND WEAKER WITH THE LOW. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...MALOIT/DW NEAR TERM...BC/MALOIT SHORT TERM...MALOIT LONG TERM...DW AVIATION...GOODMAN/NV MARINE...BC/MALOIT HYDROLOGY...MALOIT/DW

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