Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 010231 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 931 PM EST SAT FEB 28 2015 .SYNOPSIS... HIGH PRESSURE OVER THE AREA SLIDES OFFSHORE INTO SUNDAY. A COLD FRONT APPROACHES FROM THE WEST LATE SUNDAY...THEN CROSSES THE AREA SUNDAY NIGHT. HIGH PRESSURE BUILDS IN FROM THE WEST ON MONDAY AND SLIDES OFFSHORE ON TUESDAY. LOW PRESSURE WILL TRACK WELL NORTH OF THE AREA TUESDAY NIGHT AND WEDNESDAY...WITH A WARM FRONT LIFTING INTO THE AREA TUESDAY NIGHT...FOLLOWED BY A COLD FRONT WEDNESDAY AND ANOTHER SURFACE TROUGH LATE WEDNESDAY NIGHT. HIGH PRESSURE THEN BUILDS IN FOR THE REMAINDER OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 850-500 HPA SHORTWAVE RIDGING CROSSES THE AREA TONIGHT...KEEPING THINGS DRY. IT WILL ALSO KEEP THE AREA RELATIVELY CLOUD FREE UNTIL THE RIDGE AXIS PASSES OVERNIGHT. HIGH CLOUDS APPROACHING FROM THE WEST LATE THIS EVENING PER IR. FORECAST IS GENERALLY ON TRACK. INCREASED LOWS A FEW DEGREES TONIGHT WITH MID AND HIGH CLOUDS EXPECTED TO MOVE IN DURING THE LATTER PART OF THE NIGHT. WINDS ARE LIGHT AND VRB TO CALM WITH CLEAR SKIES PROMOTING EXCELLENT RADIATIONAL COOLING CONDS. TEMPS HAVE FALLEN DUE TO THESE CLEAR SKIES AND LIGHT WINDS. LOWS ARE FORECAST TO BE AROUND 15-20 DEGREES BELOW NORMAL - MAINLY IN THE SINGLE DIGITS...EXCEPT 10-15 NYC AND WESTERN LONG ISLAND. THERE COULD BE A FEW AREAS IN FAR N INTERIOR ZONES THAT DIP JUST BELOW ZERO. WINDS WILL BE LIGHT...SO WIND CHILLS WILL BE AT IF NOT SLIGHTLY BELOW THE AIR TEMPERATURE. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/... MODELS ARE ALL IN GOOD AGREEMENT ON THE GENERAL PATTERN SUNDAY- MONDAY...BUT DIFFER IN DETAILS...PARTICULARLY AT THE SURFACE. GIVEN WESTERLY FLOW AND WARM ADVECTION PATTERN ON SUNDAY...EXPECT PRECIPITATION TO DEVELOP AS FAST IF NOT FASTER THAN THE FASTEST MODEL...WHICH IS THE GFS. HAVE INCREASED POPS TO CATEGORICAL BY LATE AFTERNOON AS A RESULT. REGARDLESS OF MODEL OF CHOICE...ONLY SEE SNOW AS THE P-TYPE DURING THE DAY ON SUNDAY. HAVE SIDED WITH HIGHER RESOLUTION...ESPECIALLY IN THE VERTICAL...ECMWF/NAM/CMC-REG AND TO A LESSER EXTENT THE SREF WITH THE IDEA OF A COASTAL FRONT DEVELOPING TO THE S OF LONG ISLAND SUNDAY NIGHT...WITH A WEAK LOW OF PRESSURE RIDING ALONG IT AND PASSING TO THE S OF LONG ISLAND. THIS IS A FEATURE THAT HAS BEEN OBSERVED IN MULTIPLE OTHER STORMS WITH A SIMILAR PATTERN THIS WINTER...AND HAVE NO REASON TO BELIEVE THAT THIS TIME WILL BE ANY DIFFERENT. THE IMPACT OF THIS COASTAL FRONT WITH THE WAVE OF LOW PRESSURE GOING ALONG IT...WILL BE TO HELP KEEP THE LOW LEVEL COLD AIR IN PLACE THROUGH MOST OF SUNDAY NIGHT OVER THE CWA. AS A RESULT DO NOT HAVE ANY AREA MIXING WITH OR CHANGING TO RAIN...HOWEVER STILL EXPECT NYC/LONG ISLAND/MOST OF NE NJ/S WESTCHESTER AND FAIRFIELD TO MIX WITH/CHANGE TO ZR LATE SUNDAY EVENING. WITH THE FASTER ONSET...ALSO HAVE A FASTER END TIME...WITH PRECIPITATION COMING TO AN END FROM W TO E AFTER MIDNIGHT SUNDAY NIGHT. BASED ON THIS...EXPECT 2-5 INCHES OF SNOW WITH UP TO A TENTH OF AN INCH OF ICE ACROSS NYC/LONG ISLAND/NE NJ/COASTAL WESTCHESTER AND FAIRFIELD. EXPECT 3-6 INCHES OF SNOW ELSEWHERE...EXCEPT FOR POSSIBLY 4-7/MAYBE 8 INCHES ACROSS NEW HAVEN/MIDDLESEX/NEW LONDON COUNTIES. THEREFORE HAVE ISSUED A WINTER STORM WATCH FROM NEW HAVEN COUNTY ON E IN S CT...AND A WINTER WEATHER ADVISORY ELSEWHERE IN THE CWA. STILL SOME UNCERTAINTY ON QPF - WITH NAM/SREF WETTEST AND GFS GENERALLY THE DRIEST...WITH THE CMC AND ECMWF IN BETWEEN...AND TIMING. ALSO STILL SOME UNCERTAINTY ON TIMING OF ANY MIX/CHANGE OVER TO ZR...AND IF COASTAL FRONT WILL INDEED STAY S OF LONG ISLAND AS CURRENTLY FORECAST. TEMPERATURES SUNDAY/SUNDAY NIGHT A BLEND OF MAV/MET/ECS GUIDANCE AND NAM 2-METER TEMPERATURES...WITH AN ADJUSTMENT FOR WET-BULBING BASED ON A MAV/MET BLENDED DEW POINT WHILE PRECIPITATING. TEMPERATURES GENERALLY REACH MID 20S-LOWER 30S BEFORE THE ONSET OF PRECIPITATION...THEN COOL TO THE LOWER 20S-AROUND 30 DURING THE EVENT SUNDAY EVENING. COULD SEE A SLIGHT RISE IN TEMPERATURES LATE SUNDAY NIGHT AFTER THE PRECIPITATION COMES TO AN END. MONDAY SHOULD BE DRY WITH DOWN SLOPING BOUNDARY LAYER FLOW...DESPITE PASSAGE OF 500 HPA TROUGH AXIS. HIGHS MONDAY SHOULD BE AROUND 5-10 DEGREES BELOW NORMAL...WITH ALL BUT POSSIBLY HIGHER ELEVATIONS BREAKING THE FREEZING MARK. GUSTY NW WINDS MONDAY WITH GUSTS BY AFTERNOON UP TO 25-35 MPH WITH SOME ISOLATED GUSTS TO 40 MPH POSSIBLE. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... MODELS ARE IN DECENT AGREEMENT AT H5 THROUGH THE WEEK...ALTHOUGH SLIGHT DIFFERENCES IN HEIGHTS BEGIN TO TAKE SHAPE DURING THE LATTER HALF FROM A DIGGING TROF IN THE MIDDLE OF THE COUNTRY. RIDGING AT THE SFC AND ALOFT TRACKS TOWARDS THE E COAST MON NIGHT WITH THE UPPER RIDGE AXIS SLIDING E TUE AFTN. PCPN WILL OVERSPREAD THE AREA BY TUE EVENING AS SNOW...BUT WITH INCREASING S-SW WINDS AND STRONG WAA TEMPS WILL WARM TUE NIGHT WITH SNOW CHANGING OVER TO RAIN FROM S TO N. WARM FRONT LIFTING TOWARDS THE AREA TUE NIGHT...BUT THERE IS SOME UNCERTAINTY IF THE LLJ WILL BE STRONG ENOUGH TO PUSH IT THROUGH AT THE SFC. CLIMATOLOGY SAYS NO WITH THE LOW SO FAR TO THE NW...SO TEMPS IN THE MID TO UPPER 40S MAY BE TOO HIGH. HOWEVER...DO THINK TEMPS SHOULD BE ABOVE FREEZING BUT HOW MUCH WILL DEPEND ON THE AMOUNT OF MELTING OF THE SNOWPACK. THIS...IN ADDITION TO RAINFALL COULD LEAD TO MINOR FLOODING ISSUES. COLD FRONT MOVES ACROSS WED FOLLOWED BY ANOTHER BOUNDARY LATE WED NIGHT. THE NORTHERN EDGE OF THE PCPN SHIELD OF A SOUTHERN STREAM SYSTEM RIDING ALONG THIS SECONDARY BOUNDARY COULD KEEP PCPN LINGERING INTO THU...ALTHOUGH THE TREND HAS BEEN S OVER THE LAST 12 HOURS. HAVE KEPT CHC POPS FOR NOW. COLD WEATHER ALSO RETURNS IN THE WAKE OF THIS SECOND BOUNDARY. STRONG CANADIAN HIGH PRES THEN BUILDS TOWARDS THE AREA INTO THE WEEKEND WITH DRY WEATHER BUT THE WELL BELOW NORMAL TEMPS CONTINUING. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... HIGH PRESSURE TONIGHT WILL WEAKEN SUNDAY MORNING AS A WARM FRONT APPROACHES. EXPECT VFR CONDITIONS THROUGH EARLY SUNDAY MORNING...THEN VSBY RAPIDLY LOWERS TO IFR DURING MID TO LATE MORNING AS LIGHT SNOW DEVELOPS. THE SNOW PICKS UP IN INTENSITY AFTER 20Z FROM WEST TO EAST...WITH LIFR POSSIBLE. WINDS HAVE BECOME LIGHT/VARIABLE OR CALM LATE THIS EVENING AS THE HIGH PASSES OVERHEAD...THEN LIGHT SOUTHERLY WINDS ARE FORECAST BY LATE SUNDAY MORNING OR EARLY SUNDAY AFTERNOON. .OUTLOOK FOR 00Z MONDAY THROUGH WED... .SUNDAY NIGHT...MVFR/IFR CONDITIONS EXPECTED. SNOW...CHANGING TO A WINTRY MIX AT KJFK/KEWR DURING THE EVENING...THEN AT THE REST OF THE NYC METRO TERMINALS AFTER MIDNIGHT. MOST LIKELY TOTAL RUNWAY ACCUMULATIONS... KGON...5-7 INCHES. KSWF/KHPN/KBDR...4-6 INCHES. KEWR/KTEB/KLGA...2-4 INCHES. KJFK/KISP...2-3 INCHES. .MON-MON NIGHT...BECOMING VFR EARLY. NW WINDS 15-20 KT WITH GUSTS 25-35 KT FROM LATE MORNING UNTIL AROUND SUNSET. .TUE...CHANCE OF SNOW WITH MVFR OR IFR CONDITIONS IN THE AFTERNOON AT THE NYC METRO AND LOWER HUDSON VALLEY TERMINALS. VFR FARTHER EAST. .TUE NIGHT...IFR CONDITIONS LIKELY. SNOW...CHANGING TO A WINTRY MIX AFTER MIDNIGHT...AND THEN RAIN LATE AT ALL TERMINALS EXCEPT KSWF. LLWS POSSIBLE AFTER MIDNIGHT. .WED...IFR CONDITIONS POSSIBLE IN RAIN...WITH FREEZING RAIN CHANGING TO RAIN AT KSWF...AND PLAIN RAIN ELSEWHERE. LLWS POSSIBLE IN THE MORNING. .WED NIGHT...MVFR CONDITIONS LIKELY...IFR CONDITIONS POSSIBLE. RAIN...MIXING WITH OR CHANGING TO SNOW AFTER MIDNIGHT. .THU...CHANCE OF SNOW AND RAIN WITH MVFR CONDITIONS POSSIBLE...ENDING BY NIGHTFALL. && .MARINE... A RELAXED PRESSURE GRADIENT WILL KEEP CONDITIONS BELOW SMALL CRAFT LEVELS THROUGH SUNDAY NIGHT WITH WINDS 10 KT OR LESS ON ALL WATERS THROUGH THEN. WINDS INCREASE RAPIDLY OUT OF THE NW MONDAY AS LOW PRESSURE DEEPENS TO THE NORTHEAST. ALL WATERS WILL SEE AT LEAST GUSTS TO SCA LEVELS WITH A SMALL CHANCE TO CHANCE OF GALE GUSTS AS WELL. WILL HIGHLIGHT THIS POTENTIAL IN THE HWO. SUB-ADVSY CONDS RETURN LATE MON NIGHT AND CONTINUE THROUGH TUE. SCA CONDS THEN RETURN TUE NIGHT DUE TO AN INCREASING SLY FLOW AHEAD OF A WARM FRONT AND THEN BEHIND A COLD FROPA ON WED. GUSTS DIMINISH WED NIGHT...BUT SEAS ON THE OCEAN WATERS WILL LINGER INTO THU. && .HYDROLOGY... THERE IS THE POTENTIAL FOR AROUND 4-6 TENTHS OF AN INCH OF LIQUID EQUIVALENT TO FALL SUNDAY AND SUNDAY NIGHT. WITH ALL OF THIS EXPECTED TO BE EITHER FROZEN OR FREEZING PRECIPITATION...NO IMMEDIATE HYDROLOGIC IMPACT IS EXPECTED. BETWEEN 1/2 TO 1 INCH OF LIQUID EQUIVALENT PCPN IS POSSIBLE LATE TUE THROUGH WED. MOST OF THIS WILL FALL AS RAIN...THEREFORE THE COMBINATION OF THIS AND A MELTING SNOWPACK COULD CAUSE MINOR FLOODING ISSUES. ICE WILL CONTINUE TO DEVELOP ON LOCAL AREA RIVERS AND STREAMS AS TEMPERATURES REMAIN WELL BELOW AVERAGE. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...WINTER WEATHER ADVISORY FROM 10 AM SUNDAY TO 7 AM EST MONDAY FOR CTZ005-009. WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING FOR CTZ006>008-010>012. NY...WINTER WEATHER ADVISORY FROM 10 AM SUNDAY TO 7 AM EST MONDAY FOR NYZ067>075-078>081-176>179. NJ...WINTER WEATHER ADVISORY FROM 10 AM SUNDAY TO 7 AM EST MONDAY FOR NJZ002-004-006-103>108. MARINE...NONE. && $$ SYNOPSIS...MALOIT NEAR TERM...MALOIT/PW SHORT TERM...MALOIT LONG TERM...24 AVIATION...PW MARINE...24/MALOIT/PW HYDROLOGY...24/MALOIT

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