Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 251659 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1159 AM EST TUE NOV 25 2014 .SYNOPSIS... WEAK HIGH PRESSURE BUILDS IN BEHIND A DEPARTING COLD FRONT TODAY. LOW PRESSURE THEN DEEPENS AND TRACKS NORTHEAST TONIGHT. IT PASSES SOUTHEAST OF LONG ISLAND WEDNESDAY NIGHT...THEN HEADS INTO THE CANADIAN MARITIMES THURSDAY. HIGH PRESSURE THEN BUILDS IN BEHIND THE DEPARTING LOW FOR THE END OF THE WEEK. A WARM FRONT WILL LIFT THROUGH ON SATURDAY....FOLLOWED BY A COLD FRONT SUNDAY NIGHT. ANOTHER AREA OF HIGH PRESSURE BUILDS FROM THE NORTH FOR EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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CANOPY OF MID AND UPPER LEVEL CLOUDS STREAMING UP THE EASTERN SEABOARD HAVE BEEN THICKER THAN ADVERTISED AND WILL GO WITH MOSTLY CLOUDY SKIES. TEMPS HAVE PEAKED AND ACTUALLY HAVE DROPPED OFF A FEW DEGREES IN SPOTS WITH THE COLD ADVECTION BEHIND THE COLD FRONTAL PASSAGE EARLIER. FULL LATITUDE UPPER TROF WILL PIVOT INTO THE MS VALLEY WITH COASTAL CYCLOGENESIS TO ENSUE ALONG THE SE COAST BY THIS EVE. THIS LOW WILL IMPACT THE AREA ON WED WITH A POTENTIAL HEAVY WET SNOWFALL FOR PARTS OF THE TRI-STATE AREA.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
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SOME WINTER STORM WATCHES HAVE BEEN UPGRADED TO WARNINGS ACROSS THE INTERIOR. BASED ON 12Z GUIDANCE...CONFIDENCE OF A WARNING LEVEL SNOW IN THOSE AREAS HAS INCREASED. REFER TO NYCWSWOKX OR VISIT WEATHER.GOV/NYC FOR THE UPDATE. IT LOOKS TO BE A REAL CLOSE CALL FOR THOSE LOCATIONS NEAR THE COAST WHERE THERMO PROFILES SHOW AN ELEVATED WARM LAYER IN THE MID LEVELS WITH A NEARLY ISOTHERMAL SOUNDING BELOW THAT. UNDOUBTEDLY ONE OF THE MORE CHALLENGING FORECASTS AND CLEARLY AGAINST CLIMO. MODEL CONSENSUS SHOWS A COASTAL LOW DEVELOPING OFF THE SOUTHEAST COAST TONIGHT. THE CENTER OF THIS STORM TRACKS NE THROUGH WEDNESDAY AND PASSES OVER OR VERY CLOSE TO THE 40N/70W BENCHMARK WEDNESDAY EVENING. BY LATE WEDNESDAY NIGHT...IT WILL BE CLOSE TO NOVA SCOTIA. PRECIPITATION MOVES IN FROM THE SOUTH LATE AT NIGHT...WITH A CHANCE THAT LONG ISLAND...THE CITY AND IMMEDIATE SURROUNDING SUBURBS SEE SOME OF THIS PRECIPITATION BY DAYBREAK WEDS. PRECIPITATION THEN STARTS BY NOON FOR THE ENTIRE TRI STATE AREA AND PROBABLY ENDS BY DAYBREAK THURS FOR MOST OF THE AREA. PRECIPITATION TYPE...AND CONSEQUENTLY THE SNOWFALL AMOUNT FORECAST...WILL BE CHALLENGING. WITH A LACK OF A POLAR HIGH TO THE NORTH...THE AMOUNT OF DYNAMIC COOLING BECOMES IMPORTANT...PARTICULARLY ACROSS THE COASTAL ZONES. A LACK OF DOWNSTREAM BLOCKING WILL HAVE THIS STORM TRACK RELATIVELY QUICKLY. BASED ON WHERE MID LEVEL FRONTOGENESIS/TOTAL DEFORMATION AXES ALIGN WITH THE TIGHTEST 700MB TEMPERATURE GRADIENT...THE POTENTIAL FOR BANDED PRECIPITATION AND DYNAMIC COOLING OF THE THERMAL PROFILE APPEARS TO BE ENHANCED OVER THE CITY...SOUTHWESTERN CT AND BORDERING AREAS...COINCIDENT WITH OMEGA VALUES OF 20-30 MICROBARS PER SECOND DURING THE LATER MORNING/AFTERNOON HOURS. THE OMEGA IS NOT MAXIMIZED IN THE DENDRITIC SNOW GROWTH ZONES...BUT DOES STRETCH INTO IT. COMPLICATING THE PRECIPITATION TYPE FORECAST...MAINLY FOR EASTERN CT AND EASTERN LI IS THE POTENTIAL OF AN ELEVATED WARM LAYER NEAR 700MB DURING THE AFTERNOON HOURS. ANYTHING THAT OTHERWISE WOULD HAVE FALLEN AS SNOW COULD INSTEAD FALL AS SLEET...BUT NOT ENOUGH CONFIDENCE YET TO INCLUDE SLEET IN THE FCST. MARGINAL SURFACE/BOUNDARY LAYER TEMPERATURES WILL ALSO BE A FACTOR FOR COASTAL AREAS. ALL THINGS TAKEN INTO CONSIDERATION...WILL NOT CONVERT ANY OF THE WINTER STORM WATCHES TO WARNINGS JUST YET. WARNING CRITERIA MIGHT NOT BE FIRST MET UNTIL SOMETIME LATE IN THE 3RD PERIOD...AND FOR SOME AREAS...NOT UNTIL THE 4TH PERIOD. THERE IS SOME CONCERN THAT QPF COULD LEAN TOWARDS THE DRIER 00Z GFS...WHICH WOULD TRANSLATE TO MARGINAL WARNING CRITERIA ACROSS THE LOWER HUDSON VALLEY AND ADJACENT AREAS. 00Z ECMWF HAS TRENDED A QUARTER INCH DRIER ON AVERAGE FROM THE PREVIOUS RUN. WILL HOWEVER EXPAND THE WINTER STORM WATCH A LITTLE SOUTHEAST TO COVER SW COASTAL CT...THE CITY...AND BORDERING AREAS. THIS IS TO ACCOUNT FOR THE AFOREMENTIONED POTENTIAL OF MESOSCALE BANDING AND BETTER DYNAMIC COOLING.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/... THE H5 FLOW ACROSS THE CONUS WILL BE UNDERGOING A CHANGE DURING THE LONG TERM PERIOD ALL CONTROLLED BY THE VORTEX SPINNING JUST N OF HUDSON BAY. UPPER TROUGH OVER THE ERN US WILL SHIFT OFFSHORE THU NIGHT/FRI AS THE RIDGE OVER THE WESTERN STATES FLATTENS AS IT MOVES EWD. ZONAL FLOW DEVELOPS OVER MUCH OF THE COUNTRY THIS WEEKEND WITH AMPLIFICATION BEGINNING EARLY NEXT WEEK AS A DEEP TROUGH/CUTOFF LOW APPROACHES THE WEST COAST. NOT TOO MUCH TO BE CONCERNED WITH IN TERMS OF SENSIBLE WEATHER LOCALLY...ALTHOUGH WINTER-LIKE TEMPERATURES WILL RETURN THU AND FRI WITH HIGHS/LOWS BETWEEN 10 AND 15 DEGREES BELOW NORMAL THANKS TO THE AFOREMENTIONED UPPER TROUGH. COULD SEE SOME SOUND EFFECT SNOW/RAIN SHOWERS OR FLURRIES ON A WLY FLOW...MAINLY ON LI...THU AS ENERGY ASSOCIATED WITH THE UPPER TROUGH AXIS SWINGS THROUGH. GFS IS THE MOST ROBUST WITH QPF WHILE OTHER MODELS ARE DRY SO HAVE ONLY GONE SCHC POPS FOR NOW. DRY WEATHER THEN PREVAILS AS SFC HIGH BUILDS ACROSS THE AREA THU NIGHT/FRI. A WARM FRONT LIFTS THROUGH ON SAT...BUT HAVE KEPT FORECAST DRY WITH LIMITED MOISTURE. WE`LL REMAIN WARM SECTORED INTO SUN WITH WAA ENSUING. WARMER BUT STILL BELOW NORMAL TEMPS AS A COLD FRONT APPROACHES. THE FRONT WILL TRACK ACROSS THE AREA SUN NIGHT...BUT AGAIN LOOKS TOO DRY FOR ANY PRECIPITATION. THE FORECAST EARLY NEXT WEEK BECOMES FUZZY DUE TO THE TIMING OF THE NEXT AREA OF HIGH PRES BUILDING FROM THE N. THE DETERMINISTIC GFS/EC MODELS ARE SLOWER TO BUILD THE HIGH IN AND KEEP THE FRONTAL BOUNDARY NEARBY WITH A WAVE OF LOW PRES DEVELOPING ALONG IT AND TRACKING OVER THE AREA ON MON. THE ENSEMBLES BUILD THE HIGH IN QUICKER...SUPPRESSING THE FRONT TO THE S WITH DRY WEATHER CONTINUING. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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&& .MARINE... SCA WILL CONTINUE ON THE OCEAN AS SEAS WILL BE SLOW TO SUBSIDE BELOW 5 FT. HAVE EXTENDED THIS SAC TO GO INTO THIS EVENING...AND MAY NEED TO EVENTUALLY BE EXTENDED IN TIME EAST OF FIRE ISLAND INLET. A COASTAL LOW BRINGS THE LIKELIHOOD OF GALE CONDITIONS TO THE COASTAL OCEAN WATERS WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. THE GALE WATCH ON THE OCEAN HAS BEEN CONVERTED TO A WARNING. SOME/ALL OF THE NON-OCEAN WATERS MAY NEED A SMALL CRAFT ADVISORY FOR ROUGHLY THE SAME PERIOD. WILL ALLOW DAY SHIFT TO FINE TUNE THE FORECAST BEFORE ISSUING ANY FLAGS CONCERNING THIS. SAC SEAS WILL LIKELY CONTINUE ON THE OCEAN WATERS THURS THROUGH THU NIGHT. THE PRES GRADIENT WILL INCREASE THU NIGHT AS WELL SO MARGINAL NW SAC WIND GUSTS/SEAS CONTINUING INTO FRI REMAIN POSSIBLE ON THE OCEAN WATERS. TRANQUIL CONDITIONS THEN EXPECTED ON ALL WATERS AS HIGH PRES BUILDS OVER AND EAST OF THE WATERS THROUGH SAT. MARGINAL SAC CONDS ARE THEN AGAIN POSSIBLE SAT NIGHT WITH THE GRADIENT INCREASING BETWEEN THE DEPARTING HIGH AND LOW PRESSURE PASSING TO THE NORTH. && .HYDROLOGY... NO SIGNIFICANT PRECIPITATION THROUGH MOST OF TONIGHT. FOR WEDS AND WEDS NIGHT...EXPECTING A LIQUID EQUIVALENT PRECIPITATION AMOUNTS AVERAGING AROUND 0.75 TO 1.5. THE HIGHEST QPF AMOUNTS AREA CURRENTLY EXPECTED OVER EASTERN CT/LONG ISLAND AND THE LOWEST OVER FAR WESTERN PORTIONS OF THE TRI-STATE. OVER THE INTERIOR MOST OF THIS WILL FALL IN THE FORM OF SNOW...SO LITTLE IF ANY IMMEDIATE HYDROLOGIC IMPACT IS EXPECTED THERE. FARTHER TO THE S/E...BASICALLY ALONG AND E OF I-95...THERE WILL BE A A MIX OF RAIN AND SNOW. THIS COULD CAUSE MINOR FLOODING OF URBAN/POOR DRAINAGE AREAS. THEREAFTER...VERY LIGHT QPF AMOUNTS ARE POSSIBLE THROUGH THE WEEKEND. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 7 AM EST THURSDAY FOR CTZ005-006. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING FOR CTZ007>010. NY...WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 7 AM EST THURSDAY FOR NYZ067>070. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING FOR NYZ071>075-176>178. NJ...WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 7 AM EST THURSDAY FOR NJZ002-103. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING FOR NJZ004-006-104>108. MARINE...SMALL CRAFT ADVISORY FROM 10 AM WEDNESDAY TO 1 AM EST THURSDAY FOR ANZ330-335-338-340-345. SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR ANZ350-353- 355. GALE WARNING FROM 11 AM WEDNESDAY TO MIDNIGHT EST WEDNESDAY NIGHT FOR ANZ350-353-355.
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&& $$ NEAR TERM...DW AVIATION...GOODMAN

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