Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 240001 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 701 PM EST FRI JAN 23 2015 .SYNOPSIS... HIGH PRESSURE MOVES OFF THE MID ATLANTIC COAST TONIGHT. A RAPIDLY DEEPENING LOW MOVES ALONG THE MID ATLANTIC COAST SATURDAY MORNING...PASSING SOUTH AND EAST OF SOUTHERN NEW ENGLAND SATURDAY NIGHT. A COLD FRONT PUSHES TO THE SOUTH SUNDAY. HIGH PRESSURE BUILDS DOWN FROM SOUTHERN CANADA THROUGH WEDNESDAY...AS A SERIES OF LOWS PASS TO THE SOUTH AND EAST OF LONG ISLAND. THE HIGH RETREATS TO THE NORTHEAST WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. A COLD FRONT PUSHES TO THE SOUTH ON FRIDAY. && .NEAR TERM /UNTIL MIDNIGHT TONIGHT/... FORECAST ON TRACK. MINOR UPDATES TO HOURLY T/TD/WINDS. MID AND HIGH CLOUDS MOVING IN THIS EVENING FROM THE SW. LOWS WILL LIKELY BE MET AT MOST LOCATIONS THIS EVENING. && .SHORT TERM /MIDNIGHT TONIGHT THROUGH SATURDAY NIGHT/... THE MAIN FOCUS DURING THIS PERIOD WILL BE ON A QUICK MOVING BUT RAPIDLY INTENSIFYING LOW PRESSURE SYSTEM AFFECTING THE REGION LATE TONIGHT INTO SATURDAY EVENING. MODELS IN GOOD AGREEMENT WITH SOUTHERN STREAM SHORTWAVE ENERGY OVER TEXAS THIS AFTERNOON SLIDING TO THE EAST COAST THROUGH SAT AFTERNOON...WHILE INTERACTING WITH A NORTHERN STREAM SHORTWAVE. THE TREND HAS BEEN MORE PROGRESSIVE WITH THE INTENSIFYING SHORTWAVE...WITH FULL PHASING AND CLOSED UPPER LOW DEVELOPMENT NE OF THE REGION. SIMILARLY MODELS IN GOOD AGREEMENT WITH LOW PRESSURE ALONG THE GULF COAST THIS AFTERNOON QUICKLY TRACKING NE TONIGHT TOWARDS THE MID-ATLANTIC...AND NOW INSIDE OF THE 40/70 LAT/LON BENCHMARK BY SATURDAY EVENING. ALL OF THE ABOVE POINTS TO AN INTENSE BUT QUICK MOVING SYSTEM...WITH A FASTER...MORE WESTWARD TRACK...AND SLIGHTLY WETTER THAN 24 HOURS AGO. WITH NO HIGH TO THE NORTH OF THE REGION...A MARGINALLY COLD AIRMASS WILL BE IN PLACE. THERMAL PROFILES AND EXPECTED EVAPORATIONAL COOLING POINTS TOWARDS CONDITIONS COLD ENOUGH FOR PRECIP TO START AS SNOW FOR ALL AREAS...MAINLY AFTER MIDNIGHT. SNOW SHOULD BECOME MODERATE TO HEAVY FROM SW TO NE BTWN 4-7AM WITH STRONG WAA/MOISTURE ADVECTION ALOFT AND STRONG LIFT FROM A COUPLE JET STRUCTURE WITH STRONG FRONTOGENETIC FORCING. 1+ INCH SNOWFALL RATES POSSIBLE SATURDAY MORNING. AS INTENSIFYING LOW PRESSURE APPROACHES...AN E/SE LLJ JET BEGINS TO ADVECT +1-4C 850-900MB AIR FROM S TO N FOR ALL BUT FAR NW PORTIONS OF THE REGION BETWEEN 10Z AND 14Z. THIS SHOULD TRANSITION PRECIP TO SLEET/FREEZING RAIN/RAIN FROM S TO N...BTWN 6AM AND 8AM FOR NY/NJ METRO AND COASTAL AREAS...AND MID MORNING TO MIDDAY WORKING INTO MUCH OF INTERIOR. INDICATIONS ARE THAT FOR THE NY/NJ METRO AND COASTAL PLAIN...THAT ENOUGH WARM AIR GETS IN ALOFT FOR A CHANGE TO MAINLY LIQUID PRECIP (RAIN/FREEZING RAIN) FROM MID MORNING INTO EARLY AFTERNOON. A BIT FARTHER N AND W...THIS WILL LIKELY BE A MIX OF SLEET...SNOW...AND FREEZING RAIN. WHILE INTERIOR PORTIONS OF NE NJ...LOWER HUDSON VALLEY...AND SW CT WILL LIKELY BE MAINLY SNOW THROUGH THE EVENT. THERMAL PROFILES ARE ONE ISSUE...BUT THE OTHER ISSUE IS BANDING PLACEMENT AND QPF. BASED ON WESTWARD ENSEMBLE OPER MODEL TREND...HAVE INCREASED QPF BY ABOUT 1/4 INCH ACROSS THE BOARD FROM PREVIOUS FORECAST. THE SWEET SPOT FOR DEFORMATION BANDING POTENTIAL AND COLDER THERMAL PROFILE SAT AFTERNOON APPEARS TO BE ACROSS INTERIOR SW CT AND NORTHEASTERN HUDSON VALLEY ZONES...WITH THE HIGHEST SIGNIFICANT SNOWFALL THREAT. IN TERMS OF SNOW AMOUNTS...THE TOUGH PART OF THIS FORECAST IS THAT WE COULD BE LOOKING AT 1+ INCH SNOWFALL RATES AS WE ARE ARE TRANSITIONING SATURDAY MORNING...SO A 1-2 HR TIMING DIFFERENCE IN CHANGEOVER COULD BE A 1 TO 3 INCH DIFFERENCE IN SNOWFALL. FOR THE NYC/NJ METRO AND COAST MOST OF THE SNOW ACCUM SHOULD BE LATE TONIGHT INTO EARLY SAT MORNING. A GENERAL 2 TO 5 INCH RANGE STILL LOOKS REASONABLE THERE...WITH HIGHER AMOUNTS ACROSS NE NJ...LOWER HUDSON VALLEY...AND SW CT. AGAIN WITH BEST BANDING POTENTIAL AND WESTWARD MODEL DRIFT ACROSS INTERIOR PORTIONS OF THE SW CT ZONES AND PUTNAM COUNTY...5 TO 8 INCHES EXPECTED THERE...AND A WARNING HAS BEEN ISSUED. IN TERM OF FREEZING RAIN THREAT...ISALLOBARIC RESPONSE FROM THE RAPIDLY INTENSIFYING LOW SHOULD KEEP WINDS MORE NORTHERLY THROUGH THE PEAK OF THE STORM. THIS TYPICALLY PROMOTES COLD AIR DRAINAGE DOWN THE HUDSON AND CT RIVER VALLEYS...WHICH SHOULD HOLD SURFACE TEMPS NEAR FREEZING OR JUST BELOW FOR NY/NJ METRO...NORTH SHORE OF LI...AND COASTAL SW/SC CT THROUGH THE MID TO LATE MORNING(AFTER CHANGEOVER). SO POTENTIAL OF UP TO TENTH OF AN INCH OF ICE ACCRETION AWAY FROM SOUTH COASTAL LI/NYC IN THE MORNING. HEAVIEST ICE ACCRETION LIKELY ACROSS SOUTHERN CT...WITH WARMER AIR WORKING IN ALOFT BUT SURFACE TEMPS REMAINING NEAR OR SLIGHTLY BELOW FREEZING. POTENTIAL FOR UP TO 1/4 INCH OF ICE HERE. IN TERMS OF WINDS...NORTHERLY WINDS INCREASE SAT AFTERNOON...PEAKING IN THE AFTERNOON AND EVENING. GENERALLY 10 TO 20 MPH WITH GUSTS IN THE 30S. A PEAK GUST TO 40 MPH IS POSSIBLE ACROSS EASTERN LI/SE CT. ACROSS LI AND COASTAL CT...HEAVY RAIN SAT MORN/EARLY AFT AND EARLIER SNOW MAY RESULT IN SOME MINOR URBAN FLOODING ISSUES. ESPECIALLY ALONG THE COAST DURING TIMES OF HIGH TIDE LATE MORNING INTO EARLY AFTERNOON. THERMAL PROFILES APPEARS TO COOL ENOUGH BY MID TO LATE AFTERNOON FOR A CHANGE BACK TO SLEET THEN SNOW DOWN TO COAST...BUT QUESTION WILL BE HOW MUCH PRECIP IS LEFT. UNCERTAINTY EXISTS ON HOW FAR SOUTH BANDING POTENTIAL EXISTS...AND WILL NOT LIKELY BECOME CLEAR UNTIL SAT AFTERNOON. WITH PROGRESSIVE TREND OF THE UPPER TROUGH EXPECTING ADDITIONAL ACCUM FOR THE METRO/COAST TO BE LIGHT (COATING TO 3 INCHES) MID-LATE SAT AFT INTO EARLY SAT EVE FOR NY/NJ METRO AND COAST AS COLDER AIR WORKS IN. AS MENTIONED BEFORE...THE SWEET SPOT FOR DEFORMATION BANDING SAT AFTERNOON STILL APPEARS TO BE ACROSS INTERIOR SOUTHERN CONNECTICUT ZONES. ANY SNOW COMES TO AND END LATE SAT AFTERNOON/EARLY SAT EVENING...WITH BREEZY AND NEAR SEASONABLE TEMPS SAT NIGHT. && .LONG TERM /SUNDAY THROUGH FRIDAY/... ZONAL FLOW ALOFT ON SUNDAY...GIVES WAY TO WEAK RIDGING SUNDAY EVENING. SO IT SHOULD BE DRY SUNDAY AND SUNDAY EVENING. THE MODELS ARE MOVING TOWARDS A CONSENSUS OF ANY STORM SYSTEM EARLY NEXT WEEK STAYING FAR ENOUGH TO THE S AND E TO PROBABLY HAVE LITTLE OR NO IMPACT ON THE REGION. THE REASON FOR THIS IS THAT THERE NO LONGER IS ANY - OR AT MOST VERY WEAK - PHASING PREDICTED BETWEEN THE NORTHERN AND SOUTHERN STREAMS...SO THE SOUTHERN STREAM DRIVEN SURFACE LOW WILL END UP TAKING A FARTHER S PATH...AND THE NORTHERN STREAM ENERGY STAYS TO OUR N...LEAVING THE REGION HAVING NO TO LITTLE FORCING SUNDAY NIGHT-MONDAY NIGHT. TO GUARD AGAINST THE MODELS SWINGING THINGS BACK IN THE OTHER DIRECTION ONLY REDUCED POPS TO SLIGHT CHANCE N AND LOW END CHANCE SOUTH FROM LATE SUNDAY NIGHT INTO MONDAY NIGHT. HOWEVER...WOULD NOT BE SURPRISED IF ULTIMATELY THE FORECAST ENDED UP BEING DRY FOR MOST IF NOT ALL THE AREA IN THIS TIME FRAME. FOR NOW IT APPEARS THE BEST CHANCE FOR ANY SNOWFALL SUNDAY NIGHT-MONDAY NIGHT WOULD BE ALONG THE IMMEDIATE S SHORE OF LONG ISLAND. WHAT IS FAIRLY CERTAIN IS THAT A SOLID SHOT OF CONTINENTAL POLAR AIR PUSHES IN FOR THE EARLY TO MIDDLE PARTS OF NEXT WEEK...AS A MEAN ROUGH SETTLES OVER THE EASTERN U.S. THIS WILL RESULT IN TEMPERATURES BEING MUCH BELOW NORMAL SUNDAY NIGHT-WEDNESDAY NIGHT. WIND CHILLS ARE CURRENTLY FORECAST TO BE MAINLY FROM 5 TO 15 SUNDAY NIGHT...THEN FROM AROUND 0 TO -10 MONDAY NIGHT AND TUESDAY NIGHT...AND ONLY IN THE TEENS DURING THE DAY MONDAY AND TUESDAY...THEN IN THE 20S ON WEDNESDAY. RIDGING BUILDS IN WEDNESDAY NIGHT...THEN SLIDES OFFSHORE ON THURSDAY. A TROUGH OF LOW PRESSURE THEN WILL SLOWLY APPROACH AND CROSS THE AREA THURSDAY NIGHT AND FRIDAY. IT SHOULD BE DRY WEDNESDAY NIGHT-THURSDAY...THEN A SLIGHT CHANCE OF SNOW SHOWERS WITH THE UPPER TROUGH THURSDAY NIGHT AND FRIDAY. A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 975-900 HPA WAS USED FOR HIGHS ON SUNDAY - WITH VALUES FORECAST TO BE NEAR TO SLIGHTLY BELOW NORMAL. FOR LOWS SUNDAY NIGHT A BLEND OF MAV/MET GUIDANCE WITH NAM 2-METER TEMPERATURES WAS USED...WITH READINGS FORECAST TO BE A FEW DEGREES BELOW NORMAL. FROM MONDAY-FRIDAY A BLEND OF MEX/MEN/EKD/ECE/ECM/WPC GUIDANCE WAS USED...WITH NAM 2-METER TEMPERATURES BLENDED IN AS WELL ON MONDAY...AND ECMWF 2-METER TEMPERATURES BLENDED IN ON FRIDAY. TEMPERATURES MONDAY-WEDNESDAY WILL RUN AROUND 10 TO 15 DEGREES BELOW NORMAL...WITH THE COLDEST DAY BEING TUESDAY...WITH HIGHS FROM THE UPPER 10S TO MID 20S...AND THE COLDEST NIGHT TUESDAY NIGHT...WITH LOWS MAINLY IN THE SINGLE DIGITS...TEMPERATURES MODERATE TO SLIGHTLY BELOW NORMAL BY THE END OF THE UPCOMING WORK WEEK. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... ...HIGH IMPACT AVIATION WINTER EVENT TONIGHT INTO SATURDAY... LOW PRESSURE APPROACHES FROM THE SOUTHWEST TONIGHT AND REACHES THE MID ATLANTIC COAST LATE TONIGHT. THE LOW CONTINUES TO DEEPEN AND TRACK TO THE NORTHEAST SATURDAY...MOVING AWAY FROM THE AREA SATURDAY EVENING. SNOW SPREADS INTO THE AREA LATE THIS EVENING...AND BECOMES STEADIER AND HEAVIER LATE TONIGHT. A WINTRY MIX MOVES IN ALONG THE COAST TOWARD MORNING AND FARTHER INLAND EARLY SATURDAY. A CHANGE TO ALL RAIN IS EXPECTED AT THE COASTAL TERMINALS SATURDAY MORNING INTO THE EARLY AFTERNOON. A CHANGE BACK TO ALL SNOW IS LIKELY AS THE PRECIPITATION ENDS LATE IN THE AFTERNOON INTO THE EVENING. VFR THIS EVENING WITH CONDITIONS QUICKLY LOWERING TO IFR AS THE SNOW BEGINS. IFR MUCH OF SATURDAY BEFORE IMPROVING BY SATURDAY EVENING. THERE IS UNCERTAINTY WITH THE TIMING OF MIXING AND CHANGEOVER AND WILL BE DEPENDENT ON THE TRACK OF THE LOW. 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: VFR THIS EVENING. AMENDMENTS HIGHLY LIKELY WITH ONSET AND CHANGEOVER OF PRECIPITATION. AROUND 3 INCHES OF SNOW EXPECTED WITH A TRACE OF FREEZING RAIN AND SLEET. KLGA FCSTER COMMENTS: VFR THIS EVENING. AMENDMENTS HIGHLY LIKELY WITH ONSET AND CHANGEOVER OF PRECIPITATION. THREE TO 4 INCHES OF SNOW EXPECTED WITH A TRACE OF FREEZING RAIN AND SLEET. KEWR FCSTER COMMENTS: VFR THIS EVENING. AMENDMENTS HIGHLY LIKELY WITH ONSET AND CHANGEOVER OF PRECIPITATION. AROUND 4 INCHES OF SNOW EXPECTED WITH A TRACE OF FREEZING RAIN AND SLEET. KTEB FCSTER COMMENTS: VFR THIS EVENING. AMENDMENTS HIGHLY LIKELY WITH ONSET AND CHANGEOVER OF PRECIPITATION. AROUND 4 INCHES OF SNOW EXPECTED WITH A TRACE OF FREEZING RAIN AND SLEET. KHPN FCSTER COMMENTS: VFR THIS EVENING. AMENDMENTS HIGHLY LIKELY WITH ONSET AND CHANGEOVER OF PRECIPITATION. AROUND 4 INCHES OF SNOW EXPECTED WITH A TRACE OF FREEZING RAIN AND SLEET. KISP FCSTER COMMENTS: VFR THIS EVENING. AMENDMENTS HIGHLY LIKELY WITH ONSET AND CHANGEOVER OF PRECIPITATION. AROUND 2 INCHES OF SNOW EXPECTED WITH A TRACE OF FREEZING RAIN AND SLEET. .OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY... .SATURDAY NIGHT...LIGHT SNOW ENDING EARLY IN THE EVENING WITH CONDITIONS IMPROVING TO VFR. NW WIND 10-20 KT WITH GUSTS 20-30 KT. .SUNDAY...VFR. WEST WIND 10-15 KT WITH GUSTS 15-20 KT. .SUNDAY NIGHT-MONDAY NIGHT...MVFR/IFR CONDS IN SNOW POSSIBLE. .TUESDAY-WEDNESDAY...VFR. && .MARINE... INITIALLY...CONDITIONS WILL BE BELOW SCA WITH HIGH PRESSURE IN CONTROL. HOWEVER...THE HIGH MOVES OFFSHORE TONIGHT INTO SATURDAY...GIVING WAY TO APPROACHING LOW PRESSURE. NE WINDS WILL RAPIDLY INCREASE TO SCA TOWARDS MORNING AS LOW PRESSURE APPROACHES WILL ALSO BRING HIGHER SEAS. MARGINAL GALE GUSTS POSSIBLE ON THE OCEAN AT THIS TIME. WINDS TURN MORE NORTHERLY AND THEN NW DURING THE DAY SAT AS LOW TRACKS SE OF THE REGION AND DEEPENS...WITH SCA CONDS CONTINUING ELSEWHERE. GALES EXPECTED ACROSS THE EASTERN OCEAN WATERS SAT AFT INTO SAT NIGHT. OCEAN SEAS BUILDING TO 7 TO 10 FT IN RESPONSE. SMALL CRAFT CONDITIONS ARE LIKELY ON ALL WATERS ON SUNDAY...WITH A BRIEF LULL ON SUNDAY NIGHT..EXCEPT FOR POSSIBLY SEAS ON THE COASTAL OCEAN WATERS EAST OF MORICHES INLET. SMALL CRAFT ADVISORY CONDITIONS ARE PROBABLE ON ALL WATERS...WITH GALE CONDITIONS POSSIBLE ON THE COASTAL OCEAN WATERS MONDAY AND MONDAY NIGHT...DEPENDING ON THE EXACT TRACK AND STRENGTH OF A COASTAL LOW PASSING TO THE S AND E OF LONG ISLAND. SEAS ON THE COASTAL OCEAN WATERS EAST OF FIRE ISLAND INLET WILL REMAIN ABOVE SMALL CRAFT LEVELS ON TUESDAY...AND POSSIBLY INTO WEDNESDAY. OTHERWISE...SUB SMALL CRAFT CONDITIONS ARE EXPECTED ON THE WATERS AROUND LONG ISLAND DURING THE MIDDLE OF NEXT WEEK. && .HYDROLOGY... LOW PRESSURE IMPACTS THE REGION TONIGHT INTO SATURDAY NIGHT WITH QPF UP TO 1 TO 1 1/4 INCH ACROSS LI/SE CT...AROUND 1 INCH ACROSS NE NJ AND SW CT...TO 1/2 INCH FOR AREAS FAR NW OF NYC. THIS WILL FALL AS A MIX OF SNOW...SLEET...FREEZING RAIN...AND RAIN. NO SIGNIFICANT PRECIPITATION IS EXPECTED FROM SUNDAY-FRIDAY...WITH SUNDAY AND TUESDAY-THURSDAY FORECAST TO BE DRY. ICE ON THE WALLKILL AND YANTIC RIVERS IS CAUSING MINOR FLUCTUATIONS IN RIVER LEVELS AT THIS TIME. && .TIDES/COASTAL FLOODING... WATER LEVELS WILL APPROACH MINOR COASTAL FLOOD THRESHOLDS ACROSS THE WESTERN LI/NYC SOUTH SHORE BAYS DURING THE MID TO LATE MORNING HIGH TIDE CYCLE ON SAT...LOCALLY TOUCHING MINOR THRESHOLDS. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EST SATURDAY FOR CTZ007>011. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM EST SATURDAY FOR CTZ005-006. NY...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EST SATURDAY FOR NYZ067-069>075-078-080-176>179. WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 PM EST SATURDAY FOR NYZ068. NJ...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM EST SATURDAY FOR NJZ002-004-006-103>108. MARINE...SMALL CRAFT ADVISORY FROM 5 AM SATURDAY TO 6 AM EST SUNDAY FOR ANZ330-335-338-340-345-353-355. GALE WARNING FROM 5 AM TO 11 PM EST SATURDAY FOR ANZ350. && $$

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