Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 311138 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 738 AM EDT TUE MAR 31 2015 .SYNOPSIS...
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LOW PRESSURE TRACKS INTO THE MID ATLANTIC STATES TODAY...THEN PASSES SOUTH OF LONG ISLAND TONIGHT. HIGH PRESSURE BUILDS TO THE SOUTH FROM WEDNESDAY INTO THURSDAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST THURSDAY NIGHT...THEN MOVE SLOWLY ACROSS FRIDAY AND FRIDAY NIGHT. ANOTHER COLD FRONT WILL APPROACH ON SATURDAY...THEN PUSH TO THE SOUTH INTO SUNDAY. THE FRONT SHOULD THEN STALL NEAR THE AREA INTO MONDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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MADE MINOR CHANGES THIS UPDATE TO REFLECT THE LATEST TRENDS IN OBSERVATIONS AND GUIDANCE. THE FORECAST APPEARS ON TRACK. OBS AT 11Z INDICATED THE SFC LOW WAS NEAR FAR NW OH/FAR NE IN...WITH 3-HOURLY PRESSURE FALLS IN ITS ADVANCE SUGGESTING A PATH ESE TOWARD PITTSBURGH PA BY EARLY AFTERNOON. THIS ALSO SUGGESTS THE SLIGHTLY NORTHERN LOW TRACK FORECAST BY THE NAM MAY VERIFY BETTER TODAY...AND IN FACT THIS FORECAST LEANED MORE HEAVILY ON A NAM/ECMWF BLEND AS OPPOSED TO THE FASTER AND SLIGHTLY FARTHER SOUTH GFS. AS USUAL...THE NAM IS PROBABLY TOO SLOW WITH OVERRUNNING PRECIPITATION AND HANGS ONTO EVAPORATIVE COOLING ALOFT TOO LONG...SO STARTED INCREASING POP TO CHANCE IN NYC AND NE NJ BY 15Z-16Z...GRADUALLY INCREASING THEREAFTER TO LIKELY/CAT ACROSS THE ENTIRE CWA BY LATE AFTERNOON. PER A BLEND OF 00Z NAM 2M AND MET MOS TEMPS/DEW POINTS...THINK HIGH TEMPS MOST AREAS WILL RISE NO HIGHER THAN THE UPPER 30S/LOWER 40S...WITH THE WARMEST TEMPS TODAY OCCURRING MAINLY IN SOUTHERN CT WHERE CLOUDS AND PRECIPITATION WILL TAKE LONGER TO ARRIVE. THE ABOVE GUIDANCE BLEND ALSO SUGGESTS TEMPS WILL REMAIN COLD ENOUGH FOR AN ALL SNOW EVENT IN THE HIGHEST ELEVATIONS NORTH/WEST OF NYC...AND A SNOW/RAIN MIX TRANSITIONING TO SNOW THIS EVENING ELSEWHERE NORTH/WEST. THIS SYSTEM SHOULD BE A QUICK HITTER...WITH STRONG H7-8 FRONTOGENESIS NORTH OF THE LOW TRACK PRODUCING ACCUMULATIONS OF 2-3 INCHES IN THE HIGHEST ELEVATIONS BY THE EVENING COMMUTE. HAVE ISSUED A WINTER WEATHER ADVISORY FOR WESTERN PASSAIC COUNTY WHERE CONFIDENCE IN HIGHER QPF AND AN ALL-SNOW EVENT IS GREATEST. THIS ADVISORY COULD EVENTUALLY BE EXPANDED INTO ORANGE/PUTNAM COUNTIES IF THE ABOVE- MENTIONED FORCING TRENDS FARTHER NORTH THAN EXPECTED. TEMPS ELSEWHERE WILL COOL TOWARD EVENING VIA COMBO OF EVAPORATIVE COOLING FROM FALLING PRECIPITATION...AND EXPECT MOST OF SOUTHERN CT AND LONG ISLAND TO SEE ALL SNOW OR A SNOW/RAIN MIX THIS EVENING...WITH ACCUMULATIONS THERE OF ABOUT AN INCH...MAINLY ON GRASSY AND COLDER ELEVATED SURFACES. NYC METRO MAY SEE A FEW SNOWFLAKES...BUT WITH LITTLE TO NO ACCUMULATION EXPECTED. PRECIPITATION SHOULD TAPER OFF AFTER MIDNIGHT AS THE ASSOCIATED H8 LOW AND MID LEVEL TROUGH PASS TO THE EAST...WITH CLEARING SKIES FROM WEST-EAST. LOWS SHOULD RANGE FROM THE LOWER 30S IN THE VICINITY OF NYC...TO 25-30 MOST ELSEWHERE...TO SOME LOWER 20S IN THE VALLEYS WELL NORTH/WEST OF THE CITY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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EXPECT DRY WEATHER ON WED...WITH PERHAPS SOME BKN CLOUDS DURING LATE MORNING AND EARLY AFTERNOON FROM NYC WEST A WEAKENING UPPER TROUGH MOVES ACROSS. HIGHS SHOULD BE MOSTLY IN THE MID 40S... WHICH IS 5-8 DEG BELOW AVG.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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DEEP LAYERED RIDGING BUILDS OVER THE AREA WEDNESDAY NIGHT AND THURSDAY...WITH ASSOCIATED SUBSIDENCE KEEPING THINGS DRY. FOR LOWS WEDNESDAY NIGHT USED A BLEND OF MAV/MET/ECS GUIDANCE WITH VALUES EXPECTED TO BE A FEW DEGREES BELOW NORMAL. FOR HIGHS ON THURSDAY A BLEND OF MIXING DOWN FROM 975-925 HPA PER BUFKIT SOUNDINGS...WITH NAM 2-METER TEMPERATURES AND A BLEND OF MAV AND MET GUIDANCE WAS USED. HIGHS SHOULD BE A FEW DEGREES BELOW NORMAL. THE DEEP LAYERED RIDGE AXIS SLIDES TO THE EAST THURSDAY EVENING...ALLOWING FOR LOW-MID LEVEL MOISTURE TO RAPIDLY INCREASE IN ITS WAKE. PASSAGE OF A SURFACE WARM FRONT TO THE N AND WEAK 700 AND 500 HPA SHORTWAVES SHOULD PRODUCE SUFFICIENT FORCING TO WARRANT CHANCE POPS THROUGHOUT...MAINLY AFTER MIDNIGHT. ALSO...NAM/GFS/ECMWF ALSO SHOW SHOWALTER INDICES IN THE 0 TO 2 RANGE...WARRANTING A SLIGHT CHANCE OF THUNDER TO REFLECT POTENTIAL FOR ELEVATED STORMS. REGION ALSO WILL BE IN THE RIGHT REAR QUADRANT OF 135+KT 300 HPA JET...AND HAVE A WSW 50-60KT LOW LEVEL JET PASS NEAR THE AREA AS WELL. INCREASE POPS TO LIKELY FRIDAY AHEAD OF COLD FRONT...WITH STRONGER SHORTWAVES FORECAST TO PASS THROUGH...A COUPLED UPPER JET STRUCTURE FORECAST TO EVOLVE...AND EXPECTED PERSISTENCE OF LOW LEVEL JET. HAVE ALSO CONTINUED WITH SLIGHT CHANCE OF THUNDER ON FRIDAY AS WELL. SOME DIFFERENCES BETWEEN THE MODELS ON TIMING OF COLD FRONTAL PASSAGE...WITH THE GFS FASTER THAN THE ECMWF AND CMC. HAVE LEANED TOWARDS SLOWER SOLUTION...NOTING GENERAL PROGRESSIVE BIAS TO THE GFS. AS A RESULT CARRY CHANCE POPS INTO SATURDAY MORNING. 500 HPA TROUGH AXIS SLIDES OVER THEN TO THE EAST OF THE AREA SATURDAY AND SATURDAY NIGHT. THE LOW LEVELS THOUGH SHOULD BE SUFFICIENTLY DRY TO PRECLUDE ANY PRECIPITATION. A CLIPPER TYPE LOW WITH A FAIRLY POTENT SHORTWAVE MOVING WITH THE BASE OF A700-500 HPA N STREAM TROUGH PASSES TO THE NE SUNDAY...WITH ITS ASSOCIATED COLD FRONT PUSHING THROUGH...THEN STALLING NEAR OR JUST TO THE S OF THE AREA BY LATE SUNDAY. THE REGION WILL THEN BE UNDER WNW TO ZONAL FLOW ALOFT SUNDAY NIGHT AND MONDAY. FOR NOW WENT WITH A DRY FORECAST SUNDAY NIGHT/MONDAY...BUT THERE IS THE POSSIBILITY THAT SHORTWAVES EMBEDDED IN THE FLOW ALOFT COULD ACT ON THE FRONTAL BOUNDARY STALLED NEAR BY. HOWEVER...AT THIS TIME DO NOT QUITE HAVE CONFIDENCE IN THIS OCCURRING TO PLACE IN THE FORECAST. FOR TEMPERATURES THURSDAY NIGHT-MONDAY USED A BLEND OF MEX/ECE/ECM/WPC GUIDANCE WITH NAM 2-METER TEMPERATURES BLENDED IN THURSDAY NIGHT AS WELL. TEMPERATURES SHOULD BE ABOVE NORMAL THURSDAY NIGHT-FRIDAY NIGHT...THEN BELOW NORMAL SATURDAY-MONDAY. HOWEVER...DEPARTURES SHOULD NOT BE VERY LARGE...GENERALLY LESS THAN 10 DEGREES.
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&& .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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LOW PRES APPROACHES FROM THE W TODAY AND PASSES S OF LONG ISLAND TONIGHT. VFR TIL THIS AFTERNOON WHEN CIGS LOWER AND PRECIPITATION OVERSPREADS THE REGION. THE PRECIPITATION STARTS AS A MIX OF RASN OR ALL RAIN...THEN CHANGES TO SNOW INTO THE EVE. KSWF LIKELY TO BE MOSTLY SNOW WITH THE EVENT. LIFR POSSIBLE IN THE 22-04Z TIME PERIOD WHEN POTENTIAL WILL BE HIGHEST FOR 1/2SM SN. IMPROVEMENT FROM W TO E TONIGHT. WINDS VEER THRU THIS AFTERNOON...THEN VRB DIRECTION BECOMES NE AS THE LOW APPROACHES THE METRO. THE NE FLOW THEN VEERS TO THE NW AS THE LOW PASSES E OF THE REGION. ...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: OCCASIONALLY GUSTS TO AROUND 15KT POSSIBLE THRU 15Z. KLGA FCSTER COMMENTS: SOME VARIABILITY IN WIND DIRECTION CAN BE EXPECTED THRU 15Z. KEWR FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KHPN FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KISP FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY... .WEDNESDAY-THURSDAY...VFR. .THURSDAY NIGHT-FRIDAY NIGHT...MVFR IN RAIN SHOWERS. .SATURDAY...SUB VFR POSSIBLE IN SHOWERS EARLY...THEN VFR LATE.
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&& .MARINE...
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MADE MINOR CHANGES THIS UPDATE TO REFLECT THE LATEST TRENDS IN OBSERVATIONS AND GUIDANCE. THE FORECAST APPEARS ON TRACK. SCA CONTINUES ON THE OCEAN WATERS...WITH SEAS 5 FT THIS MORNING. THERE MAY BE A LULL THIS AFTERNOON AHEAD OF APPROACHING LOW PRESSURE...BUT THEN HAVE HIGH CONFIDENCE THAT SCA CRITERIA WILL BE MET AGAIN LATE TONIGHT INTO WED...WITH WIND GUSTS IN N-NW FLOW UP TO 30 KT AND SEAS BUILDING TO 5-6 FT IN THE WAKE OF THE LOW PASSAGE. AFTER A LULL FROM WEDNESDAY NIGHT INTO THURSDAY...PERSISTENT SOUTHERLY FLOW COUPLED WITH S SWELL SHOULD BUILD SEAS ON THE COASTAL OCEAN WATERS TO SCA LEVELS LATE THURSDAY AND FRIDAY. SCA LEVEL GUSTS ARE ALSO POSSIBLE ON THE COASTAL OCEAN WATERS FROM LATE THURSDAY INTO FRIDAY AS WELL. AT THIS TIME IT APPEARS THE HARBOR/SOUND/BAYS OF LONG ISLAND SHOULD EXPERIENCE SUB-SMALL CRAFT ADVISORY CONDITIONS TUESDAY NIGHT-FRIDAY.
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&& .HYDROLOGY... QPF OF 2 TO 4 TENTHS OF AN INCH EXPECTED THIS AFTERNOON AND EVENING...WITH SOME OF THIS IN THE FORM OF SNOW ESPECIALLY INLAND. THERE IS ALSO POTENTIAL FOR ABOUT 1/3 TO 1/2 INCH OF RAIN FROM LATE THURSDAY INTO EARLY SATURDAY. RIVERS AND STREAMS ARE EXPECTED TO REMAIN BELOW BANK FULL...BUT INCREASED RIVER/STREAM FLOW ACROSS THE LOWER HUDSON VALLEY AND SOUTHERN CONNECTICUT WILL CONTINUE ICE BREAKUP AND MOVEMENT INTO THIS WEEKEND. ISOLATED ICE JAMS ARE POSSIBLE...WHICH IF THEY OCCUR...COULD RESULT IN LOCALIZED FLOODING. SINCE ICE JAM FLOODING IS UNPREDICTABLE AND SUDDEN...INTERESTS ALONG ICE COVERED RIVERS SHOULD MONITOR NWS FORECASTS FOR THE LATEST INFORMATION. FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEB SITE. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...WINTER WEATHER ADVISORY FROM NOON TODAY TO MIDNIGHT EDT TONIGHT FOR NJZ002. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR ANZ350-353- 355. && $$ SYNOPSIS...GOODMAN/MALOIT NEAR TERM...MALOIT/GOODMAN SHORT TERM...GOODMAN LONG TERM...MALOIT AVIATION...JMC MARINE...GOODMAN/MALOIT HYDROLOGY...GOODMAN/MALOIT

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