Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 310446 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1246 AM EDT TUE MAR 31 2015 .SYNOPSIS... A COLD FRONT MOVES OFFSHORE TONIGHT...FOLLOWED BY A QUICK MOVING LOW PASSING TO THE SOUTH ON TUESDAY. HIGH PRESSURE WILL BUILD ACROSS THE AREA ON WEDNESDAY AHEAD OF A FRONTAL SYSTEM MOVING INTO THE PLAINS. THE FRONTAL SYSTEM WILL THEN PROGRESS SLOWLY ACROSS THE AREA FROM LATE THURSDAY INTO EARLY SATURDAY. HIGH PRESSURE WILL RETURN LATER THIS WEEKEND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... INITIAL COLD FRONT MOVED OFFSHORE EARLIER THIS EVENING. HOWEVER...A SECONDARY COLD FRONT IS CURRENTLY MAKING ITS WAY ACROSS THE REGION. THIS FRONT IN COMBINATION WITH A MID LEVEL SHORTWAVE HAS ALLOWED ISOLD/SCT SHOWERS TO MOVE INTO PARTS OF NE NJ...NYC METRO AND SOUTHERN. THESE RAIN SHOWERS SHOULD DIMINISH BY 06Z. THEREAFTER EXPECT CLEARING SKIES...AND DIMINISHING W TO WNW FLOW. LOWS WILL BE IN THE UPPER 20S INLAND AND IN THE LONG ISLAND PINE BARRENS...30-35 MOST ELSEWHERE...AND MID/UPPER 30S INVOF NYC. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... ALBERTA CLIPPER LOW NOW MOVING FROM THE NRN MISSISSIPPI VALLEY TOWARD THE UPPER GREAT LAKES WILL CONTINUE SE...REACHING THE NRN MID ATLANTIC BY TUE AFTERNOON. EXPECT TUE MORNING TO BE DRY WITH INCREASING CLOUDS...THEN PRECIP SHOULD OVERSPREAD THE AREA IN THE AFTERNOON. HAVE LIKELY/CAT POP FOR NEARLY THE ENTIRE CWA...EXCEPT FOR SOUTHERN CT AS THERE IS SOME UNCERTAINTY AS TO HOW FAR NORTH THE ASSOCIATED PRECIP SHIELD WILL EXTEND SINCE NWP GUIDANCE SHOWS BEST WAA AND H5 FORCING PASSING MAINLY OVER NYC METRO/LONG ISLAND AND POINTS SOUTH. PRECIP DURING THE DAYLIGHT HRS SHOULD BE MAINLY RAIN FOR NYC METRO AND LONG ISLAND...BUT INLAND THERE IS SOME UNCERTAINTY AS TO PRECIP TYPE. ATTM EXPECT AN ELEVATION-DEPENDENT SNOWFALL...WITH A COLD RAIN OR A RAIN/SNOW MIX IN THE LOWER ELEVATIONS...AND MOSTLY SNOW IN THE HIGHEST ELEVATIONS. P-TYPE SHOULD TREND MORE TOWARD SNOW THROUGHOUT BEFORE ENDING AS THE BOUNDARY LAYER COOLS VIA WET-BULB COOLING AND AN INCREASING COLDER NORTHERLY FLOW. ATTM EXPECT LITTLE TO NO ACCUMULATION IN NYC METRO...NO MORE THAN A COATING MOST ELSEWHERE AND UP TO AN INCH IN THE HIGHEST ELEVATIONS. THE WORST-CASE SCENARIO WOULD BE A COATING OF ACCUMULATION IN NYC...UP TO AN INCH MOST ELSEWHERE...AND 1-2 INCHES IN THE HIGHER ELEVATIONS. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A PROGRESSIVE...YET SOMEWHAT AMPLIFIED UPPER FLOW ACROSS THE LOWER 48...WILL BE FEATURED DURING THE PERIOD. THIS WILL RESULT IN SEVERAL SWINGS IN THE TEMP REGIME AS WE GO FROM BELOW NORMAL AT THE START OF THE PERIOD...TO ABOVE NORMAL AHEAD OF AN APPROACHING FRONTAL SYSTEM AT THE END OF THE WEEK...FOLLOWED BY YET ANOTHER SHOT OF UNSEASONABLY COLD AIR AT THE END OF NEXT WEEKEND. THERE ARE ALSO SOME TIMING ISSUES...IN PARTICULAR WITH THE FRONTAL SYSTEM AT THE END OF THE WEEK. THE GFS IS MORE AGGRESSIVE WITH A RAINFALL WITH A FRONTAL WAVE...WHILE THE ECMWF HAS THAT WAVE DISPLACED FARTHER NORTH AND WEST. EVEN SO...BOTH THE 12Z GFS AND ECMWF DRY CONDITIONS OUT BEHIND THE COLD FRONTAL PASSAGE ON SAT. THE DIFFERENCES ARISE DUE TO THE TIMING OF THE PAC SHORTWAVE ENERGY. THE SPECIFICS OF SUCH CAN NOT BE WORKED OUT THIS EARLY IN THE FORECAST PROCESS. PREFERENCE WAS TO TAKE A MIDDLE GROUND APPROACH WITH THE TIMING OF THE LATE WEEK SYSTEM. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... A COLD FRONT MOVES EAST TONIGHT AS LOW PRESSURE QUICKLY APPROACHES FROM THE WEST TUESDAY. STRONG GUSTS ASSOCIATED WITH LIGHT RAIN SHOWERS AND BEHIND A SECONDARY COLD FRONT WILL DIMINISH AS THE NIGHT PROGRESSES. THE LIGHT SHOWERS ARE EXPECTED THROUGH MIDNIGHT. OTHERWISE...VFR CONDITIONS AS SKIES GRADUALLY CLEAR. AFTER THE INITIAL GUSTS AT A FEW AIRPORTS...WEST WINDS WILL CONTINUE...GENERALLY REMAINING UNDER 10 KT. CLEAR SKIES TUESDAY MORNING WILL GIVE WAY TO INCREASING MID CLOUDS BY EARLY AFTERNOON. THEN RAIN OR A RAIN/SNOW MIX TO THE NORTH DEVELOPS AFTER 19-21Z. AS SUCH...CONDITIONS WILL QUICKLY DETERIORATE TO MVFR OR EVEN IFR. WEST WINDS IN THE MORNING LIGHTEN DURING THE AFTERNOON...BECOMING VARIABLE. .OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY... .TUESDAY NIGHT...CONDS IMPROVING TO VFR BY MIDNIGHT TUESDAY NIGHT. .WEDNESDAY-THURSDAY...VFR. .THURSDAY NIGHT-FRIDAY NIGHT...MVFR IN RAIN SHOWERS. .SATURDAY...SUB VFR POSSIBLE IN SHOWERS EARLY...THEN VFR LATE. && .MARINE... SCA CONTINUES ON THE OCEAN WATERS...EASTERN SOUND...AND PECONIC AND GARDINERS BAYS. OCEAN SEAS 4-6 FT AND MAY INCREASE ANOTHER FT BY DAYBREAK. GUSTS OUT EAST AFTER FROPA SHOULD REACH SCA LEVELS. GUSTS TO 25 KT LOOK TO BE ONLY BRIEF/OCNL IN NATURE THIS EVENING ON THE WRN SOUND AND SOUTH SHORE BAYS. SCA CONDS COULD LAST ON THE OCEAN THROUGH TUE NIGHT...AND ALSO RETURN TO THE ERN WATERS TUE NIGHT...AS LOW PRESSURE PASSES TO THE S AND NORTHERLY FLOW INCREASES IN ITS WAKE. THEN EXPECT SUB-SMALL CRAFT LEVEL CONDITIONS WED THROUGH THU AS A WEAK PRESSURE GRADIENT REMAINS OVER THE REGION. WIND GUSTS AND WAVES INCREASE TO SMALL CRAFT LEVELS AHEAD OF THE NEXT SYSTEM APPROACHING THE OCEAN WATERS THURSDAY NIGHT INTO SATURDAY. && .HYDROLOGY... QPF OF 1/10 TO 1/4 INCH EXPECTED TUE AFTERNOON AND EVENING. THERE IS THE POTENTIAL FOR WIDESPREAD RAINFALL AT THE END OF THE WEEK WITH A FRONTAL WAVE ALONG A SLOW MOVING FRONTAL SYSTEM. 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...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ330-340-350- 353-355. && $$ SYNOPSIS...GOODMAN/DW NEAR TERM...GOODMAN SHORT TERM...GOODMAN LONG TERM...DW AVIATION...PW MARINE...GOODMAN/DW HYDROLOGY...GOODMAN/DW

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