Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 300631 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 231 AM EDT TUE SEP 30 2014 .SYNOPSIS... A COLD FRONT WILL PUSH THROUGH LATE TONIGHT. MULTIPLE UPPER LEVEL DISTURBANCES WILL THEN AFFECT THE NORTHEAST DURING MID WEEK... FOLLOWED BY HIGH PRESSURE BUILDING IN FROM THE NORTH THURSDAY INTO FRIDAY. A COLD FRONT WILL PASS THROUGH ON SATURDAY...FOLLOWED BY HIGH PRESSURE BUILDING IN ON SUNDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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A SHORTWAVE AND VORT MAX MOVING THROUGH THE REGION CONTINUED TO TRIGGER LIGHT RAIN AND SPRINKLES ALONG THE SOUTH SHORE OF LONG ISLAND. MAINTAINED SLIGHT CHANCE POP FOR LONG ISLAND AND MOST OF SOUTHERN CT AS A RESULT. A BACK DOOR COLD FRONT HAD PUSHED THROUGH MOST OF SRN CT AND ERN LONG ISLAND...AND WILL CONTINUE MOVE WEST TO SOUTHWEST THROUGH THE OVERNIGHT...TURNING LOW LEVEL FLOW IN ITS WAKE TO THE E-NE.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
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AS THE BACK DOOR FRONT CONTINUES TO PUSH SLOWLY WSW-WARD AND A WEAK UPPER TROUGH MOVES ACROSS...SHOULD SEE MORE SHOWERS TODAY ESPECIALLY AS THE COMBO OF DAYTIME SFC HEATING AND MID LEVEL COOLING VIA THE UPPER TROUGH INCREASES INSTABILITY. NAM SOUNDINGS SHOW CLOSE TO 500 J/KG SBCAPE...MOSTLY AOB THE FREEZING LEVEL SO NO THUNDER ANTICIPATED ATTM. BUMPED POP UP TO LIKELY MAINLY FOR LONG ISLAND...WITH CHANCE ELSEWHERE. SCT TO NUMEROUS SHOWERS SHOULD CONTINUE TO BE AROUND TONIGHT INTO WED AS AN UPPER LOW APPROACHES FROM THE WEST...THEN MOVES ACROSS ON WED. THE UPPER LOW WILL INTERACT WITH A DEVELOPING INVERTED TROUGH EXTENDING NW-WARD FROM OFFSHORE LOW PRESSURE ON WED... WITH POTENTIAL FOR HEAVY RAIN OF OVER AN INCH NEAR AND JUST EAST OF WHERE THIS INTERACTION OCCURS...WHICH IS STILL UNCERTAIN DUR TO ITS MESOSCALE NATURE. THE 00Z NAM/GFS AND 29/12Z ECMWF WERE POINTING TOWARD SE CT AND ERN LONG ISLAND...WHILE THE LATEST ECMWF HAS SHIFTED JUST TO THE EAST OF THE CWA. CLOUDY SKIES AND AND E-NE FLOW OF MARITIME AIR WILL PERSIST... WITH TEMPS A COUPLE OF DEG ABOVE AVG TODAY...THEN NEAR OR SLIGHTLY BELOW AVG ON WED.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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SHWRS SHOULD END FROM W TO E WED NGT AS THE UPR LOW SLOWLY EXITS. SFC RIDGING EXTENDS SWD FROM ERN CANADA THU AND FRI. THIS WILL KEEP A COOL NE-LY FLOW IN PLACE PRODUCING SEASONAL TEMPS. A MOIST MARINE LAYER BLW THE DRY MID AND UPR LVLS WITH SUBSIDENCE...SO THE SETUP WILL NOT BE CONDUCIVE TO ANY CONVECTION OR SIGNIFICANT PCPN. THE MOST LIKELY SCENARIO WOULD BE A FEW SPRINKLES OR EVEN AREAS OF DZ. HAVE INCLUDED CHC SPRINKLES WHERE THE GREATEST POOLING OF LLVL MOISTURE IS EXPECTED ATTM. MAIN PCPN EVEN IN THE LONG RANGE IS TAKING SHAPE FOR SAT. THE PRIMARY DRIVER IS A STRONG UPR LOW OVER AK WHICH WILL DROP INTO THE GREAT LAKES THRU THE PERIOD. STRONG RETURN FLOW FRI NGT PRODUCES GOOD MOISTURE TRANSPORT INTO THE AREA FOR SAT. THE ASSOCIATED CDFNT AND UPR DYNAMICS THEN PRODUCE A ROUND OF RAIN ON SAT. HAVE INCLUDED LIKELY POPS IN THE FCST. DRY ON SUN. A BLEND OF DETERMINISTIC AND ENSEMBLE DATA INDICATES TEMPS WILL NOT GET OUT OF THE 60S. AS THE BROAD UPR LOW/TROF REACHES THE AREA AROUND MON...THERE IS THE CHC THAT SOMETHING COULD DEVELOP IN RESPONSE. ECMWF HAD A SFC LOW SPINNING UP...AND THE GFS HAS COLD POOL TYPE SHWRS. HAVE INCLUDED SCHC POPS AND CLOUDY SKIES AS A RESULT.
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&& .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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A COLD FRONT IS SLIDING SOUTH ACROSS THE REGION EARLY THIS MORNING. AS OF 06Z THE FRONT WAS JUST NORTH OF THE NEW YORK METRO. THE FRONT SAGS SOUTH OF THE REGION BY DAYBREAK...WITH HIGH PRESSURE BUILDING INTO NORTHERN NEW ENGLAND DURING THE DAY. AREAS OF IFR ARE OCCURRING BEHIND THE FRONT...BUT DO NOT EXPECT THESE TO SPREAD INTO THE IMMEDIATE NY METRO. EXPECT THE IFR AREAS TO DISSIPATE TO VFR AROUND OR JUST AFTER SUNRISE. CONFIDENCE IN LOW ON MARGINAL VFR CIGS THIS AFTN. THESE MAY NOT DEVELOP. SOME LIGHT RA WITH SCATTERED SHOWERS EASTERN SECTIONS TODAY. SFC WINDS IN THE WAKE OF THE FRONT ARE GENERALLY LESS THAN 10 KT FORM THE EAST THROUGH THE DAY. WINDS SHOULD VEER SLIGHTLY TO ESE IN THE AFTERNOON. .OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY... .LATE T0NIGHT...MVFR OR LOWER CIGS POSSIBLE. CHC -SHRA E-NE WINDS AROUND 10 KT. .WED...CHC MVFR CIGS/VSBYS/-SHRA. E-NE WINDS AROUND 10 KT. .THU...CHC MVFR MAINLY AM. NE WINDS AROUND 10 KT. .FRI...VFR. SE-S WINDS AROUND 10 KT. .SAT...RAIN LIKELY - MVFR OR LOWER IN THE AM. SW WINDS AM BECMG WNW PM. GUSTS 20-25KT POSSIBLE.
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&& .MARINE...
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INCREASING E-NE FLOW IN THE WAKE OF A BACK DOOR COLD FROPA...AS THE WATERS BECOME SANDWICHED BETWEEN HIGH PRESSURE TO THE NORTH AND DEVELOPING OFFSHORE LOW PRESSURE...SHOULD LEAD TO SCA CONDS TONIGHT INTO WED NIGHT...AND POSSIBLY THU. ISSUED SCA FOR LATE THIS EVENING THROUGH WED AFTERNOON AS FLOW INCREASES TO 20-25 KT AND SEAS BUILD TO 3-5 FT BY LATE EVENING...AND TO 4-7 FT ON WED. WINDS AND WAVES WILL DECREASE ON FRI...ONLY TO RAPIDLY BUILD AGAIN ON SAT WITH THE APPROACH AND PASSAGE OF A CDFNT. WINDS AND SEAS BLW SCA LVLS ON SUNDAY ATTM.
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&& .HYDROLOGY...
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NO SIGNIFICANT PCPN EXPECTED THROUGH TUE NIGHT. A FEW TENTHS OF AN INCH OF RAINFALL...AND LOCALLY UP TO AN INCH...ARE POSSIBLE WED-WED NGT...MAINLY SE CT AND ERN LONG ISLAND. UP TO AN INCH OF RAIN IS POSSIBLE ON SAT.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$

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