Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 280228 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 928 PM EST FRI FEB 27 2015 .SYNOPSIS... HIGH PRESSURE BUILDS INTO THE REGION THROUGH SATURDAY NIGHT. A FRONTAL SYSTEM WILL MOVE ACROSS THE AREA SUNDAY NIGHT INTO MONDAY. HIGH PRESSURE WILL THEN BRIEFLY RETURN ON TUESDAY BEFORE YET ANOTHER FRONTAL SYSTEM IMPACTS THE AREA FOR THE MIDDLE OF NEXT WEEK. HIGH PRESSURE BUILDS BACK IN FOR THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... FORECAST BASICALLY ON TRACK - COLD & DRY. HIGH PRESSURE RESULTS IN A CLEAR SKY AND LIGHT NW SFC FLOW (CALM AT TIMES). THE BOUNDARY LAYER HAS STARTED TO DECOUPLING (8 AT FOK AND 9 AT DXR AS OF 02Z) WHICH ALWAYS MAKES DETAILED HOURLY TEMPERATURE FORECASTS VERY DIFFICULT. BY MORNING...EXPECTING AROUND ZERO FOR INTERIOR VALLEYS AND THE PINE BARRENS OF LONG ISLAND. THE CITY AND IMMEDIATE SURROUNDING AREAS ARE EXPECTED TO DROP TO AROUND 15 F. NOT EXPECTING TO REACH THE RECORD LOWS THAT WERE SET LAST YEAR. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... NO CHANGES AT THIS TIME. FOR THE LAST DAY OF THE METEOROLOGICAL WINTER...SUNNY TO START ON SATURDAY...THEN THERE COULD BE SOME MID-HIGH CLOUDS FILTERING IN DURING THE AFTERNOON. SUBSIDENCE FROM THE APPROACHING HIGH PRESSURE CENTER WILL LIMIT THE MIXING HEIGHT BY ABOUT 25MB VERSUS TODAY...AND WITH A SIMILAR TEMP EXPECTED AT THE TOP OF THE BOUNDARY LAYER WITH LESS OF A DOWNSLOPE FACTOR...HIGHS EXPECTED TO BE A FEW DEGREES COOLER THAN TODAY. A NAM/MAV MOS BLEND MATCHES THIS THINKING. THIS IS ABOUT 15-20 DEGREES COLDER THAN NORMAL. ANY CLOUD COVER REMAINING BY EARLY SATURDAY EVENING SHOULD SHIFT OUT TO THE EAST...THEN A PERIOD OF CLEAR CONDITIONS BEFORE MID-HIGH CLOUDS BEGIN TO RETURN LATE AT NIGHT. THE LACK OF CAA AND THE LATE NIGHT CLOUD INCREASE SHOULD PREVENT TEMPS FROM FALLING AS LOW AS THEY WILL TONIGHT IN SPITE OF MORE WIDESPREAD CALM WINDS. STILL...LOWS AVERAGING 10-15 DEGREES BELOW NORMAL. && .LONG TERM /SUNDAY THROUGH FRIDAY/... RAISED POPS SLIGHTLY BASED ON TRENDS IN THE NWP AND MOVE UP THE START SLIGHTLY. 18Z GFS IS NOW FASTER AND CLOSER TO NAM WITH THE ONSET OF PCPN LATE SUNDAY - SUGGESTING MORE OF A MID AFTN ONSET. 21Z SREF ALSO NOW SUGGESTING AN EARLIER START. FROM PREVIOUS...GLOBAL MODELS CONTINUE TO BE ON BOARD FOR A CHANGE IN THE UPPER AIR PATTERN WITH THE PERSISTENT HIGH AMPLITUDE RIDGE ACROSS NORTH AMERICA FINALLY BREAKING DOWN. THIS WILL RESULT IN A SPLIT CONFLUENT FLOW ACROSS THE EASTERN HALF OF THE COUNTRY. BY MID WEEK...RIDGING BEGINS TO EXPAND NORTHWARD FROM THE GULF COAST STATES...AND A DIGGING UPPER TROUGH TRANSLATES EAST FROM THE PLAINS STATES. THIS WILL RESULT IN AN ACTIVE PATTERN WITH A SERIES OF FRONTAL SYSTEMS TO IMPACT THE AREA...THE FIRST SUN NIGHT INTO MON...THEN ANOTHER TUE NIGHT INTO THU. THE LATTER OF WHICH DIFFERS IN THE SYSTEM PROGRESSION AMONGST THE GLOBAL MODELS. THE 12Z GFS CONTINUES TO BE ON THE FASTER SIDE OF THE ENVELOPE. PREFERENCE WAS TO TAKE A MIDDLE ROAD SOLUTION...WHICH IN TIMING WAS CLOSE TO THE GGEM. THE FIRST SYSTEM IS A FAST MOVING LOW ACROSS THE GREAT LAKES SUN INTO SUN NIGHT PRECEDED BY STRONG WARM ADVECTION. THE UNCERTAINTY LIES IN THE PLACEMENT OF THE SFC LOW WHICH THE GFS AND ECMWF TRACK TO THE NORTH OF THE AREA...WHILE THE NAM WRF AND GGEM HINT AT A WEAK SECONDARY LOW FORMING TO THE SOUTH SUN NIGHT. THIS MAY MAKE FOR A CHALLENGING RAIN/SNOW LINE...WHICH RIGHT NOW LOOKS TO BE IN CLOSE PROXIMITY TO THE LI/NY METRO AFTER MIDNIGHT. THE NAM SOLUTION WOULD KEEP THE LOW-LEVEL COLD WITH A NLY FLOW AND RESULT IN A PERIOD OF FREEZING RAIN. RIGHT NOW...LOOKING FOR 2 TO 4 INCHES OF SNOWFALL ACROSS THE LOWER HUDSON VALLEY AND CT...WITH 1 TO 2 INCHES AND A LIGHT ICE ACCRETION TO THE SOUTH. CONDITIONS DRY OUT MON MORNING WITH A GUSTY NW FLOW AND ANOTHER SHOT OF UNSEASONABLY COLD AIR...ALBEIT WARMER THAN IN RECENT WEEKS. STRONG HIGH PRESSURE BRIEFLY BUILDS IN TUE WITH ANOTHER FRONTAL SYSTEM TO BRING OVERRUNNING PCPN TO THE AREA TUE NIGHT INTO WED. THIS TIME AROUND WARMER HEIGHTS ALOFT AND SW FLOW WILL RESULT IN A QUICK TRANSITION OVER TO RAIN FROM SOUTH THE NORTH. KEPT CHANCES OF PCPN IN THE FORECAST THROUGH WED NIGHT DUE TO THE UNCERTAINTY WITH THE PROGRESSION OF THE SYSTEM. THERE IS THE POSSIBILITY OF A TRANSITION BACK TO WINTRY PCPN WED NIGHT. THE WEEK COMES TO AN END ON A COLD...BLUSTERY NOTE...WITH READINGS WELL BELOW NORMAL AS THE UPPER TROF REESTABLISHES ITSELF ACROSS EASTERN NORTH AMERICA. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE BUILDS IN THROUGH SATURDAY...THEN OVER THE AREA SATURDAY NIGHT. VFR THROUGH THE TAF PERIOD. WNW WINDS 10 TO 15 KT WITH OCCASIONAL GUSTS TO 20 KT THROUGH AROUND 06Z AT CITY TERMINALS. WINDS SUBSIDE TO 10 KT OR LESS AFT 06Z. WINDS GENERALLY RIGHT OF 310 MAGNETIC SAT MORNING...BACKING TO LEFT OF 310 MAG AFTER 18-20Z. LIGHT AND VARIABLE WINDS SAT EVENING. .OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY... .SAT NIGHT-SUN MORN...VFR. .SUN AFTN-EARLY MON MORN...MVFR OR LOWER IN -SN CHANGING TO A WINTRY MIX COAST AND -SN INLAND SUN NIGHT. SE SFC WND G15-20KT POSSIBLE SUN AFTN. .MON-TUE MORN...VFR. NW WINDS G15-25KT MON AFTN/EVE. .TUE AFTN-WED...IFR POSSIBLE IN -SN CHANGING TO A WINTRY MIX TUE NGT. RA LATE TUE NGT/WED MORN. BECOMING VFR LATE WED. LLWS POSSIBLE TUE NGT-WED. && .MARINE... SWELL WILL BE DIMINISHING INTO TONIGHT...AND WITH ALL AREA BUOYS REPORTING JUST BELOW 5 FT. WINDS INCREASE SLIGHTLY TONIGHT AS THE PRESSURE GRADIENT TIGHTENS...BUT STILL BELOW SCA CRITERIA. WINDS WILL BE OFFSHORE...SO WAVE HEIGHTS SHOULD CONTINUE TO FALL AS THE SWELL SUBSIDES. BY SAT AFTN...WINDS SUBSIDE BELOW 10 KT AND REMAIN THAT WAY THROUGH SAT NIGHT AS A HIGH PRESSURE CENTER MOVES OVERHEAD OR NEARBY LATE AT NIGHT. SEAS BUILD TO SMALL CRAFT LEVELS ON MONDAY...WITH AN INCREASING SOUTHWEST FLOW IN THE MORNING. NORTHWEST FLOW BEHIND A COLD FRONT WILL LIKELY PRODUCE GUSTS TO SMALL CRAFT LEVELS ON THE OCEAN WATERS ON MONDAY. && .HYDROLOGY... THERE IS THE POTENTIAL FOR A LIGHT TO MODERATE SNOW EVENT LATE SUNDAY INTO MONDAY MORNING. THIS EVENT WILL HAVE NO IMMEDIATE IMPACT ON THE HYDROLOGIC SERVICE AREA. ICE WILL CONTINUE TO DEVELOP ON LOCAL AREA RIVERS AND STREAMS AS TEMPERATURES REMAIN WELL BELOW AVERAGE. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...JC/DW NEAR TERM...TONGUE SHORT TERM...JC LONG TERM...DW AVIATION...NV MARINE...JC/DW HYDROLOGY...JC/DW

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