Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 290552 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1252 AM EST MON DEC 29 2014 .SYNOPSIS... HIGH PRESSURE SLOWLY BUILDS IN THROUGH FRIDAY...WHILE LOW PRESSURE PASSES WELL TO THE SOUTH ON TUESDAY. ANOTHER LOW PRESSURE SYSTEM APPROACHES NEXT WEEKEND. .NEAR TERM /UNTIL 6 AM THIS MORNING/... A COLD FRONT MOVED THROUGH THE REGION WITH HIGH PRESSURE BUILDING FROM THE WEST AND NORTH OVERNIGHT. MAINLY HIGH CLOUDS REMAIN BEHIND THE FRONT...WITH SOME SC HOLDING ACROSS LONG ISLAND AND INTO NYC. WILL BE SLOW TO CLEAR AS BROAD UPPER TROUGH REMAINS ACROSS CANADA AND INTO THE NORTHERN PORTION OF THE STATES. THE CMC LOOKS TO HAVE A GOOD HANDLE ON THE CLOUDS BASED ON CURRENT IR IMAGERY. BECAUSE THE CLOUDS WILL BE SLOWER TO CLEAR...LOW TEMPS WERE RAISED A FEW DEGREES ACROSS THE AREA AND HOURLY TEMPS WERE ADJUSTED SO THAT THEY REFLECT A SLOWER DROP OFF THAN IN THE PREVIOUS FORECAST. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... HIGH PRESSURE WILL START TO SLOWLY BUILD FROM THE WEST...WITH MOSTLY CLEAR SKIES AND COLDER TEMPS. A WEAKENING SECONDARY COLD FRONT SHOULD MOVE THROUGH FROM THE NORTH ON MON...SO AFTER MIDDAY HIGHS IN THE LOWER/MID 40S...EXPECT SLOWLY FALLING TEMPS MON AFTERNOON AND THEN MUCH COLDER AIR FOR MON NIGHT. LOW TEMPS AT DAYBREAK TUE SHOULD BE NEAR 30 IN MIDTOWN NYC...IN THE 30S MOST ELSEWHERE...AND IN THE UPPER TEENS IN THE COLDER INTERIOR VALLEYS AND LONG ISLAND PINE BARRENS. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... STARTING OFF ON TUESDAY...MORE OF A CONSENSUS IN MODEL GUIDANCE NOW WITH DRY WEATHER PREVAILING. CURRENT AND PREVIOUS RUNS OF CMC...ECMWF...AND GFS KEEP PRECIP WELL SOUTH OF THE REGION IN ASSOCIATION WITH THE WAVES OF LOW PRESSURE RIDING ALONG THE STALLED FRONT. EVEN MAJORITY OF GFS ENSEMBLE MEMBERS KEEP THIS PRECIP SUPPRESSED TO THE SOUTH. OVERALL...QUASI-ZONAL MID TO UPPER LEVEL FLOW THROUGH FRIDAY WITH A RIDGING TREND FOR NEXT WEEKEND. THE MAIN UPPER LEVEL JET WILL BE ALIGNED IN A SIMILAR FASHION AND MOVING SLIGHTLY SOUTH OF THE REGION FOR MIDWEEK BEFORE TRENDING BACK NORTH OF THE AREA FOR THE WEEKEND. AT THE SURFACE...VERY STRONG HIGH PRESSURE OF AT LEAST 1050MB BUILDS INTO THE NORTHWEST PART OF THE COUNTRY AND THIS SINKS SOUTHEAST THROUGH MIDWEEK. THIS WILL BE A SOURCE FOR VERY COLD AIR AND PERIODIC SHORTWAVES WILL MOVE ACROSS THE LOCAL REGION TO HELP WITH ADVECTING THE COLDER AIR MASS INTO THE REGION. THE LOW LEVEL ENVIRONMENT WILL ALSO BECOME VERY DRY AS DIAGNOSED BY FORECAST LAYER PRECIPITABLE WATERS AROUND A TENTH OF AN INCH TUESDAY THROUGH THURSDAY. THIS WILL BE ON AN INCREASING TREND TOWARDS THE WEEKEND BUT AGAIN THERE IS UNCERTAINTY WITH THE FORECAST FOR DAY 7 THROUGH DAY 8 TIME FRAME. THIS UNCERTAINTY IS CONVEYED BY NEARLY A 90 DEGREE PHASE SHIFT BETWEEN CONSECUTIVE RUNS OF THE ECMWF WITH REGARDS TO UPPER LEVEL HEIGHT CONTOUR ORIENTATION. HOWEVER...DID INCREASE POPS A LITTLE WITH AGREEMENT ON PRECIP BETWEEN DGEX...GFS...AS WELL AS SOME GFS ENSEMBLE MEMBERS. JUST A MATTER OF PRECIP TYPE. THIS FORECAST HAS A MIX OF RAIN AND SNOW...SNOW PROBABLY AT ONSET DUE TO WET BULB COOLING AND THEN CHANGING OVER TO RAIN WITH MORE SOUTHERLY FLOW FOR NEXT WEEKEND. HOWEVER...THE CONFIDENCE IS VERY LOW FOR DAY 7 AND DAY 8 TIME FRAME...SO SUBSEQUENT FORECASTS COULD VARY WITH TIMING...PLACEMENT...AS WELL AS PRECIP TYPES. CONCERNING TEMPERATURES...TUESDAY THROUGH THURSDAY IS WHEN THE BULK OF THE COLD AIR MASS IS IN PLACE WITH HIGHS HOVERING NEAR TO SLIGHTLY ABOVE FREEZING ON AVERAGE. NEAR NORMAL TEMPERATURES RETURN BY FRIDAY AND POSSIBLY ABOVE NORMAL FOR THE WEEKEND. AGAIN...LOWER CONFIDENCE WITH TEMPERATURES NEXT WEEKEND DUE TO AFOREMENTIONED UNCERTAINTY. DRY WEATHER IN THE LONG TERM UNTIL NEXT WEEKEND WITH THE NEXT APPROACHING LOW PRESSURE SYSTEM. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... NW FLOW PREVAILS THROUGH THE PERIOD AS HIGH PRESSURE BUILDS IN FROM THE WEST. NW WINDS OF 10 TO 15 KT WITH OCCASIONAL HIGHER GUSTS AT CITY TERMINALS SHOULD LIGHTEN TOWARDS DAYBREAK. NW WINDS AROUND 10 KTS DURING THE DAYTIME...VEERING NNW LATE IN THE DAY/EVE. FOR NYC METRO...WIND DIRECTION WILL PREDOMINATELY BE TO THE RIGHT OF 310 MAGNETIC. VFR CONDITIONS...WITH FEW 030-035 AFTERNOON STRATOCU. .OUTLOOK FOR 00Z TUE THROUGH FRI... .MON NIGHT-WED...VFR. .THU...VFR. SW WIND GUSTS TO 25 KT POSSIBLE. .FRI...VFR. && .MARINE... A MODERATE NW FLOW BEHIND A COLD FRONT WELL SOUTH OF THE FORECAST WATERS WILL BE AROUND SMALL CRAFT LEVELS EAST OF MORICHES INLET. GUSTS MAY BECOME LESS FREQUENT AFTER 08Z...WITH WIND AND WAVES FALLING UNDER SMALL CRAFT LEVELS. FOR NOW WILL CONTINUE WITH THE ADVISORY THROUGH 11Z. AFTERWARD SUB SCA CONDS FORECAST MONDAY THROUGH TUESDAY. SCA CONDS ARE AGAIN POSSIBLE LATE TUESDAY NIGHT THROUGH WEDNESDAY...WITH A BETTER CHANCE WEDNESDAY NIGHT THROUGH FRIDAY...WHEN OCEAN SEAS ARE FORECAST TO REACH 5-7 FT MAINLY EAST OF FIRE ISLAND INLET. THIS WILL BE COINCIDING WITH COLDER AIR MOVING IN AND BETTER MIXING OVER THE RELATIVELY WARMER WATERS. && .HYDROLOGY... NO PRECIPITATION IS EXPECTED THROUGH FRIDAY. WIDESPREAD PRECIP POSSIBLE FOR NEXT WEEKEND...BUT IT IS TOO EARLY TO TELL IF IT WILL BE SIGNIFICANT. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ350. && $$ SYNOPSIS...GOODMAN/JM NEAR TERM...MET SHORT TERM...GOODMAN LONG TERM...JM AVIATION...PW MARINE...MET HYDROLOGY...GOODMAN/JM

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