Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 212057 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 357 PM EST SUN DEC 21 2014 .SYNOPSIS...
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HIGH PRESSURE REMAINS NORTHEAST THROUGH MONDAY NIGHT AS LOW PRESSURE APPROACHES FROM THE SOUTH. HIGH PRESSURE REMAINS NORTHEAST THROUGH MONDAY NIGHT AS LOW PRESSURE APPROACHES FROM THE SOUTH. THE WAVE OF LOW PRESSURE WEAKENS WHILE MOVING NORTH TUESDAY AND TUESDAY NIGHT. A MORE SIGNIFICANT STORM SYSTEM AFFECTS THE AREA TUESDAY NIGHT THROUGH EARLY CHRISTMAS DAY WITH A COLD FRONT PASSING THROUGH LATE WEDNESDAY NIGHT INTO THURSDAY MORNING. HIGH PRESSURE BUILDS IN LATE THURSDAY THROUGH FRIDAY. A WEAK COLD FRONT MOVES THROUGH DRY SATURDAY. ANOTHER LOW APPROACHES FROM THE SOUTH SUNDAY.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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CHALLENGING FORECAST DUE TO SUBTLE WEAK FEATURES...AND AMPLE LOW LEVEL MOISTURE PRESENT. MODELS ARE IN GENERAL AGREEMENT AS UPPER SHORTWAVE DEPARTS TO THE EAST...WITH RIDGING EXPECTED LATE TONIGHT. SFC TROUGH OVER THE EASTERN ZONES LINGERS INTO TONIGHT...AND GLOBAL MODELS DO OUTPUT LIGHT QPF THROUGH MUCH OF THE OVERNIGHT. IF PRECIP DOES INDEED OCCUR...THIS MAY BECOME PROBLEMATIC WITH REGARD TO PRECIPITATION TYPE FORECASTING. SFC TEMPS ARE EXPECTED TO HOLD STEADY OR FALL SLIGHTLY TONIGHT. AS MENTIONED...MOISTURE IS RATHER SHALLOW...AND THERE IS A CONCERN THAT ANY PRECIPITATION LATER THIS EVENING AND INTO THE OVERNIGHT THAT DOES FALL WILL BE LIQUID. IF SO...SCATTERED SPRINKLES/DRIZZLE COULD FREEZE ON CONTACT WITH THE COLD SURFACE WHERE TEMPS FALL BELOW THE FREEZING MARK. OTHERWISE...IF MOISTURE IS DEEP ENOUGH TO SUPPORT SNOW...VERY LIGHT SNOW OR FLURRIES WILL BE THE RESULT. HOWEVER...COMPLICATING THINGS IS THAT TEMPS THROUGH 850 HPA OR SO WARM SLIGHTLY AS THE NIGHT PROGRESSES. SO EVEN IF MOISTURE IS DEEP ENOUGH TO SUPPORT SNOW PRODUCING PROCESSES...ANY PRECIP MAY CHANGE OVER THE RAIN ANYWAY AS THE NIGHT WEARS ON. OTHERWISE...CLOUDS LIKELY LINGER THROUGH THE NIGHT...BUT THESE LOW CLOUDS COULD BREAK UP SOMEWHAT AS RIDGE BUILDS. TEMPS ARE A BLEND OF LATEST MOS AND FORECAST DATABASE.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
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UPPER RIDGE BUILDS AHEAD OF DIGGING MID WEST TROUGH. HIGH PRESSURE REMAINS ANCHORED OVER THE CANADIAN MARITIMES THROUGH MONDAY NIGHT. A WEAK AREA OF LOW PRESSURE DEVELOPS ALONG A WARM FRONT OFF THE MID ATLANTIC...DRIFTING NORTHWARD TOWARD THE AREA. WEAK LOW LEVEL LIFT WILL RESULT IN CHANCE POPS FOR LIGHT RAIN THROUGH THE PERIOD. DO NOT EXPECT REAL HIGH COVERAGE AT THIS TIME. TEMPS WARM INTO THE MIDDLE 30S MONDAY ACROSS THE INTERIOR...WITH LOWER TO MIDDLE 40S EXPECTED NEAR THE COAST. THESE TEMPS LIKELY REMAIN STEADY MONDAY NIGHT DUE TO EAST FLOW AND CLOUDY SKIES.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/...
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WEAK LOW TO THE SOUTH CONTINUES TO WEAKEN TUESDAY AS A WARM FRONT DEVELOPS ASSOCIATED WITH A DEEPENING LOW OVER THE MIDWEST AND LOWER MISSISSIPPI RIVER VALLEY. ALL GUIDANCE DOES NOT MAINTAIN A CLOSED CIRCULATION AS PREVIOUSLY FORECAST. OTHERWISE THERE IS GENERALLY CONSISTENCY WITH THE MIDWESTERN LOW DEEPENING AND TRACKING NORTHWARD TUESDAY NIGHT THROUGH THURSDAY MORNING AS THE FULL LATITUDE UPPER TROUGH BECOMES NEGATIVELY TILTED. ONLY CHANGE HAS BEEN A SLIGHTLY SLOWER COLD FRONTAL PASSAGE ACROSS THE REGION. CURRENTLY FORECAST TO COME THROUGH JUST AFTER 06Z THURSDAY...AND CLEAR THE EASTERN ZONES JUST AFTER 12Z CHRISTMAS DAY. ALSO...BOTH THE GFS AND ECMWF PROFILES ARE SLIGHTLY WARMER THAN YESTERDAY AND ALL RAIN IS EXPECTED FOR THE EVENT. WITH A STRONG LOW LEVEL JET LATE WEDNESDAY INTO WEDNESDAY NIGHT AND STRONG LIFT PERIODS OF HEAVY RAINFALL CAN BE EXPECTED. ALSO THERE WILL BE A DEEP INFLUX OF GULF OF MEXICO AND ATLANTIC MOISTURE AHEAD OF THE TROUGH. UP TO 2 INCHES WILL LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE. SEE HYDROLOGY SECTION. IN THE COLDER AIR BEHIND THE FRONT THURSDAY WINDS AND GUSTS INCREASE BUT ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS. HIGH PRESSURE BUILDS IN FOR FRIDAY. THEN A WEAK COLD FRONT CROSSES THE REGION SATURDAY...HOWEVER THE PASSAGE IS EXPECTED TO NOW BE DRY. A WAVE OF LOW PRESSURE DEVELOPS ON THE FRONT ACROSS THE GULF COAST STATES LATER SATURDAY AND TRACKS NORTH SUNDAY BRINGING THE NEXT CHANCE OF PRECIPITATION. THE STORM WILL BE INLAND AND THE AREA WILL BE ON THE WARM SIDE WITH ALL LIQUID PRECIPITATION EXPECTED.
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&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/...
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WEAK SURFACE TROUGH ACROSS THE AREA AND LOW-LEVEL MOISTURE TRAPPED BENEATH AN INVERSION WILL RESULT IN WIDESPREAD MVFR CONDITIONS THROUGH MON...WITH EVEN SOME LOCATIONS BEING IFR. POCKETS OF LIGHT RAIN/DRIZZLE/SNOW WILL POSSIBLE THROUGH THE EVENING DUE TO THE AFOREMENTIONED TROF...MAINLY EAST OF THE NYC TERMINALS. A WEAK NLY FLOW AT LESS THAN 10 KT GRADUALLY VEERS AROUND TO E/NE BY MON AFT. .OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY... .MONDAY AFTERNOON-MONDAY NIGHT...MVFR OR LOWER POSSIBLE IN E FLOW. RAIN DEVELOPING IN THE AFTERNOON AND AT NIGHT. .TUESDAY-TUESDAY NIGHT...IFR CIGS/VSBYS LIKELY IN RAIN. E WINDS 10-20 KT...BECOMING SE. .WEDNESDAY...HIGH IMPACT EVENT BECOMING LIKELY. IFR CONDS WITH HEAVY RAIN AND S/SE WINDS 15-20 KT WITH 20-25 KT GUSTS. WINDS SHIFT TO THE SW LATE WEDNESDAY NIGHT. .THURSDAY...SUB-VFR CONDS IN THE MORNING IN RAIN SHOWERS. VFR CONDS BY AFTERNOON. WEST WINDS 15-20 KT WITH 25-35 KT GUSTS. .FRIDAY...VFR.
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&& .MARINE...
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LIGHT NORTHERLY WINDS CONTINUE TONIGHT...SLOWLY SHIFTING EAST AS HIGH PRESSURE REMAINS WELL NORTHEAST OF THE WATERS. A WEAK AREA OF LOW PRESSURE DEVELOPS OFF THE MID ATLC COAST AND DRIFTS NORTHWARD TOWARD THE WATERS MONDAY AND MONDAY NIGHT. EAST WINDS INCREASE SLIGHTLY BUT SHOULD REMAIN BELOW SCA THRESHOLDS. SEAS REMAIN 4 FT OR LESS OVER THE OCEAN WATERS THROUGH MONDAY NIGHT. A PERSISTENT EASTERLY FLOW INTO TUESDAY WILL ALLOW FOR SEAS ON THE OCEAN WATERS TO BUILD TO SMALL CRAFT LEVELS AHEAD OF AN APPROACHING WARM FRONT. WIND AND GUSTS ARE EXPECTED TO REMAIN BELOW ADVISORY LEVELS TUESDAY INTO TUESDAY NIGHT. A DEEPENING LOW PRESSURE SYSTEM OVER THE MIDWEST WEDNESDAY WILL RESULT IN AN INCREASING SOUTHERLY FLOW AND WIND AND GUSTS WILL INCREASE TO SMALL CRAFT LEVELS ACROSS ALL THE WATERS BY LATE WEDNESDAY. THEN WEDNESDAY NIGHT THE WIND GUSTS ON THE OCEAN INCREASE TO GALE FORCE. A COLD FRONT ASSOCIATED WITH THE LOW PASSES THROUGH THE WATERS LATE WEDNESDAY NIGHT INTO EARLY THURSDAY MORNING. SOUTHERLY WIND SHIFTS TO THE WEST TO NORTHWEST AND BECOMES VERY GUSTY IN THE COLDER AIR. GALE FORCE GUSTS WILL BECOME LIKELY ACROSS ALL THE WATERS DURING THURSDAY AND THEN SUBSIDE TO BELOW GALE FORCE THURSDAY NIGHT...AND POSSIBLY BELOW SMALL CRAFT DURING FRIDAY AS HIGH PRESSURE BUILDS IN. A WEAK COLD FRONT COMES THROUGH DRY SATURDAY...AND WIND AND SEA ARE LIKELY TO BE BELOW SMALL CRAFT LEVEL.
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&& .HYDROLOGY...
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NO SIGNIFICANT PRECIPITATION IS EXPECTED THROUGH MONDAY...MAINLY JUST LIGHT AMOUNTS. RAINFALL FROM MONDAY AFTERNOON THROUGH THURSDAY MORNING COULD TOTAL 1 1/2 TO 2 INCHES WITH LOCALLY HIGHER AMOUNTS. MUCH OF THE RAINFALL IS EXPECTED TO OCCUR WEDNESDAY INTO WEDNESDAY NIGHT. MINOR URBAN AND POOR DRAINAGE FLOODING IS POSSIBLE. DRY WEATHER RETURNS THURSDAY AFTERNOON THROUGH SATURDAY NIGHT.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...MET/PW NEAR TERM...PW SHORT TERM...PW LONG TERM...MET AVIATION...DW MARINE...MET/PW HYDROLOGY...MET/PW

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