Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 131120 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 720 AM EDT SUN APR 13 2014 .SYNOPSIS... HIGH PRESSURE REMAINS OFF THE MID ATLANTIC COAST TODAY THROUGH MONDAY. A COLD FRONT MOVES ACROSS TUESDAY EVENING AND PUSHES TO THE SOUTHEAST OF THE REGION LATE TUESDAY NIGHT. THIS FURTHER MOVES SOUTHEAST...AND EVENTUALLY STALLS AND WEAKENS THROUGH FRIDAY. MEANWHILE...HIGH PRESSURE BUILDS IN ACROSS THE REGION FROM THE NORTH AND WEST FOR MID TO LATE IN THE WEEK. LOW PRESSURE APPROACHES FROM THE SOUTH AND WEST FOR NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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INCREASED CLOUDS EARLY THIS MORNING AND MORE SLOWLY DECREASED THEM FROM SOUTH TO NORTH MID TO LATE THIS MORNING. ALSO...TEMP AND DEWPOINT SPREADS HAVE BEEN HIGHER SO TOOK OUT FOG MENTION EARLY THIS MORNING. OTHERWISE JUST SOME MINOR ADJUSTMENTS TO TEMPS AND DEWPOINTS WITH THE FORECAST MAINLY ON TRACK. UPPER RIDGE BUILDS INTO THE REGION WITH RISING HEIGHTS THROUGH MUCH OF THE DAY. MEANWHILE AT THE SURFACE HIGH PRESSURE REMAINS OFF THE MID ATLANTIC WITH AN INCREASING RETURN FLOW ACROSS THE REGION AS LOW PRESSURE IN THE CENTRAL UNITED STATES MOVES SLOWLY TO THE NORTH AND EAST. WEAK WARM ADVECTION CONTINUES THROUGH THE DAY WITH THE RETURN FLOW. SURFACE WIND INCREASES IN RESPONSE TO THE INCREASING PRESSURE GRADIENT. THERE IS A POTENTIAL FOR A FEW GUSTS BUT MAY BE LIMITED AS WARMER AIR MOVES IN ALOFT LIMITING THE MIXING. ONCE AGAIN INLAND AREAS WILL BE MUCH WARMER THAN THE COASTAL REGIONS...ESPECIALLY THE IMMEDIATE SOUTH SHORES. THERE IS A CHANCE THAT SOME FOG WILL DEVELOP LATE IN THE DAY OFFSHORE AND MOVE ONSHORE TOWARD SUNSET. LEANED TOWARD THE HIGHER MET NUMBERS WHICH WERE GENERALLY HIGHER INLAND THEN OTHER GUIDANCE...AND BLENDED PREVIOUS FORECAST HIGHS FOR TODAY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... SURFACE HIGH PRESSURE REMAINS OFF THE MID ATLANTIC TONIGHT INTO MONDAY AS THE SURFACE LOW MOVES NORTH OF THE GREAT LAKES AND THE COLD FRONT MOVES INTO THE OHIO VALLEY. THE STRONG SOUTHERLY FLOW CONTINUES...HOWEVER WARM ADVECTION IS MINIMAL AS AREA REMAIN IN THE WARM SECTOR OF THE LOW. HIGHS MONDAY WILL BE SIMILAR TO SUNDAY HIGHS. DEW POINTS REMAIN IN THE LOWER TO MID 50S. FOG WILL BECOME MORE LIKELY TONIGHT INTO MONDAY AS FOG DEVELOPING OVER THE OCEAN WATERS ADVECTS INLAND. MONDAY EXPECTED TO BE MOSTLY DRY...THERE COULD BE SOME DRIZZLE OR SPRINKLES IN THE AFTERNOON AS LOW LEVEL LIFT INCREASES ACROSS THE REGION. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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MONDAY NIGHT THROUGH TUESDAY NIGHT...MODELS HAVE BEEN CONSISTENT OVER LAST FEW DAYS SHOWING A STRENGTHENING COLD FRONT APPROACHING AND MOVING ACROSS THE REGION TUESDAY EVENING. LAYER PW HAS ALSO BEEN CONSISTENT...STILL CONVEYING 1.25 TO 1.5 INCHES...ABOUT 2 STANDARD DEVIATIONS ABOVE NORMAL FOR THIS TIME OF YEAR...ADDING TO THE POTENTIAL FOR HEAVY RAIN. THIS GOES ALONG WITH THE INCREASING MERIDIONAL FLOW FROM THE APPROACHING TROUGH AND UPPER LEVEL JET ORIENTED SOUTHWEST TO NORTHEAST...TAPPING INTO GULF MOISTURE. THIS INCREASING MOISTURE ADVECTION IS REFLECTED AS WELL WITH THE LOW LEVELS...WHICH WILL HAVE AN INCREASE IN STRATUS AND/OR FOG MONDAY NIGHT INTO TUESDAY MORNING. THE FOG COULD POTENTIALLY BE DENSE AS DEWPOINTS INCREASE AND SEA SURFACE TEMPERATURES WILL STILL BE RELATIVELY COOL. THE STRENGTH OF THE PARENT LOW HAS INTENSIFIED COMPARED TO PREVIOUS RUNS WITH A RESULTING INCREASE IN THE LOW LEVEL JET. NAM SHOWS 70-80 KT AROUND 900MB TUESDAY AFTERNOON AND EVENING WHILE GFS SHOWS 60-70 KT. INVERSION WILL LIMIT GUSTS BUT MODERATE TO HEAVY RAIN MAY HAVE ENOUGH DOWNWARD MOMENTUM TO OVERCOME THE INVERSION AND BRING A FRACTION OF THIS LOW LEVEL JET TO THE SURFACE. THERE IS A POTENTIAL HERE FOR HIGHEST GUSTS IN THE 40-50 MPH RANGE WITH HEAVY RAIN. ALSO...THERE IS A GREATER SIGNAL AMONGST THE MODELS OF LINGERING PRECIP BEHIND THE COLD FRONT WITH A TREND TOWARDS COLDER AIR MOVING IN. THEREFORE...MORE IN THE WAY OF SNOW SHOWERS COULD BE EXPECTED AT THE TAIL END OF THIS EVENT BEFORE ALL PRECIP ENDS. GUSTS WILL BE FREQUENT TOO WITH THE COLD AIR ADVECTION TUESDAY NIGHT WITH THE NORTHWEST FLOW...ALTHOUGH THE GUSTS WILL PROBABLY BE MORE BETWEEN 30-40 MPH WITH THE DECREASING BOUNDARY LAYER WINDS AS THE LOW LEVEL JET WILL HAVE MOVED WELL SOUTHEAST OF THE REGION WITH THE FRONT. SO IN SUMMARY...THERE WILL STILL BE A WIDESPREAD RAIN EVENT WITH THE POTENTIAL FOR HEAVY RAIN AT TIMES ALONG WITH A CHANCE OF STRONG WIND GUSTS OF 40-50 MPH AT TIMES WITH THE HEAVIER RAIN. THE MAIN TIMEFRAME FOR HEAVY RAIN AND WIND POTENTIAL WOULD BE TUESDAY AFTERNOON AND TUESDAY EVENING. LATE TUESDAY NIGHT...ENOUGH COLD AIR COULD MOVE IN FOR LEFTOVER SNOW SHOWERS WITH LIGHT ACCUMULATIONS POSSIBLE NORTH AND WEST OF NEW YORK CITY. TEMPERATURES WILL BE MORE MARGINAL FOR SNOW ACCUMULATIONS CLOSE TO THE COAST...SO NOT EXPECTING ANY ACCUMULATIONS THERE. FOR THE REST OF THE FORECAST...THE COLD FRONT MOVES SOUTHEAST AND FARTHER OFFSHORE LATE TUESDAY NIGHT AND WEDNESDAY...EVENTUALLY STALLING AND WEAKENING WEDNESDAY NIGHT THROUGH THE REST OF THE WEEK. A MUCH COLDER AIRMASS BUILDS IN MID TO LATE WEEK WITH HIGH PRESSURE BUILDING IN FROM THE NORTH AND WEST WITH DRY WEATHER EXPECTED. THE HIGH IS QUITE TRANSIENT...TRAVERSING TO THE NORTH AND EAST OF THE REGION BY THURSDAY NIGHT THROUGH FRIDAY. THE NEXT CHANCE OF RAIN WILL ARRIVE FRIDAY NIGHT INTO NEXT WEEKEND WHEN A LOW FORMS AT THE SOUTHERN END OF THAT STALLED DISSIPATING FRONT IN THE SOUTHEAST U.S. AND APPROACHES THE REGION. CONCERNING TEMPERATURES...DID NOT USE ANY MOS FOR MONDAY NIGHT AND TUESDAY. INSTEAD TEMPERATURES WERE A BLEND OF RAW MODEL TEMPS BETWEEN THE NAM12...GFS40...AND ECMWF. DIURNAL TEMPERATURE TREND WILL BE MINIMAL WITH THE PRECIPITATION. FOR TUESDAY NIGHT USED GMOS WHICH CONVEYS RELATIVELY COLDER TEMPERATURES. THEREAFTER USED THE WPC...GMOS AND ECE GUIDANCE FOR TEMPERATURES. BASICALLY FOR HIGHS...NEAR TO BELOW NORMAL TUESDAY...BELOW NORMAL MID TO LATE WEEK WITH NEAR NORMAL FOR NEXT WEEKEND. FOR LOWS...BELOW NORMAL FOR THE NIGHTS OF TUESDAY THROUGH THURSDAY WITH NEAR NORMAL VALUES THE REST OF THE NIGHTS.
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&& .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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HIGH PRESSURE REMAINS OFFSHORE AS LOW PRESSURE OVER THE CENTRAL UNITED STATES SLOWLY MOVES NORTH AND EAST THROUGH MONDAY MORNING. LOWER MARGINAL VFR CEILINGS DEVELOPED EARLY THIS MORNING UNDER A LOW LEVEL INVERSION...AROUND 2KFT. CEILINGS AT THE NYC AREA TERMINALS EXPECTED UNTIL AROUND 13Z. THEN VFR UNTIL EARLY THIS EVENING. SOUTHERLY FLOW UNDER 10 KT WILL INCREASE THIS MORNING AND INTO THE AFTERNOON WITH SUSTAINED WIND 15 TO 20 KT. SOME HIGHER GUSTS...20 TO 25 KT WILL BE POSSIBLE...ESPECIALLY THIS AFTERNOON. HOWEVER...FREQUENCY AND CONFIDENCE LOW. MARGINAL VFR CEILINGS DEVELOP THIS EVENING...02Z TO 05Z...WITH MARGINAL VISIBILITIES IN FOG AFTER 05Z. THERE IS A CHANCE THAT CEILINGS COULD BECOME IFR...MAINLY AFTER 09Z. HIGHER CONFIDENCE IN CEILINGS AND VISIBILITIES LOWERING TO IFR AFTER 02Z AT KJFK AS FOG MOVES IN OFF THE OCEAN SOON AFTER SUNSET. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .MON...PERIODS OF IFR/LIFR IN LOW CLOUDS AND FOG...ESPECIALLY IN THE MORNING. S WINDS 15-25KT. .MON NGT-TUE...IFR LIKELY WITH RAIN AND FOG. LLWS POSSIBLE. .WED...VFR. .THU...VFR.
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&& .MARINE... WITH HIGH PRESSURE REMAINING OFF SHORE AND LOW PRESSURE OVER THE CENTRAL UNITED STATES MOVING SLOWLY TO THE NORTH AND EAST TODAY THROUGH MONDAY THE SOUTHERLY FLOW ACROSS THE FORECAST WATERS WILL PERSIST. THE FLOW WILL INCREASE TODAY TO 15 TO 20 KT AND CONTINUE INTO MONDAY. WITH A RATHER STRONG INVERSION OVER THE WATERS GUSTS ARE EXPECTED TO BE LIMITED...AND AT TIMES MAY BE AROUND 25 KT. SEAS BUILD ON THE OCEAN WATERS TO SMALL CRAFT LEVELS BY MIDDAY TODAY AND REMAIN AT SMALL CRAFT THROUGH AT LEAST MONDAY. A SMALL CRAFT ADVISORY HAS BEEN EXTENDED THROUGH MONDAY. VISIBILITIES COULD BE A PROBLEM FOR MARINERS TONIGHT AS AREAS OF FOG DEVELOP...WITH VISIBILITIES LOWERING TO 1 TO 11/2NM. THE POTENTIAL EXISTS FOR MORE WIDESPREAD FOG MONDAY WITH VISIBILITIES 1NM OR LESS. FOG ON THE WATERS CONTINUES MONDAY NIGHT INTO TUESDAY...WHICH COULD BE DENSE. RAIN SHOWERS MOVE IN THEREAFTER WITH AN INCREASING SOUTHERLY FLOW AHEAD OF THE COLD FRONT. SCA CONDITIONS WILL BE LIKELY WITH A CHANCE OF GALES LATE IN THE DAY AND ESPECIALLY AT NIGHT WITH GREATER MIXING LENGTH AS A RESULT OF COLD AIR ADVECTION. GALES MAY LINGER INTO EARLY WEDNESDAY BEFORE LOWERING TO SCA IN RESPONSE TO INCOMING HIGH PRESSURE FROM THE NORTH AND WEST. THE HIGH WILL MOVE IN CLOSER TO THE REGION WEDNESDAY NIGHT BEFORE TRAVERSING MORE NORTH AND EAST OF THE WATERS THEREAFTER. THE FLOW WILL SWITCH TO BECOME MORE EASTERLY...WITH MAINLY BELOW SCA WINDS. HOWEVER...RESIDUAL SWELLS AND THIS SWITCH OF FLOW WILL LIKELY KEEP SCA SEAS ON THE OCEAN THROUGH REST OF THE FORECAST PERIOD. && .HYDROLOGY... NEXT WIDESPREAD EVENT IN THE FORM OF MAINLY RAIN TUESDAY THROUGH TUESDAY NIGHT. TOTAL QPF APPEARS RELATIVELY CONSISTENT WITH MODELS RUNS THE PREVIOUS NIGHT...RANGING BETWEEN 1 TO 1.5 INCHES...ECMWF...CMC...AND NAM ON THE LOWER END OF THE RANGE AND GFS ON THE HIGHER END. WITH THE HEAVY RAIN POTENTIAL...LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE...PERHAPS BETWEEN 2-3 INCHES. ANY FLOODING WILL MOSTLY BE MINOR FLOODING OF URBAN...POOR DRAINAGE AND FLASHY SMALL STREAMS. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM EDT MONDAY FOR ANZ350-353-355. && $$ SYNOPSIS...JM/MET NEAR TERM...JM/MET SHORT TERM...MET LONG TERM...JM AVIATION...MET MARINE...JM/MET HYDROLOGY...JM/MET

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