Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 310531 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1231 AM EST SAT JAN 31 2015 .SYNOPSIS... LOW PRESSURE WILL DEEPEN WELL OFF THE NEW ENGLAND COAST THROUGH SATURDAY...WHILE POLAR HIGH PRESSURE BUILDS IN FROM THE WEST. A COLD FRONT WILL MOVE THROUGH ON SUNDAY AS DEEPENING LOW PRESSURE APPROACHES FROM THE OHIO VALLEY. THE LOW PASSES SOUTH OF LONG ISLAND MONDAY AND THEN FAR OFFSHORE MONDAY NIGHT WITH HIGH PRESSURE BUILDING IN ITS PLACE. THE HIGH MOVES ACROSS TUESDAY AND OFFSHORE TUESDAY NIGHT. A COLD FRONT MOVES ACROSS MIDWEEK WITH ANOTHER LOW PASSING WELL OFFSHORE LATE IN THE WEEK. BY THAT TIME FRAME...HIGH PRESSURE WILL BE CENTERED WEST OF THE REGION. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... WINDS ACROSS THE INTERIOR HAVE REALLY DIMINISHED LATE THIS EVENING. ALTHOUGH LOW OVER THE GULF OF MAINE WILL CONTINUE TO DEEPEN OVERNIGHT AND COLD ADVECTION WILL CONTINUE...THINK IT WILL BE TOUGH TO GET WIND ADVSY LEVEL WINDS HERE ANYMORE. SO AM CANCELLING THE ADVSY ACROSS INTERIOR PORTIONS OF THE LOWER HUDSON VALLEY AND INTERIOR SOUTHERN CT. REST OF ADVSY REMAINS IN EFFECT ALTHOUGH CONDS NOW LOOK MARGINAL. ALSO CUT BACK ON END TIME OF THE HAZARD ON SAT. GFS HAS BEEN TOO STRONG THIS EVE AND NAM HAS BEEN A BETTER FIT...WITH 00Z SOUNDINGS SUPPORTING WINDS DIMINISHING EARLIER WHICH WAS ALSO THE CASE OF THE 18Z RUN. DESPITE THE CANCELLATION OF THE WIND ADVSY...SFC WINDS WILL STILL REMAIN HIGH ENOUGH TO KEEP THE WIND CHILL ADVSY AS IS. A FEW ZONES MAY FALL JUST SHORT...BUT IT`S STILL CLOSE ENOUGH TO KEEP IT. THE COMBINATION OF STRONG WINDS AND LOW TEMPS INTO THE SINGLE DIGITS INLAND...AND AROUND 10 AT THE COAST...PRODUCES WIND CHILLS OF 10 TO AROUND 15 BELOW ZERO. REGARDLESS...IT WILL BE BITTERLY COLD AND PRECAUTIONS WILL NEED TO TAKEN IF EXPOSED TO THESE ELEMENTS FOR ANY LENGTH OF TIME. FOR OVERNIGHT LOWS...PREFERENCE WAS TOWARD A BLEND OF THE COLDER MET MOS AND NAM 2M TEMPS. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... STRONG NW FLOW CONTINUES ON SAT AS LOW PRESSURE LIFTS UP INTO THE CANADIAN MARITIMES AND POLAR HIGH PRESSURE BUILDS IN FROM THE WEST. GFS IS ALREADY TOO HIGH WITH THE WINDS AND MAY BE OVERDOING IT ON SAT AS WELL. THEREFORE...THE WIND ADVSY MAY BE UP TOO LONG AND MAY SCALE BACK ON THE TIMING LATER THIS EVE. PREFERENCE WAS TOWARD A BLEND OF THE COLDER MET MOS AND NAM 2 M TEMPS WITH HIGHS 15 TO 20. HIGH PRESSURE SLIDES ACROSS THE AREA SAT NIGHT AND THEN OFFSHORE SUN AS DEEPENING LOW PRESSURE APPROACHES FROM THE OHIO VALLEY. CLOUDS WILL INCREASE LATE SAT NIGHT INTO SUN WITH A LOW CHANCE OF SNOW DEVELOPING AHEAD OF THE SYSTEM BY LATE SUN AFT/EARLY EVE. LOWS SAT NIGHT WILL BE CONSIDERABLY WARMER...BUT STILL BELOW NORMAL WITH LOWS IN THE TEENS. WEST WINDS WILL ALSO CONTINUE TO DIMINISH. HIGHS ON SUN WILL BE IN THE LOW TO MID 30S. STAYED CLOSED TO A MET/MAV MOS BLEND. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... THE MAIN FOCUS OF THE LONG TERM IS THE STORM SYSTEM SUNDAY NIGHT THROUGH MONDAY. THE CHANCE OF PRECIPITATION IS VERY HIGH AND LOOKS TO BE MAINLY SNOW. THE SNOW FORECAST HAS A TOTAL OF GENERALLY 6-12 INCHES IN THIS TIME FRAME...HIGHEST ACROSS SOUTHERN CT AND LOWER HUDSON VALLEY...LOWEST ACROSS LONG ISLAND. HOWEVER...THESE SPECIFIC SNOW AMOUNTS ARE UNCERTAIN AND THE CONFIDENCE LEVEL IS AROUND 40-45 PERCENT...THE HIGHER PERCENTAGE BEING ACROSS THE INTERIOR ZONES. BECAUSE OF THIS AFOREMENTIONED UNCERTAINTY AND LOWER CONFIDENCE...HELD OFF ON THE WINTER STORM WATCH. THERE ARE MORE FEATURES THAT GO INTO THE CURRENT LOWER CONFIDENCE LEVEL. ONE...A PROGRESSING MID LEVEL SHORTWAVE THAT DOES NOT CLOSE OFF. IT EXHIBITS A RATHER POTENT MAGNITUDE BUT SWIFTLY MOVES ACROSS MONDAY. THE HIGHEST POSITIVE VORTICITY ADVECTION WILL BE GOING INTO MONDAY MORNING SO THE SNOW WILL PROBABLY BE THE HEAVIEST DURING THIS TIMEFRAME. TWO...THIS EVENT IS STILL BEYOND THE 36-48 HOUR TIMEFRAME THAT IS TYPICAL OF A WATCH. THE FORECASTS GOING INTO MONDAY MORNING HAVE EXHIBITED WIDE VARIANCE IN THE POSITION OF THE LOW ON THE ORDER OF ABOUT 100 TO 200 MILES. THIS HAS BEEN CONVEYED IN THE NAM...CMC BETWEEN THE LAST TWO RUNS AND THE ECMWF 12Z COMPARED TO 12Z YESTERDAY. THIS WILL MAKE ALL THE DIFFERENCE IF FOR EXAMPLE A FURTHER NORTHWARD TREND IS MADE WITH THE MODELS RUNS TONIGHT. THE NAM AND PARALLEL NAM HAVE ALREADY SHOWN A MORE NORTHWARD TREND THAT POSES A CHANCE FOR A WINTRY MIX ACROSS SOME COASTAL SECTIONS. THIS HAS BEEN REFLECTED IN THE FORECAST SO THIS IS A VERY COMPLEX ONE. THREE...INGREDIENTS FOR THIS SYSTEM HAVE YET TO COME TOGETHER FROM WESTERN CANADA AND SOUTHWEST MEXICO. THESE WILL COMBINE SATURDAY AND SATURDAY NIGHT. THINKING THE BETTER SAMPLING TONIGHT INTO SATURDAY WILL YIELD LESS VARIANCE IN FUTURE MODEL RUNS. AFTER THIS SYSTEM...MONDAY NIGHT UNTIL MIDWEEK...WE WILL BE IN A QUASI-ZONAL MID LEVEL FLOW. A WEAK LOW AMPLITUDE SHORTWAVE MOVES ACROSS TUESDAY WITH A LARGER MORE AMPLIFIED SHORTWAVE MOVING APPROACHING WEDNESDAY NIGHT. THERE WILL BE AN ASSOCIATED COLD FRONT AT THE SURFACE APPROACHING WEDNESDAY NIGHT INTO THURSDAY. THERE WILL BE A CHANCE OF SNOW WITH THIS. FOR LATE IN THE WEEK...A LOW PRESSURE AREA MOVES FAR OFFSHORE...MORE OFFSHORE WITH THE 12Z ECMWF RUN TODAY...BUT DID NOT WANT TO TOTALLY MAKE FOR A DRY FORECAST. LEFT IN A CHANCE OF MAINLY SNOW FOR THURSDAY INTO FRIDAY. HOWEVER...THE MODELS HAVE CONVEYED MORE OF A PROGRESSIVE SOLUTION AND LESS AMPLIFIED THAN BEFORE SO THE LOW IS NOT THAT STRONG OFFSHORE AND HIGH PRESSURE COULD PROVE TO BE MORE DOMINANT IN ALLOWING FOR A DRIER FORECAST. FOR HIGH TEMPERATURES...BELOW NORMAL OVERALL...MAINLY IN 20S EXCEPT FOR WEDNESDAY AND THURSDAY WITH LOW TO MID 30S. LOWS ARE FORECAST TO BE TEENS TO LOWER 20S SUNDAY NIGHT AND WEDNESDAY NIGHT. FOR OTHER PERIODS...LOW TEMPERATURES ARE FORECAST AS FOLLOWS...SINGLE DIGITS TO A LITTLE BELOW ZERO MONDAY NIGHT...SINGLE DIGITS TO LOWER TEENS TUESDAY NIGHT...LOW TO MID TEENS THURSDAY AND FRIDAY NIGHT. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE SLOWLY BUILDS IN FROM THE WEST THROUGH THE FORECAST PERIOD. VFR. GUSTY NORTHWEST WIND AROUND 310 TRUE...WITH GUSTS 30KT TO 37KT. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .LATE SATURDAY NIGHT-SUNDAY...VFR. .SUNDAY NIGHT-MONDAY...POTENTIAL HIGH IMPACT DAY. IFR AND SNOW LIKELY. CHC MIXED PCPN. NE-N G 25-35KT POSSIBLE. .MONDAY NIGHT...BECOMING VFR AS SNOW COMES TO AN END. N-NW WIND G20-25KT POSSIBLE. .TUESDAY-WEDNESDAY...VFR. && .MARINE... NW GALES WILL CONTINUE ON THE WATERS OVERNIGHT INTO SAT MORNING. THE EASTERN OCEAN WATERS COULD APPROACH STORM FORCE GUSTS. THE COMBINATION OF STRONG WINDS AND COLD WATER TEMPS FROM THE MID 30S TO LOWER 40S WILL ALSO RESULT IN AT LEAST MODERATE FREEZING SPRAY DURING THIS TIME FRAME. GUSTY WINDS WILL DIMINISH SATURDAY NIGHT INTO SUNDAY. SEAS WILL RESPOND BY SUBSIDING THROUGH THIS TIME FRAME. MARGINAL 5 FT SEAS MAY CLIP THE EASTERNMOST OCEAN WATERS S OF MONTAUK INTO SUNDAY...BUT SUB SCA CONDITIONS ARE LIKELY ACROSS THE WATERS SUNDAY. OVERALL...ROUGH CONDITIONS SUNDAY NIGHT THROUGH WEDNESDAY. WINDS AND SEAS INCREASE LATE SUNDAY NIGHT INTO MONDAY MORNING. OCEAN SEAS INCREASE TO 6 TO 11 FT THROUGH THE DAY MONDAY...AND LAST INTO MONDAY NIGHT. THE WIND GUSTS REACH 25 KT LATE SUNDAY NIGHT WITH GALES QUITE POSSIBLE MONDAY INTO MONDAY NIGHT. THESE CONDITIONS GRADUALLY TAPER DOWN EARLY TUESDAY. THE RELATIVELY MORE QUIET PERIOD LOOKS TO BE LATE TUESDAY MORNING THROUGH EARLY WEDNESDAY MORNING. THERE COULD BE SOME MARGINAL SCA SEAS ON THE OUTER OCEAN TUESDAY OF AROUND 5 FT. SCA CONDITIONS POSSIBLE ONCE AGAIN WITH THE APPROACH OF THE COLD FRONT TOWARDS MIDWEEK. && .HYDROLOGY... GENERALLY AROUND 0.6 TO 1.2 INCHES OF LIQUID FORECAST WITH THE SYSTEM SUNDAY NIGHT THROUGH MONDAY. MAINLY A SNOW EVENT FORECAST...SO NO HYDROLOGIC ISSUES EXPECTED. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...WIND ADVISORY UNTIL 10 AM EST THIS MORNING FOR CTZ009>012. WIND CHILL ADVISORY UNTIL NOON EST TODAY FOR CTZ005>007-009- 010. NY...WIND ADVISORY UNTIL 10 AM EST THIS MORNING FOR NYZ069>075- 078>081-176>179. WIND CHILL ADVISORY UNTIL NOON EST TODAY FOR NYZ067>071. NJ...WIND ADVISORY UNTIL 10 AM EST THIS MORNING FOR NJZ002-004-006- 103>108. WIND CHILL ADVISORY UNTIL NOON EST TODAY FOR NJZ002-004-103- 104. MARINE...FREEZING SPRAY ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ330- 335-338-340-345-350-353-355. GALE WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ330-335-338- 340-345-350-353-355. && $$ SYNOPSIS...JM/DW NEAR TERM...DW SHORT TERM...DW LONG TERM...JM AVIATION...MPS/MET MARINE...JM/DW HYDROLOGY...JM/DW

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