Area Forecast Discussion
Issued by NWS Upton, NY

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829 FXUS61 KOKX 162101 AFDOKX Area Forecast Discussion National Weather Service New York NY 401 PM EST Sun Dec 16 2018 .SYNOPSIS...
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Low pressure tracks from south of Long Island to near Nova Scotia by Monday evening. Meanwhile a series of cold fronts cross the area Monday afternoon and night. Deep low pressure over the Canadian Maritimes Tuesday gives way to high pressure mid week. Another low impacts the area Thursday and Friday, then moves into Canada next weekend.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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A cutoff low tracks to the south then southeast of Long Island through tonight, as its associated low level track pushes off to the east ahead of it. Expect precipitation to taper off from W to E tonight with the exiting of the the low level jet. Across interior zones, the question is how fast does low level cold air work in to change the rain to sleet/snow. For now have the potential for up to an inch of sleet and snow across northern interior zones, but could just as easily see no accumulation if the low level cold air does not arrive in time. Lows tonight should be around 5-10 degrees above normal.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
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Northern stream shortwave ridging crosses the area Monday morning, with associated subsidence keeping things dry. The axis of a northern stream trough then pushes through the area Monday afternoon and then continues to push SE off the Mid- Atlantic and NE seaboard Monday night. Low levels likely will be too dry for any precipitation on downsloping low level NW flow - but given expected low level instability cannot rule out a stray flurry or sprinkle Monday afternoon. It will become quite gusty Monday afternoon and night with gusts of 25-35 mph Monday afternoon and 30-40 mph Monday night. At this time it appears the area should remain below wind advisory criteria Monday night. However, given either slightly stronger cold air advection or a tighter pressure gradient and low end wind advisory gusts could be achieved Monday night both near the coast and at higher elevations inland. Highs on Monday should occur by early afternoon with slowly falling temperatures later in the day. Highs should peak out in the lower to mid 40s and wind chills by late afternoon from the mid 20s to lower 30s. Lows Monday night should be near normal, with wind chills generally in the 10s by late Monday night(around 20 NYC).
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/...
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General model agreement noted as upper ridge and sfc high builds Tuesday-Wednesday ahead of digging shortwave energy that develops into an amplified trough over the Mississippi Valley by Thursday. The sharpening trough looks to close off near the southern Appalachians as a surface low deepens. The low moves north up the Appalachians on Friday. This stacked low lifts northward into Canada next weekend. A warm front approaches and lifts northward Friday, and lagging sfc front/trough passes Saturday as the low traverses well to the north. A noticeably less amplified overall mean flow is expected toward the end of the period. Looks like the best chance for rain occurs later Thursday night and through the day Friday as a broad area of moisture sweeps northward across most of the east coast. Gusty NW winds Tuesday will add to the chill, but winds diminish Tue night and Wednesday as the pressure gradient relaxes. E/SE winds increase Thursday-Thursday night ahead of the warm front, with gusty S/SW winds Friday. These winds veer to the west, and remain rather gusty through the weekend as a tight pressure gradient remains in place. Temps remain right around or slightly below normal Tuesday-Wednesday before rebounding to above normal Thu-Friday. Readings return to normal in CAA behind the storm next weekend, especially Sunday.day.
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&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/...
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Low pressure passes south of the area into the evening before moving up the coast tomorrow. Conditions continue to vary in rain across the area. IFR-MVFR is more common across the NYC terminals, KHPN, KISP and KSWF, with MVFR- VFR elsewhere. These MVFR-VFR conditions may persist into the evening due to drier low level air on the periphery of the high, though conditions will gradually fall by late evening as the high shifts offshore and low pressure begins to dominate. Periods of LIFR will be possible with moderate to briefly heavy rainfall. Conditions gradually improve to MVFR and eventually VFR late tonight as the cold front moves through. As the precipitation comes to an end, some of the rain may mix with sleet or snow. The only place the TAF shows this is at KSWF, elsewhere, confidence is too low to include in the TAF. NE winds will generally be sustained 15 to 20kt with occasional gusts to 25 to 30 kt, highest near the coast. As low pressure begins to move to the east, winds will back to more northerly and then northwest late tonight. Winds will then be strong northwesterly tomorrow following the departure of the system, with the possibility of CIGS 025-035 redeveloping in the afternoon. .OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY... .Monday afternoon/night...Mainly VFR with CIGS 025-035 possible early. NW winds G20-35KT probable. .Tuesday-Wednesday night...VFR. NW Wind G15-25kt possible Tuesday, W- WSW winds G15-20KT possible Wednesday. .Thursday...VFR, possibly becoming MVFR or lower late with rain. LLWS possible late. .Friday...MVFR or lower in rain. SE winds 15-20kt G30kt possible. LLWS.
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&& .MARINE...
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Gale gusts have come to an end over the non-ocean zones, so have issued an SCA there through Monday (gusts up to 30 kt through Monday). Gale gusts should fall off from W to E on the ocean waters as the low level jet exits to the east. So end the Gale at 6pm on the western coastal ocean zone, 9 pm on the central coastal ocean zone and left at midnight end time for eastern coastal ocean zone. There is a chance that the winds could fall off faster than that. Will need to replace with and SCA for the remainder of the night. Gale gusts should return on the ocean waters by Monday afternoon and on all waters Monday night in response to strengthening low level cold advection. So have issued a Gale Watch for Monday and Monday night for the coastal ocean waters and for Monday night for the non-ocean waters. Gusty NW winds persist Tuesday as deep low pressure moves along the Canadian Maritimes and a tight pressure gradient remains in place. Gale force gusts are possible, especially the ocean waters and eastern LI Sound before winds diminish Tuesday night and Wednesday. The diminishing winds are due to high pressure, as it builds over the waters. Winds eventually shift around the S, then E/SE Thursday as the high moves east and a warm front approaches from the south. The warm front likely moves north later Friday. Gusty winds are expected Thursday night through Friday as deep low pressure passes to the west of the local waters. Rough seas Tuesday will subside Wednesday into Thursday. In general, tranquil conditions are anticipated during the mid week period. Seas build once again Thursday night and Friday due to increasing winds.
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&& .HYDROLOGY...
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Between 0.5" and 1.25" of additional rainfall is expected through tonight. Periods of moderate rain are possible through this evening. There is a low chance of minor nuisance/poor drainage flooding through this evening as a result. The next chance for significant rainfall of at least a half an inch is expected to occur late in the week (Thursday night-Friday). Still too early to determine if there will be any hydrologic concerns with this potential late week event.
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&& .EQUIPMENT... NYC Central Park winds are out of service until further notice. Loss of data is due to a severed cable. Parts are on order. NYC NOAA Weather Radio Station KWO35 (162.55 MHz) will remain off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Gale Watch from Monday evening through late Monday night for ANZ330-335-338-340-345. Small Craft Advisory until 6 PM EST Monday for ANZ330-335-338- 340-345. Gale Watch from Monday morning through late Monday night for ANZ350-353-355. Gale Warning until 9 PM EST this evening for ANZ353. Gale Warning until 6 PM EST this evening for ANZ355. Gale Warning until midnight EST tonight for ANZ350.
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&& $$ SYNOPSIS...Maloit/PW NEAR TERM...Maloit SHORT TERM...Maloit LONG TERM...PW AVIATION...MD MARINE...Maloit/PW HYDROLOGY...Maloit/PW EQUIPMENT...

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