Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 210258 AFDOKX Area Forecast Discussion National Weather Service New York NY 1058 PM EDT Thu Oct 20 2016 .SYNOPSIS... A warm front will slowly approach from the south tonight. A cold front will move through late Friday. Deepening low pressure will track across New England Friday night into Saturday, then spin over Quebec this weekend. A cold front will pass through on Monday, followed by building high pressure through the middle of the week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Stratus has moved in from the south. Persistent E/SE flow to the north of the warm front continues overnight. Amplifying trough approaches from the west. Generally expect low clouds to persist through the overnight hours. Spotty light rain or drizzle is possible, along with the development of fog. Analysis of NWP and high resolution models does not suggest any organized area of rain other than the aforementioned spotty light rain/drizzle. However, as moisture gets pulled northward well ahead of a subtropical low east of the Bahamas, a few showers could develop later tonight. With the clouds and easterly wind flow, temperatures tonight should be fairly uniform for this time of year, with lows ranging from the lower/mid 60s near the coast, to the upper 50s inland.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Amplifying trough tracks east as it becomes negatively tilted, and cuts off Friday night. At the surface, frontal boundary and wave of low pressure tracks east across the area by afternoon. Low pressure over the Atlantic lifts northward, passing to the east. A warm front also tracks northward ahead of the frontal boundary. The front moves slowly east of the area Friday night as surface low develops across eastern New England and deepens. Coverage of showers remains in question, and axis of heavier rain is in doubt. However, latest 12Z model suite does look drier overall. Marginal CAPE could be enough for isolated thunder Friday afternoon as lift increases ahead of the trough. Temperatures will be warm, in the lower to mid 70s during the day, falling into the 50s at night. They could be lower depending on speed of the front, and any cooler air arriving late at night. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Windy and cooler weather expected this weekend as low pressure deepens over New England and Quebec on Saturday, then drifts toward Labrador Sunday night. The GFS, GEM and ECMWF are all very similar with the evolution of the system, suggesting a 500 millibar closed low develops over central Pennsylvania Friday night, tracks into upstate New York on Saturday, and then north of Quebec City on Sunday. For Saturday, the synoptic lift will be exiting the region. However, very steep low level lapse rates will develop. In fact, the GFS progs superadiabatic lapse rates in the approximately 15-21Z time period. This should result in at least broken cloud cover and scattered showers. Across the northern tier, there may be enough moisture to result in greater coverage and perhaps some periods of steady rain. This precipitation will have to overcome the downslope however on top of the synoptic subsidence, so limited the rain to scattered showers. Because of the expected cloud cover, this should help to temper wind gusts a bit. As a result, wind gusts were capped at around 40 mph. This is essentially full mixing from 950 millibars in the GFS. The best chance at this time for over-performing winds reaching advisory criteria looks to be Saturday morning as the pressure rapidly rises. The precipitation winds down Saturday night as the low and associated moisture gets too far away, but the gusty winds will continue right through Sunday with the low still in the 980s over Canada. A clipper type system will be racing towards the forecast area on Monday. This will allow winds to back to the southwest and may allow a quick warm up if the cold frontal passage is slow enough. The 12Z data however has the front coming through during the early afternoon at the latest, so high temperatures close to those expected on Sunday were forecast. The airmass that builds in for the Tuesday and Wednesday time period looks to be around 10 degrees below average, and will have the potential to produce a freeze across much if not all of the interior, possibly getting into some of the coastal zones. A frontal system of Pacific origin may reach the area on Thursday per the ECMWF. A slower timing is preferred for this type of a system this far out however, so precipitation chances were limited to slight chance. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/...
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A warm front lifts to the north, followed by a cold front approaching from the west on Friday. MVFR-IFR conditions this evening, lowering to LIFR after midnight. Exception is KHPN where LIFR/VLIFR should persist through the night. City/Long Island terminals probably last to reach LIFR. Confidence in LIFR remains high at KHPN, low-moderate at city/Long Island Terminals, and moderate elsewhere. Conditions should improve to IFR by mid- late morning then probably to MVFR early to mid afternoon. VFR conditions may return before 00z for all but KGON. E winds diminish this evening, becoming light and variable at all but KJFK/KLGA, where should back to the SE at under 10 kt. Winds become E-SE at under 10 kt by mid morning Friday. Winds could become light and variable again by late Friday afternoon/early Friday evening. .Outlook for 00Z Saturday through Tuesday... .Friday Night...MVFR or lower possible along with isolated to scattered showers. Showers with MVFR or lower conditions likely. NW winds G30-35KT developing late Friday night. .Saturday...Becoming VFR. WNW-NW winds G25-30KT likely. .Saturday Night...Most likely VFR with very low chance of MVFR. WNW-W winds G30-35KT likely. .Sunday...VFR. W winds G25-30KT likely. .Sunday Night-Monday Night...VFR with isolated to scattered showers possible. WNW-NW winds g20-25 kt possible at eastern terminals Sunday night. NW winds g20-25KT possible Monday/Monday Night. .Tuesday...VFR with NW winds g20-25KT possible.
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&& .MARINE... Extended SCA out east through tonight seas remain around 5 ft. A frontal boundary slowly moves across the waters Friday, as winds eventually turn toward the south. Expect a wind shift Friday night, generally after midnight, to the west. Seas build over the ocean Friday night, and a few gusts could approach 25 kt late at night. SCA in effect west of Moriches Inlet for this. Gales are possible over the weekend as deep low pressure spins north of the waters. A gale watch has been issued for Saturday and Saturday night, and gales may also extend into Sunday. A cold frontal passage on Monday will have the potential to produce SCA conditions though Tuesday, especially on the ocean where seas are likely to at least remain in the 3-5 ft range. && .HYDROLOGY... Rainfall tonight should be light in spotty light rain or drizzle. Showers are possible Friday and Friday night. Totals should average around 1/2 an inch. No hydrologic problems are expected. Less than a quarter of an inch of precipitation is expected over the weekend. Mainly dry weather is expected thereafter. && .TIDES/COASTAL FLOODING... The potential remains for isolated minor coastal flooding with the Fri afternoon high tide cycles. Generally 1-2 ft departures are needed for minor flooding. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Gale Watch from Saturday morning through late Saturday night for ANZ330-335-338-340-345-350-353-355. Small Craft Advisory from 6 PM Friday to 6 AM EDT Saturday for ANZ353-355. Small Craft Advisory until 6 AM EDT Friday for ANZ350. && $$ SYNOPSIS...JMC/PW NEAR TERM...Goodman/PW SHORT TERM...PW LONG TERM...JMC AVIATION...Maloit MARINE...JMC/Goodman/PW HYDROLOGY...JMC/PW TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.