Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 280631 AFDOKX Area Forecast Discussion National Weather Service New York NY 131 AM EST Tue Feb 28 2017 .SYNOPSIS... A warm front approaches tonight and lifts through the area on Tuesday. Another warm front will then move through Tuesday night. The warm front will lift well to the northeast on Wednesday, followed by a strong trailing cold front late Wednesday into Wednesday night as intensifying low pressure moves northeast up the Saint Lawrence River valley. The low will move across the Canadian Maritimes on Thursday, followed by weak high pressure Thursday night. A weak Alberta Clipper low may move across or pass just south on Friday, followed by high pressure passing to the south for the weekend. Another low pressure system will begin to approach on Monday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Biggest challenge tonight will be with the amount of cloud cover, at least through the first half of the night. Satellite trends over the last few hours have shown some dissipation of clouds over eastern PA with mostly clear skies across New England. This has allowed for temperatures drop more then forecast due to better radiational cooling conditions. However, warm advection increases overnight and there will be an approaching 700-500 hPa shortwave. These factors should lead to clouds overspreading the region after midnight. A warm front is also progged to approach the tri-state area tonight as well, just reaching the southern portion of the CWA towards daybreak. Associated isentropic lift ahead of this front looks too weak with the given moisture depth, especially below 850mb, to produce any rainfall. Have continued with a dry forecast. Overall, low temperatures will end up above normal. A few outlying locations could fall into the lower 30s before remaining steady or slowly rising due to weak warm advection and increasing clouds. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... The warm front pushes through Tuesday morning. So after a cloudy start, it appears we get into at least partial sunshine. Higher- level clouds probably filter the sunshine until lower clouds shift in from the west and possibly from off the ocean as well late in the day. Isentropic lift is a little stronger this time around, but moisture still isn`t very deep. Will at least go with a slight chance of light rain for southern and western sections. An onshore flow will limit mixing particularly for coastal sections, but it will still end up well above normal for high temperatures. Most of the area ends up in the 50s, and expecting parts of the city and NE NJ to top the 60 degree mark. For Tuesday night, isentropic lift becomes stronger as another warm front moves through, plus there will be additional lift from a mid level shortwave passing through. Models vary with the depth and placement of moisture, but feel confident enough to go with the likelihood of rainfall for at least a short period during the night. The amount and density of fog that occurs during the night becomes a tricky forecast. On one hand, low level wind profiles look too strong for widespread or dense fog, but surface dewpoints around 50 advecting over sea surface temperatures in the low to mid 40s could result in advection fog in spite of this. Will go with areas of fog in the forecast and keep vsbys above dense. Will go with a non-diurnal temperature trend during the night with the warm front moving through. Low temperatures will be warmer than normal highs. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... As a warm front lifts to the north Wed morning, light rain and areas of fog will slowly diminish. With the area in the warm sector and partial sunshine for late morning and early afternoon, expect an unseasonably mild day with high temps on the high side of MOS guidance, with lower 70s from NYC west and into the 60s elsewhere. There could be enough instability for some isold-sct convection from NYC metro west by midday, but the main push for strong to possibly severe tstms expected late day into early evening well in advance of the approaching front. Faster GFS timing was preferred here over the 00Z ECMWF, though it appears the 12Z ECMWF is trending toward the GFS. Damaging winds the main threat here, though with model fcst strong of 0-1 km shear and strong SW winds aloft, could not rule out other modes especially inland NW of NYC as was the case this past Saturday. The threat area will also extend a little farther east than it did on Sat as low level flow will be SW rather than SE, extending to at least Nassau/Fairfield and possibly into northern New Haven and westernmost Suffolk, which is in agreement with the latest SPC Day 3 Outlook. Cold fropa will take place later Wed night, with strong cold air advection and temps cooling through the night and perhaps not rising much if at all daytime Thu, with highs in the 40s to near 50. Expect a cold night Thu night with diminishing winds and lows in the 20s to lower 30s. Models differ somewhat on track of a weak Alberta Clipper low dropping into the base of the longwave trough that becomes established over the east for Fri, with the GFS bringing it right through with a potential light snowfall, and the ECMWF/CMC taking a more southerly track. Will continue to carry chances for a light snowfall. Fair and cold wx expected to last for one more day into Sat, then Sunday/Monday are shaping up to be on the mild side as high pressure passes offshore and SW return flow becomes established. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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Primarily VFR today as high pressure builds farther offshore and a warm front approaches from the SW. Light and variable winds overnight will back around to the E-SE by daybreak. Winds gradually pick up through the day, but generally less than 10KT. A strong SW low-level jet approaches late Tuesday night with low-level wind shear likely at the coastal terminals with 50KT winds at 2000 ft. Generally VFR this afternoon, but a few showers could bring brief MVFR conditions this afternoon for city and eastern terminals, but confidence was not high enough to put in TAFs. The greatest uncertainty is with how quickly cigs lower, eventually to widespread IFR/LIFR Tuesday evening. .OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY... .Tuesday night-Wednesday morning...Areas of fog with rain. MVFR/IFR and possibly lower. LLWS possible with SW winds 45-55 kt at 2kft. SW winds G15-20KT possible Wednesday morning. .Wednesday afternoon-Wednesday night...Showers and a chance of thunderstorms. MVFR or lower possible. SW winds G20-30KT. Winds become westerly late Wednesday night. .Thursday...VFR. W-NW winds G25-35KT. .Friday...MVFR/IFR possible with a chance of light snow. NW winds G20-25KT. .Saturday...VFR. NW G20-25KT.
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&& .MARINE... Winds on the ocean have diminished with speeds around 10 kt. Ocean seas are generally 3 to 4 ft, although 44017 has seas just under 5 ft. Do not think this will continue and seas should subside to around 4 ft overnight. Otherwise, winds and seas will continue below advisory criteria until late Tuesday night. Will hold off on headlines for this event with it starting late in the 3rd period and allow the midnight shift to issue any headlines as appropriate. For the longer term, increasing SW flow on Wed will likely result in SCA conds for all waters, and perhaps minimal gales on the outer ocean waters. The better chance for gales on the ocean will come after a strong cold frontal passage late Wed night into Thu, then again late day Fri into Fri night with the passage of a weak Alberta Clipper low, with SCA conds on the remaining waters. SCA conds should last on all waters into Sat, then remain confined to the ocean Sat night. && .HYDROLOGY... Rainfall from late Tuesday through Wednesday night should run from 1/2 to 1 inch, with locally higher amounts double that possible that could cause localized minor flooding. Release from spring snow melt is occurring down the Connecticut and Housatonic Rivers. && .CLIMATE... Record highs for Wednesday March 1 Location.......Record High/Year Set.....Forecast High Newark..................75/1972...............73 Bridgeport..............59/1972...............63 Central Park............73/1972...............71 LaGuardia...............68/1972...............69 J F Kennedy.............58/2004*..............67 Islip...................60/2004...............65 * = and in previous years Record high minimum temperatures for Wednesday March 1 Location....Record High Min/Year Set.....Forecast Low Newark..................43/1976...............54 Bridgeport..............41/1976...............48 Central Park............45/2004...............54 LaGuardia...............44/2004...............52 J F Kennedy.............42/1974*..............50 Islip...................39/2016...............50 * = and in previous years && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JC/Goodman NEAR TERM...JC/DS SHORT TERM...JC LONG TERM...Goodman AVIATION...JE/DW MARINE...JC/Goodman/DS HYDROLOGY...JC/Goodman CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.