Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 161051 AFDOKX Area Forecast Discussion National Weather Service New York NY 551 AM EST Thu Nov 16 2017 .SYNOPSIS... A weak wave of low pressure moves through the area today, followed by a cold front tonight. High pressure briefly builds through late week before another strong low pressure system impacts the area this weekend. High pressure once again builds to the south for early week, followed by a cold front by mid week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Updates this morning to lower QPF amounts across the area. Looking at 1045Z water vapor imagery, mid-upper level moisture is quickly accelerating eastward ahead of where current precipitation is developing. As such, drier air aloft may hinder a heavier scenario. A potent short wave noted on water vapor over the Great Lakes Region is leading to strong upper difluence, with pressure falls noted on surface analysis across western NY/PA and eastern NY into CT, where two surface lows are expected to deepen as the system progresses eastward. There is remarkably good consistency between deterministic, ensemble and hi resolution solutions that the precipitation field across the Hudson Valley into eastern PA and NJ will expand ahead of the deepening surface trough/weak cold front, coincident with moisture advection in strengthening southerly flow aloft. For the most part, any moderate precipitation will be through the area by around noon, with drier air advecting in aloft thereafter rapidly reducing rainfall intensity. Temperatures may briefly rise again as skies begin to clear in westerly flow, though rises will be short- lived as a secondary but stronger cold front pushes east. It is possible that a brief shower or two will accompany the frontal passage as low-level instability increases, though otherwise expect a sharp drop in temperatures and an increase in wind and gust strength by evening.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Despite clearing skies and the advection of a cooler arctic air mass, winds will remain strong through much of the night which will likely hinder temperatures from falling too far below normal. Should winds subside sooner than forecast, particularly across the lower Hudson Valley, seasonably cool temperatures may be possible overnight. The pressure gradient will remain tight through much of the day as the low departs into eastern Canada and high pressure builds to the west. Temperatures will be close to normal to a few degrees below, with dry conditions and mostly sunny skies as dry air advects southeastward. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A progressive upper flow will continue into next week. That being the case, there will be multiple interactions with short waves between the polar branches for brief amplification. The first being with jet energy interaction between the southern and northern branches Saturday night into Sunday across the Great Lakes region. This results in the formation of a negatively tilted upper trough/closed low lifting across eastern Canada Sunday into Monday. At the surface, a strong cold front works through the region Sunday morning. Preference continues to be toward the slightly slower ECMWF and GGEM, with the GFS having trended in that direction over the last couple of day. Both pre- and post- frontal winds could gusts up to 40 mph Saturday afternoon through Sunday. While there will be decent warm advection ahead of the system Saturday, dry low-levels will likely limit coverage of any precipitation. Best lift and heaviest rainfall likely comes overnight Saturday along and ahead of the cold front with the potential for up to half an inch. There is some weak elevated instability, so an isolated rumble of thunder is possible. Higher rainfall amounts are possible should the system close off sooner. Deepening low pressure tracking across eastern Canada Sunday into Monday and high pressure building to the southwest will result in a prolonged period of gusty west winds. Another fast moving frontal system approaches on Tuesday and passes through on Wednesday. Latest ECMWF is more amplified and somewhat slower than the GFS. GGEM is even slower. Model consensus was followed at this juncture in time. Temperatures will fluctuate through the period with multiple frontal boundaries in the fast flow. It will be above normal Saturday into Saturday night, then trending down Sunday into Monday behind the departing storm over eastern Canada. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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A warm front and wave of low pressure approach the region early this morning, followed by a cold frontal passage later this morning. Intensifying low pressure tracks up the New England Coast through tonight, with a tight W/NW gradient in it wake over the region. MVFR ceilings expected to develop from W to E early this morning. Showers are moving into the area with conditions likely deteriorating to IFR during the morning push. Showers end with improvement to VFR late this morning into early afternoon from W to E in wake of cold front. E/SE winds will increase to 10 to 15 kt with occasional gusts to 20 kt across coastal terminals early this morning, shifting to SW after frontal passage. Timing of windshift in TAFS could be off by 1 to 2 hrs, and winds may be backed more than indicated in the morning depending on proximity of low pressure to the region. Otherwise...W/WNW winds expected to increase to 15 to 20 kt with gusts to 25-30 kt this afternoon and continuing through Thu Eve push. Occasional peak gusts to 35 kt. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: IFR conditions likely develop for morning push, with windshift from E/SE to SW. Timing in TAFS may be off by 1 to 2 hrs. Occasional gusts this afternoon may be higher than forecast. The afternoon KJFK haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: IFR conditions likely develop for morning push, with windshift from E/SE to SW. Timing in TAFS may be off by 1 to 2 hrs. Occasional gusts this afternoon may be higher than forecast. The afternoon KLGA haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: IFR conditions likely develop for morning push, with windshift from E/SE to SW. Timing in TAFS may be off by 1 to 2 hrs. Occasional gusts this afternoon may be higher than forecast. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: IFR conditions likely develop during morning push, with windshift from E/SE to SW. Timing in TAFS may be off by 1 to 2 hrs. Occasional gusts this afternoon may be higher than forecast. KHPN TAF Comments: IFR conditions likely develop during morning push, with windshift from E/SE to SW. Timing in TAFS may be off by 1 to 2 hrs. Occasional gusts this afternoon may be higher than forecast. KISP TAF Comments: IFR conditions likely develop during morning push, with windshift from E/SE to SW. Timing in TAFS may be off by 1 to 2 hrs. Occasional gusts this afternoon may be higher than forecast. .OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY... .Late Tonight-Friday...VFR. NW winds G25-30KT with occasional peak gusts to 35 kt, subsiding to 20 to 25 kt Friday. .Saturday...Sub VFR conditions possible by the afternoon and becoming likely towards evening. S-SW winds G25-35KT. .Sunday...Conditions improve to VFR. NW winds G25-30KT. .Monday...VFR. NW winds 20-25KT.
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&& .MARINE... Winds will rapidly strengthen behind a frontal system today, allowing seas to build into Friday as the pressure gradient remains tight. These winds will strengthen to gales by tonight and continue into much of Friday before subsiding from west to east as high pressure builds into the area. A brief quiet period expected Fri night into Sat morning, then S-SW winds should quickly ramp up on the ocean waters Sat afternoon and on the remaining waters Sat night. Winds on the ocean waters may gust close to gale force Sat night ahead of an approaching cold front. Gales are likely on all waters on Sunday after the cold frontal passage, followed by an extended period of SCA conditions Mon into Mon night. && .HYDROLOGY... A quarter to three quarters of an inch of rain is expected across eastern Long Island and southeast Connecticut this morning, with lesser amounts further west. There is the potential for around half an inch of rainfall Saturday night along and ahead on approaching cold front. && .TIDES/COASTAL FLOODING... A coastal flood statement has been issued for the south shore back bays of Queens and Nassau county for Thursday morning high tide. This is due to a strengthening SE flow tonight leading to water levels just touching minor coastal flooding benchmarks. Elsewhere, water levels are likely to fall short. There is a small chance the statement will need to be upgraded to an advisory if trends in tide levels are higher than currently expected. Winds shifting to the W and NW Thursday afternoon and evening will significantly lower water levels through the end of the week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 1 PM this afternoon to 6 PM EST this evening for ANZ330-335-338-340-345. Gale Warning from 6 PM this evening to 6 AM EST Friday for ANZ330-335-338-340-345. Small Craft Advisory from 10 AM this morning to 6 PM EST this evening for ANZ350-353-355. Gale Warning from 6 PM this evening to noon EST Friday for ANZ353-355. Gale Warning from 6 PM this evening to 6 PM EST Friday for ANZ350. && $$ SYNOPSIS...MD NEAR TERM...MD SHORT TERM...MD LONG TERM...DW AVIATION...BC MARINE...MD/DW HYDROLOGY...MD/DW TIDES/COASTAL FLOODING...

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