Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 270143 AFDOKX Area Forecast Discussion National Weather Service New York NY 943 PM EDT Wed Jul 26 2017 .SYNOPSIS... High pressure moves off the mid-Atlantic coast through Thursday. Low pressure forms late Friday over Virginia and passes south of Montauk Saturday Morning which likely brings rain to the region. Canadian high pressure builds from the north late Saturday into early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Only minor adjustments needed to reflect current temperature and dew point trends. Mid and high level clouds will continue to increase from the west overnight ahead of an approaching short wave. Lows around 65 in the NY Metro - near 60 elsewhere (around 5 degrees below climo). Could have some valley fog towards morning over the interior, but with the increase in high level moisture, decided to not including it. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Weak frontal boundary sags down and over the region Thursday evening. Have continued with low chance TSTMs with SPC lowering the region to marginal after collaboration with Local NWS Offices. Ensemble of NWP suggest about 1000 J/kg of MUCAPE and LI`s of -1 to -4 C of LI. Shear is only around 30 KT and most show subsidence in the 850-700 hPa layer. Thus the lowering of POPs and severe potential. POPs increase overnight as front sags southeast. Instability then has a synoptic support from the frontal passage and most NWP supports scattered convection. Upper 70s to around 80 based on consensus of MOS for highs and around 70 for lows Thursday night using warmer NAM MOS based on clouds and scatted precipitation. There will be a moderate risk of rip currents at area beaches. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... The long term period starts off with unsettled weather Friday, Friday night and the first half of Saturday as low pressure passes south of the forecast area. At this time, looks like showers and thunderstorms will occur on Friday. There is the potential that some rain could be heavy at times. the showers should transition to more of a stratiform rain event Friday night into Saturday morning, once again with some rain potentially being heavy, especially during the first half of Friday night. Winds will increase, especially across Long Island and southern CT, as the low intensifies Friday night and Saturday. Gusts into the 30 mph range is possibly, and can not rule out a few gusts to 40 mph. As of right now, average rainfall amounts for this event are expected to range from 0.50-1.00 inches across the Lower Hudson Valley and southern CT and from 1.00-1.70 across the Northeast NJ, NYC and Long Island. Locally higher amounts will be possible. These amounts are likely to change, as we fine tune the exact track of the low. The low moves east on Saturday. The rain comes to an end Saturday morning as high pressure builds in from the north. High pressure remains over the region through the first half of next week, providing dry and seasonable conditions. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... High pressure slides offshore through tonight. A weakening cold front approaches from the northwest on Thursday. Mainly VFR through the TAF period. There is a low chance of MVFR conditions late tonight into Thursday morning, especially across the Lower Hudson Valley. S-SE winds at 5-10 kt will become light and variable throughout tonight. Winds then become S-SW at under 10 kt by mid-late Thursday morning. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Timing of onset of light and variable winds could be off +/- 1-2 hours. KLGA TAF Comments: Timing of onset of light and variable winds could be off +/- 1-2 hours. KEWR TAF Comments: Timing of onset of light and variable winds could be off +/- 1-2 hours. KTEB TAF Comments: Timing of onset of light and variable winds could be off +/- 1-2 hours. KHPN TAF Comments: Timing of onset of light and variable winds could be off +/- 1-2 hours. KISP TAF Comments: Timing of onset of light and variable winds could be off +/- 1-2 hours. .OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY... .Thursday afternoon-Thursday night...MVFR possible, with a chance of showers and possibly a tstm. .Friday-Saturday morning...MVFR or lower possible, with showers and possibly a tstm. NE winds G20-30kt late Friday night into Saturday, mainly at the coastal terminals. .Saturday afternoon-Monday...VFR. && .MARINE... Tranquil into Friday. Winds and seas gradually build to advisory levels Friday night and into Saturday night as low pressure passes over the area waters. Expect a strengthening N-NE flow, with the potential for gales Friday night into Saturday. Winds will subside below advisory level on Sunday, however it may not take until Monday for seas to fall back below 5 ft as high pressure builds in. && .HYDROLOGY... Heavy rainfall is possible Friday afternoon into the night across the NY Metro and Long Island. Urban and poor drainage flooding is possible. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...Tongue NEAR TERM...MD/Tongue SHORT TERM...MD/Tongue LONG TERM...BC AVIATION...Maloit/DW MARINE...BC/Tongue HYDROLOGY...BC is the U.S. government's official web portal to all federal, state and local government web resources and services.