Area Forecast Discussion
Issued by NWS Upton, NY

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950 FXUS61 KOKX 200251 AFDOKX Area Forecast Discussion National Weather Service New York NY 1051 PM EDT Thu Oct 19 2017 .SYNOPSIS... A weak cold frontal passage will occur late tonight. High pressure will dominate from Friday through Monday, moving offshore Sunday through Monday. A slow moving frontal system will then approach the area Tuesday into Tuesday night with a cold frontal passage by early Wednesday. The front is slow to depart farther away with a wave of low pressure developing along it and approaching the area mid into late next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Analysis of surface theta-e reveals the cold front is beginning to move across western upstate NY and NW PA. All high res models forecast the front to quickly move to the south and east overnight and move offshore around sunrise. The main upper level trough will track into northern Quebec tonight so there will not be any significant change in airmass other than a minor drop in dew points. Just a few-sct high thin cirrus tonight behind the upper trough Winds will gradually shift from the SW to the NW once the front moves across. Lows tonight fall into the 40s and 50s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... High pressure builds back into the region behind the cold front. Winds will remain from the Northwest and gust into the upper teens and lower 20s. There is a chance that gusts could be slightly higher than forecast based on the amount of mixing that occurs. Conditions remain dry. Winds gradually diminish overnight, becoming light and variable across the interior. Max temperatures will climb into the upper 60s and lower 70s on Friday, with lows Friday night falling into the 40s and 50s. A MAV/MET/ECS blend was used for the short term temperatures. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Warming trend for the weekend through Monday as the jet stream remains north of the region with upper level ridging. At this surface, the dominant feature will be high pressure eventually moving offshore and the resulting S-SW flow. Mainly clear sky conditions are expected to continue this weekend. Clouds increase Monday into Monday night ahead of the next frontal system. The next chance of rain showers arrives late Monday night into Tuesday, when a deep upper level trough approaches from the west. The trough further deepens Tuesday along the Eastern Seaboard with increasing meridional flow. This will give plentiful moisture to a developing frontal system at the surface. The frontal system will be approaching the region Tuesday into Tuesday night with the region being in the warm sector to the east of the low with strengthening southerly flow, thereby increasing warm air advection. Precipitable water increases to near 1.5 inches from the moisture advection. This is much above normal for this time of year. According to OKX sounding climatology, it would be above the 90th percentile. Some moderate to heavy rainfall will be possible. The cold front moves across Wednesday morning, with a substantial decrease in precipitable water thereafter to less than 1 inch. The front slows down and is slow to depart away from the region. The numerical forecast models show weak low pressure development along it and the low approaching the region mid into late next week, with rain shower chances continuing. Temperatures are expected to be well above normal this weekend through Tuesday with a gradual decline thereafter. Highs this weekend through Tuesday are forecast to be well into the 70s with lows trending to be well into the 50s and near 60 for some locations along the coast and NYC. The highs are forecast to be more in the 60s for next Wednesday and next Thursday. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... A weak cold front approaches from the Lower Great Lakes tonight and passes through prior to daybreak. High pressure then builds in from the west through Friday night. VFR with only some cirrus through the period. SW winds less than 10 kts, gradually veer to the NW through the overnight. Winds will be right around 310 true during Friday, around 10 kt with frequent gusts up to 20 kt. .OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY... .Friday night-Monday...VFR. .Tuesday...MVFR possible in showers. S wind G20-25 kt. LLWS possible. && .MARINE... Winds east of Fire Island Inlet are close to marginal small craft levels and this should continue overnight. Seas are also running right around 5 ft. These conditions will fall below SCA levels early Friday morning behind a cold front passage. Elsewhere, winds and seas will generally be below small craft advisory levels through Friday night. There could be some nearshore gusts approaching 25 kt Friday afternoon on a relatively strong NW flow. With high pressure dominating, expecting overall a weak enough pressure gradient to keep conditions below SCA this weekend through Monday night on the waters. SCA will be probable for Tuesday ahead of a cold front as southerly winds strengthen the southerly fetch. Both wind gusts and seas are forecast to meet SCA thresholds for the ocean for Tuesday and perhaps all waters Tuesday night. && .FIRE WEATHER... A special weather statement has been issued for the entire region on Friday due to enhanced fire danger. RH values should drop to 30 to 35 percent while winds gust 20 to 25 mph, especially late morning into the afternoon. && .HYDROLOGY... No hydrologic problems are expected through Monday night. For Tuesday through early Wednesday, heavy rain will be possible at times with potential areas of 1 inch or higher. There is much uncertainty with exact rainfall amounts. Urban and poor drainage flooding will be possible. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ350-353. && $$ SYNOPSIS...BC/JM NEAR TERM...DS SHORT TERM...BC LONG TERM...JM AVIATION...DW MARINE...BC/JM FIRE WEATHER...BC HYDROLOGY...JM

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