Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 170233 AFDOKX Area Forecast Discussion National Weather Service New York NY 933 PM EST Thu Nov 16 2017 .SYNOPSIS... Low pressure across southeastern Canada into northern New England will track east through Friday as high pressures builds in from the west. Strengthening low pressure moving northeast across the lower Great Lakes and Saint Lawrence valleys will push a warm front across on Saturday and a strong cold front late Saturday night into Sunday morning. Strong high pressure builds later Sunday into Tuesday. Another cold front will approach Tuesday night and move across Wednesday morning, followed by high pressure later Wednesday into Thanksgiving Day. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... An upper trough was slowly existing the northeastern coast at 02Z as seen on the upper level water vapor loop. Meanwhile a surface low pressure continues to move through northern New England and southeastern Canada. Cold advection continues through the overnight with a strong pressure gradient force. The cold advection was not too strong, however, mixing will be sufficient to bring down 40 KT NW wind at 850 MB overnight. Gusts will be in the 25-30 kt range. Despite clearing skies and cold advection from a continental polar airmass, winds will remain strong enough to keep temperatures from dropping to below normal levels. Should winds subside earlier than currently forecast, interior zones could see temperatures drop into the low 30s. Inland temperatures were not falling off as quickly as forecast with some strato cu moving into the lower Hudson Valley. There were radar echoes across the lower Hudson Valley however, much of the precipitation was drying in NW flow. There may be a brief sprinkle across the northwestern sections into northeastern New Jersey through 05Z, however, will not mention any probabilities at this time with the isolated and light nature. Low temperatures will drop into the mid 30s to low 40s. A blend of MET/MAV was used. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... As a strengthening low pressure continues tracking off the New England coast, high pressure will briefly build in, keeping a tight pressure gradient through much of the day. Wind gusts of 25-30 kt will slowly subside into the afternoon, with coastal Long Island locations being slower to diminish. Gusty NW winds between 20-25 kt will continue through most of the afternoon. Temperatures will be a few degrees below normal, remaining in the 40s for most of the area, with the lower 50s likely in the NYC metro. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As high pressure slides east Sat morning, S winds will quickly ramp up, with gusts 25-30 mph in the afternoon along the coast, with likelihood of showers as well with a warm frontal approach and passage. Precip chances could wane Sat night as this front lifts to the north, then a potent cold front will approach late Sat night and pass through early Sunday morning accompanied by a band of low-topped heavy convection, with ECMWF still remaining/trending a little slower than other guidance with timing of the frontal passage. Forecast soundings should little in the way of an inversion to limit mixing of stronger winds from aloft, so expect S winds ahead of the front to gust to 40-50 mph, perhaps higher with the convective band. W-NW winds of similar strength also expected after fropa via strong post- frontal pressure rises, deep low level mixing, and strong downward motion in the wake of passage of a strong mid level vort max during the late morning and early afternoon. Winds could remain strong into at least the first half of Sunday night as another mid level vort max passes through during that time. Temps up to and just after cold fropa will be on the mild side, with lower/mid 50s, then steadily drop in the afternoon and at night, with upper 20s/lower 30s by Mon morning, then rising only into the lower/mid 40s daytime Mon. Temps should rebound to near avg on Tue ahead of the next cold front, and there may be a band of WAA showers in advance Tue night into Wed morning, though 12Z guidance has trended offshore with any precip. The 12Z guidance has also trended toward a slower fropa on Wed, but with another colder air mass arriving in time for Thanksgiving Day, with NW winds gusting to 20-25 mph. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Low pressure intensifies as it tracks up the New England Coast tonight. High pressure builds to the west tonight into Friday. W-WNW winds will gust 25-30 KT tonight through Friday morning, before gradually subsiding from W to E Friday afternoon. Occasional peak gusts to 35 KT are possible into early Friday morning. Winds will generally be left of 310 magnetic for the evening push, but likely veering right of 310 magnetic for the morning push. VFR forecast through the TAF period. .OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY... .Friday Night...VFR. Winds quickly diminishing. .Saturday...MVFR or lower conditions possible by the afternoon and becoming likely towards evening. Showers at night S-SW winds G25- 35KT. .Sunday...Conditions improve to VFR with showers ending. NW winds G30-40KT. .Monday...VFR. NW G20-25KT. .Tuesday...VFR. SW G20KT. && .MARINE... Winds increase tonight with an increasing pressure gradient behind a departing low and incoming high builds in. With good mixing of 35 to 40 KT wind aloft should see 35 + gusts across the forecast waters tonight, and did increase the gusts across the non ocean waters. The increased pressure gradient and winds will allow seas to build into Friday. 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. Southerly gales will quickly ramp up on the ocean waters Sat afternoon after a warm frontal passage, and then spread to all waters Sat night in advance of a strong cold front. There is a chance that wind gusts could reach storm force on the ocean just ahead of the front late Sat night or early Sunday morning. W-NW gales should then follow after cold fropa daytime Sunday and possibly into Sunday evening, then gradually ramp down to advy levels later Sunday night into Monday. Ocean seas over 5 ft should linger from Mon night into Tue, with some wind gusts up to 25 kt also possible Tue night ahead of another cold front. && .HYDROLOGY... A band of moderate to locally heavy showers with a strong cold frontal passage late Sat night should cause no more than local nuisance impacts. && .TIDES/COASTAL FLOODING... Storm surge guidance with a strong cold frontal passage may to be on the low side given the strength of southerly winds expected Sat night, and possibly into Sunday morning if the frontal passage continues to trend more slowly. Typically though, S/SW winds are not conducive to building surge. There is a low probability of a surge of 1-2 ft, which if occurred would result in minor coastal flooding with either of the two high tide cycles late Sat into Sunday morning along the south shore back bays of Long Island, and along western Long Island Sound. The most susceptible area to minor coastal impacts with this system may be eastern portions of the Great South Bay and Moriches Bay, due to the SW flow. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Gale Warning until 6 AM EST Friday for ANZ330-335-338-340-345. Gale Warning until noon EST Friday for ANZ353-355. Gale Warning until 6 PM EST Friday for ANZ350. && $$ SYNOPSIS...CB NEAR TERM...CB/19 SHORT TERM...CB LONG TERM...Goodman AVIATION...NV MARINE...CB/Goodman/19 HYDROLOGY...CB/Goodman TIDES/COASTAL FLOODING...

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