Area Forecast Discussion
Issued by NWS Upton, NY

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051 FXUS61 KOKX 220234 AFDOKX Area Forecast Discussion National Weather Service New York NY 1034 PM EDT Thu Jun 21 2018 .SYNOPSIS... A weak cold front will dissipate over the region this evening with high pressure building north of the area. The high lifts to the north and east on Friday as a frontal system approaches from the southwest. A warm front passes late Saturday into Saturday night and will be followed by cold fronts on Sunday and then on Monday. High pressure returns for Tuesday and Wednesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A cold front dissipates over the area tonight. Weak cold advection and the upper trough passing through the northeast will allow high pressure to build to the north of the area tonight. This will allow a light S/SE flow gradually to back to the NE. Stratus/patchy fog deck along E LI/SE CT will continue to drift westward across much of E LI/SE CT through midnight in easterly flow ahead of weak cold front. Expectation is this should begin to get suppressed offshore late tonight into Fri morning as flow becomes ne and drier air advects south as cold front dissipates. Fog could be locally dense along the immediate shoreline at times. Overnight lows will be nearly seasonable ranging from the upper 50s across the interior, to the mid and upper 60s across the NYC metro. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Upper trough lifts out across the Northeast on Friday, while heights build ahead of an upper low lifting northeast into the Ohio Valley. This will send a warm front northward along the Mid Atlantic coast as high pressure centered over Northern New England moves out into the western Atlantic. Overrunning mid and upper level clouds will increase through the day with a strengthening easterly flow between the departing high and associated warm front to the south. Gusts up to 20 mph will be possible, especially near the coast. Additionally, a frontal wave along the warm front passes off to the south and east of the area Friday night. This in turn may strengthen the low-level ridging across the area enough to maintain dry air. There have been multiple scenarios playing out in the guidance the last several days with the potential for rainfall Friday night, but latest indications are that the rain will arrive late and should be mainly light. Also, the upper low is weakening and opening up as it runs into the ridge over the western Atlantic. Should the frontal wave be a little father west than forecast, this would pose the potential for steadier rain across eastern Long Island. There is low confidence in this scenario. More or less this will be an easterly flow event with some light rain and cooler temperatures. Highs on Friday will be in the 70s, with lows in the upper 50s to lower 60s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Upper low will continue to open up and flatten through the day on Saturday as it moves across the Great Lakes region. The flattening shortwave will continue to traverse across New England on Sunday. The main upper flow over the Northeast this weekend into next week Closed upper low opens as it traverses across the Great Lakes region and into New England this weekend. Another shortwave in a broader cyclonic flow regime aloft will pass on Monday. Upper ridging returns for Tuesday into Wednesday with the next possible shortwave for next Thursday. There has not been too much change in the overall thinking for sensible weather. There are still differences in the model guidance with the depth of surface ridging and the exact direction of the surface winds. The NAM on Saturday has northeast flow at the surface and the GFS is more easterly. The NAM depicts a weak surface wave moving off the south and east on Saturday and the GFS has less of a reflection of a surface wave. This will make a big difference in low level moisture and the potential advection of drier dew points from the northeast into the region. Confidence in higher PoPs has lowered and therefore have lowered them until the evening hours. Saturday may just remain overcast with some light rain at times, with better forcing and moisture arriving in the evening as the warm front and shortwave axis nears the region. The shortwave axis lifts up into northern New England after 06z, which will end any showers. Instability is weak Saturday night, so will just mention slight chance of thunder. Westerly flow aloft will dry the middle and upper levels out enough for a return to partly cloudy condition on Sunday. A trailing cold front approaches late in the day along with some trailing shortwave energy. A chance for showers and thunderstorms is supported by these systems in the afternoon and evening. A much sharper upper level trough approaches late Sunday night into Monday with a secondary cold front ahead of it. The GFS is much stronger with the embedded energy within the trough which agrees with the CMC. The ECMWF is much broader and faster with the trough. Low PoPs will persist into Monday for a continued chance of showers. High pressure returns for Tuesday into Wednesday with the next cold front approaching on Thursday. Temperatures should then average near normal for next week. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/...
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High pressure builds in from the north overnight and moves off the northeast coast Friday. Meanwhile another frontal boundary will remain well to the south, through the mid Atlantic region and off the coast. A wave of low pressure will approach from the west late in the forecast period. Stratus and fog, with IFR to LIFR conditions have been developing across coastal CT and eastern Long Island. With a light northeast flow overnight the stratus will likely move into the NYC metro terminals before sunrise Friday, with IFR conditions for several hours. Conditions improve to VFR 12Z to 15Z. There is uncertainty as to how long the stratus and fog will remain overnight as high pressure will be building in from the north with drier air moving into the region. Winds will be light, under 10 KT from the NE to E overnight. Winds then increase from the east to southeast, 10-15, Friday morning, and then remain into the afternoon. Occasional gusts to near 20 KT are possible during Friday afternoon. .OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY... .Friday night...VFR early, then becoming MVFR with a chance of light rain. .Saturday...Sub-VFR. Showers likely, possibly a thunderstorm during the evening and nighttime hours. .Sunday...Chance of sub-VFR conditions in showers and thunderstorms. .Monday...Chance of showers early, becoming VFR. .Tuesday...VFR.
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&& .MARINE... Dense fog advisory continues for ocean and eastern nearshore waters tonight as stratus/fog deck advects over the waters. This stratus deck should eventually get suppressed south mainly over the ocean late tonight into Friday morning. A strengthening easterly flow late tonight into Friday will result in building seas and the potential for marginal SCA conditions on the ocean waters Friday into Friday night. Preference at this times was to hold off on any issuance. Winds will likely stay below 25 kt Saturday through early next week. Winds on the ocean may approach 20 kt at times this weekend, but will otherwise stay below 25 kt through early next week. Ocean seas may build to 5 ft this weekend as a warm front moves north and SW flow increases. Ocean seas may also approach 5 ft on Monday with seas otherwise remaining below SCA levels on Tuesday. && .HYDROLOGY... Some light rain is possible Friday night into Saturday. There could be a few locally heavy downpours on Saturday night and Sunday, but no hydrologic impacts are anticipated this weekend. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Dense Fog Advisory until 8 AM EDT Friday for ANZ330-340-345- 350-353-355. && $$ SYNOPSIS...DS/DW NEAR TERM...NV/DW SHORT TERM...DW LONG TERM...DS AVIATION...19 MARINE...DS/NV/DW HYDROLOGY...DS/DW EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.