Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211457 AFDOKX Area Forecast Discussion National Weather Service New York NY 957 AM EST Wed Feb 21 2018 .SYNOPSIS... High pressure over the western Atlantic remains in control today as a slow moving cold front approaches from the west. The cold front moves through tonight, stalling to the south on Thursday. A series of lows and frontal boundaries will impact the area late in the week and through the weekend. High pressure builds early next week. && .NEAR TERM /THROUGH TONIGHT/...
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Forecast generally on track, however temperature forecast into this afternoon will be tricky based on how fast fog and clouds lift. Updated temperatures to reflect latest obs and trends. Extended the Dense Fog Advisory for Suffolk County and coastal Connecticut until 17Z since observations still indicating widespread 1/4 mile visibilities in these locations. Have allowed the advisory to expire for Nassau, Queens, Brooklyn Bronx, Westchester and northern Fairfield, northern New Haven, northern Middlesex and northern New London counties. The atmosphere above 2 kft is very dry today, so suspect heating and mixing will be sufficient to allow the fog/stratus to burn off/lift a few hours after sunrise. A similar situation occurred on Tuesday with much of the region seeing at least partly sunny skies by late morning/early afternoon. Followed the same overall idea, but with a slightly quicker improvement than what was seen Tuesday. The only exception is across eastern Long Island and southeastern CT where at least patchy fog and/or stratus could linger into the afternoon. The main weather story for today will be the unseasonably warm temperatures aided by an anomalously strong western Atlantic ridge. The 00z OKX RAOB had an observed 500 mb height of 5880m, which well above the max observed values for this time of year per SPC Sounding Climatology webpage. In fact, it is higher than any observed value for December through March. Suspect a similar 500 mb height will be observed this morning on our 12z RAOB, leading to record high temperatures. Better mixing compared to Tuesday will allow temperatures to soar well into the upper 60s and lower 70s away from the immediate coast where readings will be held down in the upper 50s and lower 60s from colder ocean influence. These temperatures are more typical of normal highs in early May. See climate section below for record highs for February 21. A slow moving cold front moves into the region this evening with a shower possible across the NW interior.
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&& .SHORT TERM /THURSDAY/... Western Atlantic ridge breaks just enough tonight to allow the cold front to sink south of the region. Lift with the front is weak and have limited PoPs to low chance for the first part of the night. Temperatures will begin a decline as an approx. 1043mb surface high traverses across southeast Canada and begins to build across northern New England. Cold advection will take place tonight with temperatures falling into the upper 30s inland and lower 40s closer to the coast. The cold front stalls across the southern Middle Atlantic on Thursday. The anomalous western Atlantic ridge will still be dominating the weather pattern across the eastern US, but its height field over the northeast is progged to be a bit more suppressed. Weakening shortwave energy will ride along the periphery of the ridge with a weak low pressure developing on the stalled front to our south. Warmer air between 850 and 750 mb will overrun colder air below advecting south from the strong high to the north. This sets up a period of precipitation from late Thursday morning into Thursday evening. Much of the area will see a chilly rain, but there could be some sleet mixing in across the interior in the afternoon where the depth of the colder air is a bit deeper. Will need to watch surface temperatures across the interior as there are some hints that they could come close to freezing in the afternoon. Did not mention freezing rain in the forecast at this time, but it may have to be introduced in subsequent forecasts if colder temperatures look more likely. Temperatures on Thursday will be 20-30 degrees colder than on Wednesday. Daytime highs in the lower to middle 40s will likely occur in the morning, with temperatures falling into the 30s in the afternoon. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Quite an active pattern is expected through the weekend. Deep SW flow prevails initially with ridge located over the southeast, and trough over the western United States. Sfc frontal boundary weakens as it sags south of the area Thursday night, and lingering light precip temporarily tapers off as high pressure builds to the north. An area of low pressure passes to the north, dragging a warm front, occluded front to the north, through Friday. A cold front quickly follows Friday night. Once again, the front does not make much progress to the south, and the next low pressure center approaches Saturday and Sunday. This is out ahead of downstream trough that ejects out of the west and makes eastward progress across the mid section of the country. The low tracks well to the north, with a warm front passing, followed by a cold front Sunday and Sunday night. High pressure builds Monday and Tuesday. Even though temperatures will be no where near the record readings of the past couple of days, above normal temperatures are anticipated though the period. Highest readings expected this weekend ahead of downstream system when WAA ensues. As for sensible weather, lingering light precip Thursday night will be mainly in the form of rain, but a wintry mix of rain and sleet, or freezing rain and sleet, is expected across the interior. This is true for Friday morning as well if precip moves back in early enough, but all locations should see plain rain when the bulk of the precip arrives ahead of the warm front as temps warm. When precipitation does occur this weekend, it will be in the form of rain. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... High pressure today gives way to a cold front tonight. Fog and Stratus continue through 14z-15Z, then we should start to see some improving conditions. VFR is expected by afternoon. S winds bcmg SW this morning, around 10 kt. G15-20KT possible this afternoon for KLGA, KEWR, KTEB, KHPN, KSWF. Winds shift to the NW between 01z and 03z with gusts 15 to 20 kt for NYC/NJ terminals. 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: Timing of improving flight categories may be off by 1-2 hours. The afternoon KJFK haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KLGA TAF Comments: IFR might no longer occur and MVFR conds otherwise prevail thru 15z. Timing of improving flight categories may be off by 1-2 hours. The afternoon KLGA haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KEWR TAF Comments: IFR might not occur and MVFR conds otherwise prevail thru 15z. Timing of improving flight categories may be off by 1-2 hours. The afternoon KEWR haze potential forecast is YELLOW...which implies slant range visibility 4-6SM outside of cloud. KTEB TAF Comments: IFR might not occur and MVFR conds otherwise prevail thru 15z. Timing of improving flight categories may be off by 1-2 hours. KHPN TAF Comments: Timing of improving flight categories may be off by 1-2 hours. KISP TAF Comments: TEMPO or prevailing VLIFR possible thru 14z or 15z. Timing of improving flight categories may be off by 1-2 hours. .OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY... .Thu...MVFR/IFR in rain likely. Rain/sleet mix for KSWF in the afternoon and chc sleet/freezing rain at night. N/NE wind G15-20 KT possible. .Fri...MVFR/IFR in rain. chc morning sleet/freezing rain at KSWF. .Sat...CHC MVFR in shra. .Sun...MVFR/IFR in rain. S G20 KT. && .MARINE...
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Dense fog advisory has been extended for the central and eastern ocean and the sound until 17Z due to visibilities near 3/4 miles. The advisory has been cancelled for the harbor and western ocean zones since visibilities have improved. With a persistent southwest flow ocean seas east of Fire Island Inlet remain 5 feet or a little higher through tonight. Marginal SCA gusts are also possible on the ocean this afternoon and evening ahead of a cold front. The cold front moves to the south tonight with seas gradually subsiding below 5 ft into Thursday morning. Sub-SCA conditions are likely Thursday morning with ocean seas building above 5 ft and marginal SCA gusts on the ocean in the afternoon. Gusty east/northeast winds Thursday night will lighten as the winds shift to the east/southeast late Thursday night and Friday. A warm front passes as low pressure tracks well to the north, followed by a cold front Friday into Saturday. The front settles nearby, and moves back to the north as a warm front Sunday. Another area of low pressure tracks well to the north late this weekend. Winds pick up during this time, and seas build as well.
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&& .HYDROLOGY... Episodes of light to moderate rainfall are possible Thursday into the weekend. One to two inches of total rainfall is a possibility, but the rainfall accumulations will occur over a long duration. As such, no hydrologic impacts are anticipated at this time. && .CLIMATE... Temperatures may approach or break record highs in a few spots Tuesday and Wednesday. Record Highs for Wednesday February 21, 2018 Location........Record/Year Newark..............69/1953 Bridgeport..........59/2002 Central Park........68/1930 LaGuardia...........68/1953 JFK.................63/2002 Islip...............63/2002 Record High Minimum Temperatures for Wednesday February 21, 2018 Location........Record/Year Newark..............49/2002 Bridgeport..........44/2002 Central Park........50/2002 LaGuardia...........47/2002 JFK.................47/1981 Islip...............45/1996 && .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Dense Fog Advisory until noon EST today for CTZ009>012. NY...Dense Fog Advisory until noon EST today for NYZ078>081. NJ...None. MARINE...Dense Fog Advisory until noon EST today for ANZ330-335-340-345- 350-353. Small Craft Advisory until 6 AM EST Thursday for ANZ350-353.
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&& $$ SYNOPSIS...DS/PW NEAR TERM...CB/DS/PW SHORT TERM...DS LONG TERM...PW AVIATION...BC/JC MARINE...DS/PW HYDROLOGY...DS/PW CLIMATE... EQUIPMENT...

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