Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 200614 AFDOKX Area Forecast Discussion National Weather Service New York NY 214 AM EDT Thu Jul 20 2017 .SYNOPSIS... Hot and humid weather will continue across the Tri-State Area through Thursday. A cold front will pass across the area Thursday night into Friday morning with showers and thunderstorms and possibly bring some brief relief from the heat. This cold front will stall south of the area late Friday and remain around through the weekend before finally moving south as a cold front early next week. High pressure follows through mid week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Dry conditions are anticipated through the remainder of the night. Other than patchy clouds associated with upstream showers, expect a mainly clear sky except across the East End of Long Island and in southeastern CT where enough of an onshore flow of nearly 70-75 degree water could allow for some low stratus to develop. As temps cool toward the dewpoint with light winds, we could also see patchy fog develop on the East End of Long Island, the southeast CT coast and in the interior valleys of southern CT as well as the Lower Hudson Valley and Upper Passaic County and the Ramapo River Valley in North Jersey. A sticky night especially in and near The City with lows in the mid to upper 70s with lows in the upper 60s in the coolest spots well north and west.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/... Any fog that develops should dissipate after daybreak with any stratus gone by mid-morning. The surface trough along the coast will move out. A westerly flow sets up across the area ahead of an approaching cold front. This will result in another hot day with temps in the 90s even at the coast. I went with the warmer end of Guidance in areas from Newark and The City on east as the flow is offshore and usually MOS under perform in this sort of wind regime. A Heat Advisory remains in effect for much of the area and this still looks good. Heat index values will be 95-98 across the most urbanized areas in the afternoon and early evening. The next issue comes tomorrow night as a cold front approaches from the northwest. This is a healthy front with a progged 100 kt+ jet at 250 mb moving across Upstate New York. All operational models agree on some sort of approaching MCS (mesoscale convective system) working across Upstate NY and then weakening or moving toward the Lower Hudson Valley late Thursday evening into early Friday morning. There are variations in the models in how intense and how far south this activity gets but the agreement in the models was enough to boost PoPs. There is some potential if activity is more robust for downpours and gusty winds, especially north of The City in this time frame. Once this moves through somewhat drier air heads in for Friday. It is worth noting the WRF/NAM is much lower with temps on Friday showing highs inly in the mid 80s. The NAM is cooler at 850 mb by 2-4 degrees C, but if activity is slower to exit or brings more clouds we may miss the ability to hit Heat Advisory criteria and thus we held off on extending it since it is not a slam dunk. For now, I lowered temps a hair mainly inland but kept readings in the lower 90s at the coast given the west/northwest offshore flow. The front will stall to the south Friday night but it looks dry and stable enough to remove any showers and thunderstorms from the forecast and keep things dry. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Considerable uncertainty exists for the extended as the polar jet remains at an unusually southward latitude for this time of year. A series of short waves are forecast to develop and move into the Northeast in the developing northwest flow, which is a low confidence pattern on the ultimate track of where any MCSs develop. Adding to the complexity is where the fronts will stall - at the moment forecast to be in the vicinity of the northern NJ, southeast NY and CT area. Depending on the exact location...temperatures, wind direction, instability, etc could vary significantly. Regardless, confidence is highest in a potentially wet and stormy few days as these potent waves progress southeastward, which may at times tap into steeper mid level lapse rates and bring stronger storms. There is potential for high pressure to begin to develop across the area by Tuesday night or into the mid week with cooler and drier conditions. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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A weak trough of low pressure gradually moves across eastern sections of the region overnight before a weak cold front slowly approaches Thursday. Mainly VFR conditions are forecast through Thursday. Will be monitoring for low stratus and patchy fog for KISP, KGON and KSWF overnight, but confidence of this occurring is too low so was left out of TAFS. A general W-SW flow becomes light and variable overnight into early Thursday with W-SW flow re-developing for the late morning/afternoon. Wind speeds 10-15 kt through early evening with some gusts 15 to 20 kt with otherwise 5-10 kt flow. Therefore a few terminals may gust for a few hours for the late afternoon and early evening on Thursday. .OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY... .Thursday Night...Chance of thunderstorms with sub VFR conditions, with improving conditions late. .Friday and Friday Night...VFR. .Saturday...MVFR or lower possible with a chance of showers and thunderstorms. .Sunday-Monday...MVFR or lower possible with a chance of showers and thunderstorms.
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&& .MARINE... Waves were running near 3 feet and should remain in the 2 to 4 ft range through Thursday. Patchy fog and low stratus clouds are possible overnight near the waters around the East End of Long Island and in the waters of New London County that could drop visibility to near 3 statute miles. A cold front will cross the area Thursday night into early Friday morning bringing showers and thunderstorms. The front is expected to stall to our south late Friday. Generally dry conditions are expected through Friday night behind the front with northerly to northwesterly winds under SCA levels. Depending on the exact track of the stalled front, southerly swells may begin to increase through the weekend into early next week, with a low probability for SCA conditions on the ocean by Monday. && .HYDROLOGY... There is a the potential for heavy rainfall producing thunderstorms across the area late Thursday evening into early Friday morning as a complex of showers and thunderstorms approaches from the northwest. This could result in pockets of heavier showers and thunderstorms that could produce rainfall totals in excess of one inch per hour. The main threat would be poor drainage flooding in highly urbanized and other poor drainage areas. There is a low chance for flooding during the Saturday Night into Monday Night period as a slow moving frontal system interacting with a moist and unstable airmass brings a threat for periods of heavy showers and thunderstorms. && .CLIMATE... Today marked the 8th day of 2017 the temperature has reached at least 90 degrees at Central Park. So far we have had two heat waves (at least 3 consecutive days of 90 degrees or greater) in 2017 at Central Park - from May 17th through May 19th and from June 11th through the 13th. The highest temp of 2017 at The Park has been 94 on June 13th. Highest temps of 2017 for the other main climate stations in the area: LaGuardia Airport: 101 on 6/13 JFK Airport: 94 on 6/13 Islip: 93 on 6/13 Newark: 99 on 6/13 Bridgeport: 94 on 6/13 && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Heat Advisory until 6 PM EDT this evening for NYZ069>075- 176>179. NJ...Heat Advisory until 6 PM EDT this evening for NJZ004-006- 103>108. MARINE...None.
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&& $$ SYNOPSIS...MD/CS NEAR TERM...IRD/PW/CS SHORT TERM...CS LONG TERM...MD AVIATION...IRD/JE MARINE...MD/PW/CS HYDROLOGY...MD/CS CLIMATE...

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