Area Forecast Discussion
Issued by NWS Upton, NY

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395 FXUS61 KOKX 171648 AFDOKX Area Forecast Discussion National Weather Service New York NY 1148 AM EST Tue Jan 17 2017 .SYNOPSIS... Weak low pressure and a warm front pass nearby tonight into Wednesday morning with high pressure slowly building in behind it through Thursday night. The high weakens on Friday followed by a weak wave of low pressure passing to the south Friday night. High pressure returns this weekend before the next low pressure and associated frontal system impacts the area early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Rain will continue to overspread the rest of the forecast area this afternoon with increasing lift arriving from the west. As noted in the earlier update, some models indicate some cooling of the elevated warm layer over parts of CT, as well as some cooling below this layer. This area is closer to relatively drier air being supplied by high pressure to the northeast. Have therefore added a chance of sleet along with the rain this afternoon for a good portion of the CT zones. Surface temperatures should remain no lower than the mid 30s for the rest of the day, so no freezing rain is anticipated. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Rain continues tonight as a triple-point low and warm front approach. The warm front may lift through some of the southern sections tonight, but even north of the front, expecting surface temperatures to be above freezing. There is however some uncertainty with the amount of dynamic cooling aloft over CT in response to better lift early in the evening, and there could be some sleet mixed in with the rain here early in the evening. With a moisture-laden boundary layer, also put in patchy fog across the CWA for tonight into early Wednesday. For Wednesday, took a blend of MAV/MET/ECS for temperatures. Light rain continues behind the low as 500mb vort max passes south of the region with associated PVA. This will become more of a shower mode by afternoon, mainly across eastern sections. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Active jet stream pattern will continue into early next week. The latest global models and ensemble means are in overall good agreement with just some timing differences. Above normal temperatures will be the theme with NYC likely not falling below freezing through at least early next week. Offshore low will gradually move further east over the Atlantic Wednesday night into Thursday. High pressure settles over the region Thursday into Friday as ridging builds aloft. High temperatures both days will be in the middle and upper 40s for most locations and near 50 degrees in the NYC and NE NJ metro. Active southern branch of the jet will bring the approach of the next system on Friday. And upper low over the Plains will open up on Friday and energy will get driven under building ridging over the eastern States. Models and ensembles have come into better agreement with this system weakening as it approaches Friday night. The weak surface reflection should largely stay to the south of the Tri- State, with potential for some precipitation to graze the region. Confidence is low in the coverage of precipitation since the system is weakening as it moves nearby and lift and moisture are limited. 850 mb 0C line on the GFS, GEFS mean, ECMWF, and ECMWF EPS mean lies across northern New England so snow is not a concern. Inland surface temperatures would be the only concern if precipitation were to make it that far north, and at this time thinking it should be above freezing everywhere for just plain rain. Anomalous ridging aloft continues this weekend and surface high pressure will build down from SE Canada. The active southern branch of the jet will continue as the next system organizes across the central States on Sunday. Global models and ensembles continue to show a strong cut-off low lifting towards the Ohio Valley Sunday night into Monday. Its associated frontal system will gradually approach early next week. Confidence in specific details is low at this point since this is about a week out, but the signals are there for a significant rainfall event. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... A warm front slowly approaches from the southwest through early this evening as low pressure moves through the eastern Great Lakes region. Another low will develop on a triple point across central New Jersey this evening and track south of Long Island tonight. MVFR conditions have already developed for the city terminals. VFR for all other locations until approximately 16z-17z. Conditions will then lower to IFR late this afternoon into early this evening. IFR conditions then remain through 12z Wednesday with light rain and fog. Winds will be SW to W less than 10 KT to light and variable early then becoming SE this afternoon and then e late this afternoon into this evening. Winds will mainly be 5 to 8 KT. There is uncertainty to the timing and direction of the winds and will be dependent on the movement of the warm front and timing and placement of the developing low this evening. ...NY Metro Enhanced Aviation Weather Support... Detailed information...including hourly TAF wind component fcsts can be found at: http:/ KJFK TAF Comments: MVFR ceilings could be more occasional this morning. Winds may become SE before 17Z. KLGA TAF Comments: MVFR ceilings could be more occasional this morning. Winds may become SE before 17Z. KEWR TAF Comments: MVFR ceilings could be more occasional this morning. Winds may become E before 17z. The afternoon KEWR haze potential forecast is green...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: MVFR ceilings could be more occasional this morning. Winds may become more SE before 17z. KHPN TAF Comments: Amendments possible as MVFR ceilings could develop before 17Z and visibilities may remain MVFR. Winds may also become SE before 17Z. KISP TAF Comments: Uncertainty with the timing of MVFR ceilings this afternoon and may be sooner than 17Z, and developing IFR conditions may be before 21Z. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY... .Wednesday...IFR early, improving to MVFR, in rain and fog. Rain ending in the afternoon with visibilities improving, ceilings MVFR. .Wednesday night...Becoming VFR. .Thursday-Friday...VFR. .Friday night-Saturday...Chance of MVFR or lower with light rain developing. && .MARINE... Conditions remain mostly below SCA on the waters with the pressure gradient remaining weak enough today through early Wednesday. The only exception would behind a low Wednesday afternoon, in which ocean waters east of Moriches Inlet could potentially reach SCA criteria. Winds on the ocean will gradually diminish Wednesday night, but some SCA gusts are still possible east of Moriches inlet. Easterly swells from offshore low could bring ocean seas to SCA levels Wednesday night into Thursday. Winds and seas on all waters are forecast to be below SCA levels Thursday night into the weekend. && .HYDROLOGY... No hydrologic impacts are anticipated with around a half inch of precipitation today through Wednesday morning. Potential exists for a significant precipitation event early next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JM/DS NEAR TERM...JC/JM SHORT TERM...JC/JM LONG TERM...DS AVIATION...CB/MET MARINE...JM/DS HYDROLOGY...JM/DS is the U.S. government's official web portal to all federal, state and local government web resources and services.