Area Forecast Discussion
Issued by NWS Upton, NY

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534 FXUS61 KOKX 250537 AFDOKX Area Forecast Discussion National Weather Service New York NY 137 AM EDT Sat Mar 25 2017 .SYNOPSIS... A cold front over upstate New York and central New England will drift south overnight and through the Tri-State Region on Saturday. An unsettled weather pattern continues Sunday into the middle of next week. Cold front to our south returns to the region Sunday night into Monday and moves offshore Monday night. Another frontal system approaches on Tuesday and moves across Tuesday night into Wednesday. High pressure returns Thursday ahead of the next front on Friday. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Minor adjustments made to temperature, dew point and winds tonight. A few locations have decoupled faster than previously forecast, allowing temperatures to fall quickly, though these sites have been fluctuating between mid 30s and lower 40s as the wind briefly picks up again at times. Mid and high level clouds will remain through the overnight with a few breaks from time to time. Temperatures vary drastically in the diminishing SW flow, which is common in the early spring due to the cold nearshore waters. Parts of the NYC metro are in the mid and upper 50s, while in the suburbs temperatures range from the mid 30s to the mid 40s. Temperatures will fall slightly overnight and then level off. Lows will average 10 to 15 degrees above normal due to the SW flow and cloud cover. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... A cold front over southern Ontario will track south through the area by late Saturday morning into the afternoon. The timing is pretty consistent between the NAM and GFS, so the NAM was used in the grids. This translates into falling temperatures across the northern half of the forecast area by afternoon, with the fall in temperatures later in the day across New Jersey zones. Water vapor indicates a moisture stream from the subtropical Pacific into the Southeastern United States. This will allow for some deeper moisture to penetrate into the region during the day and through the night. The upper jet will be passing from southern Canada into Northern New England at this time, producing some broad lift. With these factors combining, light rain has been forecast for the area mainly Saturday afternoon and Saturday night. Easterly component low level flow could allow for some fog or drizzle development particularly overnight. Patchy fog has been maintained in the forecast along with the light rain as a result. The downscaled NAM was used for temperatures Saturday to account for the cold frontal passage. A blend of guidance was used Saturday night. There is a low chance that temperatures approach freezing late Saturday night which could result in some pockets of interior icing. The probability is low at this time, so it has not been included in this forecast. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Unsettled, progressive weather pattern will persist from Sunday through the upcoming week. Deterministic models and ensembles are in general agreement with the synoptic scale, with differences arising in the timing and amplitude of several shortwaves to move across. Backdoor front will be well to the south on Sunday with high pressure building south of out of Quebec. Warm air overrunning the stable, cool layer at the surface will keep low clouds throughout the day and the chance for light rain or drizzle. Upper level ridging will be in place, so there is not much support for widespread precipitation. Temperatures will be held down in the lower and middle 40s due to onshore flow and cloudy conditions. Cutoff low over the central states on Sunday will open and lift towards the Great Lakes Sunday night and then continue to dampen out as it moves towards the region on Monday. Upper ridge axis gradually moves offshore allowing for better lift for more widespread rainfall. Pops increase to likely for much of the area late Sunday night into Monday morning with categorical across the north closer to the shortwave energy and best lift. Shortwave axis quickly moves east Monday afternoon and evening, which will take the lingering front to the south and east. Brief ridging moves across Monday night with another shortwave on its heels for Tuesday. This is where deterministic runs and ensembles begin to diverge further as the latest 12z ECMWF flattens this next shortwave out as it passes whereas the 12z GFS and the GEFS are more amplified, bringing a weak low pressure across the region. Have capped pops off in the chance range due to the uncertainty on the amplitude of this wave. In either case, mostly cloudy to overcast skies continue. An amplifying shortwave across southeast Canada sends a shortwave across New England on Wednesday, but frontal boundary should be well offshore at this time, so improving conditions are expected. High pressure than follows on Thursday before another frontal system approaches for Friday. Near seasonable temperatures are forecast on Monday with temperatures returning to above normal levels Tuesday into Wednesday. Seasonable temperatures are currently expected for the end of the week. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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A cold front approaches from the north overnight and passes south of the terminals this morning. High pressure then builds down from the north into Saturday evening. VFR until around 17z, then MVFR conditions develop in light rain and fog. IFR conditions likely late this afternoon, with patchy LIFR conditions possible. S-SW winds less than 10 kt become light and variable toward 12Z as the front nears, then winds shift to NE with the cold front passage, 10 KT or less. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .Saturday night-Monday...IFR likely with LIFR or lower possible. Periods of rain, drizzle and fog. .Monday night-Tuesday night...MVFR or lower possible. .Wednesday...becoming VFR. NW winds G15-20kt possible in the afternoon.
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&& .MARINE... Small Craft Advisory conditions will continue on the ocean through Saturday despite the diminishing winds. It is possible conditions remain at Small Craft Advisory levels on the ocean Saturday night. Marginal SCA winds are forecast on Sunday on the ocean, but seas will likely be around 5 ft through the evening. From Sunday night through Monday night, sub-sca conditions are forecast with an overall weak pressure gradient. Seas may build to around 5 ft on Tuesday as a cold front passes through. Otherwise winds and seas should remain below SCA levels into Wednesday. && .HYDROLOGY... Less than a quarter inch of rain is expected through Saturday night. Unsettled conditions Sunday through the middle of next week will bring periods of rain. However, no hydrologic concerns are anticipated at this time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ350- 353-355. && $$ SYNOPSIS...12/DS NEAR TERM...12/MD/DW SHORT TERM...12 LONG TERM...DS AVIATION...MET MARINE...12/DS HYDROLOGY...12/DS is the U.S. government's official web portal to all federal, state and local government web resources and services.