Area Forecast Discussion
Issued by NWS Upton, NY

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291 FXUS61 KOKX 130254 AFDOKX Area Forecast Discussion National Weather Service New York NY 1054 PM EDT Mon Apr 12 2021 .SYNOPSIS... Low pressure weakens as it tracks along a stalled boundary to our south and west tonight. High pressure then builds over the region Tuesday and then offshore Tuesday night into Wednesday. Ridge axis shifts to the east Wednesday into Thursday followed by a trough and coastal low pressure system. System impacts southern New York through the end of the work week. Another low pressure system could impact our area early next week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Convergence running NW to SE has been evident for the past few hours on radar as well as surface wind analysis. This trough of convergence is expected to shift S and W over the next few hours, bringing and end to rain by daybreak across the entire forecast area. SE CT and eastern LI should be dry for the rest of the night as high pressure ridges in and dries things out. PoPs have been changed with this update to reflect this thinking and the latest radar trends. Additional rainfall amounts should be light with generally up to around a tenth of an inch. Lows temperatures tonight will be near normal in the lower to middle 40s. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Middle and upper level ridging builds over the northeast on Tuesday. Surface high pressure will also build over the area in the afternoon and evening. The main forecast challenge for Tuesday revolves around the degree of stratocu, especially across the eastern half of the region. Moisture looks to move around the larger upper level low near the Canadian Maritimes and could settle over eastern Connecticut and eastern Long Island in the morning. Subsidence from the ridging aloft and surface high building overhead should allow for some clearing in the afternoon. Partly cloudy skies are expected for the western half of the area through the day. While the latest forecast is more on the optimistic side with clearing in the afternoon, it is possible mostly cloudy skies persist through the day across the eastern half of the area. Near normal high temperatures in the upper 50s are forecast for most locations with low 60s in the NYC metro, NE NJ, and Lower Hudson Valley. The ridge axis likely moves overhead Tuesday night with the surface high settling to the south of the area. Skies should be partly cloudy with some increasing high clouds from the west late. Lows will be in the 40s for most locations. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Ridge axis shifts east Wednesday into Thursday. Main focus for the long term is a developing shortwave trough over the Southeast states as it interacts with the deep mid level low north of the Great Lakes. As the low enters northern New York Gulf moisture is pulled into the forecast area Thursday into Friday. Complex dynamics begin as a southern low off the DelMarVa coast deepens in response to a 100kt jet over the Mid- Atlantic coast. This southern low drifts north into the waters south of Long Island as it does isentropic showers begin as early as Thursday morning. East winds during the day Thursday should take on a more northeasterly component late Thursday into Friday. This cold air advection works to enhance the upper level jet to 130kts possible. This will allow the coastal low located in the left exit region of the jet to deepen further and possibly retrograde Friday as it interacts with the upper level trough above the Tri-state area. We`ll have to be mindful of possible heavy rain bands forming along a secondary frontal zone across the forecast area Friday morning. Precipitable water values around one inch support steady rain for a 36 hour period beginning Thursday night through early Saturday morning. Rainfall totals between 1 to 2 inches can be expected. Can not rule out the possibility of mixed precipitation for our northern counties early Friday morning. Rain will be falling through sub- freezing temperatures aloft until the last 50mb. Surface temperatures are anticipated to be between 38-40 degrees at that time so accumulations are not expected. The low heads northeast off shore as winds die down throughout the day on Saturday. Guidance is in good agreement with keeping most of the day dry. Brief ridging then builds in aloft ahead of the next feature. There are some model differences with this next feature as the Canadian and Euro bring a shortwave on a more southerly track than the GFS. In turn the Canadian and Euro bring a stronger surface low to our southeast while the GFS brings a weaker low just overhead. Went with slight chance PoPs starting Sunday afternoon as both solutions bring precip to the area. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... A trough of low pressure over the region shifts south this evening. Mostly IFR/MVFR this evening, improving to VFR overnight. Improvement to VFR occurs generally NE to SW. Showers this evening end overnight near the time of VFR improvement. VFR on Tuesday. NE winds around 10kt back toward N overnight. Late day/early evening synoptic flow/sea breeze hybrid shifts winds SE-S for the coastal terminals. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Timing for flight category changes could be off by 1-2 hours, particularly IFR conditions, which may prevail longer than currently forecast. .OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY.... .Tuesday Night...VFR. .Wednesday...VFR. A chance of MVFR late in the day with showers. .Thursday-Friday...MVFR to IFR with a chance of rain. .Saturday...Improving to VFR through the day. Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ && .MARINE... SCA conditions will continue on the ocean waters through tonight. Wind gusts to around 25 kt are possible for the first half of the night with winds generally around 20 kt during the early Tuesday morning hours. Ocean seas will remain elevated due to latest obs into Tuesday morning with 5 to 6 ft tonight and then around 5 ft during the morning hours. Have extended the SCA until 15z Tuesday. It appears seas should subside during the remainder of Tuesday and Tuesday night with high pressure moving over the waters. Otherwise, sub-SCA conditions are expected through Tuesday night. South east winds Wednesday increase to near SCA criteria Thursday afternoon as a low pressure system nears the ocean waters. Winds increase to 20 kts with gusts up to 30 kts Thursday afternoon. Front passes Thursday night as winds become more northerly to begin the weekend with wind gusts up to 25 kts possible. Winds may reach SCA criteria through Saturday afternoon. Winds and waves are then expected to remain below SCA criteria through Monday. && .HYDROLOGY... Steady rain Thursday morning through late Friday night may bring instances of heavy rain and nuisance flooding. Rainfall totals between 1 to 2 inches are possible. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 11 AM EDT Tuesday for ANZ350-353- 355. && $$ SYNOPSIS...DJ/DS/JT NEAR TERM...JC/DS SHORT TERM...DS LONG TERM...DJ/JT AVIATION...JC MARINE...DJ/DS/JT HYDROLOGY...TM/DS/JT is the U.S. government's official web portal to all federal, state and local government web resources and services.