Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 212235 AFDOKX Area Forecast Discussion National Weather Service New York NY 535 PM EST Fri Feb 21 2020 .SYNOPSIS... High pressure slowly builds to the south through the weekend. The high will slide offshore over the Atlantic on Sunday and Monday. Weak low pressure approaches from the south and west Monday night and moves near the region on Tuesday. A stronger low pressure approaches on Wednesday and moves across the area Wednesday night and Thursday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Mainly updated dew points as they have been running lower than forecast this evening. Many locations have seen dew points range between 0 and 5 below. This is indicative of how dry the airmass is over the region. The dew points should slowly rise this evening into the single digits. Clear skies are forecast as high pressure builds from the southwest, and ridging builds aloft. The forecast challenge for tonight will be minimum temperature for areas prone to radiational cooling. Weak shortwave passes well to the north late tonight, and a sfc trough passes. Winds will back to the west, and a slight increase in the pressure gradient is expected along with an increase in winds aloft. This will hinder good radiational cooling later tonight (after midnight). However, if winds decouple sufficiently this evening, temps could fall quickly outside of the urban areas. In general, went slightly above MOS for those locations prone to radiational cooling based on the above thinking, but much colder than blended databases. Lows will range from the mid 20s in and around NYC metro, to the lower teens in the normally colder locations. A few single digits cannot be ruled out, if winds lighten more than forecast, and for a longer duration than forecast. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/... Clear skies are expected this weekend as a ridge of high pressure builds. Temperatures during the day may very well over perform (especially Sunday) in westerly downslope flow and gradual WAA. Temps will rise through the 40s Saturday, and into the 50s Sunday under abundant sunshine. Leaned warmer than MOS. Temperatures at night show fall into the 20s, except lower 30s around NYC metro. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... The quiet pattern the Tri-State area will observe for this weekend will end next week as a more active weather pattern takes shape. Monday will continue tranquil with increasing clouds late in the day. A split jet stream flow pattern will be in place with a northern stream shortwave passing across SE Canada and a southern stream shortwave moving across the central States. Above normal temperatures in the upper 40s and lower 50s are anticipated for highs on Monday. A noticeable trend in the models over the last 24 hours is to dampen the southern stream wave out faster as it approaches the northeast. The surface low associated with the shortwave looks to weaken as it approaches Monday night. Lingering surface ridging over the New England on Tuesday also creates a challenge for precipitation development. The combination of the surface ridging and weakening shortwave leads to lower probabilities for precipitation. Temperature profiles are supportive of plain rain where precip does occur and any rain will be on the light side. The highest chance for light rain appears to be Tuesday with lower chances Tuesday night as heights rise aloft and shortwave energy weakens. Cannot completely remove the mention of light rain Tuesday night into Wednesday morning as lingering overrunning may remain in place. A ridge amplifies along the Western North America on Wednesday leading to a deepening downstream trough over the Central States. The models have continued to come into agreement that this next trough will deepen another surface low over the Middle Atlantic on Wednesday and then lift the low across the northeast Wednesday night into Thursday. The persistent pattern this winter of inland tracking lows will continue with this system as the consensus of guidance indicates the parent low moves towards the eastern Great Lakes with a potential secondary developing over New England. Plain rain is the most likely precipitation type in this scenario late Wednesday through Wednesday night with mild air in place. Will have to watch if any wrap around precip can make it across the region as colder arrives when the low departs Thursday morning, but this looks like a very low probability at this time. The upper trough becomes a closed low late Thursday into Friday as it tracks across New England. Conditions should dry out with temperatures falling below normal for the end of February. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... High pressure remains across the terminals through the forecast period with VFR conditions. No cloud expected with unrestricted visibility through the TAF period. Winds becoming W this evening diminishing to 5-10 kt. Winds then back farther WSW-SW later this evening continuing overnight and Saturday. A few gusts 15-20 kt are possible Saturday afternoon. .OUTLOOK FOR 20Z SATURDAY THROUGH WEDNESDAY... .Saturday through Sunday night...VFR. .Monday...VFR. a slight chance of MVFR late in the day in ceilings and light rain. .Monday night and Tuesday...Rain likely with MVFR or lower. .Wednesday...Chance of Rain with MVFR or Lower. && .MARINE... Winds will be rather tranquil to start the night, but should increase as the night progresses. Westerly flow increases further by Saturday morning, and will issue a SCA for the ocean waters east of Fire Island Inlet. Do expect seas to build to 5 ft for those eastern waters. Sub SCA conditions are expected elsewhere. SCA winds and seas may extend into the evening Saturday night, but will not extend the hazard attm. As high pressure passes south Sunday, winds back to the SW, and will remain sub SCA. Sub-SCA conditions are expected on the waters Monday into Tuesday with a weak pressure gradient in place. An approaching low pressure system Tuesday night and Wednesday should help build seas to SCA levels on the ocean. Winds may also gust to around 20 kt on the waters on Wednesday. && .HYDROLOGY... No hydrologic issues are expected. && .EQUIPMENT... NYC NOAA Weather Radio Station KWO35 (162.55 MHz) is still operating at reduced power. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 6 AM to 6 PM EST Saturday for ANZ350- 353. && $$ SYNOPSIS...DS/PW NEAR TERM...DS/PW SHORT TERM...PW LONG TERM...DS AVIATION...IRD MARINE...DS/PW HYDROLOGY...DS/PW EQUIPMENT...

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