Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 090723 AFDOKX Area Forecast Discussion National Weather Service New York NY 223 AM EST Mon Dec 9 2019 .SYNOPSIS... An approaching warm front will lift to the north Monday night. A cold front will then approach on Tuesday and slowly pass across from Tuesday night into Wednesday. Arctic high pressure will then follow later in the week before another potential storm system arrives next weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Light precip has broken out ahead of schedule, especially across interior southern CT where temps were still below freezing in spots. From ASOS obs and model fcst thermal profiles some spotty light freezing rain/sleet occurring, and issued SPS for the far northern CT zones. May still yet have to watch the valleys or Orange County for the same if the precip shield to the south expands NW from its current location over NE/central NJ. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... Warm advection light to moderate rain will continue developing and spreading north through the morning hours. The rain may briefly taper off as the warm front draws near the local area late morning or early afternoon. The 12z model suite is general agreement with this scenario. Large scale forcing increases in the afternoon and evening as parent low pressure and upper level trough move across the Great Lakes. A strong subtropical upper level jet stream will ride around the base of the upper trough and nose towards the northeast Monday afternoon and evening. Upper level divergence increases ahead of this jet and should combine with low level warm advection and shortwave energy to provide widespread rain in the afternoon and evening. The rain could be moderate to locally heavy at times. The jet dynamics will shift north of the area Monday night. The warm front should also lift north as the parent low pressure moves from the Great Lakes to southeast Canada. Rain will taper off from southwest to northeast around or just after midnight. Deep moisture and stronger forcing for ascent shift to the north and east after midnight with the rain tapering off from southwest to northeast. PoPs drop off significantly around day break Tuesday, but cannot completely rule out some lingering light rain. Rainfall amounts through Monday night look to range from about an inch to an inch and a quarter. Have continue to leave out mention of thunder with minimal elevated instability. Temperatures on Monday will be significantly warmer than the past several days. Highs should reach the lower and middle 50s for most locations, with upper 50s along the coast. Temperatures Monday night will not change too much from late day readings in the 50s. Fog potential appears low at this time, especially early Tuesday morning. However, it bears watching with temperatures well into the 50s moving over SSTs in the upper 40s to near 50. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Main impacts/forecast challenges this time frame will be post frontal precipitation Tuesday night into Wednesday, and next system over the weekend. Much depends on placement of upper jet, and eventual evolution of the upper level trough during the mid week period. Based on 12Z model suite and in collaboration with surrounding offices/WPC, lingering upper trough and placement of upper jet should result in a continuation of post frontal precip Tuesday night into Wednesday morning. A transition from rain to snow will occur as colder air advects in NW to SE. With lingering QPF of a quarter to a third of an inch around the time of transition, 1 to 4 inches of snow is possible across the area. Reasonable worst case scenario of around 6 inches is possible in spots away from the immediate coast. Much can change, so stay tuned. Prior to that, low coverage for showers within the warm sector Tuesday morning will give way to increasing Pops Tue afternoon along the cold front, with plain rain expected. Dry weather returns Wed afternoon through Friday as high pressure builds. Airmass does not look quite as cold as it did for the past few days, but chilly air is expected behind the front, with highs Thursday around or just above freezing. WAA precip may arrive late Friday or Friday night from the south, but model differences in upstream trough remain, so confidence in exact forecast details such as timing and coverage of precip remains low. At this time, would generally expect wet weather Saturday (mainly rain), and possibly into Sunday although dry air advecting in from the west should result in lower rain chances Sunday. Temperatures will warm to above normal late week and next weekend. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... MVFR/IFR conditions develop with rain moving in ahead of an approaching frontal wave from the south. Generally IFR ceilings on Monday, with rain that could be moderate to occasionally heavy through the day into evening. Light south to variable winds will become S/SE toward daybreak ahead of an approaching warm front. S winds then ramp up late morning into the afternoon at 15-20 kt with gusts 25 to 30 kt along the coast. Isolated G35-40 kt possible. LLWS with SSW winds of 40-50 kt at 2kft. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Tuesday...MVFR or lower conds in showers. SW gusts around 20 kt possible. Winds shift to the NW with gusts 25-30kt with a cold frontal passage in the late afternoon/evening. .Tuesday Night into Wednesday...MVFR or lower with rain in the evening, likely becoming IFR or lower transitioning to sleet then snow late Tuesday Night, continuing into Wednesday morning push. W- NW G20-25kt possible. Potential for light snow accumulations. Snow ends Wednesday afternoon with conditions improving to VFR. .Thursday into Friday...VFR. && .MARINE... SCA remains in effect on the ocean waters through 09Z. There is a short period where winds drop off early Monday morning. However, an approaching warm front from the south will aid in winds ramping up quickly by Monday afternoon. Winds on all waters will increase to SCA levels in the afternoon and gales look to develop on the ocean. The highest potential for gales appears to occur late in the afternoon through Monday night. Have converted the gale watch to a gale warning on the ocean waters and have issued a SCA on the LI Sound, LI Bays, and NY Harbor for Monday afternoon through Monday night. Ocean seas will also build to 7 to 12 ft late Monday afternoon and Monday night. Southwesterly winds will diminish Tuesday as the cold front approaches, with rough seas subsiding somewhat as a result. The front passes through the area Tuesday night with marginal SCA conditions possible Wednesday into Thursday morning in a W-NW flow. Winds diminish and seas subside quite a bit Thursday afternoon and Thursday night. There is the potential for another storm system to impact the waters at the end of the week. && .HYDROLOGY... A long duration precipitation event is expected from late tonight into Wednesday. The precipitation late tonight into Tuesday will be in the form of plain rain. The precipitation transitions to frozen Tuesday night into Wednesday morning. Total liquid equivalent precipitation of 1 to 2 inches is forecast. Nuisance/poor drainage flooding may occur on Monday afternoon and Monday night when the heaviest rain falls. Next significant rain of at least a half an inch is expected by the weekend. Too early to ascertain hydrologic impacts. && .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 noon today to 6 AM EST Tuesday for ANZ330-335-338-340-345. Small Craft Advisory until 4 AM EST early this morning for ANZ350-353-355. Gale Warning from noon today to 6 AM EST Tuesday for ANZ350- 353-355. && $$ SYNOPSIS...DS/PW NEAR TERM...DS/PW SHORT TERM...DS LONG TERM...PW AVIATION...DJ/16/DW MARINE...DS/PW HYDROLOGY...DS/PW EQUIPMENT...//

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