Area Forecast Discussion
Issued by NWS Upton, NY

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759 FXUS61 KOKX 230101 AFDOKX Area Forecast Discussion National Weather Service New York NY 801 PM EST Sun Jan 22 2017 .SYNOPSIS... A stationary front will remain off the southern Mid Atlantic coast tonight, with areas of weak low pressure riding east along it. Meanwhile, a strong southern low will track to the mid atlantic coast tonight and up the coast Monday into Tuesday as a major coastal low. This storm will produce very strong east winds from late tonight into Monday night. The low will slowly pass just south and east of the region Monday Night into Tuesday. High pressure will build in the wake of the storm on Wednesday. A series of weak mainly dry cold fronts will move southeast around low pressure north of New England through late week Sunday. && .NEAR TERM /THROUGH TONIGHT/... A stationary front will remain south of the region overnight. a wave of low pressure traveling along the front will result in some light rain this evening mainly across southern and western portions of the tri-state. With increasing ene flow and developing cad...not expecting much in the way of fog overnight. Winds increase overnight...with gusts 30 to 40 mph by late tonight/early Mon morning. Overnight lows tonight will slowly fall into the 30s around 40 along the coast. && .SHORT TERM /MONDAY THROUGH TUESDAY/... Intense coastal storm expected late tonight into Tuesday with high winds, heavy rain, wintry mix NW of NYC, and coastal impacts. A closed low over the Gulf states will continue to intensify tonight and then negatively tilt up the east coast Monday into Tuesday. The result will be a strong surface low over the Southeast states tonight tracking to the coast Monday, reaching a position just south of Long Island Mon Night into Tuesday morning. The low will interact with high pressure building south from Quebec to produce a very tight pressure gradient and long easterly fetch from south of Newfoundland. Models have trended even slower and a bit farther se than 24 hrs prior...but are well clustered with intense low pressure slowly tracking to the southeast of LI Mon Night into Tuesday, with the strongest winds expected Monday afternoon through the first half of Monday night. Strong Winds...Coastal areas continue with high wind warning for high confidence in sustained 30-40 mph with gusts 55-70 mph mon aft/eve. A wind advisory for interior southern CT, Westchester, Rockland, and into portions of NJ where winds gusts could reach 50 mph. Highest winds are expected across Long Island, particularly on the east end and along the south shore. This based on excellent potential for downward momentum transfer of a 65-70 kt 950-975 mb LLJ via both mixing in either a well-mixed or moist absolutely unstable boundary layer. The storm also presents high potential for a gravity wave event to unfold and enhance downward momentum transfer, as a highly unbalanced/ageostrophic upper level flow develops in the exit region of an intense upper jet streak moving up the coast, with large duct function values present in the low levels over and just south of the CWA. Heavy Rain...PW of 3-4 standard deviations above avg in tropical connection continues to be signaled. Coastal front development over e li/se ct and orographic lift over eastern faces of hilly terrain will be favored for the heaviest rainfall. Embedded convection not out of the question late Monday/Mon eve ahead of approaching closed low and with warm conveyor belt feeding into the region. Based on ensemble/operational output, expect rainfall of 1-3 inches with locally higher amounts (4+ inches). Wintry Mix...Models continue to signal strong low-level CAD under an H7-8 warm nose late tonight through Monday evening over the region. Based on strong dynamics and a deep enough cold layer well NW of NYC Mon, should see a prolonged mix of sleet and rain and interior NE NJ...Lower Hud...and SW CT...with period of just snow and sleet across Orange/Putnam/W Passaic. This will bring likelihood for 1 to 3 inches of sleet and snow in the NW hills...highest amount in highest elevations. ECMWF and GFS are indicating enough dynamic cooling for even a period of heavy snow late Mon/Mon eve well nw of NYC...but this may be due to under- estimation of the h7-8 warm nose as shown in the NAM. If the warm nose can be overcome or is weaker...there is a low potential for 3 to 6 inches of heavy wet snow across the NW Hills. Additionally...temps hovering around the lower 30s will present potential for a light glaze of freezing rain across NW hills as well...but overall not an efficient setup for heavy ice accum. A winter wx advisory has been issued to address the winter wx threat across Orange/Putnam/W Passaic for Mon aft/eve. Elsewhere...sleet could mix in briefly at the coast Mon aft/eve. Winds and heavy precip should fall off late Mon Night into early Tue morning from west to east as the LLJ moves NE...but how quickly is still in question. The slow moving storm will pass on Tuesday. With the associated upper level low remaining over the region, will continue to mention likely/cat PoP mainly in the morning. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Tuesday until Midnight...Light precipitation will end from west to east as low pressure moves east of coastal New England. The highest chc for mixed precip will be across our far west zones and across higher elevations NW of NYC. However, we are not anticipating any significant accumulations. Wednesday and Thursday...A weak ridge of high pressure will move quickly east across the region early Wednesday followed by a long wave of low pressure thru the day Thursday. No sensible weather is forecast as temps cont to avg above normal in SW flow. Friday through Sunday...signals a weather pattern change as a ridge builds across western North America and a trough develops across the Eastern U.S. This will bring colder temps across the area to close out January. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... A deep low centered over the southeastern states will track slowly to the east to northeast tonight, and becomes a coastal low off the mid Atlantic states by 00Z Tuesday. Winds will be the main issue tonight through Monday as east to northeast winds increase to 15 to around 20 KT with gusts increasing from 25 to 30 KT to near 40 KT by 12Z Monday. As rain develops Monday conditions lower to IFR and at time LIFR. A mix of rain, snow and sleet is likely at KSWF, with periods of heavy snow and sleet in the afternoon. Snow amd sleet could total 1 to 2 inches by late Monday. By late in the afternoon there is a chance of sleet at KHPN. East to northeast winds increase during Monday, peaking at around 30 KT with gusts 50 to 55 KT by late in the day. Winds will begin to slowly diminish around 00Z Tuesday. .OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY... .Monday Night...IFR in rain and fog with rain, snow and sleet at KSWF. E-NE wind 20-30 KT G30-40 KT. .Tuesday-Tuesday night...Rain ending late in the day Tuesday into Tuesday evening. Conditions improving during the evening to VFR southwest to northeast. Winds NE backing to NW during Tuesday. .Wednesday and Thursday...VFR. SW Winds 15-25 kt. .Friday...VFR. W 15-25 kt. && .MARINE... An intensifying storm moving up the coast will bring hurricane force wind gusts to the ocean waters Monday into Monday evening and possibly even the eastern Sound/bays Mon evening. On the non- ocean waters, storm warnings remain in effect. Expect peak winds 50-60 kt where storm warnings remain. Before then, gales are likely to develop quickly tonight, followed by storm force winds developing from south to north through the day on Monday. Max seas could peak at 20-22 ft on the ocean, 9-12 ft from Orient Point east, and 8-9 ft on central Long Island Sound, per combo of WaveWatch/NWPS guidance and wind/wave climatology. Marine Long Term... .Tuesday through Wednesday Afternoon...Seas will gradually subside as winds become SW at 15-20kt by Wednesday Afternoon. .Wednesday Night...Winds and seas decrease below Small Craft Advisory levels. .Thursday and Friday...Winds and seas increase to SCA on the Ocean with the approach and passage of a cold front. && .HYDROLOGY... QPF late tonight into Monday will likely be in the 1-3 inch range, with locally higher swaths possible with the heaviest rainfall Mon afternoon/eve. If high end rainfall amounts are realized, this will bring a threat for moderate urban flooding and minor small stream flooding in NE NJ and the Lower Hudson Valley. This will be exacerbated by coincidence of high tide with heavy rain Mon eve along coastal waterfront and shoreline roads...including along tidally affected rivers. Potential for minor flooding on larger rivers is slight. && .TIDES/COASTAL FLOODING... Minor coastal flooding expected along the western great south bay with Mon Am high tide along with the Southern bays of Long Island. With a slower onset of strong winds...the threat for minor coastal flooding has decreased for the NY Harbor and Western Li Sound. Primary attention is for the late Monday afternoon/evening high tide cycle. Moderate coastal flooding expected along southern and eastern bays of LI...Staten Island...low-lying north and east facing coastlines along Western LI Sound...and the Atlantic beachfront due to combo of elevated water levels and wave action. There is a low potential for major flood thresholds to be reached in the most vulnerable Great South Bay communities such as Lindenhurst and Freeport. A coastal flood warning has been issued to address this flood threat. Elsewhere minor to locally moderate coastal flooding expected. Minor to locally moderate coastal flooding could linger for the southern and eastern bay areas for the Tuesday morning high tide cycle as well. An ensemble of guidances is showing potential for surge to build to 2 to 2 3/4 ft Mon am...and 3 1/2 to 4 1/2 ft by Monday evening. The Mon evening expected surge is in line with surges seen during a March 13th 2010 with similarities in wind/wave forcing. The other concern will be for widespread dune erosion and localized washovers at Atlantic ocean beaches from elevated waters levels and an east to west sweep of 8 to 14 ft surf Mon into Tue. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...High Wind Warning from 1 AM Monday to 1 AM EST Tuesday for CTZ009>012. Flood Watch from Monday afternoon through late Monday night for CTZ009. Wind Advisory from 1 AM Monday to 1 AM EST Tuesday for CTZ005>008. Coastal Flood Advisory from 5 PM to 11 PM EST Monday for CTZ009>012. NY...High Wind Warning from 1 AM Monday to 1 AM EST Tuesday for NYZ071>075-078>081-176>179. Coastal Flood Warning from 3 PM to 11 PM EST Monday for NYZ079>081-179. Winter Weather Advisory from 1 PM Monday to 7 AM EST Tuesday for NYZ067-068. Flood Watch from Monday afternoon through late Monday night for NYZ069>075-176>179. Wind Advisory from 1 AM Monday to 1 AM EST Tuesday for NYZ069- 070. Coastal Flood Advisory from 3 PM to 9 PM EST Monday for NYZ072- 075-178. Coastal Flood Advisory from 5 PM to 11 PM EST Monday for NYZ073-176. Coastal Flood Advisory from 3 AM to 8 AM EST Monday for NYZ080- 179. Coastal Flood Warning from 7 PM to 11 PM EST Monday for NYZ071- 078-177. Coastal Flood Warning from 3 PM to 7 PM EST Monday for NYZ074. NJ...High Wind Warning from 1 AM Monday to 1 AM EST Tuesday for NJZ006-106-108. Winter Weather Advisory from 1 PM Monday to 7 AM EST Tuesday for NJZ002. Flood Watch from Monday afternoon through late Monday night for NJZ004-006-103>108. Wind Advisory from 1 AM Monday to 1 AM EST Tuesday for NJZ004- 103>105-107. Coastal Flood Advisory from 3 PM to 9 PM EST Monday for NJZ006- 106-108. MARINE...Storm Warning from 1 AM Monday to 1 AM EST Tuesday for ANZ330- 335-338-340-345. Hurricane Force Wind Warning from 1 PM Monday to 1 AM EST Tuesday for ANZ350-353-355. && $$ SYNOPSIS...BC/GC/NV NEAR TERM...BC/NV SHORT TERM...BC/NV LONG TERM...GC AVIATION...MET MARINE...BC/NV HYDROLOGY...BC/NV TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.