Area Forecast Discussion
Issued by NWS Upton, NY

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930 FXUS61 KOKX 221657 AFDOKX Area Forecast Discussion National Weather Service New York NY 1157 AM EST Sun Jan 22 2017 .SYNOPSIS... A stationary front will remain off the southern Mid Atlantic coast today, with areas of weak low pressure riding east along it. Meanwhile, another low will move across the southern states today, and intensify into a major coastal storm tonight into Monday, while high pressure builds southeast into New England. This combination will produce very strong east winds from late tonight into Monday night. The low will pass over or just south and east of the coastal waters on Tuesday. High pressure will build in the wake of the storm on Wednesday. A cold front will then slowly approach from the west and move through on Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Fog has improved a bit over the last 2 hours, with most locations improving to greater than 2 miles. This improving trend should continue for the afternoon. Skies should remain cloudy this afternoon as a weak low moves along a stationary front off the Delmarva coast. Some associated light rain possible this afternoon, especially late, as ridging aloft finally beings to move east. && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/... Significant coastal storm expected late tonight into Tuesday with high winds, heavy rain, and coastal impacts. A closed low over the southern Plains will continue to intensify and move east to the southern Mid Atlantic region on Monday. The eventual result will be a strong surface low developing over the Southeast states Sunday night and riding up the coast through Monday, reaching a position just south of Long Island by late Monday night. 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. Model spread is closing with regard to timing of the strongest winds and heaviest rain, with the strongest winds expected Monday afternoon and evening. Strong Winds...upgraded coastal areas to a high wind warning for high confidence in sustained 30-40 mph with gusts 60-70 mph. Highest winds 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 70-75 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. Put up a wind advisory for interior southern CT, Westchester, Rockland, and into portions of NJ where winds gusts could reach 50 mph. PW of 3-4 standard deviations above avg continues to be signaled. Coastal front development 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. Models still indicated low-level CAD under an H7-8 warm nose late tonight through Monday afternoon 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 well NW of NYC through the day on Mon mainly across Orange/Putnam/W Passaic, where up to an inch of accumulating sleet is possible, with lower amounts across interior SW CT along/north of I-84. Winds and heavy precip should fall off later Mon Night from wet- 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 SATURDAY/... Rain chances should gradually diminish through Tuesday night. Generally looking at mostly dry conditions Wednesday through Saturday. A cold front will bring cooler conditions for the end of the long term period. Expect highs Tuesday through Thursday in the middle and upper 40s, a good 10 degrees above normal. Friday and Saturday, high temperatures fall back to near normal, with high in the upper 30s and lower 40s. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... Weak low pressure rides along a stationary front to the south today. A coastal storm then approaches tonight. Widespread IFR to LIFR conditions will persist through at least 16Z. Conditions begin to improve around 16Z, with MVFR conditions possible by that time. Overall improvement of conditions is somewhat uncertain and there is a chance IFR conditions remain into the afternoon. With the approach of the low from the south tonight, rain becomes likely later this evening and overnight. Light winds initially become east to northeast, 5 to 10 KT. Winds increase through the day, to near 15 KT with gusts 20-25 KT this evening. Winds increase further late tonight. .OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY... .Monday-Monday Night...IFR in rain and fog. LLWS. Rain and sleet at KSWF. E-NE wind 25-35 KT G40-50KT, occasional higher gusts near the coast. .Tuesday-Tuesday night...Rain tapering off by afternoon with improving ceilings into the evening. NW winds G25-35KT, highest in the morning. .Wednesday and Thursday...VFR. SW Winds 15-25 kt. && .MARINE... Dense fog advisory for all forecast waters now in effect for the rest of the day. Expect visibilities to remain 1 mile or less. There are some locations where visibilities have improved, but this seems to be somewhat isolated. 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. Ocean has been upgraded to a hurricane force wind warning, while storm warnings remain in effect for the remaining waters, with peak winds 50-60 kt expected. Before then, gales are likely to develop quickly tonight, followed by storm force winds developing from south to north through the day on Mon. 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. Winds start to diminish on Tuesday, however there could be a period of NW gales on the back side of the storm late day Tue into Tue evening on the ocean. Ocean seas will also take quite some time to fall below 5 ft thereafter. && .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 would be exacerbated by coincidence of high tide with the heavy rain Mon eve. Potential for minor flooding on larger rivers is slight. && .TIDES/COASTAL FLOODING... A strong coastal storm will impact 2 successive high tide cycles of at least minor coastal flooding. The first tide cycle to be impacted is late tonight into early Monday morning. Minor coastal flooding is expected in spots as astronomical tides run a little higher than the late afternoon/evening tides. East/northeast winds are increasing during this time, but will not be quite at their peak. Expect the lower NY Harbor areas to experience minor coastal flooding, along with the South Shore and eastern bays of Long Island, and western Long Island Sound. Then, attention turns toward the next high tide cycle late Monday afternoon/evening. Potential for moderate coastal flooding for southern and eastern bays and beachfront communities of LI with this Monday evening high tide, and widespread minor coastal flooding elsewhere. The moderate coastal flood potential will increase if the slower coastal low movement (stronger E/NE winds Mon evening) comes to fruition...with even a low potential for major flood thresholds to be reached in the most vulnerable communities such as Lindenhurst and Freeport. A coastal flood watch has been issued to address this moderate flood threat. Minor 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 3 ft Mon am...and 3 1/2 to 4 1/2 ft by Monday evening. The highest threat for coastal impacts will be for flood prone locales along the south shore bays of LI/NYC...eastern bays of LI...lower NY/NJ harbor including tidally affected rivers...and western LI Sound. 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 12 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. Wind Advisory from 1 AM Monday to 1 AM EST Tuesday for CTZ005>008. Coastal Flood Advisory from 6 AM to 10 AM EST Monday for CTZ009. NY...High Wind Warning from 1 AM Monday to 1 AM EST Tuesday for NYZ071>075-078>081-176>179. Coastal Flood Watch from Monday afternoon through Monday evening for NYZ079>081-179. Coastal Flood Advisory from 4 AM to 8 AM EST Monday for NYZ074- 075-079>081-178-179. Wind Advisory from 1 AM Monday to 1 AM EST Tuesday for NYZ069- 070. Coastal Flood Advisory from 6 AM to 10 AM EST Monday for NYZ071-073-078-176-177. NJ...High Wind Warning from 1 AM Monday to 1 AM EST Tuesday for NJZ006-106-108. Coastal Flood Advisory from 4 AM to 8 AM EST Monday for NJZ006- 106-108. Wind Advisory from 1 AM Monday to 1 AM EST Tuesday for NJZ004- 103>105-107. MARINE...Dense Fog Advisory until 6 PM EST this evening for ANZ330-335- 338-340-345-350-353-355. 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/Goodman NEAR TERM...BC/Goodman SHORT TERM...Goodman LONG TERM...BC AVIATION...PW MARINE...BC/Goodman HYDROLOGY...Goodman TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.