Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221148 AFDOKX Area Forecast Discussion National Weather Service New York NY 648 AM EST Sun Jan 22 2017 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Cancelled dense fog advy as vsbys have lifted in most places, except perhaps right along immediate south facing coastlines. Widespread fog was across the region as a saturated air mass under an inversion remains into early morning. At the upper levels weak ridging moves east. 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.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
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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. 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.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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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.
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&& .AVIATION /12Z SUNDAY THROUGH THURSDAY/... Widespread IFR to LIFR conditions will remain through the early morning hours as a saturated low layer remains under an inversion. Winds will be light and variable to calm early this morning. A wave of low pressure passes to the south today. A large low pressure system moves from the lower Mississippi Valley into the Tennessee River Valley during the day, and into the Ohio Valley tonight. Conditions begin to improve around 14Z, with MVFR conditions possible by around 16Z. Timing is uncertain at this time, and there is a chance IFR conditions remain into the afternoon. With the approach of the low from the south, rain becomes likely around 23Z or shortly after. Winds become east to northeast, 5 to 10 KT this morning after 12-14Z, and increase through the day, to near 15 KT with gusts 20-25 KT by late in the afternoon into the early evening. There is a chance the low approaches more slowly, then rain and gusty winds would be delayed. .OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY... .Late tonight...MVFR TO IFR in rain and fog. At KSWF light sleet AND RAIN likely toward 08Z. E-NE wind 20-30 KT G35-45 KT. .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...
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Dense fog remains across the forecast waters through the morning. 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.
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&& .HYDROLOGY...
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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.
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&& .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...
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CT...High Wind Warning from 1 AM Monday to 1 AM EST Tuesday for CTZ009>012. 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. 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. MARINE...Dense Fog Advisory until 10 AM EST this morning 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.
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&& $$ SYNOPSIS...Goodman/BC NEAR TERM...Goodman SHORT TERM...Goodman/PW LONG TERM...BC AVIATION...PW MARINE...Goodman/BC HYDROLOGY...Goodman TIDES/COASTAL FLOODING...PW

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