Area Forecast Discussion
Issued by NWS Upton, NY

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122 FXUS61 KOKX 240445 AFDOKX Area Forecast Discussion National Weather Service New York NY 1245 AM EDT Mon Apr 24 2017 .SYNOPSIS... High pressure moves offshore overnight into Monday. A wave of low pressure over the southeastern states moves to the southeast coast Monday, then tracks up along the eastern seaboard through midweek. High pressure will build back in for the end of the week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Only minor adjustments at this time to temperature, dew points, and cloud cover for trends. Also raised overnight lows along the coast, mainly the twin forks, several degrees with light onshore flow. Region will lie in a near zonal upper flow between a polar upper low over interior Quebec and a closed upper low moving through the deep south. At the surface...high pressure continues to move east of Long Island and southern New England overnight. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... Models in fairly good agreement with a closed upper low over the deep south Monday...slowly sliding to the southeastern US coast Monday Night. In response...a broad southern low should develop into a coastal low pressure along the Southeastern US coast Monday night. Locally...weak ridging surface/aloft on Monday appears to give way to approaching lead short wave energy ahead of the upper low...with surface high pressure gradually sliding offshore. Timing and strength of the approaching shortwave energy and of associated theta- e advection range from late Monday afternoon into Monday night...which is resulting in timing spread of onset of rain development into the region. Latest trend is slower onset of rain late Monday into Monday night...with increasing likelihood of rain from south to north late Monday Night. In addition e/ne winds will be increasing along the coast Monday Night...with gusts 25 to 30 mph possible by daybreak Tuesday. Despite higher temps aloft than Sunday...increasing high and mid cloud cover and easterly flow will likely keep temps near seasonable levels on Monday. Near seasonable temps Monday night. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Models have come into better agreement with the track of the low up the east coast Tue/Wed....with the GEM and NAM both shifting eastward as compared to 24 hours ago. NWP is in good agreement through the end of the week...but then differences are apparent for next weekend leading to a low confidence forecast. Low pres over NC Tue morning will track to the Mid Atlantic coast Tue night while weakening. A tight pres gradient will remain across the area due to departing high pres to the north producing gusty easterly winds. 40-50 kt LLJ lifts through late Tue aftn/eve...but a low level inversion should keep most of these winds aloft. Rain becomes widespread Tue morning with strengthening overrunning pattern. Timing of heaviest rainfall will coincide with the LLJ late Tue aftn/eve and location is pointing towards the eastern Long Island/CT. See hydro section for rainfall amounts and potential impacts. Winds abate on Wed as the low approaches and passes just S of Montauk Wed night. Noting mid level drying from west to east on Wed...have transitioned to light rain/drizzle. Sfc Low is slow to depart and continues to weaken Wed night/Thu before being absorbed back into the synoptic flow. Meanwhile...a broad upper trough will be developing over the rest of the CONUS with a shortwave tracking through the Great Lakes on Thu. Downstream ridging will limit the eastward progression of this system with a sfc cold front moving into the area Thu night and stalling nearby with potentially unsettled weather through the weekend. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... VFR overnight and Monday as high pressure builds over the northeast and moves offshore. Clouds will lower late in the day Monday, but should remain 5 kft or higher. S/SE winds diminish overnight and become light and variable outside of city terminals. E/SE winds prevail Monday, around 10 kts. A few coastal locales may see a few afternoon gusts to 15 to 20 kt. .OUTLOOK FOR 00z TUESDAY THROUGH FRIDAY... .Monday night...VFR in the evening, then chance MVFR later at night. .Tuesday...IFR/LIFR in rain. NE gusts 20-25 KT near coast possible during the day. .Wednesday...MVFR, possibly improving to VFR later in the day. .Thursday-Friday...VFR. && .MARINE... Winds and seas forecast on track and no changes were made at this time. With high pressure influencing the waters overnight into Monday morning, tranquil conditions are expected on the waters. A low pressure system will slowly move up the southeastern coast Monday into Monday Night...allowing for a tightening E/NE gradient over the waters late Monday into Monday night. A return to SCA conditions are expected on the ocean waters Monday night...and likely across the nearshore waters later Monday night. SCA conds will likely continue on the waters into Wed morning for both winds and seas. Gusts then diminish...although seas will remain elevated through Fri due to swells from the weakening storm system. There is a low potential for gale force winds...mainly on the ocean waters Tue/Tue eve. && .HYDROLOGY... Between 3/4 and 2 inches of rainfall is possible late Monday into Wednesday. Highest amounts are expected across eastern Long Island/CT attm. Minor flooding of low lying and poor drainage areas is possible. && .TIDES/COASTAL FLOODING... Potential for minor coastal flooding for vulnerable coastal communities...mainly along the southern bays of Western LI and Western LI Sound...with the Tue eve high tide cycle. This is in response to a low pressure system moving northward along the eastern seaboard. Only 1/2 to 1 ft of surge is needed to reach minor flood thresholds Tue evening. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Tuesday for ANZ330- 335-338-340-345. Small Craft Advisory from 6 PM this evening to 8 PM EDT Tuesday for ANZ350-353-355. && $$ SYNOPSIS...24/NV NEAR TERM...MET SHORT TERM...NV LONG TERM...24 AVIATION...PW MARINE...MET HYDROLOGY...24/NV TIDES/COASTAL FLOODING...

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