Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 250817 AFDOKX Area Forecast Discussion National Weather Service New York NY 417 AM EDT MON JUL 25 2016 .SYNOPSIS...
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A cold front approaches today and moves through the region tonight. High pressure builds to the west Tuesday and moves off the southeast coast Wednesday into Thursday. A weak cold front approaches the region Friday and may linger into the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Lead shortwave moves through the region this morning with warm front lifting north through the region. Scattered showers associated with this feature...across se pa/nj...may translate east across nyc/nj metro and li this morning. Shearing northern stream shortwave then approaches late today with pre-frontal trough approaching the region late this afternoon crossing the region this evening. Trailing cold front crosses tonight. Morning convection and cloud cover complicates the temperature and instability forecast for today. With subsidence in wake of lead shortwave and warm front lifting north...expecting opportunity for at least partial clearing late morning into early afternoon. This should allow for temps to rapidly heat up late this morning into early afternoon. Temperatures away from the south coasts should be able to climb into the lower to mid 90s...with dewpoints rising into the lower 70s. Heat indices of 100 to 104 likely across nyc/NJ metro...with isolated 105 possible. For most of the remainder of the region...heat indices peaking around 100 degrees. The exception will be southern and eastern coastal areas limited to the mid to upper 80s due to morning cloud cover and onshore flow. Despite this...heat indices could still peak in the mid to upper 90s as dewpoints should surge into the lower to mid 70s. In terms of convection...would expect subsidence in wake of lead shortwave to limit convective potential late morning into early afternoon. Can`t rule out an isolated storm developing along the developing pre-frontal/lee trough and tracking eastward into NE NJ /Lower Hud during this time. Better chance for shra/tsra development along this boundary appears to be late afternoon into this evening with lift from approaching shortwave energy and right rear quad of jet streak. This forcing in combination with marginal to locally moderate instability...thanks to a subtle elevated mixed layer...in a very moist environment should support scattered to numerous showers and thunderstorms developing along the pre-frontal W/NW of NYC metro late this afternoon and then translating eastward through Lower Hud/NE NJ/SW CT/ and NYC metro and towards the western coastal areas late today into this evening. Strengthening uni- directional deep layer shear and tstm coverage should support storm organization into some strong to severe storms (line segments) affecting NYC/NJ/LI metro and points N/NW/W. Damaging winds from wet micro/macro bursts looks like the main threat based on uni-directional wind fields...deep moisture...and inverted V soundings. Relatively quick storm motions should localize flash flood threat to areas with training tstms. Convection should become elevated and weaken this evening as it translates farther east across LI/Southern CT as it runs into a deeper marine stable layer. Convection should push offshore by around midnight as shortwave axis moves across. Drier air slowly advects in late tonight with weak cold frontal passage. Areas of fog possible across outlying areas in warm and muggy airmass.
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&& .SHORT TERM /TUESDAY/...
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Shortwave axis slides offshore Tuesday...with deep WNW flow on Tuesday. With 850 hpa temps still running in the high teens...deep mixing...downslope flow and full sunshine...expect temps to quickly rise into the mid 90s for much of the coastal plain. Lower 90s for nw hills...and potential for a few upper 90s for NYC/NJ metro. Noticeably lower dewpoints should keep heat indices close to air temps...but close to heat advisory criteria for NYC metro. Sea breezes should be limited to late day and immediate south coasts...if at all.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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High pressure builds across the area on Tuesday night then moves offshore on Thursday. A stalled frontal boundary south of the area will remain through the weekend. Showers and thunderstorms are possible during the afternoon and evenings Thursday and through the weekend, as waves of low pressure begin to ride along this frontal boundary. Temperatures on Wednesday and Thursday will be above normal with highs in the upper 80s to lower 90s and returning to normal levels on Friday and through the weekend with highs in the low to mid 80s.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/... A warm front lifts through the terminals during the pre-dawn hours as high pressure slides offshore. A cold front approaches this afternoon and passes through the region this evening. High pressure returns tonight. Primarily a VFR forecast for most terminals. Some convection associated with an approaching warm front developing over SE PA and W NJ will lift towards the region and could impact western terminals by 09-10Z. That wave of convection should pass through the terminals by 13-15Z. Brief MVFR conditions possible. MVFR VSBYs possible in HZ for KNYC terminals from late morning through early afternoon. VFR otherwise. Cold front approaches this afternoon. Convection will fire up west of the region and looks to impact western terminals from around 20Z-02Z. SW flow less than 10 KT will give way to afternoon sea breezes at coastal terminals 10-15 KT. Gusty winds and heavy rain possible in convection. VFR conditions expected tonight, but it is possible that outlying terminals, such as KHPN and KGON could have MVFR or lower VSBYs in fog late tonight. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Tonight...SHRA/TSRA taper off from west to east. MVFR VSBY possible north and east of KNYC in fog. .Tuesday-Wednesday Night...VFR. .Thursday-Thursday Night...Mainly VFR, except MVFR or lower possible in isolated to scattered showers and thunderstorms, mainly late in the day and at night. .Friday...Chance of MVFR or lower in scattered showers and thunderstorms. && .MARINE...
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Sub sca conditions expected through Tuesday. S/Sw winds gusts to 20 kt possible for most waters this afternoon...with nearshore NW winds gusts to 20 kt possible Tuesday afternoon. Ocean seas should remain in the 2 to 4 ft range. Slight tstm threat on the water this morning with greater chance late today through this evening. Below small advisory conditions expected across the area waters from Tuesday through Friday.
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&& .HYDROLOGY...
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There is the potential for 1/4 to 1/2 inch of rainfall, with locally higher amounts, possibly 2+ inches, as numerous showers and thunderstorms track across the region late this afternoon into this evening. This presents a localized flash flood threat...mainly across nyc/nj metro and interior with any training cells. There is the potential for scattered showers and thunderstorms, across the area during the afternoons and evenings Thursday through next weekend.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Heat Advisory from noon today to 8 PM EDT this evening for CTZ005>007-009-010. NY...Heat Advisory from noon today to 8 PM EDT this evening for NYZ067>075-078-080-176>179. NJ...Heat Advisory from noon today to 8 PM EDT this evening for NJZ002-004-006-103>108. MARINE...None.
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&& $$ SYNOPSIS...FIG/NV NEAR TERM...NV SHORT TERM...NV LONG TERM...FIG AVIATION...MPS MARINE...FIG/NV HYDROLOGY...FIG/NV

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