Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 150644 AFDOKX Area Forecast Discussion National Weather Service New York NY 244 AM EDT Sun Jul 15 2018 .SYNOPSIS... Generally weak high pressure will be in place through Sunday night with a couple of low pressure troughs moving into the region. A cold front will impact the area from late Monday into into Wednesday, with high pressure returning for the middle of next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Showers, along with a chance of some thunder continue overnight as mid-level shortwave energy and a surface reflection in the form of a trough shift through the region. Best chances for precipitation will be across eastern LI and CT as one area of rain slides east, the other will be across NE NJ and the lower Hudson Valley where additional showers move into the area.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/... Shortwave lift and the initial surface trough may still be close enough to trigger some showers Sunday morning with somewhat higher overall chances over southern sections (LI, city, NE NJ). Another shortwave is then progged to pass through during the late morning/early afternoon, then a surface trough pushes in during the later afternoon hours into the evening. All of these subtle features combined with CAPES of 1000-1500 J/KG and steep low level lapse rates will sustain the threat of showers and thunderstorms through the day and evening before chances drop off overnight with diminishing instability. Cannot rule out an isolated strong gust with any thunderstorm, but severe thunderstorm chances are low. Much of the day will at least be dry, but likely feature more in the way of cloud cover versus today. High temperatures will be within a couple degrees of today`s but it will feel more humid. A moderate risk for rip current development is expected at the ocean beaches Sunday into Sunday evening. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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A pattern change is set for Monday as high pressure shifts offshore in advance of a strong upper trough rotating through the eastern Canadian provinces. The trough may potentially phase with another area of low pressure farther north near the Hudson Bay. With the high gradually shifting offshore and low pressure gradually approaching, south to southwest flow will be prolonged into the early part of the week, allowing the advection of greater moisture levels into the region from both the Gulf and Atlantic. As such, expect humidity to quickly increase into Monday, which combined with high temperatures in the mid 80s for coastal locations and in the lower 90s for NYC and the interior will make temperatures feel as though they are in the 90s to near 100 in some spots. Along with an increase in humidity, chances for precipitation will quickly increase. By early Monday, the previously diffuse frontal boundary is expected to move northward as a warm front, leading to at least isolated showers or thunderstorms across Connecticut during the morning hours of Monday. By afternoon, a thermal surface trough is expected to develop across the interior, increasing chances for diurnal thunderstorms, some of which may produce heavy rainfall and locally gusty winds. These thunderstorms may continue into the night, gradually spreading eastward. By Tuesday, PW values are expected to be close to the 97th percentile for this time of year, and potentially close to maximum values. Continued forcing for ascent with the approaching trough and attendant cold front will lead to at least isolated showers at any time, quickly increasing into the afternoon as the front approaches at a favorable time, diurnally. Any storms that develop in a discrete manner ahead of the front may produce locally gusty winds with a dry subcloud layer and downward momentum from heavy rainfall enhancing winds. Otherwise, flow will mainly be parallel to the frontal boundary, allowing storms to quickly spread with a line developing by afternoon. Heavy rainfall will be the primary threat until the front passes to the east Tuesday night into Wednesday morning. High pressure then follows, with a return to more seasonable temperatures and humidity levels. There is potential for an area of low pressure to approach from the southwest by the weekend, but details about placement and timing are too uncertain at this time to offer further detail.
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&& .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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Broken line of showers and tstms has developed from KTEB vicinity back into into NW NJ, with a more significant cluster behind that over NE PA. This activity was moving steadily ESE and on its current motion should bring at least vicinity thunder impact initially to KTEB/KLGA/KISP, then also to KHPN and possibly KBDR. Additional showers with brief local IFR vsby were redeveloping south of the cluster of storms in NE PA, and may have to also amend all the NYC metros for brief IFR vsby impact and possible thunder. This initial activity should clear all the terminals by 12Z. Then mainly VFR conds should prevail into early afternoon, with light W flow backing more SW and increasing to 5-10 kt this afternoon, and becoming almost due S just over 10 kt at KJFK via greater sea breeze component to the wind. Could see another round of showers/tstms with MVFR/IFR flight cat and gusty winds late this afternoon. .OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY... .Late tonight...Chance of MVFR vsby developing at terminals mainly outside of NYC metro. .Monday...Chance of afternoon/nighttime showers/tstms with MVFR or lower flight cat. SW winds G15-20KT in the afternoon for coastal terminals. .Tuesday...Showers/tstms likely with MVFR or lower flight cat. SW winds G20-25KT into early evening. .Wednesday...Chance of AM showers with MVFR or lower flight cat possible. .Thursday...VFR.
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&& .MARINE... Winds and seas will generally remain below small craft levels through Sunday night. There is a chance ocean seas increase to around 5 ft tonight into early Sunday. Thinking is that the coverage and duration of 5 ft seas due mainly to a swell is not enough to go with a SCA at this time. Winds and seas will gradually increase ahead of an approaching front Monday into Tuesday, with SCA-level seas expected by Tuesday. C continued swell after the cold frontal passage may allow SCA-level seas to persist on at least the eastern ocean waters into Wednesday. Thereafter, high pressure builds across the area, allowing winds and seas to subside into late week. && .HYDROLOGY... Rainfall amounts through Sunday evening could total up to at least quarter to three-quarters of an inch across the area with the higher amounts generally NW of NYC. Local amounts above an inch will be possible due to the convective nature of the rainfall. Minor flooding could occur at any point in this period due to a relatively slow forward motion of potentially training cells, but overall flooding chances appear to be low. Another 3/4 to 1 1/4 inch basin avg rainfall likely with the slow moving frontal system from late day Mon into Wed morning. Locally heavy rainfall is possible Tuesday afternoon and night, with some potential for minor urban and poor drainage flooding. && .TIDES/COASTAL FLOODING...
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The Saturday night high tide has passed with water levels on the way down. Astronomical tides will continue to run high due to a combo of a recent new moon and onshore flow/incoming long period swells promoting tidal piling. Additional rounds of localized minor flooding are likely tonight and again Monday night along the back backs of Nassau/Queens westward to Staten Island, and across the SE CT/Westchester coastline.
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&& .EQUIPMENT... NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JC/MD NEAR TERM...BC SHORT TERM...JC LONG TERM...MD AVIATION...Goodman MARINE...JC/MD HYDROLOGY...JC/MD TIDES/COASTAL FLOODING... EQUIPMENT...

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