Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 222159 AFDOKX Area Forecast Discussion National Weather Service New York NY 559 PM EDT FRI JUL 22 2016 .SYNOPSIS... Showers and thunderstorms are possible across parts of the Tri- State Area this evening as a system moves across the area. Drier air is expected in the wake of this system for Saturday, however, it will remain hot. A dry cold front will pass across the area Saturday night. High pressure will then be in control on Sunday before a cold front moves across the area Monday into Monday night. High pressure returns for Tuesday through Thursday. Another front moves through the area on Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... We are starting to see a few showers and thunderstorms get going over Upstate New York and the northern tier of Pennsylvania this afternoon. So far, looking at the operational models, the WRF looks about the best with handling convection for this evening both the placement of QPF and with timing. A surface pressure trough is expected to accompany the convection as it works southeast later this evening aiding in lift. Although PWATs are relatively high (around 1.5 inch per the latest SPC Mesoanalysis), forecast soundings show most of the moisture is confined to a small layer around 4,000 feet above the surface. Thus, it will take a while for the atmosphere to moisten and there is some concern as to just how much convection will fill-in this evening as the trough gets closer to the coast. As a result, I leaned toward the WRF with some blending toward the RAP and HRRR which looked about the next best in-line. Forecast soundings continue to show an inverted V signature so the dry low-level environment will aid in the transfer of momentum down to the surface and make gusty winds the main threats in and near storms. However, given the high moisture content to the air we cannot rule out isolated heavy downpours in any stronger thunderstorms. The best timing for showers and thunderstorms looks to be late this evening working toward The City from the northwest with activity weakening as it heads toward the coast. Thus, I kept enhanced wording mainly from The City north and west and over CT as activity should be in a weakening state as it heads across Long Island. In any areas that see rain this evening, patchy fog may develop later tonight from whatever ground moisture there is. We also may see patchy fog on The Island and along coastal Connecticut as the warm, moist southerly flow advects fog inland from the coastal waters. Any fog should clear out shortly after daybreak. Otherwise a steamy night in The City and urbanized areas of NJ with lows 75 to 80. A high risk for rip current development at ocean beaches remains through this evening due to southerly wind waves increasing to 3 to 5 ft and a residual 2 ft se swell. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Seriously, despite the passage of a trough this evening, we will not cool off much for Saturday and another hot day will be seen across the area. However, with winds trending toward the west to northwest at all levels, this will advect in drier air that will drop surface dewpoints into the 50s to lower 60s by the afternoon. Thus, heat index values will not be as high as today and in some ways it may feel a little better. However, the west to northwest flow will `downslope` and thus drag the hotter air out even toward the coast. I leaned toward the hotter end of statistical guidance for highs as a result. The Heat Advisory will remain up for The City and we added urban parts of Essex and Union Counties in NJ as well as Hudson County where actual temperatures could get to 100 (most likely at Newark which would be about the average highest temperature of the year). No records are in threat at Newark or in the City though as we are competing against the Heat wave of 2011 when Newark set an all-time record high of 108. Another more vigorous trough passes across New England tomorrow evening, both aloft and at the surface. There may be enough moisture in interior new London County to pop off a shower or thunderstorm but otherwise it should be dry. Saturday night will be a little cooler. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... High pressure builds into the area on Sunday. High temperatures on Sunday will be in the upper 80s to low 90s for most areas, but will be in the low to mid 90s for NYC, portions of NE NJ, and southern portions of the Lower Hudson Valley. With a west to northwest flow, dewpoints should not be as high as Saturday, resulting in heat indices below 95 degrees. High pressure moves offshore Sunday night. Meanwhile a low pressure over eastern Canada will push its associated cold front through the area Monday, scattered showers and thunderstorms will develop over western areas and spread east as that front advances and pushes through the region Monday night. Highs on Monday will be in the low to mid 90s, and heat indices will top off in the mid to upper 90s. Monday night will be very warm and humid with lows near 80 around NYC, and in the low to mid 70s elsewhere. Areas of fog are likely as well. High pressure builds into the area on Tuesday, ushering in cooler and dryer air. Highs on Tuesday will be in the low to mid 90s, and with surface dewpoints in the 60s, heat indices will once again top off in the mid 90s. High pressure will continue to build across the area through Thursday. Temperatures will be in the upper 80s to low 90s on Wednesday, and mid to upper 80s on Thursday. Another cold front is then forecast to impact the local area later on Thursday and into Friday. && .AVIATION /22Z FRIDAY THROUGH WEDNESDAY/... A weak cold front approaches tonight and moves through early Saturday. Convection is very limited as of late afternoon, but we do expect some isolated convection to develop with a pre-frontal trough this evening. Movement will be from about 300 degrees. Otherwise, VFR conditions expected through the TAF period with the exception of some patchy fog and MVFR vsbys early Saturday morning outside the NY metro. S-SW winds will diminish overnight. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: Chances for TS in the terminal area are low this evening. KLGA TAF Comments: Chances for TS in the terminal area are low this evening. KEWR TAF Comments: Chances for TS in the terminal area are low this evening. KTEB TAF Comments: Chances for TS in the terminal area are low this evening. KHPN TAF Comments: Chances for TS in the terminal area are low this evening. KISP TAF Comments: Shower chances in the terminal area are low this evening. .OUTLOOK FOR 21Z SATURDAY THROUGH WEDNESDAY... .SAT AFTN through SUN NGT...VFR. W gusts up to 20 KT possible SAT AFTN. .MON...Mainly VFR, except MVFR or lower possible in scattered late day/evening thunderstorms. .TUE and WED...VFR. && .MARINE... Wind gusts at area observation sites have mainly been between 25 and 30 kts with buoys showing 4 foot waves south of Long Island. With the approaching trough, winds will still remain up until this feature passes and as a result the Small Craft Advisory will be left up. The threat of showers and thunderstorms will be greatest over the western coastal waters this evening into early tonight. There may also be patchy fog late tonight given the warm, moist air mass in place over the area. Waves and winds will decrease tonight after the trough passes on through. Lighter offshore flow on Saturday will keep waves on the low side. High pressure will influence the area waters on Sunday. A cold front moves through the waters Monday night, and then high pressure returns for the middle of next week. Below small craft advisory conditions expected for the extended period. && .HYDROLOGY... Any stronger thunderstorms that get going this evening could produce locally heavy downpours given PWATs around 1.5 inches. The main threat looks to be more on the side of minor ponding or poor drainage flooding in urbanized areas. Scattered showers and thunderstorms will impact the region Monday afternoon and Monday night, resulting in the potential for locally heavy rain. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Heat Advisory until 7 PM EDT Saturday for NYZ072>075-176-178. High Rip Current Risk until 9 PM EDT this evening for NYZ075- 080-081-178-179. NJ...Heat Advisory until 7 PM EDT Saturday for NJZ006-106-108. Heat Advisory until 7 PM EDT this evening for NJZ004-103>105- 107. MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ350-353- 355. Small Craft Advisory until 11 PM EDT this evening for ANZ345. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...24 LONG TERM...FIG AVIATION...Tongue MARINE...FIG HYDROLOGY...FIG

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