Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 191016 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 616 AM EDT Mon Jun 19 2017 .SYNOPSIS... High pressure over the western Atlantic will maintain a southwesterly flow of very warm and muggy air over the region today. A cold front approaching from the west will cross the area this evening and move offshore by Tuesday morning. Temporary drier conditions through mid-week will give way by week`s end to increasing warmth and moisture as the Bermuda High builds back in. Another frontal system may affect the area by next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A cold front extended from the eastern Great Lakes to the lower Ohio River Valley early this morning. The boundary will progress eastward today. Clouds were lingering over parts of eastern Pennsylvania and northern New Jersey early this morning while the sky was mainly clear over northeastern Maryland, Delaware and southern New Jersey. Much of our region should receive a fair amount of sunshine from this morning into the afternoon allowing temperatures to climb well into the 80s with some 90 degree readings in our southern counties. As the cold front approaches from the west, the chance for showers and thunderstorms will increase this afternoon. The main convective line is forecast to extend from central Pennsylvania down along the West Virginia-Virgina border around 2:00 PM. It should reach Berks County, the Poconos and the Lehigh Valley by 4:00 PM before arriving in southeastern Pennsylvania and northwestern New Jersey by 6:00 PM. Daytime heating along with abundant moisture will cause mixed layer CAPE values to rise into the 1500 to 2000 J/kg range in parts of our region this afternoon. A developing low level southwesterly jet in advance of the approaching cold front will result in increasing shear and the potential for organized convection along with strong and possibly damaging wind gusts. Much of our region remains in the Storm Prediction Center`s area for an enhanced threat of severe weather. Precipitable water values are anticipated to rise to 2.2 or 2.3 inches in parts of our forecast area this afternoon. As a result, we continue to expect heavy rain along with the potential for flash flooding. The Flash Flood Watch remains in place. Rainfall totals of 1 to 2 inches are forecast to be common with localized amounts of 3 to 4 inches possible.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
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The main convective line should work its way across the Interstate 95 corridor early this evening before passing off the coast late this evening. The threat of severe weather and flash flooding will continue. Low clouds and lingering showers are anticipated for a few hours after the cold front passes, then some clearing is expected late tonight. Temperatures should drop into the 60s and lower 70s overnight. A light southwest to west wind is forecast.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/...
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The cold front that moves across the Monday night should be off the NJ/DE coast by Tuesday morning. However with southwest flow continuing aloft further progress may be slow. The forecast keeps a chance of showers for Tuesday morning over southeast DE and the DE/NJ coastal waters. Otherwise slightly cooler and somewhat drier air should filter in behind the cold front for Tuesday into Wednesday. Temperatures are forecast to remain a few degrees above normal but lower dewpoints should make for overall pleasant conditions with no precip expected. By Thursday the upper trof moves away to the east allowing for some weak ridging aloft. Low level warm advection increases along with rising surface dewpoints. Instability may be limited but the forecast has a chance of t-storms mainly north/west of PHL. It appears that another cold front an associated upper trof will approach from the northwest Friday or Saturday, but timing is uncertain at this point. The front may also be preceded by a surge of tropical moisture from the GulfMex. Given the uncertainty for forcing and the overall summer-like pattern, the forecast includes a chance of t-storms for Friday and through the weekend for the entire area.
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&& .AVIATION /10Z MONDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are expected to start the day under a mostly clear sky. We are anticipating an increase in cloud cover for this afternoon as showers and thunderstorms approach from the west. A line of strong to severe thunderstorms is forecast to work its way across our TAF sites from west to east between about 2000Z and 0200Z. MVFR conditions and scattered showers are expected to linger in the wake of the thunderstorms early tonight with some improvement to VFR possible late tonight. A south southwest wind around 10 to 15 knots with gusts of 20 to 25 knots is expected for today. The wind is forecast to become southwest to west for tonight at speeds of 5 to 10 knots. OUTLOOK... Tuesday through Thursday...Mainly VFR conditions expected. Low possibilities for sub-VFR restrictions from stratus/fog late night/early morning each day. Southwest winds 10 kt or less. Friday...Chance for MVFR or tempo IFR conditions in showers and thunderstorms.
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&& .MARINE...
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The Small Craft Advisory remains in effect for today and tonight on our ocean waters. The Small Craft Advisory is in effect for Delaware Bay from 10:00 AM until 11:00 PM. A gusty south to southwest wind is anticipated for today. Wind gusts of 25 to 30 knots are expected. While wind speeds are forecast to diminish tonight, wave heights on our ocean waters should remain in the 5 to 8 foot range. OUTLOOK... Tuesday...Winds veer slightly out of the W-SW and weaken to below 25 kt. However seas will be somewhat slow to subside and are expected to remain at 5 ft or higher much of the day. Therefore the SCA has been extended until 600 pm Tuesday. Tuesday night through Friday...Winds and seas expected to remain below SCA headline criteria. RIP CURRENTS... We will continue with the high risk for the development of dangerous rip currents for today along the coast of Delaware and New Jersey. We are expecting a 6 to 7 second southerly wind wave on top of a very long period (around 15 to 16 seconds) southeasterly ground swell. The combination will result in the development of dangerous rip currents. The primary wave period is forecast to be around 7 seconds from the south on Tuesday and Wednesday. However, the underlying 13 to 16 second southeasterly swell is expected to linger into the mid week period. As a result, the risk for the development of dangerous rip currents is anticipated to be at least moderate through the period along the coasts of Delaware and New Jersey.
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&& .EQUIPMENT...
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NWS NWR and phone broadcast of the marine and surf zone forecasts. Problems continue here at NWS PHI. Hope to resolve today.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...Flash Flood Watch from noon EDT today through this evening for PAZ060>062-070-071-101>106. NJ...Flash Flood Watch from noon EDT today through this evening for NJZ001-007>010-012-013-015>019. High Rip Current Risk through this evening for NJZ014-024>026. DE...Flash Flood Watch from noon EDT today through this evening for DEZ001. High Rip Current Risk through this evening for DEZ004. MD...Flash Flood Watch from noon EDT today through this evening for MDZ008. MARINE...Small Craft Advisory until 6 PM EDT Tuesday for ANZ450>455. Small Craft Advisory from 10 AM this morning to 11 PM EDT this evening for ANZ430-431.
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&& $$ Synopsis...AMC Near Term...Iovino Short Term...Iovino Long Term...AMC Aviation...AMC/Iovino Marine...AMC/Iovino Equipment...Staff

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