Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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021 FXUS61 KPHI 192004 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 404 PM EDT Tue Sep 19 2017 .SYNOPSIS...
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Hurricane Jose will move northeastward through Wednesday and then stall well offshore of the mid-Atlantic coast through the weekend. Meanwhile, high pressure will build southward from eastern Canada during the second half of the week and then remain anchored over the region into early next week.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Dangerous surf and rip currents along with coastal flooding are the main impacts from Hurricane Jose. The center of Hurricane Jose will remain at least a few hundred miles offshore as it continues to parallel the East Coast, and it should be due east of the central New Jersey coast near daybreak Wednesday. Our sensible weather is being driven by the circulation around Jose, however this will gradually wind down through tonight. A gusty northeast to north wind is occurring this afternoon across much of the area, with the strongest winds along the coast. The model guidance shows winds of 40-50 knots at 925 mb (strongest closer to the coast), however this diminishes gradually through the overnight. As a result of this and also the boundary layer becoming more stable tonight away from the coast will allow for less mixing and therefore less wind at the surface. A couple of somewhat organized bands of showers continue to rotate southwestward well west of the center of Jose. This is within an area of mostly weak mid level convergence. Farther to the west, there is more subsidence and drying and therefore the showers have struggled to make it more inland with even more sunshine and warmer temperatures. There will still be some showers into this evening into the I-95 corridor and perhaps a few a bit farther west. Overall, the showers should dissipate or retreat back to the east and northeast through the night as Jose works northward. As a result, the PoPs decrease from southwest to northeast. Cloud cover should linger the longest closer to the coast. Low temperatures are mainly a blend of MOS and continuity. The hourly temperatures incorporated some of the high-res guidance.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
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An upper-level ridge is forecast to build across the Ohio Valley and eastern Great Lakes then north of Hurricane Jose. This will weaken the steering flow and allow Jose to slow down and meander southeast of Cape Cod during Wednesday. While the pressure gradient remains on the tightened side and there will be a northwest breeze, it is not expected to be all that strong. There should be enough subsidence to the west of Jose to result in more sunshine although at least some cloud cover is expected especially across the northern half of the area. Some guidance hinting at a few showers possible across the northern zones especially in the afternoon, however the chance looks to small given a lack of overall forcing and therefore we continued with a dry forecast. High temperatures are closer to the warmer GFS MOS as some subsidence should allow a bit more warming especially for the southern and western areas.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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Jose is expected to become a post-tropical storm Wednesday night or Thursday and meander about 400-500 miles east of the NJ coast through the end of the week and possibly all the way into early next week. The large-scale pattern through the duration of the long term looks to be amplified, featuring persistent troughing over the western CONUS, downstream ridging over the eastern CONUS and tropical activity over the western Atlantic. Owing to upper ridging and surface high pressure over our area, a clear signal for warm and dry conditions exists for the next 7 days. No mention of rain through the entire period. Northerly flow regime is typically indicative of cold air advection. In this upcoming pattern, persistent northerly flow around the backside of Jose and away from the center of the surface high will actually yield warm air advection as the core of the heat (owing to a maximum of subsidence) will be located underneath the anticyclone that will be anchored just to our north and west throughout the period. High temperatures in the 80s will be common across the area (except cooler in the 70s at higher elevations in NE PA/NW NJ and along the coast), which are 5-10F above normal for late September. Sunday and Monday should be the warmest days of the period (temps 10-15F above normal) with the center of the anticyclone expanding toward the northern mid-Atlantic region. There is a potential that a few spots could reach 90F (particularly the urban centers) on one or both of these days.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Rest of this afternoon...VFR ceilings overall, although some MVFR ceilings lingering at and near KACY. Some MVFR visibility due to showers will affect mainly KMIV and KACY at times, however a few showers will be near KTTN, KPHL/KPNE to KILG. Northeast to north winds around 15 knots with gusts to 25 knots, with the strongest winds mainly closer to the coast. Tonight...VFR overall, although some MVFR ceilings can occur for a time mainly at KMIV and KACY. Any showers should end in the evening. North to northwest winds diminishing to around 10 knots. Wednesday...VFR with cloud bases at or above 4000 feet. Northwest winds around 10 knots, with some gusts up to 20 knots possible. Outlook... Wednesday night through Sunday...VFR. However, patchy radiational fog cannot be ruled out early Thursday morning at the typical fog- prone terminals (RDG, ABE, MIV) but setup for fog becomes less favorable each successive night as drier air works into the area. Light N winds.
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&& .MARINE...
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Tropical Storm Warning remains in effect for the ocean zones. This should be able to be cancelled sometime tonight. A Gale Warning remains in effect through this evening for Lower Delaware Bay, and a Small Craft Advisory continues for Upper Delaware Bay. Strong wind field from Hurricane Jose extends to our coastal area despite its center at least a few hundred miles off the East Coast. This wind field will weaken from south to north through tonight, therefore headline changes will be needed. The strongest winds, to 30 knots, Wednesday should be over our northern coastal waters however these will diminish through the day. The seas will take some time to subside. Outlook... Wednesday night through Sunday...Seas in our coastal waters will slowly subside in wake of Jose Wednesday night and Thursday. Seas may briefly drop below SCA levels of 5 ft on Thursday. Thereafter, seas should start to increase again to 5-7 ft Friday into the weekend with Jose meandering offshore and then with long-period swells from Hurricane Maria gradually propagating up the eastern seaboard this weekend. Winds vary between N-NW and N-NE and remain below 25 kt thru the outlook period. Rip Currents... Hurricane Jose continues to push powerful swells into the coasts of Delaware and New Jersey through tonight. As a result, there is a High Risk of dangerous rip currents and heavy surf. Significant beach erosion, localized dune overwash and minor damage to piers have been reported today. It will take some time for these large waves/swells to subside and despite the surface wind more northwesterly on Wednesday, conditions look to warrant another High Risk. This will be re- evaluated later this evening. The High Surf Advisory has been extended through late this evening as 8-10 foot breaking waves reach the coast. Jose is expected to stall well offshore through the end of the week and into the weekend. Long-period swells will enhance the risk for the development of dangerous rip currents during this time. The risk may drop to moderate for Thursday-Friday with waves subsiding a bit and winds becoming light. However, long- period swells from Hurricane Maria may arrive this weekend, which could raise the risk to high again.
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&& .TIDES/COASTAL FLOODING...
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The Coastal Flood Warning remains in effect for the upcoming high tide cycle this evening along the NJ and DE coast and along the DE Bay. A Coastal Flood Advisory remains in effect tonight for New Castle County and Salem County. Things to monitor for this evening: The ETSS has had the best performance thus far with this morning`s high tide and with the current low tide this afternoon. This model brings Philadelphia close to minor threshold for tidal flooding, close to moderate for Reedy Point, and close to major for Lewes. We may need to upgrade to a warning for New Castle County and Salem County for tonight but will wait to see how water levels respond at low tide (i.e., if water is able to drain out the bay) around 6 PM. Minor tidal flooding will likely linger into Wednesday and perhaps into Thursday.
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&& .EQUIPMENT... KSMQ observations are not being sent out. There is a comms problem and technicians are on site this afternoon to troubleshoot. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...Coastal Flood Warning until 1 AM EDT Wednesday for NJZ012>014- 020>027. High Surf Advisory until 10 PM EDT this evening for NJZ014- 024>026. Coastal Flood Advisory from 9 PM this evening to 1 AM EDT Wednesday for NJZ016. DE...Coastal Flood Warning until 1 AM EDT Wednesday for DEZ002>004. High Surf Advisory until 10 PM EDT this evening for DEZ004. Coastal Flood Advisory from 9 PM this evening to 1 AM EDT Wednesday for DEZ001. MD...None. MARINE...Tropical Storm Warning for ANZ450>455. Small Craft Advisory until 6 AM EDT Wednesday for ANZ430. Gale Warning until 11 PM EDT this evening for ANZ431.
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&& $$ Synopsis...Klein Near Term...Gorse Short Term...Gorse Long Term...Klein Aviation...Gorse/Klein Marine...Gorse/Klein Tides/Coastal Flooding...Klein Equipment...Staff

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