Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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237 FXUS61 KPHI 261322 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 922 AM EDT Wed Jul 26 2017 .SYNOPSIS... High pressure across New York and New England today will move off into the North Atlantic tonight. Low pressure across the lower Ohio Valley will begin to strengthen Thursday and cause a warm front to approach the area. This front and the low moving along it will affect our weather from Thursday night into Saturday. The low will move away by Saturday night allowing high pressure to build back over the area for Sunday and into next week. A cold front may cross the area later Tuesday or Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Band of showers across Kent county, DE lightening up and tapering off. There may be a few light showers across parts of NJ this morning, but otherwise, most of the precip is drying up. Latest VIS satellite images showing clearing working its way south through much of northeast NJ, but it still remains to be seen how far south that clearing line will be able to go. There may be some breaks in the stratus by midday, but clouds should increase once again as stronger daytime mixing leads to development of stratocu. Today is expected to be the second day in a row of temperatures in the 70s for most of the forecast area. A better opportunity for 80 degrees is northern NJ (I-78, north and east of I-287 where there is less of a marine influence and where more sunshine is expected) and in far western zones of the CWA (Reading, PA down into the eastern shore of MD).
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... High pressure centered off the New England will ridge southwestward and just off the northern Mid-Atlantic coastline tonight. Light southerly flow around the high will develop over the region. Expect most of the region to remain dry tonight though an isolated shower cannot be ruled out before sunset this evening. Additionally, WAA in the low-levels will yield increasing clouds overnight. Some of the model guidance (e.g., NAM Nest) indicates strong enough isentropic lift to yield a few showers early Thursday morning west of the Fall Line. Confined slight chance PoPs to NE PA for now. Forecast low temperatures are in the low to mid 60s area-wide. The setup for radiational fog looks to be most favorable in the coastal plain, where the arrival of thicker cloud cover may hold off until daybreak Thursday morning. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The rather benign weather from Wednesday will spill over into Thursday as high pressure moves offshore. The return flow around the high will cause moisture to increase over the region. Accordingly, we will have a partly sunny becoming mostly cloudy fcst. Pops will increase through the day from W to E with slgt chc pops for the N/W looking OK for the morning and the further S/E with chc pops for the afternoon. There will be enough instability for tstms and the SPC has indicated a slgt chc for severe storms for later Thu and Thu night. Pops Thu night will rise to likely/categorical as the warm front nears the area. Friday through Saturday morning will feature another round of showers and thunderstorms with more heavy rains expected. Most of the operational models and the ensembles show 2 to 4 inches of rain over parts of the CWA. There is still plenty of variability on timing and location will have to be sorted out over the next few cycles, but its expected that some Flood or Flash Flood Watch products will be needed. The ground is still wet from the rains earlier this week. Improving conditions will take hold across most areas Saturday afternoon as high pressure from the N/W begins to build over the area. A couple lingering showers over Delmarva and SE NJ are possible though. Temperatures Saturday will be seasonably cool with highs in the low 80s S/E and mid to upper 70s N/W. Fair weather is expected much of the Sunday through Tuesday period as high pressure affects the area. Temperatures will return to near normal readings by then as sunshine should be more abundant over the region. The next system, a cold front, may bring some showers to the area Tue afternoon, but confid in this is rather low attm. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. CIGs may briefly improve to VFR at some locations by 15Z before stratocu yields MVFR CIGs in the the 1500-3000 ft range early this afternoon. Despite broken cloud cover for most of the day, expect TAF sites to improve to VFR with CIGs above 3000 ft between about 17Z and 20Z. VFR this evening. There is considerable uncertainty with the CIG and VSBY forecast for overnight tonight. Some of the guidance shows low clouds and MVFR or even IFR CIGs developing from west to east between 06-12Z Thursday. However, there could also be visibility restrictions in patchy fog during this time, especially at the fog- prone terminals. A light E to NE wind around 5 kt this morning will veer out of the SE 5-10 kt this afternoon and then S tonight. OUTLOOK... Thu...VFR. Increasing clouds. Thu Night thru Sat Morning...Frequent MVFR/IFR with showers/tstms. Sat Afternoon thru Sunday...Mostly VFR.
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&& .MARINE...
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Winds and seas will remain below SCA thresholds today and tonight. Seas are around 3 to 4 feet on the ocean with onshore winds around 10 to 15 knots. OUTLOOK... Thu thru Friday...Mostly sub-SCA conditions. Tstms with locally gusty winds and higher seas Thu night thru Fri night. Sat thru Sun...SCA seas on the ocean expected. Seas diminishing Sun night. RIP CURRENTS... Based on in-house regression guidance, the forecast calls for a low risk for the formation of dangerous rip currents today. However, with a residual onshore flow around 10 mph and waves in the surf zone around 3 ft, the risk may approach moderate for the NJ beaches later this morning.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...O`Hara Near Term...Klein/MPS Short Term...Klein Long Term...O`Hara Aviation...Klein/O`Hara Marine...Klein/O`Hara Tides/Coastal Flooding...

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