Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 201442 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1042 AM EDT Thu Oct 20 2016 .SYNOPSIS... A front which settled south of the region wednesday night will push back across our area today. Low pressure will strengthen across the Ohio Valley and move north of the area tonight and Friday. A strong front associated with the low will cross the region Friday evening. Eventually, strong low pressure will be across New England this weekend and it will remain there into early next week. High pressure will build across our area into the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure remains centered over Maine as a broad area of low pressure develops and strengthens over the OH/TN Valleys. A stationary front remains along the Mid-Atlantic, and as the low tracks to the north, that front will lift through the region as a warm front. Due to the influence of the high, an E-NE flow remains over the CWA. For coastal and southern portions, and onshore flow is resulting in an airmass with surface dewpoints in the low to mid 60s. For the rest of the CWA, however, that flow is ushering a dry airmass from the north as surface dewpoints are in the upper 40s to mid 50s. As a result of the dry air over much of the area, precip is having a hard time developing. Current RADAR showing an area of showers and thunderstorms over central and eastern PA, just west of the PHI CWA boundary, lifting to the north. Only a few showers have been able to develop over the Lehigh Valley and Pocono Mountains this morning due to that dry air. It will take some time for the dewpoints to increase enough to support more widespread shower activity, probably not until this afternoon. Until then, can continue to expect widely scattered, light showers. Will carry low end chance PoPs, increasing to high end chance this afternoon for the Lehigh Valley, Pocono Mountains, and northern NJ. For the rest of the CWA, that warm front will continue to lift to the north, but there is not much upper level support for showers. In addition, surface moisture, with the exception of coastal and extreme southern areas, is marginal, at best. Therefore, will carry a dry forecast for most of the southern half of the CWA, with slight chance PoPs for the central portions. For temps, not making too many changes to the previous forecast. Clouds, showers, and evaporative cooling, mainly this morning, will keep temps from rising out of the low to mid 60s to the north of I-80. For the rest of the region, temps will warm well into the 70s, and into the low 80s across MD/DE. Record high temperatures are likely across southern areas. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... Low pressure will continue to deepen as it moves northeastward from the Ohio Valley to central PA tonight. Boundary layer winds are forecast to strengthen sufficiently to progress the warm front northward through eastern PA and NJ tonight. North of the front across northeastern PA and northern NJ, pockets of drizzle and fog are expected. Lows range from the mid 50s north of I-80 to the mid 60s south of the PA Turnpike/I-195. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Friday/Friday night...Low pressure and a strong front will cross the region. Most of the models are not bringing too much precip to the area, despite the strength of the systems moving through. The low pressure system offshore will be bringing in more moisture from the east, but much of it arrives too late to be acted upon by the cold front. The system gets more organized north of the area, and the higher rainfall totals will be there. The last of the rather mild air will be swept away Fri evening with temps dropping back to normal or slightly below normal values. Lows Fri night will be in the low 40s north and mid/upper 40s south. Winds will increase overnight with gusts 20-30 mph at times. Sat thru Sun...Decreasing chc for showers Sat morning across the area as the strong to the north moves away. Low chc pops will be across the nrn and central areas Sat morning...decreasing back to slgt chc by afternoon. It will be windy and cool Sat with highs only the the upper 40s/low 50s north/west and mid/upper 50s over Delmarva and srn NJ. Winds NW 15-25 mph with gusts near 40 mph possible. We may to eventually consider wind related headlines if speeds trend any higher. Winds diminish by Sunday. Sun night/Mon...A weak upper system and sfc front may bring a few sct showers across the far north. These system will also bring a reinforcing shot of cooler air and gusty conditions Sun night and Monday. The airmass looks rather dry attm, so we will hold on mentioning any pops attm. This could be updated as the time gets closer. Mon night thru Wednesday...A mostly dry period with seasonable temperatures. High pressure from the Midwest will build over the area and reach the region Wed evening. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Mainly a VFR forecast this morning with lower clouds around 4-5 kft AGL expanding from SW to NE across the area. An area of light showers may develop in VC of RDG-ABE through 16Z, with CIGs lowering to around 1500-2500 ft once precip falls. Model guidance then shows an expansion of low clouds to the southeast toward the I-95 terminals between 15-18Z. The onset of MVFR CIGs may be a bit too quick as models have under-predicted the strength of the near- surface dry air thus far. Eventually this afternoon, terminals should experience at least temporary periods of MVFR. Low clouds are likely to become more widespread after dark tonight. CIGs may lower to below 1000 ft. The best chance for IFR CIGs appears to be across the northern terminals. Stat guidance is also indicating widespread fog with VSBYs less then 1 SM at many of the terminals. This may be overdone with cloud cover already in place. There could be a more localized region of fog maybe along and north of a warm front but it is too uncertain to pinpoint which terminals would be affected. NE winds 5-10 kt early this morning will become E by this afternoon and then S-SE late this evening and overnight after the warm front passes thru. OUTLOOK... Fri/Fri night...Showers likely with restrictions to MVFR expected. IFR conditions possible. Gusty winds developing Fri night. Sat through Sun...Some MVFR psbl erly Sat, especially n, then mainly VFR. NW winds with 25-35 KT gusts psbl. Mon...VFR. && .MARINE... No marine headlines are expected for today. NE winds 5-15 kt this morning will veer out of the east and then SE over the course of the day and into tonight. Seas in our coastal waters will generally be in the 2-3 ft range. OUTLOOK... Fri...Mostly sub-sca, but winds and seas begin to increase late. Sct showers. Fri night thru Sun...A Gale Watch has been issued. Strong gusts and rough seas thru the period. Sct showers fri night and Sat morning. Sun night thru Tue...SCA conditions expected. Isolated showers possible across the nrn NJ coastal waters Sun night. && .TIDES/COASTAL FLOODING...
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Tide levels may come close to touching minor coastal flooding thresholds at high tide late this morning and early this afternoon. Latest guidance has Lewes, DE, and Sandy Hook, NJ just touching minor coastal flooding benchmarks. Although a Coastal Flood Advisory will not be issued, there may be some spotty minor tidal flooding. Guidance is also indicating the potential for minor tidal flooding around high tide early Friday afternoon.
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&& .CLIMATE... The following sites tied or set daily record high temperatures yesterday (Wednesday, 10/19) New RecordOld Record Allentown, PA 84 82 (1963) Trenton, NJ 86 83 (1963) Philadelphia, PA 86 80 (1947) Atlantic City, NJ 86 80 (1991) Wilmington, DE 87 81 (1963)* record tied Georgetown, DE8681 (1953) Warmth of this magnitude seen the past few days is a rare occurrence for this late in the year: For Allentown, the only other year that recorded a high temperature of at least 85 degrees this late in the calendar year was 1947. In 1947, the high was 85 degrees on the 21st and 23rd of October. Climate records at Allentown go back to 1922. Here are the record high temperatures for today (10/20). THU OCT 20 Mount Pocono, PA 75 in 1963 Reading, PA 80 in 1947/1953/1969 Allentown, PA 78 in 1936 Trenton, NJ 80 in 1969 Philadelphia, PA 80 in 1916/1938 Atlantic City, NJ 85 in 1987 Wilmington, DE 82 in 1969 Georgetown, DE 83 in 1953 Monthly average temperatures are projecting 3 degrees or so above normal, which would rank in the top 15 warmest Octobers at Philadelphia and Allentown. This is stated with the usual mid month uncertainty. What we do know is that the warmth of this week will virtually lock in an above normal month, especially since the pattern for the last week of October does not indicate any lengthy period of below normal temperatures. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Watch from Friday evening through Saturday afternoon for ANZ430-431-450>455. && $$ Synopsis...O`Hara Near Term...Klein/MPS Short Term...Klein Long Term...O`Hara Aviation...Klein/MPS/O`Hara Marine...Klein/MPS/O`Hara Tides/Coastal Flooding... Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.