Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 191614 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1214 PM EDT Wed Oct 19 2016 .SYNOPSIS... High pressure will remain over the Southeast coast before moving into the western Atlantic waters by the end of the week. Meanwhile, a weak cold front will move southward through the region today and tonight, before returning to the north as a warm front on Thursday. Low pressure developing over the Ohio Valley will pass to the north on Friday, dragging a strong cold front through the region. High pressure then builds in from the south as low pressure deepens to our north over the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Cold front continues to slowly work its way through eastern PA, and is just pushing into NW NJ. Not sure how much forward progress it will make during the day, but there is not precip with it, so the forecast remains dry. Most of the SCT-BKN mid and high clouds are across S NJ and into DE, with some SCT lower clouds moving into E PA and NW NJ. As a result, temps are warming up quite nicely across the region with temps generally running in the upper 70s to low 80s for much of the CWA, and in the low 70s in the Pocono Mountains. Think highs may end up a couple of degrees warmer than forecast, so will go ahead and bump up highs, and daily record high temperatures will likely be tied or broken at many of our climate sites this afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... The west-east oriented cold front will drift southward through the Delaware Bay and lower Delmarva regions this evening. The surface boundary may then stall or even start to return back northward late tonight. Meanwhile, a wave of low pressure is forecast to organize over Mid South and Ohio River Valley tonight. Isentropic lift in the H9-H7 layer will ensue as the flow to the east of this developing wave backs out of the south. There is still some discrepancies between models regarding how quickly overrunning precipitation develops in the vicinity of the front. We anticipate at a band of light rain to develop by early Thursday morning somewhere between ILG and ABE but PoPs were kept low due to forecast uncertainty. Forecast low temperatures range from the lower 50s in northeastern PA-northwestern NJ (since cloud cover will arrive late in the period) to the mid 60s from about the Philly metro southward (where clouds will arrive much earlier in the night). Surface winds will veer from north to northeast tonight as high pressure builds southward from New England. Wind speeds will be 10 mph or less. && .LONG TERM /THURSDAY THROUGH TUESDAY/... A cold front and low pressure across the Ohio Valley and a storm offshore will eventually merge and become a strong system north of our area this weekend. Clouds and shower chcs will increase from Thu thru friday night. A strong cold front will cross the area Fri night with showers likely. Above normal temperatures will continue Thu and (to a lesser extent) Fri. Once the cold front crosses the area, readings will turn sharply colder. Showery weather with cool temperatures is expected Sat with decreasing chc for showers Sat night and Sunday. The models are at odds with how much moisture circulates across our region. The ECMWF has more showers Sat across our area than its previous runs while the GFS is notably drier. We will continue with mostly chc or slgt chc for showers attm. Highs Sat and Sun will be in the upper 50s north and low 60s elsewhere. These temperatures will be several degrees below normal. Mon and Tue will feature dry weather with cooler than normal temperatures as high pressure builds across the area. Highs will again be mostly in the 50s up north and low/mid 60s over srn NJ and Delmarva. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR forecast on tap for today with mid-level clouds passing through. Winds 5-10 kt will veer out of the W mid to late morning and then NW during the afternoon as a cold front progress southward thru the region. Lower clouds are expected to develop first over the southern terminals (ILG-MIV-ACY) this evening and then expand northward late tonight. CIGs will most likely be between 3500-5000 ft AGL. However, cannot rule out MVFR restrictions early Thursday morning if CIGs lower a bit more than forecast, especially if rain develops. OUTLOOK... Thursday through Friday night...Showers developing on Thursday, becoming more widespread into Friday, tapering off Friday night. MVFR conditions likely, with the chance for IFR and lower. Saturday through Sunday...Mainly VFR. NW winds with 25-35 KT gusts possible. && .MARINE... Sub-SCA conditions on tap for the rest of the day. A cold front will move southward through the waters tonight. SW winds ahead of the front will become NW and then NE with speeds under 20 kt. OUTLOOK... Wednesday through Friday afternoon...Forecast winds and seas below SCA criteria. Scattered showers Thu thru Friday. Friday night through Sunday...A strong cold front passes across the waters Friday night. Tight pressure gradient develops over the weekend with winds gusting to at least 30 KT with the potential for gale force wind gusts. Sunday night...Winds and seas will drop back below SCA criteria. && .TIDES/COASTAL FLOODING... Observed tidal anomalies are around two-thirds of foot above astronomical normal early this morning. The ETSS guidance predicts Cape May to reach minor tidal flooding threshold of 6.7 ft with the upcoming morning high tide. Although this is below our threshold to issue a Coastal Flood Advisory, spotty minor tidal flooding may occur later this morning. The same ETSS guidance indicates the potential for several of the forecast sites along the oceanfront and lower Delaware Bay to come within a tenth of a foot of minor Thursday morning. && .CLIMATE... The following sites tied or set daily record high temperatures yesterday (Tuesday, 10/18) New RecordOld Record Allentown, PA8581 (1963) Reading, PA8585 (1908) *record tied Georgetown, DE8481 (1996) Wilmington, DE8381 (1938) Trenton, NJ8382 (1908) Warmth of this magnitude seen yesterday (and potentially again today) was/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. For Philadelphia, yesterday (10/18) marked the latest occurrence in a calendar year with a high of 84 degrees or warmer since 1950 (it was 84 degrees on November 11, 1950). Here are the record high temperatures for today (10/19)...and across southern portions of the area on Thursday (10/20). WED OCT 19 THU OCT 20 Mount Pocono, PA 80 in 1963 75 in 1963 Reading, PA 84 in 1963 80 in 1947/1953/1969 Allentown, PA 82 in 1963 78 in 1936 Trenton, NJ 83 in 1963 80 in 1969 Philadelphia, PA 80 in 1947 80 in 1916/1938 Atlantic City, NJ 80 in 1991 85 in 1987 Wilmington, DE 81 in 1963 82 in 1969 Georgetown, DE 81 in 1953 83 in 1953 Thursday is dependent on sunshine. For now, no daily record highs are forecast but this could change in future forecasts. We`ve left the records in this section since it could be with a few degrees of the record at a few locations, especially south of Philly. 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...None. && $$ 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.