Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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953 FXUS61 KPHI 230148 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 948 PM EDT MON AUG 22 2016 .SYNOPSIS... High pressure will pass over our region on Tuesday before moving off the coast and drifting out to sea. A cold front approaching from the northwest is expected to arrive on Friday. Another area of high pressure is anticipated to build from the Great Lakes to New England and southeastern Canada over the weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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930PM ESTF: little change from the 630 PM lowered min temps in the countryside because of developing ideal overnight radiational cooling. GFS 2m temps argue strongly for upper 40s nw NJ and ne PA. Low temp fcst below and the last time it was this cool. Aug 23 Forecast 63 PHL would be the coolest since the 59 June 18th Aug 23 forecast 52 ABE would be the coolest since the 50 June 15th Aug 23 forecast 55 ACY would be the coolest since the 55 June 27th Aug 23 forecast 57 ILG would be the coolest since the 57 June 18th
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
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The fine weather continue Tuesday. This high will crest over the area during the morning and begin to slide east. Skies will be mostly sunny and it will be another dry and comfortable day. High temperatures will reach the low/mid 80s in most spots. Winds will turn NE to E by afternoon...but speeds will be less than 10 mph overall.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Dominant features through the long term are two large high pressure systems, leading to a continued mostly tranquil weather pattern. Wednesday night through Thursday...Surface high shifts off shore. The biggest impact of this will be to bring a shift to weak low level onshore flow. Meanwhile, in the mid and upper levels, a broad ridge builds over the southeastern U.S., which could slow the progress of the cold front (over the Great Lakes region at this time). Thursday night and Friday...Cold front continues slow progress east, though little, if any precipitation is expected primarily because of synoptic scale subsidence thanks to the persistent broad ridge over the southeastern U.S.. The front should arrive on Friday. With models depicting considerable pressure rises behind the front (thanks to a high building south out of central Canada), expect that the front should make steady progress through the region without stalling. Saturday and Sunday...the region will once again be mostly under the influence of a High pressure system, resulting in mostly tranquil weather. However, the center of the high will stay well north of the region. As a result, we expect temperatures will remain above normal through this period. Monday...An upper level short wave trough could dig southeast towards our region through this time, bringing another small chance for precipitation. Given the uncertainty with how far out it is, kept the chance for precipitation no higher than 20 percent. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Great flying weather is expected through Tuesday with high pressure building in. The daytime cu across the area will diminish by sunset and the winds will become light by then too. Clear skies and light winds will be over the area tonight and early Tue. Winds will be variable Tue, but may show a tendency to go NE or E by afternoon. Outlook... Wednesday through Thursday...VFR conditions expected. Thursday night and Friday...mostly VFR conditions expected though there is a slight chance (20 percent) of thunderstorms across the Delaware Valley and Lehigh Valley (including KRDG, KABE, KTTN, KPNE, and KPHL). Saturday...VFR conditions expected. && .MARINE...
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No marine headlines through Tuesday. Transfer of wind may be starting to come into play as the boundary layer temp cools below the sst, increasing low lvl instability time Tuesday morning. Winds will remain mostly NW this evening and then veer to N late. On Tuesday, winds will further veer to NE during the morning. Winds speeds later tonight and Tuesday will mostly be around 10 knots with gustiness diminishing tonight. Outlook... Wednesday through Saturday...winds and seas should stay below SCA criteria. RIP CURRENTS: Tomorrow-Tuesday is definitely a low ENHANCED day that may need an upgrade to moderate risk along our entire NJ coast in our 530 am issuance Tuesday. Have facebooked concern. It appears that a 1 ft 12-13 second period swell will become dominant tomorrow and during the afternoon winds will be turning onshore enhancing the risk for the formation of dangerous rip currents. It is very important that everyone swim in designated beach patrol watched areas. The benign looking swell (1ft easterly 12-13 second) at both 44065 and BTHD1 has lots of energy and can result in wave knock down and associated rip current formation. Wednesday: ditto Tues of Low ENHANCED or possibly Moderate for NJ. Thursday, Friday: Probably low ENHANCED, maybe slightly less chance of moderate risk due to a southerly flow but even that could be enhanced during the afternoon because of inland heating. Developing later this coming weekend? some of our guidance is showing a 2 ft 15 to 17 second period southeast swell rolling into our waters. IF that occurs and the flow is onshore...we might be issuing our first high risk headline of the season. We just are not sure if the GFS ensembled and ECMWF supported central Atlantic developments will occur. Water temperatures: Upwelling cool water in the 2246z satellite imagery and water temps vcnty the entrance to De Bay and up to at least ACY (upper 60s). Otherwise a few miles offshore much warmer than normal.
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&& .CLIMATE...
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A top 6 warmest August appears assured most of our forecast area and a top 4 warmest June-July-August for Philadelphia, Allentown and possibly Atlantic City. Philadelphia August normal temp 76.6. The forecast seems to be settling in close to 80F. Odds favor the 80.2F we project now as conservative or at least 3.6 above normal. In any case...Philadelphia ranking includes our 330 PM forecast temps (SFT specific values) through the 29th and the FTPRHA GFS 2m max/min for PHL for the 30th-31st. The average of 81.9 through the 21st will cool 1 to 2 degrees. Records date back to 1874. 1. 80.2 2016 2. 79.9 1980 3. 79.8 2001 and 1995 4. 79.6 2005 5. 79.5 2002 Regarding whether August can tie its record of 17 90F days. Its possible but not probable. Can foresee 3 to 6 more 90 degree days to add onto the 11 we have so far this month. The record of 17 was set in 1995. The mean for the month is only 5. Allentown will probably rank #2 and #3 warmest August. Through the 21st 77.9 but we`ll lose 1-2 degrees by the end of the month. Records date back to 1922. Normal 71.7 projecting a positive departure of 4.5 degrees. Rank 1. 78.2 1980 2. 76.2 2016 3. 76.0 1937 4. 75.7 75.7 Atlantic City through the 21st has averaged 79.5 but may lose up to 2 degrees by the end of the month. Records date back to 1874. The August monthly normal is 74.4 and we`re projecting a positive departure of 3.5 degrees. 1. 77.9 2016 and 2005 2. 77.1 2009 3. 77.0 1984 4. 76.9 2010 Wilmington Delaware through the 21st has averaged 80.3 but will lose 1 to 2 degrees. Records date back to 1894. The monthly normal is 75.2 and we`re projecting a positive departure of 3.6 degrees. The Wilmington records appear biased on the warm side during the early stages of this period of record. Even so, Wilmington would probably be 6th or 7th warmest in the period of record for the month of August. 1. 86.6 1900 2. 83.8 1898 3. 82.4 1901 4. 81.5 1899 5. 80.8 1897 6. 78.8 2016 and 1895 7. 78.7 1902 Seasonal: This summer 2016 for Philadelphia will probably be the 2nd or 3rd warmest June-July-August (JJA) in the period of record dating back to 1874. 1. 79.6 2010 2. 78.6 1995 3. 78.5 2016 4. 78.3 1994 5. 78.2 1993 Allentown seasonal avg is projecting 74.8 or a ranking of around #2 in the por. rank 1 75.3 1949 2 74.8 2016 3 74.6 2005 and 1980 4 74.3 1943 and 1937 Atlantic City seasonal average is projecting 75.7..4th warmest in the por. 1. 77.5 2010 2. 77.0 2011 3. 75.9 2005 4. 75.7 2016 5. 75.5 2008 6. 75.3 1984
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Iovino/Johnson Near Term...Drag/O`Hara 947 Short Term...O`Hara Long Term...Johnson Aviation...Drag/Johnson/O`Hara Marine...Drag/Johnson/O`Hara 947 Climate...Drag 947

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