Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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840 FXUS61 KPHI 270917 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 517 AM EDT SAT AUG 27 2016 .SYNOPSIS... High pressure in southeast Canada is ridged down into the mid Atlantic states this weekend, then shifts offshore next week. A very weak frontal boundary from the northwest may arrive early in the new week. A strengthening cold front approaching from the northwest is anticipated to cross our area early on Thursday. Great Lakes high pressure builds toward the mid Atlantic coast for Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure will settle across the area today with fair weather expected. It will remain warmer than normal, like Friday, with highs in the upper 80s to low 90s. The humidity levels will be a little lower than Friday, so although it will be warm/hot, it shouldn`t be unbearable to be outside today. Winds will be mostly NE or E at around 10 mph. This will keep temperatures along the shore and inland a bit cooler. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... More fair weather tonight as the High continues to move away far N/NE. Skies will remain mostly clr and winds will be light. Low temperatures will be mostly in the 60s, with some 70 degree temps over the metro Philadelphia area. Lows across the srn Poconos will be closer to 60 degrees, so overall, temperatures will be about 5 degrees above normal. && .LONG TERM /SUNDAY THROUGH FRIDAY/... **a basically dry 6 day period with a possible modest 6 day heat wave parts of the I-95 corridor and RDG-ABE** 500 MB: +2 standard deviation ridge overhead to start this 6 day period progressively weakens during the middle and end of the week as a trough develops across the ne USA with ridging to return eastward Labor Day weekend. Temperatures: A top 4 warmest August and summer (June-July-August) will come to close with calendar day average temperatures Sunday- Wednesday 6 to 10 degrees above normal, then cooling Thursday to maybe 2 to 5 above normal and finally normal just below on Friday. Forecast basis: Unless otherwise noted, a 50 50 blend of the 00z/27 GFS/NAM MOS guidance Sunday-Monday, thereafter the 00z/27 GFS MEX MOS for Monday night and 05z/27 WPC Guidance Tuesday-Friday. The 00z/27 GFS operational cycle was in sharp disagreement with the 00z/27 ECMWF, GGEM WPC and continuity Tuesday and Wednesday and therefore not applied. The dailies... Sunday-Wednesday...Clear to partly cloudy, very warm to hot during each afternoon. Light wind at night permits radiational cooling in the countryside. Lowered blended gfs/nam mos guidance temps in the non-urban areas Sunday night by 2F, especially since it hasnt rained since the 21st. Did not have time to consider that cooling adjustment For Monday night. Light onshore flow Sunday and Tuesday afternoon will cool the coasts but a 6 day heat wave is possible (Friday the 26th was the start if it happens) for some of the interior including Berks County into the Lehigh Valley and parts of the I-95 corridor. Confidence for a 6 day heat wave is average to slightly below average with a 1 day interruption in 90 degree warmth possible. Early morning haze and fog may eventually develop during mid week, especially Wednesday morning. For now its only a spotty prediction Monday and Tuesday. Late Wednesday afternoon into early Thursday...A developing cold front is expected to pass through our area and possibly trigger scattered thunderstorms. This appears to be our primary hope for any beneficial rain since the 21st. if we dont get it, it could be quite a few days before it rains. Thursday...turning cooler but still near or slight above normal with a gusty northwest wind developing. Friday...Could be delightful for late summer with very dry air=low humidity (dewpoints down close to 50). && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. A decent period of flying weather today and tonight with high pressure in control. Skies will be clear except for a few daytime cu this afternoon. Wind speeds will be 10 knots or less. The wind directions mostly North or Northeast this morning and then East or Southeast this afternoon. OUTLOOK... Sunday through Wednesday...VFR...mainly sct clouds aoa 5000 ft with brief broken cigs near 5000 or 6000 ft. Late night and early morning visibility restrictions are possible, especially Wednesday morning. Small chance of a passing shower or thunderstorm early Monday. Scattered Showers and thunderstorms are possible late Wednesday night with the approaching cold front. Winds: light southeast Sunday, light west to northwest Monday, light and variable Tuesday, then on Wednesday southwest gusting 15 kt in the afternoon before shifting northwest at night. && .MARINE... No significant weather today or tonight. Winds will veer from North early this morning to Northeast after sunrise. Wind speeds will increase to 10-15 knots by mid-morning. Winds will then continue to veer to East or a little Southeast tonight. Winds by tonight will have subsided back to less than 10 knots for the most part. Seas on the ocean will be 2 to 4 ft today and closer to 2 ft tonight. OUTLOOK... Sunday through Wednesday...No marine headlines are anticipated. Long period (12-15 second) 2 to 3 foot southeast swells from Gaston will be rolling ashore in the Atlantic waters Monday through Wednesday. Its possible these swells will briefly build to 4 feet Tuesday. RIP CURRENTS... A Moderate risk for enhanced rip currents is expected today. The swells from distant tropical systems have yet to arrive, but the beginnings of this may be late this afternoon and early tonight. Winds will be onshore today and will be 10-15 knots this morning. This will create some enhanced surf conditions. The swell will arrive late and may further create enhanced conditions. The long period swells from Tropical Cyclone Gaston should arrive Sunday as the cyclone nears 55 degrees west longitude. However, the long period 12 to 15 second swells are forecast to become more pronounced along the coasts of New Jersey and Delaware on Monday and Tuesday, even as Gaston makes its turn northeastward. Momentum in the swells reaching our coast due to the original westward motion of the tropical system should result in an enhanced threat for the development of dangerous rip currents for much of the week. Presuming these swells occur as outlined above, this will eventually impact beach behavior. Follow the advice of local lifeguards who will be observing and your safety net. This is not a time to swim on your own without lifeguard presence. Additionally waders are cautioned not to turn their backs to the waves when coming out of the water. Wave knock down can result in upper torso injury. && .CLIMATE... A top 5 warmest August appears assured most of our forecast area with record monthly warmth likely at PHL. A top 3 warmest June-July-August for Philadelphia, Allentown and possibly Atlantic City. Philadelphia is on its way for its warmest August on record (dating back to 1874). More than 4 degrees above normal. This Philadelphia August ranking includes our 330 AM forecast temps (SFT specific values) through the 31st. The 30 year normal is 76.6 Records date back to 1874. 1. ~81.0 2016 2. 79.9 1980 3. 79.8 2001 and 1995 Regarding whether August can tie its record of 17 90F days. Its possible but not probable. Foresee 3 to 5 more 90 degree days to add onto the 12 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 warmest August. Records date back to 1922. Normal is 71.7 and we are projecting a positive departure of at least 5 degrees. 1. 78.2 1980 2. 76.7 2016 3. 76.0 1937 Atlantic City records date back to 1874. The August monthly normal is 74.4 and we`re projecting a positive departure of nearly 4 degrees. As it stands, Atlantic City will rank #1 or #2 warmest August with very little chance of slipping to #3. 1. 78.0 2016 2. 77.9 2005 3. 77.1 2009 Seasonal: This summer 2016 for Philadelphia will probably be the 2nd warmest June-July-August (JJA) in the period of record dating back to 1874. 1. 79.6 2010 2. 78.9 2016 3. 78.6 1995 4. 78.3 1994 Allentown seasonal avg is projecting 75.0 or a ranking of around #2 in the por. 1 75.3 1949 2 75.0 2016 3 74.6 2005 and 1980 Atlantic City seasonal average is projecting 75.8...4th warmest in the por. 1. 77.5 2010 2. 77.0 2011 3. 75.9 2005 4. 75.8 2016 5. 75.5 2008 90 degree days season mean Aug Aug Aug Season mean rer rer abe 31 17 10 4 16-1980 41-1966 acy 27 10 10 3 11-2010 46-2010 phl 36 21 12 5 17-1995 55-2010 ilg 31 20 12 5 23-1895 59-1895 Decided not to post dry rainfall statistics due to uncertainty regarding shower amounts, if any Monday-Wednesday. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Drag Near Term...O`Hara Short Term...O`Hara Long Term...Drag Aviation...Drag/O`Hara Marine...Drag/O`Hara Climate...516a is the U.S. government's official web portal to all federal, state and local government web resources and services.