Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 250146 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 946 PM EDT WED AUG 24 2016 .SYNOPSIS... High pressure offshore will continue to move east through Friday. Low pressure will move across Canada and send a weak cold front across the mid Atlantic states late Friday. Another high pressure system will build in for the weekend. Low pressure will move through Canada early next week and another front may affect our weather next Monday and Tuesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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930 PM ESTF: minor adjustments to temp trends through the night and no big changes. Surface high pressure continues to push offshore tonight. Meanwhile, a weak cold front over the Midwest will move into the Great Lakes. Mainly warm and quiet for the local area tonight, but there may be some convective cloud debris from the storms upstream passing overhead very late at night. Dewpoints are up from 24 hours ago. With S to SW flow persisting through the overnight hours, low level humidity levels will continue to creep up. UPS cross over tool gave spotty fog to parts of countryside NJ and ne PA. Temperatures should be around 2 degrees above normal.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
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Low pressure over Canada will continue to drag a cold front through the OH Valley and towards the local region on Thursday. Surface high pressure off the Mid-Atlantic coast continues to push offshore, but upper level ridging will hold firm over the area with the approach of that front. The front almost appears to wash out as it moves into the region late in the afternoon. Best forcing remains to the N and W. The upper ridging should keep precip from developing across most of the area, but will carry slight chance POPs, and cannot rule out a rumble of thunder or 2 into eastern PA. Southerly flow continues to usher a warmer and more humid airmass into the region on Thursday. Southwest wind may gust 20 mph during the afternoon. Temps may nudge 90 in PHL and in general max temps should be around 6 degrees above normal.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Mostly good weather for the longer range part of the forecast. A cold front will cross the area Thursday night and Friday, but the front is weakening and the showers and few tstms that accompany it will not be anything out of the ordinary for the summer. High pressure will bring nice weather for the weekend. Another low pressure system and cold front will move through for early next week. Again, more sct showers and tstms will affect our weather then. Calendar day average temperatures for the long range will be above normal with averages Friday about 10 degrees above normal, then 5 to 9 degrees above normal daily thereafter through Wednesday. Highs will be in the upper 80s to low 90s across the urban areas and Delmarva. Highs across the Nrn NJ and srn Poconos areas will be in the 80s. The warmest and most uncomfortable conditions will be on Friday. The dew points and temperatures on Friday may bring heat index values into the upper 90s or even 100 across the urban areas. && .AVIATION /02Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Remainder of tonight...VFR. Light southerly winds. Local MVFR visibility is possible toward daybreak Thursday due to light fog, mainly at RDG, ABE and MIV but not yet in the TAF. Thursday...VFR. Isolated SHRA possible which could temporarily lower conditions. South to southwest winds increase to 5-10 KT with gusts near 20 kt in the afternoon. Outlook... Thu Night thru Monday...Mostly VFR conditions expected. Sct tstms Thu night and Fri may bring short period of lower cigs/vsbys.
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&& .MARINE...
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No marine headlines through Thursday. A 1 foot 12-13 second ese swell is becoming more evident. It may increase to 2 feet Thursday? Still...not a marine hazard. High pressure off the Mid-Atlantic coast continues to move offshore tonight through Thursday. A cold front approaches from the west on Thursday. S winds will range from 5-10 KT tonight with gusts 15-20 kt probably diminishing late, then will increase to 10-15 KT during the day Thursday. Cannot rule out a few gusts to 25 KT late Thursday for northern NJ ocean zones, but will hold off on issuing a SCA at this time. Outlook... Thursday night through Monday...Sub-sca conditions are expected. Close to SCA gusts may occur on the northern NJ waters Thu night and early fri. Sct tstms Thu night/Fri and again early next week. For Thursday...The risk for the formation of dangerous rip currents is low enhanced except moderate for Ocean and Monmouth counties, especially late afternoon when the southerly wind increases to 15 kt and the tide is moving into the lower half of the tide cycle. Confidence on moderate risk occurrence and extent is below average. If a 2 ft 10-12 second swell does not materialize the risk will lessen. No matter: Swim in the presence of lifeguards. About 55% of the rip current fatalities in our waters since 1998 have been after the beach patrols go home, or between roughly 530 and 730 PM. August is our more fatal month...95% were men and 50 percent between 18 and 35 years of age. 60 percent occur with maximum temps above 85 at philadelphia, over 60 percent died with water temps above 70. Friday and Saturday are outlooking low enhanced risk. Then this coming Sunday-Wednesday...model ensemble guidance on every successive cycle continues to send 2-4 ft long period (15 to 17 second) east southeast swell into our waters from the central Atlantic - Gaston. It could be even higher but we`re taking the conservative approach at this time from this distant offshore hurricane. This is all dependent on size, strength and track but there is little doubt that swells will build here...just how much is the question. Swimming and wading dangers will probably increase. For now we`re anticipating a moderate or greater risk for Monday- Wednesday and possibly starting Sunday.
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&& .CLIMATE... There is some potential for a heat wave beginning Thursday or more likely Friday. 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. Odds still favor the monthly average rising beyond the currently projected 80.8 as the 12z/24 ECMWF is 1-2 degrees warmer than the 12z/24 GFS Saturday- Tuesday. Model mid level heights (500mb) are 1 to 2 SD above normal through most of this period. The ridge weakens toward Sept 2-3 then impressively warms again by Sept 7. Philadelphia August ranking includes our 330 PM forecast temps (SFT specific values) through the 31st. The 30 year normal is 76.6 Records date back to 1874. 1. 80.8 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. Foresee 3 to 5 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 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. 76.8 2016 3. 76.0 1937 4. 75.7 1955 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. 78.2 2016 2. 77.9 2005 3. 77.1 2009 4. 77.0 1984 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. 78.8 2016 3. 78.6 1995 4. 78.3 1994 Allentown seasonal avg is projecting 74.9 or a ranking of around #2 in the por. 1 75.3 1949 2 74.9 2016 3 74.6 2005 and 1980 4 74.3 1943 and 1937 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 30 17 9 4 16-1980 41-1966 acy 26 10 9 3 11-2010 46-2010 phl 35 21 11 5 17-1995 55-2010 ilg 30 20 11 5 23-1895 59-1895 All the data including the forecast will be rechecked for the 330 am Saturday AFD. In the meantime, this part of the climate section will probably be discarded around 330 am Thursday. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Drag/O`Hara 945 Near Term...Drag/MPS 945 Short Term...MPS Long Term...O`Hara Aviation...Drag/MPS/O`Hara 945 Marine...Drag/MPS/O`Hara 945 Climate...945

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