Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 171100 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 600 AM EST Tue Jan 17 2017 .SYNOPSIS...
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Low pressure is forecast to pass across the Great Lakes today with a secondary low developing near Long Island tonight. The system is anticipated to move out to sea on Wednesday. High pressure should follow for Wednesday night through Thursday night. Low pressure is forecast to move across the Ohio River Valley and the eastern Great Lakes on Friday with a secondary low developing off the Middle Atlantic coast on Friday night. High pressure is expected to build into our region from the north for the weekend. A broad area of low pressure is anticipated to approach from the southwest early next week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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600 AM: Confidence on Freezing rain advisory is still less than ideal except elevations where its 32F at 6am which was few and far between. Thinking that this is primarily an elevated ice event: bridges/overpasses/ trees and branches later this morning through tonight from northern Sussex County into northwest Monroe county. Yes there can be spotty elsewhere this morning but i dont see widespread icing, at least not at this 6am writing due to lack of organized qpf while wet bulbs near freezing. Still no icing groups at any metar sites (I group) in our area through 11z, which means, little if any icing, so far. We have messaged FB for any reports. The 06z/17 GFS/NAM keep primary measurable prior to 13z down on the Delmarva and s NJ. Wet bulbs still say icing possible in portions of the forecast area but as of this writing...am thinking only Monroe County Sussex County high terrain will have any substantive icing once rain begins in earnest between 15z-17z. Its a close call on all of this. Light winds. So, rain overspreads the entire area 15z-18z then may quit at times Delmarva late day or evening. A cold rain. Light wind trending northeast, north of I-78 as low pressure forms in central NJ late in the day while winds are southeast over the Delmarva trending south late in the day with max temps there late in the day. Basically blended the 0z/17 EC 2m temps with the 00z/17 MAV MOS temps. MET and MOS temps as well as 2m temps on the models are substantially too cold early this morning and not used prior to 12z). Forecast max temps several degrees above normal.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
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Cold rain and drizzle north of I-78 while s of I-78... periods of rain and drizzle diminish, especially Delmarva where there may be 9 hours of rainfree weather. Still a risk of glazing vcnty KMPO and High Point NJ but no advy extension attm. Reasons why am concerned about glazing tonight...00z/17 EC 2mT at 00z this evening as well as the 00z/17 NCAR ensembles forecasting the greatest amount of icing in the 18z/17 to 06z/18 time frame. Fog may become a problem, especially late and especially south of I-78. 00z/17 ECMWF 2 m temps blended with the colder of the avbl NCEP MOS guidance. Min temps around 15 degrees above normal!
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/... The long term part of the forecast will feature a continuation of mild temperatures for mid-late January. High temperatures will be mostly around 10 degrees above norma thru the period. There will be several wet weather systems. The first will be across the area Wed morning, but pops will decrease thru the day as low pressure and its fronts pass east of the region during the afternoon. This will be followed by a period of dry weather from wed night thru Fri morning. Low pressure will move into the upper Great Lakes region Friday and its attached warm front will approach/cross the region Fri into Sat. A period of showers will accompany the feature. Overall rainfall amts will be rather light however. A stronger system will move slowly across the Mississippi/lower Ohio Valley region Sun-Tue next week. This will draw moisture northward from the Gulf of Mexico. It appears that a decent rainfall event will occur across our forecast area Mon-Tue with this system. Rainfall amts of 1 to 2 inches could occur across our area. Pops are already in the low likely category for this time period. We will leave it as is for now. Latest GFS/EC are showing good agreement with the broad scale timing/location of the system. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...MVFR cigs lower to IFR during midday with vsby decreasing to MVFR in periods of rain. light wind...trending northeast or north KABE/KRDG while light south to southeast elsewhere. Tonight...Widespread IFR conditions expected with rain diminishing to drizzle and eventually fog as cigs lower through the night. Chance LIFR in dense fog? Light wind trending north to west entire area overnight. OUTLOOK... Wed...Morning clouds/showers will yield to improving cigs/vsbys. Wed night thru Fri morning...Mostly VFR expected. Fri afternoon thru Saturday...Lower cigs/vsbys possible. Showers. Sat afternoon-Sat night...mostly VFR.
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&& .MARINE...
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No headlines through Tonight. Wave heights will still be around a foot or 2 with sustained winds generally under 13 knots, fairly quiet on the waters. OUTLOOK... Wed thru Sun...Sub-SCA conditions. Showers Wed morning, Fri-Sat morning. Sun night...SCA developing with low end Gale possible. Showers.
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&& .CLIMATE...
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January 2017 at PHL is projecting 17th warmest January on record with the PHL database back to 1874. The current monthly avg through the first 16 days of 35.8 degrees is forecast to warm by at least two degrees, when all is said and done for January. This should mean a similar warmup for the remainder of our forecast area so that the generally 2 to 3 degree above normal temperatures will end up 4 to 5 degrees above normal. The exception...Mount Pocono, which was normal for the first 16 days but it too should end up at least two degrees above normal. PHL, using this mornings 330 am Mount Holly fcst thru 7 days, then the FTPRHA for D8-11, finally using normal temps the 28th- 31st offers a monthly avg of 38.1 degrees, or 5.1 above normal. We probably wont post on this again for a few days but suffice to say...the warmth during the heart of the coldest part of winter eases the fuel oil bite on the bank account. We have seen the BUFAFDBUF climate section commenting on stratwarm. While not an expert on the subject, I do like the NAEFS D8-14 as generally helpful in outlooking temperatures with respect to normal. As it stands this morning (00z/17), the NAEFS is still with a near 90 percent probability that the 6 day period of the January 25-February 1, as a whole, will be above normal. It might end up only a smidge above normal but there is not clear cut sign of a major cold outbreak here before the 28th of January. Colder than normal trends are showing up toward Feb 1. Usually there is a complication regarding the arrival of these potential regime changes. In the meantime, enjoy the warmth.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...Freezing Rain Advisory until 7 PM EST this evening for PAZ054- 055. Freezing Rain Advisory until 10 AM EST this morning for PAZ060>062. NJ...Freezing Rain Advisory until 7 PM EST this evening for NJZ001. Freezing Rain Advisory until 10 AM EST this morning for NJZ007. DE...None. MD...None. MARINE...None. && $$ Synopsis...Iovino/O`Hara 600 Near Term...Drag 600 Short Term...Drag Long Term...O`Hara Aviation...Drag/O`Hara 600 Marine...Drag/O`Hara Climate...600

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