Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 171750 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1250 PM EST Tue Jan 17 2017 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A warm front will continue to approach from the south and southwest today and it should reach Maryland and perhaps southern Delaware by evening. Low level moisture will be on the increase as a light east to south surface flow continues to develop. Clouds will lower and some patchy fog may form, especially in the hills of eastern Pennsylvania and northern New Jersey. Rain will continue to spread into our region from the west. A fairly steady rain is anticipated for part of the afternoon. Rainfall amounts should range from around a quarter inch in the Poconos, the Lehigh Valley and northern New Jersey to around a tenth of an inch in southern Delaware. Temperatures will continue to hover around the freezing mark in the elevated terrain of Monroe County, Pennsylvania and Sussex County, New Jersey today. As a result, there may be pockets of freezing rain there. The Freezing Rain Advisory remains in effect for the two counties. The advisory has been cancelled for Berks County, Carbon County, the Lehigh Valley and Warren County. Afternoon temperatures should favor the 40s in the Philadelphia metropolitan area, central and southern New Jersey, Delaware and northeastern Maryland. Readings are expected to remain in the 30s in the northern part of our forecast area. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... 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! && .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 /18Z TUESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Conditions are forecast to continue lowering this afternoon as areas of rain pass across the region from west to east. Conditions are anticipated to be in the IFR range at all eight of our TAF sites by evening (around 2200Z). IFR conditions are expected overnight with abundant low level moisture lingering in our region. The rain should taper to patchy drizzle. Areas of fog are likely. A developing northwest surface flow on Wednesday is forecast to slowly draw dry air into our region. Conditions are expected to slowly improve through the MVFR range and they should reach VFR during the afternoon. A light southeast wind this afternoon should become light and variable for tonight at most locations. The wind is expected to settle into the northwest for Wednesday and speeds are anticipated to increase around 10 knots for the afternoon hours. 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. && .MARINE... 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. && .CLIMATE... 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. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Freezing Rain Advisory until 7 PM EST this evening for PAZ055. NJ...Freezing Rain Advisory until 7 PM EST this evening for NJZ001. DE...None. MD...None. MARINE...None. && $$ Synopsis...Iovino/O`Hara Near Term...Iovino Short Term...Drag Long Term...O`Hara Aviation...Iovino/O`Hara Marine...Drag/O`Hara Climate...Drag is the U.S. government's official web portal to all federal, state and local government web resources and services.