Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 162038 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 338 PM EST Mon Jan 16 2017 .SYNOPSIS...
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High pressure will drift off the coast tonight. Low pressure is forecast to pass across the Great Lakes on Tuesday with a secondary low developing near Long Island on Tuesday night. 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 on Monday.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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An area of low pressure over the Great Lakes will track northeastward overnight with a warm front to our southwest. Lift along the warm front will be enough for some areas of light precipitation to develop toward sunrise. Used a MOS/Superblend blend which keeps pops fairly low south of Philadelphia and increases them through the chance range further north overnight. Temperatures look fairly tricky overnight. On the warm extreme we have the ECMWF and the latest HRRR which warm everyone except the Poconos above freezing fairly quickly. However, the RGEM and the NAM Parallel are colder. Given how it is usually hard to get rid of low level cold opted closer to the colder data at this point with the note that the RGEM has had a recent cold bias (so not that cold). We have issued a freezing rain advisory to cover any light periods of freezing rain overnight and during the morning commute on Tuesday where temperatures have a good shot at falling below freezing. Mid level temperatures will be well above freezing , no snow. Most of the region outside the Southern Poconos, Lehigh Valley and Northwestern New Jersey should stay above freezing overnight. Any ice accumulation would be minor but could still cause a few slick spots. Winds will be under 10 mph with cloudy skies moving by later this evening for the entire region.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
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The warm front will move through the region on Tuesday with the main low area of low pressure moving into Southeast Canada. Additional periods of rain will likely develop with the lift along the front and moisture streaming northward ahead of the low. The steadiest rain looks to be across northern portions of the area where up to a quarter inch of rain could fall. Went several degrees under where the MET/ MAV and ECMWF MOS have temperatures tomorrow given the clouds, rainfall and stubborn low level cold around. Temperatures may actually rise more toward in the evening than the high temperature forecasted through 00z. Winds will still be under 10 mph with cloudy skies.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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Three precipitation systems are expected to affect eastern Pennsylvania, northeastern Maryland, Delaware and New Jersey during the period from Tuesday night through Monday. However, temperatures should remain above normal and the precipitation is expected to fall in the form of rain. The closed mid level low that was located over Kansas this afternoon will progress to the northeast. The low is forecast to become an open wave before passing over the northeastern states around Tuesday evening. A 40+ knot low level southwesterly jet is anticipated to be located over the coastal plain at that time and it should be pushed out to sea on Tuesday night. A mid level short wave trough that was located over Manitoba, North Dakota and vicinity is forecast to progress to the southeast and it should pass off the Middle Atlantic coast on Wednesday afternoon. At the surface, a warm front should be up into the upper Delmarva and southern New Jersey on Tuesday evening with a cold front moving through western Pennsylvania and West Virginia. Low pressure is expected to develop around Long Island on Tuesday night before racing out to sea. We are anticipating a fair amount of lingering low level moisture on Tuesday night and Wednesday even as the mid levels dry in the wake of Tuesday evening`s short wave. We will continue to mention rain and rain showers during that period along with areas of fog for Tuesday night into Wednesday morning. The expected temperature profiles continue to suggest all liquid precipitation. Mid level ridging is expected over the eastern states for Wednesday night through Thursday night. Another short wave trough is forecast to lift over the northeastern states around Friday night with the ridge anticipated to re-establish itself over the east for the weekend. Surface high pressure is forecast to build across our region from west to east during the period from Wednesday night into Thursday night. The high will likely bring dry weather conditions. Surface low pressure is expected to move up the Ohio River Valley and into the eastern Great Lakes on Friday before weakening. A secondary low is forecast to develop off the Middle Atlantic coast on Friday night before moving quickly out to sea. As the main energy shifts from the Great Lakes to the coast, we are anticipating another rain event for our region beginning around midday on Friday and continuing through Friday night. Some rain may linger into Saturday, especially in the northern part of our region. Surface high pressure is forecast to build into our area from the north during the weekend. A broad closed low should be located over the Ozarks and vicinity late on Sunday and it is forecast to move toward the Ohio River Valley on Monday. Rain associated with the system may begin to overrun the surface high and it could spread into parts of our region as early as Sunday afternoon. Rain is anticipated for both Sunday night and Monday.
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&& .AVIATION /21Z MONDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Mainly VFR, with winds under 10 knots through this evening. A broken deck with intermittent MVFR ceilings from KRDG to KPNE and KACY southward into the evening will move from west to east near and likely over some of these TAF sites. Ceilings thickening and lowering at all TAF sites overnight to MVFR. On Tuesday, rain showers will start moving into the area between 10- 13 Z. Steadier rain after 16z. Likely cold enough for a potential brief interval of freezing rain around sunrise at KABE and KRDG. IFR ceilings and visibilities likely, potentially going lower in the afternoon. Winds still under 10 knots. OUTLOOK... Tuesday night and Wednesday morning...IFR and MVFR conditions are expected with fog and rain. Wednesday afternoon...Conditions are expected to improve to VFR. Wednesday night through Friday morning...Mainly VFR. Friday afternoon...Mainly VFR with a chance of rain. Friday night...MVFR and IFR conditions in rain and fog. Saturday...MVFR and IFR conditions in morning fog and rain, improving to VFR for the afternoon.
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&& .MARINE...
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Wave heights will still be around a foot or so with winds under 10 knots, fairly quiet on the waters. OUTLOOK... Tuesday night through Saturday...No marine headlines are anticipated.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...Freezing Rain Advisory from 4 AM to 10 AM EST Tuesday for PAZ054-055-062. Freezing Rain Advisory from 1 AM to 10 AM EST Tuesday for PAZ060-061. NJ...Freezing Rain Advisory from 4 AM to 10 AM EST Tuesday for NJZ001-007-008. DE...None. MD...None. MARINE...None.
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&& $$ Synopsis...Iovino Near Term...Gaines Short Term...Gaines Long Term...Iovino Aviation...Gaines/Iovino Marine...Gaines/Iovino

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