Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 191401 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1001 AM EDT Thu Apr 19 2018 .SYNOPSIS... An area of low pressure will move out to sea this morning. This low will then drift into the Canadian Maritimes through Friday, which will keep northwest flow across the area with a couple of dry surface troughs moving across the east coast. High pressure will build into the Mid Atlantic and Northeast Saturday through Sunday, before moving offshore Monday into Tuesday. A coastal low may move north along the coast and affect the area during the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The surface low pressure system located offshore of the Mid Atlantic coast this morning will continue to lift to the northeast through today away from our area. Meanwhile, a couple of short wave/vorticity impulses will move across the area as well. We had one round of showers early this morning associated with the surface low pass through the area. A second round of showers associated with the first short wave is moving across Delaware, Maryland, and southern New Jersey now through the late morning hours. Finally, another round of showers ongoing to our west associated with the next short wave will move across the area during the midday and afternoon hours. Temperatures across most of the area will remain well above freezing to keep precipitation rain for most places. The exceptions would be across the higher elevations of the Poconos of northeast Pennsylvania, as well as portions of extreme northwest New Jersey. With temperatures in the low to mid 30s in some places, some snow will likely mix in, or be the predominant precipitation type. With temperatures being above freezing, little accumulation is expected, although would not be surprising to see up to an inch total snow through the day for the coldest spots where it is mostly snow. The wind is varying between northeast and northwest this morning as slight ridging has build in from the north, and a weak trough has developed in the backside of the low. As the surface low continues to moves out to sea, the wind is expected to become northwest everywhere. Wind speeds are forecast to increase around 15 to 20 mph with gusts approaching 30 mph for this afternoon in much of our region.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... The intensifying surface low is forecast to pass near Nova Scotia tonight and high pressure will begin building into our region from the west. The pressure gradient between the two systems should maintain a northwest wind around 10 to 15 mph for much of the night with gusts near 20 mph. The cloud cover is expected to decrease from south to north during the course of the night. Scattered light snow showers and flurries may linger in the Poconos and far northern New Jersey. Low temperatures are forecast to be mainly in the 30s in the Lehigh Valley, southeastern Pennsylvania, New Jersey, Delaware and northeastern Maryland. Readings should drop into the upper 20s in the elevated terrain up north. The northwest wind is expected to preclude the development of any frost tonight. However, temperatures may approach the freezing mark in some location where we have started to issue frost and freeze products for the season (generally from a Reading to Trenton to New Brunswick line southward). We are particularly concerned with parts of Berks County, Chester County and lower Montgomery County in Pennsylvania. We will take a look at the next full round of guidance before deciding whether a Freeze Warning is necessary. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Friday Through Sunday... High pressure will bring dry, quiet weather with sunshine for the weekend. To start the period Friday morning, low pressure will be over Atlantic Canada with an associated upper level trough extending back into the northeast CONUS. Meanwhile a broad high will be situated over the midwest. This will keep the area in a relatively cool, breezy, NW flow for Friday with highs generally in the low to mid 50s (40s across the southern Poconos). Early in the day there could still be some lingering snow/rain showers in the southern Poconos but otherwise conditions will be dry with considerable cloud cover persisting in the far north but otherwise partly to mostly sunny skies with just some afternoon Cu farther south. High pressure gradually builds eastward into the region through the course of Friday night and Saturday. The result will be lighter winds for Saturday and somewhat warmer temperatures as the airmass modifies. Most area will see highs in the mid to upper 50s Saturday under abundant sunshine with again, the southern Poconos being cooler in the 40s. The high will remain in place over the area right through Sunday bringing more sunshine with the general moderation in temperatures continuing as temperatures Sunday should be a few degrees warmer than Saturday. Sunday night through Wednesday... High pressure maintains control over the region bringing sunshine and seasonable temperatures through at least Monday. By Tuesday, the GFS indicates that a coastal low over the southeast US will begin to move north toward the area...potentially bringing in some light rain to southern areas by late day. However the ECMWF and GEM Global are slower to bring this system up and based on the GFS tending to be a little too progressive in these scenarios, we trimmed back POPs and keep Tuesday dry at this point. However by Wednesday, system looks to make its move up the coast as its associated upper level low opens up at the same time another trough moves in from the west. So we keep chances of rain in the forecast for Wednesday. Temperatures look to generally remain around seasonal through this period. && .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...TAFS are mostly VFR this morning, with ABE and RDG begin the exception as they are MVFR. CIGS are expected to lower to MVFR by this afternoon for the remaining TAF sites as lower clouds and showers move in from the west. An area of light showers will move across Maryland, Delaware, and southern New Jersey this morning, before another area of light showers is expected to impact all eight of our TAF sites this afternoon. Winds are varying between northwest and northeast this morning, but are expected to become northwest everywhere through the morning hours while increasing to 10 to 20 knots with gusts of 25 to 30 knots this afternoon. Tonight...VFR with decreasing cloud cover. Northwest wind 10 to 15 knots with gusts of 20 to 25 knots. OUTLOOK... Friday-Monday...VFR through the period. Gusty northwest winds gusting 20-30 knots Friday; 15-20 knots Friday night; and 10-15 knots Saturday.
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&& .MARINE... Low pressure off our coast early this morning will move farther out to sea and strengthen. A northwest wind will develop today and speeds should be on the increase. We continue to expect gale force gusts on Delaware Bay and on our ocean waters from Great Egg Inlet, New Jersey to Fenwick Island, Delaware. As a result, the Gale Warning remains in effect for those areas. We have a Small Craft Advisory for our waters off the coast from Great Egg Inlet northward to Sandy Hook. Wind gusts should be slightly lower there than in areas to the south. We are anticipating wind gusts to peak around 30 to 32 knots in the area covered by the Small Craft Advisory. OUTLOOK... Friday...Small Craft Advisory conditions likely in the morning with winds diminishing below SCA levels by afternoon. Friday night - Monday...Sub Small Craft Advisory conditions exected. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 4 PM this afternoon to noon EDT Friday for ANZ450>452. Gale Warning from 2 PM this afternoon to 8 AM EDT Friday for ANZ430-431-453>455. && $$ Synopsis...Fitzsimmons Near Term...Iovino/Robertson Short Term...Iovino Long Term...Fitzsimmons Aviation...Fitzsimmons/Iovino/Robertson Marine...Fitzsimmons/Iovino

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