Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 181025 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 625 AM EDT Wed Apr 18 2018 .SYNOPSIS...
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Low pressure will continue to slowly move north and east through the Canadian Maritimes today and tonight. A second area of low pressure will approach from the west and move across the mid-Atlantic region on Thursday. As the low moves away to the northeast on Friday, high pressure will begin to build in from the west, continuing through the weekend and into early next week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The Freeze Warning continues for the Pennsylvania counties of Berks, Chester, Montgomery and lower Bucks, as well as for Cecil County in Maryland. It will be in effect until 8:00 AM. Weak high pressure was located in the Virginias early this morning. The high is forecast to slide southeastward today. We are anticipating a mostly sunny sky for today, after some morning clouds. The wind will be from the west around 10 to 15 mph with gusts near 20 mph. The wind should begin to diminish late this afternoon. Maximum temperatures are forecast to range from the middle 50s to the lower 60s in our region. Readings may not get much above 50 in the elevated terrain of the Poconos and far northern New Jersey.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
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Surface low pressure is forecast to be located in Ohio this evening. The low is expected to move into Pennsylvania tonight with its energy transferring off the New Jersey coast around daybreak on Thursday. We are expecting a rapid increase in cloud cover this evening, especially over eastern Pennsylvania and New Jersey. Light rain should spread into our region from the west. The rain may not quite reach southern Delaware and the adjacent counties of eastern Maryland. Rainfall amounts will be rather light, with perhaps one or two tenths of an inch across our northern counties and only a few hundredths of an inch of rain in areas to the south. The warm advection in advance of the approaching low will keep this an all liquid precipitation event for tonight. Low temperatures are forecast to range from the upper 30s in the Pocono Region and in far northern New Jersey to the upper 40s in southern Delaware.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
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Thursday Through Friday... To start the period, a low pressure system will be stretched west to east across northern portions of the forecast area near I-80 with its attendant cold front extending south over eastern PA near the western CWA border. Some rain and showers will be ongoing near and north of the low with any precip farther south toward Philly and Trenton and points south more scattered in nature in the warm sector. Heading forward through the day Thursday, aformentioned cold front will sweep east across the forecast area through the morning into the early afternoon as the low moves east into southern New England. This will result in morning highs mainly in the 50s to low 60s (40s in the southern Poconos) with temperatures falling off in the afternoon. Steadier rain early in the day across the north will quickly move out but as a couple shortwaves pivot around the upper level trough centered over the northeast this will bring some additional scattered showers by the late morning into the afternoon along with, especially across the north, along with considerable cloud cover. Also, the pressure gradient will really tighten up in the afternoon in the NW flow behind the system resulting in gusty winds, aided by fairly steep lapse rates. Generally expect NW winds 15 to 25 gusting up to 35 mph. Thursday night...chilly, NW flow persists in the way of the low with 850 mb temps by morning indicated to be near -8 C. However the winds should keep the boundary layer well mixed so only calling for lows mainly in the mid to upper 30s except near 30 in the southern Poconos. Most of scattered precip will diminish except across the southern Poconos where some showers will persist and change over to snow showers as the temps drop. Friday is shaping up to be a cool, breezy, but mainly dry day as NW flow persists under a mix of sun and clouds. Highs will generally be in the low to mid 50s except 40s across the southern Poconos and NW NJ...a good 10+ degrees below average. Friday night through Tuesday... Quiet for this period as high pressure will move in and dominate our weather. High pressure will initially be centered over the Great Lakes Friday evening with a continuing cool, NW flow over the area. However through the course of the weekend, the high will build south and east becoming centered over the area by late Sunday. The result will be dry weather with plenty of sunshine and a gradual moderation toward more seasonable temperatures through the weekend. Lows Friday night will be generally in the 30s with highs Saturday in the 50s but by Sunday expect highs likely cracking 60 degrees over much of SE PA, central and southern NJ, and the Delmarva. Heading into early next week, this drier, warmer pattern dominated by high pressure persists as the surface high moves off the coast of New England with an associated upper level ridge building over the northeast. Partly to mostly sunny skies persist with highs for most areas into the 60s both Monday and Tuesday. The exceptions to this will be along the NJ coast and over the southern Poconos. East winds will keep conditions right along the coast cooler due to the still cool ocean waters so highs will be in the 50s here.
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&& .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR. Clouds with bases 4000 to 6000 feet through about 14z, then mainly clear. West wind 8 to 12 knots with gusts near 20 knots, becoming southwest 5 to 10 knots late this afternoon. Tonight...Mainly VFR. Light rain developing at KRDG, KABE, KTTN, KPNE, KPHL and KILG. There is the potential for MVFR conditions at KRDG and KABE. Light and variable wind at KRDG and KABE. Wind becoming southeast around 4 to 8 knots at KTTN, KPNE, KPHL, KILG, KMIV and KACY. Outlook... Thursday...Occasional restrictions to MVFR possible Thursday in low stratus and scattered showers, mainly from PHL northward. Winds becoming NW gusting up to 30 knots in the afternoon. Moderate confidence. Thursday night and Friday...Mainly VFR, but with NW winds gusting to 25 kt. Confidence moderately high. Friday night through Sunday...VFR conditions expected, with diminishing NW winds. High confidence.
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&& .MARINE...
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We have made a minor adjustment to the Small Craft Advisory. We will leave it in place for the waters off New Jersey until noon. However, it appears as though the west wind will diminish below the criterion a bit earlier than that on the waters off Delaware and on Delaware Bay. As a result, we will end the advisory for those locations at 9:00 AM. The wind is forecast to settle into the southwest to southeast quadrant from late today into tonight at speeds favoring the 10 to 15 knot range. Outlook... Thursday through Friday...SCA conditions likely for most of this period with a period of gale force NW winds likely Thursday afternoon through Thursday night. Friday night through Sunday...SCA conditions may linger into Friday evening but otherwise diminishing winds with no marine headlines anticipated.
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&& .FIRE WEATHER...
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The relative humidity should drop into the 30 to 40 percent range this afternoon in far southeastern Pennsylvania, southern New Jersey and the upper Delmarva. A west wind is forecast to gust around 18 to 22 mph. However, the ground and fine fuels remain moist from Monday`s heavy rainfall so fire weather concerns are rather low.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...Freeze Warning until 8 AM EDT this morning for PAZ060-101>104- 106. NJ...None. DE...None. MD...Freeze Warning until 8 AM EDT this morning for MDZ008. MARINE...Small Craft Advisory until noon EDT today for ANZ450>453. Small Craft Advisory until 9 AM EDT this morning for ANZ430- 431-454-455. && $$ Synopsis...Fitzsimmons Near Term...Iovino Short Term...Iovino Long Term...Fitzsimmons Aviation...Fitzsimmons/Iovino Marine...Fitzsimmons/Iovino Fire Weather...Iovino

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