Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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280 FXUS61 KPHI 210722 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 322 AM EDT Fri Apr 21 2017 .SYNOPSIS...
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A nearly stationary front will exist today from southern New Jersey into northern Maryland. Low pressure moving from the Great Lakes region into southeast Canada, will pull a cold front across the area Friday night. This front will stall to our south over the weekend. An area of low pressure is forecast to strengthen as it moves off the southeast coast late Sunday, then move north offshore of the east coast through early next week. A cold front is expected either next Wednesday or Thursday as an area of low pressure moves out of the Great Lakes region into southeast Canada.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Early this morning. Cloudy patchy fog forming. showers now spreading into the I78 region northward will sag southeastward so that after daybreak most of the showers should be aligned near I-78 and heading southeast into Philly and s NJ before dissipating around 10 am. Isolated embedded thunderstorm. Otrw...light east wind. The daylight hours after 10 am...have had to lower temps considerably from vicinity PHL north due to cloud cover and a chilly marine shower sodden boundary layer, especially I-78 northward. max temps today from the mid 50s near I-80 to near 85 southwest DE where a decent amount of sunshine is anticipated. It should be convectively unstable on the Delmarva this aftn for a group or two of showers and tstms. One or 2 storms may be strong and certainly produce heavy rain. Light easterly flow in the cool sector and variable mostly southwest to west flow in the warm sector...especially s DE and the MD lower e shore. Bay breeze could impact temps vcnty Dover De today and certainly further north of Dover De. This 330 am fcst was a 50 50 blend of the 00z/21 GFS/NAM MOS and then that was blended with mesoscale models hrrr, rgem to handle the temperature differencing along the coasts and in the cooler boundary layer airmass across NNJ, ditto warmer s DE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
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Patchy fog, otherwise considerable cloudiness. Leftover early evening showers/iso tstms vcnty s NJ and the Delmarva. This part of the fcst was a 50 50 blend of the 00z/21 GFS/NAM MOS.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/... There is the potential for some unsettled periods during the long term, but not the entire time expected to be active. Some uncertainty with some model differences at times during the forecast. As we move into Saturday and continuing into Sunday, the front is expected to stall to the south, while an area of low pressure moves along the boundary well to our south. With stronger short wave/vorticity impulses expected to move across the area this weekend north of the frontal boundary and low pressure system, there will be a better chance of showers across the area Saturday through Sunday. The most likely areas for showers is expected to be from around the Philadelphia area southward. There will remain a chance of showers Sunday night across southern New Jersey and southern Delmarva, but chances decrease through the night as the short wave/vorticity impulses begin to move past the area. By Sunday night into Monday the low pressure to our south is expected to move offshore of the southeast coast, then begin lifting northward offshore of the east coast into the middle of the week. There is some timing differences in how fast the model guidance lifts this low offshore of our area, but there is a general consensus for a enhanced chance of showers around Tuesday for much of the area. Depending on how fast this system lifts north of the area, there could also be a small chance of showers into Wednesday. However, if it`s far enough offshore, most places should be precipitation free. There is also the possibility of a cold front approaching the area during the middle of next week as well. The ECMWF has it approaching Wednesday into Wednesday night, while the GFS has it approaching Thursday into Thursday night. This frontal boundary could bring another chance of showers to the area Wednesday or Thursday. && .AVIATION /07Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through 12z... MVFR cigs lower to IFR conds in showers/isolated tstms/stratus/fog. light mostly east wind. please see TAFS for specific details. After 12z...IFR and MVFR conds in st/fog to start the day with showers near KTTN ending by 14z. Conditions improving to cigs 2000-4000 ft in the afternoon. light wind. Tonight...MVFR or IFR cigs for a time during the early night should improve late at night. Patchy IFR fog possible. Wind becoming light north. OUTLOOK... Saturday-Sunday...Better chance for showers and lower conditions over the weekend. The highest chances for showers and lower conditions are expected from the Philadelphia area southward. Sunday night...A chance of showers remains for coastal New Jersey and central/southern Delmarva with possible lower conditions there. Elsewhere, improving conditions overnight. Monday-Monday night...Mostly VFR, lowering clouds overnight. Tuesday...MVFR conditions possible with showers, especially eastern New Jersey.
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&& .MARINE...
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No headlines at this time. winds east or southeast for a while this morning with a more southerly component for a time Cape May southward during midday before winds everywhere turn to northeast late today pr this evening and then northerly tonight Gusts near or above 20 kt may be possible in the vicinity of any thunderstorms late this afternoon in the De Waters. Wave heights on our ocean waters are forecast to favor the 3 to 4 foot range. Waves on Delaware Bay are expected to be 1 to 3 feet. OUTLOOK... Saturday...Winds may gust around 20 knots at times Friday night into Saturday, but overall should remain below advisory levels. Saturday night-Sunday...Conditions expected to remain below advisory levels. Winds shift from a west-northwest direction to a northeast direction overnight Saturday. Sunday night...Winds and waves begin to increase to advisory levels late Sunday night into early Monday morning. Monday-Tuesday...Small Craft Advisory conditions likely.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...Drag 321 Short Term...Drag 321 Long Term...Robertson Aviation...Drag/Robertson 321 Marine...Drag/Robertson 321

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