Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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257 FXUS61 KPHI 250720 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 320 AM EDT Sun Jun 25 2017 .SYNOPSIS... Surface high pressure over the Midwest gradually builds east as an upper trough encompasses the Great Lakes and Northeast. High pressure moves offshore Monday night, and then a cold front and upper trough passes through the region Tuesday and Tuesday night. High pressure returns on Wednesday, and then a series of frontal boundaries will pass through the region through the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure will be ridging across the area today while low pressure remains to the north. A dry day with mostly sunny skies is expected by-in-large. There could be a few isolated showers across the southern Poconos this afternoon. We have reduced the pops slightly from the earlier fcst. Temperatures will be seasonable for late June with low 80s across the north and mid 80s over Delmarva and metro Philadelphia. Winds will be west to northwest around 10 mph. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... Fair weather will continue tonight with mostly clear skies and light winds. Low temperatures will drop into the low/mid 50s across the north and upper 50s to low 60s elsewhere. Winds will be light and variable. && .LONG TERM /MONDAY THROUGH SATURDAY/... The first half of the new week will feature surface high pressure building into the Southeast U.S. as an upper trough digs into the Great Lakes and Northeast. Several shortwaves will pass through the base of the trough Monday and Monday evening, and this may touch off some isolated showers and thunderstorms, mainly north and west of the Fall Line. Monday will end up being dry for most of the region due to the influence of the surface high south and west of the region, and temperatures will be several degrees below normal, topping off in the mid to upper 70s. Humidity levels will be quite comfortable, as surface dewpoints will be in the 40s and low 50s. On Tuesday, a stronger shortwave will dig through the OH/TN Valleys and into the Appalachians and will push a cold front into the region through the region during the afternoon and evening. Weak surface low pressure develops off the Mid-Atlantic coast, but this low looks to be too far south and east to have much of an impact for the Mid- Atlantic and Northeast coasts. However, the 00Z ECMWF is showing a closer track to the coast than the NAM/GFS/CMC-GDPS, so this does bear watching. For now, will keep PoPs capped at slight chance- chance with the passage of the cold front. Another relatively cool day on tap with highs once again in the 70s. High pressure builds into the Mid-Atlantic on Wednesday, and then moves offshore Wednesday night. Dry with plenty of sunshine, and temperatures tick up a few degrees as compared to Tuesday with comfortable humidity levels. From there, an upper trough digs into the Northern Plains and gradually works its way east into the end of the week. Several strong shortwaves will dive into the base of the trough, and surface low pressure develops out ahead of the trough. Each low will pass north of the region from Thursday through Saturday, but each low will drag a weak frontal boundary through the region. This will touch off scattered showers and thunderstorms during this time, but the forecast may end up reading worse than it may actually end up being. With surface high pressure now offshore for the end of the week, SW flow will tap into Gulf moisture and brings a return to the heat and humidity across the region. Highs climb back up through the 80s to around 90 with dewpoints building through the 60s and into the low 70s by the weekend. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Good flying weather across the region today and tonight. Low pressure remains to the north while a ridge of high pressure builds over our area. Winds will generally be from the west or southwest much of the day. Winds speeds will mostly be around 10 knots after mid-morning. A few gusts closer to 20 knots are possible. Tonight, mostly clear skies expected and winds under 5 knots. OUTLOOK... Monday and Monday night...Mostly VFR, but isolated SHRA/TSRA possible at KRDG/KABE. SW winds 10-15 KT with gusts to 20 KT during the day and less than 10 KT at night. Tuesday...Mostly VFR, but isolated SHRA/TSRA possible, mainly in the afternoon/evening. SW winds 10-15 KT with gusts to 20 KT during the day and less than 10 KT at night. Wednesday...VFR conditions expected. Thursday...Mostly VFR. Isolated SHRA/TSRA possible. && .MARINE... Good weather expected on the waters today and tonight. The remaining SCA flag that was up for the northern NJ coastal waters will be taken down with the 330 issuance. Seas will mostly remain around 3 ft on the ocean today and 1-2 ft across Delaware Bay. Winds will be northwest this morning and then west or southwest tonight. OUTLOOK... Monday through Wednesday...Winds and seas should stay below SCA criteria. Isolated SHRA/TSRA possible Monday through Tuesday. Dry on Wednesday. Thursday...SCA conditions may develop in the afternoon. .RIP CURRENTS... We will forecast a low risk for rip currents for today and tonight. && .TIDES/COASTAL FLOODING... Tide levels may approach but not quite exceed minor coastal flooding thresholds with the evening high tide tonight. Will not issue a Coastal Flood Advisory at this time. A similar situation may develop again with Monday evening high tide. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...MPS Near Term...O`Hara Short Term...O`Hara Long Term...MPS Aviation...MPS/O`Hara Marine...MPS/O`Hara Tides/Coastal Flooding... is the U.S. government's official web portal to all federal, state and local government web resources and services.