Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 241049 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 649 AM EDT Mon Sep 24 2018 .SYNOPSIS... A front will remain south of the area today as high pressure builds across New England. The front will slowly move across the area tonight through Tuesday as low pressure moves into Canada. A cold front attached to this low will cross the Middle Atlantic region Wednesday night. Another weak low will affect the area Thursday. High pressure will build in Friday and remain for much of the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Today will be a very similar pattern to yesterday, with the high to our north and the front remaining to our south (at least through the day). The main difference looks to be that the main area of low level convergence, and thus precipitation will be a bit farther south than what we saw yesterday, mostly along and south of the PA turnpike/195 corridor. Any rain should be light and stratiform, so rain amounts look to be generally less than a quarter of an inch through the day. One other difference from yesterday will be the increasing pressure gradient, resulting in breezy easterly winds across the area, especially at the shore. Temperatures will be near or perhaps slightly higher than Sunday, especially up north where breaks in the clouds are more likely. Highs should generally be in the 60s across the region which is 5 to 10 degrees below normal. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... Tonight, the front, now a warm front, will begin to slowly propagate north through the region. As it does so, expect winds to shift to southeasterly and rain will become more showery. There remains a signal for heavy rain, especially with precipitable water values well above normal. However, most of the latest model runs keep the axis of heaviest QPF northwest of the region. However, will keep the mention of heavy rain leading to localized flooding in the HWO. A combination of persistent cloud cover and warm air advection behind the front will keep temperatures from dropping much overnight. Therefore, lows are expected to be 5 to 10 degrees above normal, ranging from the mid 50s to upper 60s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Unsettled conditions for the beginning of the long term, but then a pattern change could bring a drier period of weather for Friday and into the weekend. Tuesday and Wednesday...Low pressure will move from the upper Midwest into Canada Tue/Wed and draw a warm front across the area Tue followed by a moderately strong cold front Wed. We will just update the pops for these periods to bump them up since confid in the details is becoming better with each model run. The pops were also tweaked to match our neighboring offices better. A better chc for tstms Wed as the day will feature some breaks in the clouds and with the higher humidity level and being in the warm sector, CAPE values will be notably higher than Tue. Thursday...The front that crosses the area Wednesday night will stall south of the area, as it gets caught in parallel flow aloft. A weak wave will ride along it bringing increased clouds and higher chc for rains to affect the area Thursday and Thursday night. The highest pops will be across the southern areas since that will be closer to the disturbance. The 00Z operational models are all keying in on this, so we may eventually may have to raise pops for these periods. Temperatures Thu. will be near normal. Friday thru Sunday...The weak low pressure system from Thursday will be offshore Friday and any lingering clouds and precip will move away during the morning. We will just have slight chc pops for Friday attm, with much of the day expected to be fair. As high pressure moves in from the north, we expect the nicer weather to continue into the weekend. The upper flow will be much different next weekend with a brisk wrly flow and subtle troughing across ern Canada and New England. Temperatures will be near normal, or perhaps a few degrees above normal for late September. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...MVFR and some IFR ceilings around the area this morning may improve, at least briefly to VFR late this morning into the afternoon. This is an unusual pattern to see with low level on shore flow, so confidence in the forecast is low, especially with the timing of flight category changes. Easterly winds will be increasing through the morning, with 10g20KT possible by this afternoon. High confidence in the wind forecast. Tonight...Conditions should lower to MVFR with both ceilings and visibility as another round of rain moves into the region from the southwest. IFR conditions are possible, primarily after 06Z. Easterly winds will gradually shift to southeasterly around 10 KT, except at KACY where gusts near or above 20 KT may continue overnight. Low confidence. Outlook... Tue/Tue night...Lower cigs/vsbys possible mostly early with sct showers. Wed/Wed night...Sct tstms with lower cigs/vsbys psbl, mostly late afternoon and evening. Thu...Mostly VFR, but lower conditions psbl with sct showers. Fri...VFR expected. && .MARINE... Easterly winds will increase, with gusts above 25 KT expected on all the waters. Small craft advisory conditions are expected to persist through late tonight on the Delaware Bay before winds begin to diminish after midnight. On the Atlantic coastal waters, elevated seas will continue through out the night. Outlook... SCA conditions will continue Tue and will probably be extended through Wed as seas on the ocean will be slow to settle back below 5 ft, Sct showers Tue and showers and tstms Wed/Wed night. Sub-SCA conditions expected for Thu and Fri. Sct showers Thu and fair weather for Fri. Rip Currents... A high risk for the formation of dangerous rip currents is expected through at least this evening due to increasing onshore flow. Tides will be enhanced by the full moon which will also help enhance the rip current risk. && .TIDES/COASTAL FLOODING... We have issued a Coastal Flood Advisory for this evenings high tide cycle. We expect at least some spotty minor tidal flooding along the coasts of Delaware and New Jersey and along lower Delaware Bay. While water levels will get high along the upper eastern shore of Chesapeake Bay, no flooding is anticipated for that area at this time. An increasing onshore flow is expected for today and the astronomical tides will be high due to the full Harvest Moon. The onshore flow is forecast to continue tonight before veering to the south on Tuesday, from south to north. The following high tide cycle (Tuesday morning) may be affected too, but we will examine this later today and extend the advisory if necessary. && .CLIMATE... Yesterday, the Philadelphia International Airport (PHL) received 0.70 inches of rain, which brought the yearly precipitation total up to 41.58 inches. The normal rainfall for the entire calendar year at PHL is 41.53, which means we are already above normal for the year, with 99 days left to go. PHL joins the Atlantic City Airport (ACY), Mount Pocono (MPO), and Reading (RDG) as sites that have already reached their average annual precipitation. Both Wilmington (ILG) and Allentown (ABE) could reach their average annual precipitation this week, as those sites are within 1.08 and 0.90 inches respectively of that mark. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...High Rip Current Risk through this evening for NJZ014-024>026. Coastal Flood Advisory from 6 PM this evening to midnight EDT tonight for NJZ012>014-020>027. DE...High Rip Current Risk through this evening for DEZ004. Coastal Flood Advisory from 6 PM this evening to midnight EDT tonight for DEZ002>004. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ450>455. Small Craft Advisory until 2 AM EDT Tuesday for ANZ430-431. && $$ Synopsis...O`Hara Near Term...Johnson Short Term...Johnson Long Term...O`Hara Aviation...Johnson/O`Hara Marine...Johnson/O`Hara Tides/Coastal Flooding... Climate...

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