Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231346 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 946 AM EDT THU JUN 23 2016 .SYNOPSIS... Low pressure in western Pennsylvania will move southeastward and off the Atlantic coast later today. High pressure will then build in from the north for Friday into early next week. A slow moving cold front is forecast to approach from the northwest on Tuesday and move through the region on Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Adjustments to sky/pops grids with the round of showers/isolated thunder passing across the Delmarva and srn NJ. More sct activity across central NJ ern PA will be covered with chc pops for the next few hours. There remain some degree of uncertainty in the forecast which revolves around how much will the atmosphere be able to rebound/destabilize this afternoon in wake of this morning`s clouds/MCS. Based on the latest guidance, there will likely be scattered convection developing during peak heating across eastern PA and central/northwest NJ along the residual outflow boundary and/or differential heating boundary to the north of where MCS tracked earlier. Majority of the model forecast soundings show the atmosphere capped, which would hinder convective updrafts and our thunderstorm potential. Still kept a slight chance of thunder in the weather grids for the mid to late afternoon. High temperatures should generally in the in the upper 70s and lower 80s. The warmest conditions are expected across the northern half of the CWA as well as the lower Delmarva, where the greatest potential to see extended breaks in the clouds reside. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Some of the hires convective-allowing model guidance advertises a second MCS developing along or just south of the Ohio River. If it develops, it should track mainly to our southwest tonight given the distant position of the frontal boundary to our south and with weak high pressure building in from the north. Kept low chance PoPs in the forecast for our Delmarva/Delaware Bay zones tonight to account for the possibility of the northern periphery that these showers and storms clip us. There is still a limited risk that a storm or two becomes strong to severe this evening mainly across the Delmarva. The threat would transition from winds to hail late in the evening as convection becomes increasingly elevated. Patchy fog may also develop late this evening and especially overnight. There greatest potential will reside across the southern portion of the area, where the ground remains wet after today`s precip. However, convective debris clouds may linger across the lower Delmarva, which should inhibit the formation of radiational fog. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... High pressure will be the dominant wx feature for the extendd period. The high will build down from Canada on Fri and influence our wx into early next week. THe current fcst is for dry and pleasant wx durg this time. There is one potential fly in the ointment though. A mid level trof is fcst to knock back the ridge a bit on Fri. The majority of the guid keeps any precip assocd with this trof to our w and s. However, the ecmwf is more robust and brings precip acrs our area and then develops a sfc low which moves out to sea on Sat. For now, will maintain a dry fcst, since the ecmwf is the outlier and go with the majority of the mdls and wpc. By Mon, an area of low pres will be movg acrs ern Canada. Its assocd cdfnt will approach from the w late Mon and cross the area on Tue, with a secondary fropa Tue night into erly Wed. Both cfp will bring the chc of shwrs/tstms. High pressure will then build in for the remainder of Wed. Temps look to be near seasonal values with comfortable dew points. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. By-in-large VFR conditions even in the remnants showers which are passing thru KMIV/KACY. KMIV was at 5SM in the most recent ob. Clouds upstream are thinning. Daytime CU will develop this afternoon. These may further develop into CIGS later. Winds will be mostly light and somewhat variable today. More scattered showers could develop after 18Z before ending around 02Z. Added a 2-3 hour prob30 group for most of the terminals for late in the day. While an isolated thunderstorm is not out of the question this afternoon, confidence too low to include in TAFs. Patchy fog could develop late this evening and overnight. Winds will be light (under 10 kt) and variable thru the period. OUTLOOK... Friday through Monday...VFR under high pres. Mdt confidence Friday. High COnfidence for the rest of the period. && .MARINE... Winds and seas below SCA today and tonight. A sly swell around 2-4 ft will continue in our coastal Atlantic waters thru the period. One potential impact on our southern waters could be locally gusty winds in thunderstorms his evening. Coverage of storms will be low. OUTLOOK... Friday through Monday...No marine headlines are anticipated. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Nierenberg Near Term...Klein/O`Hara Short Term...Klein Long Term...Nierenberg Aviation...Klein/Nierenberg/O`Hara Marine...Klein/Nierenberg/O`Hara

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