Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 280713 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 313 AM EDT SAT MAY 28 2016 .SYNOPSIS... A ridge of high pressure across the mid-Atlantic region will maintain generally fair and warm weather through most of the weekend. Moisture from the remnants of a tropical system to our south may reach the area Sunday night and interact with a weak frontal system to produce showers and thunderstorms. More high pressure and dry but continued warm weather are expected through the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Prior to sunrise: patchy fog and haze near sunrise...thickest fog probably nw NJ to the lehigh valley. otherwise patchy cu and cirrus early this morning. of interest...dewpoints are several degrees cooler all along the mid atlantic coast when compared to 24 hours ago! light south to southwest wind. Today...Issuing an SPS for first heat wave and associated modest heat related risk for early season warmth. Expecting hottest day of this late May warm spell today and 1-3F warmer than ydy in e PA and most of NJ...even a degree or so warmer in De and MD E shore than ydy. Early season heat wave (Day 3 of the minimum three consecutive 90f or greater required) is at hand for PHL/PNE/ABE/WRI while other locations nearby in our CWA have been 89-90F the past two days and today will be day 3, but cannot officially note them as heat wave potential inclusive (GED/REG/TTN). So, after any early morning low clouds/fog/haze...a sunny or mostly sunny day with the forecast likely verifying above any of the warmest available guidance be it bias corrected, or individual NCEP op MOS, super and national blends (both blends 3-4F cooler than our official fcst). Best of the automated guidance is the adjust MET but have fcst warmer than that as well. 16c at 850mb with a south-southwest wind gusty to 20 mph this afternoon should allow temps to rise to 1-3F above yesterdays values (especially with slightly lower dewpoints), at least for e PA and interior NJ. Heat index 90-95 for NJ and e PA and maybe only near 90 DE/E MD. No advy but issuing an SPS. Synoptic Health Warning Network has been highlighting early season concerns for the I95 corridor the past several days. so while officially we dont reach the HI early season criteria of 96 for the ILG-=PHL-TTN metro corridor or 100 HI elsewhere, we think its the first heat wave of the season for parts of this area and day3 and probably a daily cumulative toll on health for those elderly or children with respiratory ailments and no air conditioned relief. Not anticipating convection this afternoon even in the pwat axis of 1.5" near and north of I-78...northern portion of our CWA. There is no known lift mechanism. Suppose something isolated can develop but with suppressant ridging at mid levels (500mb) today and lack of excessive moisture (PWAT of 1.5" for a 570 1000-500mb thickness is not excessive), therefore it seems difficult to develop afternoon convection. Have a small pop up north but convection i do not think is weather story for today. Max temps again 10-16F above normal with a general 50 50 blend of the 00z/28 GFS/NAM MOS guidance except heavy reliance on the warmer NAM BL and 2M temps, along with the overzealous RGEM and HRRR warmth but corroborated by the GGEM and ECMWF 2m temps. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... Fair and not quite as warm as this morning because the PWAT lowers northward from 1.5 to 1 inch tonight (also means lower dewpoints) with minimum temps probably 6 to 12F above normal and a light south to southwest wind. It may be hazy with patchy fog possible after midnight?, primarily in the countryside. Lower dewpoints reduce my concern for fog late tonight. In fact clouds from the leading edge of nwwd moving tropical moisture may be arriving over the Delmarva early Sunday morning. Meanwhile, Any evening showers along and north of I-80 in NNJ/ne PA quickly end during the evening. This part of the fcst was a 50 50 blend of the 00z/28 GFS/NAM MOS guidance. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The current summer-like weather pattern over the mid-Atlantic region is expected to continue through the extended forecast period. Temperatures will be somewhat above normal and precipitation will be mainly in the form of convective rain showers and t-storms. Surface and upper-level features affecting the area will remain relatively weak. One uncertainty at this time is how much effect we will see from the tropical/sub-tropical system now off the SE Atlantic coast. Moisture from tropical depression 2 NE of the Bahamas is forecast to move N into the mid-Atlantic on Sunday with an increasing chance of showers and T-storms by afternoon. Showers and storms are forecast to continue Sunday night into Monday as a weak frontal system moves into the area from the NW. PWATS are forecast to be near 2 inches over the area so some heavy downpours and possible flooding can be expected. Clouds and precip will result in milder daytime temps on Monday. By Tuesday somewhat drier air is expected to push in from the W and decrease the chances for precip as an upper-level trough moves by to the N. Daytime temps will recover back into the 80s as there is not much change in air mass with the with the associated surface front. Wed and Thu should be mainly fair with high pressure building in from the N/NE and low-level winds off the cool Atlantic. Both the latest GFS and ECMWF suggest another frontal system approaching from the W or NW by next Fri, with increased chances for precip. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through 12z...VFR with MVFR vsby possible toward 10z in haze or patchy fog. Small chc IFR stratus fog vcnty KRDG/KABE toward 10z. Light south to southwest wind. After 12z...any sub VFR vsby improves to VFR by 15z with only sct clouds aoa 5000 ft and a south to southwest wind gusty to 18 kt during mid afternoon. no convection expected at the TAF sites though not impossible to see a brief mid afternoon shower vcnty KABE/KRDG. Tonight...VFR with possible patchy MVFR vsby in haze or patchy fog toward 10z sunday. Light south to southwest wind. OUTLOOK... Mainly VFR conditions are expected through the period, except MVFR possible Sunday night thru Monday night in showers and T-storms. && .MARINE... No marine headlines anticipated through tonight. Winds were gusty 20-30 kt for a time this past Friday evening (44065 and Weather Flow sensors) along the coasts and this drove seas upward to near 5 ft at 44065. That was stronger than we expected 24 hours ago. The southerly flow and associated wind wave have subsided. So in essence, a south to southwest wind occasionally gusty to between 20-22 kt into tonight with Atlantic coastal waters seas 2-4ft and De Bay 1-2 Ft. OUTLOOK... Winds and seas are expected to remain below SCA criteria during the Sunday thru Wednesday time frame. Poor visibility is possible Sunday night through Monday night in showers and thunderstorms. RIP CURRENTS: We will probably cautiously forecast a LOW risk today but LOW does not mean NO risk!!! For safety swim in the presence of lifeguards. there will be an incoming 2-3 foot mixed s to se swell today of varying periodicity 4 to 9 seconds. A cooling southerly wind will develop this afternoon with gustiness possibly enhancing water buildup behind the sandbars which should mean an enhanced low risk. Am concerned about early season heat and about swimmers in unguarded areas. We do not want any news headlines about rip current fatalities. These fatalities are all preventable. They tend to occur in the younger male population, after hours unguarded locations. Its not worth the risk. && .CLIMATE... We`ll be adding considerable information to this section between 4 and 5 am Saturday. The KMPO temperature sensor was fixed yesterday. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...AMC/Drag/Johnson Near Term...Drag 313am Short Term...Drag 313 am Long Term...AMC Aviation...AMC/Drag 313am Marine...AMC/Drag 313am Climate...313 am is the U.S. government's official web portal to all federal, state and local government web resources and services.