Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 271640 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1240 PM EDT WED JUL 27 2016 .SYNOPSIS... A weak front will stall to our south today into Thursday. A few waves of low pressure developing along this boundary will result in periods of showers and thunderstorms late in the week into early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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for the 1230 pm significant changes were made to the forecast. max heat indices in the mid 90s are still expected today along and south of the i-95 corridor. 88d was indicating an isolated but strong thunderstorm along the maryland coast just south of ocean city. some of this activity could gradually drift north, with areas southe of the C&D canal having the best chances of seeing any thunderstorm activity this afternoon (30 percent or less). seabreaze moving west could change the wind direction from east- southeast to south as far inland as PHL this afternoon, all under 10 mph. ...discussion below from earlier afd... Mid morning surface analysis shows a zonally oriented stationary front located near the southern tip of NJ, extending back to the west across central DE and eastern MD. Differential heating owing to strong heating and sunshine on the cool, northern side of the boundary and increasing cloud cover along and south of the boundary, frontolysis is expected. There will still be some weak wind convergence along the axis of the pressure trough, which could provide enough lift for convective development during peak heating this afternoon. Made some minor tweaks the PoP/Weather grids based on the latest hi-res model guidance. Isolated to widely scattered showers and storms are expected in Delmarva and the coastal plain in far southern NJ, where the greatest low- level lift and instability will forecast to reside. Forecast high temperatures are in the lower 90s across a majority of the region. Readings should not get out of the 80s in the elevated terrain of the Poconos and northwestern New Jersey. Also, a developing sea breeze should keep temperatures from rising above the 80s along the immediate coast. Dew point readings are expected to be mainly in the 60s in eastern Pennsylvania and New Jersey and in the lower 70s in much of Delaware and northeastern Maryland. Heat index values will likely be near or only slightly above the air temperatures where dew points are in the 60s. Heat index values are forecast to reach the upper 90s in much of Delaware and northeastern Maryland due to the expectation of higher dew points there.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... The frontal boundary should remain to our south for tonight. We will keep a slight chance of showers and thunderstorms in the forecast for our southern counties. Otherwise, the sky should be in the mostly clear to partly cloudy range. The wind is expected to be light and variable and temperatures should fall back into the 60s in our northern counties and into the 70s in the south. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The chance for showers and thunderstorms will be on the increase through Friday with a weak front in the area, potential waves of low pressure along the boundary, and surging precipitable water values. At this point it appears the highest chances will occur during Friday as a stronger in a series of hard to time impulses moves west to east across the region. The threat for severe weather will be highest farther south during Thursday as instability is limited for the northern areas. The latest SPC outlook highlights a Marginal Risk across southern NJ, MD and DE. A Marginal Risk will expand across NJ Friday however, expect the potential for heavy rainfall/flooding to be a potential threat as well. During Friday the precipitable water is projected to range from 2 to 2.3 inches, which is above the 90th percentile for this time of year. The precipitable water will remain around 1.5 to 2 inches during Saturday while the swath of higher values will be displaced offshore in the wake of the aforementioned impulse. Regardless, with a couple waves of low pressure expected along the boundary unsettled weather will persist into the first part of next week. Max temperatures will be warmest during Thursday with afternoon heat indices of 96 to 99. Otherwise, increasing cloud cover and convection will limit max temperatures Friday through early next week. Low temperatures each night will be a category above normal through Saturday night, then near normal for the remainder of the extended period. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are expected through the TAF period under a mostly clear sky. The wind is forecast to be 8 knots or less. The direction may favor the northeast to east for a time this morning before switching to the southwest and south during the afternoon. The direction is anticipated to be variable for tonight. Outlook... Thursday through Sunday...Mainly VFR conditions are expected. However, the potential for shra/tsra Thursday through Sunday will support tempo MVFR/IFR conditions at times. && .MARINE... The wind direction is forecast to veer from the north this morning to the south for this afternoon into tonight. Wind speeds will be generally 10 knots or less. The ocean will be like a mill pond (in the words of our former marine report relay Mrs. Cook) with wave heights of 2 feet or less. Waves should be 1 foot or less on Delaware Bay. Outlook... Thursday through Sunday...Light and variable flow under a weak pressure gradient early Thursday will become southerly around 10 knots with lower pressure across PA and weak high pressure farther offshore. The pattern becomes a little more complex by Friday night as low pressure may evolve near Delmarva. The low is projected to move northeast during Saturday across the offshore waters. The passage of the low would support light east winds Friday that would back to a north-northeast direction and increase a notch Saturday morning prior to lifting away later in the day. A weak pressure gradient during Sunday would result in light onshore flow. Seas of 2 ft or less are expected during Thursday with a combination of a minimal southerly wind wave and minor southeast swell. Multiple higher frequency wave components are likely during Saturday given the shifting winds with a dominant easterly wind wave taking hold. Seas will subside some during Sunday. Advisory criteria is not expected to be met at this time. Rip currents... There is a low risk for the development of dangerous rip currents for today due to the relatively light wind and tranquil seas. The probably risk for the development of dangerous rip currents on Thursday is also low. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Pfaff Near Term...Iovino/Klein/Miketta Short Term...Iovino Long Term...Pfaff Aviation...Iovino/Pfaff Marine...Iovino/Pfaff is the U.S. government's official web portal to all federal, state and local government web resources and services.