Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231704 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 104 PM EDT TUE AUG 23 2016 .SYNOPSIS... High pressure over our area today and tonight will shift offshore Wednesday. A weak cold front is forecast to move through during Friday, then high pressure builds in Saturday into Sunday before shifting off the New England coast later Sunday into Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Quiet weather on tap for the rest of today as high pressure remains over the area. Mostly clear conditions with only a few clouds are expected today. Temperatures will be a few degrees warmer than Monday, and end up a couple degrees warmer than normal. Humidity levels will remain low as dewpoints remain low today. Precipitation chances today are zilch. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... High pressure remains in control of the weather tonight, keeping mostly clear skies across the area. Overnight lows will likely end up a little warmer than Monday night as thicknesses begin to increase. It is also possible that some patchy fog may develop as temperatures cool and calm/light and variable winds develop again. Precipitation chances remain nil. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... The synoptic setup is comprised of a ridge across the southern states that expands into the Mid Atlantic region Thursday into Saturday. This ridge may then retreat back to the southwest some later in the weekend and early next week as a short wave trough tracks across the Midwest and into the Great Lakes region. This will result in building heat and humidity for the end of the week. We used a model blend for Wednesday into Friday, then blended in mostly the 00z WPC guidance with continuity thereafter. Some adjustments were then made following additional collaboration with our neighboring offices. For Wednesday and Thursday...As a ridge remains centered across the southern states, it begins to expand north-northeastward into the Mid Atlantic especially Thursday. As this occurs, surface high pressure slips offshore Wednesday and then farther out to sea Thursday. This will result in a return flow, however the main moisture advection looks to take place on Thursday. As a result, a warm afternoon Wednesday however dew points are expected to be in the comfortable range overall. The dew points then creep up some Thursday across much of the area. The flow looks to be light enough both days where a sea breeze develops and therefore it is possible that dew points increase in the wake of this boundary especially on Thursday. A lee-side trough may develop Thursday however it appears some initial convection develops to our west as enough subsidence from the southern states ridge mainly dominates much of our area. Some isolated convection however may move into our western zones Thursday evening as moisture/thermal advection increases some, therefore carried a slight chance pop. For Friday and Saturday...Our area looks to be on the northern periphery of a large southern states ridge. Some short waves traversing the westerly flow aloft from the Great Lakes to the Northeast may be enough to spark some diurnal convection. A lee-side trough looks to be in place Friday ahead of a weak cold front, therefore both of these features may focus just enough surface convergence for some convective development. The overall forcing looks weak with mostly the northern areas more removed from lingering subsidence of the ridge. As a result, we will continue to indicate slight chance pops Friday. It will be hot and much more humid Friday ahead of the weak cold front, however heat indices are anticipated to be below advisory criteria. The weak front looks to be offshore Saturday with high pressure starting to build in from the northwest. While a temperature drop should occur Saturday in the wake of the weak front, more of a dew point drop should be more noticeable for much of the area. For Sunday and Monday...High pressure builds across the Northeast into Sunday before it slides off the New England coast by late Sunday. As the high weakens or separates into two Monday, a short wave trough is forecast to be migrating across the Midwest to the Great Lakes. This should result in a warm frontal type feature developing into the Ohio Valley Monday. A ridge axis is forecast to be to our west, with a bit of a trough across the Northeast. Some guidance shows either some weak short wave forced convection Monday or terrain influenced. Given the timing uncertainty along with questions regarding the forcing mechanisms, maintained some slight chance pops for portions of the area Monday. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR through the TAF period. Some patchy MVFR VSBY in BR possible, mainly at KRDG, late tonight through daybreak Wednesday. Winds generally out of the N at 5 KT or less, backing to the W through the afternoon. S winds at KPHL will veer SW 6-8 KT starting by 20Z. Sea breeze should keep winds out of the SE at KACY 5-7 KT through this evening. LGT/VRB winds tonight, and then SW winds become 5-7 KT late Wednesday morning with afternoon sea breezes likely at favored terminals. Outlook... Wednesday and Thursday...VFR. Winds should favor a south to southwest direction at less than 10 knots, however turn more southeasterly each afternoon at ACY/ILG due to a sea/bay breeze. Friday...VFR overall. A few isolated showers/thunderstorms are possible as a weak cold front moves through. Saturday...Mainly VFR.
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&& .MARINE... The pressure gradient will weaken today as high pressure will move across the waters today and tonight. Winds will lighten through today and into tonight and remain well below Small Craft Advisory levels. Outlook... Wednesday through Saturday...The winds and seas are anticipated to be below Small Craft Advisory criteria. However, a southerly flow should increase for a time Wednesday and Thursday especially in the afternoon and evening with some enhancement from sea/bay breeze circulations. A weak cold front moves through Friday with a wind shift to the northwest, then more north-northeast Saturday. RIP CURRENTS... For today, the risk for the formation of dangerous rip currents looks to be low. For Wednesday, the probable risk for the formation of dangerous rip currents is low. However this may increase to moderate, especially for the New Jersey beaches, especially if the wind turns more southeasterly as it increases some in the afternoon. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Gorse Near Term...MPS Short Term...Robertson Long Term...Gorse Aviation...MPS Marine...Gorse/Robertson

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