363 FXUS61 KPHI 050145 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 845 PM EST Wed Nov 4 2020 .SYNOPSIS... High pressure remains entrenched off the Northeast coast into the middle of next week. A cold front may pass through the region late next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... No significant changes for the late evening update. As the high becomes entrenched over the Mid Atlantic, tonight will be the first of several nights with a potential for fog. Continued a mention of patchy or areas of fog. For tonight, expect much of the fog to be confined in the river valleys, though there is potential in the Pine Barrens and inland northern Delmarva as well. Skies will remain mostly clear overnight and winds will be light. The clear skies and relatively light winds will promote efficient radiational cooling, though higher moisture content and a light southerly component in the boundary layer flow should help to keep temperatures slightly higher than Tuesday night. Lows will range from the upper 30s/low 40s for the north and mostly low or mid 40s for Delmarva and south NJ. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... High pressure continues across the region along with slowly rising H5 heights during the morning. Fair weather will continue. Temperatures will remain mild for the first week of November with highs reaching the 60-65 degree range for the north/west and 65-70 for the southern/eastern counties. These values will be 10 (or more!) degrees above normal. Winds will be mostly SW at around 10 mph by afternoon. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Surface high pressure remains east of the Northeast U.S., over the western Atlantic Ocean waters as another area of high pressure establishes itself over the Mid-Atlantic. This high will become the dominant high, almost as if it is a Bermuda High late this week and into the start of the new week. Persistent onshore flow develops Thursday night, and increasing low-level moisture develops across much of the region. Patchy fog develops late as that moisture increases and surface temps drop down to the surface dew point. Meanwhile, some weak mid- level shortwave energy approaches from the west. This may be enough to trigger some rain late Thursday night into early Friday morning, mainly across portions of southern Delaware and extreme southeast New Jersey. The trough passes through the region Friday afternoon, and then strong high pressure establishes itself off the Mid-Atlantic coast this weekend and into next week. With increasing southerly flow, temperatures and surface dew points will gradually rise into next week. Can expect fog to develop each night, but sensible weather will generally be quiet until late next week. By Wednesday or Thursday of next week, dew points will be well in the 60s, possibly approaching 70. A cold front approaches on Wednesday and passes through Wednesday night or Thursday. With dew points well in the 60s, there may be enough instability to allow for some convection. Will introduce a slight chance for thunderstorms Wednesday afternoon. Highs will be above normal during the period, with highs generally in the 60s to near 70, and lows generally in the 50s. Only difference will be Friday night, when radiational cooling conditions may be strong enough to allow temperatures to drop into the 40s. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR conditions are expected for much of the night. There is an increasing chance for fog, especially in river valleys. I have included a mention of 6SM BR in the TAFs where fog is most likely, but will continue to watch trends through the evening. Winds should be light (near or below 5 kt). Direction could be variable, but should generally favor SSW. Moderate confidence on the overall pattern, but low confidence on the potential for fog. Thursday...Once any morning fog dissipates, VFR expected with mostly clear skies. Winds generally west to southwest at 5 to 10 knots. Moderate confidence. Outlook... Thursday night through Tuesday...A prolonged period of VFR conditions during the day, and patchy MVFR or lower conditions in fog at night. Generally S-SW winds 5-10 kt during the day and LGT/VRB at night. High confidence on VFR during the day. Low confidence on fog at night. Moderate confidence on wind forecast. && .MARINE... Tonight and Thursday... Fair weather. Southwest winds mostly around 10 knots. Outlook... Thursday night through Tuesday...A prolonged period of sub-SCA conditions. Generally S-SW winds 10-15 kt. Patchy nearshore fog with VSBY restrictions developing late at night and in the early morning. Best chances for more widespread fog towards the middle of next week. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...MPS Near Term...Johnson/O'Hara Short Term...O'Hara Long Term...MPS Aviation...Johnson/MPS/O'Hara Marine...MPS/O'Hara