523 FXUS61 KPHI 232022 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 322 PM EST Mon Dec 23 2019 .SYNOPSIS... High pressure over the Mid-Atlantic moves offshore tonight, and then a cold front moves across the region on Tuesday. High pressure returns from the north through the end of the week before departing. A cold front passes through the Northeast on Friday, and then low pressure may affect the area early in the new week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A weak cold front will move from north to south across the region tonight as a northern stream low passes just north of New England. Should be a very uneventful frontal passage, with a wind shift from southwest to northwest being the only noticeable effect. Winds may stay just elevated enough tonight to prevent ideal radiational cooling, so expecting lows to be generally a few degrees warmer than last night. Mostly upper 20s and low 30s. The frontal passage will also lower the odds of fog development tonight, though cannot rule out some patchy fog especially over Delmarva. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Quiet weather continues Tuesday. Behind the weak cold front and with high pressure to the north, surface winds will turn north- northeasterly. This will lead to a slightly cooler day, though only a few degrees cooler than Monday with abundant sunshine. Most areas will make it into the mid to upper 40s. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... High pressure over eastern Canada builds south into the Northeast U.S. Tuesday night and Wednesday. Dry conditions remain on tap for Christmas and through the end of the week with temperatures running several degrees above normal. The highs moves offshore and out to sea on Thursday. From there, low pressure tracking across Canada pulls a warm front north through the region late Thursday night, followed by a cold front on Friday. Overrunning precip develops out ahead of the warm front Thursday night. For the most part, temperatures will be warm enough to support plain rain, but surface temperatures will remain just below freezing across the southern Poconos and far northern new Jersey. This could result in a period of freezing rain in those areas from Thursday night through Friday morning, and then behind the warm front, temperatures warm back up above freezing, changing precip to plain rain. Cold front passes through the region Friday night and then high pressure builds back in from the west. High pressure briefly builds back into the region for the weekend, and then low pressure may affect the region Sunday through Monday. There is little consistency between the GFS and the ECMWF, so will carry chance PoPs for now, and will see how this develops over the next couple of days. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight... Mainly VFR. There is potential for localized fog development again tonight but it looks like a lower probability than recent nights. Westerly or west-southwesterly winds around 5 kt initially will become northwesterly at around 5 to 10 kt. By late tonight, the wind direction will turn more northerly. Have added LLWS to the TAFs for RDG and ABE due to stronger northwest flow above light surface winds. That should be less of a concern further south. Moderate confidence. Tuesday... Mainly VFR, with localized MVFR possible early due to fog or haze. North-northeasterly winds at around 10 kt. High confidence. Outlook... Tuesday night and Wednesday...VFR, however localized MVFR conditions are possible each early morning due to fog. LGT/VRB winds. Moderate confidence, however low confidence regarding any fog/low clouds. Thursday...Mainly VFR. Northeast winds 5-10 knots Thursday Thursday night and Friday...Sub-VFR possible in -RA, but a period of -FZRA is possible at KABE late Thursday night through Friday morning. Light NE winds Thursday night becoming light S on Friday. Saturday...VFR. W winds 5-10 kt. && .MARINE... Through tonight... Sub-SCA conditions are expected. West- southwest winds at around 10 kt through midnight, becoming northwesterly later and northerly towards daybreak. Gusts to 20 kt are possible late tonight. Seas 1 to 3 ft. Tuesday... Sub-SCA conditions are expected. North-northeasterly winds around 15 kt with gusts to 20 kt. Seas 2 to 4 ft. Outlook... A prolonged period of sub-SCA conditions on tap for the rest of the week and into the weekend. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...MPS Near Term...O'Brien Short Term...O'Brien Long Term...MPS Aviation...MPS/O'Brien Marine...MPS/O'Brien