509 FXUS61 KPHI 020007 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 707 PM EST Fri Feb 1 2019 .SYNOPSIS... A weak upper-level system will more off the East Coast this evening, and surface high pressure will remain over the area tonight and Saturday. A low will develop off the Southeast coast on Sunday before moving well offshore early next week. A surface low in the Midwest on Monday will lift rapidly northeast into the Canadian Maritimes by Tuesday night, dragging a cold front through the area. Another surface low will progress from the central plains on Wednesday to New England by late in the week, allowing another cold front to move through the region. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Snow is exiting our region now. Therefore, allowed the winter weather advisory to expire on time. However, slippery driving conditions will persist overnight thanks to temperatures continuing to be well below freezing. Otherwise, no significant changes to the forecast. Clearing skies, light winds and a bit of fresh snow cover should lead to near ideal surface radiating condition through the evening and overnight, although temps aloft (e.g. 850 hPa) will be on the rise. The forecast overnight mins range from near zero in far north NJ to mid teens in southern DE, but would not be surprised to see colder readings towards morning in some areas. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... On Saturday, the core of the arctic air mass will have shifted well northeast back into Canada, and 850 hPa temps will be about 10 deg C warmer than today. With plenty of (albeit still rather weak) February sunshine, forecast max temps in the afternoon should reach well into the 30s F in most areas. Some high level clouds are possible mainly north of PHL with the approach of a weak frontal boundary. Surface high pressure will shift southeast and offshore, resulting in a return to southwest winds. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Midlevel flow becomes more zonal Saturday night and Sunday, with a broad/low-amplitude southern- stream perturbation moving into the Southeast. This should be a dry period for the CWA. The main story Sunday and Monday should once again be temperatures, with substantial warming expected during this period as zonal midlevel flow acquires subtle ridging by Monday, downstream of a potent shortwave trough entering the central plains. This leads to about a 6-12 degree warm-up on Sunday versus Saturday and another 4- 8 degree increase for Monday. By Monday night, a perturbation will be moving into the Great Lakes with an attendant surface low moving into the Saint Lawrence Valley on Tuesday. Models have trended north with the low's track and with the precipitation shield extending to its south. Most models barely have precipitation glancing the Poconos as the perturbation moves into the Northeast on Tuesday night, as large-scale lift is displaced well north of our area and the southwestward-extending cold front. Tuesday should be the warmest day of the extended downstream of the cold front, with highs approaching 60 near/southeast of the urban corridor. As the cold front moves through Tuesday evening, about a 15-degree drop in maximum temperatures should be expected for Wednesday. The next surface low will lift northeastward into the Great Lakes and adjacent southeast Canada by Thursday night, with isentropic lift downstream increasing sufficiently for widespread precipitation near/north of a developing baroclinic zone Wednesday night through Thursday night. Models vary with the timing of precipitation onset, ranging from as early as Wednesday night to as late as Thursday night. Temperatures may be cool enough at night for a wintry mix in the northern CWA, but in general, this would be another rain event for the area given the low's track north/west of the area. Looks like another broad surface high moves in later Friday into next weekend, with colder temperatures and another fairly lengthy dry period. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Mostly VFR conditions are expected. There is a small chance for fog to develop overnight, primarily along the coastal Plains including KMIV and KACY. If it does develop, MVFR visibility is possible, however the chance is too low to include in the TAFs at this time. Winds will be light and direction will be varying from northwesterly to southwesterly. Low confidence on the fog potential, but high confidence on other aspects of the forecast. Tomorrow...VFR conditions are expected. Southwesterly winds may get as high as 10 to 15 kt. High confidence. OUTLOOK... Saturday night through Wednesday: Mainly VFR. Light winds. There is a slight chance for rain Monday night, generally northwest of PHL, with lower CIGs possible. Moderate confidence. && .MARINE... Sub-SCA conditions are expected to continue through tonight and Saturday. Light snow will limit vsbys over much of the forecast waters to 2 miles or less through mid evening, but snow snow should clear out to the east by midnight. Southwest winds will develop on Saturday as surface high pressure shifts southeast and offshore. By late afternoon, wind gusts could approach 25 kt over the waters mainly north of Manasquan. Attm however there is not enough confidence to go with a SCA. OUTLOOK... Saturday night through Wednesday: Sub-advisory winds/seas expected. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...AMC/Franklin Near Term...AMC/Johnson Short Term...AMC Long Term...Franklin Aviation...AMC/Franklin/Johnson Marine...AMC/Franklin