Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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920 FXUS61 KPHI 061146 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 646 AM EST Thu Feb 6 2025 .SYNOPSIS... A low pressure system and its associated fronts cross the region today bringing a mixed bag of wintry precipitation to the area. High pressure briefly returns late tonight into Friday before another low pressure system passes through late Saturday into Saturday night. High pressure returns temporarily on Sunday into Monday before another system approaches the region for the Tuesday and Wednesday timeframe. && .NEAR TERM /THROUGH TONIGHT/... Warm air advection is underway for portions of the area, and most of Delmarva and southeast New Jersey have risen above freezing and freezing rain changed to plain rain. The exception is the area in/around Wilmington. Temperatures remain around freezing with freezing rain still being reported at KILG. Will continue the Winter Weather Advisory that is in effect for these areas until 8 am. For the I-95 corridor and areas north, the Winter Weather Advisories remain in effect as the wintry mix of snow, sleet, and freezing rain continues over the area. Low pressure moves across the region, and then snow and sleet will eventually change to sleet and freezing rain, then a period of freezing rain, then plain rain from south to north through the morning hours. Freezing rain may hold on in the southern Poconos and northern New Jersey into this afternoon before tapering off. Overall, snow and sleet accumulations will generally average 1/2 to 1 inch over the Delaware Valley, including Philadelphia, and southern New Jersey, and minimal amounts over Delmarva. For the Lehigh Valley, northern New Jersey, and the southern Poconos, snow and sleet amounts will average 1 to 2 inches, with localized amounts up to 3 inches in the higher elevations of northern New Jersey. Ice accretions from freezing rain will generally range from 0.10 to 0.20 inches. The area of 500 to 2500 J/kg of MUCAPE continues to spread into Pennsylvania, and even into portions of New York. Most of the lightning has ended as it moves through Pennsylvania, so really not expecting much more than a rumble of thunder or two later this morning, should this MUCAPE hold together. Rain gradually tapers off through the early afternoon hours as that secondary low passes through New Jersey. Once rain ends, it looks to remain cloudy and dreary with patchy fog. Highs will range from the mid and upper 30s over the southern Poconos, northern New Jersey, and the Lehigh Valley, and otherwise mostly in the low to mid 40s. Highs may get into the low 50s in southern Delmarva. Cold front moves across the region late tonight. It will remain cloudy with patchy fog until the front passes through the region and cooler and dryer air can filter into the region, likely not until after midnight tonight. A few showers are possible over Delmarva and southern New Jersey with its passage. Lows tonight will range from the upper 20s in the southern Poconos and mostly in the low 30s in northern New Jersey and the Lehigh Valley. Lows will be in the mid and upper 30s for the Delaware Valley, southern New Jersey, and Delmarva. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... High pressure briefly builds into the area on Friday before shifting overhead late Friday night and offshore early on Saturday. Overall, expecting pleasant weather conditions across the area with a mix of sun and clouds. Winds will be quite gusty though, as a secondary dry cold front sweeps across the region late Friday morning. Winds will occasionally gust upwards of 30-35 mph during the afternoon. High temps should top out in the mid 30s to mid 40s for most, and possibly pushing low 50s across the Delmarva. Tranquil conditions continue into Friday night with an increase in clouds overnight and winds diminish. Low temperatures are expected to fall into the teens/20s for Friday night. Attention then turns to the Saturday into Sunday timeframe as the next low pressure system takes aim at the area as high pressure shifts offshore early on Saturday. An area of low pressure originating from the Central Plains will traverse east while strengthening over the Ohio River Valley by Saturday evening. Low pressure will then translate its energy into a developing coastal low off the Mid-Atlantic coast on Saturday night before continuing northeast off the New England coast on Sunday. For now, general consensus amongst forecast guidance is that this system is trending slightly colder, meaning more snow is possible! As precipitation begins on Saturday afternoon, most locales should encounter a period of light snow as temperatures will be below or around the freezing mark heading into Saturday night. However, a modest ramp-up in warm air advection is anticipated to occur later Saturday night as a warm nose aloft progresses northward. This will result in a gradual change over to sleet and/or freezing rain from south to north. Point forecast soundings suggest that freezing rain may be favored over sleet so have included this potential in the forecast. As temperatures warm overnight throughout the atmospheric column, a changeover to plain rain is expected across the Delmarva and most of the Coastal Plain. However, frozen precipitation may hang on for the duration of the event especially up in the higher elevations of the Lehigh Valley, Poconos and northern New Jersey. The timings and specifics of the changeover are not yet set in stone, but the greatest potential for a prolonged period of frozen precipitation lies over the usual spots of the higher terrain areas. In terms of amounts, the current forecast calls for 0.40-0.70" of liquid QPF. Breaking this down into snow/sleet totals, anticipate a C-1" for the northern Delmarva and much of the I-95 corridor including the Philadelphia metro. Just north of the I-95 corridor up to and including the I-78 corridor, expecting 1-3". Once north of the I-78 corridor and especially north of I-80, amounts upwards of 3- 5" are possible. There will also be freezing rain accretion over most of the area, but amounts should generally range from a T-0.1" (locally higher). Considering this, Winter Weather headlines will likely be needed within the next 24-48 hours. Low pressure and precipitation are anticipated to exit the region by Sunday morning. Some leftover rain/snow showers will be possible through the morning, especially further north and east. However, high pressure will gradually build in from the west late in the day, so Sunday does appear to be mostly dry during the afternoon. High temps will be quite seasonable under a mix of sun and clouds. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... Little changes were made to the long term period as attention was primarily focused on the system in the short term period. Signals continue amongst both deterministic and ensemble guidance toward yet another winter storm towards somewhere between the Monday night and Wednesday timeframe. Although this is still roughly 5-6 days away, there is somewhat a higher confidence level with this system bringing wintry weather to the region. The 01Z NBM probability of 4+ inches of snow ending by the end of the day on Wednesday is in the ballpark of 40-60%. While a lot can change between now and the beginning of next week, the general consensus of the long term forecast is for Sunday night and Monday being mostly dry. In terms of the wintry precipitation, it may begin as early as Monday night and lasting as late as Wednesday. Once timing becomes more certain, this timeframe will be constricted. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...MVFR/IFR, lowering to IFR/LIFR as the morning progresses. A wintry mix of SN/PL/FZRA at KILG/KPHL/KPNE/KTTN/KABE/KRDG will eventually change to RA. For KMIV/KACY, precip is already RA. RA ends by this afternoon, but IFR/LIFR conditions will remain in fog and stratus. E-SE winds 5 to 10 kt, becoming light and variable this afternoon, then W 5 to 8 kt late. Low confidence. Tonight...IFR/LIFR conditions initially in fog and stratus, improving to VFR after 06Z, but probably not until closer to 12Z. W winds less than 10 kt. Moderate confidence overall. Outlook... Friday through Friday night...VFR. No significant weather expected. Saturday through Saturday night...Sub-VFR conditions likely. Periods of snow gradually changing over to a wintry mix and rain. Sunday through Monday...Mainly VFR. No significant weather expected. && .MARINE... Although widespread sub-Small Craft Advisory conditions are expected today, there may be a few gusts to 25 kt on the ocean waters late this afternoon, and seas may build to 5 feet. At this time, it does not look like these conditions will be frequent enough nor widespread enough to warrant a SCA. E-SE winds generally 15 to 20 kt will slacked by mid-afternoon before turning SW 10 to 15 kt with gusts up to 20 kt late this afternoon and most of tonight. Winds become W around 10 kt late tonight. Seas build to around 5 feet tonight on the ocean. SCA remains in effect for tonight for the ocean waters. Outlook... Friday...Lingering SCA conditions possible early on Friday due to wind gusts up to 30 kt and seas around 5 feet. Saturday through Saturday night...No marine headlines expected. Sunday...A period of SCA conditions likely as winds gust up to 30 kt and seas approach 5 feet. Sunday night through Monday...SCA conditions may briefly linger into Sunday night, but for the majority, no marine headlines are expected. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 1 PM EST this afternoon for PAZ060>062-101>103-105. Winter Weather Advisory until 10 AM EST this morning for PAZ070-071-104-106. Winter Weather Advisory until 3 PM EST this afternoon for PAZ054-055. NJ...Winter Weather Advisory until 8 AM EST this morning for NJZ016- 021>023. Winter Weather Advisory until 1 PM EST this afternoon for NJZ001-007>009. Winter Weather Advisory until 10 AM EST this morning for NJZ010-012-013-015-017>020-027. DE...Winter Weather Advisory until 8 AM EST this morning for DEZ001>003. MD...Winter Weather Advisory until 8 AM EST this morning for MDZ012- 015-019-020. MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EST Friday for ANZ450>455. && $$ SYNOPSIS...DeSilva/RCM NEAR TERM...MPS SHORT TERM...DeSilva LONG TERM...DeSilva/Hoeflich AVIATION...DeSilva/MPS MARINE...DeSilva/MPS