269 FXUS61 KPHI 181552 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1052 AM EST Mon Feb 18 2019 .SYNOPSIS... Low pressure will pass through the region today, with High pressure building back in from the north and west on Tuesday. High pressure will move away from the area Tuesday night with a complex area of low pressure moving through the Northeast Wednesday through Thursday. High pressure builds in from the north and west to close out the week. Low pressure will likely impact the area next weekend. && .NEAR TERM /THROUGH TONIGHT/... The Winter Weather Advisory has been taken down as most of the precipitation has ended across the area. It's possible that a little drizzle or perhaps some freezing drizzle may still be occurring up north, but it will not last much longer. There will also be some icy patches with some glaze occurring last night, so still exercise caution it out this morning. Clearing will start to occur as the precip departs and much drier air moves into the region. Skies may remain cloudy through at least mid day but expect some sun to start peeking out this afternoon, especially across our southern areas. Winds pick up in the westerly flow and may become quite gusty through the afternoon and into this evening. Wind gust up around 25 to 30 mph with some gusts around 35 mph possible across the forecast area. Temperatures will gradually rebound today and should start to war appreciably toward this afternoon. Expect highs to reach into the upper 40s to lower 50s across Delmarva, mid to upper 40s through the Delaware Valley and along the I-95 corridor, and in the upper 30s to lower 40s across the Lehigh Valley, southern Poconos and northwestern New Jersey. && .SHORT TERM /TUESDAY/... High pressure will start to build into the region tonight and we are expected to stay dry. Skies will clear out overnight and we should radiate well, especially once the winds start to die down. Overnight lows will be cold with teens across the northern zones and 20s every where else. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Big Picture The large-scale synoptic pattern will be more or less static through the long term period with longwave troughing over the western US and a mid-lvl ridge over the sub-tropical Atlantic. Various shortwave disturbances will eject from the western trough and generally track north and west of the area due to the mean ridge position. An upper level jet will generally be centered just north of the area however it will meander at times into favorable locations to enhance ascent over the forecast area. The sfc.low track to the northwest of the area will result in precipitation events being largely driven by ejecting shortwaves interacting with moist isentropic lift advection to the SE of the low center. Dailies: Tuesday: High pressure will reside over or just north of the forecast area on Tuesday with quiet sensible weather as a result. As the high moves overhead northerly winds should be noticeably weaker than Monday. A fairly cool airmass will keep temps about 5-10 degrees below normal. Cloud cover increases from S-N Tuesday night into Wednesday morning as flow aloft backs more southwesterly advecting moisture into the area. Wednesday: The main precipitation event of the long-term looks to impact the area Wednesday as shortwave energy interacts with increasing isentropic lift and moisture advection ahead of a sfc.low over the Midwest. Guidance has slightly slowed the onset of precipitation with precipitation now arriving in Delmarva early Wednesday morning and then spreading northeast...finally reaching NW NJ/the Poconos by early Wed afternoon. As is typical with overunning events ptype will be challenging with typical model biases coming into play (e.g. the GFS scours out the low- lvl cold air too quickly, while the NAM likely keeps the sfc. too cold). Additionally there is quite a bit of spread among guidance over how much a secondary low developing near/south of the area Wed PM will impact the kinematic and thermal fields. Currently it appears most areas (outside of maybe far southern Delware) will experience all snow with the initial burst of precipitation Wed AM, with a gradual (SW-NE) transition to mixed precipitation then finally to rain Wednesday afternoon into Wednesday night. Naturally the speed in which this transition occurs will have significant impacts on snow and ice accumulations. The current snow accumulations represent a compromise between the GFS which is both the fastest to warm the column and also has the lowest QPF, and the NAM which has the highest QPF and the coldest profiles. It must be emphasized the uncertainty associated with these amounts is higher than usual both due to spread in ptype forecasts and spread in QPF forecasts. Thursday/Friday: By Thursday AM the sfc. warm front will have passed through the entire area with any lingering precipitation being all rain. The area will dry out fairly quickly into Thursday afternoon as the cold/occluded front passes with brisk but not particularly strong westerly winds in its wake. Friday looks generally quiet as high pressure builds to the north of the area. Expecting seasonable temperatures although some weak mid-lvl waves may result in some passing cloud cover. Saturday/Sunday: The next storm system takes aim at the area this weekend with plenty of uncertainties regarding detail. At this time the signal is for another warm advection driven storm, with little to no CAD in place beforehand. Consequently am currently leaning on a primarily rain event Saturday PM into Sunday AM but there is still some uncertainty. && .AVIATION /16Z MONDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Improving conditions expected into the afternoon. VFR after that with gusty W to NW wind developing. Gusts up to 30 knots possible by late afternoon. Tonight...Mainly VFR conditions expected. Northwest winds around 10 to 15 knots early will drop down to around 10 knots or less overnight. High confidence.Outlook... Outlook... Tuesday...VFR. N/NW winds 10 kt or less. High confidence. Tuesday night through Wednesday night...Cloud cover increasing Tuesday night with VFR conditions transitioning to MVFR and then IFR Wednesday morning into early afternoon as snow arrives. Precipitation type will transition to wintry mix and then rain from south to north Wed afternoon/evening. East to southeast winds around 10 knots or less. Low confidence with respect to precipitation type. Thursday...MVFR or lower conditions in the morning, improving to VFR late in the day. West to northwest winds around 10-15 knots. Moderate confidence. Friday...VFR. N winds 5-10 kt. && .MARINE... Small Craft Advisory is in effect for all waters from this afternoon through tonight. Winds will be generally light this morning before starting to pick up out of the west/northwest by the afternoon. A fairly tight pressure gradient will allow winds to gust above 25 knots for this afternoon and evening before the gradient starts to relax overnight. Seas around 2 to 4 feet this morning will build to 3 to 6 feet this evening. Seas will subside back down to 2 to 4 feet overnight. night. Outlook... Tuesday...Sub-SCA conditions with Seas generally around 2 to 4 feet. Wednesday through Wednesday night...Increasing easterly winds Wed PM with gusts > 25 knots possible. Transition from snow, wintry mix to rain expected. Thursday...Seas building to SCA levels by Thursday AM on ocean waters with winds shifting to the West/NW by Thursday afternoon. Friday...Seas/winds dipping below SCA by Friday morning with sub-SCA conditions prevailing through Saturday. && .TIDES/COASTAL FLOODING... High tide has passed on the Atlantic waters and in Delaware Bay, and flood waters are beginning to recede. Therefore, the coastal flood advisory will be allowed to expire at 11 am. It appears as though at least some spotty minor flooding may occur with the morning high tides into the mid week period. We will continue to monitor the water level trends. The full moon occurs on Tuesday. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...Coastal Flood Advisory until 11 AM EST this morning for NJZ012>014-020-022>027. DE...Coastal Flood Advisory until 11 AM EST this morning for DEZ002>004. MD...None. MARINE...Small Craft Advisory until 6 AM EST Tuesday for ANZ430-431- 450>455. && $$ Synopsis...Carr Near Term...Meola/O'Hara Short Term...Meola Long Term...Carr Aviation...Carr/Meola/O'Hara Marine...Carr/Meola Tides/Coastal Flooding...CMS/Iovino/Meola