395 FXUS61 KPHI 142332 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 732 PM EDT Sun Oct 14 2018 .SYNOPSIS... High pressure off the mid-Atlantic coast this evening will move farther out to sea tonight and Monday. Meanwhile low pressure will move from the Great Lakes northeastward across southeast Canada, and a trailing cold front will cross our area Monday night. A re-enforcing cold front will arrive on Wednesday, followed by strong high pressure on Thursday. The high should move offshore on Friday, followed by yet another cold front on Saturday, then more high pressure for Sunday. Except for Monday, temperatures will be near or below normal, and any rainfall relatively light. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 715 pm update: I updated winds and sky cover to match current observations. The main change was to make conditions cloudier this evening, as current satellite imagery does not suggest much progress in the clearer skies to our north moving southward into the CWA. Current temperatures were OK, but I suspect some adjustments to hourly temperatures will be needed once nocturnal cooling sets in, particularly if sky conditions become somewhat more variable. Previous discussion... Some mid-level shortwave energy passes through the region late this afternoon and through this evening. Most of the area is quite dry, but there may be some sprinkles (no PoP/no QPF) until sunset. Surface high pressure centered over the area moves offshore this evening, and continues to move east into the western Atlantic during the overnight hours. Behind the departing high, a warm front lifts north towards the region. Meanwhile, a cold front over the Great Lakes and Midwest continues to push east, and will move into the Ohio Valley by daybreak Monday. Most of the night should be dry, but clouds will thicken and lower through the overnight. Showers move into western zones well after midnight, and may approach the I-95 corridor by daybreak. Rainfall will be light, generally 1/10" or less. Lows tonight will range from the low to mid 40s north and west of the Fall Line, and will be in the low to mid 50s in southern NJ, southeast NJ, and Delmarva. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... Warm front lifts north Monday morning, and showers taper off by midday or so. behind the warm front, a relatively warm and humid airmass spreads into the region with highs in the mid and upper 60s for areas north of I-195, and in the low to mid 70s for southern NJ, southeast PA, and Delmarva. Surface dewpoints will climb well into the 60s, and may even approach 70 in southern Delmarva and southeast NJ. The cold front moves through NY/PA during the day, and moves into western portions of the forecast area by evening. Showers develop again in the afternoon and evening. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... The extended forecast period features long-wave trofiness over the eastern US with a couple of fairly pronounced shortwave digging into the trof at midweek and over the coming weekend. The pattern leads to below normal temps but not a lot of precip. The storm center track remains over Canada for now. A cold front is forecast to cross the forecast area Monday evening and be well to our south by Tuesday morning. Rain should also end NW to SE during the evening, although the forecast maintains a chance of showers overnight mainly south/east of PHL. Colder air will move in on gusty NW winds, overnight lows ranging from the 40s will north/west of PHL to the low or mid 50s elsewhere. Zonal flow aloft and and a weak ridge of high pressure at the surface should bring fair but rather cool weather for Tuesday. A low pressure wave on the frontal boundary still to our south could bring a chance of rain to southern DE and vicinity Tuesday night or Wednesday. On Wednesday a fast moving shortwave trof diving down from Canada will bring a re-enforcing shot of cool air into the region on gusty NW winds. Little if any precip is expected with the surface cold frontal passage, however some freezing temps are possible in the Poconos by Thursday morning. High pressure builds to our south Thursday into Thursday night, before shifting offshore Friday. This is expected to provide dry weather for the end of the work week. However, this dry forecast is not expected to last long as a cold front is likely to affect the area next Saturday. There are some timing, placement and strength differences with the different features, but all the long term guidance are indicating a chance of showers next Saturday. High pressure is forecast to build in behind the cold front on Sunday, bringing dry but cool weather. && .AVIATION /23Z SUNDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. This evening...VFR with mid-to-high cloudiness. Winds becoming light and variable. High confidence. Overnight...CIGs gradually deteriorating to MVFR (and possibly IFR near daybreak). Showers will be moving in from the southwest, though timing their onset is challenging. Currently expect showers to increase after 06Z and become more widespread after 10Z. VSBYs will likely deteriorate to MVFR at times once the showers arrive. Light/variable winds. Moderate confidence. Monday...Prolonged sub-VFR likely with showers in the morning. CIGs may remain IFR or low MVFR through early afternoon before improving to high MVFR or even VFR by late afternoon. Anticipating a break in the showers during the afternoon before another round of showers moves in from the west during the late afternoon (ore even early evening). Winds becoming south to southwest around 10 kts with occasional gusts to 20 kts possible in the afternoon. Moderate confidence. OUTLOOK... Monday night...MVFR or IFR conditions with showers possible early, then improving conditions overnight behind a cold front. Northwest winds may gust 20-25 knots. Tuesday-Tuesday night...VFR conditions expected. West winds around 10 kt. Wednesday-Wednesday night...VFR conditions expected. West to northwest winds may gust 25-35 knots, with the strongest gusts Wednesday afternoon. Thursday...VFR conditions expected. Northwest winds may gust 15-20 knots. Friday...VFR conditions expected. Southwest winds may gust 15-20 kt. && .MARINE... Sub-advisory winds/seas are expected this evening, but conditions will worsen quickly by tomorrow morning. South to southwest winds will increase to 15 to 25 kts with gusts approaching/exceeding 30 kts by afternoon. Cannot rule out the potential for gales on the Atlantic waters and am considering upgrading the small craft advisory to a gale warning for the New Jersey coastal waters. Delaware Bay should remain solidly within advisory levels during the day, with the Delaware Atlantic waters likely also sub-gale force. Seas will build quickly to 4 to 6 feet by Monday afternoon (generally less than 4 feet on Delaware Bay). OUTLOOK... Monday night...Small Craft Advisory in effect with increasing winds and building seas. A few gusts to near gale force are possible. Tuesday...Small Craft Advisory conditions likely to continue into Tuesday. Tuesday night...Sub Small Craft Advisory conditions expected. Wednesday...Winds increasing to at least Small Craft Advisory conditions, approaching gale force during the afternoon. Wednesday night...At least Small Craft Advisory conditions likely to continue. Thursday...Conditions expected to fall back below advisory levels by Thursday morning. Friday...Sub SCA Conditions are expected. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 8 AM Monday to 6 AM EDT Tuesday for ANZ430-431-450>455. && $$ Synopsis...AMC Near Term...CMS/MPS Short Term...MPS Long Term...AMC Aviation...AMC/CMS Marine...AMC/CMS