634 FXUS61 KPHI 192029 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 329 PM EST Mon Dec 19 2022 .SYNOPSIS... High pressure will gradually build east from the Ohio Valley for the next couple of days. A significant storm system will develop well to the west and affect our weather Thursday and Friday bringing mainly rain with strong winds.Following that, arctic air and gusty winds will affect the weather for the upcoming holiday weekend. && .NEAR TERM /THROUGH TUESDAY NIGHT/... Clouds have had the upper hand today in many areas with mostly sunny skies only across Delaware and ern/sern NJ. The clouds have held the temperatures down a bit as well with mostly mid/upper 30s across the region as of 2PM. We do expect that the clouds will diminish through sunset and remain only across the NW most areas this evening. It will be another cold night with lows in the teens for the N/W and low/mid 20s elsewhere. Winds will be NW diminishing to less than 10 mph after sunset. Tuesday, the high pressure will move closer to the area and we will (hopefully) have the elusive sunny day for the Delaware valley and areas nearby. Highs are expected to reach the upper 30s/low 40s in most areas. Winds will be lighter than today, mostly NW at 5 to 10 mph. Tuesday night, high pressure moves overhead so clear skies and cold temperatures expected. Lows, like Mon night, will be in the teens N/W and 20s elsewhere. Light winds. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... Conditions remain tranquil for Wednesday as high pressure remains centered near the area. This will result in a mainly sunny day with temperatures that will still be a little on the cool side with highs mostly in the 40 to 45 degrees range. It will be a bit cooler (mid to upper 30s) over the southern Poconos and NW NJ. For Wednesday night, the high will retreat towards New England with skies clouding over ahead of the storm system that will affect the area for the end of the week. Expect lows mainly in the 20s, except 30s near the coast due to onshore winds. && .LONG TERM /THURSDAY THROUGH MONDAY/... A significant extratropical cyclone is forecast to develop in the midwest and rapidly intensify while tracking northeastward across the Great Lakes later Thursday into Friday. While modeling continues to feature some spread and variance in some specific aspects of the evolution of this system, generally speaking the weather that our region can expect has become fairly clear. While some portions of our area might see a little snow and/or freezing rain at the onset of precipitation on Thursday, generally we are looking rainy and windy weather for the bulk of our area late this week. Getting into the specifics, the high pressure centered near Maine early in the day will continue its retreat eastwards as it moves into the Canadian Maritimes. Meanwhile, deepening low pressure will move northward from Oklahoma towards Lake Michigan through the day. The arrival of precip looks to be during the daytime with still some uncertainty on exact timing, but most likely moving in west to east around late morning into the afternoon. The earlier it arrives in the day, the higher the chances for a brief period of snow or ice before the changeover to rain. But either way, any snow/ice accumulation will very little if any, and should be confined mainly to areas N/W of the urban corridor. We have our highest POPs Thursday night into Friday at which time the low will be continuing to rapidly deepen while moving north in response to a potent upper level disturbance and associated upper jet rotating around the base of the long wave trough. It is at this time (Thursday night into Friday) that moderate to heavy rain rates will be possible. The latest indications are for total amounts with the system to be a widespread 1-2+ inches so it's possible there could be some localized flooding issues but the big story looks to be the winds. We'll also have to keep an eye on the coastal water levels as we get closer, with at least some minor coastal flooding hard to rule out late Thursday or early Friday. Otherwise, the most impactful weather element with this system looks to be winds, as a strong southeast to southerly low-level jet will develop over our region Thursday night, followed by another surge of strong southerly winds aloft on Friday as the main area of low pressure and associated upper-trough passes by. Advisory-level winds (greater than 45 mph gusts) are certainly possible for portions of our area, especially toward the coast on Friday, when we may be in the warm sector of the storm and low-level mixing will be improved. An extremely sharp cold front will swing through at some point on Friday, with exceptional upper-height falls and cold air advection only aiding momentum transfer and continuing gusty westerly winds Friday night into Saturday. Very dry air moving in should quickly put an end to precipitation behind the cold front. Though we do have a mention of some snow showers behind the front late Friday, am not expecting much of that at this point. The cold air following the front may be the biggest story for our area associated with this storm for the holiday weekend, as a highly anomalous cold upper low bottoming out below 500 dm will drive arctic air into our area Friday night through the weekend. The main surface high will drop southward from the Plains to the Gulf Coast, so that area will see the brunt of the most anomalous cold. Still, our area will be well below normal with highs struggling to get out of the 20s across our region over the weekend, and lows in the teens, with some single digits possible in the coldest spots. The weather will at least be dry and partly to mostly sunny, but again, accompanied by brisk winds Saturday and probably still some breezes on Sunday afternoon. High pressure looks to build in to start next week bringing lighter winds with mainly clear skies and continuing cold temperatures. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight... Decreasing clouds and winds. VFR. Northwest winds mostly 5 to 10 kts after 00Z. High confid. Tuesday... VFR. Mostly FEW/SCT clouds but some BKN possible KABE/KRDG for the late morning/early afternoon. NW winds around 10 kts. High confid. Tuesday night... VFR. Mainly SKC. Light winds. High confid. Outlook... Wednesday...VFR with increasing clouds at night. North to northeast winds around 5 knots or less. High confidence. Thursday and Friday...Very Likely MVFR to IFR conditions, with strong and gusty southerly winds especially on Friday. LLWS possible. Rain most areas but some brief snow may occur early Thursday around ABE/RDG. Moderate confidence. Saturday...VFR. West winds 15 to 20 gusting 20 to 30 knots. Moderate confidence. && .MARINE... Earlier we extended the SCA flag for the lower Delaware Bay out a bit longer as the winds were slow to diminish. The SCA for the lower Bay and the SC flag for the southern Ocean zones will expire at 6 PM. The remaining zones will continue into the overnight hours and stop at 7 AM. sub-SCA conditions are expected Tue/Tue night. Fair weather is expected for the period. Outlook... SCA conditions increasing to gale force with strong southeast to southerly winds especially Thursday night into Friday. Winds diminish into Saturday but will still likely be at strong SCA levels. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ431- 452>455. Small Craft Advisory until 7 AM EST Tuesday for ANZ450-451. && $$ SYNOPSIS...Dodd/Fitzsimmons NEAR TERM...OHara SHORT TERM...AKL/Fitzsimmons LONG TERM...Dodd/Fitzsimmons AVIATION...Fitzsimmons/OHara MARINE...Fitzsimmons/OHara