099 FXUS61 KPHI 121349 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 849 AM EST Tue Nov 12 2019 .SYNOPSIS... An arctic front will cross our region this morning, then high pressure builds in during Wednesday before shifting offshore Thursday. A cold front moves through Friday night with high pressure building in from the northwest Saturday into Sunday. Meanwhile, low pressure develops off the southeast coast Saturday then it tracks northeastward across the western Atlantic over the weekend and early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Cold front is now moving through the Delaware Valley and Delmarva areas. Rain is moving across the region ahead of that front. Winds gusts over 30 mph occurring with and behind the front. With temperatures out ahead of the front well above freezing, expecting the vast majority of the precip to fall as rain. However, the front should be through the I-95 corridor by lunchtime, and off the coast by late afternoon. Behind the front, temperatures drastically drop off, and will fall into the 20s in the southern Poconos, the lower 30s north and west of the Fall Line, and in the mid and upper 30s across southern New Jersey and Delmarva. Temperatures continue to fall late in the afternoon. Watching model trends, most of the precip should be offshore before the sub-freezing temperatures overspread the region. Some wet snow is down to Philly, but confidence is low that it would occur, and impacts would be minimal. However, the exception will be the far northern zones of the southern Poconos and far northern New Jersey. Here, rain will change to snow before ending, but snowfall totals should be under an inch. The issue of concern would be any lingering water on roads from previous rainfall freezing. Northwest winds increase to 15-20 mph with 25-35 mph gusts, with the strongest winds to the north. Wind chills later today will drop into the single digits in the southern Poconos and teens north and west of the Fall Line. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... Arctic high pressure builds in from the north and west tonight. Northwest winds this evening will continue to average 15-20 mph with gusts to 25 mph, diminishing a bit after midnight, then to 5-10 mph prior to daybreak Wednesday. A frigid air mass with the potential for record breaking low temperatures will be in place tonight with lows ranging from 10-15 in the southern Poconos and far northern New Jersey, and otherwise in the teens and low 20s. Minimum wind chills tonight will range from zero to five below in the far northern zones, and in the single digits to low teens otherwise. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Summary...Very cold to even potentially record cold to start Wednesday (and Thursday) with a little warming during the day, then the airmass moderates some Thursday and especially Friday before cooling takes place Saturday. Milder air looks to arrive for early next week, however a storm system looks to be lurking offshore. Synoptic Overview...A strong upper-level trough lifts out of the East Wednesday with the mid level flow turning more zonal, then a short wave trough from the Midwest to the central Mississippi Valley pivots eastward Wednesday night and Thursday. This feature slides across the East later Friday as a closed low amplifies and shifts southward some across eastern Canada. The latter shifts across the Northeast into Saturday with a ridge building across portions of the western Atlantic, however a cutoff low looks to develop off the southeast coast over the weekend and into early next week. A surface low tied to this is forecast to slowly track northeastward into early next week. For Wednesday...As a strong upper-level trough exits the Northeast, the center of arctic high pressure builds over our area during the afternoon and at night. This will result in a very cold day with even record cold possible to start the day, then temperatures only warming into the 30s for most during the afternoon. The strongest breeze should be during the first half of the day, with wind chill values starting out in the 5-10 degree range (down to zero or just below in the Poconos). The airmass is forecast to be very dry, given its arctic source, and with surface high pressure building in during the course of the day the winds will ease up. While some flurries or even an isolated snow shower is possible early across mostly the Poconos, this should end quickly due to the very dry air along with increasing subsidence. As the surface high slides right over our area in the evening before shifting more to our northeast overnight, a very cold night is in store due to light/calm winds, limited cloud cover and a very dry airmass. This could result in some temperatures dropping to near record territory. For Thursday and Friday...A very cold start Thursday with even some record lows possible, then some warming in the afternoon. A short wave trough is forecast to slide eastward from the Great Lakes region Thursday to New England Thursday night, with a clipper system at the surface tagging along with it. This will toss a weak cold front across our area Friday night. The main warm air advection and therefore lift is focused well to our north therefore no precipitation is expected with it as of now. However, energy diving across the southern states Thursday is forecast to close off as is nears the southeast coast. This will induce surface low pressure development along a lingering baroclinic zone. Some energy and forcing ahead of this feature may try and produce some light precipitation late Thursday night into Friday across southeastern New Jersey and portions of Delmarva. This is less certain given weaker forcing this far north, with the main focus farther south closer to the closed low and developing surface low. For now, kept some low PoPs in for portions of the aforementioned area. The thermal profiles should be warming enough for mainly rain, although this may have to battle some lingering mid to low level dry air before dew points recover more. Given enough warm air advection, most places should warm into the lower 50s Friday afternoon despite some increase in cloud cover. For Saturday through Monday...The evolution of northern and southern stream energy becomes a bit more uncertain, however overall strong high pressure slides by to our north while a closed low near the southeast coast Saturday drives a surface low. The forecast challenge is the timing and also how much protection does our area get from the surface high as it gradually departs. Our region may get brushed by the storm as it tracks northeastward across the western Atlantic, however a gusty northeasterly wind (especially closer to the coast) looks certain given the pressure gradient forecast. We will continue with some slight chance to low chance Pops given the uncertainty especially later Sunday through Monday. The airmass should moderate some during the weekend and early next week, however this could be tempered some by the strengthening onshore flow, if more precipitation ends up occurring and if the system is even slower in moving further away. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR, lowering to MVFR with a chance for IFR in rain showers this morning. For KRDG/KABE, rain may briefly mix with and change to snow before tapering off by noontime. VFR this afternoon. SW winds 5-10 kt, becoming NW 15-20 kt with 20-30 kt gusts after 12Z for KRDG/KABE, after 15Z for KTTN/KPNE/KPHL/KILG, and after 18Z at KMIV/KACY. Tonight...VFR/SKC. NW winds 15-20 kt with gusts up to 25 kt, becoming 10-15 kt after midnight. OUTLOOK... Wednesday...VFR. Northwest winds 10-15 knots, then becoming light and variable at night. High confidence. Thursday...VFR, however MVFR ceilings are possible late at night mainly at ACY and MIV. Light and variable winds becoming southerly around 5 knots, then light and variable at night. Moderate confidence. Friday and Saturday...Mainly VFR ceilings. West to northwest winds 5- 10 knots Friday turning northerly Friday night, then northeast 5-15 knots Saturday. Low confidence. && .MARINE... Today...Decided to issue the Gale early with strong gusts occurring on the inland stations with the front and decent cold air advection expected to promote excellent mixing today. A shot of gales with the front and perhaps a lull (SCA gusts) before stronger gusts returning this afternoon. G35 to 40 kts expected during the period. Tonight...Gale force winds for most of the night, diminishing to 15- 20 kt with gusts up to 30 kt by daybreak Wednesday. Ocean seas 4-6 feet, and waves on Delaware Bay 2-4 feet. OUTLOOK... Wednesday...The conditions are anticipated to be dropping below Small Craft Advisory criteria by the early afternoon, then continue to subside at night. Thursday and Friday...The conditions are anticipated to be below Small Craft Advisory criteria much of the time, however winds increase Friday night and an advisory may be needed. Saturday...Small Craft Advisory anticipated. Northeast winds are forecast to gust to 30 knots, however a period of gale force gusts are possible. && .CLIMATE... Arctic air pours across the entire area by later today and sticks around into Thursday. This may lead to some record lows. Here are the record low temperatures for Wednesday and Thursday: Climate Site Nov 13 ------------ ------ Allentown 18 in 1996 Atlantic City 22 in 2001, 1996, and 1995 Atl. City Marina 24 in 1920 Georgetown 21 in 1986 Mount Pocono 12 in 1911 Philadelphia 24 in 1986 Reading 21 in 1976 Trenton 23 in 1920, 1911 Wilmington 18 in 1911 Climate Site Nov 14 ------------ ------ Allentown 17 in 1986 Atlantic City 15 in 1986 Atl. City Marina 23 in 1874 Georgetown 22 in 1986, 1950 Mount Pocono 5 in 1905 Philadelphia 19 in 1986 Reading 16 in 1986 Trenton 20 in 1905 Wilmington 20 in 1986, 1911 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 AM EST Wednesday for ANZ430-431-450>455. && $$ Synopsis...Gorse Near Term...MPS/PO Short Term...MPS Long Term...Gorse Aviation...Gorse/MPS Marine...Gorse/MPS/PO Climate...