Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 040212 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 912 PM EST Sat Dec 3 2016 .SYNOPSIS... High pressure will build across the area on Sunday. A disturbance will affect the area on Sunday night into early Monday, before high pressure briefly builds in again Monday night. Tuesday and Tuesday night, an area of low pressure will move into south central Canada, while a second passes to the south of our area as it moves offshore. A new low will form to our north as these two lows weaken then combine with each other. This low will strengthen to our north Thursday through Saturday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Low pressure just east of the Canadian Maritimes will continue to move offshore and depart tonight. Meanwhile, surface high pressure over the TN/OH Valleys will build east. Pressure gradient over the area will relax through this evening, and winds drop off fairly quickly to 5-10 MPH this evening. After midnight, winds diminish even further to 5 MPH or less. Strato CU streaming in from the NW will impact most of the western portions of the CWA with BKN-OVC skies at 4000-5000 feet for much of tonight. Otherwise, skies clear out. Going towards daybreak, skies become mainly clear. Temps this evening will slowly drop off, but it looks as if sometime between midnight and 6 am, skies should clear out enough and winds will diminish enough for strong radiational cooling conditions to develop. As a result, overnight lows will drop into the mid and upper 20s across the Poconos and northern NJ, and in the low 30s for most of NJ/PA. Temps along the urban corridor of I-95 and along the Atlantic coast, as well as the Delmarva, will drop into the mid 30s. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... The center of the high will move towards the Delmarva by Sunday morning, and then throughout the day, will move offshore. Meanwhile, low pressure to the west will develop and organize as it presses east. Sunday will be dry with no precip, but will expect mid and high clouds to increase during the afternoon hours. Highs on Sunday will be a few degrees short of normal. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... The high pressure retreats northward early Sunday evening before a weak surface trough and associated mid/upper disturbance approach the area. Low-mid level moisture and lift will increase across the area as this disturbance moves across the area overnight into Monday morning. We expect precipitation chances to increase from the southwest after midnight and spread northeastward through the overnight into Monday morning. It could be cold enough for some snow or sleet to mix in for the southern half/two-thirds of the area while the northern third of the area may stay snow for the entire time, and have the best chance to see accumulating snowfall. QPF amounts are relatively light, so we only expect around a half inch to one and a half inches at across the northern areas, with a little dusting elsewhere. As both the surface trough and the short mid/upper disturbance pass to our northeast during the day, precipitation chances will diminish by midday. Dry weather will then remain for the remainder of the afternoon and continue into Monday night as high pressure briefly builds across the area. This dry weather will only be temporary as the high pressure will be retreating during the afternoon ahead of an approaching storm system. An area of low pressure will be lifting through the northern Mississippi River Valley and into south central Canada, while another will be moving across the Appalachians to our south. As the southern low lifts northward, we expect enhanced moisture and lift to spread across our area as several short waves aloft move across the area. Low clouds and precipitation chances will increase from south to north late in the day into the evening, and continue during the overnight. By Wednesday morning, the southern low will have moved offshore and will be east of the area. However, we may still be under the influence of a surface trough associated with this low through the day Wedensday into Wednesday night. As a couple of short wave/vorticity impulses slide across the area, we could continue to have low clouds and precipitation affect the area. By early Thursday, the low pressure across southern Canada and the low offshore weaken. They then combine to our north during the day Thursday into Thursday night, before strengthening and slowly lifting northward Friday into Saturday. A strong west to northwest flow will develop across the area. With steep lapse rates across the northern portions of the area and enhanced low- mid level moisture forecast to remain, especially across the northern portions of the area and farther north, we could continue to see snow or rain showers Thursday through Friday, and possibly continue into Saturday. One thing for sure for the end of the week, regardless of precipitation, is it will get cold and windy for the latter portion of Thursday, but especially Friday and Saturday. Wind chills will likely get into the single digits to lower teens for many areas overnight each morning Thursday night through Saturday morning when the temperatures are the lowest. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions with BKN-OVC ceilings at 4000-5000 FT through this evening. Ceilings will scatter out late tonight. FEW clouds at 4000- 5000 FT expected Sunday morning. Surface winds 15-20 KT with 20-30 KT gusts will diminish quickly this evening to less than 10 KT, and then winds diminish to 5 KT or less late tonight. W-NW winds increase to 5-8 KT Sunday morning. OUTLOOK... Sunday night-Monday...VFR early, becoming MVFR or IFR overnight and continuing into Monday. Snow possible for the northern half/two- thirds of the area, with rain for the southern areas. Precipitation ends by midday, but clouds likely to linger through the day. Monday night...Conditions may improve to VFR for a period overnight. Tuesday-Wednesday...Conditions lowering to MVFR/IFR during the morning with periods of rain/fog/drizzle likely. Snow also possible for northern areas. Winds likely become gusty 15-20 knots out of the northwest late in the day. Wednesday night...Steady rain likely ends during the evening, but lower clouds may linger into the night. Gusty northwest winds 20-25 knots possible. Thursday...Generally VFR, but scattered showers are possible during the day which may temporarily lower conditions. Gusty northwest winds 25-30 knots. && .MARINE...
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SCA conditions will continue on the ocean waters through 06Z. Tranquil conditions then expected through Sunday as high pressure builds in from the west. Sunday night-Tuesday...Sub-Small Craft Advisory conditions expected. Tuesday night-Wednesday...Small Craft Advisory winds likely, with conditions approaching gale force. Wednesday night...Winds likely drop below advisory levels, but seas could remain above 5 feet. Thursday...Northwest winds increase to Small Craft Advisory levels during the day.
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 1 AM EST Sunday for ANZ450>455.
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