Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 240529 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1229 AM EST Fri Nov 24 2017 .SYNOPSIS... High pressure currently over the region will move slowly offshore on Friday as a cold front approaches the region from the west. This cold front will pass through the region on Saturday. Another area of high pressure will build into the region for the early part of next week then move offshore with the approach of another cold front by the middle of next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... High pressure located over Virginia this evening will continue to influence our weather overnight. An area of high based stratocumulus was approaching from western and north central Pennsylvania this evening. However, the guidance continues to suggest that it will erode before reaching our region. As a result, we are expecting a mostly clear sky. The light wind will allow for nearly ideal radiating conditions. We are anticipating low temperatures to be mostly in the 20s with some upper teens readings up north and in the interior of southern New Jersey. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... Sunny. Milder in the afternoon after a chilly start. Light wind trending south to southwest in the afternoon. Max temps generally within 2f of normal. Due to poor mixing despite a sunny day and after early morning chill...think PHL max will be 51. There may be a signal developing in some of the guidance with a long dry spell apparently developing. High pressure and radiation cooling options at night may verify temps lower than guidance. GGEM seems to have that idea. This is due to lack of mixing except a day before a frontal passage (gradient sw flow). Daytime max`s may not be as high GFS guidance suggests...in part because of short days. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Friday night through Saturday night: High pressure will continue to move offshore Friday night giving way to an approaching cold frontal boundary. This cold front will move through the area on Saturday. Overall, timing remains consistent on various models and ensembles for an afternoon/ evening frontal passage. Enough lift and moisture should be present for a few spotty rain showers, primarily in the afternoon hours. Temperatures Saturday morning may be close enough to freezing in the southern Poconos and NW NJ for a freezing rain concern. Right now any precipitation is expected to hold off till mid-morning when it warms well above freezing. Precipitation looks very light, only a few hundredths at best. A few southerly wind gusts in the afternoon around 15 mph are possible before the frontal passage. Northwest flow on the backside of the front could also kick off some sprinkles and flurries toward sunrise that could be enhanced where the elevation is highest (southern Poconos and NW NJ). Sunday through Thursday: A fairly strong push of cold air advection will occur behind the front. This will lead to another period of more winter like temperatures across the region with stronger northwest winds, gusting perhaps to 25 mph on Sunday. The northwest flow may also allow for some moisture to transport southeast off of the Great Lakes. The moisture could be enhanced by the higher terrain. Highs Sunday and Monday will generally be in the 40`s with overnight lows will be in the 20`s and 30`s. Conditions are expected to clear later Sunday and Monday as the northwest flow weakens and high pressure builds into the region. We should see a fairly quick rebound Tuesday and Wednesday with temperatures into the 50`s, maybe 60 Wednesday? Right now the forecast stays close or a little above to the mean of the ensemble guidance on Tuesday and Wednesday. A majority of ensemble guidance does indicate a pattern favorable for a period of warm weather. However, the 12z OP EC 11/23 does indicate a stronger push of cold air advection from the northwest Monday into Tuesday which would lead to lower temperatures. The OP EC looks like an outlier solution at this time. Some uncertainty is also present with the speed of a cold frontal boundary moving toward the area sometime Wednesday or more likely Thursday of next week. For now, went middle of the road between the GFS and ECMWF and brought in a chance of showers on Thursday. This has trended a little slower the last couple of model runs. After a warmer Wednesday, temperatures Thursday should cool a few degrees back closer to normal. Happy Thanksgiving from all of us here at the National Weather Service in Mount Holly! && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...VFR conditions with a mostly clear sky. A light and variable wind. High confidence in all aspects of the forecast. Friday...VFR conditions with a clear sky. Wind will settle out of the southwest less than 10 KT through the day. High confidence. OUTLOOK... Friday night: VFR, westerly winds becoming southwesterly but staying at 10 knots or less. High confidence. Saturday and Saturday night: Sub-VFR possible with some scattered showers primarily from 15 to 23Z. Southerly wind gusts 10-15 knots, becoming northwest Saturday night. Medium to high confidence. Sunday and Sunday night: VFR, a few sprinkles or flurries possible at KABE Sunday morning. Northwest wind gusts from 20-25 knots. Medium confidence. Monday through Tuesday night: VFR, West winds around 10-15 knots becoming more southerly on Tuesday. High confidence.
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&& .MARINE... No marine headlines anticipated through Friday. A 3 foot se swell at 10 seconds is the primary driver of the Atlantic coastal waters forecast. OUTLOOK... Friday night: Sub-SCA southwesterly wino below SCA levels under 15 knots and seas around three feet. High confidence. Saturday and Saturday night: Seas building late Saturday but staying under 5 feet. Southwesterly wind gusts 15-20 knots in the afternoon. Winds becoming northwesterly Saturday night and increasing to 20- 25 knots. Medium confidence. Sunday and Sunday night: Seas steady just under five feet with some northwest wind gusts around 25 knots. An SCA currently looks like it will be needed in this period. Medium confidence. Monday through Tuesday night: Westerly wind gusts generally around 15 knots but increasing on Tuesday closer to 25 knots. Seas decrease Monday but should begin to build up by Tuesday close to five feet. Low to medium confidence. && .CLIMATE... As it stands with our 330PM forecast. It appears the month will average about a degree or 2 below normal vcnty I-80, near or slightly below normal remainder of the area except about a degree above normal near GED. Short waves passing through eastern Canada have not dug quite as far south as indicated 8 days ago when it appeared a below normal month was probable. This would end up being about degree warmer than our deterministic solution from the 15th. There is still uncertainty regarding how temperatures verify from Tuesday the 28th onward. Todays 12z/23 GGEM and ECMWF operational cycles for 2m temps are significantly cooler for a day or two between Tuesday and Thursday (28-30th). For now we lean with the warmer GFS per the GEFS and even the ECEFS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Gaines Near Term...Iovino Short Term...Drag Long Term...Gaines Aviation...Gaines/Iovino/Johnson Marine...Drag/Gaines Climate...

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