Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 181758 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 158 PM EDT Mon Mar 18 2024 .SYNOPSIS...
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A reinforcing cold front moves through the region late today. Several upper level disturbances and cold fronts will pass through the region this week as surface high pressure builds to the west. Developing low pressure approaches for the end of the week and weekend.
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&& .NEAR TERM /THROUGH TUESDAY/... Weak reinforcing cold front moving across the region late this afternoon with a bit more cold advection and mid-level cloud cover overspreading the region, and possibly a few sprinkles or flurries, especially in the Poconos. Dry, colder air mass builds in behind the front tonight with temps dropping near or below freezing region-wide, accompanied by a persistent west to northwest wind, resulting in wind chills deep into the 20s for most and into the lower teens in the Poconos. Will have some sun to start on Tuesday, but clouds then increase as warm advection gets underway ahead of the next system. The combination of the cold air mass and return of clouds will keep temps down on Tuesday, with few locations managing to reach 50. Winds will remain gusty as well much of the day. By late afternoon, there could be enough warm advection to cause a few flurries or snow showers to develop in the Poconos, but the air mass should be too dry elsewhere for any precip. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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A weak cold front crosses through the region late Wednesday, but no impactful weather is expected aside from conditions becoming more conducive for fire spread (more information below in the Fire Weather section) Ahead of the cold front Wednesday night, weak warm air advection will allow temperatures on Wednesday to be 5 to 10 degrees higher than Tuesday. As the cold front approaches late in the day Wednesday, a few showers are possible primarily north and west of the fall line. However, any precipitation (should be mostly rain aside from the higher terrain of the southern Poconos) will be very light, with rain amounts less than a tenth of an inch. In the wake of the front Wednesday night into Thursday, expect a relatively tight surface pressure gradient. Consequently, winds of 15 to 25 mph gusting as high as 40 mph are expected. The other impact of the cold front is that it will be considerably cooler. A widespread freeze is likely Wednesday night/Thursday morning (we remain outside of the growing season so no frost/freeze headlines are needed at this time).
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
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With high pressure moving offshore Friday, return flow sets up and temperatures begin to warm back up to normal levels for the end of the week and weekend. The main feature we are watching in this period is a low developing off the coast of the southeastern U.S.. Some guidance depicts this low lifting northeast along the coast, while others depict it staying well to our south. If it follows something close to the first solution, we could see our next best chance for widespread precipitation Friday night into Saturday. However, if it stays far enough suppressed to the south, then precipitation should stay south of the region as well. Given the uncertainty, stayed close to a blend of guidance and the previous forecast in this time frame. Regardless of the evolution of the coastal low, an upper level trough could dig southeast towards our region at the beginning of next week, which could mean another small chance (20%) for precipitation across the area.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas... Through Tonight...VFR. Winds W to NW 10-20 kts with gusts to 25 kts rest of today diminishing to 5-10 kts with gusts 10-20 kts tonight. High confidence. Tuesday...VFR. Winds W to NW 5-10 kts with gusts 10-20 kts early increasing to 10-20 kts with gusts to 25 kts in the afternoon. High confidence. Outlook... Wednesday through Saturday...VFR overall. A few SHRA or SHSN Tuesday afternoon, and again Wednesday afternoon and evening could result in brief sub-VFR conditions. A prolonged period of W-NW winds will range from 15 to 20 kt with 25 to 35 kt gusts.
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&& .MARINE...
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SCA through Tuesday with persistent west to northwest winds 10-20 kts with gusts to 30 kts. Seas mainly 2-4 ft. Outlook... Should be a brief lull in SCA conditions Tuesday night into Wednesday morning, before SCA conditions develop again late Wednesday through the day on Thursday. Winds and seas are likely to stay below SCA criteria Friday into Saturday.
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&& .FIRE WEATHER... Lowering humidity levels and increasing winds over the next few afternoons could lead to fire weather concerns across our region. The lack of rainfall during the past week has led to dry fine fuels over the region, with fine fuel moisture already below 20 percent. A few rain or snow showers are possible across the Poconos from time to time this week. Aside from that, dry conditions on tap. Although most of the area is above normal for precipitation since March 1, it has been a week since the last significant rainfall, and no significant rainfall is expected this week. Min RH values this week will generally range from 25 to 35 percent, and stronger westerly flow occurs over the area as well with winds generally 15 to 20 mph with gusts 25 to 30 mph. The day of highest concern looks to be Thursday, where surface dew points drop into the upper single digits to low teens. Min RH values may be as low as 20 to 25 percent, and west to northwest winds could gust as high as 30 to 35 mph. By then, it will be almost 2 weeks since the last significant rainfall. Depending on how fast and how efficiently fine fuels dry out further will add to possible concerns for the rapid spread of any fires that may develop. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT Tuesday for ANZ430-431- 450>455. && $$ SYNOPSIS...Johnson NEAR TERM...RCM SHORT TERM...Johnson LONG TERM...Johnson AVIATION...Johnson/RCM MARINE...Johnson/RCM FIRE WEATHER...PHI

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