Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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658 FXUS61 KPHI 200412 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1112 PM EST Mon Feb 19 2018 .SYNOPSIS... A warm front approaches tonight and lifts through the region Tuesday morning. Bermuda high pressure is then in control through Wednesday. Low pressure develops ahead of a cold front and moves through the region Wednesday night. A series of low pressure systems will then impact the Northeast and Mid-Atlantic through the upcoming weekend and into the start of the new week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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We have issued a Dense Fog Advisory for the remainder of the overnight hours. A warm front remains south of the area overnight, and warm/moist air is overrunning the front across our area. Fog and drizzle are expected to continue to develop across the area through the overnight. Areas along and north of the I-95 corridor are already 1/2-1/4 mile with fog. The Dense Fog Advisory starts now and runs through the night. Areas south of the I-95 corridor are not that low yet, but there is indications that they will lower overnight as the warm front gets closer to the area. These areas have their Dense Fog Advisory starting later in the night. Other than a few showers exiting eastern New Jersey, most of the rain has ended for the night. Temperatures has slowly risen a couple of degrees over the past couple of hours and should slowly rise a bit more through the night morning.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
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The warm front will ligt north of the area Tuesday as low pressure across the Great Lakes starts to move into Canada. The steady rains will mostly by done by dawn, but still plenty of low clouds, fog and some drizzle too. We will keep a chc for showers near the shore areas during the morning however. Conditions will improve from SW to NE thru the day as drier air arrives on a SW flow. Temperatures will climb thru the day, and readings will reach the upper 60s to low 70s in many areas. These readings will be reached once the sun return, so any delay in that, may cause readings to be lower than fcst. Winds will be mostly SW at around 10 mph.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Bermuda high pressure is in control for much of Wednesday. SW flow behind the high continues to advect an anomalously warm airmass into the region as 1000-500 MB thicknesses climb to around 565 dam and 850 MB temps climb to around 13C. What is fairly interesting is that the 12Z/19 NAM is similar to the 12Z/19 ECMWF and the 12Z/19 GFS in terms of 1000-500 MB thicknesses and 850 MB temps, yet the NAM MOS guidance is almost 10 degrees colder than the MAV MOS guidance. Unless there is widespread fog and stratus across the region, and with SW flow, that is unlikely, so NAM MOS temps were discounted. Mixed down from 925 MB, and blended with the MAV MOS. As a result, still have highs in the upper 60s to low 70s generally north and west of the Fall Line, and in the mid to upper 70s across southeast PA, southern NJ, and the Delmarva. Several high temperature records are likely to be broken. Meanwhile, a strong cold front will be digging through the central U.S. Low pressure develops out ahead of that front, and will nose its way into the region by Wednesday evening, and then the cold front swings through Wednesday night and becomes nearly stationary over the Mid-Atlantic. There is not much in the way of mid-level shortwave energy with the passage of the front, and strong upper jet will stay well north and west of the region. Will expect some showers with it, but despite going from a warm and relatively humid airmass to a closer to seasonal airmass, not seeing the dynamics to support thunder Wednesday evening. With the front nearly stationary to our south and several mid- level shortwaves approaching from the west, can expect unsettled weather through the end of the week and even into the weekend. Although the record level warmth will be gone, temperatures will generally be above the seasonal norm. The pattern seems to alternate between the warmer air to the south and the colder air to the north. If the colder air settles in, especially north of I-80, that may result in some ice issues as the warmer air returns Thursday night and Friday morning. For now, looks like snow, but bears watching. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Widespread IFR/LIFR conditions across the terminals this evening. periods of VLIFR expected overnight into the early morning as visibilities drop down to 1/4-1/2SM. Some patchy rain/drizzle is expected through the night. Winds mostly S or SW 5 to 10 knots, becoming light and variable at times. Low- end LLWS with 35 to 40 knots at 020-025. Tuesday...LIFR/IFR conditions will continue Tuesday morning with a very slow improvement expected. Might not start seeing some MVFR/VFR conditions until late morning/early afternoon. South to southwest winds will continue, becoming around 10 knots by the afternoon. OUTLOOK... Tuesday night...Fog and stratus with MVFR/IFR conditions possible. Light south winds. Confidence: Average. Wednesday...Fog and stratus dissipate in the morning, giving way to VFR conditions. SW winds 10-15 kt with gusts to 20 kt. Confidence: Above average. Wednesday night...Scattered showers and patchy fog possible with sub-VFR conditions. Winds shift from SW to N around midnight. Confidence: Average. Thursday...Sub-VFR conditions possible in scattered showers. NE winds 10-15 kt. Confidence: Average. Thursday night...Sub-VFR conditions possible in scattered showers. Some rain/snow showers possible at KRDG/KABE. Confidence: Below average. Friday through Saturday...Sub-VFR conditions in showers. Confidence: Below average. && .MARINE...
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A Dense Fog Advisory has been issued for the coastal waters for the remainder of tonight through Tuesday morning as areas of fog area likely to be occuring or form through tonight. Visibilities of one mile or less can be expected. Conditions will remain below SCA criteria tonight and Tuesday. Winds will be mostly south to southwest through the period with speeds 5 to 10 knots tonight and 10 to 15 knots Tuesday. OUTLOOK... Tuesday night through Wednesday morning...Sub-SCA conditions. VSBY restrictions in fog likely. Wednesday...SW winds 15-20 kt, seas around 4 feet. Morning fog dissipates. Wednesday night...Seas around 5 feet early, then subsiding to 3-4 feet. SW winds turning NW late. Thursday...SCA conditions possible, at least on the ocean waters. Friday through Saturday...Sub-SCA conditions anticipated.
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&& .CLIMATE... Record high temperatures are possible on Tuesday and Wednesday. Tuesday, February 20: Atlantic City...70 in 1930 Philadelphia....70 in 1939 Wilmington......71 in 1930 Allentown.......68 in 1930 Trenton.........70 in 1930 Georgetown......68 in 2002 Mount Pocono....59 in 1930 Reading.........72 in 1930 Wednesday, February 21: Atlantic City...74 in 1930 Philadelphia....72 in 1930 Wilmington......70 in 1953 Allentown.......67 in 1953 Trenton.........70 in 1930 Georgetown......71 in 2014 Mount Pocono....60 in 1930 Reading.........71 in 1930 A record warm minimum temperature may be set for Atlantic City on Tuesday. The current record is 44 in 1949. The following are the record warm minimum temperatures for Wednesday, all which should be exceeded. ABE 46-1981 ACY 49-1954 PHL 49-2002 ILG 47-2002 RDG 48-1930 TTN 48-2002 The all time February max temps may be approached on Wednesday at ILG, TTN, GED RDG MPO. All the all time monthly max`s are listed below: ACY 77 2/25/30 PHL 79 2/25/30 ILG 78 2/24/85 ABE 77 2/24/17 TTN 76 2/25/30 GED 77 2/25/17 RDG 77 2/24/17 MPO 70 2/25/30 Our expectation is that ACY will exceed the previous all time record rainfall for February, by the end of the weekend. The record is 6.50 inches in 2010. #2 is 1958 with 5.98 inches. And...adding only half an inch to PHL and ILG will put both locations in the top 9 ranking for Feb rainfall. Have rechecked the monthly projection at PHL and the avg temp continues at 41.0 or 5.3F above avg which is 8th warmest on record, if it holds. Add or subtract a degree to the average/departure and the ranking changes from 3rd to 11th. The forecast 5.3F departure is ~2f warmer than the current departure. I`d expect similar for the rest of our area...a bit less in the north which will have better chances for colder air, and a bit more warming in the south where the positive departure as of yesterday was already 5F above normal, heading for 7+. So all in all it appears we`re heading for a top 10 warmest February. Last year was the warmest on record, a whopping 3+F degrees warmer than our current projection. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...Dense Fog Advisory until 10 AM EST Tuesday for PAZ054-055- 060>062-070-071-101>106. NJ...Dense Fog Advisory until 10 AM EST Tuesday for NJZ001-007>010- 012-013-015>019. Dense Fog Advisory from 3 AM to 10 AM EST Tuesday for NJZ014- 020>027. DE...Dense Fog Advisory until 10 AM EST Tuesday for DEZ001. Dense Fog Advisory from 3 AM to 10 AM EST Tuesday for DEZ002>004. MD...Dense Fog Advisory until 10 AM EST Tuesday for MDZ008-012. Dense Fog Advisory from 3 AM to 10 AM EST Tuesday for MDZ015- 019-020. MARINE...Dense Fog Advisory until 10 AM EST Tuesday for ANZ430-431- 450>455.
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&& $$ Synopsis...MPS Near Term...Robertson/Meola/O`Hara Short Term...O`Hara Long Term...MPS Aviation...Meola/MPS/O`Hara Marine...Robertson/MPS/O`Hara Climate...

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