High pressure provided light easterly winds and clear skies, and with a moist lower atmosphere, areas of dense fog developed during the predawn hours on September 12th. The fog dissipated shortly after sunrise.
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The episode as NWS PHI wrote it up.
High pressure provided light easterly winds and clear skies, and with a moist lower atmosphere, areas of dense fog developed during the predawn hours on September 12th. The fog dissipated shortly after sunrise.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Sep 12, 12:28 AM EST, 32 minutes earlier.
Area Forecast Discussion National Weather Service Mount Holly NJ 128 AM EDT Thu Sep 12 2024 .SYNOPSIS... High pressure over our region will dominate our weather through early next week. By then, a tropical disturbance will be located off the Southeastern United States coastline which may bring some rain back to the region by the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... High pressure is centered just east of Cape Cod and will more or less remain in place through tonight. The pressure pattern is resulting in a light southeasterly flow, which is enhancing moisture transport off the ocean. Not a lot, but enough when coupled with near ideal radiational cooling to result in greater coverage of patchy fog and low clouds early this morning. Guidance has hit parts of the area pretty heavy with the fog, but will hold off on any dense fog advisories until the evolution becomes a bit more clear. That said, there's definitely a potential of dense fog advisories this morning, especially across New Jersey. Low clouds and fog look to break by mid morning and the rest of the day should turn out very similar to yesterday, including in the temp department. Meanwhile, as implied by the static pattern, tonight looks like it may be very similar to this past night is turning out, with clear conditions early giving way to patchy fog and low clouds late with similar temps. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... High pressure will be situated to our north and northeast near or off the coast of New England through much of the short term period leading to continuing onshore flow. Aloft, a Rex Block pattern will be setting up as upper level ridging builds over the Great Lakes and a closed low associated with what is currently Hurricane Francine meanders over the south-central US. All in all, this will result in dry weather with mainly clear to partly cloudy skies throughout the period with some occasional high clouds from Francine fanning in from south to north at times. There may also be a period of some low stratus that develops by early Friday over southern parts of the forecast area (Delmarva, south Jersey, SE PA). Highs will generally be in the upper 70s to mid 80s, with lows ranging from the mid 50s to low 60s. Humidity should remain rather comfortable. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As a whole, the long term period remains relatively unchanged through the weekend as the Rex Block pattern continues. This will yield continuing dry conditions along with above normal temperatures through Sunday. The blocking pattern does appear that it will break down early next week, which may finally result in some much needed precipitation returning to the area by midweek. For now, both the GFS/ECMWF global guidance indicate that there is potential for the development of a tropical disturbance off the Southeast US eventually lifting northward by midweek. Will have to monitor this closely as weather features following blocking patterns are often difficult to predict, but considering model to model run consistency, have maintained a 20- 30% chance of showers on Tuesday and Wednesday for much of the area. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through 12Z this morning...VFR to start. Patchy fog develops toward dawn mainly for I-95 and points east. Have TEMPOs for IFR at these terminals, with worst conditions appearing most likely at KTTN, but others could get quite low too. Low confidence overall. 12Z this morning through this afternoon...Conditions lift to VFR quickly by the mid-morning. Southeast winds around 5-10 kt. Moderate confidence. Tonight...VFR to start. Patchy fog and low clouds look likely to redevelop across the region after midnight, but for now will keep out of the TAFs. Southeasterly winds 5 kts or so. Low confidence. Outlook... Friday through Monday...Mainly VFR except will have to watch for low stratus potential Thursday night into Friday which has a chance (20-30 percent) of bringing some MVFR cigs into our southern sites (PHL southward) Thursday night into early Friday. && .MARINE... No marine headlines expected through tonight. Winds generally out of the east around 5-10 kt with 2 foot seas, building to near 3 feet late tonight. Outlook... No marine headlines are expected Friday through Saturday night. However by late Sunday into early next week seas look to increase to levels near or above Small Craft Advisory levels due developing system south of our waters. Rip currents... Through Friday...Northeast winds around 10 mph will become east to locally southeast each afternoon and evening. Breaking waves in the surf zone are forecast to be around 2 feet with a period of around 8 seconds. As a result, there is a LOW risk for the development of dangerous rip currents for both the Jersey Shore and the Delaware Beaches. For specific beach forecasts, visit weather.gov/beach/phi && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && SYNOPSIS...DeSilva/Fitzsimmons/RCM NEAR TERM...RCM SHORT TERM...DeSilva/Fitzsimmons LONG TERM...DeSilva/Fitzsimmons AVIATION...Fitzsimmons/Hoeflich/MJL/RCM MARINE...Fitzsimmons/Gorse/Hoeflich/RCM
The national radar mosaic for the moment the first event began.
1 dense fog. Local standard time, as filed.
Several hours of dense fog was reported at Wilmington Airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Delaware in 2024Every state in 2024This day in weather historyWarnings in Delaware, September 2024
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1215252.