A combination of recent rainfall, clearing skies, and light winds led to the formation of fog, some of which became dense with visibility less than a quarter of a mile.
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The episode as NWS LWX wrote it up.
A combination of recent rainfall, clearing skies, and light winds led to the formation of fog, some of which became dense with visibility less than a quarter of a mile.
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 Baltimore/Washington wrote its last area forecast discussion before the first event at Aug 31, 2:59 AM EST, 1 hour 36 minutes earlier.
Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 359 AM EDT Fri Aug 31 2018 .SYNOPSIS... A weak cold front will stall over the region today and remain overhead through Saturday. The boundary will dissipate Sunday and high pressure will build over the western Atlantic during the early and middle portions of next week. && .NEAR TERM /THROUGH TONIGHT/... A frontal boundary bisects the CWA early this morning near the I-66 corridor, oriented in a west to east fashion. Skies remain mostly cloudy across much of the region, however there are some breaks in the cloud cover west of the Blue Ridge. It is also here where patchy dense fog is being observed. Radar echoes have lessened over the last couple of hours with isolated coverage of showers/drizzle. Temperatures holding steady in the upper 60s to middle 70s. Hi-res guidance is honing in on shower activity picking up over the next few hours as the frontal boundary hangs overhead and shortwave energy aloft passes from west to east. Areas favored to see an uptick in shower activity and perhaps a rumble of thunder will be along and to the north and east of the Potomac River. Latest mesoanalysis does depict a wedge of instability over this region, supporting the above scenario playing out through the morning rush. With the boundary lingering across central Virginia today, continued shower and isolated thunderstorm chances will persist into early this evening. The primary hazard today will be localized flooding with the potential for heavy rainfall as ample cloud cover and the boundary across central Virginia should limit any severe threat. This is supported by precipitable water values near two inches and low level convergence along the stationary boundary. The heaviest axis of precipitation this morning points to setting up along and east of the Blue Ridge, including the metro areas. Coverage across the mountains will increase this afternoon and early this evening with maximized daytime heating. Expect highs today to remain slightly below normal in the low to middle 80s. Coverage of showers decreases overnight with the loss of daytime heating and limited support aloft, however the boundary will hold its position across central Virginia, so will maintain a chance of showers. Patchy fog will be likely through the overnight hours given the saturated soils and low level moisture persisting. Lows in the upper 60s to near 70 degrees can be expected. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... No discernible changes in the pattern on Saturday as the boundary stubbornly lingers nearby, promoting weak low level convergence, and the trigger for showers and storms. The afternoon and early evening hours will be favored for the highest coverage of activity. Locally heavy rain will be the primary threat, but strong gusty winds will be possible in and around thunderstorm activity. Will carry chance POPs Saturday and Sunday, with coverage trending a bit less each day as the boundary weakens and eventually washes out over the region. Humid conditions will continue to win out through the weekend with dewpoints in the upper 60s to lower 70s. Highs will top out near normal in the 80s with overnight lows in the upper 60s to lower 70s. && .LONG TERM /MONDAY THROUGH THURSDAY/... An upper-level high will remain over the region Monday through Thursday while surface high pressure over the western Atlantic extends into our area as well. 500mb heights are forecast to be anomalously high. The 12z run from 8/30 on the NAEFS forecasts mean 500mb heights to be forecasted outside (higher) than climatology for this time of year. Strong subsidence from the upper-level ridge and an onshore flow to the surface flow means that more unseasonably hot and humid conditions are likely. Highs are most likely to range from the upper 80s to lower/middle 90s for most areas along with high humidity. The heat and humidity will lead to an unstable atmosphere each day, so there will be chances for showers and thunderstorms...mainly during peak heating in the afternoon/evening hours each day. Coverage may remain scattered due to the lack of strong lifting mechanism, weak shear and subsidence overhead...but slow movement of storms and low min theta e's could lead to isolated instances of flooding and gusty winds. Confidence in details remain low at this time. && .AVIATION /07Z FRIDAY THROUGH TUESDAY/... Frontal boundary will linger near the terminals today and through the weekend. This will promote daily chances of showers and storms, with the peak heating hours of the day favored. Episodes of sub VFR conditions will be possible as a result. Patchy fog will be possible during the overnight hours as well with ample low level moisture and saturated soils, with CHO/MRB most likely to see sub VFR VIS/CIGs. Winds generally will hail from the east southeast through Saturday, turning a bit more southerly on Sunday, but remaining at 10 knots or less through the weekend. Upper-level high pressure will remain overhead for Monday and Tuesday, causing light winds. Patchy fog is possible during the overnight and morning hours each day and scattered thunderstorms are possible both days as well, especially during the afternoon and evening hours. && .MARINE... Sub SCA conditions forecast through the weekend as a stationary boundary stretches across the waters. Gusty winds in and around thunderstorm activity will be possible each day with the afternoon and evening hours favored. This may result in the need to Special Marine Warnings for any of the stronger activity. Given the boundary nearby, the gradient will remain weak enough through the weekend for winds to remain below SCA criteria. High pressure over the western Atlantic will extend toward the waters for Monday through Wednesday. The gradient should be weak so winds should remain below SCA criteria for most of the time. There may be a few showers and thunderstorms each day, especially during the afternoon and evening hours. However, coverage is most likely to remain isolated or scattered. && .TIDES/COASTAL FLOODING... An onshore flow will develop today and persist through the weekend as a boundary stalls near the waters and eventually dissipates by Sunday. The onshore flow will lead to an increase in tidal anomalies. Latest forecasts show many locations reaching caution stages tonight through the weekend. Minor flooding is possible for sensitive areas, but confidence is low since the onshore flow will be light. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && SYNOPSIS...BJL NEAR TERM...BKF SHORT TERM...BKF LONG TERM...BJL AVIATION...BJL/BKF MARINE...BJL/BKF TIDES/COASTAL FLOODING...BJL
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 516 AM EDT Fri Aug 31 2018 ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-010930- Chesapeake Bay north of Pooles Island MD- Chesapeake Bay from Pooles Island to Sandy Point MD- Chesapeake Bay from Sandy Point to North Beach MD- Chesapeake Bay from North Beach to Drum Point MD- Chesapeake Bay from Drum Point MD to Smith Point VA- Tidal Potomac from Key Bridge to Indian Head MD- Tidal Potomac from Indian Head to Cobb Island MD- Tidal Potomac from Cobb Island MD to Smith Point VA- Patapsco River including Baltimore Harbor- Chester River to Queenstown MD-Eastern Bay- Choptank River to Cambridge MD and the Little Choptank River- Patuxent River to Broomes Island MD- Tangier Sound and the inland waters surrounding Bloodsworth Island-District of Columbia-Southern Baltimore-Prince Georges- Anne Arundel-Charles-St. Marys-Calvert-Southeast Harford- Prince William/Manassas/Manassas Park-Fairfax- Arlington/Falls Church/Alexandria-Stafford-Spotsylvania- King George- 516 AM EDT Fri Aug 31 2018 This Hazardous Weather Outlook is for the Maryland portion of the Chesapeake Bay, Tidal Potomac River, and adjacent counties in central Maryland and northern Virginia as well as the District of Columbia. .DAY ONE...Today and Tonight Showers and thunderstorms producing locally heavy rain with isolated incidents of flooding are possible across the Washington and Baltimore Metropolitan areas this morning, and the entire area this afternoon and evening. .DAYS TWO THROUGH SEVEN...Saturday through Thursday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected. MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053- 055-501>506-010930- Washington-Frederick MD-Carroll-Northern Baltimore- Extreme Western Allegany-Central and Eastern Allegany- Northwest Montgomery-Central and Southeast Montgomery- Northwest Howard-Central and Southeast Howard-Northwest Harford- Augusta-Rockingham-Shenandoah-Frederick VA-Page-Warren-Clarke- Nelson-Albemarle-Greene-Madison-Rappahannock-Orange-Culpeper- Northern Fauquier-Southern Fauquier-Western Highland- Eastern Highland-Western Loudoun-Eastern Loudoun- Northern Virginia Blue Ridge-Central Virginia Blue Ridge- Hampshire-Morgan-Berkeley-Jefferson-Hardy-Western Grant- Eastern Grant-Western Mineral-Eastern Mineral-Western Pendleton- Eastern Pendleton- 516 AM EDT Fri Aug 31 2018 This Hazardous Weather Outlook is for eastern West Virginia, northern and central Virginia, and central and western Maryland with the exception of Garrett County. .DAY ONE...Today and Tonight Showers and thunderstorms producing locally heavy rain with isolated incidents of flooding are possible through this evening. .DAYS TWO THROUGH SEVEN...Saturday through Thursday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1258 AM EDT FRI AUG 31 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1254 AM MARINE TSTM WIND 17 NE SMITH ISLAND 38.14N 75.79W
08/31/2018 M44 MPH ANZ543 MD BUOY
&&
EVENT NUMBER LWX1801820
BJLThe national radar mosaic for the moment the first event began.
2 dense fog. Local standard time, as filed.
Observations from around the area indicate visibility was reduced to a quarter of a mile in dense fog.
Observations from around the area indicate visibility was reduced to a quarter of a mile in dense fog.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Virginia in 2018Every state in 2018This day in weather historyWarnings in Virginia, August 2018
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: 777331, 777332.