A combination of recent rainfall, abundant low level moisture, and light winds led to the formation of fog, some of which became dense with visibility less than a quarter of a mile.
Every event with a place to put it; 14 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LWX wrote it up.
A combination of recent rainfall, abundant low level moisture, 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 Sep 1, 10:16 PM EST, 3 hours 59 minutes earlier.
Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 1116 PM EDT Sat Sep 1 2018 .SYNOPSIS... A stationary front over central Virginia will slowly dissipate overnight. High pressure and heat will build over the western Atlantic during the early and middle portions of next week. A cold front may approach from the north late next week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Shortwave energy crossing the forecast area late this afternoon/early this evening has been supporting a broken line of showers/thunderstorms. While there was a downward echo trend around sunset, a regeneration of storms has occurred along the boundary...much like yesterday...which is now across southern Maryland. Aside from that, subsidence behind the shortwave has generally led to relatively-rain free conditions behind the trough axis. Believe that will be the main story for the overnight hours. With that in mind, have cancelled the Flash Flood Watch for portions of central Virginia. Will be keeping an outside chance of a shower due to CAM support given the saturated nature of the airmass and residual instability. High dewpoints/moist ground and parting clouds also suggest that fog will be a consideration, especially west of the Blue Ridge. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... A warm and humid holiday weekend expected Labor Day weekend. On Sunday...guidance in good agreement showing increase of height aloft as high pressure builds into the region. Little change in airmass continue with uncomfortably humid condtions persisting...as dew points continue to be in the L/M 70s during the day Sunday. Winds at the surface will be light and with heights building aloft...convection will be scattered at best forming on any weak boundaries due to differential heating from clouds and/or localized wind circulation...mountain/valley or bay/river breeze. Temperatures will be very warm with readings around 90F east of the Blue Ridge. Any convection that fires Sunday afternoon will diminish rapidly after sunset with high pressure aloft. Overnight temperatures on Sunday night will continue unseasonably warm with low/mid 70s and high humidity. Some isolated patchy fog especially in the valleys west of the Blue Ridge possible. For Monday and Monday night...500 hPa heights continue to increase with a large 594 height covering much of the central Mid-Atlantic region. This should help suppress convection to isolated on Monday...mainly to some ridge lines along and west of the Blue Ridge during the afternoon. Temperatures quite warm on Monday/Labor Day with lower 90s in the DC/Baltimore metro areas. Another unseasonably warm and humid night on Monday night with lows in the 70s. .LONG TERM /TUESDAY THROUGH SATURDAY/... Very strong late season upper ridge will be positioned over the area Tuesday. High pressure at the surface will pivot over the Mid- Atlantic and New England and into the western Atlantic as the upper ridge gradually breaks down during the middle part of next week. 850 hPa temps will be in 17-19 C during this time, suggesting high temperatures at the surface will reach the lower to middle 90s. Southeasterly low-level flow will keep dew points elevated, likely well into the 70s. This would result in heat index values over 100. There's a daily chance for spotty showers and thunderstorms given the heat and humidity, but should remain spotty given synoptic ridging. As the ridge breaks down late next week, a cold front may approach from the Great Lakes resulting in a more organized chance of showers and thunderstorms. && .LONG TERM /TUESDAY THROUGH SATURDAY/... && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... Low clouds/fog will be a concern for the overnight. That said, have relatively low confidence in the details. Have therefore capped forecasts at MVFR except for CHO vsbys-- which has climo support for IFR-- and have maintained VFR at DCA. Would not be surprised if IFR ended up to be more prevalent. VFR conditions expected Sunday after morning fogs dissipates. Mainly VFR outside of any spotty TSRA or early morning patchy fog/stratus Tue-Wed of next week. && .MARINE... With high pressure expected to dominate conditions through early next week, winds are expected to remain below advisory levels. Isolated showers and thunderstorms possible late this afternoon and evening and again on Sunday afternoon. Monday should feature little in the way of storms. Southeasterly flow around high pressure should remain relatively light, and Small Craft Advisories are not anticipated during the middle of next week. A couple pop up thunderstorms are possible each afternoon. && .TIDES/COASTAL FLOODING... Onshore flow continues to cause some increase in water levels approaching advisory level at Annapolis, Straits Point and Washington. A Coastal Flood Advisory has been issued for Washington DC along the upper tidal Potomac River. Elsewhere, water levels are more likely to reach caution stage instead of minor flood stage...due to the light flow. Onshore flow persists through through Sunday keeping water levels elevated. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until 3 AM EDT Sunday for DCZ001. MD...None. VA...None. WV...None. MARINE...None. && SYNOPSIS...SMZ NEAR TERM...HTS SHORT TERM...SMZ LONG TERM...DHOF AVIATION...SMZ/DHOF MARINE...SMZ/DHOF TIDES/COASTAL FLOODING...BJL
Hazardous Weather Outlook National Weather Service Baltimore MD/Washington DC 816 PM EDT Sat Sep 1 2018 ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-030030- 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- 816 PM EDT Sat Sep 1 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...Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Sunday through Friday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. Please report any flooding or heavy rain to the National Weather Service. MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053- 055-501>506-030030- 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- 816 PM EDT Sat Sep 1 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...Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Sunday through Friday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. Please report any flooding or heavy rain to the National Weather Service. HTS
The national radar mosaic for the moment the first event began.
14 dense fog. Local standard time, as filed.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less in dense fog.
Observations from around the area indicate visibility fell to a quarter of a mile or less 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, September 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: 784426, 784427, 784428, 784429, 784430, 784431, 784432, 784433, 784434, 784435, 784436, 784437, 784438, 784439.