A humid airmass and moist flow off the Atlantic allowed dense fog to develop over St. Mary's County in lower southern Maryland.
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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 humid airmass and moist flow off the Atlantic allowed dense fog to develop over St. Mary's County in lower southern Maryland. Visibilities fell to one quarter mile or less for several hours before 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 Baltimore/Washington wrote its last area forecast discussion before the first event at May 10, 2:02 AM EST, 1 hour 58 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 302 AM EDT THU MAY 10 2007 .SYNOPSIS... A WEAK TROUGH OF LOW PRESSURE MOVES EAST INTO THE REGION THIS AFTERNOON AND TONIGHT. THAT WILL STALL JUST SOUTHEAST OF THE AREA THROUGH LATE SATURDAY. A COLD FRONT WILL SWEEP THROUGH THE MID ATLANTIC EARLY SUNDAY BRINING COOLER TEMPERATURES AND DRIER AIR. CANADIAN HIGH PRESSURE WILL SETTLE OVER THE AREA THROUGH EARLY NEXT WEEK. && .NEAR TERM /UNTIL NOON TODAY/... MARINE LYR HAS WORKED INLAND ONCE AGN THIS MRNG...AND PRETTY MUCH ENCOMPASSES MOST AREAS E OF THE BLURDG. HWVR...THERE/S A LGT SLY BRZ...WHICH HAS INHIBITED FOG FORMATION. INSTEAD...THE INFLUENCE IS MORE IN THE FORM OF LOW CLDS...WHICH WL AFFECT AVN INTERESTS. W/ DEWPTS NEAR 60F...THERE HAS BEEN FOG ALNG THE BAY...AND MTRS REFLECT THAT MOSTLY IN CALVERT/ST MARYS CNTYS. ALTHO NO OBS AT 1/4SM YET... WL GO AHD W/ DENSE FOG ADVY FOR THOSE TWO CNTYS. STILL THINK THAT BNDRY LYR WL DCPL BRIEFLY TWD SUNRISE...AND AREAS OF FOG WL DVLP... BUT NOT WDSPD OR DENSE. MUCH LIKE YDA...STRONG MAY SUN WL ERODE LYR DURING MRNG HRS. && .SHORT TERM /NOON THROUGH 6 PM TODAY/... EXPECTING MORNING LOW OVERCAST AND FOG TO BREAK DOWN DURING THE MORNING HOURS. NEXT UP IS A TROF MOVING TOWARDS THE REGION FROM THE MIDWEST. EARLY THIS MORNING THAT TROF WAS PRODUCING A FEW SHOWERS AND TSRA OVER OHIO. THAT ZONE OF FORCING AND INSTAB WILL MOVE INTO THE WV MOUNTAINS LATE THIS MORNING...THEN WILL PRODUCE SCT SHOWERS AND THUNDERSTORMS OVER THE EASTERN WEST VIRGINIA PANHANDLE AND WESTERN MD. AFTER CHECKING 21Z SREF 00Z NAM AND GFS AND THE 00Z LOCAL WRF...THERE COULD BE A FEW ISOLATED SHOWERS OR TSRA EAST OF THAT AREA...BUT NOT EXPECTING MUCH THIS AFTERNOON IN THE EAST AT THIS TIME. PRECIPITABLE WATER IS JUST UNDER AN INCH AND A HALF...SO VERY HEAVY RAIN. BUT ATMOS WINDS SHOULD KEEP STORMS MOVING ALONG TO THE ENE. && .LONG TERM /TONIGHT THROUGH WEDNESDAY/... TONIGHT THAT ZONE OF WEAK FORCING WILL SLOWLY MOVE ACROSS THE FORECAST AREA...BUT INSTAB WILL DIMINISH AS IT MOVES EAST. BY FRIDAY THE TROF WILL BE HUNG UP JUST TO OUR S AND SE...BUT A FAIR AMOUNT OF MOISTURE AND GENERAL INSTAB REMAIN AROUND THE FORECAST AREA. BEST CHC OF PRECIP STILL S AND E FRIDAY THROUGH SATURDAY. THE GFS BRINGS A SHORT WAVE THROUGH THE REGION SAT NIGHT...BUT NOTING THE SREFS BASIC LACK OF POPS FOR US...WILL DISREGARD THAT S/W FOR NOW. BY SUNDAY THE NEXT SHOT OF CANADIAN HIGH PRESSURE WILL BE MOVING SOUTH INTO OUR AREA WITH AN INC IN NORTH WINDS AND COOLER TEMPS ALONG WITH CLEARING SKIES AND LOWERING HUMIDITIES. HOWEVER IT WILL BE SHORT LIVED AS THE HIGH ALREADY MOVES SE OF THE REGION BY MONDAY AFTERNOON ALLOWING FOR RETURN FLOW. STILL...NO PRECIP UNTIL AT LEAST TUE AND POSSIBLY WED AS THE NEXT COLD FRONT SLOWLY PUSHES S TOWARDS THE MID ATL FROM THE NNW. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... MARINE LYR HAS ADVCD ACRS TAF SITES E OF BLURDG...IN THE FORM OF LOW CLDS. CIGS BLO OVC010 DC/BALT...AND BTWN 1000-2000 FT TO THE W. LGT SLY FLOW HAS HINDERED DVLPMNT OF FOG /VSBYS STILL VFR AT TAF SITES/. HWVR...FRTHR E...CIGS/VSBYS BOTH LIFR/VLIFR...AND THIS IS THE AMS THAT/S ADVECTING WWD. THINK BNDRY LYR WL DCPL TWD DAWN...AND SATD LLVLS WL ENABLE IFR FOG TO DVLP. ALL LOCATIONS WL EXPERIENCE AT LEAST A FEW HRS W/ CIGS BLO 1000 FT AS WELL. AFTR SUNRISE...THIS LYR SHUD MIX OUT...AND BALANCE OF DAY WL BE VFR. AMS UNSTBL ENUF FOR WDLY SCT SHRA/TSRA...BUT CONFIDENCE/RISK TOO LOW FOR MNTN ATTM. PREFRNTL TROF WL APPCH TNGT...PROVIDING A BETTER CHC AT SHRA/TSRA. THUS FAR...WENT W/ PREDOMINANT SHRA /MVFR VSBY/ FOR MRB...THINKING THAT ANY PCPN WL HOLD OFF TIL AFTR 06Z VALID PD. INCLUSION WL COME W/ 12Z ISSUANCE. WL ALSO RECONSIDER NEED FOR THUNDER...OR AT LEAST A VCTS COMMENT. CHANCE OF CONVECTION ESP OVER E WV AND W MD THIS AFTERNOON AND EVENING...SHIFTING SLOWLY EAST AND WEAKENING DURING THE NIGHT. THAT AXIS SLIDES MAINLY S AND E OF OUR AREA BY FRIDAY...BUT THERE STILL WILL BE THE CHANCE OF TSRA UNTIL COOLER AIR MOVES IN SUNDAY. WEAK WINDS THROUGH SATURDAY. OTHER THAN THE TSRA AND POSSIBLY SOME LOW OVERCAST AND FOG AGAIN LATE TONIGHT OVER SE MD AND E VA...NO OTHER MAJOR AVIATION CONCERNS THROUGH MONDAY. WINDS BECOME N AND INC SUNDAY WITH THE ARRIVAL OF HIGH PRESSURE. && .MARINE... XPCT VSBY RESTRICTIONS DUE TO FOG IN HUMID AMS...SPCLY IN MAIN CHANNEL OF CHSPK. GENERALLY LIGHT WINDS THROUGH THE WEEK WITH CHANCE OR SLIGHT CHANCE OF THUNDERSTORMS. WINDS BECOME N AND INCREASE TO ABOUT 12G18KT ON SUNDAY AS COOLER HIGH PRESSURE MOVES INTO THE REGION. WINDS DIMINISH SUNDAY EVENING. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR MDZ017-018. VA...NONE. WV...NONE. MARINE...NONE. && SYNOPSIS...STRONG NEAR TERM...HTS SHORT TERM...STRONG LONG TERM...STRONG AVIATION...HTS/STRONG MARINE...HTS/STRONG
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 320 AM EDT THU MAY 10 2007 ANZ530>537-DCZ001-MDZ003>007-009>011-013-014-016>018-501-502- VAZ021-025>031-036>042-050>057-WVZ050>055-501>504-101600- 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- DISTRICT OF COLUMBIA-WASHINGTON-FREDERICK MD-CARROLL- NORTHERN BALTIMORE-HARFORD-MONTGOMERY-HOWARD-SOUTHERN BALTIMORE- PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS-CALVERT- EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-HIGHLAND- AUGUSTA-ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE- NELSON-ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-FAUQUIER-LOUDOUN- ORANGE-CULPEPER-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX- ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA- KING GEORGE-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-PENDLETON-HARDY- WESTERN GRANT-EASTERN GRANT-WESTERN MINERAL-EASTERN MINERAL- 320 AM EDT THU MAY 10 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR MARYLAND WEST OF THE EASTERN SHORE INCLUDING THE CHESAPEAKE BAY AND EAST OF GARRETT COUNTY...EASTERN WEST VIRGINIA...NORTHERN AND CENTRAL VIRGINIA... WASHINGTON DC AND THE TIDAL POTOMAC RIVER. .DAY ONE...TODAY AND TONIGHT A DENSE FOG ADVISORY HAS BEEN ISSUED FOR CALVERT AND SAINT MARYS COUNTIES IN LOWER SOUTHERN MARYLAND. CONSULT THE LATEST ADVISORY ON NOAA WEATHER RADIO OR AT WEATHER.GOV ON THE INTERNET. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED. HTS/STRONG
The national radar mosaic for the moment the first event began.
1 dense fog. Local standard time, as filed.
Automated Observations from Patuxent River Naval Air Station (KNHK) and St. Inigoes Airport in St. Mary's County reported dense fog with visibilities of one quarter mile of less.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2007Every state in 2007This day in weather historyWarnings in Maryland, May 2007
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: 27114.