A stationary boundary triggered showers and thunderstorms. The main threat was heavy rain, but there was an isolated severe thunderstorm due to the unstable atmosphere.
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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 stationary boundary triggered showers and thunderstorms. The main threat was heavy rain, but there was an isolated severe thunderstorm due to the unstable atmosphere.
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 18, 1:58 PM EST, 4 hours 44 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 258 PM EDT MON MAY 18 2015 .SYNOPSIS... A COLD FRONT WILL MOVE ACROSS THE AREA ON TUESDAY. COOLER AND DRY HIGH PRESSURE WILL BUILD IN FROM MIDWEEK THROUGH THE EARLY PART OF THE WEEKEND. && .NEAR TERM /THROUGH TUESDAY/... SHOWERS AND THUNDERSTORMS DEVELOPED AS THE CONVECTIVE TEMP WAS REACHED LATE THIS MORNING INTO THE AFTERNOON. AREAS OF NERN MD NEAR THE BAY...INCLUDING BALTIMORE CITY...HAVE SINCE STABILIZED WITH TEMPS FALLING BACK INTO THE UPPER 70S. ELSEWHERE...THE CONVECTION CONTINUES WITH TEMPS IN THE 80S...EVEN PUSHING 90 IN SPOTS. MESOANALYSIS SHOWS THE GREATEST CAPE IS IN THE ONE AREA WHERE THERE HAS BEEN NO CONVECTION...AND NOTHING OF CONSEQUENCE SEEMS TO BE ABLE TO FORM ON THE OUTFLOW PUSHING WEST FROM THE BALTIMORE METRO TOWARD FREDERICK. BUT SOME OF THE HI-RES MODELS DO HINT THAT WHEN THE CONVECTION CURRENTLY OVER ERN WV PROPAGATES INTO THAT HIGHER-CAPE ZONE...IT GETS A BIT OF A BOOST IN INTENSITY. SO THAT WILL NEED TO BE MONITORED TOWARD 00Z. BLENDED TPW INDICATES PWATS AROUND 1.7 INCHES...SIMILAR TO WHAT MODEL FORECASTS INDICATED FOR 18Z. EARLIER CELLS WEST/SW OF WILMINGTON DELAWARE HAVE NOT MOVED MUCH AND THUS DROPPED AN ESTIMATED 2-3 INCHES OF RAIN. THIS POTENTIAL EXISTS LOCALLY ALSO BUT SO FAR EVERYTHING IS MOVING ALONG AND NOT STAYING IN ANY ONE LOCATION. HI-RES MODELS INDICATE THIS IS LIKELY TO CONTINUE OVERALL. ACTIVITY WILL DECREASE THIS EVENING WITH THE LOSS OF HEATING...AND MUCH OF THE OVERNIGHT CURRENTLY LOOKS DRY /ALTHOUGH A STRAY SHOWER CANNOT BE RULED OUT AT ANY POINT/. BUT TONIGHT WILL BE UNSEASONABLY WARM AND QUITE HUMID AGAIN WITH LOWS SIMILAR TO...IF NOT A DEGREE OR TWO WARMER THAN...THIS MORNING. A COLD FRONT MOVES THROUGH DURING THE DAY ON TUESDAY. CONVECTIVE TEMPS ARE AGAIN IN THE LOW/MID 80S...BUT THE MITIGATING FACTOR IS TIME-RELATED...WITH THE FRONT THROUGH MOST OF THE AREA BY EARLY AFTERNOON...AND WINDS SHIFTING OUT OF THE WEST...A MAJOR HINDRANCE TO PRECIP DEVELOPMENT. POPS WERE LOWERED WEST OF THE BLUE RIDGE...AND KEPT AT LESS THAN 50/50 WEST OF THE METRO AREAS. PWATS ARE ALSO NOT AS IMPRESSIVE TOMORROW...AND THERE IS MORE STEERING FLOW...SO THE HEAVY RAIN THREAT DECREASES TOO. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... GENERAL CONSENSUS AMONGST THE 12Z MODEL SUITE HAS THE COLD FRONT EXTENDING JUST EAST OF THE CHESAPEAKE BAY BY TUES EVENING. MOSTLY ZONAL FLOW ALOFT LACKING IN ANY SIGNIFICANT FORCING LENDS TO ANY PCPN ACTIVITY TUES EVENING BEING DRIVEN BY SFC INSTABILITY AND LIFT PRODUCED BY THE COLD FRONT. AS SUCH...SCT SHOWERS AND MAYBE AN ISO TSTM PSBL INITIALLY TUES EVENING...BUT WILL QUICKLY TAPER POPS OFF AS THE FRONT CLEARS THE AREA ALONG WITH LOSS OF DIURNAL HEATING. DRY WX BY THE SECOND HALF OF THE NIGHT AND LASTING THRU WED AS SFC HIGH PRESSURE OVER THE WESTERN GREAT LAKES BUILDS IN....WITH THE REGION REMAINING ON THE EASTERN PERIPHERY. SUBSIDENCE ALOFT AIDES IN MOSTLY SUNNY SKIES...WITH SCT CU PSBL. INCREASING CLOUDS WED NIGHT WITH SFC LOW PRESSURE ATTEMPTING TO ORGANIZE OVER THE SOUTHEASTERN. OVERRIDING PCPN COULD POSSIBLY MOVE IN BY LATE WED TO SOUTHWESTERN PORTIONS OF THE CWA...WITH MOST OF THE AREA STAYING DRY TILL AFTR DAYBREAK THURS MORNING. CAA BEHIND THE COLD FRONT WILL DROP TEMPS BACK TO MORE SEASONAL LVLS...LOWS 40S AND 50S AND HIGHS UPPER 60S TO MID 70S. && .LONG TERM /THURSDAY THROUGH MONDAY/... LOW PRES TO OUR SOUTH MOVES OFFSHORE THU NIGHT INTO FRI... BRINGING SOME SCATTERED SHOWERS MAINLY TO THE S AND SE OF THE CWA. SHOWERS LOCATION WILL DEPEND ON THE TRACK OF THIS LOW PRES... WHICH IS UNCERTAIN AT THIS MOMENT. HIGH PRES BUILDS INTO THE REGION FRI AND INTO SUN... BRINGING DRIER CONDITIONS FOR THE FIRST HALF OF THE WEEKEND. RETURN FLOW INCREASES MOISTURE TO THE REGION FOR SUN... AND THE CHANCE FOR SHOWERS AND AFTERNOON TSTMS. A WARM FRONT APPROACHES LATE ON SUN INTO MON. SOME SHOWERS AND AFTERNOON TSTMS ARE POSSIBLE ON MON AS WELL. HIGH TEMPS WILL BE IN THE UPR 70S TO LOW 80S FOR FRI AND SAT...IN THE LOW 80S FOR SUN... AND IN THE UPR 80S FOR MON. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... GENERALLY VFR CONDITIONS THROUGH THE TAF PERIOD. CANNOT RULE OUT SOME LOW STRATUS AT BWI/MTN TONIGHT...BUT KEPT CIGS AT MVFR FOR NOW. ALSO CANNOT RULE OUT PATCHY FOG THOUGH OVERCAST SPREADING IN FROM THE WEST MAY KEEP THAT FROM BEING A BIG ISSUE. LOWER VSBYS POSSIBLE IN SCTD TO NUMEROUS SHRA/TSRA THROUGH EARLY EVENING TODAY. VFR CONDITIONS TUES NIGHT THROUGH FRIDAY. NW WINDS WED 10-15 KTS WED AFTN...PSBL GUSTS UP TO 20 KTS. SOME SCATTERED SHOWERS PSBL THU NIGHT. && .MARINE... LIGHT WINDS ON THE WATERS THROUGH TUESDAY. SOME LOCALLY GUSTY WINDS ARE POSSIBLE IN AND NEAR SHRA/TSRA BOTH TODAY AND TUESDAY. SCA CONDITIONS BCMG MORE LIKELY TUES NIGHT THRU WED MORNING BEHIND THE COLD FRONT ON THE CHESAPEAKE BAY AND MAYBE LOWER TIDAL POTOMAC. SCA GUSTS PSBL THRU WED AFTN...WITH ALL WATERS BCMG SUB- SCA BY WED NIGHT AND REMAINING THAT WAY THROUGH FRIDAY. && .CLIMATE... UNUSUALLY WARM WEATHER CONTINUES THROUGH TOMORROW. RECORD HIGH MINIMUMS MAY BE BROKEN AT DCA AND IAD TODAY /MAY 18TH/ AND COULD BE APPROACHED TOMORROW MORNING TOO. RECORD HI MINS FOLLOW... SITE...MAY 18TH.........MAY 19TH......... DCA....68 (1995*).......70 (1986/1962)... BWI....68 (1900/1896)...75 (1877)........ IAD....66 (1995)........66 (1969)........ *ALSO IN 1953...1943 AND 1900. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && SYNOPSIS...JE NEAR TERM...JE SHORT TERM...SEARS LONG TERM...IMR AVIATION...JE/SEARS/IMR MARINE...JE/SEARS/IMR
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 429 PM EDT MON MAY 18 2015 ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-191000- 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- 429 PM EDT MON MAY 18 2015 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...TUESDAY THROUGH SUNDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053- 055-501>506-191000- WASHINGTON-FREDERICK MD-CARROLL-NORTHERN BALTIMORE- EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY- NORTHWEST MONTGOMERY-CENTRAL AND SOUTHEASTERN 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 VA BLUE RIDGE-CENTRAL VA BLUE RIDGE-HAMPSHIRE-MORGAN- BERKELEY-JEFFERSON-HARDY-WESTERN GRANT-EASTERN GRANT- WESTERN MINERAL-EASTERN MINERAL-WESTERN PENDLETON- EASTERN PENDLETON- 429 PM EDT MON MAY 18 2015 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...TUESDAY THROUGH SUNDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The Sterling radar (KLWX), 103 km away, was scanning. The volume nearest the first event began at 23:42 UTC.
1 thunderstorm wind. Local standard time, as filed.
A tree was snapped off at the trunk. The tree was one foot in diameter.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2015Every state in 2015This day in weather historyWarnings in Maryland, May 2015
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: 575850.