Flash Flood and Hail in New York, July 20, 2004

Name: Flash Flood and Hail in New York, July 20, 2004
Start: 2004-07-20T11:55
End: 2004-07-20T18:00
Location: New York

July 20, 2004 · NWS BUF · 5 events in 3 counties and zones

An upper level disturbance produced slow-moving thunderstorms along the south shore of Lake Ontario. The thunderstorms produced hail over Niagara, Orleans and Monroe counties.

Where it happened

Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $35,000
Crop damage: None recorded
Events: 5

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.

What happened

The episode as NWS BUF wrote it up.

An upper level disturbance produced slow-moving thunderstorms along the south shore of Lake Ontario. The thunderstorms produced hail over Niagara, Orleans and Monroe counties. Three-quarter inch hail was reported in Pittsford, Pekin and Sanborn. One-inch hail fell in Ridgeway. The slow moving thunderstorms dropped two to three inches of rain inundating numerous streets in Lewiston.

What forecasters said that day

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 Buffalo, NY wrote its last area forecast discussion before the first event at Jul 20, 9:14 AM EST, 2 hours 41 minutes earlier.

Area forecast discussion, Jul 20, 9:14 AM EST, 2 hours 41 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
1015 AM TUE JUL 20 2004

.UPDATE...
CLOUDS WITH APPROACHING SHORT WAVE ARE BREAKING UP A BIT OVER
SOUTHERN ONTARIO BUT SHOULD BE REFORMING DURING THE AFTERNOON
WARMTH. WILL STAY WITH THE CURRENT FORECAST FOR SKIES BECOMING
MOSTLY CLOUDY WITH SCATTERED SHRA/TSRA...ESPECIALLY IN CENTRAL AND
NORTHERN NY AS MID LEVEL CAP ERODES AND TEMPS WARM TO THE 75-80
DEGREE RANGE.

.SHORT TERM (TODAY THROUGH THURSDAY)...

THE PERSISTENT TROUGH OVER THE EASTERN STATES WILL CONTINUE THROUGH
TODAY AS REINFORCEMENT FROM A SHORT WAVE ADVANCES FROM THE UPPER
GREAT LAKES.  THIS FEATURE IS PRODUCING SHOWERS AND THUNDERSTORMS AS
CLOSE AS SOUTHERN ONTARIO JUST EAST OF LAKE HURON AT THIS TIME.  WE
WILL BRING SCATTERED ACTIVITY INTO THE WESTERN PART OF THE FORECAST
AREA THIS MORNING AND TO EASTERN AREAS THIS AFTERNOON.  GFS AND ETA
DIVERGE A BIT ON MOVING THE ACTIVITY OUT LATER TODAY WITH THE GFS
KEEPING THE THREAT IN A BIT LONGER.  WE WILL OPT TO GO WITH THE ETA
TIMING AND JUST KEEP A CHANCE IN FOR THE EASTERN LAKE ONTARIO REGION
THIS EVENING.  AN UPPER RIDGE FINALLY BUILDS IN FROM THE WEST
TONIGHT AND WEDNESDAY WITH THE GFS A LITTLE FLATTER THAN THE ETA.
AT ANY RATE IT LOOKS LIKE A DRY WARM DAY WEDNESDAY.  850 MILLIBAR
TEMPERATURES ARE PROGGED TO GO AS HIGHS AS 16-17C WHICH SHOULD
RESULT IN HIGHS WELL UP INTO THE 80S.  A WEAK SHORT WAVE APPROACHES
FROM THE WEST WEDNESDAY NIGHT AND MOVES THROUGH THURSDAY.  CHANCE
POPS STILL LOOK GOOD AT THIS TIME ALTHOUGH GFS MOS POPS FOR THURSDAY
ARE LIKELY TO CATEGORICAL.

DEW POINTS WILL BE CLIMBING THROUGH THE 60S TO AROUND 70 ON
THURSDAY.  IT WILL FEEL QUITE MUGGY...ESPECIALLY THURSDAY.

&&

.LONG RANGE (THURSDAY NIGHT THROUGH MONDAY)...

A MAJOR PATTERN CHANGE IS PROMISED OVER THE WEEKEND AS STRONG OPEN
WAVE MOVES ACROSS ONTARIO AND QUEBEC.  WE WILL HAVE TO HANG ONTO A
THREAT OF PRECIPITATION INTO FRIDAY BUT A STRONG SURFACE HIGH WILL
BUILD SOUTHEAST FROM ONTARIO PROVINCE AND LEAD TO A DRY PERIOD FROM
FRIDAY NIGHT INTO MONDAY.  NOT QUITE AS COOL AS THE LAST RUN OF THE
MODELS BUT A BIG DROP IN DEW POINTS LOOKS CERTAIN.

&&

.AVIATION...

LOOK FOR GENERALLY VFR CONDITIONS ACROSS THE REGION THIS AFTERNOON
AND EVENING ALTHOUGH A FEW SHOWERS AND THUNDERSTORMS WILL MOVE EAST
AND SOUTHEAST AND BRIEFLY DROP CONDITIONS TO MVFR.

SKIES SHOULD CLEAR THIS EVENING BUT LOOK FOR HAZE AND PATCHY FOG
LOWERING VISIBILITIES LATER TONIGHT...ESPECIALLY ACROSS SOUTHERN
TIER VALLEYS.

WINDS WILL REMAIN LIGHT.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...NONE.

UPDATE...HIBBERT
SHORT TERM/LONG TERM...SAGE
AVIATION...SFM

Hazardous weather outlook, Jul 20, 4:08 AM EST, 7 hours 47 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BUFFALO NY
508 AM EDT TUE JUL 20 2004

NYZ001>008-010>014-019>021-085-201106-
ALLEGANY-CATTARAUGUS-CHAUTAUQUA-GENESEE-JEFFERSON-LEWIS-LIVINGSTON-
MONROE-NIAGARA-NORTHERN CAYUGA-NORTHERN ERIE-ONTARIO-ORLEANS-OSWEGO-
SOUTHERN ERIE-WAYNE-WYOMING-
508 AM EDT TUE JUL 20 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND NORTH CENTRAL NEW
YORK.

.DAY ONE...

NO HAZARDOUS WEATHER EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

THIS PRODUCT...ALONG WITH OTHER WATCHES...WARNINGS...ADVISORIES...AND
STATEMENTS ISSUED BY THE NATIONAL WEATHER SERVICE OFFICE IN BUFFALO
CAN BE FOUND ON THE INTERNET AT THE FOLLOWING (LOWER CASE):
HTTP://WWW.ERH.NOAA.GOV/BUF/

SAGE

The radar

The Buffalo radar (KBUF), 45 km away, was scanning. The volume nearest the first event began at 16:54 UTC.

Open the radar archive at this moment

Event by event

4 hail, 1 flash flood. Local standard time, as filed.

Hail, Orleans

When: July 20, 11:55 AM EST
Where: Orleans County, Ridgeway
Measured: 1 in hail
Property damage: $5,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.267, -78.400

Hail, Monroe

When: July 20, 2:00 PM EST
Where: Monroe County, Pittsford
Measured: 0.75 in hail
Property damage: $5,000
Reported by: POST OFFICE
Coordinates: 43.083, -77.533

Hail, Niagara

When: July 20, 2:20 PM EST
Where: Niagara County, Pekin
Measured: 0.75 in hail
Property damage: $5,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.167, -78.900

Flash Flood, Niagara

When: July 20, 3:35 PM EST to 6:00 PM EST
Where: Niagara County, Lewiston
Property damage: $15,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.173, -78.691 (the zone’s center; the record gives no point)

Hail, Niagara

When: July 20, 3:35 PM EST
Where: Niagara County, Sanborn
Measured: 0.75 in hail
Property damage: $5,000
Reported by: LAW ENFORCEMENT
Coordinates: 43.133, -78.900

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in New York in 2004 Every state in 2004 This day in weather history Warnings in New York, July 2004

Sources

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: 5414170, 5414171, 5414172, 5414169, 5414173.