Time: 1055 PM Thu May 11, 2023 Forecaster: Brad Simmons ------------------------- MESSAGE 2 UPDATE Flash Flood Prediction Program ------------------------- FLASH FLOOD WATCH The National Weather Service previously issued a FLASH FLOOD WATCH for: the following counties: BOULDER (CITY OF BOULDER AFFECTED, FOUR MILE BURN AREA AFFECTED), JEFFERSON, BROOMFIELD, DOUGLAS, ADAMS, DENVER, ARAPAHOE including: DIA, THE CITY OF AURORA, ARVADA, WHEAT RIDGE, LAKEWOOD ------------------------------------------------------------------------------ from: Current to 1159 AM . THE NATIONAL WEATHER SERVICE IN BOULDER HAS ISSUED A FLOOD WATCH/FLASH FLOOD WATCH FOR THE ENTIRE DISTRICT EFFECTIVE UNTIL NOON FRIDAY. Prime time for flooding: Current to 1159 AM . ------------------------------------------------------------------------------ Forecast rainfall: Light rain showers will produce rainfall rates of 0.1-0.3" in 60 minutes. Moderate to heavy non-thunderstorm rain showers will produce rainfall rates of 0.3-0.9" in 60 minutes. Very heavy rain showers or a weak to moderate thunderstorm has the potential to produce rainfall amounts of 0.5-1.5" in 30-60 minutes. ------------------------------------------------------------------------------ The most likely areas to be impacted by flooding are: X Mountain streams & floodplains; road crossings; canyon roads & highways; recreational trails; adjacent open space areas/campgrounds/parks; fishing access points & stream reaches; buildings near streams; utilities X Urban streams/gulches; road crossings; recreational trails; adjacent open space areas/campgrounds/parks; floodplain properties; utilities X Urban streets, intersections, low lying areas, known trouble spots X Mountain locations subject to mud/rock/debris slide ------------------------------------------------------------------------------ Additional information: A saturated ground due to 2.0-5.0" of rain already observed over a 1-2 day period is resulting in even light to moderate rain showers resulting in excessive runoff in creeks and streams. Smaller creeks and streams are already running high and additional rainfall may exacerbate runoff further and produce flooding/flash flooding conditions in the District. An additional 1.0-3.0" of rain is likely over the next 5-10 hours. A Flash Flood Watch means that flash flooding is possible within the watch area. This message is not intended for public dissemination. Please pass this information along to affected emergency response organizations (police, fire, public works, etc.) within your area. Also, please take appropriate actions to prepare for possible flooding. Further information will be provided to you as it becomes available. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]