Time: 856 AM Fri July 24, 2020 Forecaster: Brad Simmons

Heavy Precipitation Outlook
Flash Flood Prediction Program

MONSOON MOISTURE MOVES INTO THE DISTRICT WITH AN ELEVATED THREAT FOR HEAVY RAINFALL
-The first real surge of Monsoon moisture this season has moved into CO and will pass over the District today resulting in scattered to widespread showers and thunderstorms this afternoon and evening. Showers and thunderstorms are expected to develop over the higher terrain to the W of the District by around noon and then spread onto the I-25 corridor by 1-2pm.
-With abundant moisture in place at the surface and aloft the storms that develop today will be very capable of producing heavy rainfall. However, the heavy rainfall is expected to be fairly brief from most storms as upper level steering winds from the SW at 20-25mph will help to keep storms moving and reduce point rainfall amounts from a single storm.
-Training of thunderstorm cells or large thunderstorms will have the potential to produce extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding. Best chances for shower and thunderstorm activity will be through 10pm this evening with lingering rain showers possible overnight. Message 1's will likely be issued by Noon or before.
STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers and weak to moderate thunderstorms will produce 0.1-0.5" in 10-30 minutes. Strong thunderstorms will have the potential to produce 0.5-1.5" in 10-30 minutes.

WORST CASE SCENARIO: Training of thunderstorm cells or a very large slower moving thunderstorm may produce up to 2.8" of rain in 45-60 minutes.

A LOOK AHEAD: Monsoon moisture will continue to impact the District through early next week with daily chances for thunderstorms with the potential for heavy rainfall. Thunderstorm activity will likely decrease a bit on Saturday only to uptick again on Sunday and Monday with Tuesday potentially being the peak of activity before drier air moves into NE CO on Wednesday of next week.

Location Prime Time 30-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams 100 PM TO 1000 PM
0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH
Arapahoe 100 PM TO 1000 PM
0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH
Boulder 100 PM TO 1000 PM
0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH
Broomfield 100 PM TO 1000 PM
0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH
Denver 100 PM TO 1000 PM
0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH
Douglas 100 PM TO 1000 PM
0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH
Jefferson 100 PM TO 1000 PM
0.1" (90%) to 0.5" (60%) to 1.5" (20%) HIGH
Foothills above 6500ft      
Boulder 1200 PM TO 1000 PM
0.1" (95%) to 0.5" (60%) to 1.5" (20%) HIGH
Douglas 1200 PM TO 1000 PM
0.1" (95%) to 0.5" (60%) to 1.5" (20%) HIGH
Jefferson 1200 PM TO 1000 PM
0.1" (95%) to 0.5" (60%) to 1.5" (20%) HIGH
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.