Time: 1017 AM Sat June 15, 2019 Forecaster: Alan Smith

Heavy Precipitation Outlook
Flash Flood Prediction Program

COOLER WITH SCATTERED THUNDERSTORMS FAVORING SOUTHERN AND WESTERN AREAS
-A weak trough of low pressure will pass south of the District today, leading to increasing clouds and cooler temperatures with highs in the mid to upper 70s on the plains.
-Thunderstorms will develop over the foothills and Palmer Divide by midday with much of the activity remaining over the higher terrain with instability remaining limited over the plains until mid to late afternoon. By late in the day, thunderstorm chances will increase across the lower elevation areas. Storm motions will generally be to the E/SE at 10-15mph once storms move off of the foothills.
-Dewpoints will generally be in the mid 40s this afternoon, but slower storm motions compared to previous days will result in the potential for heavy rainfall if stronger storms are able to develop. Storm coverage and intensity should generally favor western and southern portions of the District. Thunderstorm activity should quickly decrease after sunset with conditions drying out overnight.
STORM RAINFALL POTENTIAL AND DURATION: Typical weak to moderate thunderstorms will produce rainfall amounts of 0.05-0.3" in 10-30 minutes. Strong thunderstorms will be capable of producing rainfall of 0.3-0.8" in 10-30 minutes.

WORST CASE SCENARIO: A slow-moving thunderstorm or training of thunderstorm cells results in heavy rainfall of up to 2.0" in 60-90 minutes.

A LOOK AHEAD: A weak cold front will move into the District from the north late Sunday afternoon, which will likely result in a round of late afternoon/early evening thunderstorms with heavy rainfall possible. Temperatures Sunday will be a few degrees warmer than Saturday ahead of the approaching front. Moisture will increase behind the cold front while a trough of low pressure moves across Colorado on Monday, resulting in cooler temperatures and more widespread thunderstorm activity across the District on Monday with heavy rainfall possible.

Location Prime Time 30-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams 300 PM TO 900 PM
0.1" (70%) to 0.3" (40%) to 0.8" (15%) MOD
Arapahoe 300 PM TO 900 PM
0.1" (80%) to 0.3" (50%) to 0.8" (20%) MOD
Boulder 300 PM TO 900 PM
0.1" (80%) to 0.3" (45%) to 0.8" (15%) MOD
Broomfield 300 PM TO 900 PM
0.1" (70%) to 0.3" (40%) to 0.8" (15%) MOD
Denver 300 PM TO 900 PM
0.1" (70%) to 0.3" (40%) to 0.8" (15%) MOD
Douglas 300 PM TO 900 PM
0.1" (80%) to 0.3" (50%) to 0.8" (20%) MOD
Jefferson 300 PM TO 900 PM
0.1" (80%) to 0.3" (50%) to 0.8" (20%) MOD
Foothills above 6500ft      
Boulder 100 PM TO 900 PM
0.1" (90%) to 0.3" (60%) to 0.8" (25%) MOD
Douglas 100 PM TO 900 PM
0.1" (95%) to 0.3" (60%) to 0.8" (25%) MOD
Jefferson 100 PM TO 900 PM
0.1" (95%) to 0.3" (60%) to 0.8" (25%) MOD
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.