Time: 1026 AM Mon May 20, 2019 Forecaster: Alan Smith

Heavy Precipitation Outlook
Flash Flood Prediction Program

MUCH COLDER WITH WIDESPREAD RAIN DEVELOPING
-A powerful trough of low pressure moving across Colorado will bring wet conditions and well below average temperatures to the District today and tomorrow. However, the atmosphere has become cold and stable which will remove the threat of heavy rainfall from the forecast.
-Light rain showers this morning will give way to a more widespread rainfall this afternoon and into the evening. A soaking rainfall is expected across the District today and tonight, but rainfall rates will be less than 0.5"/hour. Some isolated lightning can't entirely be ruled out this afternoon, but the threat will be limited given the stable atmosphere in place. Highs today will only peak in the low 40s on the plains.
-Rain will change to snow in the foothills tonight with accumulating snow expected. We could even see a rain/snow mix at times on the plains below 6,000' late tonight. Total liquid precipitation amounts from today through tonight should generally range from 0.5-1.5" across the District.
STORM RAINFALL POTENTIAL AND DURATION: Typical rainfall rates today and tonight will range from 0.05-0.2" per hour. Heavier showers and isolated thunderstorms could produce locally higher rainfall rates of 0.2-0.4" per hour.

WORST CASE SCENARIO: A thunderstorm produces rainfall of 0.5" in 60 minutes or less.

A LOOK AHEAD: Periods of rain and snow will continue across the District Tuesday morning, with all-rain on the plains from late morning on. Rain showers will gradually decrease in coverage Tuesday afternoon before tapering off Tuesday evening. Temperatures will remain well below average with highs in the low 40s on the plains.

Location Prime Time 60-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Arapahoe Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Boulder Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Broomfield Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Denver Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Douglas Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Jefferson Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Foothills above 6500ft      
Boulder Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Douglas Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
Jefferson Current TO 1000 AM TUE
Trace (100%) to 0.2" (60%) to 0.4" (20%) NONE
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.