Time: 949 AM Mon June 17, 2019 Forecaster: Alan Smith

Heavy Precipitation Outlook
Flash Flood Prediction Program

COOLER WITH WIDESPREAD AFTERNOON AND EVENING THUNDERSTORMS
-Moisture has increased across the District since yesterday with dewpoints currently well into the 50s. Low level cloud cover has developed across the plains this morning, but will gradually clear out by early afternoon. Temperatures will warm up into the mid to upper 70s on the plains this afternoon.
-A trough of low pressure is located west of the District today and a couple of upper level disturbances are expected to track ahead of this trough across the District this afternoon and evening. The atmosphere will be capped over the plains initially, but cooler air aloft arriving this afternoon should allow the cap to erode with multiple rounds of thunderstorms developing. Initial storm development should occur over the foothills and Palmer Divide by noon-1pm, before activity spreads onto the plains by mid-afternoon.
-Storms today will generally move from west to east at 12-17mph, but there will also be some potential for storms to stall along wind convergence boundaries. Abundant low level moisture combined with an unstable atmosphere will result in a threat for heavy rainfall and excessive runoff. Strong to severe thunderstorms will also be possible today with large hail, gusty straight-line winds, and frequent lightning the primary threats. The most widespread thunderstorm activity should end by sunset, but additional isolated thunderstorms will continue possible well into the evening.
STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall amounts of 0.2-0.5" in 10-30 minutes. Strong to severe thunderstorms will be capable of producing rainfall of 0.5-1.5" in 10-30 minutes.

WORST CASE SCENARIO: A strong, slow-moving thunderstorm or training of thunderstorm cells results in heavy rainfall of up to 3.0" in 90-120 minutes

A LOOK AHEAD: Deep moisture will remain in place on Tuesday as another potent disturbance drops into Colorado from the northwest. This will result in another active day with below average temperatures and widespread thunderstorms with heavy rainfall possible. Warmer and drier conditions will arrive on Wednesday and Thursday with just a slight chance of isolated thunderstorms both days and minimal potential for heavy rainfall.

Location Prime Time 30-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams 300 PM TO 1100 PM
0.1" (95%) to 0.5" (60%) to 1.5" (25%) HIGH
Arapahoe 300 PM TO 1100 PM
0.1" (95%) to 0.5" (60%) to 1.5" (25%) HIGH
Boulder 300 PM TO 1100 PM
0.1" (95%) to 0.5" (50%) to 1.5" (20%) HIGH
Broomfield 300 PM TO 1100 PM
0.1" (95%) to 0.5" (50%) to 1.5" (20%) HIGH
Denver 300 PM TO 1100 PM
0.1" (95%) to 0.5" (50%) to 1.5" (20%) HIGH
Jefferson 300 PM TO 1100 PM
0.1" (95%) to 0.5" (50%) to 1.5" (20%) HIGH
Douglas 200 PM TO 1100 PM
0.1" (95%) to 0.5" (60%) to 1.5" (25%) HIGH
Foothills above 6500ft      
Boulder 100 PM TO 1100 PM
0.1" (95%) to 0.5" (60%) to 1.5" (25%) HIGH
Douglas 100 PM TO 1100 PM
0.1" (95%) to 0.5" (60%) to 1.5" (25%) HIGH
Jefferson 100 PM TO 1100 PM
0.1" (95%) to 0.5" (60%) to 1.5" (25%) HIGH
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.