Time: 959 AM Fri June 21, 2019 Forecaster: Justin Brooks

Heavy Precipitation Outlook
Flash Flood Prediction Program

COOLER TODAY WITH A CHANCE FOR RAIN/THUNDERSTORM THIS AFTERNOON/EVENING
-An unsettled weather pattern remains over the District today as a low-pressure trough moves in from the west combined with a cold front from the north that moved through yesterday evening resulting in slightly cooler than average temperatures across the District today. Partly cloudy skies this morning will become mostly cloudy this afternoon with highs in the upper 60's to low 70's on the plains.
-Thunderstorms will develop over the foothills by midday, before spreading onto the plains in the early afternoon. With sufficient upper level support in place across the region and dew points in the low to mid 40's, storms will have the chance to become severe, especially east of the I-25 corridor as they reach a more favorable atmosphere.
-Storm motions will be from W/NW to E/SE at 15-20mph and strong thunderstorms will have the potential to produce heavy rainfall, large hail, and gusty winds. Storm activity could continue well into the evening before gradually diminishing overnight with a chance for widespread showers into Saturday morning, but any overnight accumulations should remain minimal.
STORM RAINFALL POTENTIAL AND DURATION: Typical weak to moderate thunderstorms will produce rainfall amounts of 0.1-0.4" in 10-30 minutes. Strong thunderstorms will be capable of producing rainfall of 0.4-0.8" in 10-30 minutes.

WORST CASE SCENARIO: A strong thunderstorm stalls along a wind convergence boundary, or training of thunderstorms, results in heavy rainfall of up to 2.40" in 60-90 minutes.

A LOOK AHEAD: The low-pressure system will slowly move across the region over the weekend bring a good chance for showers Saturday and Sunday. Temperatures this weekend will be below average in the mid 60's Saturday, barely warming into the upper 60's to low 70's Sunday.

Location Prime Time 30-Minute Rainfall
and % Probability
Message
Potential
Plains      
Adams 1200 PM TO 800 PM
Trace (90%) to 0.4" (50%) to 0.8" (30%) MOD
Arapahoe 1200 PM TO 800 PM
Trace (90%) to 0.4" (50%) to 0.8" (30%) MOD
Boulder 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (20%) MOD
Broomfield 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (20%) MOD
Denver 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (20%) MOD
Douglas 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (20%) MOD
Jefferson 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (20%) MOD
Foothills above 6500ft      
Boulder 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (10%) LOW
Douglas 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (10%) LOW
Jefferson 1200 PM TO 800 PM
Trace (90%) to 0.4" (30%) to 0.8" (10%) LOW
MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS.