Time: 844 AM Sat June 5, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- HOT WITH ISOLATED AFTERNOON THUNDERSTORMS MORE NUMEROUS OVER THE FOOTHILLS - A summer-like day over the District with temperatures warming to well above normal in the upper 80's to lower 90's over the plains with 70's and lower 80's in the Front Range foothills. Normal high for Denver today is 80 degrees. Skies will be sunny this morning and begin to cloud up as thunderstorms develop over the higher terrain by early afternoon. - Weak steering winds aloft from N to S will keep the majority of the thunderstorm activity over the higher terrain today. Rain cooled outflow from the initial foothill storms may push eastward onto the I-25 corridor and generate additional thunderstorm development by mid afternoon. The storms on the plains will be isolated while the coverage over the foothills is more scattered. Best chances for thunderstorm activity will be from 2-9pm foothills and from 4-9pm over the plains. - Surface moisture is limited resulting in most storms that develop today producing light to brief moderate rainfall and gusty winds. An outflow induced thunderstorm that remains nearly stationary could become strong and may be capable of brief heavy rainfall and hail. STORM RAINFALL POTENTIAL AND DURATION: Typical weak to moderate thunderstorms will produce a trace to 0.15". A stronger thunderstorm will have the potential to produce 0.15-0.40" of rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in heavy rainfall of 0.40-1.20" in 15-45 minutes. A LOOK AHEAD: An uptick in thunderstorm activity is expected on Sunday over the District with temperatures continuing to run above normal in the upper 80's to around 90 over the plains. Afternoon thunderstorms will generally produce light to moderate rain and gusty winds much like today but a stronger storm will be capable of producing brief heavy rainfall. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 400 PM TO 900 PM Trace (50%) to 0.2" (15%) to 0.4" (5%) NONE Arapahoe 400 PM TO 900 PM Trace (50%) to 0.2" (15%) to 0.4" (5%) NONE Boulder 400 PM TO 900 PM Trace (50%) to 0.2" (15%) to 0.4" (5%) NONE Broomfield 400 PM TO 900 PM Trace (50%) to 0.2" (15%) to 0.4" (5%) NONE Denver 400 PM TO 900 PM Trace (50%) to 0.2" (15%) to 0.4" (5%) NONE Douglas 300 PM TO 900 PM Trace (75%) to 0.2" (40%) to 0.4" (15%) NONE Jefferson 300 PM TO 900 PM Trace (60%) to 0.2" (20%) to 0.4" (10%) NONE Foothills above 6500ft       Boulder 200 PM TO 900 PM Trace (95%) to 0.2" (70%) to 0.4" (20%) LOW Douglas 200 PM TO 900 PM Trace (95%) to 0.2" (70%) to 0.4" (20%) LOW Jefferson 200 PM TO 900 PM Trace (95%) to 0.2" (70%) to 0.4" (20%) LOW MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]