Time: 1029 AM Wed August 18, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- NEAR RECORD HEAT OVER THE PLAINS WITH ISOLATED HIGH-BASED SHOWERS / THUNDERSTORMS - It’s going to be another hot day on the plains as temperatures soar to near-record highs into the mid to upper 90’s. The normal high for Denver is 87, with a record high of 100 set in 2020. We should stay a few degrees below this record. An upper-level low will meander into the Great Basin today, positioning strong southwesterly flow over Colorado. Expect isolated to widely scattered high-based thunderstorms later today and this evening. - Showers and thunderstorms will likely initiate in the foothills between 1pm to 3pm, descending onto the plains between 3pm to 5pm. Scattered showers and thunderstorms will be more numerous over the foothills and Palmer Divide region, with isolated activity over the adjacent plains. Storm motion will be from SSW to NNE at about 20 mph, mainly producing gusty winds and minimal rain later this evening. - This evening and overnight, mostly dry conditions are expected over the plains. Isolated showers and thunderstorms may linger along and near higher terrain, with a small chance an isolated shower drifts east over the District. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.1" of rain. Moderate to heavy showers and thunderstorms can produce 0.2" of rain in 10-30 minutes. A LOOK AHEAD: Cooler temperatures after Thursday's cold front will increase moisture in the area. Strong southwesterly flow aloft will create fast-moving storms over the District. Training thunderstorms pose the greatest risk of heavy rainfall in some areas and may lead to excessive runoff. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains       Adams 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Arapahoe 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Broomfield 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Denver 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Boulder 200 PM TO 900 PM Trace (75%) to 0.1" (50%) to 0.2" (15%) NONE Douglas 200 PM TO 900 PM Trace (75%) to 0.1" (50%) to 0.2" (15%) NONE Jefferson 200 PM TO 900 PM Trace (75%) to 0.1" (50%) to 0.2" (15%) NONE Foothills above 6500ft       Boulder 100 PM TO 900 PM Trace (90%) to 0.1" (60%) to 0.2" (30%) NONE Douglas 100 PM TO 900 PM Trace (90%) to 0.1" (60%) to 0.2" (30%) NONE Jefferson 100 PM TO 900 PM Trace (90%) to 0.1" (60%) to 0.2" (30%) NONE MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789    F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]