July 2021 - hpo-ims - Udfcd-Lists.Org

by f2p2＠udfcd.org

Time: 825 AM Fri July 23, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- HOT AGAIN TODAY WITH ANOTHER CHANCE FOR AFTERNOON AND EVENING RAIN SHOWERS/ISOLATED THUNDERSTORMS - Not much chance in the overall pattern today as high temperatures are expected to reach the low to mid 90's once again on the plains with mid to upper 80's along the foothills. Elevated monsoonal moisture remains in place over the region resulting in another chance for isolated heavy rainfall this afternoon and evening with rain showers possible through the overnight and into Saturday morning. - Thunderstorms will develop over the mountains/foothills during the afternoon. Thunderstorm chances increase over the plains between 3-4pm with prime time for thunderstorms from 4-10pm. Additional showers and possibly a weak isolated thunderstorms will remain possible through the overnight. At least 1 strong round of thunderstorms is expected this afternoon, with a good chance for an additional rounds of rain showers/isolated thunderstorms in the evening, however, the initial afternoon round likely being the strongest and will have the best chance for heavy rainfall. Any heavy rainfall threat should diminish after 10pm this evening. - Relatively slow overall storm motions from W to E between 3-8mph will allow for extended periods of heavy rain under stronger storms. Storm motions may also become erratic or stationary at times due to outflow boundaries/gust front interactions. This behavior will also increase the chance for isolated heavy rainfall this afternoon and into this evening. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce TR-0.3" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.3-1.0" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 2.0" in 60 minutes or less. A LOOK AHEAD: A cold front will move through the region overnight and into Saturday effectively dropping Saturday's high temperatures back into the mid to upper 80's for the plains with upper 70's to around 80 for the foothills. This front will allow a chance for rain showers and isolated thunderstorms throughout the day Saturday, however, the intensity of rainfall will hinge on whether temperatures increase sufficiently during the day to produce stronger storms. the most likely outcome at this time will be weak to moderate rain showers/isolated thunderstorms. Conditions start to dry out slightly Sunday with a slight chance for afternoon rain showers/isolated thunderstorms with minimal threat for heavy rainfall for now. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 300 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 1.0" (15%) MOD Arapahoe 300 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 1.0" (15%) MOD Boulder 300 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 1.0" (15%) MOD Broomfield 300 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 1.0" (15%) MOD Denver 300 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 1.0" (15%) MOD Douglas 300 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 1.0" (15%) MOD Jefferson 300 PM TO 1000 PM Trace (75%) to 0.3" (50%) to 1.0" (15%) MOD Foothills above 6500ft Â Â Â Boulder 300 PM TO 1000 PM Trace (80%) to 0.3" (60%) to 1.0" (30%) HIGH Douglas 300 PM TO 1000 PM Trace (80%) to 0.3" (60%) to 1.0" (30%) HIGH Jefferson 300 PM TO 1000 PM Trace (80%) to 0.3" (60%) to 1.0" (30%) HIGH MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 920 PM Thu July 22, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE AT 10PM - Message 1's will be allowed to expire at 10pm as the threat for heavy rainfall has ended for the day. - Lingering light rain showers over central and southern areas of the District will continue to diminish with generally dry conditions expected by around 10pm. - A similar setup is expected tomorrow over the District with isolated to widely scattered afternoon thunderstorms capable of producing heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: No meaningful precipitation expected for the remainder of the evening and overnight period, TR-0.05" from lingering light rain showers. COUNTY MESSAGE VALID TIMES PRIME TIME Wheat Ridge 1 Current TO 1000 PM 600 PM TO 900 PM Lakewood 1 Current TO 1000 PM 600 PM TO 900 PM Arvada 1 Current TO 1000 PM 600 PM TO 900 PM the City of Aurora 1 Current TO 1000 PM 600 PM TO 900 PM Arapahoe County 1 Current TO 1000 PM 600 PM TO 900 PM DIA 1 Current TO 1000 PM 600 PM TO 900 PM Denver County 1 Current TO 1000 PM 600 PM TO 900 PM Adams County 1 Current TO 1000 PM 600 PM TO 900 PM Douglas County 1 Current TO 1000 PM 600 PM TO 900 PM Broomfield County 1 Current TO 1000 PM 600 PM TO 900 PM Jefferson County 1 Current TO 1000 PM 600 PM TO 900 PM Boulder County 1 Current TO 1000 PM 600 PM TO 900 PM MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

3 years, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 508 PM Thu July 22, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT - Message 1's have been issued for the entire District and will be valid until 10pm. - Thunderstorms are beginning to initiate over eastern areas of the District currently and are expected to become stronger and more numerous as the evening progresses. Storms will be slow moving with the potential to produce heavy rainfall that may lead to excessive runoff and possibly flash flooding. - Prime time for thunderstorms is from 6-9pm, likely favoring the plains versus the foothills. STORM RAINFALL POTENTIAL AND DURATION: Moderate to strong thunderstorms have the potential to produce 0.4-1.2" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 2.2" in 60 minutes or less. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1000 PM 600 PM TO 900 PM Jefferson County 1 Current TO 1000 PM 600 PM TO 900 PM Broomfield County 1 Current TO 1000 PM 600 PM TO 900 PM Douglas County 1 Current TO 1000 PM 600 PM TO 900 PM Adams County 1 Current TO 1000 PM 600 PM TO 900 PM Denver County 1 Current TO 1000 PM 600 PM TO 900 PM DIA 1 Current TO 1000 PM 600 PM TO 900 PM Arapahoe County 1 Current TO 1000 PM 600 PM TO 900 PM the City of Aurora 1 Current TO 1000 PM 600 PM TO 900 PM Arvada 1 Current TO 1000 PM 600 PM TO 900 PM Wheat Ridge 1 Current TO 1000 PM 600 PM TO 900 PM Lakewood 1 Current TO 1000 PM 600 PM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 1000 PM THU 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Arapahoe Current TO 1000 PM THU 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Boulder Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (25%) ISSUED Broomfield Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (25%) ISSUED Denver Current TO 1000 PM THU 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Douglas Current TO 1000 PM THU 0.1" (90%) to 0.4" (60%) to 1.2" (30%) ISSUED Jefferson Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (25%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (25%) ISSUED Douglas Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (25%) ISSUED Jefferson Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (25%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 838 AM Thu July 22, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- HOT AND A LITTLE HAZY TODAY WITH A CHANCE FOR ISOLATED AFTERNOON RAIN SHOWERS/THUNDERSTORMS - Another hot and hazy day for Colorado as highs reach the low to mid 90's on the plains this afternoon with mid to upper 80's along the foothills. Colorado will continue to tap into monsoon moisture today resulting in another chance for isolated heavy rainfall this afternoon and evening. - Thunderstorms will develop over the mountains/foothills during the afternoon. Thunderstorm chances increase over the plains between 3-4pm with prime time from 4-10pm. Additional showers and weaker thunderstorms will remain possible through midnight. At least 1 round of thunderstorms is expected this afternoon, with a good chance for an additional round of rain showers/isolated thunderstorms in the evening, however, the initial afternoon round likely being the strongest and will have the best chance for heavy rainfall. - Relatively slow storm motions from W to E between 5-10mph will allow for extended periods of heavy rain under stronger storms. Storm motions may also become erratic or potential stationary at times due to outflow boundaries/gust front interactions. This behavior will also increase the chance for isolated heavy rainfall this afternoon. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce TR-0.3" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.3-1.0" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 2.0" in 60 minutes or less. A LOOK AHEAD: As the high-pressure ridge remains over the Central/Southwest US, Colorado will continue to tap into monsoon moisture through the weekend with afternoon/evening rain showers/isolated thunderstorm chances both Saturday and Sunday. The intensity of rainfall will hinge heavily on how much surface moisture can remain in place throughout the day with upper 40's to low 50's dew points projected Saturday, at least a low chance will remain for isolated heavy rainfall. Conditions dry out at the surface slightly on Sunday, however a very low threat will remain for isolated heavy rainfall at this time. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 200 PM TO 1000 PM Trace (50%) to 0.3" (20%) to 1.0" (10%) LOW Arapahoe 200 PM TO 1000 PM Trace (50%) to 0.3" (20%) to 1.0" (10%) LOW Boulder 200 PM TO 1000 PM Trace (50%) to 0.3" (20%) to 1.0" (10%) LOW Broomfield 200 PM TO 1000 PM Trace (50%) to 0.3" (20%) to 1.0" (10%) LOW Denver 200 PM TO 1000 PM Trace (50%) to 0.3" (20%) to 1.0" (10%) LOW Douglas 200 PM TO 1000 PM Trace (50%) to 0.3" (20%) to 1.0" (10%) LOW Jefferson 200 PM TO 1000 PM Trace (50%) to 0.3" (20%) to 1.0" (10%) LOW Foothills above 6500ft Â Â Â Boulder 200 PM TO 1000 PM Trace (60%) to 0.3" (30%) to 1.0" (15%) MOD Douglas 200 PM TO 1000 PM Trace (60%) to 0.3" (30%) to 1.0" (15%) MOD Jefferson 200 PM TO 1000 PM Trace (60%) to 0.3" (30%) to 1.0" (15%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 916 PM Wed July 21, 2021 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE AT 10:00 PM - Message 1's issued for the entire District will be allowed to expire at 10:00pm as the threat for heavy rainfall has come to an end. - Heavier than usual rainfall impacted areas in Douglas and Elbert County just S and SE of the District earlier this evening. A few lingering light rain showers persist to the south and along the higher terrain in the foothills at this time. These showers will continue to gradually decrease over the next couple of hours with dry conditions expected through the overnight and into Thursday. - Overnight lows will drop into the 60's for the plains with upper 50's to around 60 for the foothills. STORM RAINFALL POTENTIAL AND DURATION: light rain showers will produce a trace to 0.10" in 10-30 minutes. WORST CASE SCENARIO: a moderate rain shower could produce 0.1-0.3" in 10-30 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 1000 PM Current TO 1000 PM Jefferson County 1 Current TO 1000 PM Current TO 1000 PM Broomfield County 1 Current TO 1000 PM Current TO 1000 PM Douglas County 1 Current TO 1000 PM Current TO 1000 PM Adams County 1 Current TO 1000 PM Current TO 1000 PM Denver County 1 Current TO 1000 PM Current TO 1000 PM DIA 1 Current TO 1000 PM Current TO 1000 PM Arapahoe County 1 Current TO 1000 PM Current TO 1000 PM the City of Aurora 1 Current TO 1000 PM Current TO 1000 PM Arvada 1 Current TO 1000 PM Current TO 1000 PM Wheat Ridge 1 Current TO 1000 PM Current TO 1000 PM Lakewood 1 Current TO 1000 PM Current TO 1000 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 1159 PM WED Trace (10%) to 0.1" (5%) to 0.3" (0%) ISSUED Arapahoe Current TO 1159 PM WED Trace (10%) to 0.1" (5%) to 0.3" (0%) ISSUED Boulder Current TO 1159 PM WED Trace (10%) to 0.1" (5%) to 0.3" (0%) ISSUED Broomfield Current TO 1159 PM WED Trace (10%) to 0.1" (5%) to 0.3" (0%) ISSUED Denver Current TO 1159 PM WED Trace (10%) to 0.1" (5%) to 0.3" (0%) ISSUED Douglas Current TO 1159 PM WED Trace (30%) to 0.1" (10%) to 0.3" (5%) ISSUED Jefferson Current TO 1159 PM WED Trace (30%) to 0.1" (10%) to 0.3" (5%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 1159 PM WED Trace (30%) to 0.1" (10%) to 0.3" (5%) ISSUED Douglas Current TO 1159 PM WED Trace (30%) to 0.1" (10%) to 0.3" (5%) ISSUED Jefferson Current TO 1159 PM WED Trace (30%) to 0.1" (10%) to 0.3" (5%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 727 PM Wed July 21, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S CONTINUE VALID, HEAVY RAINFALL THREAT DIMINISHING - Message 1's will continue valid although the threat for heavy rainfall is diminishing now that temperatures are cooling. - Strong/slow moving thunderstorms concentrated just S and W of the District over Clear Creek County earlier this afternoon and more recently over SE Douglas County. Currently there is a gust front travelling northward from the Douglas County storms but is failing to initiate new thunderstorms with temperatures now in the 80's. - There is weak thunderstorm activity to the NW of the District at this time and should these storms survive their journey E/SE into the District or interact with the boundary moving northward heavy rainfall may still occur in areas that have had minimal storm activity up to this point. However, with the cooling temperatures thunderstorms will likely not be as strong as earlier in the day but it will not necessarily require a strong thunderstorm to produce brief heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.1-0.5" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.5-1.5" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 2.5" in 60 minutes or less. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 100 PM TO 1000 PM Current TO 900 PM Jefferson County 1 100 PM TO 1000 PM Current TO 900 PM Broomfield County 1 100 PM TO 1000 PM Current TO 900 PM Douglas County 1 100 PM TO 1000 PM Current TO 900 PM Adams County 1 100 PM TO 1000 PM Current TO 900 PM Denver County 1 100 PM TO 1000 PM Current TO 900 PM DIA 1 100 PM TO 1000 PM Current TO 900 PM Arapahoe County 1 100 PM TO 1000 PM Current TO 900 PM the City of Aurora 1 100 PM TO 1000 PM Current TO 900 PM Arvada 1 100 PM TO 1000 PM Current TO 900 PM Wheat Ridge 1 100 PM TO 1000 PM Current TO 900 PM Lakewood 1 100 PM TO 1000 PM Current TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 1000 PM WED 0.1" (40%) to 0.5" (20%) to 1.5" (10%) ISSUED Arapahoe Current TO 1000 PM WED 0.1" (80%) to 0.5" (50%) to 1.5" (20%) ISSUED Boulder Current TO 1000 PM WED 0.1" (75%) to 0.5" (50%) to 1.5" (20%) ISSUED Broomfield Current TO 1000 PM WED 0.1" (60%) to 0.5" (30%) to 1.5" (15%) ISSUED Denver Current TO 1000 PM WED 0.1" (40%) to 0.5" (20%) to 1.5" (10%) ISSUED Douglas Current TO 1000 PM WED 0.1" (80%) to 0.5" (50%) to 1.5" (20%) ISSUED Jefferson Current TO 1000 PM WED 0.1" (75%) to 0.5" (50%) to 1.5" (20%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 1000 PM WED 0.1" (80%) to 0.5" (40%) to 1.5" (20%) ISSUED Douglas Current TO 1000 PM WED 0.1" (80%) to 0.5" (40%) to 1.5" (20%) ISSUED Jefferson Current TO 1000 PM WED 0.1" (80%) to 0.5" (40%) to 1.5" (20%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

3 years, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 104 PM Wed July 21, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT - Message 1's have been issued for the entire District and will be valid until 10pm this evening. - Thunderstorms are beginning to develop over the higher terrain to the west with thunderstorms expected to emerge onto the plains between 2-4pm. Prime time for thunderstorm activity is from 2:30-9pm. Additional showers and weaker thunderstorms will remain possible until midnight. 1-2 rounds of thunderstorms are expected with the initial round likely being the strongest. - Relatively slow storm motions from W to E at 10-15mph will allow for extended periods of heavy rain under stronger storms. Storm motions may become erratic at times due to outflow boundaries/gust front interactions. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.2-0.6" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 3.0" in 60 minutes or less. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 100 PM TO 1000 PM 200 PM TO 900 PM Jefferson County 1 100 PM TO 1000 PM 200 PM TO 900 PM Broomfield County 1 100 PM TO 1000 PM 230 PM TO 900 PM Douglas County 1 100 PM TO 1000 PM 200 PM TO 900 PM Adams County 1 100 PM TO 1000 PM 230 PM TO 900 PM Denver County 1 100 PM TO 1000 PM 230 PM TO 900 PM DIA 1 100 PM TO 1000 PM 230 PM TO 900 PM Arapahoe County 1 100 PM TO 1000 PM 230 PM TO 900 PM the City of Aurora 1 100 PM TO 1000 PM 230 PM TO 900 PM Arvada 1 100 PM TO 1000 PM 230 PM TO 900 PM Wheat Ridge 1 100 PM TO 1000 PM 230 PM TO 900 PM Lakewood 1 100 PM TO 1000 PM 230 PM TO 900 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 300 PM TO 900 PM 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Arapahoe 300 PM TO 900 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) ISSUED Broomfield 300 PM TO 900 PM 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Denver 300 PM TO 900 PM 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Boulder 200 PM TO 900 PM 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Douglas 200 PM TO 900 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) ISSUED Jefferson 200 PM TO 900 PM 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 900 PM WED 0.2" (95%) to 0.6" (60%) to 1.8" (30%) ISSUED Douglas Current TO 900 PM WED 0.2" (95%) to 0.6" (60%) to 1.8" (30%) ISSUED Jefferson Current TO 900 PM WED 0.2" (95%) to 0.6" (60%) to 1.8" (30%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

3 years, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 913 AM Wed July 21, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- MONSOON MOISTURE INCREASES HEAVY RAINFALL THREAT TODAY - Mid and upper level monsoon moisture will move overhead today and result in thunderstorm activity returning to the District. Thunderstorms that develop will be slow moving and have the potential to produce heavy rainfall that may lead to excessive runoff and possibly flash flooding. - Thunderstorms will develop over the mountains/foothills during the early afternoon. Thunderstorm chances increase over the plains between 2-3pm with prime time from 3-9pm. Additional showers and weaker thunderstorms will remain possible until midnight. 1-2 rounds of thunderstorms are expected with the initial round likely being the strongest. - Relatively slow storm motions from W to E at around 10mph will allow for extended periods of heavy rain under stronger storms. Storm motions may become erratic at times due to outflow boundaries/gust front interactions. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.2-0.6" in 10-30 minutes. Strong thunderstorms have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm may result in up to 3.0" in 60 minutes or less. A LOOK AHEAD: Ridge of high pressure shifts back to the west on Thursday decreasing the chances for thunderstorms over the plains as the activity moves back over the mountainous areas of the state. There will still be a chance for isolated afternoon thunderstorm activity favoring the W and S areas of the District. Heavy rainfall threat lowers considerably. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 300 PM TO 900 PM 0.2" (75%) to 0.6" (50%) to 1.8" (25%) HIGH Arapahoe 300 PM TO 900 PM 0.2" (75%) to 0.6" (50%) to 1.8" (25%) HIGH Broomfield 300 PM TO 900 PM 0.2" (75%) to 0.6" (50%) to 1.8" (25%) HIGH Denver 300 PM TO 900 PM 0.2" (75%) to 0.6" (50%) to 1.8" (25%) HIGH Boulder 200 PM TO 900 PM 0.2" (80%) to 0.6" (50%) to 1.8" (25%) HIGH Douglas 200 PM TO 900 PM 0.2" (80%) to 0.6" (50%) to 1.8" (25%) HIGH Jefferson 200 PM TO 900 PM 0.2" (80%) to 0.6" (50%) to 1.8" (25%) HIGH Foothills above 6500ft Â Â Â Boulder 100 PM TO 900 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) HIGH Douglas 100 PM TO 900 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) HIGH Jefferson 100 PM TO 900 PM 0.2" (90%) to 0.6" (60%) to 1.8" (30%) HIGH MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

3 years, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 854 AM Tue July 20, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- THUNDERSTORMS RETURN TO THE MOUNTAINOUS ARES OF THE STATE WITH DRY CONDITIONS OVER THE PLAINS - Thunderstorm activity will return to the mountains and higher foothills today as monsoon moisture lurks to the west. There remains uncertainty as to whether there will be much activity over the District itself... One thing is for certain, there will be haze from smoke and temperatures will continue to run in the 90's for highs over the plains. - Thunderstorms will develop along and W of the Continental Divide by early afternoon. North to south upper level steering winds is expected to keep the shower and thunderstorm activity over the higher terrain with the District remaining dry for another day. Although unlikely, there is a slight chance this evening for a very isolated storm moving off the higher terrain via gust front activity favoring areas W of I-25. - If a thunderstorm is able to develop today they will likely favor the terrain west of the District forecast area. Should thunderstorm activity become more likely as the day progresses over the District the HPO will be updated to reflect higher chances for precipitation. STORM RAINFALL POTENTIAL AND DURATION: No meaningful precipitation expected today or tonight. WORST CASE SCENARIO: Gust front activity from higher terrain storms results in thunderstorm activity developing over the plains late this afternoon and evening with the potential to produce moderate to briefly heavy rain. A LOOK AHEAD: Thunderstorm activity returns to the District on Wednesday with strong storms capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding. Prime time for thunderstorms looks to be from 2-8pm at this time. MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

3 years, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 810 AM Mon July 19, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- DRY WITH SEASONAL TEMPERATURES - Conditions will be dry over the District today as a layer of warm air aloft will put a lid on any thunderstorm activity. Temperatures will warm into the lower 90's over the plains with 80's in the Front Range foothills under sunny to mostly sunny skies. - There will continue to be haze due to multiple fires over the Pacific NW but our haze/smoke here is not as bad as our neighbors to the N in Wyoming and Montana. STORM RAINFALL POTENTIAL AND DURATION: No precipitation expected today or tonight. A LOOK AHEAD: Isolated to widely scattered thunderstorms return to the District on Tuesday. Storms will be more numerous over the foothills with a low risk of heavy rainfall. Thunderstorm chances increase further on Wednesday as monsoon moisture is drawn northward with scattered afternoon thunderstorms with the potential to produce heavy rain. Temperatures will continue to run in the 90's over the plains the next few days. MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 Â Â Â F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

3 years, 3 months

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