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

by f2p2＠udfcd.org

Time: 951 AM Sat July 31, 2021 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 2'S CONTINUE VALID UNTIL 9:00 PM THIS EVENING - Message 2's continue valid until 9pm as the threat for heavy rainfall continues into this afternoon and evening. - Cooler and cloudy this morning with a few lingering rain showers out on the eastern plains at this time. High temperatures today will reach the mid to upper 70's this afternoon which could help limit the potential for stronger storms. However, with adequate moisture still in place, even moderate storms could produce heavy rainfall with the chance for longer duration rainfall from storms that form along outflow boundaries that remain stationary for an extended period of time. Storm chances will start between noon and 1pm, with prime time between 4-9pm. With the recent moisture it may not take as much rain to produce excessive runoff and possibly flash flooding. - A chance will remain for a few scattered lingering rain showers through the evening and into the overnight. Overnight skies will remain cloudy with lows dropping into the 60's on the plains with mid to upper 50's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.2-0.6" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm will have the potential to produce up to 3.6" in 45-60 minutes. Storms that persist beyond 60 minutes may produce locally higher amounts. COUNTY MESSAGE VALID TIMES PRIME TIME the City of Aurora 2 Current TO 900 PM Current TO 900 PM Arapahoe County 2 Current TO 900 PM Current TO 900 PM DIA 2 Current TO 900 PM Current TO 900 PM Denver County 2 Current TO 900 PM Current TO 900 PM Adams County 2 Current TO 900 PM Current TO 900 PM Douglas County 2 Current TO 900 PM Current TO 900 PM Broomfield County 2 Current TO 900 PM Current TO 900 PM Jefferson County 2 Current TO 900 PM Current TO 900 PM Boulder County 2 Current TO 900 PM Current TO 900 PM Lakewood 2 Current TO 900 PM Current TO 900 PM Wheat Ridge 2 Current TO 900 PM Current TO 900 PM Arvada 2 Current TO 900 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 900 PM SAT 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Arapahoe Current TO 900 PM SAT 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Boulder Current TO 900 PM SAT 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Broomfield Current TO 900 PM SAT 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Denver Current TO 900 PM SAT 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Douglas Current TO 900 PM SAT 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Jefferson Current TO 900 PM SAT 0.2" (80%) to 0.6" (60%) to 1.8" (30%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 900 PM SAT 0.2" (90%) to 0.6" (70%) to 1.8" (40%) ISSUED Douglas Current TO 900 PM SAT 0.2" (90%) to 0.6" (70%) to 1.8" (40%) ISSUED Jefferson Current TO 900 PM SAT 0.2" (90%) to 0.6" (70%) to 1.8" (40%) 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

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Time: 132 AM Sat July 31, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 2'S CONTINUE VALID INTO SATURDAY - Message 2's continue valid until 9pm Saturday. The Message 3's issued earlier for SE Boulder and Broomfield Counties have been allowed to expire at 1:30am. - Thunderstorm activity diminished hours ago and light rain showers continue, mainly impacting northern areas of the District currently. Rain showers are expected to continue to slowly decrease as the overnight wears on with a generally dry period into late morning Saturday. - By 10am Saturday there will already be a chance for thunderstorms over the District with prime time from around noon to 6pm. Thunderstorms that develop on Saturday will be very capable of producing heavy rainfall. With the recent moisture it may not take as much rain on Saturday to produce excessive runoff and possibly flash flooding. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce a trace to 0.3" in 60 minutes or less through daybreak Saturday. WORST CASE SCENARIO: A weak to moderate thunderstorm is able to develop overnight with the potential to produce 0.3-0.9" of heavy rain in 10-30 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 900 PM 1200 PM TO 600 PM Jefferson County 1 Current TO 900 PM 1200 PM TO 600 PM Broomfield County 1 Current TO 900 PM 1200 PM TO 600 PM Douglas County 1 Current TO 900 PM 1200 PM TO 600 PM Adams County 1 Current TO 900 PM 1200 PM TO 600 PM Denver County 1 Current TO 900 PM 1200 PM TO 600 PM DIA 1 Current TO 900 PM 1200 PM TO 600 PM Arapahoe County 1 Current TO 900 PM 1200 PM TO 600 PM the City of Aurora 1 Current TO 900 PM 1200 PM TO 600 PM Arvada 1 Current TO 900 PM 1200 PM TO 600 PM Wheat Ridge 1 Current TO 900 PM 1200 PM TO 600 PM Lakewood 1 Current TO 900 PM 1200 PM TO 600 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 60-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 1000 AM SAT Trace (90%) to 0.1" (60%) to 0.3" (30%) ISSUED Arapahoe Current TO 1000 AM SAT Trace (60%) to 0.1" (30%) to 0.3" (10%) ISSUED Boulder Current TO 1000 AM SAT Trace (100%) to 0.1" (75%) to 0.3" (30%) ISSUED Broomfield Current TO 1000 AM SAT Trace (100%) to 0.1" (75%) to 0.3" (30%) ISSUED Denver Current TO 1000 AM SAT Trace (60%) to 0.1" (30%) to 0.3" (10%) ISSUED Douglas Current TO 1000 AM SAT Trace (60%) to 0.1" (30%) to 0.3" (10%) ISSUED Jefferson Current TO 1000 AM SAT Trace (60%) to 0.1" (30%) to 0.3" (10%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 1000 AM SAT Trace (100%) to 0.1" (45%) to 0.3" (30%) ISSUED Douglas Current TO 1000 AM SAT Trace (60%) to 0.1" (30%) to 0.3" (10%) ISSUED Jefferson Current TO 1000 AM SAT Trace (80%) to 0.1" (50%) to 0.3" (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

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Time: 607 PM Fri July 30, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S HAVE TRANSITIONED TO MESSAGE 2'S AND WILL REMAIN VALID UNTIL 9PM SATURDAY - Message 1's have transitioned to Message 2's at 6pm to coincide with the NWS Flash Flood Watch. Message 2's/NWS Flash Flood Watch will remain valid until 9:00pm Saturday. - Strong, slow moving thunderstorms have developed over the District this afternoon and are expected to persist well into the evening. Moisture levels are expected to be higher than at any point this season and storms that develop today and tomorrow will be very capable of producing heavy rainfall that will lead to excessive runoff and possibly flash flooding. - The greatest threat for heavy rain from thunderstorms will be through about 10pm or midnight then rain showers may be capable of producing up to 1"/hr or higher rainfall rates overnight absent of any thunder. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.2-0.6" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm will have the potential to produce up to 3.5" in 45-60 minutes. Storms that persist beyond 60 minutes may produce locally higher amounts. COUNTY MESSAGE VALID TIMES PRIME TIME Denver County 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Adams County 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Douglas County 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Lakewood 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Broomfield County 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Jefferson County 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Boulder County 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Wheat Ridge 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Arvada 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY the City of Aurora 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY DIA 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY Arapahoe County 1 Current TO 900 PM SATURDAY Current TO 900 PM SATURDAY County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Arapahoe Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Boulder Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Broomfield Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Denver Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Douglas Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Jefferson Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Douglas Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) ISSUED Jefferson Current TO 1159 PM FRI 0.2" (100%) to 0.6" (85%) to 1.8" (65%) 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

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Time: 452 PM Fri July 30, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR THE ENTIRE DISTRICT/MESSAGE 2'S BECOME VALID AT 6PM - Message 1's have been issued for the entire District and will be valid until 6:00pm then the Message 1's will be upgraded to Message 2's to coincide with the NWS Flash Flood Watch. - A cold front is on the approach and is already producing strong thunderstorms over northern Colorado. As the front moves southward thunderstorms are expected to develop behind it becoming strong to severe with the potential to produce extended periods of heavy rainfall that may lead to excessive runoff and possibly flash flooding. - Moisture levels are expected to be higher than at any point this season later today and tomorrow and will result in efficient rainfall producing storms. The greatest threat for heavy rain from thunderstorms will be through about midnight then rain showers may be capable of producing up to 1"/hr or higher rainfall rates overnight. STORM RAINFALL POTENTIAL AND DURATION: Weak thunderstorms will produce 0.2-0.6" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 0.6-1.8" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A strong thunderstorm will have the potential to produce up to 3.5" in 45-60 minutes. Storms that persist beyond 60 minutes may produce locally higher amounts. COUNTY MESSAGE VALID TIMES PRIME TIME Broomfield County 1 Current TO 600 PM 500 PM TO 600 PM Jefferson County 1 Current TO 600 PM 500 PM TO 600 PM Boulder County 1 Current TO 600 PM 500 PM TO 600 PM Wheat Ridge 1 Current TO 600 PM 500 PM TO 600 PM Arvada 1 Current TO 600 PM 500 PM TO 600 PM the City of Aurora 1 Current TO 600 PM 500 PM TO 600 PM Arapahoe County 1 Current TO 600 PM 500 PM TO 600 PM DIA 1 Current TO 600 PM 500 PM TO 600 PM Denver County 1 Current TO 600 PM 500 PM TO 600 PM Adams County 1 Current TO 600 PM 500 PM TO 600 PM Douglas County 1 Current TO 600 PM 500 PM TO 600 PM Lakewood 1 Current TO 600 PM 500 PM TO 600 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Arapahoe 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Boulder 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Broomfield 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Denver 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Douglas 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Jefferson 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Foothills above 6500ft Â Â Â Boulder 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Douglas 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) ISSUED Jefferson 500 PM TO 1159 PM 0.2" (100%) to 0.6" (75%) to 1.8" (50%) 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

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Time: 851 AM Fri July 30, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- HOT AGAIN TODAY WITH A CHANCE FOR AFTERNOON/EVENING/OVERNIGHT RAIN SHOWERS/ISOLATED THUNDERSTORMS - The final day of 90 degree temperatures as the pattern shifts this afternoon and into this weekend resulting in good chances for off and on rain through Sunday. Highs today will reach the low to mid 90's on the plains with mid to upper 80's along the foothills. An uptick in mid to upper-level moisture is expected this afternoon as a disturbance moves into the region bringing a good chance for scattered rain showers/isolated thunderstorms this afternoon, evening with a continued chance for some overnight rain showers into Saturday morning. - Rain showers and thunderstorms will initiate along the higher terrain this afternoon with the best chance for storms in the District between 3-5pm. Rain showers/thunderstorms chances pick up into the early evening with a continued chance for rain/thunderstorms until 10pm with generally just rain showers after 10pm and through the overnight. Storm motions will be relatively slow from W to E between 3-8mph this afternoon with the potential for stationary storms that form along outflow boundaries which will increase the threat for heavy rainfall this afternoon and evening. - The heavy rainfall threat diminishes this evening and through the overnight, however an isolated brief heavy rain showers or thunderstorm cannot be completely ruled out at this time. Overnight lows will drop into the low to mid 60's with mostly cloudy skies along with the chance for lingering rain showers through daybreak. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers to moderate thunderstorms will produce 0.10-0.40" in 10-30 minutes. 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 2.4" in 60 minutes or less. A LOOK AHEAD: An active weather pattern is expected through the weekend as temperatures remain in the upper 70's to low 80's both Saturday and Sunday. The largest increase in available moisture will be on Saturday along with the highest threat for heavy rainfall. However, with cloudy skies and cooler high temperatures, there will be a chance stronger storms are unable to develop resulting in a better chance for widespread light to moderate rain showers rather than moderate to strong thunderstorms. This pattern continues Sunday with off an on rain showers/isolated thunderstorm chances throughout the day. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Arapahoe 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Boulder 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Broomfield 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Denver 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Douglas 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Jefferson 300 PM TO 1000 PM 0.1" (60%) to 0.4" (30%) to 1.2" (15%) MOD Foothills above 6500ft Â Â Â Boulder 300 PM TO 1000 PM 0.1" (80%) to 0.4" (40%) to 1.2" (20%) HIGH Douglas 300 PM TO 1000 PM 0.1" (80%) to 0.4" (40%) to 1.2" (20%) HIGH Jefferson 300 PM TO 1000 PM 0.1" (80%) to 0.4" (40%) to 1.2" (20%) 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

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Time: 953 PM Thu July 29, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE - Message 1's will be allowed to expire at 10pm. A relatively warmer layer of air aloft held strong keeping any meaningful thunderstorm development at bay over NW portions of the District this evening. Now that temperatures are cooling off the threat for any thunderstorm activity has ended for the day. - Monsoon moisture will increase over the District on Friday and continue to impact NE Colorado Saturday and Sunday as a cold front moves through giving us all a nice reprieve from the heat. - Heavy rainfall chances increase significantly on Friday and are expected to peak Sat/Sun, likely lowering into early next week. With the way this monsoon season has been playing out the next few days will feature a high likelihood of flooding in or around the District. Be prepared! STORM RAINFALL POTENTIAL AND DURATION: No meaningful precipitation expected for the remainder of the overnight period. COUNTY MESSAGE VALID TIMES PRIME TIME Broomfield County 1 Current TO 1000 PM Current TO 1000 PM Jefferson County 1 Current TO 1000 PM Current TO 1000 PM Boulder County 1 Current TO 1000 PM Current TO 1000 PM Adams County 1 Current TO 1000 PM Current TO 1000 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

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Time: 832 PM Thu July 29, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S CONITINUE VALID UNTIL 10PM FOR PORTIONS OF THE DISTRICT - Message 1's will continue valid over NW portions of the District until 10pm although the threat for heavy rainfall is diminishing. - A warm layer of air aloft has kept any moderate to strong storm development at bay despite moisture levels rising significantly from this morning as the 6pm sounding in Denver yielded 1.09" of precipitable water. A surface wind convergence line still exists over NW portions of the District but is is now washing out and reducing storm chances. - There is still a slight chance for a stronger, slow moving thunderstorm to develop but now that temperatures are backing off as the sun sets this threat is much lower than just a couple hours ago. As time passes this evening the threat for heavy rainfall also diminishes likely allowing Messages to expire at 10pm. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" of rain. Moderate to strong thunderstorms will have the potential to produce 0.2-0.6" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A stationary strong thunderstorm will have the potential to produce up to 1.2" in 30-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Adams County 1 Current TO 1000 PM Current TO 900 PM Broomfield County 1 Current TO 1000 PM Current TO 900 PM Jefferson County 1 Current TO 1000 PM Current TO 900 PM Boulder County 1 Current 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 THU Trace (50%) to 0.2" (20%) to 0.6" (10%) ISSUED Arapahoe Current TO 1000 PM THU Trace (25%) to 0.2" (10%) to 0.6" (5%) LOW Boulder Current TO 1000 PM THU Trace (60%) to 0.2" (30%) to 0.6" (10%) ISSUED Broomfield Current TO 1000 PM THU Trace (50%) to 0.2" (20%) to 0.6" (10%) ISSUED Denver Current TO 1000 PM THU Trace (25%) to 0.2" (10%) to 0.6" (5%) LOW Douglas Current TO 1000 PM THU Trace (25%) to 0.2" (10%) to 0.6" (5%) LOW Jefferson Current TO 1000 PM THU Trace (50%) to 0.2" (20%) to 0.6" (10%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 1000 PM THU Trace (90%) to 0.2" (60%) to 0.6" (15%) ISSUED Douglas Current TO 1000 PM THU Trace (25%) to 0.2" (10%) to 0.6" (5%) LOW Jefferson Current TO 1000 PM THU Trace (50%) to 0.2" (20%) to 0.6" (10%) 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

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Time: 702 PM Thu July 29, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S ISSUED FOR PORTIONS OF THE DISTRICT - Message 1's have been issued for NW portions of the District as a surface wind convergence boundary is in place and weak storms are beginning to develop over Boulder and Broomfield Counties. - A warm layer of air aloft results in uncertainty if the current storms can maintain or strengthen but with ample surface moisture in place if a stronger storm is able to develop it will contain heavy rainfall. Best chances for storms are near the surface wind convergence over NW portions of the District but these storms may produce their own outflow boundaries and produce additional storms which may become strong may lead to Message 1's being issued for the remainder of the District as the evening wears on. - Thunderstorms will be slow moving due to weak steering winds aloft. Best chances for thunderstorms will be through 10pm this evening. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.3" of rain. Moderate to strong thunderstorms will have the potential to produce 0.4-1.2" of heavy rain in 10-30 minutes. WORST CASE SCENARIO: A stationary strong thunderstorm will have the potential to produce up to 2.5" in 45-75 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Adams County 1 Current TO 1000 PM Current TO 900 PM Broomfield County 1 Current TO 1000 PM Current TO 900 PM Jefferson County 1 Current TO 1000 PM Current TO 900 PM Boulder County 1 Current 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 THU 0.1" (60%) to 0.4" (25%) to 1.2" (10%) ISSUED Arapahoe Current TO 1000 PM THU 0.1" (40%) to 0.4" (20%) to 1.2" (5%) MOD Boulder Current TO 1000 PM THU 0.1" (80%) to 0.4" (50%) to 1.2" (25%) ISSUED Broomfield Current TO 1000 PM THU 0.1" (80%) to 0.4" (50%) to 1.2" (25%) ISSUED Denver Current TO 1000 PM THU 0.1" (40%) to 0.4" (20%) to 1.2" (5%) MOD Douglas Current TO 1000 PM THU 0.1" (40%) to 0.4" (20%) to 1.2" (5%) LOW Jefferson Current TO 1000 PM THU 0.1" (60%) to 0.4" (25%) to 1.2" (10%) ISSUED Foothills above 6500ft Â Â Â Boulder 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" (40%) to 0.4" (20%) to 1.2" (5%) LOW Jefferson Current TO 1000 PM THU 0.1" (75%) to 0.4" (50%) to 1.2" (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

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Time: 846 AM Thu July 29, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ANOTHER HOT DAY WITH A SLIGHT CHANCE FOR SCATTERED HIGH-BASED AFTERNOON RAIN SHOWERS/ISOLATED THUNDERSTORMS - After record breaking heat yesterday, very little change in the forecast today with highs expected in the low to mid 90s this afternoon. Although minimal, a slightly better chance today for scattered high-based afternoon/early evening rain showers/isolated thunderstorms. However, Most areas will likely remain dry today, with any storm development favoring areas along the Palmer Divide and eastward out on the plains. - Best chance for storm development will begin between 2-4pm with a chance for rain showers/isolated thunderstorms through 7-9pm with a slight chance for continued rain showers favoring northern portions of the District at this time. Most rain showers/isolated thunderstorms will be high-based if they do develop, resulting in a better chance for gusty winds and the occasional lightning strike, however, current dewpoints are in the low to mid 50's for eastern portions of the District. If these dewpoints struggle to mix out during the day, a threat will remain for isolated moderate to heavy rainfall if a stronger storm is able to develop, especially off an outflow boundary resulting in erratic or stationary storm movement. - Any threat for stronger rain showers/isolated thunderstorms diminishes quickly after sunset with generally mild conditions overnight and into Friday as lows are expected to reach the upper 60's to low 70's for the plains with low to mid 60's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical high-based rain showers/isolated thunderstorms will produce a TR-0.10" in 10-30 minutes. A moderate rain shower/isolated thunderstorm will produce 0.1-0.3" in 10-30 minutes. WORST CASE SCENARIO: A stronger thunderstorm that forms along an outflow boundary will have the potential to produce 1.2" in less than 60 minutes. A LOOK AHEAD: Monsoonal moisture returns Friday afternoon with a good chance for rain showers/thunderstorms over the District during the afternoon/evening and through the overnight into Saturday. As this disturbance slowly churns, rain and thunderstorm chances will continue over the region through the entire weekend before this disturbance starts to move eastward. With adequate moisture in place at the surface and in the mid to upper-level, the threat for heavy rainfall will likely persist through the weekend before the region starts to dry out on Monday of next week. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) LOW Arapahoe 200 PM TO 900 PM Trace (35%) to 0.2" (20%) to 0.3" (15%) LOW Boulder 200 PM TO 900 PM Trace (30%) to 0.2" (10%) to 0.3" (5%) NONE Broomfield 200 PM TO 900 PM Trace (30%) to 0.2" (10%) to 0.3" (5%) NONE Denver 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) LOW Douglas 200 PM TO 900 PM Trace (40%) to 0.2" (20%) to 0.3" (15%) LOW Jefferson 200 PM TO 900 PM Trace (30%) to 0.2" (10%) to 0.3" (5%) NONE Foothills above 6500ft Â Â Â Boulder 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) NONE Douglas 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) NONE Jefferson 200 PM TO 900 PM Trace (30%) to 0.2" (15%) to 0.3" (10%) NONE 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: 825 AM Wed July 28, 2021 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- DRY, HAZY WITH RECORD BREAKING HEAT - High-pressure continues to dominate over the region leading to another hot, dry and hazy day. Afternoon highs are expected in the mid to upper 90's across the plains. Current record temperature at DIA for today is 98 degrees set ALL the way back in 1876. A very good chance we will reach or break that record at DIA this afternoon. - A warm layer of air aloft will continue to eliminate any chance for rain shower or thunderstorm activity over the District today with dry conditions expected area wide. There will be a few fair weather clouds that develop this afternoon over the mountains and along the Palmer divide with hot and mild conditions through the evening. - Overnight lows will remain in the upper 60's to low 70's for the plains with low to mid 60's along the foothills. STORM RAINFALL POTENTIAL AND DURATION: No precipitation expected today or tonight. A LOOK AHEAD: Similar conditions Thursday as high temperatures remain in the mid to upper 90's along the plains with upper 80's to low 90's along the foothills. Hazy and dry Thursday with continued dry conditions. A bit cooler Friday with highs in the upper 80's to low 90's. A weak disturbance moves in Friday afternoon bringing a slight chance for scattered rain shower's/isolated thunderstorms with minimal, if any, chance for heavy rainfall. A stronger disturbance moves into the region Saturday effectively dropping high temperatures into the 80's with a good chance for rain showers/isolated thunderstorms. Storm intensities will hinge on daytime heating, although with adequate moisture in place, a moderate chance for heavy rainfall is expected 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]

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hpo-ims July 2021