August 2023 - hpo-ims - Udfcd-Lists.Org

by f2p2＠udfcd.org

Time: 517 PM Sat August 5, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- SHOWERS CURRENTLY OVER PORTIONS OF THE DISRTICT WITH AN APPROACHING GUST FRONT COULD PRODUCE RAPID STORM DEVELOPMENT OVER THE FEW HOURS The Denver metro was able to miss stronger storms so far today and this could continue, however, a gust front approaches from the east with an uptick in surface moisture. This uptick combined with good upper-level support in and and around the area will bring a chance for rapid storm development leading to localized heavy rainfall. Stronger storms will favor eastern portions of the District at this time. Showers and weak thunderstorms that have developed are currently moving fairly quick, between 25-30mph, although strong storms that form along outflow boundaries could stall out and produce a quick 0.5-1.0” in 10-30 minutes. The best chance for storms will be between now and 9pm, with a few off and on showers through the late evening. Note: if stronger storms are able to develop, there is potential for large hail 1+”, gusty winds 60mph, and frequent cloud-to-ground. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/thunderstorms will produce a 0.05-0.25” total in 10 to 30 minutes. A moderate thunderstorm will produce 0.25” to 0.50” total in 10 to 30 minutes. A strong thunderstorm will produce 0.50” to 1.00” total in 10 to 30 minutes. WORST CASE SCENARIO: An anchored strong thunderstorm or training of thunderstorm cells has the potential to produce up to 1.75” in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 900 PM Current TO 800 PM Jefferson County 1 Current TO 900 PM Current TO 800 PM Broomfield County 1 Current TO 900 PM Current TO 800 PM Douglas County 1 Current TO 900 PM Current TO 800 PM Adams County 1 Current TO 900 PM Current TO 800 PM Denver County 1 Current TO 900 PM Current TO 800 PM DIA 1 Current TO 900 PM Current TO 800 PM Arapahoe County 1 Current TO 900 PM Current TO 800 PM the City of Aurora 1 Current TO 900 PM Current TO 800 PM Arvada 1 Current TO 900 PM Current TO 800 PM Wheat Ridge 1 Current TO 900 PM Current TO 800 PM Lakewood 1 Current TO 900 PM Current TO 800 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Arapahoe Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Boulder Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Broomfield Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Denver Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Douglas Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Jefferson Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Foothills above 6500ft Boulder Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Douglas Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED Jefferson Current TO 900 PM SAT 0.25" (50%) to 0.5" (25%) to 1" (15%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 858 AM Sat August 5, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- A CHANCE FOR SHOWERS/ISOLATED THUNDERSTORMS THIS AFTERNOON AND INTO THIS EVENING Mild and dry currently, a change is in the air today as a cold front is poised to move through the region this afternoon. This cold front should have no issues getting a few showers and isolated thunderstorms going this afternoon and possibly into the evening hours. Slightly less moisture at the surface currently should increase behind the cold front bringing dew points back into the upper 50’s to around 60. This will result in a MODERATE chance for Message 1’s as the potential for a quick 0.25-0.75” in 10-30 minutes will be possible today. Initial storm development will be along the higher terrain by midday with showers/isolated thunderstorms moving into the District between 2-8pm. Storm motions will continue to be brisk from W to E between 15-25mph, effectively limiting any point rainfall amounts. However, a stronger storm will have the potential to produce outflow boundaries which additional storm develop could stall out along, bringing the best chance for moderate to brief heavy rainfall, favoring eastern portions of the District at this time. Skies will stay partly through the overnight with lows in the mid to upper 50’s on the plains with low 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a 0.05-0.25” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.25-0.75” total in 10-30 minutes. WORST CASE SCENARIO: A stronger, stalled out thunderstorm formed along an outflow boundary is able to develop, will have the potential to produce up to 1.25” total, in under 60 minutes. A LOOK AHEAD: Cooler temperatures behind this cold front will dictate the strength of storms tomorrow as highs are expected to stay in the 70s. An uptick in overall moisture will likely bring a chance for moderate to brief heavy rainfall throughout most of the afternoon with chances picking up into the evening. Storm chances remain Monday, with another decent chance for afternoon/eve showers/isolated thunderstorms. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Arapahoe 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Boulder 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Broomfield 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Denver 200 PM TO 900 PM 0.05" (65%) to 0.25" (35%) to 0.75" (20%) MOD Douglas 200 PM TO 900 PM 0.05" (75%) to 0.25" (50%) to 0.75" (25%) MOD Jefferson 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Foothills above 6500ft Douglas 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Jefferson 200 PM TO 900 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Boulder 100 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 900 AM Fri August 4, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- A SLIGHT CHANCE FOR SHOWERS/ISOLATED THUNDERSTORMS THIS AFTERNOON AND EARLY EVENING, MAINLY NORTH AND EAST OF THE DISTRICT. Not much change to the overall pattern once again today as westerly flow aloft continues to dominate over the region. Slightly less moisture aloft should decrease storm chances today, however, dew points have remained in the upper 50’s to around 60 and will likely only decrease slightly through the rest of the day. This will result in a LOW chance for Message 1’s as the potential for a quick 0.5” in 10-30 minutes remains today. Any storm development should stay to the north and move well east of the District. There will be a slight chance storms are able to develop in the District, especially if a gust front approaches from storms on the peripheral of the District. The best chance for storm development within the District will be between 2-8pm. Storm motions will be brisk from W to E between 15-25mph, effectively limiting any point rainfall amounts for storms that do develop. Skies will clear this evening, at or before sunset, with overnight lows in the upper 50’s to low 60’s on the plains with low to mid 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a 0.05-0.30” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.30-0.60” total in 10-30 minutes. WORST CASE SCENARIO: A stronger, stalled out thunderstorm formed along an outflow boundary is able to develop, will have the potential to produce up to 1.20” total, in under 60 minutes. A LOOK AHEAD: A slightly better chance for storms Saturday afternoon and evening, with more widespread rainfall likely across the I-25 corridor. No doubt dew points will remain elevated, resulting in a chance for isolated heavy rainfall which will keep at least a LOW if not MOD chance for Message 1’s to be issued. Cooler temperatures Sunday behind a cold front will dictate the strength of storms, although there will be a good chance once again for widespread showers and possibly a few thunderstorms Sunday afternoon and evening. An uptick in overall moisture will likely bring a chance for moderate to heavy rainfall throughout most of the day Sunday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 800 PM FRI 0.05" (40%) to 0.25" (25%) to 0.6" (10%) LOW Arapahoe Current TO 800 PM FRI 0.05" (40%) to 0.25" (25%) to 0.6" (10%) LOW Boulder Current TO 800 PM FRI 0.05" (30%) to 0.25" (20%) to 0.6" (10%) LOW Broomfield Current TO 800 PM FRI 0.05" (30%) to 0.25" (20%) to 0.6" (10%) LOW Denver Current TO 800 PM FRI 0.05" (30%) to 0.25" (20%) to 0.6" (10%) LOW Douglas Current TO 800 PM FRI 0.05" (30%) to 0.25" (20%) to 0.6" (10%) LOW Jefferson Current TO 800 PM FRI 0.05" (30%) to 0.25" (20%) to 0.6" (10%) LOW Foothills above 6500ft Boulder Current TO 800 PM FRI 0.05" (40%) to 0.25" (25%) to 0.6" (10%) LOW Douglas Current TO 800 PM FRI 0.05" (40%) to 0.25" (25%) to 0.6" (10%) LOW Jefferson Current TO 800 PM FRI 0.05" (40%) to 0.25" (25%) to 0.6" (10%) 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]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 650 PM Thu August 3, 2023 Forecaster: Laura Smith ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S WILL BE ALLOWED TO EXPIRE AT 7:00 PM Message 1’s will be allowed to expire at 7:00pm as the threat for heavy rainfall has come to an end. A few strong to severe storms have impacted the region this afternoon and early evening and are currently moving out of the District and onto the eastern plains, with the exception of showers in Douglas County along the southern edge of the District. Skies have cleared behind these storms and will continue through the rest of the evening. A few lingering showers are possible in Douglas County and will remain mostly south of the District over the next few hours. Minimal, if any, precipitation is expected through the overnight as low temperatures drop into the upper 50s to low 60s on the plains. STORM RAINFALL POTENTIAL AND DURATION: No additional rainfall is expected through the evening and overnight. WORST CASE SCENARIO: A stray shower moves north into the District from Douglas County and produces a trace to 0.25" in 10-30 minutes total. COUNTY MESSAGE VALID TIMES PRIME TIME the City of Aurora 1 Current TO 700 PM Current TO 700 PM Arapahoe County 1 Current TO 700 PM Current TO 700 PM DIA 1 Current TO 700 PM Current TO 700 PM Denver County 1 Current TO 700 PM Current TO 700 PM Adams County 1 Current TO 700 PM Current TO 700 PM Douglas County 1 Current TO 700 PM Current TO 700 PM Broomfield County 1 Current TO 700 PM Current TO 700 PM Jefferson County 1 Current TO 700 PM Current TO 700 PM Boulder County 1 Current TO 700 PM Current TO 700 PM Arvada 1 Current TO 700 PM Current TO 700 PM Wheat Ridge 1 Current TO 700 PM Current TO 700 PM Lakewood 1 Current TO 700 PM Current TO 700 PM MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 140 PM Thu August 3, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S HAVE BEEN ISSUED EFFECTIVE UNTIL 7:00 PM Message 1’s have been issued effective until 7pm as there is a threat of heavy rainfall. Storms have initiated along western portions of the District today and will be moving eastward through the afternoon and early evening. Dew points at this time are well in the 50’s with around 60 by DIA. Strong upper-level support sits just east of the District, out on the eastern plains where strong to severe storms are likely. A chance for moderate to brief heavy rainfall within the District this afternoon and early evening. The best chance will be from now until 6pm with storms quickly moving east this evening and out of the District. A slight chance a storm could become severe inside the District, mainly for gusty winds and hail up to 1”. Storm motions will generally be from west to east between 15-25mph with some erratic storm movements possible along gust fronts. These storms will have the best chance of producing longer lasting heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/thunderstorms will produce a 0.05-0.25” total in 10 to 30 minutes. A moderate thunderstorm will produce 0.25” to 0.50” total in 10 to 30 minutes. A strong thunderstorm will produce 0.50” to 1.00” total in 10 to 30 minutes. WORST CASE SCENARIO: An anchored strong thunderstorm or training of thunderstorm cells has the potential to produce up to 1.5” in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 700 PM 200 PM TO 600 PM Jefferson County 1 Current TO 700 PM 200 PM TO 600 PM Broomfield County 1 Current TO 700 PM 200 PM TO 600 PM Douglas County 1 Current TO 700 PM 200 PM TO 600 PM Adams County 1 Current TO 700 PM 200 PM TO 600 PM Denver County 1 Current TO 700 PM 200 PM TO 600 PM DIA 1 Current TO 700 PM 200 PM TO 600 PM Arapahoe County 1 Current TO 700 PM 200 PM TO 600 PM the City of Aurora 1 Current TO 700 PM 200 PM TO 600 PM Arvada 1 Current TO 700 PM 200 PM TO 600 PM Wheat Ridge 1 Current TO 700 PM 200 PM TO 600 PM Lakewood 1 Current TO 700 PM 200 PM TO 600 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 700 PM THU 0.25" (75%) to 0.5" (40%) to 1" (20%) ISSUED Arapahoe Current TO 700 PM THU 0.25" (75%) to 0.5" (40%) to 1" (20%) ISSUED Boulder Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED Broomfield Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED Denver Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED Douglas Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED Jefferson Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED Foothills above 6500ft Boulder Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED Douglas Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED Jefferson Current TO 700 PM THU 0.25" (60%) to 0.5" (30%) to 1" (15%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 852 AM Thu August 3, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- A CHANCE FOR AFTERNOON/EARLY EVENING SHOWERS/THUNDERSTORMS WITH BRIEF HEAVY RAINFALL Very minimal change to the overall pattern again today as westerly flow aloft continues to dominate over the region. Dew points have remained in the upper 50’s to around 60 and will likely only decrease slightly through the rest of the day. The best chance for storm development within the District will be between 2-8pm. Storm motions will once again be W to E between 10-20mph, effectively limiting any point rainfall amounts. However, a few storms could produce gust fronts, with additional storms forming along these gust fronts within the District. These storms will have the highest potential to produce impactful heavy rainfall as they will likely stall out over an area for an extended period. Currently only one round of showers and thunderstorms will move across the District through the afternoon and early evening, with the strongest storms likely during the afternoon with storms decreasing in intensity as the evening progresses over the District. A better chance for stronger storm development just east of the District and onto the eastern plains where severe weather will be likely through the late evening hours. Skies will clear this evening after sunset with overnight lows in the upper 50’s to low 60’s on the plains with low to mid 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a 0.05-0.25” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.25-0.75” total in 10-30 minutes. Strong thunderstorms will produce 0.75-1.25” total in 10-30 minutes. WORST CASE SCENARIO: A stronger, stalled out thunderstorm is able to develop and will have the potential to produce up to 2.00” total, in 45-60 minutes. A LOOK AHEAD: An overall decrease in moisture in the area tomorrow will likely limit the heavy rainfall threat significantly. Storm chances will be similar to today, between 2-8pm with west to east storm movements between 15-25mph which will help limit point rainfall amounts. Storms will generally be weaker than previous days, at least over the District both Friday and Saturday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 200 PM TO 800 PM 0.05" (70%) to 0.25" (40%) to 0.75" (20%) MOD Arapahoe 200 PM TO 800 PM 0.05" (70%) to 0.25" (40%) to 0.75" (20%) MOD Boulder 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Broomfield 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Denver 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Douglas 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Jefferson 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Foothills above 6500ft Boulder 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Douglas 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD Jefferson 200 PM TO 800 PM 0.05" (60%) to 0.25" (30%) to 0.75" (15%) MOD MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 1024 PM Wed August 2, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S WILL BE ALLOWED TO EXPIRE AT 11:00 PM Message 1’s will be allowed to expire at 11:00pm as the threat for heavy rainfall has come to an end. A strong late night round of showers/thunderstorms has impacted the District. A few lingering showers/isolated thunderstorms are still in the north, and eastern portions of the District at this time and will continue to move eastward through the overnight. A chance for off and on overnight showers and possibly a rumble of thunder or two through daybreak tomorrow. A slight chance showers and isolated thunderstorms tomorrow morning, mainly out of the eastern plains. Another chance for showers/thunderstorms tomorrow afternoon and early evening. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/thunderstorms will produce a TR-0.20” total in 10 to 30 minutes. A moderate thunderstorm will produce 0.20” to 0.40” total in 10 to 30 minutes. WORST CASE SCENARIO: A strong thunderstorm, or training of moderate thunderstorms will have the potential to produce up to 0.80” total in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 Current TO 1100 PM Current TO 1030 PM Wheat Ridge 1 Current TO 1100 PM Current TO 1030 PM Arvada 1 Current TO 1100 PM Current TO 1030 PM the City of Aurora 1 Current TO 1100 PM Current TO 1030 PM DIA 1 Current TO 1100 PM Current TO 1030 PM Arapahoe County 1 Current TO 1100 PM Current TO 1030 PM Denver County 1 Current TO 1100 PM Current TO 1030 PM Adams County 1 Current TO 1100 PM Current TO 1030 PM Douglas County 1 Current TO 1100 PM Current TO 1030 PM Broomfield County 1 Current TO 1100 PM Current TO 1030 PM Jefferson County 1 Current TO 1100 PM Current TO 1030 PM Boulder County 1 Current TO 1100 PM Current TO 1030 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Arapahoe Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Boulder Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Broomfield Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Denver Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Douglas Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Jefferson Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Foothills above 6500ft Boulder Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Douglas Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) NONE Jefferson Current TO 600 AM THU Trace (50%) to 0.2" (25%) to 0.4" (10%) 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]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 838 PM Wed August 2, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S HAVE BEEN EXTENDED UNTIL 11:00 PM Message 1’s have been extended as the threat of heavy rainfall remains over the District. A line of storms is currently moving into the District from the southwest. A gust front from the northeast is also moving into the District and these will converge over the District over the next few hours. Behind this gust front, dew points are very elevated, around 60 degrees, resulting in a good chance for efficient rainfall producing storms. Currently storm motions are fairly brisk out of the southwest between 15-25mph, although storm movements may become erratic once the gust front from the northeast moves in. The strongest storms are currently in Douglas County and are expected to move northeastward and into Denver and Arapahoe Counties. Additional storms could initiate in north and northwestern portions of the District, however the best chance for heavy rainfall will likely be for south and southeastern portions of the District through the rest of the evening. Stronger storms should diminish by 10pm with light to moderate storms through 11pm. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/thunderstorms will produce a 0.05-0.25” total in 10 to 30 minutes. A moderate thunderstorm will produce 0.25” to 0.75” total in 10 to 30 minutes. A strong thunderstorm will produce 0.75” to 1.25” total in 10 to 30 minutes. WORST CASE SCENARIO: An anchored strong thunderstorm or training of thunderstorm cells has the potential to produce up to 2.5” in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 Current TO 1100 PM Current TO 1030 PM Wheat Ridge 1 Current TO 1100 PM Current TO 1030 PM Arvada 1 Current TO 1100 PM Current TO 1030 PM the City of Aurora 1 Current TO 1100 PM Current TO 1030 PM Arapahoe County 1 Current TO 1100 PM Current TO 1030 PM DIA 1 Current TO 1100 PM Current TO 1030 PM Denver County 1 Current TO 1100 PM Current TO 1030 PM Adams County 1 Current TO 1100 PM Current TO 1030 PM Douglas County 1 Current TO 1100 PM Current TO 1030 PM Broomfield County 1 Current TO 1100 PM Current TO 1030 PM Jefferson County 1 Current TO 1100 PM Current TO 1030 PM Boulder County 1 Current TO 1100 PM Current TO 1030 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 1100 PM WED 0.25" (75%) to 0.75" (35%) to 1.25" (15%) ISSUED Arapahoe Current TO 1100 PM WED 0.25" (80%) to 0.75" (40%) to 1.25" (20%) ISSUED Boulder Current TO 1100 PM WED 0.25" (60%) to 0.75" (30%) to 1.25" (15%) ISSUED Broomfield Current TO 1100 PM WED 0.25" (60%) to 0.75" (30%) to 1.25" (15%) ISSUED Denver Current TO 1100 PM WED 0.25" (80%) to 0.75" (40%) to 1.25" (20%) ISSUED Douglas Current TO 1100 PM WED 0.25" (80%) to 0.75" (40%) to 1.25" (20%) ISSUED Jefferson Current TO 1100 PM WED 0.25" (60%) to 0.75" (30%) to 1.25" (15%) ISSUED Foothills above 6500ft Boulder Current TO 1100 PM WED 0.25" (50%) to 0.75" (25%) to 1.25" (10%) ISSUED Douglas Current TO 1100 PM WED 0.25" (50%) to 0.75" (25%) to 1.25" (10%) ISSUED Jefferson Current TO 1100 PM WED 0.25" (50%) to 0.75" (25%) to 1.25" (10%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 542 PM Wed August 2, 2023 Forecaster: Laura Smith ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S WILL CONTINUE VALID UNTIL 9:00 PM Message 1’s will continue to be valid as the threat of heavy rainfall continues. Thunderstorms began forming along a boundary near the southern portions of the District earlier this afternoon, but dissipated before producing significant rainfall. Dewpoints remain elevated in the low to mid 50s with temperatures climbing into the mid 80s. Currently, an outflow boundary is slowly approaching the District from the northeast, and has the potential to provide enough low level forcing to initiate thunderstorms into the evening. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/thunderstorms will produce a trace to 0.25” total in 10 to 30 minutes. A moderate thunderstorm will produce 0.25” to 0.50” total in 10 to 30 minutes. A strong thunderstorm will produce 0.50” to 0.75” total in 10 to 30 minutes. WORST CASE SCENARIO: An anchored strong thunderstorm or training of thunderstorm cells has the potential to produce up to 1.50” in under 60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 Current TO 900 PM Current TO 830 PM Wheat Ridge 1 Current TO 900 PM Current TO 830 PM Arvada 1 Current TO 900 PM Current TO 830 PM the City of Aurora 1 Current TO 900 PM Current TO 830 PM Arapahoe County 1 Current TO 900 PM Current TO 830 PM DIA 1 Current TO 900 PM Current TO 830 PM Denver County 1 Current TO 900 PM Current TO 830 PM Adams County 1 Current TO 900 PM Current TO 830 PM Douglas County 1 Current TO 900 PM Current TO 830 PM Broomfield County 1 Current TO 900 PM Current TO 830 PM Jefferson County 1 Current TO 900 PM Current TO 830 PM Boulder County 1 Current TO 900 PM Current TO 830 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Arapahoe Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Boulder Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Broomfield Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Denver Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Douglas Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Jefferson Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Foothills above 6500ft Boulder Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Douglas Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED Jefferson Current TO 900 PM WED 0.25" (50%) to 0.5" (25%) to 0.75" (10%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 3 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 221 PM Wed August 2, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- ANOTHER GOOD CHANCE FOR SHOWERS/THUNDERSTORMS ACROSS THE DISTRICT THIS AFTERNOON AND EVENING. Message 1’s have been issued for the entire District effective until 9pm. A few isolated storms have formed along the higher terrain west of the District and will move through the District over the next several hours before storm chances taper off after sundown. A couple of rounds of storms will be possible through the evening with a slight chance for a few off and on showers through the overnight. Storms will be hit or miss today, leading to some areas likely staying dry. A boundary has been set up along the eastern portion of the District which will be a focal point for stronger storm development heading into the late afternoon/early evening. Storm motions will typically be from west to east between 10-20mph, which should help limit point rainfall amounts. However, additional storms that form along outflow boundaries have the potential to stall out and bring moderate to heavy rainfall for an extended period of time. These storms will likely have the best chance of heavy rainfall leading to LOW IMPACT FLOODING with both threats of a quick 0.5” in 10-15 minutes. The best chance for stronger storms will be from the initial wave of storms, with subsequent waves of showers decreasing with intensity through the evening. STORM RAINFALL POTENTIAL AND DURATION: Typical showers/weak thunderstorms will produce a 0.05-0.25” total, in 10-30 minutes. A moderate to strong shower/thunderstorm will produce 0.25-0.75” total in 10-30 minutes. Strong thunderstorms will produce 0.75-1.50” total in 10-30 minutes. WORST CASE SCENARIO: A stronger, stalled out thunderstorm is able to develop and will have the potential to produce up to 2.50” total, in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Wheat Ridge 1 Current TO 900 PM Current TO 830 PM Lakewood 1 Current TO 900 PM Current TO 830 PM Arvada 1 Current TO 900 PM Current TO 830 PM the City of Aurora 1 Current TO 900 PM Current TO 830 PM Arapahoe County 1 Current TO 900 PM Current TO 830 PM DIA 1 Current TO 900 PM Current TO 830 PM Denver County 1 Current TO 900 PM Current TO 830 PM Adams County 1 Current TO 900 PM Current TO 830 PM Douglas County 1 Current TO 900 PM Current TO 830 PM Broomfield County 1 Current TO 900 PM Current TO 830 PM Jefferson County 1 Current TO 900 PM Current TO 830 PM Boulder County 1 Current TO 900 PM Current TO 830 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Arapahoe Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Boulder Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Broomfield Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Denver Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Douglas Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Jefferson Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Foothills above 6500ft Boulder Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Douglas Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED Jefferson Current TO 900 PM WED 0.25" (50%) to 0.75" (25%) to 1.5" (10%) ISSUED MONITOR NATIONAL WEATHER SERVICE FOR SEVERE WEATHER STATEMENTS. MHFD Flood Prediction Center: 303-458-0789 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

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hpo-ims August 2023