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

by f2p2＠udfcd.org

Time: 853 AM Wed June 30, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SLOW STORM MOTIONS AND AMPLE MOISTURE = INGREDIENTS FOR HEAVY RAINFALL PRODUCING THUNDERSTORMS - Moisture is on the increase today, the only question is whether or not there will be any significant storm coverage within District boundaries... Light upper level winds from the SW at 10mph or less and ample surface moisture with dew points in the upper 40's to lower 50's will result in thunderstorms that develop today having the potential to produce extended periods of moderate and heavy rainfall. - Thunderstorms will first develop over the foothills and Palmer Divide by around noon or shortly after. With light steering winds and a lack of a trigger over the plains the storms are expected to favor the higher terrain. Rain cooled outflow from foothill storms or the development of a surface wind convergence line over the plains will likely be needed to initiate convection within the District itself. Between 2-4pm a gust front from foothill storms or the set-up of a surface wind convergence line may develop or a combination of the two and thunderstorms will become more likely over the plains. - The foothills and Palmer Divide stand the best chance for stronger storms today with a lesser chance over the plains, however the plains storms will be just as capable of producing heavy rain, the overall threat is just lower. Prime time for thunderstorms today is from 2-8pm, beyond 8pm any thunderstorm activity is expected to be weak with conditions trending dry for the overnight period. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.4" in 15-45 minutes. Moderate to strong thunderstorms will have the potential to produce 0.4-1.6" in 15-45 minutes. WORST CASE SCENARIO: A stationary strong thunderstorm may result in up to 2.5" of rain in 60-90 minutes. A LOOK AHEAD: Thunderstorm chances increase all areas of the District on Thursday with scattered to numerous thunderstorms expected during the afternoon and evening. There is a high likelihood of excessive runoff and possibly flash flooding as moisture levels continue to rise and storm motions remain very slow. Not much change on Friday with scattered to numerous thunderstorms with the potential for heavy rainfall. There will likely be a flooding event of some type over the next few days but the severity and location cannot be pinpointed until the events begin to unfold. LOCATION PRIME TIME 45-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 200 PM TO 800 PM 0.1" (65%) to 0.4" (30%) to 1.0" (15%) MOD Arapahoe 200 PM TO 800 PM 0.1" (65%) to 0.4" (30%) to 1.0" (15%) MOD Broomfield 200 PM TO 800 PM 0.1" (65%) to 0.4" (30%) to 1.0" (15%) MOD Denver 200 PM TO 800 PM 0.1" (65%) to 0.4" (30%) to 1.0" (15%) MOD Boulder 100 PM TO 800 PM 0.1" (75%) to 0.4" (50%) to 1.0" (25%) MOD Douglas 100 PM TO 800 PM 0.1" (80%) to 0.4" (60%) to 1.0" (30%) MOD Jefferson 100 PM TO 800 PM 0.1" (75%) to 0.4" (50%) to 1.0" (25%) MOD Foothills above 6500ft Â Â Â Boulder 1200 PM TO 800 PM 0.1" (95%) to 0.4" (75%) to 1.0" (35%) HIGH Douglas 1200 PM TO 800 PM 0.1" (95%) to 0.4" (75%) to 1.0" (35%) HIGH Jefferson 1200 PM TO 800 PM 0.1" (95%) to 0.4" (75%) to 1.0" (35%) 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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 805 PM Tue June 29, 2021 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE AT 9:00 PM - Message 1's will be allowed to expire at 9:00pm as the threat for heavy rainfall across the District has come to an end for the day. - Rain showers have started to dissipate over the District and will continue to do so over the next hour or so with very few light lingering rain showers along the foothills. - Skies will gradually clear through the overnight and into tomorrow morning. Another chance for widely scattered rain showers/thunderstorms tomorrow afternoon with high temperatures reaching the low to mid 80's. STORM RAINFALL POTENTIAL AND DURATION: Typical light rain showers will produce a trace to 0.10" in 10-30 minutes. WORST CASE SCENARIO: A moderate rain showers has the potential to produce 0.10-0.3" in 30-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Wheat Ridge 1 Current TO 900 PM Current TO 900 PM Lakewood 1 Current TO 900 PM Current TO 900 PM Arvada 1 Current TO 900 PM Current TO 900 PM the City of Aurora 1 Current TO 900 PM Current TO 900 PM Arapahoe County 1 Current TO 900 PM Current TO 900 PM DIA 1 Current TO 900 PM Current TO 900 PM Denver County 1 Current TO 900 PM Current TO 900 PM Adams County 1 Current TO 900 PM Current TO 900 PM Douglas County 1 Current TO 900 PM Current TO 900 PM Broomfield County 1 Current TO 900 PM Current TO 900 PM Jefferson County 1 Current TO 900 PM Current TO 900 PM Boulder County 1 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 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (0%) NONE Arapahoe Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (0%) NONE Boulder Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (0%) NONE Broomfield Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (0%) NONE Denver Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (0%) NONE Douglas Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (0%) NONE Jefferson Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (0%) NONE Foothills above 6500ft Â Â Â Boulder Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Douglas Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Jefferson Current TO 1000 PM TUE Trace (20%) to 0.1" (10%) to 0.3" (5%) 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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 405 PM Tue June 29, 2021 Forecaster: Justin Brooks ------------------------- 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 effective until 9pm. - Slow moving to nearly stationary thunderstorms have pushed a rain cooled outflow boundary eastward and onto the plains. Nearly stationary rain showers and isolated thunderstorms have formed around the Chatfield area and will slowly build outward from this area to the north and east with rain showers to isolated thunderstorms possible throughout the District for the rest of this afternoon and evening. - Moderate to strong thunderstorms will be capable of producing heavy rainfall that may lead to excessive runoff. Best chances for thunderstorms will be over the next 4-5hours. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.3-0.9" in 10-30 minutes. WORST CASE SCENARIO: A stationary moderate to strong thunderstorm may result in up to 2.5" of rain in 60-90 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME 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 Broomfield County 1 Current TO 900 PM Current TO 800 PM Jefferson County 1 Current TO 900 PM Current TO 800 PM Boulder County 1 Current TO 900 PM Current TO 800 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 900 PM TUE 0.1" (30%) to 0.3" (20%) to 0.9" (5%) ISSUED Arapahoe Current TO 900 PM TUE 0.1" (40%) to 0.3" (30%) to 0.9" (10%) ISSUED Boulder Current TO 900 PM TUE 0.1" (65%) to 0.3" (40%) to 0.9" (20%) ISSUED Broomfield Current TO 900 PM TUE 0.1" (50%) to 0.3" (40%) to 0.9" (10%) ISSUED Denver Current TO 900 PM TUE 0.1" (50%) to 0.3" (40%) to 0.9" (10%) ISSUED Douglas Current TO 900 PM TUE 0.1" (75%) to 0.3" (50%) to 0.9" (25%) ISSUED Jefferson Current TO 900 PM TUE 0.1" (75%) to 0.3" (50%) to 0.9" (25%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 900 PM TUE 0.1" (75%) to 0.3" (50%) to 0.9" (25%) ISSUED Douglas Current TO 900 PM TUE 0.1" (75%) to 0.3" (50%) to 0.9" (25%) ISSUED Jefferson Current TO 900 PM TUE 0.1" (75%) to 0.3" (50%) to 0.9" (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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 308 PM Tue June 29, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- FOOTHILL THUNDERSTORMS MAY SUPPLY TRIGGER FOR STORMS ON THE PLAINS LATER THIS AFTERNOON/EVENING - Slow moving to nearly stationary thunderstorms over the foothills of Jefferson County may push a rain cooled outflow boundary eastward onto the plains shortly. This rain cooled outflow boundary/gust front may be able to overcome a warm layer of air aloft and generate new storm development over the plains in the coming hours. - Thunderstorms if they develop will be slow moving and capable of producing moderate to heavy rainfall for extended periods of time. There is no indication that storms are imminent but may develop over the coming hours if conditions come together just right. - Best chances for thunderstorm activity continues to be over the foothills through about 8pm this evening. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce 0.3-0.9" in 10-30 minutes. Strong thunderstorms will have the potential to produce 0.5-1.5" in 10-30 minutes. WORST CASE SCENARIO: A stationary moderate to strong thunderstorm may result in up to 2.5" of rain in 60-90 minutes. A LOOK AHEAD: We will tack on a few more degrees to high temperatures on Wednesday and add a little more moisture. With more heat and moisture to work with there will be a better chance for afternoon thunderstorms, some of which may contain heavy rainfall. Thursday and Friday will feature a high likelihood of afternoon and evening thunderstorms with the potential to produce heavy rainfall that may result in excessive runoff and flash flooding. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 400 PM TO 800 PM 0.1" (60%) to 0.3" (30%) to 0.9" (15%) MOD Arapahoe 400 PM TO 800 PM 0.1" (60%) to 0.3" (30%) to 0.9" (15%) MOD Boulder 400 PM TO 800 PM 0.1" (65%) to 0.3" (40%) to 0.9" (20%) MOD Broomfield 400 PM TO 800 PM 0.1" (60%) to 0.3" (30%) to 0.9" (15%) MOD Denver 400 PM TO 800 PM 0.1" (60%) to 0.3" (30%) to 0.9" (15%) MOD Douglas 400 PM TO 800 PM 0.1" (65%) to 0.3" (40%) to 0.9" (20%) MOD Jefferson 400 PM TO 800 PM 0.1" (65%) to 0.3" (40%) to 0.9" (20%) MOD Foothills above 6500ft Â Â Â Boulder Current TO 800 PM TUE 0.1" (95%) to 0.3" (70%) to 0.9" (30%) MOD Douglas Current TO 800 PM TUE 0.1" (95%) to 0.3" (70%) to 0.9" (30%) MOD Jefferson Current TO 800 PM TUE 0.1" (95%) to 0.3" (70%) to 0.9" (30%) 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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 934 AM Tue June 29, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARM LAYER OF AIR ALOFT MAY PUT A LID ON THUNDERTSORM DEVELOPMENT OVER THE PLAINS? - A warm layer of air aloft at around 20,000ft is expected to suppress thunderstorm activity over the plains today with any shower or thunderstorm activity generally limited to the foothills and Palmer Divide. Late in the day moisture will increase from the S and a stray storm cannot be completely ruled out over the plains but they will be far and few between. Temperatures today will nudge upwards a few degrees into the mid 70's to around 80 over the I-25 corridor. - Shower and weak to moderate thunderstorm activity will develop over the higher terrain W of the District during the early afternoon. Increasing moisture from the S or an outflow from foothill storms may be able to generate isolated showers and weak thunderstorms over the plains by 3 or 4pm. With ample surface moisture in place if a thunderstorm is able to develop it will have the potential for moderate rainfall. - The current impression is that the warm layer of air aloft will hold and keep thunderstorm activity limited to the higher terrain W and S of the District with any activity within the District being weak and short lived. If the warm layer of air aloft erodes the HPO may need to be updated to increase the chances for thunderstorms and heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" in 10-30 minutes. Moderate thunderstorms will produce 0.2-0.5" in 10-30 minutes. WORST CASE SCENARIO: The warm layer of air aloft erodes allowing for more numerous moderate and strong thunderstorms with the potential to produce heavy rainfall rates of 0.4-1.0" in 10-30 minutes. A LOOK AHEAD: We will tack on a few more degrees to high temperatures on Wednesday and add a little more moisture. With more heat and moisture to work with there will be a better chance for afternoon thunderstorms, some of which may contain heavy rainfall. Thursday and Friday will feature a high likelihood of afternoon and evening thunderstorms with the potential to produce heavy rainfall that may result in excessive runoff and flash flooding. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 400 PM TO 800 PM Trace (40%) to 0.2" (20%) to 0.5" (5%) NONE Arapahoe 400 PM TO 800 PM Trace (40%) to 0.2" (20%) to 0.5" (5%) NONE Broomfield 400 PM TO 800 PM Trace (40%) to 0.2" (20%) to 0.5" (5%) NONE Denver 400 PM TO 800 PM Trace (40%) to 0.2" (20%) to 0.5" (5%) NONE Boulder 300 PM TO 800 PM Trace (60%) to 0.2" (25%) to 0.5" (5%) NONE Douglas 300 PM TO 800 PM Trace (60%) to 0.2" (25%) to 0.5" (5%) NONE Jefferson 300 PM TO 800 PM Trace (60%) to 0.2" (25%) to 0.5" (5%) NONE Foothills above 6500ft Â Â Â Boulder 200 PM TO 800 PM Trace (80%) to 0.2" (50%) to 0.5" (15%) LOW Douglas 200 PM TO 800 PM Trace (80%) to 0.2" (50%) to 0.5" (15%) LOW Jefferson 200 PM TO 800 PM Trace (80%) to 0.2" (50%) to 0.5" (15%) LOW 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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 710 PM Mon June 28, 2021 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE AT 8:00 PM FOR PORTIONS OF THE DISTRICT - Message 1's that have been issued for Adams, Arapahoe, Denver, Douglas and Jefferson Counties will be allowed to expire at 8pm this evening as the threat for heavy rainfall has come to an end. - Most rain shower activity has cleared out of the District at this time. Skies will continue to gradually clear out through the overnight for the plains, with a few lingering scattered light rain showers still possible towards the foothills. Conditions will generally be dry, although a few light rain showers could persist through midnight, favoring areas along the foothills and west of I-25. - Overnight lows will drop into the 50's with mild conditions through the morning. A shift in the overall pattern tomorrow with a chance for rain showers/isolated thunderstorms in the afternoon which will move in from the south to north. Tomorrow will also start a warming trend over the region where we could see temperatures hit 80 degrees for the first time in several days. STORM RAINFALL POTENTIAL AND DURATION: Sprinkles to light rain will produce a trace to 0.1" in 10-30 minutes. WORST CASE SCENARIO: Light to moderate rain showers have the potential to produce 0.1-0.3" in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Jefferson County 1 Current TO 800 PM Current TO 800 PM Douglas County 1 Current TO 800 PM Current TO 800 PM Adams County 1 Current TO 800 PM Current TO 800 PM Denver County 1 Current TO 800 PM Current TO 800 PM DIA 1 Current TO 800 PM Current TO 800 PM Arapahoe County 1 Current TO 800 PM Current TO 800 PM the City of Aurora 1 Current TO 800 PM Current TO 800 PM Arvada 1 Current TO 800 PM Current TO 800 PM Wheat Ridge 1 Current TO 800 PM Current TO 800 PM Lakewood 1 Current TO 800 PM Current TO 800 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 1159 PM MON Trace (10%) to 0.1" (5%) to 0.3" (0%) NONE Arapahoe Current TO 1159 PM MON Trace (10%) to 0.1" (5%) to 0.3" (0%) NONE Boulder Current TO 1159 PM MON Trace (10%) to 0.1" (5%) to 0.3" (0%) NONE Broomfield Current TO 1159 PM MON Trace (10%) to 0.1" (5%) to 0.3" (0%) NONE Denver Current TO 1159 PM MON Trace (10%) to 0.1" (5%) to 0.3" (0%) NONE Douglas Current TO 1159 PM MON Trace (10%) to 0.1" (5%) to 0.3" (0%) NONE Jefferson Current TO 1159 PM MON Trace (10%) to 0.1" (5%) to 0.3" (0%) NONE Foothills above 6500ft Â Â Â Boulder Current TO 1159 PM MON Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Douglas Current TO 1159 PM MON Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Jefferson Current TO 1159 PM MON Trace (20%) to 0.1" (10%) to 0.3" (5%) 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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 426 PM Mon June 28, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S CONTINUE VALID FOR PORTIONS OF THE DISTRICT - Message 1's continue valid for Adams, Arapahoe, Denver, Douglas and Jefferson Counties until 8pm this evening, however the threat for heavy rainfall is diminishing. - A gust front moved through the District from NW to SE and generated a few isolated thunderstorms over eastern areas of the District but did not produce much additional activity. Now that this gust front has moved through we are lacking a trigger for new storms and the threat for thunderstorms is lowering with temperatures in the 60's to lower 70's over the plains. - A weak wave to the N may still be able to produce weak to moderate thunderstorm activity later this afternoon and early evening as it moves into the District. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" in 10-30 minutes. Moderate to strong thunderstorms will have the potential to produce 0.2-0.6" in 10-30 minutes. WORST CASE SCENARIO: A large or slower moving thunderstorm may result in up to 1.2" of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Jefferson County 1 Current TO 800 PM 245 PM TO 600 PM Douglas County 1 Current TO 800 PM 245 PM TO 700 PM Adams County 1 Current TO 800 PM 245 PM TO 700 PM Denver County 1 Current TO 800 PM 245 PM TO 700 PM DIA 1 Current TO 800 PM 245 PM TO 700 PM Arapahoe County 1 Current TO 800 PM 245 PM TO 700 PM the City of Aurora 1 Current TO 800 PM 245 PM TO 700 PM Arvada 1 Current TO 800 PM 245 PM TO 700 PM Wheat Ridge 1 Current TO 800 PM 245 PM TO 700 PM Lakewood 1 Current TO 800 PM 245 PM TO 700 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) ISSUED Arapahoe Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) ISSUED Boulder Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) LOW Broomfield Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) LOW Denver Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) ISSUED Douglas Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) ISSUED Jefferson Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) LOW Douglas Current TO 800 PM MON Trace (60%) to 0.2" (30%) to 0.6" (10%) ISSUED Jefferson Current TO 800 PM MON Trace (60%) to 0.2" (30%) 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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 216 PM Mon June 28, 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 Adams, Arapahoe, Denver, Douglas and Jefferson Counties and will be valid until 8pm this evening. - Weak to briefly moderate thunderstorms over the foothills of Boulder County earlier today has produced a gust front that is pushing SE through the District and may be a trigger for stronger thunderstorms to develop later this afternoon. Since this gust front/outflow boundary has already passed Boulder and Broomfield Counties they are not included in the Message 1's at this time but may be added later this afternoon if conditions warrant. - Moderate to strong thunderstorms will be capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding. Best chances for thunderstorms will be over the next 4-5hours. STORM RAINFALL POTENTIAL AND DURATION: Moderate to strong thunderstorms will have the potential to produce 0.3-0.8" in 10-30 minutes. WORST CASE SCENARIO: A large or slower moving thunderstorm may result in up to 1.5" of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Lakewood 1 Current TO 800 PM 245 PM TO 600 PM Arvada 1 Current TO 800 PM 245 PM TO 600 PM Wheat Ridge 1 Current TO 800 PM 245 PM TO 600 PM the City of Aurora 1 Current TO 800 PM 245 PM TO 600 PM DIA 1 Current TO 800 PM 245 PM TO 600 PM Arapahoe County 1 Current TO 800 PM 245 PM TO 600 PM Denver County 1 Current TO 800 PM 245 PM TO 600 PM Adams County 1 Current TO 800 PM 245 PM TO 600 PM Douglas County 1 Current TO 800 PM 245 PM TO 600 PM Jefferson County 1 Current TO 800 PM 245 PM TO 600 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 800 PM MON 0.1" (80%) to 0.4" (60%) to 0.8" (30%) ISSUED Arapahoe Current TO 800 PM MON 0.1" (80%) to 0.4" (60%) to 0.8" (30%) ISSUED Boulder Current TO 800 PM MON 0.1" (60%) to 0.4" (30%) to 0.8" (15%) MOD Broomfield Current TO 800 PM MON 0.1" (50%) to 0.4" (25%) to 0.8" (10%) MOD Denver Current TO 800 PM MON 0.1" (80%) to 0.4" (60%) to 0.8" (30%) ISSUED Douglas Current TO 800 PM MON 0.1" (80%) to 0.4" (60%) to 0.8" (30%) ISSUED Jefferson Current TO 800 PM MON 0.1" (80%) to 0.4" (60%) to 0.8" (30%) ISSUED Foothills above 6500ft Â Â Â Boulder Current TO 800 PM MON 0.1" (60%) to 0.4" (30%) to 0.8" (15%) MOD Douglas Current TO 800 PM MON 0.1" (80%) to 0.4" (60%) to 0.8" (30%) ISSUED Jefferson Current TO 800 PM MON 0.1" (80%) to 0.4" (60%) to 0.8" (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]

2 years, 10 months

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Flash Flood Prediction Program

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Time: 858 AM Mon June 28, 2021 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- CONTINUED UNSEASONABLY COOL WITH LESS NUMEROUS SHOWERS AND THUNDERSTORMS FAVORING THE FOOTHILLS - Temperatures will remain below seasonal averages over the District today with highs in the 70's over the plains and 60's in the Front Range foothills. Normal high for Denver today is 87 degrees. Rain showers and isolated to widely scattered thunderstorms are expected this afternoon, however the shower and thunderstorm coverage is expected to be less than previous days as moisture has decreased a bit from this time yesterday. - Rain showers and weak thunderstorms will become possible before noon, mainly in and near the foothills. Upper level steering winds at around 15mph from N to S through early afternoon and NW to SE later this afternoon is expected to keep the majority of the storm activity over the foothills. Over the plains the best chances for storms will be along and W of I-25 and S of I-70 with far NE areas of the District expected to have the lowest chance for storm activity today. - Thunderstorm strength this afternoon will hinge upon daytime heating with weak to moderate thunderstorms currently expected and temperatures reaching the low to mid 70's. Should temperatures warm more than anticipated into the upper 70's stronger thunderstorms may develop and there will be a better chance for heavy rainfall. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.2" of rain. Moderate to briefly strong thunderstorms will have the potential to produce 0.2-0.6" in 10-30 minutes. WORST CASE SCENARIO: Temperatures warm further than anticipated resulting in strong thunderstorms with the potential to produce 0.4-1.2" of rain in 10-30 minutes and up to 2.0" in 45-60 minutes. A LOOK AHEAD: A similar outlook on Tuesday with isolated to widely scattered afternoon thunderstorms and temperatures in the 70's for highs. A low threat for heavy rainfall is expected. We add more heat and moisture into the equation from Wednesday through Friday resulting in a moderate to high threat for heavy rainfall producing thunderstorms each day, likely peaking on Friday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams 100 PM TO 1000 PM 0.1" (60%) to 0.3" (30%) to 0.6" (10%) LOW Arapahoe 100 PM TO 1000 PM 0.1" (70%) to 0.3" (50%) to 0.6" (20%) LOW Broomfield 100 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Denver 100 PM TO 1000 PM 0.1" (70%) to 0.3" (50%) to 0.6" (20%) LOW Boulder 1200 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Douglas 1200 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Jefferson 1200 PM TO 1000 PM 0.1" (80%) to 0.3" (60%) to 0.6" (25%) MOD Foothills above 6500ft Â Â Â Boulder 100 PM TO 1000 PM 0.1" (90%) to 0.3" (70%) to 0.6" (40%) MOD Douglas 100 PM TO 1000 PM 0.1" (90%) to 0.3" (70%) to 0.6" (40%) MOD Jefferson 100 PM TO 1000 PM 0.1" (90%) to 0.3" (70%) to 0.6" (40%) 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]

2 years, 10 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 825 PM Sun June 27, 2021 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S WILL BE ALLOWED TO EXPIRE, ADDITIONAL RAIN SHOWERS TO CONTINUE INTO THE LATE EVENING - Message 1's will be allowed to expire at 9:00pm as the threat for heavy rainfall from thunderstorms has ended for the day. - A weak disturbance upstream is expected to produce additional widely scattered light rain showers through about midnight, likely favoring areas W of I-25 and over the foothills. Beyond midnight there could be a few lingering, isolated showers that persist into early Monday morning. Showers will move briskly from N to S at around 15mph. Although unlikely, if a weak thunderstorm were to develop it would be capable of producing brief heavy rainfall. - Due to all of the moisture as of late over large areas of the District it may not take much additional rain to produce runoff and smaller creeks and streams may be susceptible to higher flows into the evening. STORM RAINFALL POTENTIAL AND DURATION: Rainfall rates from light rain showers will generally range from a trace to 0.2" in 30-60 minutes with moderate rain showers producing rainfall rates of 0.2-0.5" in 30-60 minutes. WORST CASE SCENARIO: Weak to moderate thunderstorms are able to develop with the potential to produce brief heavy rainfall of 0.3-0.9" in 10-30 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Denver County 1 Current TO 900 PM Current TO 800 PM MONDAY Adams County 1 Current TO 900 PM Current TO 800 PM MONDAY Douglas County 1 Current TO 900 PM Current TO 800 PM MONDAY Broomfield County 1 Current TO 900 PM Current TO 800 PM MONDAY Jefferson County 1 Current TO 900 PM Current TO 800 PM MONDAY Boulder County 1 Current TO 900 PM Current TO 800 PM MONDAY DIA 1 Current TO 900 PM Current TO 800 PM MONDAY Arapahoe County 1 Current TO 900 PM Current TO 800 PM MONDAY the City of Aurora 1 Current TO 900 PM Current TO 800 PM MONDAY Arvada 1 Current TO 900 PM Current TO 800 PM MONDAY Wheat Ridge 1 Current TO 900 PM Current TO 800 PM MONDAY Lakewood 1 Current TO 900 PM Current TO 800 PM MONDAY County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 60-Minute Rainfall and % Probability Message Potential Plains Â Â Â Adams Current TO 400 AM MON Trace (75%) to 0.2" (50%) to 0.5" (15%) NONE Arapahoe Current TO 400 AM MON Trace (75%) to 0.2" (50%) to 0.5" (15%) NONE Boulder Current TO 400 AM MON Trace (75%) to 0.2" (50%) to 0.5" (15%) NONE Broomfield Current TO 400 AM MON Trace (75%) to 0.2" (50%) to 0.5" (15%) NONE Denver Current TO 400 AM MON Trace (75%) to 0.2" (50%) to 0.5" (15%) NONE Douglas Current TO 400 AM MON Trace (75%) to 0.2" (50%) to 0.5" (15%) NONE Jefferson Current TO 400 AM MON Trace (75%) to 0.2" (50%) to 0.5" (15%) NONE Foothills above 6500ft Â Â Â Boulder Current TO 400 AM MON Trace (95%) to 0.2" (60%) to 0.5" (20%) NONE Douglas Current TO 400 AM MON Trace (95%) to 0.2" (60%) to 0.4" (20%) NONE Jefferson Current TO 400 AM MON Trace (95%) to 0.2" (60%) to 0.4" (20%) 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]

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hpo-ims June 2021