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

by f2p2＠udfcd.org

Time: 353 PM Mon July 31, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 2'S HAVE BEEN ISSUED FOR THE ENTIRE DISTRICT AND WILL BE VALID UNTIL MIDNIGHT Message 2’s (NWS Flood/Flash Flood Watch) have been issued for the entire District and will be valid from 4:00 PM until midnight tonight. Thunderstorms are expected to develop over the next 1-3 hours over the District and continue well into the evening with multiple rounds of showers and thunderstorms possible. Should thunderstorm activity persist past midnight Message 2’s may be extended into the early morning hours on Tuesday. Thunderstorms that develop later this afternoon and evening have ample moisture to work with and will be very capable of producing heavy rainfall that may lead to excessive runoff and flash flooding within the District. Storms will be relatively slow moving at 10-15mph allowing for extended periods of heavy rain. Prime time for thunderstorms will be from 5:00 PM until 11:30 PM. Heavy rainfall will be the primary threat from thunderstorms today, but large hail and gusty winds is also possible from stronger storms. The stronger thunderstorms may favor areas E of I-25 where surface moisture is more abundant. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall rates of 0.2-0.8” in 10-30 minutes. Strong thunderstorms will have the potential to produce rainfall rates of 0.8-2.0” of rain in 10-30 minutes. WORST CASE SCENARIO: A slow moving strong thunderstorm or a large thunderstorm complex may result in up to 3.5” of rain in 60-90 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 2 400 PM TO 1159 PM 500 PM TO 1130 PM Jefferson County 2 400 PM TO 1159 PM 500 PM TO 1130 PM Broomfield County 2 400 PM TO 1159 PM 500 PM TO 1130 PM Douglas County 2 400 PM TO 1159 PM 500 PM TO 1130 PM Adams County 2 400 PM TO 1159 PM 500 PM TO 1130 PM Denver County 2 400 PM TO 1159 PM 500 PM TO 1130 PM DIA 2 400 PM TO 1159 PM 500 PM TO 1130 PM Arapahoe County 2 400 PM TO 1159 PM 500 PM TO 1130 PM the City of Aurora 2 400 PM TO 1159 PM 500 PM TO 1130 PM Arvada 2 400 PM TO 1159 PM 500 PM TO 1130 PM Wheat Ridge 2 400 PM TO 1159 PM 500 PM TO 1130 PM Lakewood 2 400 PM TO 1159 PM 500 PM TO 1130 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 430 PM TO 1159 PM 0.5" (80%) to 1" (50%) to 2" (30%) ISSUED Arapahoe 430 PM TO 1159 PM 0.5" (80%) to 1" (50%) to 2" (30%) ISSUED Boulder 430 PM TO 1159 PM 0.5" (75%) to 1" (50%) to 2" (25%) ISSUED Broomfield 430 PM TO 1159 PM 0.5" (75%) to 1" (50%) to 2" (25%) ISSUED Denver 430 PM TO 1159 PM 0.5" (80%) to 1" (50%) to 2" (30%) ISSUED Douglas 430 PM TO 1159 PM 0.5" (75%) to 1" (50%) to 2" (25%) ISSUED Jefferson 430 PM TO 1159 PM 0.5" (75%) to 1" (50%) to 2" (25%) ISSUED Foothills above 6500ft Boulder Current TO 1159 PM MON 0.5" (75%) to 1" (50%) to 2" (25%) ISSUED Douglas Current TO 1159 PM MON 0.5" (75%) to 1" (50%) to 2" (25%) ISSUED Jefferson Current TO 1159 PM MON 0.5" (75%) to 1" (50%) to 2" (25%) 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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 905 AM Mon July 31, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WIDESPREAD LATE AFTERNOON AND EVENING THUNDERSTORMS WITH HEAVY RAINFALL/MESSAGE 2'S WILL BE ISSUED BY 4:00 PM Much of the District missed out on the thunderstorm activity yesterday despite elevated moisture levels but that will not be the case today as widespread thunderstorms are expected as upper level steering winds become more southwesterly pushing foothill storms eastward. Moisture is also on the increase at the surface and aloft with dew points currently in the 60’s resulting in thunderstorms that develop being very capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding. The high risk of heavy rainfall has resulted in the NWS issuing a Flood/Flash Flood Watch for the District which is valid from 4pm until midnight tonight and Message 2’s will be issued later this afternoon, possibly before 4pm. Prime time for thunderstorms will be from 3 or 4pm until midnight but could linger beyond midnight into the early morning hours on Tuesday. Storms will generally move from WSW to ENE at around 15mph, but stronger storms may move more slowly or against the grain. Heavy rainfall will be the primary threats from thunderstorms today but large hail is also possible. Temperatures will be near normal for this time of year with afternoon highs over the plains in the upper 80s to lower 90s. Normal high for Denver today is 90 degrees. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall rates of 0.2-0.8” in 10-30 minutes. Strong thunderstorms will have the potential to produce rainfall rates of 0.8-2.2” of rain in 10-30 minutes. WORST CASE SCENARIO: A slow moving strong thunderstorm or a large thunderstorm complex may result in up to 4.0” of rain in 60-90 minutes. A LOOK AHEAD: Thunderstorms will be widespread to numerous on Tuesday and Wednesday with highs only in the 80s. Thunderstorms will again be very capable of producing heavy rainfall that may lead to excessive runoff and possibly flash flooding and additional NWS Flood Watches/Message 2’s are likely. A decrease in thunderstorms is expected Thursday and Friday but there will still be a few storms with heavy rainfall a good bet. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 400 PM TO 1159 PM 0.5" (80%) to 1" (60%) to 2" (30%) HIGH Arapahoe 400 PM TO 1159 PM 0.5" (80%) to 1" (60%) to 2" (30%) HIGH Broomfield 400 PM TO 1159 PM 0.5" (75%) to 1" (50%) to 2" (25%) HIGH Denver 400 PM TO 1159 PM 0.5" (80%) to 1" (60%) to 2" (30%) HIGH Boulder 300 PM TO 1159 PM 0.5" (75%) to 1" (50%) to 2" (25%) HIGH Douglas 300 PM TO 1159 PM 0.5" (80%) to 1" (60%) to 2" (30%) HIGH Jefferson 300 PM TO 1159 PM 0.5" (75%) to 1" (50%) to 2" (25%) HIGH Foothills above 6500ft Boulder 200 PM TO 1159 PM 0.5" (80%) to 1" (50%) to 2" (20%) HIGH Douglas 200 PM TO 1159 PM 0.5" (80%) to 1" (50%) to 2" (20%) HIGH Jefferson 200 PM TO 1159 PM 0.5" (80%) to 1" (50%) to 2" (20%) HIGH 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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 653 PM Sun July 30, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S HAVE BEEN RESCINDED/MESSAGE 4'S (ALL CLEAR) ISSUED Message 1's have been rescinded and Message 4's (All Clear) has been issued for the entire District as the threat for heavy rainfall has ended for the day. Thunderstorms impacted the District this afternoon producing gusty winds and light to moderate rainfall with small areas of brief heavy rain. These thunderstorms have moved eastward with a more stable air mass now in place now that temperatures are cooling. No additional thunderstorm activity is expected this evening. An isolated rain shower cannot be ruled out this evening but additional rainfall will remain under 0.1". More of the same for tomorrow with another chance of widely scattered late afternoon and evening thunderstorms. Thunderstorms that form along outflow boundaries may become energized and contain brief heavy rainfall likely resulting in LOW to MODERATE Message potential. STORM RAINFALL POTENTIAL AND DURATION: No meaningful precipitation is expected for the remainder of the evening and overnight period, Trace to 0.1' or less. COUNTY MESSAGE VALID TIMES PRIME TIME 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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 420 PM Sun July 30, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- A FEW ISOLATED STORMS HAVE INITIATED ALONG EASTERN PORTIONS OF THE DISTRICT AT THIS TIME Message 1’s have been issued for the entire District effective until 9pm. A weak gust front collision east has initiated storms at this time, specifically around the Thornton/Brighton area. This storm has rapidly developed and will have the potential for moderate to heavy rainfall. This storm has the potential to produce additional gust fronts, similar to yesterday which could trigger additional storms, favoring eastern portions of the District through the evening. The largest storm threat will be a quick 0.5” in 10 minutes, however, a stronger storm that stalls out for an extended period should have no issue dumping over 1” per rainfall in 10-30 minutes as dew points remain elevated in some spots. Storms will taper off by sunset with skies gradually clearing through the overnight. Overnight lows will drop into the low 60’s along the plains with mid to upper 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers, weak thunderstorms will produce a 0.10-0.50” total in 10-30 minute. A moderate to strong thunderstorm will produce 0.50-1.20” total in 10-30 minutes. WORST CASE SCENARIO: A strong, anchored thunderstorm will have the potential to produce 2.00” in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Arvada 1 Current TO 900 PM Current TO 830 PM Wheat Ridge 1 Current TO 900 PM Current TO 830 PM the City of Aurora 1 Current TO 900 PM Current TO 830 PM DIA 1 Current TO 900 PM Current TO 830 PM Arapahoe County 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 Lakewood 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 SUN 0.1" (60%) to 0.5" (30%) to 1.2" (15%) ISSUED Arapahoe Current TO 900 PM SUN 0.1" (60%) to 0.5" (30%) to 1.2" (15%) ISSUED Boulder Current TO 900 PM SUN 0.1" (60%) to 0.5" (30%) to 1.2" (15%) ISSUED Broomfield Current TO 900 PM SUN 0.1" (60%) to 0.5" (30%) to 1.2" (15%) ISSUED Denver Current TO 900 PM SUN 0.1" (60%) to 0.5" (30%) to 1.2" (15%) ISSUED Douglas Current TO 900 PM SUN 0.1" (60%) to 0.5" (30%) to 1.2" (15%) ISSUED Jefferson Current TO 900 PM SUN 0.1" (60%) to 0.5" (30%) to 1.2" (15%) ISSUED Foothills above 6500ft Boulder Current TO 900 PM SUN 0.1" (50%) to 0.5" (25%) to 1.2" (10%) ISSUED Douglas Current TO 900 PM SUN 0.1" (50%) to 0.5" (25%) to 1.2" (10%) ISSUED Jefferson Current TO 900 PM SUN 0.1" (50%) to 0.5" (25%) to 1.2" (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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 921 AM Sun July 30, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SEASONABLE TEMPERATURES WITH SLOW MOVING ISOLATED AFTERNOON THUNDERSTORMS The District is located near the center of the ridge of high pressure aloft and will result in temperatures at or slightly above normal for the date and weak upper level steering winds will result in relatively slow storm motions. Afternoon highs will reach the 90-94 degree range over the plains with 80’s in the Front Range foothills. Normal high for Denver today is 90 degrees. Much like the past few days thunderstorms will initiate over the mountains and foothills W of the District by around noon or shortly after. Due to the weak upper level steering winds it will take some time for thunderstorms to develop over the plains but by 2 or 3pm storms will drift eastward or rain cooled outflow from the higher terrain storms may help generate new storms over the lower elevations. Thunderstorm coverage is expected to be isolated over the plains but the storms that do form will have the potential to produce moderate to brief heavy rainfall. Foothill storms will be more numerous and also contain a heavy rainfall threat. Prime time for thunderstorm activity will be from 2 or 3pm until around 9pm. After 9pm thunderstorm chances decrease, and generally dry conditions are expected for the later evening and overnight period. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall amounts of 0.1-0.5”. Strong thunderstorms will have the potential to produce rainfall rates of 0.5-1.2” of rain in 10-30 minutes. WORST CASE SCENARIO: A nearly stationary strong thunderstorm or a large/slow moving thunderstorm may result in up to 2.0” of rain in 45-60 minutes. A LOOK AHEAD: An uptick in thunderstorm activity is expected on Monday and thunderstorm coverage will increase further on Tuesday and Wednesday along with cooling temperatures. Ample moisture is available over the coming days for stronger storms to produce heavy rainfall that may lead to excessive runoff and possibly flash flooding in and around the District. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 300 PM TO 900 PM 0.1" (60%) to 0.5" (30%) to 1" (15%) MOD Arapahoe 300 PM TO 900 PM 0.1" (60%) to 0.5" (30%) to 1" (15%) MOD Broomfield 300 PM TO 900 PM 0.1" (60%) to 0.5" (30%) to 1" (15%) MOD Denver 300 PM TO 900 PM 0.1" (60%) to 0.5" (30%) to 1" (15%) MOD Boulder 200 PM TO 900 PM 0.1" (60%) to 0.5" (30%) to 1" (15%) MOD Douglas 200 PM TO 900 PM 0.1" (60%) to 0.5" (30%) to 1" (15%) MOD Jefferson 200 PM TO 900 PM 0.1" (60%) to 0.5" (30%) to 1" (15%) MOD Foothills above 6500ft Boulder 100 PM TO 900 PM 0.1" (80%) to 0.5" (40%) to 1" (20%) MOD Douglas 100 PM TO 900 PM 0.1" (80%) to 0.5" (40%) to 1" (20%) MOD Jefferson 100 PM TO 900 PM 0.1" (80%) to 0.5" (40%) to 1" (20%) 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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 904 PM Sat July 29, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1’S WILL BE ALLOWED TO EXPIRED AT 9:00 PM Message 1’s have been allowed to expire at 9pm as the threat of heavy rainfall has come to an end. Strong storms persist just east of the District at this time which have been producing heavy rainfall over the last several hours. These storms have pulsed up and down with a few isolated storms just within the District boundary that quickly dissipated. Storms have cleared the District at this time and will continue to move eastward through the rest of the evening. Partly cloudy skies currently will slowly clear through the overnight. Overnight with low will drop into the low to mid 60’s on the plains with mid to upper 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical showers will produce a trace to 0.1” total in 10-30 minutes. A weak to moderate shower will produce 0.10-0.30” total, in 10-30 minutes. WORST CASE SCENARIO: A thunderstorm is able to develop within the District has the potential to produce up to 0.5” in 10-30 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Denver County 1 Current TO 905 PM Current TO 905 PM Adams County 1 Current TO 905 PM Current TO 905 PM Douglas County 1 Current TO 905 PM Current TO 905 PM Broomfield County 1 Current TO 905 PM Current TO 905 PM Jefferson County 1 Current TO 905 PM Current TO 905 PM Boulder County 1 Current TO 905 PM Current TO 905 PM DIA 1 Current TO 905 PM Current TO 905 PM Arapahoe County 1 Current TO 905 PM Current TO 905 PM the City of Aurora 1 Current TO 905 PM Current TO 905 PM Arvada 1 Current TO 905 PM Current TO 905 PM Wheat Ridge 1 Current TO 905 PM Current TO 905 PM Lakewood 1 Current TO 905 PM Current TO 905 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Arapahoe Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Boulder Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Broomfield Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Denver Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Douglas Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Jefferson Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Foothills above 6500ft Boulder Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Douglas Current TO 1000 PM SAT Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Jefferson Current TO 1000 PM SAT 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 F2P2 Website [http://udfcd.org/Flash+Flood+Prediction+Program]

1 year, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 342 PM Sat July 29, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- A GOOD CHANCE FOR AFTERNOON SHOWERS AND THUNDERSTORMS WITH A SLIGHT CHANCE SOME OF THOSE STORMS BECOME SEVERE 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 boundary has also been set up along the eastern portion of the District which will likely be the focal point for stronger storm development heading into the evening with the potential some of the storms become severe. These severe storms will have strong winds, 60+ mph, hail up to 1.5". The best chance for storms will be from now through 8pm with a few lingering showers through 9pm. Storm motions will typically be from west to east between 15-20mph, which should help limit point rainfall amounts. However, 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, and a chance for rainfall over 1” in some spots, favoring eastern portions of the District at this time. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers, weak thunderstorms will produce a 0.10-0.50” total in 10-30 minute. A moderate to strong thunderstorm will produce 0.50-1.50” total in 10-30 minutes. WORST CASE SCENARIO: A strong, anchored thunderstorm will have the potential to produce 2.50” in 60-75 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 900 PM Current TO 830 PM Jefferson County 1 Current TO 900 PM Current TO 830 PM Broomfield County 1 Current TO 900 PM Current TO 830 PM Douglas County 1 Current TO 900 PM Current TO 830 PM Adams County 1 Current TO 900 PM Current TO 830 PM Denver County 1 Current TO 900 PM Current TO 830 PM DIA 1 Current TO 900 PM Current TO 830 PM Arapahoe County 1 Current TO 900 PM Current TO 830 PM the City of Aurora 1 Current TO 900 PM Current TO 830 PM Arvada 1 Current TO 900 PM Current TO 830 PM Wheat Ridge 1 Current TO 900 PM Current TO 830 PM Lakewood 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 SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Arapahoe Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Boulder Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Broomfield Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Denver Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Douglas Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Jefferson Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Foothills above 6500ft Boulder Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Douglas Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Jefferson Current TO 900 PM SAT 0.1" (75%) to 0.5" (50%) to 1.5" (25%) 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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 931 AM Sat July 29, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- CONTINUED HOT WITH ISOLATED TO WIDELY SCATTERED AFTERNOON THUNDERSTORMS Afternoon highs will once again warm into the low and mid 90’s over the plains with 80’s in the Front Range foothills. Normal high for Denver today is 90 degrees. Skies will begin sunny to mostly sunny and become partly to mostly cloudy as storms develop this afternoon. There is a surge of higher surface moisture over NE Colorado and if this feature pushes into the District the threat of heavy rainfall may end up being higher than anticipated. Otherwise, today is expected to be much like the past few days with thunderstorms developing over the foothills early in the afternoon then thunderstorm chances increase over the plains between 1-3pm. Isolated to widely scattered thunderstorm coverage is expected with typical storms producing light to moderate rainfall and gusty winds. Stronger storms may develop, especially if the higher surface moisture to the E makes it all the way back to the base of the foothills and strong storms will be capable of producing brief heavy rainfall that may lead to excessive runoff. Thunderstorms will generally move from W to E at 15-20mph but stronger storms that form along outflow boundaries may move more slowly/erratically. Thunderstorm chances will diminish by around sunset with generally dry conditions expected for the overnight period. STORM RAINFALL POTENTIAL AND DURATION: Weak to moderate thunderstorms will produce rainfall rates of 0.1-0.4” in 10-30 minutes. Strong thunderstorms will have the potential to produce 0.4-1.2” of rain in 10-30 minutes. WORST CASE SCENARIO: Surface moisture increases from a boundary approaching from the E allowing for strong thunderstorms to produce rainfall rates of 0.5-1.5” in 10-30 minutes and up to 2.0” of rain in 45-60 minutes. A LOOK AHEAD: Isolated to widely scattered afternoon thunderstorms are expected again on Sunday and Monday with temperatures continuing to run in the low to mid 90’s for afternoon highs over the plains. Monsoon moisture is expected to increase on Tuesday and Wednesday with scattered to widespread afternoon thunderstorms and a higher risk of heavy rainfall. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 200 PM TO 800 PM 0.1" (60%) to 0.4" (30%) to 1" (15%) MOD Arapahoe 200 PM TO 800 PM 0.1" (60%) to 0.4" (30%) to 1" (15%) MOD Boulder 200 PM TO 800 PM 0.1" (60%) to 0.4" (30%) to 1" (15%) MOD Broomfield 200 PM TO 800 PM 0.1" (60%) to 0.4" (30%) to 1" (15%) MOD Denver 200 PM TO 800 PM 0.1" (60%) to 0.4" (30%) to 1" (15%) MOD Douglas 200 PM TO 800 PM 0.1" (60%) to 0.4" (30%) to 1" (15%) MOD Jefferson 200 PM TO 800 PM 0.1" (60%) to 0.4" (30%) to 1" (15%) MOD Foothills above 6500ft Boulder 100 PM TO 800 PM 0.1" (80%) to 0.4" (40%) to 1" (15%) MOD Douglas 100 PM TO 800 PM 0.1" (80%) to 0.4" (40%) to 1" (15%) MOD Jefferson 100 PM TO 800 PM 0.1" (80%) to 0.4" (40%) to 1" (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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 801 PM Fri July 28, 2023 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 9pm as the threat of heavy rain has come to an end. Storms that have impacted the District have moved well east and onto the plains at this time. A few showers persist west bringing a slight chance for a few isolated showers through midnight, however most areas will remain dry. Skies will gradually clear through the rest of the overnight with clear skies likely by daybreak tomorrow. Mild and dry conditions expected through the overnight as low temperatures drop into the low to mid 60’s on the plains with mid to upper 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Any additional shower activity will be between a trace and 0.20” in 10-30 minutes. WORST CASE SCENARIO: A stronger shower is able to develop and will have the potential to produce 0.2-0.4” in 10-30 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 DIA 1 Current TO 900 PM Current TO 830 PM Arapahoe County 1 Current TO 900 PM Current TO 830 PM the City of Aurora 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 1159 PM FRI Trace (25%) to 0.2" (15%) to 0.4" (5%) NONE Arapahoe Current TO 1159 PM FRI Trace (25%) to 0.2" (15%) to 0.4" (5%) NONE Boulder Current TO 1159 PM FRI Trace (25%) to 0.2" (15%) to 0.4" (5%) NONE Broomfield Current TO 1159 PM FRI Trace (25%) to 0.2" (15%) to 0.4" (5%) NONE Denver Current TO 1159 PM FRI Trace (20%) to 0.2" (10%) to 0.4" (5%) NONE Douglas Current TO 1159 PM FRI Trace (20%) to 0.2" (10%) to 0.4" (5%) NONE Jefferson Current TO 1159 PM FRI Trace (20%) to 0.2" (10%) to 0.4" (5%) NONE Foothills above 6500ft Boulder Current TO 1159 PM FRI Trace (25%) to 0.2" (15%) to 0.4" (5%) NONE Douglas Current TO 1159 PM FRI Trace (20%) to 0.2" (10%) to 0.4" (5%) NONE Jefferson Current TO 1159 PM FRI Trace (20%) to 0.2" (10%) to 0.4" (5%) 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, 4 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 358 PM Fri July 28, 2023 Forecaster: Justin Brooks ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- A FEW STRONG STORMS SURROUND THE DISTRICT WITH A GOOD CHANCE FOR ISOLATED HEAVY RAINFALL INTO THE EVENING. An impulse of moist air at the surface moved in from the NE this afternoon. This has increased dew points from the 40’s, well into the mid to upper 50’s along northern portions of the District. This suggests the storms currently moving off the foothills around the Boulder area will have the potential to produce heavy rainfall. A slight chance for a storm or two to become severe with 60+mph winds and hail up to 1”. Storms should remain along northern portions of the District, however a gust front could produce additional storms across the District through the rest of the evening. Skies should start to clear after sundown with a few showers/light rain possible through midnight before clearing out completely. Overnight lows will drop into the 60’s along the plains with mid to upper 50’s along the foothills. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers, weak thunderstorms will produce a TR-0.50” total in 10-30 minute. A moderate to strong thunderstorm will produce 0.50-1.50” total in 10-30 minutes. WORST CASE SCENARIO: A strong, anchored thunderstorm will have the potential to produce 2.25” 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 FRI Trace (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Arapahoe Current TO 900 PM FRI Trace (65%) to 0.5" (40%) to 1.5" (15%) ISSUED Boulder Current TO 900 PM FRI Trace (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Broomfield Current TO 900 PM FRI Trace (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Denver Current TO 900 PM FRI Trace (65%) to 0.5" (40%) to 1.5" (15%) ISSUED Douglas Current TO 900 PM FRI Trace (50%) to 0.5" (25%) to 1.5" (10%) ISSUED Jefferson Current TO 900 PM FRI Trace (60%) to 0.5" (40%) to 1.5" (15%) ISSUED Foothills above 6500ft Boulder Current TO 900 PM FRI Trace (75%) to 0.5" (50%) to 1.5" (25%) ISSUED Douglas Current TO 900 PM FRI Trace (50%) to 0.5" (25%) to 1.5" (10%) ISSUED Jefferson Current TO 900 PM FRI Trace (60%) to 0.5" (40%) to 1.5" (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]

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hpo-ims July 2023