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

by f2p2＠udfcd.org

Time: 819 PM Tue May 9, 2023 Forecaster: Brad Simmons ------------------------- Internal Message Status Flash Flood Prediction Program ------------------------- MESSAGE 1'S CONTINUE VALID Message 1’s will continue valid for the next few hours but may be cancelled early if conditions remain quiet over the District. Strong thunderstorms developed over parts of Adams and Denver Counties late this afternoon and produced large hail as well as moderate to heavy rainfall. These strong thunderstorms have moved out of the District but these storms also produced an outflow boundary which has pushed westward into the foothills and may be a trigger to generate additional thunderstorms this evening. If this outflow boundary does not result in new thunderstorm development Message 1’s may be cancelled early as they are currently valid until 2:00 AM Wednesday. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.4" of rain in 30-60 minutes. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.4-0.8" in 10-30 minutes. WORST CASE SCENARIO: A slow moving strong thunderstorm or training of thunderstorm cells may result in up to 1.5" of rain in 45-60 minutes. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Jefferson County 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Broomfield County 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Douglas County 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Adams County 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Denver County 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM DIA 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Arapahoe County 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM the City of Aurora 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Arvada 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Wheat Ridge 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM Lakewood 1 Current TO 200 AM WEDNESDAY Current TO 1100 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 1159 PM TUE 0.1" (50%) to 0.4" (25%) to 0.8" (10%) ISSUED Arapahoe Current TO 1159 PM TUE 0.1" (40%) to 0.4" (20%) to 0.8" (5%) ISSUED Boulder Current TO 1159 PM TUE 0.1" (65%) to 0.4" (30%) to 0.8" (15%) ISSUED Broomfield Current TO 1159 PM TUE 0.1" (60%) to 0.4" (30%) to 0.8" (15%) ISSUED Denver Current TO 1159 PM TUE 0.1" (50%) to 0.4" (25%) to 0.8" (10%) ISSUED Douglas Current TO 1159 PM TUE 0.1" (30%) to 0.4" (15%) to 0.8" (5%) ISSUED Jefferson Current TO 1159 PM TUE 0.1" (50%) to 0.4" (25%) to 0.8" (10%) ISSUED Foothills above 6500ft Boulder Current TO 1159 PM TUE 0.1" (70%) to 0.4" (30%) to 0.8" (15%) ISSUED Douglas Current TO 1159 PM TUE 0.1" (40%) to 0.4" (20%) to 0.8" (5%) ISSUED Jefferson Current TO 1159 PM TUE 0.1" (50%) to 0.4" (25%) to 0.8" (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, 7 months

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Flash Flood Prediction Program

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Time: 554 PM Tue May 9, 2023 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 and will be valid until 2:00 AM tomorrow morning. Persistent easterly surface level flow, combined with an incoming upper-level disturbance has initiated a line of thunderstorms through the District at this time. These storms have rapidly developed and will be capable of heavy rainfall, which could produce localized flooding. The best chance for storms will be from now through 8pm with another round of overnight rain showers possible between 10pm and 2am. Off and on rain shower chances will continue overnight and into daybreak Wednesday, however, the threat for heavy rainfall should diminish after 2am. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce 0.1-0.4" of rain in 30-60 minutes. Moderate to strong thunderstorms will have the potential to produce rainfall rates of 0.4-0.8" in 10-30 minutes. WORST CASE SCENARIO: Training of thunderstorm cells or a slower moving thunderstorm may result in up to 1.5" of rain in 60 minutes or less. COUNTY MESSAGE VALID TIMES PRIME TIME Boulder County 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Jefferson County 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Broomfield County 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Douglas County 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Adams County 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Denver County 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM DIA 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Arapahoe County 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM the City of Aurora 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Arvada 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Wheat Ridge 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM Lakewood 1 Current TO 200 AM WEDNESDAY Current TO 1159 PM County-specific Quantitative Precipitation Outlook PRECIPITATION TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 200 AM WED 0.1" (75%) to 0.4" (50%) to 0.8" (20%) ISSUED Arapahoe Current TO 200 AM WED 0.1" (75%) to 0.4" (50%) to 0.8" (20%) ISSUED Boulder Current TO 200 AM WED 0.1" (75%) to 0.4" (50%) to 0.8" (20%) ISSUED Broomfield Current TO 200 AM WED 0.1" (75%) to 0.4" (50%) to 0.8" (20%) ISSUED Denver Current TO 200 AM WED 0.1" (75%) to 0.4" (50%) to 0.8" (20%) ISSUED Douglas Current TO 200 AM WED 0.1" (75%) to 0.4" (50%) to 0.8" (20%) ISSUED Jefferson Current TO 200 AM WED 0.1" (75%) to 0.4" (50%) to 0.8" (20%) ISSUED Foothills above 6500ft Boulder Current TO 200 AM WED 0.1" (50%) to 0.4" (30%) to 0.8" (10%) ISSUED Douglas Current TO 200 AM WED 0.1" (50%) to 0.4" (30%) to 0.8" (10%) ISSUED Jefferson Current TO 200 AM WED 0.1" (50%) to 0.4" (30%) to 0.8" (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, 7 months

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Flash Flood Prediction Program

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Time: 845 AM Tue May 9, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARMER TODAY WITH ANOTHER CHANCE FOR AFTERNOON/EVE RAIN SHOWERS/ISOLATED THUNDERSTORMS Warmer today as high temperatures reach the upper 70's to nearly 80 degrees this afternoon. Another chance this afternoon and evening for a few rain showers/isolated thunderstorms, however, similar to last night, these showers will be very hit or miss across the I-25 corridor this afternoon and evening. Surface moisture will play a huge role in storm intensity today with dew points likely decreasing throughout the morning and into the afternoon. An uptick in surface moisture late this afternoon and into the early evening from the east could help initiate stronger storms later this afternoon and into this evening. There will be a low chance that these storms are able to strengthen to the point of producing heavy rainfall as dew points are projected to reach the upper 40's to low 50's this evening between 5-7pm with a good chance this elevated surface moisture sticks around through the rest of the week. The best chance for storms today will be from 5pm through midnight tonight, favoring northern portions of the District at this time. However, a gust front from a stronger storm has the potential to initiate additional storms across the District this evening. Storm intensity should diminish after midnight, with skies gradually clearing into daybreak Wednesday. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/isolated thunderstorms will produce a trace to 0.2" in 10-30 minutes. A moderate to strong thunderstorm could produce 0.2-0.5" in 10-30 minutes. WORST CASE SCENARIO: A stronger, slower moving storm formed off an out flow boundary, or training of thunderstorm cells has the potential to produce 0.5-1.5" in 30-60 minutes. A LOOK AHEAD: Upper-level flow turns southwesterly through the overnight tonight bringing a better chance for strong storm tomorrow afternoon and evening. These storms will likely produce localized heavy rainfall resulting in a better chance for some isolated flash flooding during the afternoon and early evening tomorrow. Rainfall chances will stick around through the overnight Wednesday and into Thursday with off and on rainfall chances likely throughout the day Thursday. The shower intensity Thursday will hinge on whether there is enough daytime heating. This active weather pattern continues Friday, with afternoon and evening rain showers/isolated thunderstorm chances continuing. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Arapahoe 400 PM TO 1159 PM Trace (50%) to 0.2" (25%) to 0.5" (10%) LOW Boulder 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Broomfield 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Denver 400 PM TO 1159 PM Trace (50%) to 0.2" (25%) to 0.5" (10%) LOW Douglas 400 PM TO 1159 PM Trace (40%) to 0.2" (20%) to 0.5" (10%) LOW Jefferson 400 PM TO 1159 PM Trace (40%) to 0.2" (20%) to 0.5" (10%) LOW Foothills above 6500ft Boulder 400 PM TO 1159 PM Trace (60%) to 0.2" (30%) to 0.5" (15%) LOW Douglas 400 PM TO 1159 PM Trace (40%) to 0.2" (20%) to 0.5" (10%) LOW Jefferson 400 PM TO 1159 PM Trace (40%) to 0.2" (20%) to 0.5" (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, 7 months

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Flash Flood Prediction Program

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Time: 856 AM Mon May 8, 2023 Forecaster: Justin Brooks ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- A SLIGHT CHANCE FOR A FEW HIGH-BASED RAIN SHOWERS/ISOLATED THUNDERSTORMS THIS AFTERNOON/EVE Another day with above normal temperatures with highs reaching the mid 70's this afternoon. Mostly sunny skies currently with clouds increasing this afternoon and evening. A slight chance this afternoon for a few high-based rain showers/isolated thunderstorms, however most precipitation will struggle to reach the surface with generally just a trace, with up to 0.10" possible. The best chance for shower activity will be between 2-8pm. A slightly better chance for shower activity for areas east of the I-25 corridor as storms strengthen out onto the far eastern plains late this afternoon and evening. Clouds will start to clear out late this evening with mild and dry conditions expected through the overnight and into Tuesday. Overnight lows will drop into the mid to upper 40's on the plains, with low to mid 40's along the foothill areas. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.1” of precipitation in 10-30 minutes. WORST CASE SCENARIO: A moderate thunderstorm will have the potential to produce 0.10-0.30” in 10-30 minutes. A LOOK AHEAD: Slightly warmer tomorrow along with another chance for high-based rain showers/isolated thunderstorms in the afternoon and early evening with minimal precipitation expected at this time. Slightly cooler Wednesday, however, a stronger disturbance moves over the region bringing a good chance for widespread rain showers/thunderstorms Wednesday afternoon and into the evening with some of these storms likely producing some localized heavy rainfall. This shower activity will hang around through the overnight Wednesday and into Thursday with another good chance for widespread rain showers/thunderstorms for the District during the day Thursday. Thursday's rainfall intensity will rely heavily on daytime heating and whether enough sunshine can peak through to heat the surface enough to bring stronger storms in the afternoon and evening. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 200 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.3" (5%) NONE Arapahoe 200 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.3" (5%) NONE Boulder 200 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.3" (5%) NONE Broomfield 200 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.3" (5%) NONE Denver 200 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.3" (5%) NONE Douglas 200 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.3" (5%) NONE Jefferson 200 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.3" (5%) NONE Foothills above 6500ft Boulder 200 PM TO 800 PM Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Douglas 200 PM TO 800 PM Trace (20%) to 0.1" (10%) to 0.3" (5%) NONE Jefferson 200 PM TO 800 PM 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, 7 months

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Flash Flood Prediction Program

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Time: 901 AM Sun May 7, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- ISOLATED SHOWERS AND THUNDESTORMS POSSIBLE AS A WEAK UPPER LEVEL DISTURBANCE MOVES OVERHEAD Temperatures over the plains will be slightly above normal today, warming into the lower 70’s with 50’s and 60’s in the Front Range foothills. Normal high for Denver today is 67 degrees with a record high of 89 and a record low of 23. The record high was set just last year. Clouds will be on the increase this morning, becoming partly to mostly cloudy through much of the day. A weak upper level disturbance will move through later this morning into the afternoon but most of the precipitation will skip over the District as surface moisture is lacking with dew points currently in the 20’s to around 30. There will still be a slight chance for isolated rain showers and weak thunderstorms late morning into the afternoon as the upper level feature passes overhead. Showers and thunderstorms that develop today will move quickly from SW to NE producing breezy winds and light to brief moderate rain. After 6pm chances for precipitation diminish with dry conditions expected for the overnight period. STORM RAINFALL POTENTIAL AND DURATION: Rain showers and weak thunderstorms will produce a trace to 0.1” of precipitation in 10-30 minutes. WORST CASE SCENARIO: A moderate thunderstorm will have the potential to produce 0.10-0.30” in 10-30 minutes. A LOOK AHEAD: Warmer on Monday with a low chance for an isolated afternoon thunderstorm producing minimal rainfall. We will tack on a degree or two to afternoon highs on Tuesday with a continued chance for an isolated afternoon thunderstorm in the afternoon. Tuesday evening and early overnight there could be a few rain showers that remain in the area. Better chances for thunderstorms on Wednesday as a low pressure system passes to our north with wrap around moisture on Thursday keeping a chance for rain showers and possibly an isolated thunderstorm in the forecast. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 1100 AM TO 600 PM Trace (60%) to 0.1" (30%) to 0.2" (15%) NONE Arapahoe 1100 AM TO 600 PM Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Boulder 1100 AM TO 600 PM Trace (60%) to 0.1" (30%) to 0.2" (15%) NONE Broomfield 1100 AM TO 600 PM Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Denver 1100 AM TO 600 PM Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Douglas 1100 AM TO 600 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Jefferson 1100 AM TO 600 PM Trace (60%) to 0.1" (30%) to 0.2" (10%) NONE Foothills above 6500ft Boulder 1000 AM TO 600 PM Trace (75%) to 0.1" (40%) to 0.2" (20%) NONE Douglas 1000 AM TO 600 PM Trace (70%) to 0.1" (35%) to 0.2" (15%) NONE Jefferson 1000 AM TO 600 PM Trace (60%) to 0.1" (30%) to 0.2" (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, 7 months

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Flash Flood Prediction Program

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Time: 856 AM Sat May 6, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARM/BREEZY AND GENERALLY DRY Temperatures will be warm across the District today with breezy winds and generally dry conditions. Afternoon highs over the plains will reach the low to mid 70’s with 50’s and 60’s in the Front Range foothills. Normal high for Denver today is 67°F. Winds will be from the W to SW at 10-20mph gusting between 25-35mph. Warm temperatures, breezy winds and low relative humidity values will result in increased fire danger today in areas that have not started to green up quite yet. Clouds will increase this afternoon becoming partly to mostly cloudy at times, but no meaningful precipitation is expected as the lower levels of the atmosphere are very dry resulting in virga and gusty winds from high based showers that develop versus any precipitation reaching the surface over the plains. A brief shower or sprinkle cannot be ruled out over the foothills. Winds will weaken after sunset and conditions will remain dry overnight with overnight lows in the 40’s over the plains with some 30’s in the foothills. STORM RAINFALL POTENTIAL AND DURATION: High based showers and possibly a very isolated weak thunderstorm will generally produce only a trace of precipitation over the foothills. No measurable precipitation is expected today. A LOOK AHEAD: A slight increase in moisture on Sunday will allow for isolated to widely scattered afternoon and early evening showers/thunderstorms. With surface moisture still lacking, the storms that develop Sunday will produce more wind than rain and many areas are expected to be on the drier side. 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, 7 months

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Flash Flood Prediction Program

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Time: 922 AM Fri May 5, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- GENERALLY DRY AND BREEZY WITH A SLIGHT CHANCE FOR A VERY ISOLATED SHOWER/WEAK THUNDERSTORM Conditions will trend on the dry side over the majority of the District today with above normal temperatures and breezy winds. Afternoon highs will reach the mid to upper 70’s over the plains with 60’s in the Front Range foothills. Normal high for Denver today is 66°F. Winds will be from the SW to W at 10-20mph, gusting to 30-35mph. Skies will begin the day sunny and then become partly cloudy this afternoon with any shower or thunderstorm activity likely limited to the higher mountains and foothills and over far NE Colorado leaving the District sandwiched in-between on the drier side. Isolated afternoon thunderstorms will be possible over the foothills between 1-8pm, favoring Boulder County over Douglas or Jefferson Counties. Should a shower or weak thunderstorm survive off the foothills the impacts will be minimal with storms producing more wind than rain. Overnight, conditions will be dry and winds will decrease with temperatures reaching the upper 30’s and lower 40’s for overnight lows along the I-25 corridor into Saturday morning. STORM RAINFALL POTENTIAL AND DURATION: Isolated rain showers and possibly a weak thunderstorm will produce a trace to 0.1” of rain over the lower elevations. WORST CASE SCENARIO: A foothill thunderstorm will have the potential to produce a trace to 0.2” in 10-30 minutes, favoring Boulder County. A LOOK AHEAD: Saturday will continue the dry trend for most with any chances for storms limited to the foothills. Temperatures will back off a handful of degrees with highs in the low to mid 70’s. Winds will continue breezy from the W/SW at 10-20mph, gusting to 25-30mph. A slight uptick in thunderstorm activity is expected Sunday with isolated afternoon and evening thunderstorms over the plains producing minimal moisture. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 200 PM TO 800 PM Trace (15%) to 0.1" (5%) NONE Arapahoe 200 PM TO 800 PM Trace (15%) to 0.1" (5%) NONE Boulder 200 PM TO 800 PM Trace (15%) to 0.1" (5%) NONE Broomfield 200 PM TO 800 PM Trace (15%) to 0.1" (5%) NONE Denver 200 PM TO 800 PM Trace (15%) to 0.1" (5%) NONE Douglas 200 PM TO 800 PM Trace (15%) to 0.1" (5%) NONE Jefferson 200 PM TO 800 PM Trace (15%) to 0.1" (5%) NONE Foothills above 6500ft Boulder 100 PM TO 800 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Douglas 100 PM TO 800 PM Trace (30%) to 0.1" (15%) to 0.2" (5%) NONE Jefferson 100 PM TO 800 PM Trace (25%) to 0.1" (10%) to 0.2" (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, 7 months

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Flash Flood Prediction Program

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Time: 915 AM Thu May 4, 2023 Forecaster: Brad Simmons ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- CLOUDY/COOLER WITH RAIN SHOWERS AND ISOLATED TO WIDELY SCATTERED THUNDERSTORMS An upper level disturbance is moving through the District today and will result in light rain showers this morning with additional rain showers and isolated to widely scattered thunderstorms this afternoon. Temperatures will be held down with the cloud cover with afternoon highs reaching the upper 60’s to lower 70’s over the plains with 50’s and 60’s in the Front Range foothills. Rain showers will be widely scattered this morning and light with a chance for thunderstorms developing by around noon and continuing possible until around 8:00 PM this evening. Intermittent showers and thunderstorms are expected through the day with stronger thunderstorms this afternoon capable of producing brief moderate rain and possibly small hail which may result in minor runoff. After 8:00 PM this evening the chances for precipitation will decrease with dry weather expected ahead of midnight. Total precipitation through the day is expected to be in the 0.1-0.4" range with isolated higher amounts possible under thunderstorms. Showers and thunderstorms will move from S to N through early afternoon and then upper level steering winds will be more SW to NE mid to late afternoon between 10-20mph. STORM RAINFALL POTENTIAL AND DURATION: Rain showers will produce a trace to 0.1” in 30 minutes. Weak to moderate thunderstorms will have the potential to produce rainfall rates of 0.1-0.3” in 10-30 minutes. Although unlikely a stronger thunderstorm will have the capability to produce 0.2-0.5” in 10-30 minutes. WORST CASE SCENARIO: A slower moving strong thunderstorm or training of moderate to strong thunderstorm cells may result in up to 0.3-0.7” in 10-30 minutes and up to 1.0” in 60 minutes or less. A LOOK AHEAD: Drier and warmer on Friday with best chances for thunderstorms north of the District but there will still be a modest chance for an isolated late afternoon or evening thunderstorm, favoring areas N of I-70. Temperatures will warm well into the 70’s over the plains with mostly sunny skies early becoming partly to mostly cloudy late. Daily chances for afternoon showers and thunderstorms will continue over the weekend into early next week. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams Current TO 800 PM THU 0.01" (100%) to 0.2" (50%) to 0.4" (15%) LOW Arapahoe Current TO 800 PM THU 0.01" (100%) to 0.2" (50%) to 0.4" (15%) LOW Boulder Current TO 800 PM THU 0.01" (100%) to 0.2" (50%) to 0.4" (15%) LOW Broomfield Current TO 800 PM THU 0.01" (100%) to 0.2" (50%) to 0.4" (15%) LOW Denver Current TO 800 PM THU 0.01" (100%) to 0.2" (50%) to 0.4" (15%) LOW Douglas Current TO 800 PM THU 0.01" (100%) to 0.2" (50%) to 0.4" (15%) LOW Jefferson Current TO 800 PM THU 0.01" (100%) to 0.2" (50%) to 0.4" (15%) LOW Foothills above 6500ft Boulder Current TO 800 PM THU 0.01" (100%) to 0.2" (60%) to 0.4" (20%) LOW Douglas Current TO 800 PM THU 0.01" (100%) to 0.2" (60%) to 0.4" (20%) LOW Jefferson Current TO 800 PM THU 0.01" (100%) to 0.2" (60%) to 0.4" (20%) 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, 7 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 937 AM Wed May 3, 2023 Forecaster: Laura Smith ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- WARM CONDITIONS ACROSS THE DISTRICT TODAY WITH ISOLATED SHOWERS ACROSS THE FOOTHILLS An Omega blocking pattern is in place across the continental US, suppressing thunderstorm activity along the Plains. As a result, this morning will be dry followed by afternoon temperatures in the upper 70s to low 80s. Chances for showers and thunderstorms will remain minimal today with dewpoints in the upper 20s to low 30s across the District. Areas along the foothills and Palmer Divide have slightly better chances for a brief isolated thunderstorm or two due to orographic support. The best chances for precipitation activity will be between 4PM and 8PM. With upper-level flow out of the west-southwest, showers are expected to favor mostly westerly trajectories before dissipating upon reaching the plains. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/isolated thunderstorms will produce a TR-0.10” in 10-30 minutes. A moderate rain shower/isolated thunderstorm could produce 0.10-0.20” in 10-30 minutes. WORST CASE SCENARIO: An anchored rain shower/isolated thunderstorm, or training of rain showers, has the potential to produce 0.20-0.40” in 45-60 minutes. A LOOK AHEAD: High-pressure ridging continues over the Intermountain West ahead of an upper-level disturbance slowly advancing across the Great Basin. The Omega block will begin to recede tonight, allowing moisture and upper-level support to improve across Colorado. Afternoon temperatures tomorrow will reach the mid 70s with dew points climbing into the upper 30s to low 40s, resulting in a more active weather pattern. These conditions will support widespread early afternoon to early evening showers and thunderstorms across the District. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 400 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.2" (5%) NONE Arapahoe 400 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.2" (5%) NONE Boulder 400 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.2" (5%) NONE Broomfield 400 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.2" (5%) NONE Denver 400 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.2" (5%) NONE Douglas 400 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.2" (5%) NONE Jefferson 400 PM TO 800 PM Trace (25%) to 0.1" (15%) to 0.2" (5%) NONE Foothills above 6500ft Boulder 400 PM TO 800 PM Trace (30%) to 0.1" (20%) to 0.2" (10%) NONE Douglas 400 PM TO 800 PM Trace (30%) to 0.1" (20%) to 0.2" (10%) NONE Jefferson 400 PM TO 800 PM Trace (30%) to 0.1" (20%) to 0.2" (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, 7 months

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Flash Flood Prediction Program

by f2p2＠udfcd.org

Time: 925 AM Tue May 2, 2023 Forecaster: Laura Smith ------------------------- Heavy Precipitation Outlook Flash Flood Prediction Program ------------------------- SPRING CONDITIONS PERSIST WITH SCATTERED AFTERNOON RAIN SHOWERS & THUNDERSTORMS High-pressure ridging continues over the Intermountain West today ahead of an upper-level disturbance arriving along the High Plains by midafternoon. This morning will be dry followed by afternoon temperatures in the low to mid 70s. Chances for showers and thunderstorms improve around midafternoon as daytime heating erodes the stable layer while dewpoints climb into the upper 30s to low 40s. With upper-level flow out of the south-southwest, storms are expected to favor south to north trajectories. The best chances for precipitation activity will be between 3PM and 9PM across the District broadly. STORM RAINFALL POTENTIAL AND DURATION: Typical rain showers/isolated thunderstorms will produce a TR-0.20” in 10-30 minutes. A moderate rain showers/isolated thunderstorm could produce 0.10-0.30” in 10-30 minutes. WORST CASE SCENARIO: An anchored rain shower/isolated thunderstorm, or training of rain showers, has the potential to produce 0.20-0.50” in 45-60 minutes. A LOOK AHEAD: An active week weather wise to start the season, however the threat of heavy rainfall should remain minimal at this time. The spring pattern is expected to continue Wednesday with another round of mid-afternoon to early evening showers and thunderstorms. These chances remain through the rest of the week with rain/thunderstorm chances both Thursday and Friday. LOCATION PRIME TIME 30-Minute Rainfall and % Probability Message Potential Plains Adams 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Arapahoe 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Boulder 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Broomfield 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Denver 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Douglas 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Jefferson 300 PM TO 900 PM Trace (50%) to 0.1" (25%) to 0.2" (10%) NONE Foothills above 6500ft Boulder 200 PM TO 1000 PM Trace (60%) to 0.1" (40%) to 0.2" (20%) NONE Douglas 200 PM TO 1000 PM Trace (60%) to 0.1" (40%) to 0.2" (20%) NONE Jefferson 200 PM TO 1000 PM Trace (60%) to 0.1" (40%) to 0.2" (20%) 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]

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hpo-ims May 2023