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National Weather Service Forecast Discussion |
National Weather Service Forecast 48 Hour Graphical Forecast Today's Weather Story |
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000 FXUS65 KBOU 031826 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1226 PM MDT Sat Jun 3 2023 .UPDATE... Issued at 916 AM MDT Sat Jun 3 2023 An impressive plume of moisture can be seen on water vapor imagery extending from the Gulf of Mexico northwest through Colorado and into the northern Rockies. On the ground, widespread and mostly light to moderate rain can be found over a good portion of the plains, the Palmer Divide, and northern I-25 corridor. A few localized heavier cells have been forming throughout the morning south and southeast of Denver, coinciding with a water vapor maxima and likely some subtle surface boundaries. The heaviest cells have produced 0.25-0.50" of rainfall, and have certainly been slow moving. ACARS soundings depict very week winds through at least 500mb with some directional shear. The forecast for today looks on track. Did increase PoPs for tonight and Sunday morning, when a stronger surge of easterly flow looks to push into the northeastern quadrant of the state and reinvigorate precipitation. && .SHORT TERM...(Today and tonight) Issued at 331 AM MDT Sat Jun 3 2023 The 00Z synoptic analysis showed the large, negatively tilted trough over the western states and the ridge building to our northeast. There is moderate, southeasterly flow aloft over Colorado and an MCS coming in, and there should be widespread, persistent showers through today and tonight. Localized heavy rainfall is possible. Models continue to be very reliable and consistent, and I made no particularly significant changes to the forecast in this package. Expect persistently cloudy to overcast skies, with quite cool temperatures today followed by slightly warm nights, the range narrowed by the sky cover. High temperatures should be in the the 60s across the plains and mostly 40s and 50s across the high country, then lows in the 50s across the plains and mostly 30s across the high country. There is great moisture in place. Surface dewpoints will stay in the 40s and 50s across the plains and mostly 30s across the high country. The closest upstream sounding at AMA showed deep saturation and precipitable water of almost an inch, and that should be higher come 12Z. Models have precipitable water generally 150 to 200 percent of normal over our through tonight. All the associated cloudiness should also limit instability, however, and lapse rates look modest at best most places most of the time. Forecast soundings show long, skinny CAPE profiles and warm rain processes will dominate. Due to the unusual flow aloft, shower and thunderstorm motions will be southeasterly, upslope into the foothills which should mean increased coverage and intensity over the eastern slopes and the adjacent urban corridor compared to our usual routine. There is just a marginal risk of excessive rainfall across much of the area and widespread impacts are not currently expected, though locally heavy rainfall will probably result in localized impacts around burn, urban, and poor drainage areas. There is an elevated threat of flash flooding to the Cameron Peak burn area. Along with the lack of instability there is a lack of shear, enough to support multi-cell storms but not many (or probably any) supercells, and so there is very little threat of severe storms. There will probably be small hail and breezy, maybe a few incidents of marginally severe hail or gusts, but the primary hazard is heavy rainfall. .LONG TERM...(Sunday through Friday) Issued at 331 AM MDT Sat Jun 3 2023 Blocking pattern will persist for the upcoming week keeping a cool and unsettled pattern in place through next week. Each day will feature scattered to numerous showers and thunderstorms. Strong upper level high will remain centered over the Northern Plains and Prairie Providences Sunday and through next week. This high only drifts westward a few hundred miles all of next week. Over Colorado, a weak low trapped under the ridge will continue to slowly dissipate Sunday and Monday. Southeast flow around the dying low will keep the airmass moist with showers and thunderstorms tracking west to northwest. For Tuesday and the rest of next week, a closed low will be parked over southern California. Colorado will see weak flow aloft between the low and high with no well defined features to move across the region. Moisture will remain in place, and produce showers and storms each day. There will be more sunshine early next week, which will lead to slightly warmer temperatures. This will help the airmass to become more unstable and lead to an increase in thunderstorms. Not enough instability or shear for severe storms. However, heavy rainfall and localized flooding could become an issue with continued daily rainfall. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1222 PM MDT Sat Jun 3 2023 We`ll start with the easier aspect...the winds. Should see prevailing NE winds through early evening, followed by a period of variable and light winds in the evening before light northwesterly flow takes hold overnight. Widespread moderate rain is overspreading NE Colorado and will continue throughout the day, with CIGS primarily in the 030-060 range but with occasional lowering to 010-020 possible during heavier showers. With limited instability, believe TS potential will remain low today. Cannot completely rule out some VFR conditions at times later this evening or tonight, but even then expect periods of showers and lower CIGS. Visibility may lower to 3SM during the heaviest showers. Tomorrow, expect another active day with renewed showers and likely a higher chance of a thunderstorm in the afternoon. && .HYDROLOGY... Issued at 331 AM MDT Sat Jun 3 2023 Today and tonight are the most likely periods for heavy rainfall and flooding impacts. An MCS is coming in from the southeast and with near record values of precipitable water. There will probably be a lack of instability and shear, but widespread and persistent showers will still likely lead to impacts. Upstream and forecast soundings show deep moisture and warm rain processes are likely. Shower and thunderstorm motions will generally be southeasterly, upslope into the foothills which should mean increased coverage and intensity over the eastern slopes and the adjacent urban corridor compared to our usual routine. There is just a marginal risk of excessive rainfall across much of the area and widespread impacts are not currently expected, though locally heavy rainfall will probably result in localized impacts around burn, urban, and poor drainage areas in particular. There is at least a limited threat of flash flooding to all burn areas, and an elevated threat to the Cameron Peak. If cloud cover breaks enough to build some instability today then those would rise to elevated and significant threats, respectively, but I don`t think that`s very likely at this time. For Sunday and next week, there will be a limited to elevated flash flood threat for the burn areas each day. A moist easterly flow into the foothills Sunday and Monday will lead to an elevated threat for flooding in the Cameron Peak Burn Area. Meanwhile the fires west of the divide will be somewhat rain shadowed, which will keep the threat limited. For Tuesday and the rest of next week, there will be warmer temperatures, which will increase the instability and result in better chances for thunderstorms. The airmass will remain moist and heavy rain will accompany the thunderstorms each day. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Rodriguez SHORT TERM...EJD LONG TERM...Meier AVIATION...Rodriguez HYDROLOGY...EJD/Meier NWS BOU Office Area Forecast Discussion
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