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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 010644 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1244 AM MDT Thu Jun 1 2023 .UPDATE... Issued at 735 PM MDT Wed May 31 2023 Satellite and radar both indicate that most of our storms have weakened over the past couple of hours. The one notable exception was the storm north of New Raymer in northeast Weld county, that likely dropped greater than golf ball sized hail across rural portions of the county... but that storm has exited the CWA and now only weak convection remains. Across the metro, we should see a brief increase in showers/weak storms this evening as one last wave of convection enters the area, but these storms aren`t likely to produce any severe risk given a largely unfavorable environment. A few isolated storms will continue across the plains this evening as well. Most places should see rain come to an end around midnight, with just an isolated shower or storm possible after. Have made some changes to the PoP grids to match up with current radar and the latest forecasts from the RAP/HRRR through the overnight, but otherwise the grids were in good shape. && .SHORT TERM...(This evening through Thursday) Issued at 243 PM MDT Wed May 31 2023 Scattered thunderstorms initiated over the foothills and southern Front Range mountains early this afternoon, and will slowly drift into the urban corridor and plains over the next couple of hours. Dew points over much of the plains are hovering in the 50`s under moist southeasterly low-level flow, except for the Denver metro which is staying drier owing to the downslope flow from the Palmer Divide and warmer urban temperatures. As previously stated, shear is very marginal today and not particularly supportive of long- lived severe thunderstorms, however some stronger to locally marginally severe storms will certainly still be possible in the plains later this afternoon. Greatest threat for small hail and heavier rain should be east of the I-25 corridor, particularly in the northern plains, where MLCAPE values near or slightly above 1,000 J/Kg this afternoon will be more supportive. Storms that drift east off the higher terrain may initially carry a threat of strong gusty outflow winds with drier near-surface conditions and healthy DCAPE progged to be exceeding 1,000 J/Kg over the next few hours. Forecast soundings suggest mid-level moisture will be slow to clear overnight, and we could very well see lower cloud cover persist into the morning on Thursday. This will help sustain lower temperatures with highs that will likely struggle to climb into the mid 70`s across the lower elevations tomorrow. With that, instability will also be more marginal, and suspect convective activity over the urban corridor and plains may be late to develop and somewhat subdued. The mountains will be better positioned to be the focus of activity Thursday, with increased moisture and potentially less morning cloud cover. Southerly to southeasterly winds also look fairly robust tomorrow as the closed low ejects northeast into western Colorado, and may help promote convergence over the foothills to enhance rainfall as well as sustain convection over the higher terrain for longer. Considering this, anticipate a slightly higher threat of heavy rain for recent burn scars, but overall threat of severe weather will be on the low end. .LONG TERM...(Thursday night through Wednesday) Issued at 243 PM MDT Wed May 31 2023 A shortwave trough will move across our CWA Friday morning and will end up near Cheyenne, WY during the afternoon. This will push the best lift and instability away from our CWA but there will still be upward motion over the far northeast plains of Colorado. With good moisture in place and morning sunshine, weak instability will develop and showers and storms will form in the afternoon and evening. The lack of deep layer and low level shear will keep the majority, if not all, of the storms below severe limits. There is a small concern about flash flooding over the burn areas but not a particularly high threat. A shortwave over northeast New Mexico will develop an MCS on Friday night which models are predicting to develop an MCV. This MCV moves northwestward into northeast Colorado on Saturday morning. This could have moderate to heavy rainfall associated with it if it does develop as models say. Saturday looks like a cool day with a good chance of rain showers across much of our CWA. Highs will likely stay in the 60s across the plains. The precipitable water values will be near the max moving average on the SPC sounding climatology page. With so much moisture in place, there is a possibility that warm rain processes develop and some areas may see some minor flooding although the risk seems low at this time. A ridge aloft will strengthen over the Northern Plains on Sunday and the shortwave trough over Colorado will slowly weaken and move off to the west. The ridge will help develop deep upslope flow across eastern Colorado although the strength of the winds will be low. Ample moisture will stay in place so Sunday will be another day of widespread showers and storms. The ridge aloft becomes more dominant on Monday through mid next week. This will likely allow for more sunshine than clouds each morning which would result in better instability. Since good moisture will linger in Colorado, scattered to widespread showers and storms will remain likely. A flash flooding threat exists during this period but details are low. Otherwise, temperatures will be below normal with light winds. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1237 AM MDT Thu Jun 1 2023 VFR conditions are expected through Thursday morning, though there is a chance of some localized IFR/MVFR ceilings for a few hours around 12z. Scattered thunderstorms are expected between 21z and 02z with localized MVFR visibilities and variable winds gusting to 35 knots. && .HYDROLOGY... Issued at 243 PM MDT Wed May 31 2023 Another round of afternoon showers and thunderstorms can be expected over the high country Thursday. These may produce heavier precipitation relative to previous days with increased moisture in place. Some may be slow moving, with general progression being south to north, and will thus result in a slightly higher burn scar flash flood threat. The latest data suggests storms on Friday will not be very strong and they may avoid the burn areas for the most part. However, they will be moving slowly so a limited flash flood threat over the recent burn areas will still exist. On Saturday and Sunday, precipitable water values will be near record levels. The limiting factor will be the amount of sunshine, or lack thereof, throughout the day. At the moment, each day appears very cloudy which would keep the flash flood threat at limited. However, if more instability is expected to develop in future forecasts, these days could have an elevated risk of flash flooding. During next work week, instability will increase with similar moisture values and storm motion. Therefore, an elevated risk of flash flooding may exist over the burn areas. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Hiris SHORT TERM...Rodriguez LONG TERM...Danielson AVIATION...Gimmestad HYDROLOGY...Rodriguez/Danielson NWS BOU Office Area Forecast Discussion
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