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Displaying AFOS PIL: AFDBOU Received: 2022-04-07 15:20 UTC
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832 FXUS65 KBOU 071520 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 920 AM MDT Thu Apr 7 2022 .UPDATE... Issued at 909 AM MDT Thu Apr 7 2022 Winds are picking up as scheduled over the plains, where gusts of 55-70 mph are likely once more. Blowing dust will be an additional hazard through the afternoon, and current satellite imagery depicts a few dust plumes beginning to surface over Washington County. May consider Blowing Dust Advisories down the line depending on how widespread/persistent the blowing dust looks to be. Overall, we're just a little more moist compared to this time yesterday, both on the ground and in the mid levels, with some scattered cumulus likely over the plains through the day. Nonetheless, Red Flag conditions look largely on track, particularly around the Denver metro where humidity will be lowest. May be tough to technically reach the 15% threshold over parts of the plains with increased cloud cover and winds, but given the strength of the winds, fire concerns are warranted regardless. No major changes to the forecast needed this morning. && .SHORT TERM...(Today and tonight) Issued at 402 AM MDT Thu Apr 7 2022 Windy and dry conditions will persist today as the upper low continues to drift slowly east. The strong pressure gradient remains in place between that system and high pressure building over the Rocky Mountains ahead of the approaching ridge. The flow aloft will turn more northerly between them and jet winds move overhead. There will still be moderate to strong synoptic subsidence and good mixing to around 650 hPa, into 30 to 60 knot winds. Expect another day of strong and gusty winds across the plains from late morning through early evening, now more northerly. Peak afternoon winds should be 30 to 40 mph gusting up to 65 mph, strongest further east. We have maintained our High Wind Warning for our eastern plains from 9 AM to 7 PM. It will also still be quite dry with critical and near-critical afternoon humidity of 10 to 20 percent across the lower elevations. This means another day of widespread critical fire weather conditions across the plains. It will be driest closer to the foothills and the strongest winds will be over the eastern plains. We have maintained our Red Flag Warning for all our plains from 9 AM through 8 PM. Blowing dust is also likely again due to steep low level lapse rates over 9 C/km. Areas of blowing dust will significantly reduce air quality and visibility, the latter often resulting in significant travel impacts. This hazard has been included in our High Wind Warning. The cooling trend ends today with temperatures just a few degrees warmer than those yesterday. Highs should be in the upper 40s to mid 50s on the plains and 20s to upper 30s in the high country. Winds will decrease quickly with decoupling in the early to mid evening though should remain a bit breezy overnight, gusting up to around 30 mph over the eastern plains. It should be dry and mostly clear through the night and low temperatures fall to the single digits and teens in the high country, still 20s to lower 30s on the plains. .LONG TERM...(Friday through Wednesday) Issued at 430 AM MDT Thu Apr 7 2022 A broad trough that has been responsible for our windy weather will drift eastward on Friday. This will pull the northerly jet stream associated with this trough to the east with it. Wind speeds will decrease as a surface pressure gradient decreases and winds in the low levels decrease as well. Nonetheless, there may be some gusts across the far eastern plains up to 30 mph as some of the northerly winds at the top of the boundary layer are able to mix down with daytime heating. Meanwhile, warm air advection and plenty of sunshine will increase high temperatures to the 60s across the plains. The dry and somewhat gusty conditions will lead to near critical fire weather conditions and the potential for fire weather highlights is discussed in the fire weather section below. A ridge will move over our forecast area Friday night and into Saturday with a trough hot on its tail. Continued warm air advection will increase 700 mb temperatures to around 8 or 9 C. With mostly sunny skies, near dry adiabatic low level lapse rates are expected and based on those 700 mb temperatures, highs in the mid to upper 70s will occur. Lee cyclogenesis will develop over northeastern Colorado and with winds aloft increasing ahead of a trough over the Pacific Northwest, gusty winds will form. The dry conditions along with gusty winds will likely lead to areas of critical fire weather conditions across the plains that may need highlights. A trough that was over the Pacific Northwest on Saturday will dig towards Colorado on Saturday night and Sunday. Strong 700 mb frontogenesis along with QG ascent from the trough will combine to create scattered showers late Saturday and into Sunday morning. These showers will be focused over the mountains, in particular the western slopes, while the downslope, westerly winds dissipate most of the showers across the plains. Over some of the higher mountain peaks and ridges there will be an inch or two of snow accumulation. A cold front that pushes across the area will decrease high temperatures 10 to 20 degrees on Sunday. There are considerable model differences in the Sunday and Monday timeframe. Some solutions show this period being mostly dry as zonal flow or slight ridging result in weak subsidence. Other solutions show this period being active with warm air advection and frontogenesis providing lift. It is hard to tell which solution will be right at this time due to the large range in solutions but it warrants a mention of precipitation in the forecast. A secondary shortwave trough will move over the West Coast late on Monday and will be near the Four Corners on Tuesday before it ejects onto the High Plains on Wednesday. It is this trough that will need to be watched closely as there is potential for significant impacts. This is because this trough is forecast to be 2 to 3 standard deviations below the normal 500 mb heights with an anonymously strong ridge over the eastern US. In between, a strong temperature gradient will form and will be the focus for a deep surface cyclone to develop. It is still too early to talk about specific details in the forecast since there is too big of a spread in the different global models and their ensembles on the location and strength of this trough. However, recent model runs have shifted this trough further north and if this trend continues, there will be less precipitation that falls over our forecast area and the chance for critical fire weather conditions would increase. If the model solutions that have the trough going further south verify, our forecast area would see more precipitation and snowfall along with colder temperatures and a smaller fire weather threat. The only thing that seems like a good bet is a healthy mountain snowfall since the NBM has probabilities of over 6 inches of snow well over 50 percent from this storm. Due to the northward shift in model predictions for the trough, PoPs were lowered across the plains Tuesday and Wednesday to take out the mention of likely precipitation. There just seems to be too high of a chance that our area has the dry slot go overhead to have likely PoPs in the forecast. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 909 AM MDT Thu Apr 7 2022 VFR through TAF period. N winds will strengthen late morning into afternoon, with gusts 30-40 kt likely and possible periods of BLDU in vcnty of KDEN. FEW-SCT mid level clouds AOA 080. Rapid weakening of winds expected after ~01Z, with some uncertainty in wind direction until 08Z before return to SW drainage flow overnight. Leaning toward period of NE winds after 02Z with clockwise rotation toward drainage through the evening. && .FIRE WEATHER... Issued at 402 AM MDT Thu Apr 7 2022 Windy and dry conditions will persist today and there will again be widespread critical fire weather conditions across the lower elevations from mid morning through early evening. Expect strong and gusty northerly winds across the plains, 30 to 40 mph gusting up to 65 mph by early afternoon. These winds will be coincident with critical and near-critical humidity of 10 to 20 percent across the lower elevations. It will be driest closer to the foothills and the strongest winds will be over the eastern plains. We have maintained our Red Flag Warning for all our plains from 9 AM through 8 PM. Temperatures will warm slightly above normal on Friday with the dry air remaining in place. Minimum relative humidity will drop to the mid teens across the plains as a result. With regards to fire weather conditions, winds will be the biggest uncertainty. Forecast models that have better mixing show stronger winds with gusts up to 30 mph possible. However, there is a chance those models are over doing the mixing and wind gusts will only reach 20 to 25 mph. Therefore, there is potential for critical fire weather conditions to occur across the plains but there is too much uncertainty to issue highlights at this time. Temperatures warm further on Saturday with similar moisture in place meaning relative humidity will drop to the low teens. West to southwest winds will increase in the afternoon due to a developing low pressure system in the area with gusts up to 30 mph. Critical fire weather conditions are likely and fire weather highlights will be needed soon. && .BOU WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 7 PM MDT this evening for COZ042-044- 046>051. Red Flag Warning until 8 PM MDT this evening for COZ238>251. && $$ UPDATE...Rodriguez SHORT TERM...EJD LONG TERM...Danielson AVIATION...Rodriguez FIRE WEATHER...Danielson/EJD