Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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948 FXUS65 KBOU 062117 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 317 PM MDT Mon May 6 2024 .KEY MESSAGES... - Very active weather pattern through the next couple days, with Winter Weather, Fire Weather, and High Wind highlights in effect - Periods of snow and blowing snow through Tuesday with some travel impacts, especially across the Park Range/Rabbit Ears Pass. - Widespread gusty winds continue through at least Tuesday, with the strongest winds expected across the higher Foothills. - Cool and unsettled weather along with much lighter winds Thursday through Saturday. && .SHORT TERM /Through Tuesday/... Issued at 135 PM MDT Mon May 6 2024 High winds will continue to be the main concern for impacts across northeast Colorado this afternoon through Tuesday. Based on surface observations, the stronger winds are across the Front Range mountains/foothills and the adjacent plains with gusts 40-60 mph and locally higher for the Front Range windy spots. Radar shows snow continuing across the mountains with CDOT cameras shows minor impacts to the higher passes. A band of showers remains over northern Weld County; however, large dewpoint depressions will make it difficult for any liquid to hit the ground. Starting with the highest impact..wind. Strong winds continue through Tuesday. Toward the early evening, winds decrease some across the urban corridor with high winds still across the Front Range mountains/foothills. More dry subsident flow moves in overnight. Model cross sections show a period of decreased moisture in the high country before the next wave approaches. There is also indication of a wave mountain wave set up during this time with cross sections showing a stable layer with increased flow aloft, and decreased moisture. This supports the potential for wind enhancement across the Front Range mountains and foothills in the 03-09z timeframe. If this were to set up, those areas could see gusts 60-75 mph and locally up to 80 mph in the windy spots, further justifying the ongoing High Wind Warning. Moisture increases again in the high country by sunrise and the pressure gradient relaxes across the Front Range which will decrease the higher magnitude winds Tuesday morning. Tuesday will still be windy, although not as windy as Monday with HREF showing mean gusts 40-60 mph for the Front Range and 30-45 mph elsewhere. Regarding snow. Snow continues in the mountains through early this evening with minor impacts to travel possible. Later in the evening, moisture decreases along with lapse rates promoting a lull in snow for a period overnight. The next wave increases and deepens moisture across the high country with steepening lapse rates early to mid AM Tuesday. This will increase snow showers across the mountains. Tues AM through late afternoon will be the best timeframe. Can`t rule out minor impacts, although May sun angle will make it difficult to accumulate on most trafficked roads. Mountain passes will have the higher chances of any impact. With windy conditions, patchy blowing snow is possible. From tonight through tomorrow, we`ll see closer to advisory level amounts. Held off for now on issuing any additional headlines with hesitation on actual travel impact. Could see up to another foot in the Park Range in spots and 4-8 inches for the Front Range mountains and mountains of Summit County with some locally higher amounts. && .LONG TERM /Tuesday night through Monday/... Issued at 135 PM MDT Mon May 6 2024 Winds will gradually subside Tuesday evening as gradients relax slightly and we lose daytime heating and mixing. There is still a moderate gradient aloft, however, so gusty winds could linger off/on overnight into early Wednesday morning in/near the foothills but to much less magnitude than tonight. With less wind, clearing skies, and a very dry airmass, there is a greater than 50% chance of sub-freezing temperatures on the plains. With the growing season beginning, we`ve opted for a Freeze Watch in all but the northeast corner where winds will stay up a bit more. There`s a greater chance we could remain above freezing in some of the western suburbs depending on wind, but opted to keep it simple for now with a contiguous area across the plains and I-25 Corridor. It`s also been quite some time since it`s frozen in the western suburbs. For Wednesday, generally lighter breezes are expected in most areas, with temperatures still averaging a few degrees below normal. We`ll be mostly caught in between moisture sources (departing to our east and another staying to our north) during the day, so only a few mountains snow showers expected. That will start to change Wednesday night and Thursday as an elongated trough slips southward into our forecast area. And yes, that will be the remnants of the deepening (current) storm system moving through the western Dakotas tonight and Tuesday. Given the increase in moisture and instability associated with the upper trough, at least scattered showers are expected Thursday and Thursday night. Temperatures will be several degrees below normal, and in fact snow levels could hover around 7,000 feet during the day, and a little lower than that at night. We don`t see any big precipitation amounts at this time, but perhaps a couple more inches for the northern mountain snowpack. For Friday into Saturday, there is still considerable uncertainty regarding how the upper trough further elongates and even shears south/southwest. The EPS members are showing strong agreement with the shearing/deeper trough into the Desert Southwest, while the GEFS is almost entirely opposite showing the elongated trough essentially getting squashed to our south and building a ridge quicker into our area. Even the EPS, however, is a little too far south and west so overall a drier weather pattern is expected to develop sometime around Friday, and then hold through most of the weekend. It`s hard to buy the EPS solution of lifting the low back to the northeast and across us toward Sunday, but definitely worth keeping an eye on as that could slow our warming trend and drier weather forecast. At this point, it`s hard to argue with the ensemble forecast which shows gradual moderation and above normal temperatures by Sunday and Monday. Low odds (~20%) that we would stay cooler with more numerous showers. && .AVIATION /18Z TAFS through 18Z Tuesday/... Issued at 1219 PM MDT Mon May 6 2024 Expect VFR conditions through the TAF period. Strong westerly, gusty winds continue this afternoon through the early evening. Gusts in the 30-40 kt range are likely this afternoon with higher gusts at BJC (~40-55 kts). Winds decrease gradually early evening 23-03z at APA and DEN out of the W/WSW. Winds may stay more elevated at BJC for for the early evening, decreasing toward midnight. 09-12z winds turn more westerly at the terminals. Winds mix out in the 14-17z timeframe Tuesday morning, bringing back gusty WNW winds although not as high as Monday. Gusts up to 35 kts possible in the afternoon. && .FIRE WEATHER... Issued at 135 PM MDT Mon May 6 2024 Critical fire weather conditions expected for southern Lincoln County and far southeastern Elbert County Tuesday. Min relative humidity dropping to 8-12% combined with gusty winds up to 40 mph will support this. The rest of the plains has potential for areas of elevated conditions in the afternoon. A Red Flag Warning will be in effect for southern Lincoln County/SE Elbert County Tuesday from 11 AM to 7 PM. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 PM MDT this evening for COZ031- 033-034. High Wind Warning until 6 AM MDT Tuesday for COZ035-036. High Wind Warning until midnight MDT tonight for COZ038-039. Freeze Watch from late Tuesday night through Wednesday morning for COZ038>049. Red Flag Warning until 9 PM MDT this evening for COZ247. Red Flag Warning from 11 AM to 7 PM MDT Tuesday for COZ247. && $$ SHORT TERM...Mensch LONG TERM...Barjenbruch AVIATION...Mensch FIRE WEATHER...Mensch