Area Forecast Discussion
Issued by NWS Denver/Boulder, CO
Issued by NWS Denver/Boulder, CO
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715 FXUS65 KBOU 101745 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 1145 AM MDT Fri May 10 2024 .KEY MESSAGES... - Showers will gradually decrease over the mountains and foothills through the day today, with snow levels around 9,000 ft. No travel impacts expected the rest of today. - Temperatures will stay below seasonal normals today. - Gradual warming this weekend and through Tuesday along with scattered showers and thunderstorms, most numerous this weekend and Tuesday onward. && .UPDATE... Issued at 959 AM MDT Fri May 10 2024 A few minor updates were made to today`s forecast. First, we cancelled the winter weather advisory for the mountains because area webcams confirm roads have completely melted where snow had fallen, and where snow is actively falling (mostly southern half of Park County), the May sun angle is already significant enough to keep the roads wet. So with all mountain passes now clear, no more travel impacts are expected the rest of the day. We also updated the PoPs for today, mostly knocking them down below 6,000 ft elevation. CAMs are getting drier with each run. A look at the most recent CAMs for today shows the best chance for precip across the southern foothills and mountains (BoCo and south) and Park County. Not much accumulation is expected east of there anymore so we trimmed PoPs to 20 percent or less east of the terrain. It looks to remain dry east and north of Denver. The rest of the forecast looks on track. && .SHORT TERM /Through tonight/... Issued at 327 AM MDT Fri May 10 2024 Area radars, observations and web cameras indicated light rain showers over the southern plains and Palmer Ridge of the CWA at this time. Light to moderate snow is falling over the southwestern CWA, including Park County. Temperatures are currently in the upper 30s to mid 40s over the plains, and 30s in the foothills. Models show an upper closed low over the southern Great Basin into central Utah today with a weak upper tough axis stretched west to east across the CWA. By 12Z Saturday morning, the upper low is over northwestern Arizona with the upper trough axis across the northern border area of the CWA. QG fields have weak upward vertical velocity for much of the CWA today and tonight. The low level wind and pressure fields show weak to no upslope for the plains today. For tonight, weak drainage winds are progged. There is fairly deep moisture in place today for much of the CWA. Moisture decreases this evening and overnight in all areas. There is weak CAPE progged this is afternoon and evening, mainly over the mountains and foothills. Will keep the basic trend going with the pops in the forecast. The highest pops will be over the alpine areas and southwestern CWA this morning, with a gradual decrease through the day. There will be low to no pops over the eastern half of the plains today with "scattered" pops for the western half. Will leave the winter weather highlights going in Zones 34, 36, and 37 through 18Z today. For temperatures, today`s highs look to get 1-3 C warmer over most of the CWA compared to yesterday`s readings. However readings will stay below seasonal normals. && .LONG TERM /Saturday through Thursday/... Issued at 136 AM MDT Fri May 10 2024 Over the weekend, the upper-level low previously to our southwest will reverse course as building high pressure pushes it northeast into the plains, and it will weaken slightly as it does so. Thermal ridging will be more evident across the lower levels, allowing for temperatures to climb into the upper 60`s for the majority of the lower elevations. Marginal instability with MLCAPE values 400 J/Kg or less and lingering mid-level moisture will sustain isolated to scattered showers/thunderstorms, most numerous in the mountains. Moisture looks more vertically consistent during the morning and early afternoon hours Sunday, so have adjusted timing of higher PoPs to reflect this. Snow levels during the weekend will generally hover around 10,000 ft during the warmer parts of the day. The ridge axis should become more prominent over the region by Monday, bringing weaker northwest flow aloft and additional warming. Temperatures will climb into the 70`s for the plains and urban corridor, returning to near or slightly above normal values. QG forcing appears minimal and forecast soundings suggest a more stable profile, so showers/thunderstorm coverage should be notably more isolated, and largely confined to the higher terrain. Tuesday will start to usher in some pattern changes as a developing trough impacts the northern Rockies. Flow aloft will become more westerly/southwesterly, with increasing PWAT values. Differences in timing among ensemble guidance starts to become more significant around this time, but the overall consensus suggests an increase in thunderstorm coverage across the region. Low-level flow may still be rather subsident with drier downslope flow in the lee of the Front Range, which will help sustain warmer temperatures well into the 70`s. This could ultimately taper the precipitation potential in the afternoon for areas along the I-25 corridor, with higher potential focused over the plains where instability looks to be maximized. Expect cooler temperatures Wednesday into Thursday as a cold front pushes south through the region, along with precipitation chances ticking up another notch. && .AVIATION /18Z TAFS through 18Z Saturday/... Issued at 1145 AM MDT Fri May 10 2024 DEN should remain in VFR conditions through Saturday, though can`t rule out thickening clouds around 025-035 with afternoon showers which should stay to the west. BJC and APA will have MVFR conditions into the early evening hours, especially when the chances of showers increase after 21Z. Light rain with slightly lower CIGs would be the result of any showers this afternoon. By 01 or 02Z showers should have ended and light drainage flow will be the norm through about 14Z (SSW at APA and DEN, WSW at BJC, under 10 kts). On Friday there is a better chance of showers during the afternoon at the metro area terminals, and there is a chance of thunder but for now it`s 10, maybe 15% and thus too low to include in the TAFs this far out. Winds are expected to be out of the south or southwest, and could gust over 20 kts during the afternoon. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Schlatter SHORT TERM...RJK LONG TERM....Rodriguez AVIATION...Schlatter