Sunrise 5:51 AM   Sunset 7:59 PM Moonrise 4:27 AM   Moonset 5:23 PM

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FXUS65 KBOU 051124 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 524 AM MDT Sun May 5 2024

KEY MESSAGES

- Isolated showers and storms across the high country south of I-70 through this evening.

- Warmer and windy on Sunday.

- Periods of snow showers in the mountains late Sunday night through mid week. There could be travel impacts for the Monday morning commute along the I-70 Mountain Corridor.

- Highs winds possible in the mountains and foothills Monday into Tuesday with 50% Confidence Level.

- Across the plains, expect very windy conditions Monday and Tuesday with critical fire conditions across southern Lincoln county.

SHORT TERM /Through tonight/
Issued at 333 AM MDT Sun May 5 2024

Various METARs this morning display breezy southeasterly winds across the eastern plains. This will continue this afternoon as deep mixing will occur increasing our surface winds for northeastern Colorado. Our upper level ridge pattern will shift east as the next trough enters Colorado this afternoon. 500mb wind increase between 50-60kts. As daytime heating occurs, afternoon temperatures increase between 70-77 for the plains and 48-60 for the mountains and valleys. Southeasterly winds increase this afternoon producing wind gusts up to 45 mph for the mountains, foothills, and valleys.
Additionally, wind guts up to 50-55 mph will occur across the eastern plains. With wind gusts varying this afternoon and evening, it is possible a few spots throughout the eastern plains could reach 60 mph briefly. This will likely lead to elevated fire weather conditions mainly for the urban corridor this afternoon as humidities drop near 17-20 percent. Tonight, mid-level moisture increases through the 500-700mb layer and winds across the mountains shift west. Light orographic snow begins for areas above 8 thousand feet north of I-70 through Monday.

LONG TERM /Monday through Saturday/
Issued at 333 AM MDT Sun May 5 2024

A strong storm system will move quickly across the area Mon morning and then move rapidly northeast into wrn South Dakota by late aftn. As this feature moves across, there will be a quick shot of stg QG ascent which will bring snow to the mtns in the morning.
Across the plains, expect a band of showers and possibly a tstm as the activity moves rapidly across in the morning hours.

By late morning thru the aftn there will be a decent amount of subsidence over the area as the storm system moves rapidly out of the area. Cross-sections still show some potential for a period of high winds, in some mtn areas and foothills, from mid morning thru the aftn. Cross-barrier flow will be in the 50-55 kt range but really don't have a decent mtn wave. Thus, not sure how widespread higher winds will be at this point. Overall, the ECMWF has more coverage than some of the other higher res models. For now will issue a watch for Mon. Across the plains, it will be very windy as well but wind gusts look to be below high wind criteria. Meanwhile, cross-sections show lingering moisture in the mtns with favorable orographics so will continue to see periods of lighter snow thru the aftn. As far as highs, readings will drop back in to 60s over the plains.

For Mon night into Tue, an intense storm system will be over the nrn high Plains with rather stg WNW flow aloft across the area.
Cross-sections show decreasing moisture in the mtns Mon night so will see a decrease in snow shower activity. However, moisture will increase again on Tue which will lead to periods of orographic driven snow thru the aftn. Across the plains, it will be dry Mon night into Tue with very windy conditions. Highs will remain in the 60's. Finally, over the higher terrain, there could be some threat for higher winds Mon night if a mtn wave becomes better defined as cross-barrier flow remains in the 50-55 kt range.

By Tue night, a disturbance will move across nrn CO which will allow for periods of light snow in the mtns. On Wed, the storm system will be over the Dakota's with westerly flow aloft. Latest cross- sections show a drier airmass over the area so snow chances will decrease in the mtns with dry conditions elsewhere. Highs across the plains will remain in the 60's.

Looking ahead to Thu, the main upper level low will begin to move eastward while a 2nd weaker piece of energy is over the Great Basin.
Overall, there could be a chc of light precip on Thu but the set up doesn't look as favorable as yesterday. Highs may stay mostly in the 50's across nern CO.

On Fri, the GFS has is a weak upper level low over Nevada while the ECMWF has this feature further south. The GFS has quite a bit of moisture over the area while the ECMWF is much drier. For now will just go with the blended solutions as it's not clear how things may evolve late next week.

AVIATION /12Z TAFS through 12Z Monday/
Issued at 519 AM MDT Sun May 5 2024

VFR conditions continue through the TAF period.
Winds remain south to southeast between 14-16kts with gusts up to 20-25kts. As the next system enters the region, gust increase up to 32-40kts. Clouds decks should sit near 9-11 thousand ft shifting from FEW to BKN. Strong winds are expected to continue through late Monday evening.

FIRE WEATHER
Issued at 333 AM MDT Sun May 5 2024

Elevated fire weather conditions are possible along the urban corridor this afternoon for humidities near 17-20 percent and wind gusts up to 40-50 mph.

Gusty winds and lower humidity will be over the plains Mon and Tue. However, there is still some question as to how dry the fuels are due to decent precip in the latter half of April.
The only area that didn't receive decent precip was over portions of srn Lincoln county. Thus that would be an area to watch for critical fire conditions in the afternoon and early evening hours.

BOU WATCHES/WARNINGS/ADVISORIES
Winter Weather Advisory from 6 PM this evening to 6 PM MDT Monday for COZ031.

High Wind Watch from Monday morning through late Monday night for COZ033>036.

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