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FXUS65 KBOU 301533 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 933 AM MDT Tue Apr 30 2024

KEY MESSAGES

- Snow for the northern mountains diminishing

- Gusty west winds to 40 mph in/near foothills and over far northern Colorado.

- Cooler Wednesday night and Thursday with a chance of scattered showers and light mountain snow.

UPDATE
Issued at 919 AM MDT Tue Apr 30 2024

Current radar indicates the snow is diminishing in the northern mountains as expected this morning. There was a brief passing shower here at the office as some of the mountain showers made their way off the higher terrain bringing some gusty westerly winds and a very picturesque double rainbow. These showers are quickly fading and still on track for all precipitation to come to an end by late this morning. All else looks on track with the current forecast, therefore we will let it ride.



SHORT TERM /Through tonight/
Issued at 312 AM MDT Tue Apr 30 2024

Radar showing a band of rain and mountain snow over northwest Colorado and southern Wyoming in advance of an upper level trough.
This trough will race east-northeast this morning and be over western Nebraska and South Dakota by early afternoon. As this area rain and mountains moves across the northern mountains, expect it to drop 1 to 5 inches of snow by mid morning. It quickly dries behind the trough axis by late morning. Dry conditions are expected east of the mountains with a westerly downslope flow prevailing. A shallow cold front drops south across eastern Colorado around sunrise, but downslope flow will exist above it.
The shallow cool airmass is expected to mix out and gusty westerly winds to 30-40 mph are expected spread across the foothills and far northern Colorado by noon. Surface low pressure trough forms along the base of the foothills late in the day. This will cause winds to turn easterly over the plains and transport moisture into eastern Colorado tonight. A few weak showers will be possible late tonight over the plains. Better chance for showers will be over the northern mountains after midnight where the right entrance of the jet could produce showers. After this morning's snow over the north central mountains, any additional precipitation tonight is expected to be very light due to limit moisture.

LONG TERM /Wednesday through Monday/
Issued at 312 AM MDT Tue Apr 30 2024

Not too many changes in the long-term forecast package as an unsettled pattern brings increasing chances of precipitation across northeastern Colorado. Southwesterly flow and mid-level moisture increase Wednesday as the first shortwave trough approaches Colorado. This system mostly clips our area with majority of upper level forcing staying to the north in Wyoming. MLCAPE values remain weak and range between 100-200 J/kg. Additional, lapse rates near 7 C/km and weak 3km shear values of 15-20 kts should lead to scattered showers and an isolated thunderstorms or two for the lower elevations. With scattered to numerous showers continuing through Wednesday evening, light snow will occur for elevations above 10k ft through Thursday. Highest accumulations of 3-6 inches could occur for the Park and Gore Ranges.

Thursday morning and afternoon, temperatures are slightly cooler.
The mountains and valleys With model guidance trending downwards on shower coverage. Cross sections indicate a substantial amount of dry air aloft between the 500-700mb layer. Thus, PoPs were also lowered Thursday afternoon as showers could be more isolated across the region. An additional shortwave trough arrives Friday which increase precipitation chances once more. This pattern continues through Saturday although, coverage of showers decrease especially across the mountains.

500mb ensembles display a ridge building into the region by Sunday. This update includes an increase to afternoon temperatures Sunday into next week with majority of guidance favoring the return of above normal temperatures.

AVIATION /12Z TAFS through 12Z Wednesday/
Issued at 530 AM MDT Tue Apr 30 2024

VFR to prevail through tonight. A cold front is pushing through the Denver area at this time and will bring gusty north winds with it. Winds direction then gets tricky. Expect winds to decrease and turn northeast by 13Z. The winds then transition to the west- northwest and increase as stronger winds aloft mix down. This is expected to occur 17-18Z. The strongest winds are expected to be in the 18Z to 21Z period with gusts to 30 knots possible. Winds then decrease and turn clockwise, becoming an east to southeast direction after 00Z Wednesday.

BOU WATCHES/WARNINGS/ADVISORIES
None.

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