textproduct: Denver/Boulder

KEY MESSAGES

- A wave of precipitation will move across our forecast area on Thursday. This will bring 1-7" of snow to the mountains, foothills, and Palmer Divide. The plains will see mostly snow with rain mixing and little accumulation.

- More rain and snow showers Friday into Saturday, with light snow accumulations across the Foothills and Palmer Divide.

- Warmer and drier next week.

UPDATE

Issued at 829 PM MDT Wed Apr 2 2025

The last showers are departing the far northeast corner, while it remained far too dry for even sprinkles or flurries across the rest of the plains and urban corridor. That will be changing tomorrow as moisture advects northward ahead of the shortwave lifting to the Four Corners late tonight and then across area during the day Thursday. We don't have much to change with regard to the forecast, since precipitation (mostly snow) will be spreading northward. We've just refined the timing slightly based on the latest trends. Forecast of a dusting to <1" for most of the plains seems on track with some melting expected, while a little more for the Palmer with a period of slush possible during the heavier snow period late morning, and a few inches for the mountains and foothills.

SHORT TERM /Through Thursday/

Issued at 350 PM MDT Wed Apr 2 2025

Radar shows some light showers over the plains and higher terrain. These showers are not amounting to much and minimal impacts are expected.

Winds will become weaker tonight and will eventually turn to the east. There will be some small areas of fog over the far eastern plains as more moisture moves into the area. The majority of the night will be dry as the forcing will not arrive to our forecast area yet.

A shortwave trough that is currently over Arizona will move northeastward over our CWA on Thursday. There will be 700-500 mb frontogenesis along with light low level upslope winds that will provide further forcing to develop a wave of precipitation. Ensemble guidance has decreased the QPF from this system a decent amount. All global ensembles have between 0.1-0.2" QPF for Denver and Monument Hill for tomorrow. This actually seems low to me and it is possible the models have not been able to fully capture the recent precipitation that has fallen since models seem to have dew points that are too low. The high resolution models indicate there will be pockets of higher QPF especially over the far northeast corner where up to 0.5" of QPF may fall. Temperatures across the plains will be in the mid 30s when the heaviest band of precipitation will move through and most of the precipitation will fall as snow. However, given it is April, the roadways will likely only be wet so minimal travel impacts are expected. Over the Palmer Divide, there will be colder temperatures that could lead to a couple inches of accumulation. Some slushy conditions could impact travel especially on I-25 over monument hill. The foothills and Front Range mountains will be the trickiest part of the forecast. Often times in these events that come up from the south with frontogenesis, the foothills and northern I-25 corridor can miss out on some of the precipitation. So while the models may have too little precipitation over the eastern plains, models may have too much over the foothills. The forecast has generally 2-6" of snow in the foothills and 3-7" in the mountains. Since most of it will fall during the daytime, the roads should just be slushy and not completely snow-covered. Because of that, along with the chance that the lower end of the range of snow totals verifies for the foothills, no highlights were issued.

LONG TERM /Thursday night through Wednesday/

Issued at 350 PM MDT Wed Apr 2 2025

A cool/unsettled pattern will continue through the first half of the weekend, as a broad upper trough continues to meander across the region.

The upper trough should eventually close off over the desert southwest Thursday night/Friday morning, and will then track eastward across far southern AZ/NM through Friday night. At 700mb, there isn't a well-defined circulation, but guidance does push some cooler air into the region during the day Friday, with a modest increase in upslope flow as well. Recent guidance continues to trend away towards a more significant storm, with a majority of ECME/CMCE/GEFS ensemble members showing less than a quarter inch of precipitation across most of Denver... a solution that is also generally supported by their deterministic/AIFS counterparts. We'll likely see rain and snow showers for much of the day Friday into Saturday, especially across the lower foothills into the south/west metro where shallow upslope can still produce some meaningful QPF. Precipitation chances should diminish east of I-25 into the northeast plains. Generally light snow accumulations are forecast at this point, but we'll need to continue to watch model trends over the next day or so. Temperatures on both Friday and Saturday will be below normal... with highs around 40F for the Denver area.

The second half of the weekend should be much warmer, as ridging begins to build across the intermountain west. Highs bounce back into the 50s across the plains, with partly cloudy skies.

Next week should feature a continued warming trend across the region. Temperatures on Monday should be near or a little above normal across the plains, with warmer weather likely by mid-week. A shortwave is expected to race across the area Tuesday into Tuesday night, with some light snow showers across the mountains and a few rain showers over the plains. The GFS is quite bullish with this while other guidance is dry across the lower elevations. A stronger ridge looks likely to develop Wednesday and persist through the end of next week, with good agreement on well above normal temperatures in this period.

AVIATION /00Z TAFS through 00Z Friday/

Issued at 606 PM MDT Wed Apr 2 2025

Gusty northwest winds will turn more north/northeast with another surge moving south across the metro airports 0030-0200Z (KDEN on the early side). Winds then gradually weaken and turn clockwise through 06Z, and then hold southerly at KDEN and KAPA (VRB at KBJC) through 12Z. VFR conditions will prevail through this period.

Snow will spread northward on Thursday, mostly likely affecting the TAF sites after 16-17Z. Ceilings will lower with the onset of precipitation, and with easterly flow we'll likely (>70% chance) transition to IFR through a combination of lower visibility and/or ceilings. We've lowered them accordingly. There is potential for visibility dropping to <1SM should a heavier shower/band move across, but this would be fairly short-lived. Despite a decrease in snow late tomorrow, we don't think ceilings will rise that much in continued light and moist easterly upslope flow. Snow may mix with rain in the afternoon due to relatively mild temperatures. That would also limit any snow accumulations and allow paved surfaces to stay melted.

BOU WATCHES/WARNINGS/ADVISORIES

None.