Sunrise 6:14 AM   Sunset 7:43 PM Moonrise 2:51 PM   Moonset 3:34 AM

  Print   HELP   Reset   Save   Recall

FXUS65 KBOU 191155 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 555 AM MDT Fri Apr 19 2024

KEY MESSAGES

- Springtime snow in the Rockies, with accumulations expected in most locations tonight through Saturday morning. Patchy drizzle/freezing drizzle to start the day

- Slick and hazardous travel in the foothills, and possibly onto the adjacent plains into Saturday morning

- Cold through Saturday, then drier and warmer for Sunday through much of next week.

SHORT TERM /Through tonight/
Issued at 1257 AM MDT Fri Apr 19 2024

Plenty of low cloud cover in northeast Colorado this morning. Radar shows a bit of a different picture than it did late last evening with a fairly organized band of snow extending from the foothills of Boulder County eastward onto the plains. There isn't high certainty on how long this band remains organized, but most model guidance doesn't keep it around too long this morning. A few showers will be possible for the remainder of this morning across the east slope and adjacent plains. Temperatures in the urban corridor are a little above freezing. If it were a tad colder at the surface, freezing drizzle would be more of a threat this morning given the low stratus. With light snow in parts of the foothills and cooler temperatures overall, there may be some slick spots out there this morning.

Plenty of small yet challenging elements in the forecast today and tonight. Colorado will be under zonal flow aloft with a quick shortwave trough moving across into Saturday. This morning, there is a good amount of moisture in place with the low stratus to prove it. The first question will be if and how long these low clouds stick around. For most areas, it is becoming more likely that the stratus sticks around today with some subtle thinning or rising in the afternoon. Areas south of I-70 have a better chance at some breaks in the deck. With that said, cloud cover and a cooler airmass will keep highs cool today. Had to do some manual adjusting to the highs as most guidance was too warm. Highs will likely remain in the low 40s across the plains.

Late this afternoon through Saturday morning will be the most "weather-active" timeframe. As the next wave approaches, better ascent and moisture moves into the area. Snow showers develop in the mountains this afternoon. A front will move across the plains in the late afternoon-early evening timeframe bringing a push of NE upslope winds and additional cold air advection. This will help develop showers across the lower elevations. This will start as rain.
Early evening, as temperatures cool, snow will begin to mix in and change to snow. Had to wrestle a bit with the snow levels to paint the right picture. There is a low chance for some freezing drizzle early PM on the plains. Moisture should be deep enough to combat this however.

The jet will play a role in this event as it will support more organized banding across the eastern slope mountains and plains Friday night into Saturday. However, the downfall of bands is the lower confidence in exact placement and more localized totals.
This isn't looking like a high-impact event. Can't rule out a few localized bands with more moderate rates (0.5-1"/hour). Generally, bands will move northward across the I-25 corridor, and east slope overnight while also spreading eastward onto the plains.
Ensemble means are still consistent with moderate to high probabilities 40-80% for 1-3" for the adjacent plains. As you go further eastward, confidence decreases in exact amounts and this is due to the localized nature of the banding. The east slopes of the Front Range and the foothills will be most favored with amounts in the 4-10 inch range. As a result, a Winter Weather Advisory has been issued for the mentioned areas along the Front Range mountains/foothills.

LONG TERM /Saturday through Thursday/
Issued at 230 AM MDT Fri Apr 19 2024

Snow will be ongoing Saturday morning over much of the Front Range Mountains, Foothills, and Plains. However, the best lift in the form of the right entrance region of the upper jet, QG, and mid level frontogenesis will be weakening. Thus, snow will start to taper off once we hit mid morning with a further decrease in most areas through the afternoon. Another inch or so of accumulation is expected before tapering off in the mid to late morning hours. There will be some convective redevelopment in and near the mountains in the afternoon due to mid level instability, but additional accumulation with those will be minimized by daytime "heating". Heating is a loose term, as high temperatures even on the plains will be struggling to reach the lower 40s given some fresh snow on the ground, persistent low clouds, and shallow upslope.

Now, if you're looking for nice weather, you don't have to look any further than Sunday. Westerly flow develops which will lead to warm advection, a return of sunshine, and downslope warming.
Thus, we expect high temperatures to push back into the mid to upper 60s. Further warming is likely to occur Monday with good ensemble agreement that we'll reach the 70s across the plains, although a cold front potentially reaches us earlier shaving a few degrees off those numbers.

That late Monday cooling will last into Tuesday, but then warmer temperatures will re-establish themselves for Wednesday into Thursday in advance of the next storm system. That storm system's arrival is expected to bring a return of unsettled weather toward Friday with scattered showers and storms, and some mountain snowfall along with cooler temperatures.

AVIATION /12Z TAFS through 12Z Saturday/
Issued at 555 AM MDT Fri Apr 19 2024

Ceiling and weather impacts are expected to continue through the TAF period.

A batch of light snow showers has made it across BJC and DEN within the last hour or so this morning. A few VCSH are possible this morning, but will be a low chance. Expect small improvements in the ceilings this morning into the early afternoon. This will put them in the upper MVFR to low VFR category (at best). A Denver cyclone wind pattern will dominate the wind direction today with winds turning to the northwest this morning then more northerly for the afternoon.

A front moves across Colorado in the late afternoon-early evening timeframe (20-00Z) followed by a push of northeast winds. Showers develop around the terminals mid to late afternoon with lowering ceilings. Early evening snow will likely begin to mix in and changeover. With light snow, conditions drop back into low MVFR to IFR with lower visiblities and ceilings. Briefs drops to 1/2SM are possible in some snow bands. This will continue overnight with lingering showers Saturday morning.



BOU WATCHES/WARNINGS/ADVISORIES
Winter Weather Advisory from 6 PM this evening to 9 AM MDT Saturday for COZ033>036.

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Denver/Boulder, CO,