741
FXUS65 KBOU 190032
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
632 PM MDT Fri Apr 18 2025

.KEY MESSAGES...

- Hazardous mountain roads through Saturday morning with ongoing
  moderate snow.

- Steady snow through this evening for the urban corridor,
  diminishing overnight, with bulk of accumulations limited to
  colder surfaces.

- Warmer pattern Sunday into next week, with a chance of
  afternoon/evening showers most days.

&&

.UPDATE...
Issued at 621 PM MDT Fri Apr 18 2025

Boulder, Jefferson, and Douglas Counties all have moderate snow
with decently high reflectivity shown on radar. These areas may
pick up a quick 2-3" of additional accumulation on grassy surfaces
with higher amounts possible in the foothills given the colder
temperatures and better snow ratios there. Travel in the
foothills and mountains will only deteriorate this evening as any
snowless roads may see accumulation. The Palmer Divide and areas
in the western Denver metro may also see icy/slushy roads that
could lead to poor travel conditions. People traveling in those
locations will need to be cautious. Elsewhere, roads are quite
warm and the snow will not be heavy enough to cause much of a
concern. The forecast is still on track for snow to continue
through the evening before tapering off overnight.

&&

.SHORT TERM /Through Saturday/...
Issued at 228 PM MDT Fri Apr 18 2025

Deepening moisture and a slight enhancement of the upslope component
in the low-level winds will support continued snow across the
high country, foothills and urban corridor, gaining some intensity
and persistence this afternoon and evening. Despite ambient
temperatures near or below freezing around the Denver metro,
pavement temperatures remain markedly warm at this hour courtesy
of the April sun, effective even with the cloud cover. With
increased snowfall rates and roadway temperatures anticipated to
drop near freezing between 5-8pm, some slushy accumulations will
become possible for the urban corridor this evening, primarily
west of I-25 where snow will be heaviest/most persistent. Thus,
minor impacts to the very tail end of the commute will be
possible, but there just isn`t enough road temperature, snowfall
intensity, and snowfall duration alignment to necessitate any
expansion of current headlines. The extent of travel impacts is
similarly questionable for the Palmer Divide, but there`s enough
potential for snow to drag on longer into the evening for us to
retain the Advisory and see how things play out. In the high
country, the focus for the heaviest snow will focus along and
south of I-70, especially in and around Park County, with
hazardous road conditions expected to extend into Saturday.

That being said, one consideration for the overnight period will
be the freezing of road surfaces as snow gradually diminishes and
temperatures fall below into the 20`s, making roads slick early
Saturday. Patchy fog can`t be ruled out either for the lower
elevations in the morning.

For Saturday, we`ll see modest warming into the 50`s for the
plains/urban corridor (low 50`s in the northeast corner), and
mostly 30`s for our mountain communities. Southeasterly low-level
flow combined with lingering mid-level moisture will sustain
scattered snow showers in the mountains, again favoring I-70
southward, whereas most other areas will be mostly dry past
midday. Cloud cover will be slower to clear however.

&&

.LONG TERM /Saturday night through Friday/...
Issued at 228 PM MDT Fri Apr 18 2025

Saturday night, an upper level trough of low pressure will be over
the Rocky Mountain Region with a closed upper low tracking across
New Mexico. Cross sections show diminished upslope flow east of the
mountains which should result in mostly dry weather across the
plains. The high country could see scattered snow showers overnight
due to some weak orographic lift combined with QG lift from a
passing shortwave.

Warmer and drier weather is expected on Sunday as the upper trough
moves into the Central Plains States and a weak upper ridge builds
over Colorado.

Early next week, a zonal flow aloft sets up over the state with mild
and dry weather across the plains, with temperatures climbing into
the lower to mid 70s. Across the high country, there should be
enough available moisture combined with some orographic lift to
produce isolated to scattered rain and snow showers. On Monday, the
flow aloft will be the strongest which will produce breezy
conditions across the higher mountains and foothills. In addition,
the plains could also see gusty winds due to a downsloping flow. The
gusty winds combined with low relative humidity will lead to
increasing fire danger during the afternoon hours.

For the Wednesday night through Friday period, the upper flow turns
southwesterly in response to an upper level trough deepening along
the west coast of the U.S. At the surface, the gradient between
higher pressure over the Central U.S. and lower pressure over
Colorado should allow east to southeasterly winds to advect higher
moisture onto the plains. This moisture combined with daytime
heating may lead to a better chance for afternoon and early
evening showers and storms through this period.

&&

.AVIATION /00Z TAFS through 00Z Sunday/...
Issued at 605 PM MDT Fri Apr 18 2025

Snow will continue through around 03Z this evening at all
terminals. When a heavier band is overhead, visibility will likely
be between 1-2SM with ceilings around 500-1,000 feet. Otherwise,
visibility may be around 4-7SM with ceilings around 2,000-3,000
feet. Some lingering snow showers will continue after 03Z but
visibility will not be impacted as much. The concern tonight is
the threat for fog. With a lot of moisture in the area and melting
snow, any clearing in the ceilings could lead to fog development.
However, there will likely be southeast winds for much of the
night. Southeast winds are usually not favorable for fog
development. Therefore, VCFG was kept in the TAF for DEN and BJC.
There is a higher likelihood of fog at BJC. Low ceilings will
break around midday tomorrow and VFR conditions will return.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM MDT Saturday for COZ033>037-
041.

&&

$$

UPDATE...Danielson
SHORT TERM...Rodriguez
LONG TERM...JK
AVIATION...Danielson

NWS BOU Office Area Forecast Discussion