485
FXUS65 KBOU 081747
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1047 AM MST Fri Nov 8 2024

.KEY MESSAGES...

- An ongoing winter storm is generating significant snowfall
  across much of northeast and north central Colorado today into
  Saturday morning.

- Moderate to heavy snowfall is occurring across the east central
  Plains, and will spread north and east today, continuing
  overnight night. Very difficult and hazardous winter driving
  conditions are expected for much of northeast and north central
  Colorado, including the Urban Corridor.

&&

.UPDATE...
Issued at 948 AM MST Fri Nov 8 2024

Lots going on today. Latest radar trends have the heavy snow
moving westward across the I-25 corridor. Today`s forecast was
updated for the early arrival of heavy snow. Snow is accumulating
on the roadways across much of the area because of the heavy
rates, but still feel with a slight lull coming midday roads
should thaw before the evening rush hour other than across I-70
east of Denver. Speaking of the lull, radar is showing a dry slot
moving northwest out southeast Colorado, which should temporarily
reduce the snow rates for a few hours, maybe even shutting off
for an hour. This dry slot moves over Lincoln and Elbert Counties
in the next 2 hours, then I-25 corridor by midday-early
afternoon. However, don`t be fooled by this dry slot. All CAMs
show most of the area getting hammered with moderate to heavy snow
by mid/late afternoon, definitely impacting the evening rush
hour. Expect very poor driving conditions afternoon and evening,
all across the area within the Winter Storm Warning. Plan ahead
for any travel across northeast and north central Colorado,
especially east of the Divide and all the way to Kansas. The only
place across the Plains that for now still looks to miss out on
the snow is the northeast corner where it should remain as rain or
rain/snow mix with no significant accumulations. Amounts on the
West Slope will be light as well.

Advisories look good for Larimer-Weld-Morgan Counties for now,
despite the fact that it`s snowing pretty hard all across that
area. Roads are mostly wet along and north of US-34. We`ll need
to watch the afternoon push of heavy snow to see if it extends all
the way to Wyoming like this initial batch is right now, but for
now the plan is for advisory level impacts.

Snowfall amounts were tweaked a bit for the earlier moderate-heavy
snow, but only an inch or two added overall across metro Denver-
Boulder into Douglas County. Amounts elsewhere look okay for now,
and the heaviest snow totals exceeding 2-3` since Tuesday are on
track for the Palmer Divide east across Lincoln County, as well as
north to E. Arapaho and southern Washington Counties.

&&

.SHORT TERM /Through Tonight/...
Issued at 425 AM MST Fri Nov 8 2024

A decent snow event is still on track for northeast and north
central Colorado this afternoon through tonight.

Satellite pictures are showing the upper closed low circulation over
southwest/south central New Mexico at this time. Area radars are
currently showing an area of precipitation south and southeast of
the CWA, moving northward with echoes already getting into
southern Lincoln and southeastern Washington Counties.

Models maintain decent consistency with the track of the upper system
for the first two periods, with the upper low center tracking
northward right along the eastern Colorado border from 00Z
through 12Z tonight. So, the forecast is also on track, including
the warnings and advisories and snowfall amounts.

Models do, however, show an increase in QPF over the north
central CWA for this afternoon and evening. With that increased
QPF expected, we went ahead and extended Snow Advisories up into
zones 38 and 42 in addition to all the rest. Of note, the south
central and southeastern CWA could see 14 to 20 inches of snow by
Saturday morning.

There will be significant winter-weather travel impacts for much of
the forecast area by later this afternoon and especially this
evening and overnight. This includes the heavily populated Urban
Corridor.

&&

.LONG TERM /Saturday through Thursday/...
Issued at 425 AM MST Fri Nov 8 2024

Snow will be decreasing from west to east Saturday morning as the
low moves eastward. Warming temperatures and increasing NNW winds
bringing some downslope drying will also reduce snowfall rates and
impacts. There could still be some minor accumulations but impacts
should be going away. Of course, places with deep snow will
require time for road clearing.

There will be a brief period of mountain wave activity as the flow
goes northwest Saturday night. At this point it doesn`t look like
much of a high wind threat, but the higher mountains and wave
prone foothills spots will likely see a period with 40-60 mph
gusts.

Not much to say about the rest of the forecast as we`ll have
modest westerly flow aloft. There`s a shortwave in the
Tuesday/Wednesday period that models are struggling with. Stronger
solutions would be enough for mountain showers and perhaps a quick
band of showers moving across the plains but most solutions are
weaker and drier. Whatever cooling there is should be short lived
as westerly flow continues and should displace any cooler air
mass. NBM solution is adequate.

&&

.AVIATION /18Z TAFS through 18Z Saturday/...
Issued at 948 AM MST Fri Nov 8 2024

IFR and LIFR conditions into Saturday morning with periods of SN+.
There may be a brief lull in IFR sometime between 19-21Z when a
dry slot moves in from the southeast, but we haven`t included this
in the TAF just yet because it`s not clear if CIGs/VIS will get
above 1SM or 010. But the lull will be brief. We have high
confidence that around 23/00Z moderate to heavy snow will again settle
in for a while this evening into early Saturday. Don`t expect
much better than 1/2SM VIS and CIGs 004 throughout this evening
into early Saturday. Winds should remain under 12 kts throughout
the snow event, and mostly out of the north. Total snowfall
accumulations on runways will run 5-10" through Saturday morning
at all the terminals.

So when will CIG/VIS get better? After 12Z Saturday it looks
like. Light snow/no snow should be the norm especially by 15Z.
CAMs are hinting that light snow showers may occur between 18-21Z,
but for now just leaving a tempo in the TAF. Winds should shift
to southwest at under 10 kts after 21Z, and fingers crossed, VFR
conditions after that.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MST Saturday for COZ033>035-
038-042>044.

Winter Storm Warning until noon MST Saturday for COZ036-039>041-
045-049.

Winter Weather Advisory until 5 AM MST Saturday for COZ037.

Winter Storm Warning until 5 AM MST Saturday for COZ046-047.

&&

$$

UPDATE...Schlatter
SHORT TERM...RJK
LONG TERM....Gimmestad
AVIATION...Schlatter