Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 041624
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
924 AM MST Mon Mar 4 2024

.KEY MESSAGES...

- Snow showers continue in the mountains through this evening, but
  gradually decrease especially in the I-70 corridor. Still some
  travel impacts mainly northern tier of mountains through
  tonight.

- There will be a daily chance of snow in the mountains during the
  work week. The heaviest mountain snowfall will fall on Thursday
  and Friday.

- Precipitation is likely across the plains late on Thursday and
  into Friday. The most likely scenario is that light
  precipitation occurs although there remains a chance that
  moderate to heavy precipitation could occur with this system.

&&

.UPDATE...
Issued at 924 AM MST Mon Mar 4 2024

Latest cameras and satellite indicate some breaks in the clouds
and snow showers in Summit County and the I-70 mountain corridor.
Thus, we`ve allowed the Winter Storm Warning to expire there.
However, accumulating snow was still occurring in the northern
tier of mountains including Rabbit Ears Pass and Medicine Bow
Range. There is one more wave of moisture and forcing that will
arrive in those areas this afternoon, currently pushing eastward
across northern Utah. That wave is associated with one last speed
max rotating through the Northern Rockies trough axis. Given
those trends, we`ve opted to downgrade the existing Winter Storm
Warning for the northern tier of mountains from Rabbit Ears Pass
to RMNP to Winter Weather Advisories, but at the same time extend
it until midnight tonight to handle the expected hazardous winter
travel conditions and additional snow/blowing snow impacts.

A few showers may even spread onto the plains once again this
afternoon and evening as mid level frontogenesis strengthens yet
again with this passing disturbance/jet max to our north. Nothing
more than a brief dusting expected near the Wyoming border.

Overall, mostly minor changes to the existing forecast, except
boosted PoPs in the northern mountains through this evening for
the passing disturbance and forcing.

&&

.SHORT TERM...(Today and tonight)
Issued at 341 AM MST Mon Mar 4 2024

Current upper air analysis shows a 500mb trough across Colorado
this morning with enhanced SW flow aloft. Although not as
pronounced as hours ago, there is still weak 700mb frontogenesis
across the region. Mainly this has been supporting a weak, very
narrow snow band extending SW-NE as far as NE Weld County early
this AM. Some struggle to get snow to the ground in most spots;
however, Greeley reported light snow earlier. This band will
continue to fall apart into the morning hours.

Snow continues in the mountains this morning with showers
with sufficient lapse rates to support showers in the afternoon as
well. The upper level jet will shift north this afternoon/early
evening bringing the better support for ascent with it. This will
slowly decrease showers from south to north across the high country
into this evening. As the better ascent slides north, a few showers
may stray onto the adjacent plains, but drier low levels should
limit this overall. A Winter Storm Warning remains in effect through
9 AM this morning for the mountains. The highest impacts will be
over; however, minor impacts to travel are still expected today. It
will be breezy in the mountains, especially over the mountain
passes, so areas of blowing snow will remain an issue given the
fresh snowfall. Subsident flow fully moves in Monday night
diminishing any lingering showers. For the plains today, highs will
be a few degrees cooler than yesterday behind last evening`s front.
Relative humidity is improved with values in the 20 percent range
across the plains as opposed to the teens from the last few days.
Lighter winds expected today across the plains, with a Denver
cyclone wind pattern setting up in the afternoon.

.LONG TERM...(Tuesday through Sunday)
Issued at 341 AM MST Mon Mar 4 2024

Moderate west-southwesterly flow will be over Colorado Tuesday and
Wednesday. Since there won`t be any shortwaves within this flow,
there will generally be subsident conditions which will keep the
plains dry. The only exception to this will be Tuesday night when
700 mb frontogenesis moves across the Palmer Ridge with a few
light showers possible along it. In the mountains, daytime
heating will lead to steep low level lapse rates in the afternoon.
The instability generated from this will allow for convective
snow showers to form especially on Wednesday. Snow amounts will
not be much to write home about but some locations could pick up
as much as 2 or 3 inches each day. However, most locations will
receive much less snow. Travel may be briefly impacted during some
of the heavier afternoon snow showers in the mountains.

It finally feels like the models have some agreement during the
Thursday and Friday system. There will be a series of shortwave
troughs aloft that move near or over Colorado. Perhaps the more
important aspect will be the low level winds. A cold front will
push across our forecast area Wednesday night that will bring
northeasterly winds behind it. These northeasterly winds will
persist throughout Thursday and into Friday. As a result, there
will be upslope flow across much of northeast Colorado but
especially along the Palmer Divide and southern foothills.
Precipitation will be likely and PoPs in the 60-70% range are in
the forecast for those locations. Global ensembles are clustered
around a solution where the plains receive light precipitation,
generally in the 0.1-0.3" QPF range. However, all global ensembles
have a few members that are producing over an inch of QPF across
the plains. So this "high end" solution is still viable and the
forecast will need to be monitored over the next few days for the
potential for a moderate or high impact event. For the Front
Range mountains, there will be convergent low level flow that will
lead to light to moderate snowfall during this period. Snow
amounts appear they will most likely be in the Winter Weather
Advisory criteria range. Travel will be impacted in the mountains
and foothills during this system.

By late Saturday into Sunday, a ridge will move over Colorado
which will bring dry conditions and warming temperatures. The next
period the ensembles highlight for precipitation is March 14-16.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 454 AM MST Mon Mar 4 2024

SSE winds this morning at 07-12 kts. A band of clouds has reached
BJC this morning, bringing in BKN ceilings around 060. It is
slowly dipping south. It may brush DEN bringing in a period of
SCT to BKN ceilings at 060-100 this morning. Winds will be a
challenge today at the terminals thanks to development of a
Denver cyclone circulation in the afternoon. There is higher
confidence that winds will increase late morning/early afternoon
out of the SE at 08-12 kts. Can`t rule out a gust 18-20 kts. The
cyclonic wind pattern sets up in the afternoon and where it sets
up and progresses will dictate the winds. There isn`t strong
agreement among models on where it tracks, thus lower confidence
in the wind direction. Expressing the transition to a more NW
component at BJC/APA west of the circulation while DEN may be more
NE/E component. Again, this will mainly be based on set-up
location of the circulation. Winds become lighter SE late evening
into early Tuesday morning.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MST tonight for COZ031-
033.

&&

$$

UPDATE...Barjenbruch
SHORT TERM...Mensch
LONG TERM...Danielson
AVIATION...Mensch


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