Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 220617
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1217 AM MDT Fri Mar 22 2024

.KEY MESSAGES...

- Scattered light snow showers in the northern mountains this
  evening.

- Above normal temperatures Friday and Saturday.

- An upper trough moves in late Saturday into Tuesday with colder
  air and increased moisture. Alpine snowfall is expected, but
  not certain yet, if substantial amounts will accumulate. A
  decent plains snowfall does not look favorable at this time, but
  stay tuned.

&&

.UPDATE...
Issued at 828 PM MDT Thu Mar 21 2024

Scattered snow showers have moved into the mountains as expected,
but only spotty one half to one inch accumulations will occur as
they will be short-lived, and pretty much over or at least moved
south of the I-70 mountain corridor by midnight. With 7-8C/km mid
level lapse rates, can`t totally rule out a brief shower or
sprinkle in the lower elevations - but mostly gusty
outflow/enhanced downslope winds expected with the deep, dry
sub-cloud layer.

At the surface, a cold front was moving through southeast Wyoming
and the Nebraska panhandle, recently passing Chugwater, WY and
Scottsbluff, NE. That front and northerly wind shift is a bit
ahead of schedule and will push through Denver shortly after
midnight. Gusty winds will then gradually decrease behind the
front, and skies will clear overnight. Main adjustments this
evening were for gustier winds before the front and slightly
earlier frontal passage/wind shift. Also nudged down high
temperatures tomorrow over the northeast corner where front will
have more cooling power. Denver still looks nice and mild with
lower 60s for highs and a good amount of sunshine.

&&

.SHORT TERM...(This evening through Friday)
Issued at 129 PM MDT Thu Mar 21 2024

A shortwave will move quickly across Colorado tonight. There are
some light shower bands over northern Utah that will make it into
our mountains this evening. It`s probably not enough to produce
showers reaching the ground over eastern Colorado, but an isolated
light shower isn`t out of the question. The lift will come and go
quickly, just a couple of hours, though there could be a little
lingering mid level moisture over areas west of the Front Range
overnight. On the plains, we`ll see a northerly wind shift in the
late evening. The warmest air will get shoved southward, but the
coldest air will stay north of us. There may be just enough
cooling to generate a high stratus layer over the northeast plains
in the late night and morning hours before drying/warming
subsidence erodes it.

For Friday temperatures should rebound nicely with sunshine. At
first glance, it`s hard to believe there`s not more cooling with
post-frontal east winds, but there`s really only about 10 degrees
of cooling at the surface and 5-10 F aloft and that will be
warming again by Friday afternoon. We`ll stick with the current
forecast of 5-10 degrees cooler (less warm?) on the plains with
little change in the mountains.

.LONG TERM...(Friday night through Thursday)
Issued at 129 PM MDT Thu Mar 21 2024

There will be a few chances for some Spring snowfall through the
extended forecast period. The first will be associated with a trough
currently on an eastward track towards the west coast. This trough
will move into the PNW Friday and pass through the Intermountain
West over the weekend. Guidance remains consistent with regards to
the current pattern and for accumulating mountain snowfall, but
uncertainties remain for what will be seen across the plains.

For the mountains, the approaching trough will advect Pacific
moisture into Colorado. This moisture mixed with steep mid level
lapse rates, frontogenesis, and orographics will be sufficient to
bring accumulating snow and possibly even some thunder beginning
Saturday night. Unlike last week`s moisture laden, slow moving
storm, this one will have far less moisture to wring out and move
through more swiftly. These factors will help limit any real
significant accumulations. Ensembles show QPF totals ranging from
less than half an inch on the low end (Canadian) to 0.7 on the high
end (GFS) for some mountain passes. With the steep lapse rates in
place, there is some potential for snow squall conditions to develop
Sunday afternoon that could cause poor visibility in localized
areas. Travel conditions will likely be slick across the I-70
mountain corridor during Sunday evening ski traffic and into
Monday morning that may require some highlights in the coming
days.

For the plains, the ensembles agree there will be precipitation,
however, there are some lingering uncertainties as far as when rain
will turn to snow. A cold front will pass through Saturday night
into Sunday, mixed with frontogenesis, this will be sufficient
forcing to see precipitation develop across the plains Sunday
morning. A chance for thunderstorms can`t be ruled out with enough
instability present overnight. This will likely remain rain until
temperatures dip low enough Sunday evening/overnight to
transition to snow. High temperatures on Sunday may be tricky with
the frontal passage. We dropped them a few degrees across the
plains from what was in the previous forecast, but timing of the
frontal passage may impact these, which could then impact when the
precipitation transition takes place. Models are showing a
northerly flow that will favor drier/warmer conditions to areas
south of the Cheyenne Ridge and wetter conditions for the Palmer
Divide. QPF supports this with higher values shown for the Palmer.
Slick travel conditions may develop over the Palmer Divide and
into the Denver metro Sunday night, and may persist through the
Monday morning commute. There is a chance for blowing snow across
the plains with gusty winds expected that may also lower
visibilities causing hazardous travel conditions. Some highlights
may be issued in the coming days to address this.

There will be sufficient Pacific moisture present and
southwesterly/westerly flow through the rest of the forecast period
to allow for light mountain snow possibilities. The active weather
pattern will continue with a more significant system likely to
move in around Thursday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1215 AM MDT Fri Mar 22 2024

A wind shift is pushing southwestward across DIA at this time.
Fairly strong north-northeasterly winds can be expected with
gusts to about 30 knots for next hour or so. Most of the models
have weak downsloping after that and something close to weak
drainage flow by 12Z this morning. Models show northwesterly winds
at DIA later this afternoon. There should not be any ceiling
issues.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE.......Barjenbruch
SHORT TERM...Gimmestad
LONG TERM....Bonner
AVIATION.....RJK


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