Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 280535
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1135 PM MDT Wed Mar 27 2024

.KEY MESSAGES...

- Accumulating snow across the Park Range/Rabbit Ears Pass
  Thursday night with mainly lighter accumulations across the
  remainder of the Northern Mountains. Occasional snow showers in
  the mountains and scattered showers for the northern plains
  Friday through Saturday.

- Mountain snow, with a mix of rain and snow likely for the
  plains, late Sunday into Monday. Mostly light but there could be
  some impact for the mountains and foothills.

&&

.UPDATE...
Issued at 808 PM MDT Wed Mar 27 2024

Radar, satellite, and webcams indicate snow showers have ended
over the mountains. The convective cloud cover that formed over
the plains is dissipating with mostly clear skies expected for a
good part of the night. Highs do begin to increase after midnight.
Going forecast on track with no changes planned.

&&

.SHORT TERM /Through Thursday/...
Issued at 224 PM MDT Wed Mar 27 2024

Current radar shows snow showers over the mountains this
afternoon. Some marginal instability has allowed shower
development over northern Weld County across the northeast plains.
Not a whole lot coming out of those showers on the plains with
wide enough temperature-dewpoint spreads. For the remainder of the
afternoon, expect showers to continue over the mountains with very
light accumulations (an inch or two at most). A few showers may
drift onto the plains, but dry air will work against any liquid
accumulation. A broad upper ridge moves in this evening, shutting
off any lingering showers.

Overnight, cross-barrier flow increases to around 30-40 kts.
Model cross sections show indications of a stable layer developing
overnight. Mountain wave enhancement will bring gusty winds to the
mountains and favored higher foothills areas overnight and into
Thursday. Generally seeing gusts 40-50 mph, but a few gusts up to
60 mph are possible in the wind prone, exposed areas. Temperatures
warm further aloft for Thursday. This should bring highs in the
60s to most of the plains. Urban corridor nearing 60. Higher level
mountain wave clouds may inhibit temperatures from warming as
high as they could. It will be fairly dry in spots across the east
plains with elevated fire weather conditions for Lincoln County
and some spotty critical conditions possible. Late afternoon, a
weak shortwave approaches. This will bring the first wave of weak
ascent and average- slightly above average moisture to the high
country. Snow showers will increase slowly from west to east
across the mountains late Thursday afternoon into the early
evening timeframe.

&&

.LONG TERM /Thursday night through Wednesday/...
Issued at 224 PM MDT Wed Mar 27 2024

Thursday night through Saturday, an upper level storm system will
deepen off the coast of Central California with a moderate to strong
west southwesterly flow aloft over Colorado. This pattern should
bring periods of snow to the high country with mostly dry conditions
on the plains. Snowfall rates should be generally light due to poor
southwesterly orographic flow with the exception of the Park Range
where higher snowfall rates are expected. However, with a 100KT
upper jet in the vicinity, can`t rule out a couple of localized
heavier bands across the remainder of the North Central Mountains.
The models are suggesting the heaviest snow across the Park Range
from Thursday evening until about midnight with the snow shifting
towards the I-70 Corridor Friday morning as the upper jet sags
south. At this time, it looks like an Winter Weather Advisory may be
needed for zone 31. Snowfall rates could again increase across the
mountains mainly north of US-40 Friday evening as another 100KT
upper jet moves into Northern Colorado.

East of the mountains, there could be scattered (30-50%) showers
across the northern sections of the plains late Friday afternoon
into Saturday morning as some of the moisture spills over the
mountains and a weak surge of cooler air moves in from the
northeast.

Snow should continue across the Northern Mountains Sunday and Monday
as the upper trough shifts eastward into the Central and Southern
Rockies. Once again, snowfall rates will generally be light
(excluding the Park Range) due to an unfavorable orographic
southwesterly flow aloft with the potential for heavier bands
associated with a nearby 130Kt upper jet.

The plains should see mild and mostly dry conditions on Sunday with
20% to 40% chance for showers along with a few thunderstorms by late
afternoon. Precipitation should increase across the Foothills, Front
Range Urban Corridor, plains and Palmer Divide Sunday evening as
lift from the strong upper jet interacts with a cold front moving
south across the plains. Due to the somewhat warm airmass, the
precipitation should change over to snow in the foothills during the
evening and stay mostly rain across the plains overnight. The rain
could change over to snow across the Palmer Divide as well as the
northern sections of the plains by early morning Monday. There is
still quite a bit of uncertainty in QPF and snowfall amounts east of
the mountains due to a variety of factors. The first factor is how
much upslope flow do we get behind the passage of the cold front.
Some of the models are showing a due northerly flow which would
favor the Palmer Divide with some local downsloping flow which could
limit QPF just east of the foothills from north of Denver to the
Wyoming Border. If the flow turns more northeasterly, the foothills
and Front Range Urban Corridor could see higher QPF/snowfall
amounts. Another factor would be the timing of the front and the
amount of cold air behind it which could have notable implications
on snowfall amounts. A third factor would be how the upper level
pattern develops as it moves east of the mountains. If the upper low
closes off over far Northeastern Colorado as the 12Z GFS
Deterministic solution suggests, the far northeastern sections of
the plains could see a period of accumulating snow and gusty
northerly winds Monday afternoon. For now it looks like most places
east of the mountains should see measurable precipitation with the
highest amounts most likely over the from the foothills/Front Range
Urban Corridor northeast across the plains. As for snow, the
foothills most likely will see at least a few inches of snow with a
couple inches over the Palmer Divide and northern sections of the
plains. We`ll have to keep a close eye on this system as it is March
and things can change.

Dry and warmer weather is expected to return by Tuesday as upper
level high pressure builds over the Rocky Mountain Region.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1133 PM MDT Wed Mar 27 2024

VFR conditions thru the period. South winds overnight will
continue thru Thursday morning. By early aftn they should
become more WSW and then westerly by 23z.

&&

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

&&

$$

UPDATE...Meier
SHORT TERM...Mensch
LONG TERM...JK
AVIATION...RPK


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