Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 270346
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
846 PM MST Mon Feb 26 2024

.KEY MESSAGES...

- Windy and warm through the rest of the afternoon, with critical
  fire weather conditions for lower elevations.

- Significant travel impacts from snow, strong winds, and blowing
  snow will develop in the mountains this evening and continue
  through Tuesday evening.

- Much colder temperatures and windy for the plains Tuesday along
  with scattered light snow showers.

- Dry and warm conditions Thursday through Saturday.

- The next upper system to affect the CWA Sunday in poor model
  agreement.

&&

.UPDATE...
Issued at 818 PM MST Mon Feb 26 2024

Gusty west to southwest winds will continue through the night
across much of our forecast area. This will help to keep
temperatures elevated. In addition, the cold front will not move
through until the mid morning so low temperatures were raised 2-3
F tonight. The cold front passage should be between 13-16Z through
the plains. Given the strong frontogenesis from this front, there
will likely be a band or two of precipitation immediately behind
it. PoPs were raised in the 15-18Z timeframe across the plains to
indicate the best likelihood of precipitation occurring during
that time. When strong cold fronts like this come through, the
precipitation immediately following the front seems to "over-
produce." Therefore, it would not be surprising that a couple
areas, mainly on the north side of the Palmer Divide, pick up a
quick inch of snow tomorrow.

The other main focus in this update was to increase winds in the
Front Range mountains and foothills Tuesday night. Cross sections
show a very strong inversion at ridgetop level that will help
focus the winds in the higher foothills. High resolution model
guidance is beginning to show rather impressive wind speeds with
some gusts exceeding 90 mph. The forecast was updated to indicate
gusts up to 75 mph but a High Wind Warning may eventually be
needed for this period.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 225 PM MST Mon Feb 26 2024

An active weather pattern will continue through Tuesday.

Observations across the plains this afternoon show temperatures in
the upper 50s to upper 60s, with little moisture and lots of wind.
Dew points are currently in the single digits to mid 10s, with
gusts of 35-50 mph across a majority of the lower elevations...
which has led to a sustained period of critical fire weather
conditions. Conditions should improve later this evening as
humidity increases slightly and winds speeds slowly decrease.

Across the mountains, it`s been a fairly quiet day in between the
waves of snow. Water vapor satellite shows better moisture
approaching from the west, and snow should redevelop across the
high country later this afternoon or evening. The heaviest period
of snow looks to come late tonight into Tuesday morning as
moisture deepens and lapse rates increase. There may be one or two
strong frontal bands Tuesday morning that could further enhance
snowfall rates at times. The heavies snow should also fall during
a period of gusty winds... and while snowfall totals have
decreased somewhat compared to previous forecasts the combination
of snow and blowing snow will make travel very difficult at times
through Tuesday.

Meanwhile, the cold front will push across the plains Tuesday
morning, though this looks like it will come with more wind than
precipitation. Guidance has steadily backed away from the snowier
solutions, with low-level moisture lacking, while the near surface
flow maintains a westerly component. Can`t rule out some scattered
snow showers during the day, but accumulating snow chances look
much less likely. Our deterministic forecast lies on the bearish
side, though there is still some potential (<30%) for a quick
inch or two in any heavier, organized/persistent snow showers.
Temperatures will peak early in the day with highs in the upper
30s to low 40s, falling into the low to mid 30s by the late
afternoon.

.LONG TERM...(Tuesday night through Monday)
Issued at 225 PM MST Mon Feb 26 2024

Models have an upper trough move east of the CWA through Tuesday
night. Flat upper ridging is in place Wednesday and Wednesday
night. There is a weak upper trough, with most of the energy south
of the CWA Thursday, then zonal flow Thursday night. The synoptic
scale energy on the QG Omega fields is downward vertical velocity
or neutral through Thursday night.

For moisture, there is still some lingering around Tuesday evening,
especially in the high mountains. Will leave the Winter Storm
warning going until 11 PM MST late Tuesday evening.   QPF fields
show some measurable precipitation over the mountains Tuesday
night and a bit over the southeastern CWA Tuesday evening.
Wednesday and Thursday are pretty dry, with a bit of low level
moisture progged for the mountains Thursday night. No pops
Wednesday through Thursday night.

For temperatures, Wednesday`s highs warm up 9-13 C over Tuesday`s
highs and are right near seasonal normals.  Thursday`s high
temperatures look to be 2-5 C higher than Wedensday`s readings.

For the later days, Friday through Monday, the flow aloft becomes
southwesterly later in the day Thursday and that is progged to
continue into Saturday. Moisture moves into the CWA from the west
ahead of a decent sized upper trough that is over the Great Basin
at 12Z Sunday morning. Models all show upper troughing Sunday
into Monday for the CWA, but many of the specifics vary
considerably between the models. The trough should bring
precipitation to most of the forecast area Sunday into Monday, but
exactly where, when and how much is yet to be determined.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 529 PM MST Mon Feb 26 2024

VFR conditions today. Winds have begun to relax at all three
terminals this evening. Winds will stay at these levels with
sustained winds around 15 knots and gusts up to 30 knots at times
throughout the night.

A cold front will move across the terminals Tuesday morning.
Behind the front winds will shift to the north and then may shift
to the northeast. Gusts up to 30 knots are possible especially
when the front initially comes through. There is growing
confidence that low clouds and snow showers will develop in the
16-20Z timeframe. Ceilings could be as low as 2,000 feet and
visibility could reach as low as 1 mile under the heaviest snow
bands. During the mid afternoon, there is low confidence in wind
direction and speed as models are seemingly over-mixing the
northwesterly flow. While northwest winds appear most likely at
this point, northeast winds may continue through the afternoon.
Winds will turn westerly in the evening and will weaken.

&&

.FIRE WEATHER...
Issued at 225 PM MST Mon Feb 26 2024

Critical fire weather conditions have been observed across a
majority of the urban corridor and plains this afternoon, with a
few exceptions where RH hasn`t quite dropped to 14%. The
combination of dry conditions and winds gusting to 35-45 mph will
continue through the late afternoon, with conditions improving
near or after sunset. The current RFW timing looks fine and will
expire at 6 PM.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 11 PM MST Tuesday for COZ031-033-034.

&&

$$

UPDATE...Danielson
SHORT TERM.....Hiris
LONG TERM......RJK
AVIATION...Danielson
FIRE WEATHER...Hiris


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