Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 231637
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1037 AM MDT Sat Mar 23 2024

.KEY MESSAGES...

- A weather system will affect the area Sunday through early
  Monday morning. This system may bring heavier snowfall to
  portions of the mountains, southern foothills and Palmer Divide
  Sunday night. However, confidence in exact details still remain
  low at this time.

- Snow shower activity will continue in the mountains Tuesday and
  Wednesday with mainly dry conditions over the plains.

&&

.UPDATE...
Issued at 1030 AM MDT Sat Mar 23 2024

A few minor adjustments were made to the forecast. The first was
to decrease high temperatures across the far northeast corner of
Colorado as low clouds and southeast winds are keeping
temperatures down there. Highs should stay in the 50s instead of
reaching the 60s. The second change was to lower PoPs across the
plains late tonight and into Sunday morning. There is a brief dry
slot that moves over our forecast area during that time which
should lead to a dry period especially for the plains.

&&

.SHORT TERM...(Today and tonight)
Issued at 340 AM MDT Sat Mar 23 2024

Area radars are showing a few alpine snow showers pushing
east-northwestly at this time, but pretty sparse. There is a Denver
cyclone going right now.  The center is a bit north of DIA.

Models have an upper ridge push eastward across the CWA today. There
will be southwesterly flow aloft developing later this evening and
overnight.  There is weak upward vertical velocity over the forecast
today and tonight on the QG Omega fields. The low levels will be
dominated by southwesterly downsloping today.  The thickness fields
show warm air advection for much of the CWA today.  There is minor
CAPE over the western two-thirds of the CWA this afternoon. Lapse
rates are fairly steep. So I went with 10-25% pops for the plains
this afternoon/evening. I doubt there will be much rain hitting the
ground.  In the mountains, I decreased the pops today. There is too
much warm air advection with the upper ridge and not great low level
moisture, especially later this afternoon.  Also, southwesterly flow
at mountains top level is not great for orographics in our
mountains.  I left the higher mountains pops in tonight with the
upper system nearing.  Temperatures will be warm over the plains
this afternoon, a good 10 degrees F above normal.

.LONG TERM...(Sunday through Friday)
Issued at 323 AM MDT Sat Mar 23 2024

An upper level trough will be over the Great Basin on 12z Sun. This
system will then move eastward thru the day with a closed low
eventually developing over ern CO by early Sun evening.  This low
will then eject rapidly northeast and be over central NE by late
Sun night.

As this system moves across there will be favorable QG ascent along
with decent lapse rates. For the mtns, should see an increase in snow
thru the day with the heaviest amounts from the aftn into the
evening hours. At lower elevations, a cold front will move across
the plains in the aftn with gusty north winds behind it. MLCAPE is
fcst to be around 500 j/kg over the plains so will likely see
aftn tstms in addition to increasing shower activity.

By late aftn into the early evening hours, should see a quick
changeover to snow across most of the plains/Palmer Divide as colder
air surges into the area.

As far as qpf/snowfall amounts, the ECMWF has been the most
consistent the last 3 to 4 runs while the GFS has been going back
and forth with overall amounts.  Ensemble mean data from the ECWMF
has matched up well with its operational runs while the GFS
Ensemble mean has been more like the operational ECMWF and
Ensemble mean.

At this time, I still think there is some potential for heavier snow
in the srn Foothills and across the Palmer Divide Sun night.  Across
most of the mtns, snow amounts will probably stay mainly blo 12",
however, could see some heavier snowfall in some areas but not sure
how widespread it will be.  Below 6000 feet, will keep amounts
around the Denver metro in the 2-4 inch range, although the far wrn
and srn suburbs could see up to 6 inches.  Elsewhere across the
plains will keep amounts around an inch or so.  Gusty winds will
continue Sunday night so will also have blowing snow and poor
visibility, especially over the Palmer Divide.

By Mon, NW flow aloft will be over the area.  Lingering moisture in
the mtns will lead to some light orographic snowfall.  Across the
plains it will be mainly dry with colder temperatures as highs will
range from the 30`s to lower 40s.

For Mon night thru Tue, NW flow aloft will remain over the area.
Moisture embedded in the flow combined with favorable lapse rates
will allow for periods of orographic snow in the mtns.  Across the
plains it will remain mainly dry, although can`t rule out a
slight chance of showers Tue aftn/evening. Highs will be in the
40`s over the plains.

On Wed, will begin to see an upper level ridge slowly build into the
area.  Moisture will begin to decrease in the mtns so should see a
less snow shower activity.  Across the plains, it will be dry with
seasonal temperatures.

For Thu/Fri, there is still a lot of uncertainty on the overall
pattern.  Latest data, has an upper level trough moving across the
nrn Rockies late Thu into Fri with nrn CO on the southern extent of
this system.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday night) Issued
at 340 AM MDT Sat Mar 23 2024

Winds have gone to a near due westerly direction at DIA as the
models indicated they would, earlier. Models keep weak
southwesterly winds going much of today at DIA. Some of them
show southeasterlies around 00Z later this afternoon. Will put a
"VCSH" in the TAF this afternoon with a minor convection
potential. Later updates might include a TEMPO group for stronger
outflow winds. There shouldn`t be any ceiling issues.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to 6 AM MDT Monday
for COZ031-033-034.

&&

$$

UPDATE...Danielson
SHORT TERM...RJK
LONG TERM....RPK
AVIATION.....RJK


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