395
FXUS65 KBOU 280629
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1229 AM MDT Sun Apr 28 2024

.KEY MESSAGES...

- Warmer and drier conditions to start the week, turning to
  cooler and wetter conditions as another storm system moves in
  later in the week

&&

.UPDATE...
Issued at 911 PM MDT Sat Apr 27 2024

Radar shows bands of showers across the Front Range, urban
corridor, and plains.. This will continue to produce light snow
for the Front Range mountains and foothills. Mainly rain showers
for the lower elevations, but can`t rule out snow mixing in at
times across the urban corridor. The Palmer Divide will be more
favorable for light snow showers. This system will continue to
decrease in coverage and intensity tonight with lingering showers
tomorrow morning. This appears on track for the expiration of the
Winter Storm Warning for the Front Range mountains and the winter
weather advisory for southern Park County. With snow decreasing in
intensity in the foothills, the Winter Storm Warning there may be
able to be let go earlier than 12z tomorrow. As the last cohesive
wave goes through the Palmer Divide, decided to keep the Advisory
going, although it could likely be let go before midnight as
accumulations/impacts appear minimal.

&&

.SHORT TERM /Through Sunday/...
Issued at 230 PM MDT Sat Apr 27 2024

Satellite pictures are showing the upper low center now over
northwestern New Mexico.  Area radars are indicating, mostly light
Stratiform precipitation falling over the Divide mountains, foothills
and western half of the plains. The snow level is about 5,500 MSL
right now.

The models move the upper low center northeastward across the CWA
overnight to about the southwestern Nebraska at 12Z Sunday morning,
then to north central Nebraska by 00Z late Sunday afternoon.  Cross
sections show pretty deep moisture in place over the forecast area
all night.  The northwesterly downsloping winds behind the upper low
center get into the CWA 09-12Z Sunday morning.   I will keep the
pops high through around midnight tonight, then start to decrease
them, especially east of the mountains where the downsloping will
further dry things out.  With thickness grids in mind, the snow
level will be from 5,500-6,000 MSL overnight.  Not expected much
accumulation over the plains overnight.  Will leave the highlights
going for the high County and Palmer Ridge as is for through 06Z
night.  Additional accumulations will drop off by mid evening. For
temperatures, tonight`s lows should stay in the lower to mid 30s F
for the plains, 20s F in the foothills and teens & 20s F in the
mountains.

&&

.LONG TERM /Sunday night through Saturday/...
Issued at 213 PM MDT Sat Apr 27 2024

As the upper level low exits Colorado, westerly flow aloft will
transition to northwesterly as weak ridging builds in overnight
Sunday. By Monday morning, cross sections indicate a mountain wave
signature that will aid in bringing drier conditions to the lee side
of the Front Range Mountains for Monday. A jet associated with a
passing disturbance to the north will also help dry things out as
northern CO resides in the subsident zone of its right exit region.
High temperatures for the day will be in the low 70s across the
plains and foothills and 50s across the mountains, which will be
below normal for the higher elevations and above normal for the
eastern plains. The aforementioned disturbance to the north will
shift eastwards across Montana Monday. While the main forcings will
remain north of Colorado, the southern side of the shortwave may dig
deep enough southward to bring enough forcings and moisture into the
northern mountains for some light rain and snow showers to develop
overnight. A cold front will bring a northwesterly surface wind
shift overnight, however, temperatures behind it will not drop
significantly and remain mild in the 40s across the plains and
foothills and 30s for the mountains.

Tuesday will be another dry and mild day across the forecast area
with widespread 70s, just a few degrees warmer than Monday`s, across
the plains and foothills, and 50s and 60s for the mountains. Mid
level lapse rates will steepen through the afternoon that could
provide enough instability to allow for some afternoon showers or
thunderstorms to develop. An upper level low will begin to dig
south from the PNW Tuesday into Wednesday that will transition
upper level flow to southwesterly as it approaches the forecast
area. Models continue to show uncertainties on the track with this
system, however, it looks likely that we will see increasing
moisture and cooler temperatures. A cold frontal passage will
likely bring more high mountain snowfall and widespread rain by
the end of the week. Depending on timing of the frontal passage,
high temperatures on Thursday may drop into the 50s across the
plains bringing them 6 to 13 degrees below the normal seasonal
temperatures for this time of year. Ensembles are showing a decent
spread (5-10 degrees difference between EC, GFS, and CMC) across
the forecast area for Thursday`s high temperatures, however,
temperatures should remain warm enough to keep precipitation in
the form of rain aside from the high mountain elevations. It`s
looking like the forecast area is in store for another cool and
wet weekend.

&&

.AVIATION /06Z TAFS through 06Z Sunday/...
Issued at 1205 AM MDT Sun Apr 28 2024

Light rain showers continue overnight, decreasing toward sunrise.
IFR ceilings with MVFR visibility restrictions through 12z, maybe
patchy fog too, then MVFR ceilings from 12-18z. VFR ceilings this
afternoon/evening around 7000 feet. A few brief showers possible,
but low enough probability not to include them in the terminals
at this time. Light north/northwest winds expected.

&&

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

&&

$$

UPDATE...Mensch
SHORT TERM.....RJK
LONG TERM......Bonner
AVIATION...Cooper