000
FXUS65 KBOU 280032
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
632 PM MDT Sat Apr 27 2024

.KEY MESSAGES...

- Current storm to wind down overnight tonight.

- Up to 6 inches of snow through this evening for the mountains
  and foothills with little accumulation over the plains.

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

&&

.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 /00Z TAFS through 00Z Monday/...
Issued at 632 PM MDT Sat Apr 27 2024

Light rain showers continue across the terminals early this
evening. Light rain/snow showers continue overnight, decreasing
toward sunrise. Low ceilings and and periods of reduced
visibility (4-6SM) continue tonight. There is lower confidence on
the ceilings and visibility early Sunday morning. There is a low
chance that lower ceilings (LIFR) develop around midnight into
early Sunday morning. Denoted this as SCT004 for DEN. Visibilities
will be dependent on if and how FG/BR evolves. Can at least see
slight reductions from showers with 5-8SM for periods. There is a
low chance for patchy fog in the early morning timeframe (06-13Z).
Ceilings are expected to improve toward VFR in the 16-19z
timeframe. Low coverage showers after 20z. Winds stay northerly
overnight at 7-10 kts. Light winds Sunday with a northerly
component becoming more WNW/W in toward early evening.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until midnight MDT tonight for COZ033-034.

Winter Storm Warning until 6 AM MDT Sunday for COZ035-036.

Winter Weather Advisory until midnight MDT tonight for COZ037-
041.

&&

$$

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

NWS BOU Office Area Forecast Discussion