097
FXUS65 KBOU 011755
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1155 AM MDT Wed May 1 2024

.KEY MESSAGES...

- Scattered to numerous showers this afternoon and evening.

- Isolated thunderstorms expected over the eastern plains with
  small hail accompanying the stronger storms.

- Up to 4 inches of snow for the mountains through tonight.

- Another round of showers and storms late Friday/early Saturday.

- Warmer and breezy over the weekend.

&&

.UPDATE...
Issued at 937 AM MDT Wed May 1 2024

We`re off to a fairly quiet start this morning, as the main band
of clouds/precip associated with an approaching front remains off
to the north and west. Meanwhile, some stratus/mid-level clouds
have advected into the far eastern edges of the CWA as a modest
moisture advection regime has set up there. However, surface dew
points remain underwhelming in this area (mid/upper 30s F) and as
a result the overall airmass is still stable. Continued moisture
advection through the day will allow for meager instability in the
eastern plains later this afternoon. Organized severe weather
looks unlikely as weaker updrafts will struggle to survive in a
strongly sheared environment. Still can`t rule out a briefly
organized storm or two capable of marginally severe hail/wind
later this afternoon. However, across most of the forecast region
we still only expected scattered showers and a couple of
thunderstorms.

The morning update comes with only a few minor changes to the
forecast grids, as the previous forecast was in good shape. Did
make some PoP adjustments through tonight along with a few updates
to wind grids in an attempt to better time the frontal passage
today.

&&

.SHORT TERM /Through tonight/...
Issued at 320 AM MDT Wed May 1 2024

Upper level trough over the Great Basin will shift east across the
Central Rockies tonight. Ahead of this trough, the right entrance
region of the jet is producing rain and snow showers over northwest
and north central Colorado. The trough and jet slowly progress
eastward across the region over the next 24 hours. At the surface,
southeast winds will prevail today ahead of a cold front. This front
moves south across eastern Colorado this afternoon bringing gusty
north winds with it. Lift from the jet, trough, and front is
expected to produce scattered to numerous showers this afternoon and
evening. Isolated thunderstorms are also expected to occur.
Soundings show steep mid level lapse rates, however CAPE is expected
to be less than 1000 J/kg and in most cases less the 500 J/kg.
Expect small hail to be the main threat with the storms, though
can`t rule out a couple storms just reaching severe threshold with
one inch diameter hail. The showers and storms progress eastward
through the evening and exit the state overnight. The backside of
the trough will usher in drier air and by 12Z Thursday expect the
area to be free of precipitation.

&&

.LONG TERM /Thursday through Tuesday/...
Issued at 320 AM MDT Wed May 1 2024

A few minor changes in the long-term forecast mainly for PoPs and
winds through Tuesday. Lingering mid-level moisture and weak
MLCAPE values between 100-200 J/kg will allow for isolated showers
and a thunderstorm or two to occur Thursday afternoon. It is
possible that majority of the region could experience virga
versus showers given the dry air aloft. Afternoon temperatures
should remain slightly cooler with the mountains and valleys
between 36-49. The foothills and plains should range between
50-64. The next shortwave trough arrives Friday morning.
Southwesterly flow increases while remnants of Pacific moisture
from a system enter northeastern Colorado. With favorable QG
fields and MLCAPE values near 400 J/kg, scattered thunderstorms
and showers are possible across the mountains and plains Friday
afternoon. BUFKIT soundings display favorable lapse rates near 7-8
C/km and SHIP values between 1-1.2 meaning there is a decent
chance of thunderstorms producing small hail. Showers will likely
be too warm for the valleys but parts of the Park Range above 10k
ft. could receive 1-2 inches of snow briefly Friday evening.

As this system exits, zonal flow will occur. Drier air and warmer
conditions are expected by Saturday and Sunday. This weekend,
PoPs were lowered given the decreasing QPF fields across the
region. Although, there is still a chance for an isolated shower
or two.

There is quite a bit of uncertainty next week. WPC Cluster 500-
hpa Height Analysis indicates a large spread of ensemble members
in agreement of trough pattern focusing on the Central Plains
mainly southeastern Wyoming, Colorado and western Nebraska. If
this pattern were to occur, it may lead to a plethora of
thunderstorms Monday evening across the eastern plains given QPF
amounts of 0.10-0.30 are somewhat in agreement across model runs.
Additionally, there is disagreement if this system exits our
region by Tuesday. Thus, kept the NBM PoPs for now between 10-30%
for the mountains and plains.

&&

.AVIATION /18Z TAFS through 18Z Thursday/...
Issued at 1140 AM MDT Wed May 1 2024

VFR through the TAF period. Main challenge today will be the near
term winds (through 00z this evening) as a lee cyclone develops,
followed by a fairly strong frontal passage later in the
afternoon. Guidance remains inconsistent with wind directions,
speeds, and timing of wind shifts through this period. Behind the
front, a gradual increase in mid-level cloud cover is expected
through the evening, with scattered showers developing near/after
00z. Any showers would likely bring ceilings down to around 5-6kft
AGL for brief periods.

A weak anticyclone is expected to develop tomorrow morning, with
light easterly flow across the terminals. No ceiling or visibility
concerns are anticipated for Thursday.

&&

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

&&

$$

UPDATE...Hiris
SHORT TERM...Meier
LONG TERM...AD
AVIATION...Hiris