967
FXUS65 KBOU 012349
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
549 PM MDT Sat Jun 1 2024

.KEY MESSAGES...

- Afternoon showers/thunderstorms today, strongest east of a line
  from Sterling to Limon where a few could become severe.

- Still a chance of a couple severe storms Sunday over the
  northeast corner of the state

- Summer heat through most of next week, with a few 90 degree
  readings over the plains.

&&

.SHORT TERM /Through Sunday/...
Issued at 222 PM MDT Sat Jun 1 2024

Dry line is currently a little west of a line from Sterling to
Limon. The dry line will progress eastward through the rest of the
afternoon and be east of the area by early evening. ML CAPE is
expected to reach 2000 J/kg. This combined with 0-6km Bulk Shear
of 35-40 knots should produce a few supercell thunderstorms. Large
hail up to tennis ball size and damaging winds will be possible
with these thunderstorms. To the west of the dry line, ML CAPE
only reaches 500 J/kg. Dew points are falling into the 20s and 30s
which will result in high-based showers and thunderstorms. Gusty
outflow winds to 50 mph will be the main threat with these
thunderstorms. The showers and storms come to an end this evening
as the airmass stabilizes.

For Sunday, a wave embedded in the westerly flow aloft will track
across the region. At the surface, lee side trough will extend
from far eastern Colorado north-northeast into South Dakota. Best
lift from the passing wave will be over northern Colorado into
Wyoming. Isolated high-based showers are expected to form over far
northern Colorado. Eventually an organized outflow from the
storms in Wyoming dives south and increases low level moisture
which will bring a better chance for rainfall. Over the far
northeast corner of Colorado where it will be more unstable, a
severe storm or two will be possible. Airmass continues to warm
Sunday, with highs across northeast Colorado expected to reach the
mid to upper 80s.

&&

.LONG TERM /Sunday night through Saturday/...
Issued at 255 PM MDT Sat Jun 1 2024

Zonal flow is expected across the CWA Sunday night well into
Monday, then a weak upper trough moves across Monday night into
Tuesday. There is neutral synoptic scale energy over the CWA
Sunday night with weak upward motion Monday through most of Monday
night. Downward vertical velocity is progged on Tuesday. Looking
at moisture, precipitable water values are progged in the 0.30 to
0.80 inch range Sunday night, then they increase into the 0.50 to
1.10 inch range Monday afternoon and night, then they decrease
again Tuesday. For CAPE, models show values under 1,000 J/kg
over the far northeast corner Sunday night. On Monday afternoon
and evening there is limited CAPE, under 600 J/kg, over much of
the CWA with slightly higher values over the far northeast
corner. There is no CAPE progged on Tuesday. So for pops, will go
with 10-30%s over the far northeast corner Sunday evening, then
10-20%s for the northern half of the CWA Monday afternoon and
evening. That`s it. Temperatures stay above seasonal normals
through the periods, with both Monday`s and Tuesday`s highs very
closed to Sunday`s readings. The plains will see mid 80s to lower
90s both days for highs.

For that later days, Wednesday through Saturday, models have
upper ridging to dominate the weather for the forecast area into
Friday. The center of an upper ridge is over southern Utah
Wednesday, then central New Mexico on Thursday. By Friday, the
upper ridge axis is pushed west and northwest of Colorado due to a
strong upper low over the Great Lakes. By Saturday, the upper
ridge axis moves back east towards and into Colorado. Moisture is
sparse Wednesday, Thursday and Saturday, with a bit more progged
on Friday. Overall, it will be dry and pretty warm with the only
decent chance of showers and thunderstorms to be on Friday.

&&

.AVIATION /00Z TAFS through 00Z Sunday/...
Issued at 548 PM MDT Sat Jun 1 2024

VFR through Sunday and into Monday. There is still a fair amount
of virga around but the boundary layer has stabilized such that
convection is weak, and downdrafts/gust fronts are also weaker
than mid-afternoon. Given the latest radar/satellite trends, we
don`t feel the need to include particularly gusty winds in the
TAFs the rest of the evening. Can`t rule them out, but too low a
chance to include. Northerly flow at APA and DEN should give way
to drainage (SSW) after 06Z near 10 kts. At BJC, it should stay
pretty much WNW all evening into Sunday morning.

On Sunday, we are not expecting as much convective showers as
there were today, and thus less chance of convective outflows and
rapidly shifting winds. We will still probably need a TEMPO group
for convective outflows/gusty wind from virga, but not confident
enough to include it just yet for late Sunday afternoon. Generally
winds should be out of the WNW and gusting 20-25 kts from midday
into the evening hours. There is model agreement in a wind shift
via cool front or convective outflow from the north, either way
the result is the same: gusty winds (20 kts) out of the NNE after
00-01Z across the TAF sites, so have introduced it into DEN`s
TAF.

&&

.HYDROLOGY...
Issued at 255 PM MDT Sat Jun 1 2024

Alpine snowmelt will increase runoff the next few days.
Hydrologic forecasts from the River Forecast Centers show a few
streams getting to action stage by Monday or Tuesday, which means
flows will be high and fast but flooding threat appears limited.
Please use caution and respect these fast moving and cold flows in
the high country.

&&

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

&&

$$

SHORT TERM...Meier
LONG TERM....RJK
AVIATION...Schlatter
HYDROLOGY....RJK/Barjenbruch