792
FXUS65 KBOU 071136
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
536 AM MDT Fri Jun 7 2024

.KEY MESSAGES...

- Temperatures will be warmer today with scattered late day
  showers and thunderstorms.

- Minor snowmelt impacts from rising streams, mainly in Grand
  County

- Increasing chances for showers and thunderstorms this weekend
  into early next week, along with cooler temperatures. A couple
  storms could be strong to severe.

- Hot and mainly dry weather towards the middle of next week.

&&

.SHORT TERM /Through tonight/...
Issued at 444 AM MDT Fri Jun 7 2024

Enhanced southerly downslope flow off the Palmer Divide and into
Denver has weakened a bit early this morning which has allowed
temperatures to drop into the 60s. Fairly mild morning regardless,
setting up for a warmer day ahead.

A flattened upper ridge prevails over the region today under weak
synoptic ascent and mid-level moisture gradually advecting into
the region. Instability and high temperatures will be dependent
on how quickly the mid-level clouds move in with the increasing
moisture. With the axis of the thermal ridge positioned over the
region today highs be a couple degrees warmer than yesterday.
Highs in the lower 90s are likely across most of the urban
corridor and plains. If clouds don`t develop as quickly in the
afternoon, can`t rule out higher values into the mid 90s. Marginal
instability builds in the afternoon with MLCAPE values 200-1000
J/kg from west to east respectively. This is sufficient to support
afternoon scattered showers and thunderstorms. Model soundings
across the urban corridor exhibit the classic inverted-V profile.
DCAPE values range around 800-1200 J/kg. A good indicator of gusty
outflow winds with any convective showers/storms (35-45 mph).
Scattered showers and storms continue across the region through
the early evening hours.

&&

.LONG TERM /Saturday through Thursday/...
Issued at 444 AM MDT Fri Jun 7 2024

Lots of tricky questions for this weekend`s forecast as we`ll have
potential for quite a bit of convection, but we`re also looking at
fairly marginal environments with the trade off of higher moisture
but cooler air over eastern Colorado. It doesn`t help that the
models are struggling with details of the shortwave moving across
the northern plains, which impacts how strong the push of cooler
moist air into our area is.

Saturday looks like the most active day and probably the easiest
forecast. A cold front drops across the plains early in the day
bringing modest cooling and moistening. The a shortwave will move
across the area from west to east. This looks well timed for the
afternoon hours. Model soundings show a weakly capped environment
over the plains, with potentially warmer but still moist enough
air over the mountains for convection to start there. Between the
mountain initiation and a little QG lift/low level convergence
from the short wave and post frontal upslope, we should get a
pretty good batch of storms, maybe a solid line, moving from the
mountains onto the plains in the afternoon. The degree of capping
will likely determine how widespread the storms will be and
whether they evolve into a strong line of storms on the plains or
more disorganized and mostly elevated convection in the evening.
With 40-50 knots of shear and 1000-1500 J/kg of CAPE, along with
decent storm motions and a good chance of linear structure,
there`s a decent severe hail and wind threat. Limiting factors
might be a higher areal coverage of storms if they don`t form a
nice line and potential early cloud cover or too early timing of
the storms. There could be a tornado threat, but it seems like the
storms might be too early to the western part of our plains to
get a good southeasterly low level wind and then the linear
structure could create outflow driven storms further east. Slower
timing of the storms or a faster turn to southeast surface winds
would increase the risk.

Sunday is a lot harder. Some models are bringing in pretty chilly
air, with cloud cover and highs around 70 that would confine
surface based convection to the mountains. These runs have decent
upslope winds into the foothills, but this might just bring
persistent showers. Even the warmer solutions look pretty capped
on the plains, but could be warm enough for more vigorous storms
along the west edge of the moisture, in and near the Front Range.
In these scenarios there could be a threat of some heavy rain as
the winds aloft are lighter and we could have slow storm motions.
The low level upslope would favor eastward propagation though and
reduce the threat of stationary storms. Hard to argue with the
intermediate solution we get from the NBM with high PoPs over the
foothills diminishing eastward and a quarter to half inch of rain
in the favored areas.

Monday is a transition day with temperatures recovering but low
level moisture remaining on the plains. This could be a good
balance for less storm coverage, but still a decent severe threat
with just enough of all of the ingredients. Cooler solutions
still struggle to get warm enough. After that, we`re warmer and
drier with lower storm coverage Tuesday and maybe nothing on
Wednesday. Details on the next trough are uncertain, Thursday
could still be hot and dry, or there could be a front and some
mid level moisture/lift ahead of the next system. That seems more
likely for Friday, but the little cooling and low PoPs in the NBM
seem appropriate.

&&

.AVIATION /12Z TAFS through 12Z Saturday/...
Issued at 536 AM MDT Fri Jun 7 2024

VFR conditions are expected through the TAF period. SSW winds
transition to NW flow by early afternoon at 10-15 kts with gusts
20-25 kts. Biggest concern for impacts will be the
shower/thunderstorm potential in the afternoon, mainly after 21Z.
Storm coverage will be scattered and there isn`t a strong
consensus on where they will more likely be, so kept it as VCTS.
APA will have a higher chance due to proximity to the Palmer
Divide. Strong gusty outflow winds will be the main hazard with
any passing or nearby storms with gusts 25-35 kts.

&&

.HYDROLOGY...
Issued at 444 AM MDT Fri Jun 7 2024

Elevated flows continue across most of the higher elevation rivers
and streams, particularly across the upper Colorado River basin.
Continued snowmelt and additional rainfall this weekend could lead
to additional increases in river flows. Remain cognizant of the
dangers of these cold flows, and be aware of any Flood Advisories.

In the forecast period, the main concern is a limited threat of
burn area flash flooding by Saturday. Moisture increases
substantially as PWATs remain close to 150-200% of normal across
the high country from Saturday into Monday. Better instability
should be in place on Saturday, but storm motions will be fast
enough to limit the flood threat to quick storms in the burn areas.
Storm motions will be slower Sunday and Monday. More widespread
rain is likely Sunday, but the intensity may be limited. There is
a flash flood threat is strong storms develop, with the greatest
potential over the east slopes of the Front Range. By Monday,
there will be some drying although a few storms with heavy rain
are still possible. The threat is lower after that in a drier
environment.

&&

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

&&

$$

SHORT TERM...Mensch
LONG TERM...Gimmestad
AVIATION...Mensch
HYDROLOGY...Gimmestad/Mensch