663
FXUS65 KBOU 161656
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1056 AM MDT Sun Jun 16 2024

.KEY MESSAGES...

- Warmer, drier, and breezy today with Heat Advisories across the
  southeast Denver metro.  Well above normal temperatures will
  continue on Monday.

- Critical fire weather conditions today and again on Monday.

- Snowmelt producing minor impacts from high streams. Gradually
  diminishing flows next week.

- Cooler for Tuesday and Wednesday

&&

.UPDATE...
Issued at 1016 AM MDT Sun Jun 16 2024

The cold front mentioned in yesterday`s discussion is indeed
throwing a wrench into the forecast. The front has been a bit
stronger than forecast and has raced across the Denver metro in
the past couple of hours. It had warmed up considerably to the
south of the boundary, with an 87F recorded at Centennial with
Limon also up to 93F. Meanwhile, temperatures are still in the low
to upper 70s north of the boundary with dew points in the upper
40s to low 50s.

How the temperature/moisture gradient evolves today is still
somewhat uncertain. The HRRR insists on quickly mixing out the
shallow moisture later this afternoon with highs in the mid/upper
90s for the southeast metro, while other CAMs maintain a deeper
moist layer that never fully erodes, leaving temperatures closer
to 90F. Reality will likely be somewhere between these two
scenarios with highs generally in the low 90s across Denver and
into the mid/upper 90s southeast into Lincoln county. Ultimately
could probably cancel the Heat Advisory for Denver itself but for
simplicity will just let it roll until there`s an obvious sign one
way or another. Ultimately did make several changes to the
temperature grids today that are closer to the multi-model mean.

How far the boundary sinks south will also play a role with the
Red Flag Warnings which go into effect at noon. With mixing
increasing this afternoon there should be fairly widespread
critical fire weather conditions across the Palmer Divide and
Lincoln county.

Also can`t rule out an isolated storm or two later this evening,
mainly along the I-76 corridor northeast of Fort Morgan... where a
marginal risk was drawn by the SPC. It will be hard to get a storm
to break through the CAP but models do have an unstable (MLCAPE
~1000 J/kg), sheared airmass that would support a hail/wind threat
(especially with DCAPEs > 1500 J/kg).

&&

.SHORT TERM /Through tonight/...
Issued at 247 AM MDT Sun Jun 16 2024

Hot and dry weather will continue today. Expect mostly sunny skies
today due to limited moisture and instability. CAMs are in favor
of Denver cyclone development this afternoon but there is still
uncertainty in where this will set up. Although wind direction is
still in question, wind speeds between 15-20 mph will produce
wind gusts up to 30 mph along the Palmer Divide and adjacent
plains. This pattern combined with low relative humidities as low
as 10 percent will lead to critical fire weather conditions this
afternoon. Similar conditions will also occur for portions of
Grand and Summit counties. Additionally, 700mb temperatures
increase between 16-18C. This will likely lead to afternoon highs
between 90-100 for the urban corridor and plains. Mountains and
foothills also trend above normal this afternoon reaching mid 60s
to upper 70s with a few mountain valleys reaching 80. A Heat
Advisory covers portions of the Palmer Divide, metro Denver and
southeast plains through 7 PM MDT this evening. Those sensitive
to heat should limited exposure outdoors. A marginal risk of
storms exists for the northeast corner where an isolated storm
could occur clipping our area from the Nebraska Panhandle this
evening. Tonight, low temperatures are slightly above normal and
mostly clear skies are expected.

&&

.LONG TERM /Monday through Saturday/...
Issued at 247 AM MDT Sun Jun 16 2024

SW flow aloft will continue on Mon as an upper level trough moves
into the nrn Rockies.  As mentioned yesterday, will still have a
boundary associated with convection to the north located
somewhere over nern CO. Based on current data, it appears this
boundary will be a tad further north and located near the CO-NE
border. South of the boundary temps will be in the 95-100 degree
range across the plains while closer to the NE border highs may
stay in the upper 80`s to lower 90`s. Meanwhile, along and north
of the boundary decent MLCAPE will be in place but capping
inversion may still inhibit tstm development, so have kept pops
in the isold category.

For late Mon night into Tue, a cold front will move across the
plains.  This front will drop temps back into the upper 70s to lower
80s for aftn highs over nern CO.  Any low level moisture with this
front will move into the higher terrain, however, MLCAPE is marginal
at best so any tstm development will be rather isold.

Looking ahead to Tue night into early Wed, eventually the low level
flow will become more easterly in the lower levels.  This will allow
for some return of deeper low level moisture. At this time, it`s
not clear how far north this moisture will be as it may end up
further south over the Palmer Divide and sern CO. Meanwhile, the
flow aloft will remain from the SW. The blended solution has
showers and tstms developing over the plains Tue night with rather
high pops. Confidence in this is low at best since this activity
could end up further to the east and south. Thus have lowered pops
into the chc category.

For the rest of Wed, the low level flow will become more southeast
which will allow for deeper low level moisture to move across the
plains.  This should lead to somewhat better instability, however,
may still have to contend with a cap, as convective temps may not
be reached across the plains. Over the higher terrain, there will
be a chc of aftn storms. Highs will only be in the mid 70`s to
lower 80s across the plains.

By Wed night into early Thu, both the ECMWF and GFS indicate a weak
disturbance embedded in SW flow aloft may move across.  This feature
combined with a warm advection pattern may lead to a chc of elevated
convection across portions of the plains.  For the rest of Thu,
MLCAPE should gradually increase by aftn with a chc of storms in the
late aftn and evening hours.  Highs will be warmer as readings rise
into the mid to upper 80s.

On Fri, the flow aloft will continue from the SW.  Overall, there
should be enough instability for at least sct storms across the
area.

&&

.AVIATION /12Z TAFS through 12Z Monday/...
Issued at 509 AM MDT Sun Jun 16 2024

VFR conditions are expected through the TAF period. A Denver
cyclone may lead to a tricky wind forecast in the afternoon as
winds may shirt briefly northeast to southeast as the cyclone
pushes east. By 20Z, expect wind speeds to increase between
11-15kts producing gusts up to 25kts. Drainage winds are possible
by early evening.

&&

.FIRE WEATHER...
Issued at 247 AM MDT Sun Jun 16 2024

Critical fire weather conditions are likely for portions of Grand
and Summit counties due to low humidity near 12-14 percent and
southwesterly winds producing wind gusts up to 25 mph this
afternoon. Additionally, similar conditions will occur for the
Palmer Divide, and adjacent plains including metro Denver.

Elevated to Critical fire conditions will be in place on Monday
across the Palmer Divide, portions of the Denver Metro area and
across South Park and Middle Park. Gusty winds, low humidity and
well above normal temperatures will occur from midday Monday
through early Monday evening. A cold front will move across on
Tuesday which will decrease fire conditions in most areas.

&&

.HYDROLOGY...
Issued at 247 AM MDT Sun Jun 16 2024

Elevated flows continue in the mountain streams, with Flood
Advisories remaining in effect for the streams above Granby and
Grand Lake. Remain alert of the dangers of water that is running
high and cold. Flows are expected to gradually decrease next week
as the peak snowmelt is passing by.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM MDT this evening for COZ213-214-241-
245>247.

Heat Advisory until 7 PM MDT this evening for COZ040-041-045>047.

&&

$$

UPDATE...Hiris
SHORT TERM...AD
LONG TERM...RPK
AVIATION...AD
FIRE WEATHER...AD/RPK
HYDROLOGY...AD/RPK