389
FXUS65 KBOU 131614
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1014 AM MDT Sat Jul 13 2024

.KEY MESSAGES...

- Heat wave continues through Sunday. High temperatures this
  afternoon will be in the upper 90`s to lower 100`s with highs
  reaching 100 to 105 degrees across the Urban Corridor and plains
  on Sunday. Important to take steps to limit outdoor activity,
  find ways to cool off, and stay hydrated as much as possible.

- A Heat Advisory is in effect both today and Sunday 10 am to 8 pm
  for all of northeast and east central Colorado.

- Monitoring dry lightning threat and possible new fire starts
  today and especially Sunday.

- Slight heat relief expected by Monday, but more so by Tuesday
  and Wednesday. Increasing chance of showers and thunderstorms
  for that period.

&&

.UPDATE...
Issued at 1008 AM MDT Sat Jul 13 2024

A couple of boundaries from convection overnight to the north and
northeast of the area moved across early this morning. This has
allowed for deeper low level moisture to move across portions of
nern CO. As a result, this will allow for decent CAPE over the
nern plains this aftn but the airmass will be capped. Meanwhile,
water vapor imagery does show some mid level moisture across the
area versus yesterday at this time. As a result, will see widely
sct high based showers/storms over the higher terrain. At lower
elevations may see some widely sct high based activity develop
over the Cheyenne Ridge by late aftn and then move southeast
across portions of the plains this evening. With soundings having
an inverted-v type structure along with decent DCAPE, any of the
activity will be capable of producing gusty winds.

As far as highs this aftn, previous outflow boundaries from
earlier this morning may keeps highs similar to yesterday across
the nern plains, as readings stay in the 96 to 100 degree range.
Along the I-25 Corridor, temps late this morning aren`t as warm as
they were this time yesterday. Latest hi res data keeps highs a
few degrees cooler than yesterday with readings mainly in the
upper 90`s to around 100.

&&

.SHORT TERM /Through Saturday night/...
Issued at 208 AM MDT Sat Jul 13 2024

It will be another hot day across the forecast area today as the
slow moving upper level ridge remains situated over the Four
Corners. Current mid-level water vapor imagery shows some upstream
moisture that should enter northern Colorado later today and bring
some welcome cloud coverage this afternoon. Forecast soundings
continue to show large dewpoint depressions and a well mixed
boundary layer to heights above the 500 mb level. DCAPE values are
expected to range from 1500-1900 J/kg for the afternoon and with the
increasing mid-level moisture, high-based convection could develop,
especially over the mountains, resulting in some gusty outflows. Hi-
res models show some virga showers crossing over the I-25 corridor
as well, and indicate dry microbursts are possible with some gusts
reaching 35-45 kts. Instability assessments indicate marginal
amounts of CAPE will be likely which could lead to some isolated dry
lightning.

High Temperatures are forecast to break our current standing record
of 100 degrees at DIA, which last occurred in 2003. Afternoon
highs will range from 100 to 105 degrees across the plains and
some of the high mountain valleys could even make it to the 90
degree mark. Overnight low temperatures will likely remain in the
mid to upper 60s across the urban corridor and plains. Due to
these expected conditions, a Heat Advisory has been issued for
these locations from 10 AM through 8 PM tonight. In addition to
the high temperatures, Vertical Integrated Smoke guidance shows
that later this afternoon/evening, smoke from fires in the PNW
will likely increase across northern Colorado with the most
concentrated levels staying north of I-70.

&&

.LONG TERM /Sunday through Friday/...
Issued at 330 AM MDT Sat Jul 13 2024

Another day of record and near record breaking temperatures can be
expected Sunday as the 500 mb high and thermal ridge hold firmly
over the state. In fact, the eastern plains will likely heat a
couple more degrees over today`s highs with further mid level
warming, and many of the elevations below 4500 feet will see
highs near 105. Denver should also exceed 100 again, breaking the
old record of 100 set in 1878, while Ft Collins and Boulder
should easily break their records of 97 set back in the drought
year of 2002. While the eastern plains are even hotter, they will
be going up against stronger records set back in the Dust Bowl
days and droughts in the mid 1950s.

It should be noted there is a further increase in mid/upper level
moisture expected Sunday, which should provide just slight relief
in the form of clouds, a few showers/storms in and near the
mountains, and slightly cooler outflows in the afternoon. Speaking
of outflows, some of these could be quite strong with microbursts
producing wind gusts >50 mph with DCAPE of 1700-1800 J/kg.
Isolated high based convection could move into the eastern plains
by evening.

For Monday, we still expect slight heat relief via the passage of
a week backdoor cool front and further airmass moistening under
the ridge. That said, even with the front the very warm mid level
temps will support high temperatures well above normal, with mid
to upper 90s still in the forecast for the plains.

Tuesday continues to trend cooler with a nice reinforcing cold
front arriving from the north, behind a deepening upper level
trough across the Great Lakes. This front is also forecast to
bring an increase in low level moisture. At the same time, a
deepening plume of mid/upper level moisture lifts northeast across
the state, as seen in the 700-500 mb specific humidity charts.
Thus, convective coverage is expected to increase further in
coverage and intensity for both Tuesday and Wednesday, and
locally heavy rain may become a threat.

If there was one change in the long term worth noting, it was for
the upper level trough over the Great Lakes/Midwest to be more
persistent, while the upper ridge retrogrades farther west. This
could actually lead to a few more days of cooling and unsettled
weather lingering into the latter half of next week. We`ll use
ensemble averages for this period, which points to near normal
temperatures and a chance of showers and storms each day.

&&

.AVIATION /12Z TAFS through 12Z Sunday/...
Issued at 420 AM MDT Sat Jul 13 2024

VFR through the TAF period. Today will be a similar pattern to
Friday`s with a slightly higher chance of dry microbursts impacting
all TAF sites for a few hours this afternoon. Increasing mid-level
moisture is expected to enter northern Colorado later today that
could increase chances of high-based convection and could result in
some gusty outflows. With dry low-levels, any showers that develop
have little chance of producing rainfall, although isolated dry
lightning can`t be ruled out. Some guidance indicate gusts up to 50
kts possible (20% chance), however, the more likely scenario would
be gusts reaching 35-40 kts at the TAF sites. Winds are expected to
transition to drainage between the 5Z-7Z time frame.

&&

.FIRE WEATHER...
Issued at 330 AM MDT Sat Jul 13 2024

Isolated dry thunderstorms with gusty outflow winds are possible
today. Given recent dryness and much above normal temperatures and
low humidity, any lightning strikes could result in a new fire
start. However, coverage of thunder will be limited by lack of
instability so not enough coverage or threat for a Red Flag
Warning today.

Bigger concerns for dry lightning exist for Sunday afternoon and
early evening as we`ll see an increase in mid/upper level moisture
but still dry and unseasonably warm near surface conditions. That
said, MLCAPE is still limited to just a couple hundred J/kg so
overall cloud to ground lightning threat could still be limited to
isolated coverage. We`ll continue to monitor and message this
threat in our fire weather products.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM MDT this evening for COZ038>051.

Heat Advisory from 10 AM to 8 PM MDT Sunday for COZ038>051.

&&

$$

UPDATE...RPK
SHORT TERM...Bonner
LONG TERM...Barjenbruch
AVIATION...Bonner
FIRE WEATHER...Barjenbruch