504
FXUS65 KBOU 121013
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
413 AM MDT Fri Jul 12 2024

.KEY MESSAGES...

- Heat wave today through Sunday with temperatures reaching 100 to
  105 degrees across the urban corridor and plains. 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 today from 10a-8p for the I-25
  corridor, expanding across all the plains for Saturday and
  Sunday.

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

&&

.SHORT TERM /Through Saturday/...
Issued at 245 AM MDT Fri Jul 12 2024

Current radar shows some showers and a few lightning strikes moving
across the northeast plains at this time with steering winds
directing them to the southeast. The SPC mesoanalysis indicates some
marginal instability is present with MLCAPE values of 500 J/kg in
the area. These are expected to move out of the forecast area within
the next few hours.

The main headline for today will be the arrival of the highly
anticipated heat wave. Anomalously high 500 mb heights mixed
with notably elevated 700 mb temperatures ranging from 19C to
21C will translate to surface temperatures reaching record breaking
values. Forecast temperatures are set to top the 100F degree mark
across the plains this afternoon. Today`s record high at DIA is 101F
which last occurred in 1971. Today`s forecast high at DIA is
103F, which would put us 2 degrees above the record high for this
day if the forecast verifies. Due to these excessive
temperatures, a Heat Advisory will be in effect beginning at 10 AM
this morning and continue through 8 PM this evening for the urban
corridor. The heat will be widespread across the plains outside
these locations as well. Overnight lows are expected to remain in
the upper 60s for the urban corridor and low to mid 60s for the
rest of the plains. The mountains will feel some of the heat as
well as forecast high temperatures are 5F to 12F degrees above
climo. High mountain valleys are forecast to reach the high 80s.
Overnight lows will range from 44F to 53F for the mountains.

Forecast soundings show some marginal instability over the high
country this afternoon that could allow for some convection to
develop. High dewpoint depressions are expected as well as DALR
climbing above the 500 mb level. While some clouds may develop and
help cool off temperatures over the high country, the expected
environment would likely result in some light rain, gusty winds, and
isolated dry lightning. The plains are expected to remain hot and
dry with dewpoint temperatures staying below 40F aside from a
portion of the northeastern portion of the forecast area where
dewpoints may remain in the low 50s. Hi-res models indicate some
showers may develop in these locations, therefore we have upped PoPs
to account for the potential for scattered showers or storms in
these locations.

&&

.LONG TERM /Saturday night through Thursday/...
Issued at 245 AM MDT Fri Jul 12 2024

Heat is the name of the game for this period, with record high
temperatures expected again Saturday and Sunday.

A dominating 597-598 decameter high will shift slightly eastward
Saturday and Sunday, with the mid level thermal ridge centering
itself across the Central Rockies. This will bring the hottest
temperatures of the year with all guidance supporting highs
soaring into the 100-105 degree range in elevations below 6000
feet both Saturday and Sunday. Thus, we`ll continue the Heat
Advisory for these days, while also expanding that advisory
across the plains to account for expected highs right near the
105 degree criteria for the rural areas.

This heat wave will almost certainly be a record breaking hot
streak of 3 consecutive days (today through Sunday) for Denver,
while the rest of the plains will be near or at record breaking
temperatures. Denver`s forecast high for Saturday is 102F, while
Sunday still appears to be the hottest day (forecast of 103F) as
700 mb temps soar to +21C and moisture remains limited. That would
be just shy of our all time high of 105F - just a slight (10-20%)
chance of reaching that but the ground is extremely dry so
something to watch for in the latest model thermal ridge/moisture
trends. Mountains will also be quite hot, with valley locations in
the 85-90 degree range for highs. Although the deep mixed layer
and elevated terrain should result in convective clouds and
isolated to scattered late day showers/storm. That`s another
potential problem area with dry lightning (storms producing little
rain but lightning) possible for fire weather concerns by Sunday.

We do see a change in the pattern starting Monday, as a backdoor
"cool" front is expected to arrive as a shortwave moves across the
Northern Plains. Let`s be clear, it will still be hot. But the
northeasterly surge, along with increasing upper level moisture
under the ridge, should support at least a little heat relief with
highs on the plains mostly in the mid to upper 90s. Afternoon
shower and storm chances are expected to increase although they`ll
still be fairly high based.

The cooling and moistening trend is expected to continue into
Tuesday as we get into northwest flow aloft as the ridge
retrogrades. It`s quite possible we could see a couple days of
highs in the 80s across the plains, while at the same time shower
and storm chances would increase further. Some trends are then
shown for drying and warming again by Thursday into the latter
part of next week.

&&

.AVIATION /12Z TAFS through 12Z Saturday/...
Issued at 402 AM MDT Fri Jul 12 2024

VFR conditions through the TAF period. Winds have finally made
the transition to drainage and are expected to remain here before
turning to a northerly component for the remainder of the day.
Models indicate that showers may move across the TAF sites between
the 20Z - 1Z timeframe this afternoon. Confidence is low in this
scenario playing out as conditions will be very dry and
instability is lacking, therefore we have left it out of the TAF
at this time. If this were to play out, it would likely result in
high-based showers with gusty outflows. Winds are expected to
return to drainage overnight.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 10 AM this morning to 8 PM MDT this evening
for COZ038>040-043.

Heat Advisory from 10 AM to 8 PM MDT Saturday for COZ038>040-
042>051.

Heat Advisory from 10 AM to 8 PM MDT Sunday for COZ038>040-
042>051.

&&

$$

SHORT TERM...Bonner
LONG TERM...Barjenbruch
AVIATION...Bonner