227
FXUS65 KBOU 112335
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
535 PM MDT Thu Jul 11 2024

.KEY MESSAGES...

- The heat wave continues Friday through Monday with temperatures
  reaching 98 to 105 degrees across the urban corridor and
  plains. Overnight lows will be near 70 across the urban heat
  islands, resulting is limited relief from the heat.

- A heat advisory is in effect Friday, Saturday, and Sunday from
  10a-8p for the I-25 corridor. It will be hot everywhere,
  including outside of the advisories, so take steps to limit
  outdoor activity and find ways to cool off and stay hydrated as
  much as possible.

&&

.SHORT TERM /Through Friday/...
Issued at 212 PM MDT Thu Jul 11 2024

A 597dm ridge of high pressure continues to move slowly eastward,
and will be positioned over Utah by late in the day Friday. Our
area will be under weak NNW flow aloft, 15-20 kts of steering
flow. The atmosphere overall is pretty dry between now and
Friday, with PW values ranging from 0.3-0.4" across the mountains
and west slope, to 0.5" along the I-25 corridor, and perhaps as
much as 0.8" across the far NE corner. There is some low level
moisture across Phillips and Sedgwick Counties this evening and
through tomorrow, with mid to upper 50s Tds. This evening there
is a 10-20 percent chance of a thunderstorm out there, and if any
form they could be severe with up to 1" hail and 60 mph wind
gusts. However, there isn`t any forcing or source of lift, so
convection would have to form along a gust front later this
evening, which is not very likely and thus the reason for low
PoPs. Elsewhere, convection should be dying down across the Palmer
Divide and Front Range/Park County before midnight, with light
rain and gusty winds the main impacts. Lows tonight should drop
into the upper 50s to low 60s across the plains, but mid 60s for
the urban corridor. Skies should be mostly clear by daybreak which
will help cool things down before the heat really gets going
Friday.

As mentioned, a heat advisory is in effect Friday from 10 am - 8
pm across the urban corridor, though it will be hot everywhere.
Expect highs 98-104 across the urban corridor and plains, and >90
degrees below 8,000 ft elevation. Even normally cool locations
like North Park, Middle Park, Fairplay, and Breckenridge will be
into the mid 80s tomorrow. Afternoon convection should cool off
most mountain valley locations by 1-4 PM, with light rain and
gusty winds, along with a few lightning strikes possible. No
thunderstorms or rain are forecast for the urban corridor and
plains, just the heat. Clouds and virga may help take the edge off
temperatures after 5 PM but for now expect a hot evening too. With
steering level winds ~15 kts out of the NNW, we don`t expect too
much cloud cover other than within 20 miles of the Front Range.
Temperatures across the plains and much of Denver metro along and
east of I-25 probably won`t cool off below 90 until 7 or 8 PM.

&&

.LONG TERM /Friday night through Thursday/...
Issued at 212 PM MDT Thu Jul 11 2024

Hot and mostly dry weather is expected to continue across the
forecast area through the weekend as upper level high pressure
dominates the region. Friday night, the 597 decameter upper high
will be centered over Central Utah and then shift eastward over
Colorado during the weekend. Max temperatures are expected to reach
the century mark across most of the plains Saturday and Sunday with
mild low temperatures in the 60s. Our current forecast max temp for
Saturday July 13th and Sunday July 14th at DIA is 102 degrees which
would set a new record high temperature for both days if it
verifies. As a result, the Heat Advisory will continue for the Front
Range Urban Corridor and adjacent plains through Sunday evening. Due
to a very dry airmass, no precipitation is expected on Saturday with
the exception of a few high based showers and storms across the high
country. By Sunday, enough mid level moisture may be around to allow
some of the storms to spread eastward onto the adjacent plains.
However, any showers and storms that form would be most likely
produce some light rain and gusty winds.

On Monday, the upper ridge elongates and weakens in response to an
upper level shortwave moving across the Northern Plains States. This
combined with an increase in low and mid level moisture should
result in slightly cooler temperatures and somewhat higher
precipitation chances. Despite the slight cool down, max
temperatures are still expected to be hot with highs in the upper
90s to around 100 degrees on the plains.

Tuesday through Thursday the models are showing the upper high
retrograding westward into the Intermountain West with a
northwesterly flow aloft setting up over Colorado. This pattern
would allow occasional upper level disturbances and cold fronts to
move across the forecast area, resulting in a cooler more active
weather pattern. With increasing PWAT`s of over an inch, some of
the storms could produce locally heavy rainfall during the
afternoon and evening hours during this period.

&&

.AVIATION /00Z TAFS through 00Z Saturday/...
Issued at 532 PM MDT Thu Jul 11 2024

VFR through the TAF period. Winds this afternoon have been all
over the place, but with generally light speeds. A previous
outflow boundary has since washed out, and radar trends upstream
suggest that the potential for any additional outflow boundaries
is low. We should see a gradual trend towards drainage winds,
which should establish sometime between 03-06z.

Quiet conditions are expected tomorrow with only a few mid-level
clouds and hot temperatures. Guidance favors a northwest to north
wind from late morning into the afternoon hours. Can`t completely
rule out an outflow boundary or two from any convection over the
higher elevations west of the metro, but the chance of that is too
low to include in the TAF.

&&

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

Heat Advisory from 10 AM to 8 PM MDT Saturday for COZ038>040-043.

Heat Advisory from 10 AM to 8 PM MDT Sunday for COZ038>040-043.

&&

$$

SHORT TERM...Schlatter
LONG TERM...JK
AVIATION...Hiris