755
FXUS65 KBOU 260851
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
251 AM MDT Thu Sep 26 2024

.KEY MESSAGES...

- Warm and dry for the foreseeable future with very limited
  chances of precipitation.

- Record highs possible today and Sunday.

&&

.SHORT TERM /Through Tonight/...
Issued at 135 AM MDT Thu Sep 26 2024

A strong upper ridge will remain overhead today, leading to near-
record temperatures across portions of the forecast area this
afternoon. Satellite and radar are quiet right now, and not much
is expected to change today. Guidance does show enough moisture
near the top of the PBL this afternoon for some scattered mid/high
cloud cover, but it doesn`t look like this will affect
temperatures much.

Main question today is just how warm we get. Most MOS guidance
gets DEN to 91-92F, which would break today`s record (90F in
2010). With that in mind, we took a look at the observed DNR
soundings from that day to compare our current setup. The 2010
(forecast) soundings have a 592 (~589) decameter 500mb height,
with a 14.8C (13-14C) 700mb temperature. There was a subtle stable
layer near 700mb on the DNR sounding that doesn`t show up in
today`s forecast soundings, which is likely the best argument for
setting a record today. Time will tell... but either way, it`ll
feel quite warm for a late September day! While overall Heat Risk
is in the minor to moderate range, it`d be a good idea to stay
hydrated and take a break or two if you have strenuous outdoor
activities planned.

&&

.LONG TERM /Friday through Wednesday/...
Issued at 135 AM MDT Thu Sep 26 2024

On Friday, there will be northerly winds in the mid to upper levels
as our forecast area will be on the east side of an upper level
ridge. There will be subsident flow aloft which will keep conditions
dry with plenty of sunshine. A weak cold front will move through in
the early morning and this front will keep temperatures cooler than
Thursday. Highs across the plains will be in the low to mid 80s
which is still above normal for this time of year.

During the weekend, the center of an anomalously strong ridge
will position itself over Colorado. 500 mb heights may reach 594
dm over the Four Corners which are values seen more often in the
middle of summer. Strong subsidence and plenty of sunshine will
allow temperatures to be well above normal. Highs will reach the
upper 80s across the plains and urban corridor on Saturday but
should avoid the 90s due to light southeast surface winds. Added
subsidence and more of a downslope component of the winds will
help to increase temperatures further on Sunday. A high of 90 is
well within reach and the record high of 92 could be tied in
Denver.

The ensemble spread for temperatures on Monday becomes much greater
than the previous days with a range of almost 30 degrees. This is
because models still disagree over the timing and strength of a cold
front that will most likely move through our forecast area Monday or
Tuesday. If the front is delayed in getting to Colorado and it
doesn`t move across the plains until late in the afternoon or
evening, highs may again reach the low 90s. Daily record highs would
be set or tied in many locations. If the front moves through
quicker, highs could be in the 70s across the plains. Models seem to
be trending toward the warmer, less progressive solution so a couple
of degrees were added to forecast highs. This front will not bring
precipitation but will bring gusty north winds up to 40 mph. There
could be some fire weather concerns with those wind gusts if the
warmer temperatures verify.

Tuesday should be cooler as a post-frontal airmass will be in place
with southeast winds. There will still be dry conditions and it is
possible breezy conditions in the mountain valleys and foothills
create elevated fire weather conditions. There will be a very strong
ridge that will develop late Tuesday and into Wednesday. Strong
subsidence and downslope winds will warm temperatures on Wednesday
to the upper 80s across the plains. This may lead to more daily
record highs being broken. There is not much hope for cooler or
wetter weather looking at the ensemble forecasts.

&&

.AVIATION /06Z TAFS through 06Z Friday/...
Issued at 1129 PM MDT Wed Sep 25 2024

VFR through the TAF period. Drainage winds will continue through
the night. Winds are a little bit more tricky Thursday afternoon
but speeds will be light. An approaching weak cold front Thursday
night will likely keep winds a little more westerly. Some increase
in mid/high cloud cover is expected this afternoon but no ceiling
or visibility issues are forecast.

&&

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

&&

$$

SHORT TERM...Hiris
LONG TERM...Danielson
AVIATION...Hiris