869
FXUS65 KBOU 250226
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
826 PM MDT Tue Sep 24 2024

.KEY MESSAGES...

- Warm and dry for the foreseeable future with very limited
  chances of precipitation. The mountains have a 10-20% chance of
  showers late Friday into Saturday.

- Record highs possible on Thursday.

&&

.UPDATE...
Issued at 825 PM MDT Tue Sep 24 2024

Clear skies over the CWA this evening with current temperatures
in the 50s to mid 60s for most of the forecast area.  Winds were
pretty light across the CWA as well. Will make a minor grid
updates to winds and temperatures only.

&&

.SHORT TERM /Through Wednesday/...
Issued at 144 PM MDT Tue Sep 24 2024

Current observations show temperatures have made it to the mid 70s
across the plains and mid 60s across the higher elevations so far
this afternoon. Cloud coverage has decreased throughout the day,
and clear skies are expected by this evening as a dry airmass
settles in.

By tonight, northerly flow aloft will take hold as Colorado will be
downstream of an anomalous 500mb ridge pushing east towards the
Four Corners. Quiet weather is expected overnight with overnight
low temperatures forecast to dip into the 30s for our mountain
valleys, 50s for the urban corridor, and mid to high 40s across
the plains.

Blue skies and warming temperatures are expected on Wednesday as the
ridge anchors itself to the southwestern CONUS. With a dry
airmass in place, persisting clear skies, and 700mb temperatures
expected to reach 17C, this will translate to afternoon high
temperatures 5 to 10 degrees warmer than today`s.

&&

.LONG TERM /Wednesday night through Tuesday/...
Issued at 144 PM MDT Tue Sep 24 2024

Very warm and dry weather will definitely be the norm over the
rest of this week, into the weekend, and most likely into next
week as well. A persistent 500 mb ridge will be in place until
further notice. It will not help that Hurricane Helene will merge
with a strong early fall trough over the southeast US. Once the
two merge they just sit and spin over the southeast U.S. into the
middle of next week, effectively preventing any sort of movement
of the ridge. Even though it will be warm or hot during the day
depending on personal perspective, the saving grace this time of
year is that with dry air, light winds, and clear skies,
temperatures will always cool off significantly each night, even
with the urban heat islands. Lows throughout the period should be
in the low to mid 50s across the plains, 40s for the cool river
valleys, and 30s in the mountain valleys. The other bonus from
this pattern is although it will be very warm and dry, winds will
be light so we are not anticipating fire weather concerns for the
next week. Starting with Thursday, it will be dry and mostly
clear across the area. With 700 mb temps around +16 degC, 90
degrees is likely across most of the plains below 5500 ft
elevation. "Literally likely" given NBM has a >50% chance of
exceeding 90 in metro Denver to Greeley, then northeast to the
Nebraska border the chances exceed 80%.

A dry cold front is expected to move across Colorado late Thursday
into early Friday, taking the edge off temperatures but 700 mb
temps should still be around +12 degC, supporting highs in the
80s across the plains and 70s in the mountain valleys and
foothills. The global models actually advect a little bit of
moisture in from the northeast (which is via the stationary
trough/hurricane remnants over the southeast U.S.), and generates
weak rain showers over the high country in the evening hours.
Overall this is a low chance (10-20%) and with how warm it should
be, rain would fall below 12,500 ft elevation. This weekend will
remain very warm and dry under the influence of the ridge overhead
and the stationary trough to the east, expect mid 80s across the
plains and mid 70s for the mountain valleys and foothills.

Next week still looks to be above normal temperature wise and
mostly dry. The overall pattern is still a ridge overhead but the
GFS is more optimistic about a frontal passage early next week
on the backside of a strong trough moving across the Dakotas. The
EC and it`s ensembles are much weaker with that trough and thus
any potential cool down. The ensemble systems likewise are all
over the place in terms of temperatures, which is not surprising a
week out and in early October. All three ensemble systems have
30+ degree temperature spreads Mon-Tuesday next week, though in
general it still looks mostly dry with maybe 20-30% of the members
showing mountain precip, but much less chance across the I-25
corridor and plains. We shall see if this ridge continues to
dominate next week, but that`s what it looks like at this point.

&&

.AVIATION /00Z TAFS through 00Z Thursday/...
Issued at 825 PM MDT Tue Sep 24 2024

Winds look to be light and variable this evening.  Weak normal
drainage wind patterns are expected by 04-05Z.  There will be no
ceiling issues.

&&

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

&&

$$

UPDATE.......RJK
SHORT TERM...Bonner
LONG TERM....Schlatter
AVIATION.....RJK