139
FXUS65 KBOU 251543
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
943 AM MDT Wed Sep 25 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 and Sunday.

&&

.UPDATE...
Issued at 930 AM MDT Wed Sep 25 2024

GOES satellite imagery paints a pretty clear picture of where the
upper-level ridge currently resides this morning. With cloud-free
skies stretching from the Mississippi River west to California, it
will be another quiet weather day here in northern Colorado. The
current forecast needs no adjustments on this update.

&&

.SHORT TERM /Through Tonight/...
Issued at 133 AM MDT Wed Sep 25 2024

An upper level ridge axis is centered near the UT/CO border this
morning, and will continue to drift eastward today... ending up
over eastern Colorado by the evening. Depending on your ensemble
and model climate of choice, 500mb height standardized anomalies
are around 1-2 sigma (~90-95th percentile). Unsurprisingly, it`s
going to be warm underneath this ridge, especially as mid-level
temperatures warm and skies remain clear. Forecast highs are in
the mid to upper 80s today and look to be warmer tomorrow.
Overnight lows will also remain above average with lows in the
upper 40s to mid 50s.

&&

.LONG TERM /Thursday through Tuesday/...
Issued at 133 AM MDT Wed Sep 25 2024

An anomalously strong ridge which will be over Colorado today
will slide slightly southward on Thursday. A weak trough will pass
well to the north of Colorado but this feature will lower 500 mb
heights and temperatures. In the low levels, 700 mb will warm to
around 16-17 C and with light downslope flow, highs will reach
near record highs. The forecast still calls for Denver to reach 90
which would tie the daily record.

On Friday, the ridge will build back northward and there will be
very little, if any, wind at 500 mb over Colorado. At the surface,
a weak front will push through in the morning shifting winds to
the northeast across the plains and foothills. This will cool
temperatures down a few degrees but highs will still be well above
normal. With the convergent flow over the mountains, there may be
just enough forcing and instability to generate a couple showers
and perhaps a weak thunderstorm. No impacts are expected from
these.

The ridge aloft will only strengthen this weekend as subsident
flow will persist over the Intermountain West while there is a
strong trough and remnants of a hurricane over the southeast US.
Warm and dry conditions will persist. Ensemble data is starting
to converge on a solution that has Sunday reaching near record
high temperatures. The high temperature forecast for Denver was
increased to 89 F which is a few degrees below the daily record of
92 F.

There is plenty of uncertainty by Monday and into Tuesday. Some
ensemble runs keep the strong ridge in place while a weak trough
passes too far to the north to have an impact on our weather. In
that case, Monday and Tuesday may continue to have highs in the
upper 80s across the plains. However, some ensemble runs are more
aggressive with a trough that brings a cold front through. In
these solutions, highs may only be in the mid 70 across the
plains. These patterns tend to take longer than expected to
progress so the warmer temperatures are favored. Into the middle
of next week, warm and dry conditions are expected as the ridge
aloft does not want to move or weaken.

&&

.AVIATION /12Z TAFS through 12Z Thursday/...
Issued at 531 AM MDT Wed Sep 25 2024

VFR through the TAF period. Drainage flow will slowly turn to more
of a southeast or east wind from late morning into the early
afternoon, before transitioning back to drainage this evening. No
cloud cover is expected through tonight. There may be a brief
period of stronger drainage flow around 03z tomorrow but otherwise
wind speeds should remain near or below 10kt.

&&

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

&&

$$

UPDATE...Bonner
SHORT TERM...Hiris
LONG TERM...Danielson
AVIATION...Hiris