656
FXUS65 KBOU 092052
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
252 PM MDT Mon Sep 9 2024

.KEY MESSAGES...

- Warm again Tuesday with isolated showers and storms mainly over
  the mountains and Palmer Divide.

- Best chance (20-50%) for showers and thunderstorms will be
  Wednesday afternoon and evening.

- Fire weather concerns increasing for Thursday with stronger
  southerly winds, near record temperatures, and a drier airmass.

- Mainly dry and calmer weather Friday through the weekend, but an
  isolated storm still possible.

&&

.SHORT TERM /Through Tuesday/...
Issued at 252 PM MDT Mon Sep 9 2024

Scattered showers and isolated thunderstorms will continue into
the early hours across the area. Some of the showers will linger
into the late evening hours and possibly after midnight over the
northeast plains. Due to a dry sub-cloud airmass, gusty winds to
50 mph will remain possible into the evening. Skies clear some
overnight, but expect more clouds than we`ve seen recently at
night. This will help to keep overnight lows a little warmer.

For Tuesday, upper level ridging will continue to bring warm
temperatures to the region. Many places across northeast Colorado
should top 90F degrees again. Airmass dries a little, leading to a
decrease in showers and thunderstorm activity. However, still
expect isolated/scattered showers and thunderstorms over the
higher terrain and across the nearby plains. Wind gusts to 50 mph
will be possible under the stronger showers and thunderstorms.

&&

.LONG TERM /Tuesday night through Monday/...
Issued at 252 PM MDT Mon Sep 9 2024

We`ll keep a few showers and storms in the forecast into the
evening hours Tuesday, mainly in/near the higher terrain and
Palmer Divide. Then, the airmass stabilizes late in the evening
with clearing skies expected overnight with near normal low
temperatures.

Wednesday is still shaping up to be the most active convective
weather day. Moisture is forecast to increase slightly, but weak
QG lift is also noted. Thus, convective coverage is expected to
have an uptick into the scattered category for most areas. Low
level moisture is still depleted, however, so look for mostly
gusty winds and light rainfall from the passing showers and storms
that last from afternoon into the evening.

Thursday will see drier air at all levels, despite the
continuation of weak QG lift. The dry air advection occurs as
stronger south/southwest flow aloft develops in advance of the
ejecting Pacific Northwest/Northern Rockies upper low, essentially
drawing up dry desert air. The main concern will be increasing
fire danger due to gusty winds and near record warmth. High
temperatures will likely soar into the lower to mid 90s across the
plains and I-25 Corridor (Denver`s record is 94F and we should be
very close to that). We`ll address the fire weather concerns in
the Fire Weather section below.

For Friday, the upper level trough to our north shears out,
leaving us in westerly flow aloft. There is still enough pressure
gradient for breezy weather in the mountains, but generally lighter
winds should prevail on the plains in the wake of a backdoor cold
front. That will also bring temperatures down a few degrees, but
still above normal for this time of year. A late day storm is
possible on the far eastern plains where the cap is weaker,
although a farther southward push of the front would effectively
cap things off. We`ll continue some low PoPs over the northeast
plains to account for that.

For Saturday through Monday, we`ll be in lighter and fairly dry
southwest flow aloft. We`ll see a continuation of above normal
temperatures and mainly dry weather. The next changes could start
to enter the picture by Tuesday or more likely Wednesday of next
week, so at least some hopes of seeing more fall-like weather by
then.

&&

.AVIATION /18Z TAFS through 18Z Tuesday/...
Issued at 1128 AM MDT Mon Sep 9 2024

Scattered showers and isolated thunderstorms are expected through
early evening 01-02Z. Winds shifts will be likely from this
activity. For DEN, light and variable to weak northerly winds are
expected before the outflow winds move through. Drainage winds
then develop after sunset 02Z. More high-based showers and storms
with gusty winds are expected Tuesday.

&&

.FIRE WEATHER...
Issued at 252 PM MDT Mon Sep 9 2024

Critical fire weather conditions are becoming more likely by
Thursday as stronger south/southwest flow develops. The airmass
will be quite dry, with humidity levels dropping to 10-15% from
Denver metro eastward across a good chunk of the plains. Near
record high temperatures can be expected, and winds will likely
gust into the 30-35 mph over most of the plains east of I-25.
We`ll also have at least elevated if not critical fire weather
conditions in the mountains and foothills with humidity readings
of 15-20%, and similar gusty winds.

It will still be dry and breezy Friday, but less wind than
Thursday. If the front gets delayed, then we could see at least
elevated if not critical conditions develop again.

Lighter winds are expected for the weekend, but temperatures will
remain above normal with low humidity readings.

&&

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

&&

$$

SHORT TERM...Meier
LONG TERM...Barjenbruch
AVIATION...Meier
FIRE WEATHER...Barjenbruch

NWS BOU Office Area Forecast Discussion