842
FXUS65 KBOU 162322
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
522 PM MDT Fri May 16 2025

.KEY MESSAGES...

- Scattered thunderstorms over the mountains Saturday afternoon,
  with just a slight chance of storms on the plains.

- Threat of severe storms on Sunday afternoon, mainly in the
  northeast corner of Colorado. There is uncertainty due to the
  track of the low pressure system and timing.

- Near critical fire weather possible south of I-70 Sunday.

- Cooler and windy with more showers/storms Monday and possibly
  Tuesday, but a lower severe threat.

&&

.DISCUSSION /Through Friday/...
Issued at 330 PM MDT Fri May 16 2025

It`s looking like a pretty quiet late afternoon/evening as we`ve
still got stable air over the mountains, evidenced by the trapped
waves in the mid level cloud deck. Winds have finally started to
ease a bit and that will continue into the evening. We did update
the forecast for more cloud cover through Saturday as we`ll have a
weak shortwave trough passing and then the edge of the moisture
stalling over us ahead of the developing western trough. This will
keep temperatures from rising too much on Saturday despite a
warming air mass. With the moistening, we`ll return to scattered
afternoon thunderstorms over the mountains, but the clouds will
limit the eastward progression. The combination of lift from the
trough and increasing low level moisture could produce a cluster
of stronger storms over the northeast corner Saturday evening.

There`s been a little model convergence for the Sunday through
Tuesday time frame, though we`ll need a better handle on details
before we know what it means. There`s clearer agreement on the two
jet streaks rotating around the trough, bringing a lead wave
kicking out of the trough on Sunday and then the second part of
the trough sliding east Monday night or Tuesday. Unfortunately,
there`s still a lot of disagreement on the relative strength of
the jet streaks and their associated troughs. In general, there`s
a trend towards a bit weaker trough for Sunday, but we don`t have
a lot of confidence in that. This could result in a northward
shift in the position of the QG lift, but it could also mean that
there`s less southwest flow to push the developing dryline
eastward out of Colorado. The main threat for severe weather is
with convergence along the developing dryline which may start in
northeastern Colorado Sunday afternoon, or it may focus a bit
further east or north and be a few hours later. There should be
enough ingredients for all kinds of severe weather somewhere in
this area. The severe threat is probably greatest in bordering
areas of Kansas and Nebraska in the evening, but there may be a
better threat of strong isolated storms in our northeast corner at
the beginning. There may be critical fire weather conditions on
our southern flank, but with green grass for the moment, the
threat is diminished.

Monday is in between the two pieces of the trough, and while
details about any possible lift or the mid level flow have some
uncertainty, we will be in a moist and cooler air mass, probably
with decent north or northeast winds. If there`s not much cooling,
this could be a showery/stormy day, though it may be too cool for
much of a severe threat. That will depend on how much cooling
there is. The current trends towards a more sheared large scale
trough point towards either a faster departure or more westerly
flow on Tuesday, but again there`s not a lot of confidence in
that. NBM gradual decrease in PoPs without warming seems fine for
now. Then pretty solid warming and drying in westerly flow with
weak ridging for Wednesday into the later part of the week. There
may be a shortwave passing north of us in the Thursday/Friday time
frame, but this would probably just generate a bit of wind.

&&

.AVIATION /00Z TAFS through 00Z Sunday/...
Issued at 518 PM MDT Fri May 16 2025

WNW winds will continue for a few more hours with gusts to 20 kts.
Winds will then become north by 02z and then light and variable
by 04z. Overnight winds will become south by 10Z. On Sat, high
based showers will be possible by 19z with gusty and erractic
winds thru the aftn. For now have winds going NE by 19z, but
directions could be all over the place thru the aftn.

&&

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

&&

$$

DISCUSSION...Gimmestad
AVIATION...RPK