956
FXUS65 KBOU 171818
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1218 PM MDT Sun May 17 2026

.KEY MESSAGES...

- Another active shower/storm day Sunday, although threat of
  severe weather is more uncertain.

- Rain and mountain/foothill snow increases Sunday night through
  Monday with much colder temperatures arriving.

- Accumulating snow for the mountains, and >70% chance of
  accumulation in the foothills. Only a few wet snowflakes
  possibly mixed in for the I-25 Corridor.

- One last spring freeze possible on some of the plains Monday
  night.

- Gradually drier with a warming trend through the end of next
  week.

&&

.DISCUSSION /Through Saturday/...
Issued at 207 AM MDT Sun May 17 2026

We`re looking at another day of scattered showers and thunderstorms,
with the potential for a few strong to severe storms in the
afternoon. The upper level trough to our northwest this morning will
be digging south and progressing east towards Colorado today. In the
flow ahead of the upper low, a disturbance or two will move over the
area. This will help trigger some convective activity today. At the
surface, a front will move into our northern counties this morning,
moving south and potentially stalling somewhere near our southern
counties by early this afternoon. Behind the front, north winds will
bring drier air into the plains. This drier air will lower
instability, making severe storms less likely. Areas near and just
ahead of the front will have higher instability and convergence
along the front as an additional lifting mechanism, making this
area the best chance to see strong to severe storms today. The
positioning of the front early this afternoon is still uncertain,
but looking at high res guidance, the areas most likely to see
severe weather this afternoon will be Lincoln and Washington
counties and the far northeast plains. The biggest concern with
any storms today will be hail, however we could see strong winds
and potentially an isolated tornado as well.

Storm chances will dwindle as we go into the evening, however rain
chances will stick around. The upper level trough will approach the
area late Sunday, moving over the area mid Monday. Strong lift ahead
of this trough combined with decent moisture will bring more
widespread precip chances to the area. As the showers and storms
move east of the plains early this evening, additional showers will
be moving into the mountains from the west. Snow levels will start
out on the higher end, with snow generally above ~10,000ft. However,
the snow level will be continuously dropping overnight and
throughout Monday, leading to a rain/snow transition for the
lower mountains elevations, foothills, and Palmer Divide early
Monday. We could start to see a few snow flakes mix in Monday
afternoon for the I-25 corridor and northern plains, however
accumulations look unlikely (<20%) at this time. The heaviest snow
is expected for areas above 9000ft in the northern front range,
with most likely snow totals around 4 to 15 inches. Most likely
totals for the foothills and lower mountains elevations are a
trace to around 5 inches. For the plains, the highest QPF amounts
are expected along the northern I-25 corridor with most likely
rain totals around 0.5 to 1.5 inches. Lower amounts are expected
further east and south. Precip chances will start to taper off
Monday evening.

Temperatures on Monday will be significantly cooler, with a 20 to 30
degrees drop in highs for Monday compared to Sunday. Temperatures
Tuesday morning could drop below freezing for much of the plains,
which is 2 weeks past our average last freeze date for Denver. Below
normal temperatures are forecast to hang around through much of the
work week, with highs in the 50s and 60s across the plains Tuesday
through Thursday. The main precip event is late Sunday through
Monday, but we could see some additional scattered showers and
storms Tuesday and Wednesday afternoons as a secondary weaker trough
sits off to our west aloft. We start to warm up for the weekend,
with highs getting back into the 70s and low 80s.

&&

.AVIATION /18Z TAFS through 18Z Monday/...
Issued at 1215 PM MDT Sun May 17 2026

Area radars are showing some weak convection coming off the
foothills and weakening as it moves east. Little to no lightning
has been detected thus far. Models keep the northeasterly winds
going at DIA through much of the TAF period. There could be
variable gusts to 30 knots with the convection this afternoon.
Will leave the -TSRA in this afternoon with the most confidence
for just -RA portion. Will continue the chance of rain showers in
the TAF this evening, tonight and much of Monday. For ceilings,
will go with a BKN035-040 this afternoon and evening. Will get
ceilings down to OVC015 and lower after 06Z tonight and Monday.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to 9 PM MDT Monday
for COZ031-033-034.

Freeze Watch from late Monday night through Tuesday morning for
COZ038>051.

&&

$$

DISCUSSION...AP
AVIATION...RJK