722
FXUS65 KBOU 290541
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1141 PM MDT Tue Apr 28 2026

.KEY MESSAGES...

- Areas of patchy fog, resulting in low visibilities for the
  northeastern plains through Wednesday morning.

- Scattered showers/isolated weak thunderstorms Wednesday
  afternoon.

- More active pattern continues through the week with highest
  chance of more significant/beneficial precipitation in/near the
  Front Range Thursday - Thursday night.

- Warmer and drier conditions expected by the weekend.

- Chance of showers returns early next week.

&&

.DISCUSSION /Through Tuesday/...
Issued at 1118 PM MDT Tue Apr 28 2026

Current radar imagery shows decreasing showers over the forecast
area, with upslope flow allowing a few additional rain showers along
the Urban Corridor. As subsidence filters in behind the exiting
upper level shortwave, expect showers to gradually end in the next
few hours, with partly cloudy skies behind it. Due to this,
radiation fog is likely across our northeastern plains through
Wednesday morning.

The break in precipitation will be shortlived as another weak
shortwave trough treks across Colorado Wednesday afternoon. Increase
in QG lift and mid-level frontogenesis will permit another round of
scattered showers (and light mountain snow), particularly for the
southern foothills, Palmer Divide, and Lincoln county areas due to
best forcing. Afternoon instability should grow, with MLCAPE between
100-500 J/kg to support isolated weak thunderstorms. Temperatures
will likely reach up to the low 60s for most of the plains, however
that will still keep us about 4-6 dg F below seasonal averages. A
weak cold front in the late afternoon/evening will bring cooler
temperatures for Thursday.

Some uncertainty still remains in the forecast for Thursday into
Friday, despite being about 48-hrs out. A 500-mb closed low
associated with a longwave trough over central U.S. will begin
trekking east from southern California into New Mexico on Thursday.
For our forecast area, this will result in weak QG ascent and
potentially light upslope flow, from the surface up to about
700-mb according to cross-sections. These two forcings will
promote precipitation, mainly for our Front Range
mountains/southern foothills, Urban Corridor, and Palmer Divide.
Places farther north and east unfortunately likely won`t see most
of this precipitation.

QPF amounts vary between guidance, however models do agree that the
southern Front Range mountains/foothills and portions of the Palmer
Divide will receive the most QPF, with some guidance indicating
about 1.00" of QPF by Friday morning. For the Urban Corridor,
anywhere from 0.20"-0.60" QPF likely depending on the strength and
duration of upslope flow. For portions of Weld county and east to
the northeastern plains, T-0.20" QPF due to overall less forcing. It
is interesting to note that both the AIGFS and ECMWF-AIFS seem less
enthusiastic with QPF compared to the deterministic runs. In
addition, there are discrepancies between hi-res guidance, with
the NAM also less enthusiastic compared to the HRRR. This large
spread in QPF values will lead to some uncertainty with total
snowfall amounts for our mountains and foothills. Temperatures on
Thursday will support snowfall above 6500-7000 ft. If guidance
starts honing in on wetter solutions, winter weather highlights
will be warranted, as travel will likely be impacted on Thursday
and possibly Friday morning, particularly for the I-70 mountain
corridor. Will hold off on any highlights for now due to the
uncertainty.

For the weekend, warmer and drier weather is expected as an upper
level ridge builds over the Rockies. Ensemble guidance is now in
better agreement of temperatures rising above normal, reaching the
low 70s by Sunday. This will be shortlived, however, as models try
to resolve multiple disturbances early next week, which will bring
almost daily chances for precipitation.

&&

.AVIATION /06Z TAFS through 06Z Thursday/...
Issued at 1140 PM MDT Tue Apr 28 2026

A surge of northeast winds has brought a few showers and
increased cloud coverage across the Denver area with ceilings of
4000-7000 feet. Expect clouds to slowly decrease and lift a
little, but skies will remain scattered/broken overnight and into
Wednesday morning. The next system will bring showers and
increased cloud cover mid to late Wednesday morning (15 to 18Z).
Showers increase after 18Z, with ceilings 5000 to 8000 feet. Under
the showers, ceilings could fall to around 3000 feet. The chance
for showers continues through 06Z. Ceilings lower slowly after 00Z
Thursday falling to 1500 to 3000 feet 03-06Z.

&&

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

&&

$$

DISCUSSION...MAI
AVIATION...12

NWS BOU Office Area Forecast Discussion