533
FXUS65 KBOU 050709
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
109 AM MDT Tue May 5 2026

.KEY MESSAGES...

- A significant snow storm will impact the mountains and foothills
  Tuesday through Wednesday, most pronounced north of I-70 where
  the snowfall will make travel conditions exceptionally
  difficult at times.

- Several inches of heavy wet snow are expected Tuesday night into
  Wednesday for much of the I-25 corridor, especially on colder
  surfaces. Damage to tree limbs will be possible, as well as
  locally slick conditions for the Wednesday morning commute. The
  plains will also see accumulating snowfall as well with some
  potential for heavier snowfall as well in some areas.

- Return to a warmer pattern likely by the latter half of the week
  with a chance of snow showers in the mountains.

&&

.DISCUSSION /Through Monday/...
Issued at 100 AM MDT Tue May 5 2026

Things appear to be coming together for a late season snow event
across much of the area. An upper level trough will move SSE from
the nrn Rockies across the area from Tue aftn thru Wed. Best QG
ascent with this feature will be Tue night thru midday Wed. Cross-
sections show plenty of moisture with this system along with
favorable lapse rates. Low level flow will generally be easterly
thru early Tue evening and then shift to the northeast after
midnight, as a secondary cold front moves across, which enhances
low level upslope component thru midday Wed. In addition, analysis
of cross-sections show potential for jet enhanced heavier pcpn as
well across portions of the area. Precip could change to snow by
midday along the I-25 Corridor with a mix across the plains. With
a high sun angle believe any snow that falls at lower elevations
will generally melt thru the aftn. However, across the mtns and
foothills expect periods of heavier snow especially north of I-70
thru the aftn.

By Tue evening, snow will occur across the higher terrain and along
the I-25 Corridor and adjacent plains.  As the secondary cold front
moves across should see heavy snow develop overnight which will
continue thru Wed morning over the I-25 Corridor and portions of the
plains.  Latest data from operational and ensemble based models
continue to show several inches of heavy wet snow at lower
elevations thru midday Wed. Thus have upgraded previous watches
to warnings and expanded the winter weather advisory further east
across the plains. There could eventually be warning criteria snow
across portions of the adjacent plains but confidence isn`t high
enough at this point for a warning.

QPF amounts vary from 1.0" to 1.5" of water across the plains with
1.5" to 2.5" of water across portions of the mtns and northern
foothills. As for snow amounts, mtn areas north of I-70 may see
18 to 36 inches with up to 24 inches in the nrn foothills. Along
and south of I-70 will see lower snow totals. Across the I-25
Corridor, for now have kept amounts in the 4 to 8 inch range with
locally up to 12 inches closer to the foothills and over the
Palmer Divide. Over the plains have kept amounts mainly in the 3
to 6 inch range. Keep in mind, some of the higher res guidance has
higher amounts across the I-25 Corridor and plains. Thus may have
to increase amounts if additional data overnight continues to
trend towards the higher amounts.

Overall, snow should gradually decrease from north to south by Wed
aftn with snow ending by early Wed evening across southern areas of
the CWA. Meanwhile, overnight lows into Thu morning will drop
well below freezing across most of the plains.

Looking ahead to Thu and Thu night, a weak disturbance embedded in
NW flow aloft may bring a chc of snow to the mtns Thu night with a
slight chc of showers across the plains.

For Fri and Sat, NW flow aloft will remain over the area.  The ECMWF
has another disturbance moving across on Sat while the GFS doesn`t.
Latest blended solution is aligned more with the ECMWF so will keep
in a chc of showers across the area.

Temps will begin to warm on Thu with above normal readings expected
Fri and Sat across the area.

&&

.AVIATION /06Z TAFS through 06Z Wednesday/...
Issued at 1120 PM MDT Mon May 4 2026

A relative lull in -SHRA activity and by associated CIGS in the
030-060 range is expected over the next several hours for Denver
area terminals, with most of the precipitation anticipated to stay
to the north until closer to 10Z. Approaching sunrise, potential
for development of -SHRA and -SHSN will return along with lower
bases in the 012-020 range. Expect a steady decline in CIGS
throughout the day Tue, along with gradually more consistent
snowfall and lowering vis restrictions. Potential for 1/2SM in
heavier SN increases notably after ~05-07Z tonight.

For winds, currently quite light and variable but should
transition to a more stable E/NE direction in the coming hours.
Little chance in direction through the TAF period, through KBJC
will likely stay more N vs NW as it remains on the NW side of
DCVZ. Periods of stronger winds gusting up to 20 kts will be
possible, particularly this morning.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 PM this evening to 3 PM MDT
Wednesday for COZ030-032-037-042>046-049.

Winter Weather Advisory from noon today to noon MDT Wednesday
for COZ031.

Winter Storm Warning until 3 PM MDT Wednesday for COZ033-035.

Winter Storm Warning from noon today to 3 PM MDT Wednesday for
COZ034-036.

Winter Storm Warning from 8 PM this evening to 3 PM MDT
Wednesday for COZ038>041.

Freeze Watch from Wednesday evening through Thursday morning for
COZ038>051.

&&

$$

DISCUSSION...RPK
AVIATION...BRQ

NWS BOU Office Area Forecast Discussion