656
FXUS65 KBOU 051136
AFDBOU

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

.KEY MESSAGES...

- A significant spring snowstorm is developing across the Colorado
  Front Range, and will produce heavy snow in our northern
  mountains and foothills today.

- Scattered rain and snow showers across the lower elevations will
  fully transition to snow by this evening, with accumulations
  occurring overnight into Wednesday morning, potentially
  impacting the morning commute. Snow will taper off north to
  south Wednesday afternoon/evening.

- The heavy, wet nature of the snow will lead to damage to tree
  limbs and power lines. Significant travel impacts can be
  expected for the higher elevations, with more uncertainty in the
  extent of these across the lower elevations on Wednesday.

- 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 /12Z TAFS through 12Z Wednesday/...
Issued at 526 AM MDT Tue May 5 2026

Scattered to numerous -SHRA and -RASN across the urban corridor
are set to continue through the day, although there`s some
question as to their persistence, particularly late morning
through late afternoon. Nonetheless, expect occasional heavier
showers lowering CIGS to 006-012 and vis 3-5SM. Otherwise, CIGS
should largely oscillate between 010-030 with vis at or slightly
above 6SM. -SHSN will be more likely for KBJC with a slightly
slower development for KDEN where NE flow is favored to prevail
over N winds. All terminals will fully transition to snow by this
evening, if not earlier.

In general terms, guidance has continued to trend the heavier SN
later into the early morning hours of Wed, so there`s considerable
uncertainty in the degree of vis/CIG restrictions for the evening
period. However, by 10-12Z, steadier and heavier SN is anticipated
to lead to reduced vis below 1SM and sub-005 CIGS, lasting through
the morning on Wed.

Winds will largely retain a NE direction (more N for KBJC/KAPA),
with slightly gustier periods this morning and early Wed AM.

&&

.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