Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KBOU 262331
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
531 PM MDT Tue Mar 26 2024

.KEY MESSAGES...

- Scattered light snow showers in the mountains through
  Wednesday. Across the plains there will be a chance of snow
  showers into early this evening.

- Drier conditions return for Wednesday night through Thursday

- Snow showers and accumulations come back for the mountains
  Thursday night through at least Friday night, scattered showers
  for the northern plains

- Warming trend Saturday into Sunday

- Next storm system expected for late Sunday to Monday, but most
  ensemble members are still on the weaker side

&&

.SHORT TERM /Through Wednesday/...
Issued at 303 PM MDT Tue Mar 26 2024

Radar trends this afternoon show increased orographic snow
showers across the mountains supported by afternoon instability
and moisture in the flow. Some showers have been drifting onto the
adjacent plains along the northern I-25 corridor and from the
southern foothills to Palmer Divide. Day cloud phase satellite
imagery shows hints of some boundaries with one across Elbert-
Lincoln County providing some show enhancement. There is a hint of
a weaker boundary in northern Weld County as well. ACARS soundings
show dry air at in the near-surface layer. Not too substantial,
but likely enough to limit what falls to the ground for any
showers spreading onto the plains this afternoon/evening. Expect
showers to continue through the afternoon into early this evening.
Light accumulations are expected in the mountains with at most
minor impacts to travel from lower visibility and slick roads in
spots. For the plains, scattered rain/snow showers will attempt to
spread eastward with none to a trace of accumulation (if
anything). Showers will diminish across the plains tonight. For
the mountains, showers may not completely shut off overnight, but
will be isolated.

Wednesday, expect dry conditions across the plains and
temperatures warming back into the 50s for the east plains and 40s
to around 50 for the I-25 corridor. Model cross sections show
shallow moisture remaining in the flow and combined with some
marginal instability built in the afternoon will provide some
scattered light snow showers for the mountains in the afternoon. A
flat ridge will begin to move into the region and this will
gradually diminish those showers. Breezy conditions expected in
the mountains with gusts up to 30-40 mph at times.

&&

.LONG TERM /Wednesday night through Tuesday/...
Issued at 230 PM MDT Tue Mar 26 2024

An upper level ridge axis will shift eastward across the Central
Rockies Wednesday night and Thursday, bringing warmer temperatures
for Thursday. There is good agreement per model guidance and
forecast soundings that we`ll push back into the 60s across all
the plains, with mostly 50s foothills, and 30s to mid 40s
mountains and high valleys, although some high clouds could be a
little concerning for reaching maximum potential. There will be
downslope breezes in/near the Front Range Wednesday night with a
hint of a stable layer and 30-35 knot cross mountain flow, but
nothing terribly out of the ordinary (gusts 35-45 mph in wind
prone areas).

Moisture will start to increase late Thursday and Thursday night
as the ridge axis passes by. At the same time, a Pacific jet
stream will start to nose into the state, putting the northern
tier of mountains in the favorable left exit region and sustained
lift from Thursday night through Friday. Typically, the models
overdo precipitation in this type of pattern (southwest flow and
weak warm advection), but in this case we also have at least weak
and persistent frontogenesis and neutral to slightly unstable
lapse rates of 6.5-7.5C/km. Thus, the northern tier of mountains
from around Rabbit Ears Pass to Rocky Mountain National Park and
northward is trending toward a period of accumulating snow from
Thursday night through Friday night. Meanwhile, the I-70 Mountain
Corridor is still on the edge of better lift and moisture, and
will be more blocked in southwest flow aloft. Therefore, any
accumulations would be more meager in that direction. Finally,
given the jet location, we`ll have some low PoPs for a few showers
potentially spilling onto plains roughly along/north of I-76
Friday afternoon through Friday night.

Temperatures will be a little tricky during this period. We`ll be
in a general warm advection pattern, but given the above we may
also see a couple weak surges of cooler air brush the northeast
plains. Thus, we`ll have a more conservative approach to high
temperatures for Friday (upper 50s to lower 60s for the plains),
but a 30-40% chance we are cooler than Thursday with highs in the
mid to upper 50s.

The real warmup is still on track for Saturday and/or Sunday.
That occurs as flow aloft buckles more southerly in advance of the
next storm system dropping southeast off the California Coast. We
have more confidence (50-60%) of hitting 70 across the I-25
Corridor and Plains one or both of these days. Sunday could end up
being a transition day with late cooling as showers and even a
few thunderstorms develop late in the day.

There are still many uncertainties with regard to the next
potential storm system. It would be fair to mostly ignore the 12Z
GFS at this point which showed a heavy QPF event for the Front
Range. Ensembles just don`t support that strong of a storm system
and almost all members shear this energy into an elongated trough
as it moves across the region. That would support mostly light to
perhaps moderate QPF (snow in the mountains, and rain changing to
snow on the plains). Ensembles in the last 24 hours were speeding
up the progression of this feature into late Sunday and Monday,
versus just 24 hour ago when they were slowing it. In any case,
it`s still something to watch as indicated in the previous
forecast discussion. If this trough is organized just right,
there could be a period of moderate upslope rain changing to snow
with a impactful snow in/near the Front Range. Looking from an
ensemble perspective, those odds appear to be 20% or less. But, we
know these types of systems can be quite effective in the spring
if sufficient moisture and instability are present, and we`ve
been on quite the roll during recent precip events.

&&

.AVIATION /00Z TAFS through 00Z Wednesday/...
Issued at 530 PM MDT Tue Mar 26 2024

With showers to the north and south of the Denver area, wind
forecast will remain tricky through this evening (06Z). Winds then
settle at a south-southwest direction at DEN and APA. Seems too
stable for showers in the Denver area over the next few hours.
Some stratocumulus has formed over the southeast part of the
Denver area at roughly 3000-5000 feet. So there is a slight chance
(less than 20 percent), Denver sees this lower ceiling. These
clouds are decreasing and tracking southeast, away from DEN and
APA.

For Tuesday, northwest winds are expected by 18Z after the southerly
winds decrease and turn clockwise. Expect VFR to prevail with
scattered or perhaps fewer mid level clouds.

&&

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

&&

$$

SHORT TERM...Mensch
LONG TERM...Barjenbruch
AVIATION...Meier


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.