Westminster, Colorado Weather Forecast Discussion

822
FXUS65 KBOU 221158
AFDBOU
Area Forecast Discussion
National Weather Service Denver/Boulder CO
558 AM MDT Mon Sep 22 2025
.KEY MESSAGES...
- Cold front today with a good chance of showers and thunderstorms
  late this afternoon into tonight.
- Remaining cool with showers likely Tuesday. High mountain snow
  likely Monday night into Tuesday, with winter wx impacts
  possible across the northern mountains.
- Turning warmer and drier again late next week.
&&
.UPDATE...
Issued at 548 AM MDT Mon Sep 22 2025
Models continue to slowly converge for today/Tuesday`s first real
storm system this fall.
Our main area of interest is a fairly sharp shortwave, now
tracking across western Montana, per GOES water vapor imagery and
RAP analysis. Guidance is in broad agreement that a piece of this
shortwave will break off from the parent trough axis and briefly
form a closed low over north central Colorado by 12z Tuesday...
before slowly shearing apart as it gets shoved eastward Tuesday
into Tuesday night.
As a result of the better agreement overnight, there`s been a
gradual narrowing of the main precipitation shield/QPF from
tonight through Tuesday, with a majority of ensemble guidance now
painting a stripe of 0.5-1.25" across the northern 2/3rds of the
CWA... which is near or perhaps a little higher than our overnight
grids. At this point, the two biggest questions I have for the QPF
forecast are (1) where is the actual track of the 500mb low, and
how strong is it? and (2) how expansive is the upslope/QG lift
Tuesday morning into Tuesday afternoon? Both of these will
influence if there`s a narrow band of higher totals, or if this
will be a storm that features a broad (but likely less intense)
amount of precipitation. You wouldn`t have to look too hard to
find a few far higher totals from the overnight model suite... but
don`t get your hopes up on any specific amounts from any given
solution.
Meanwhile, there still looks to be a good signal for mountain
snow. 700mb temperatures fall to around -1 to +1C during the peak
of the precipitation, which would roughly translate to a ~10kft
snow level. Assuming our QPF is reasonable, we could see several
inches of slushy accumulation tonight through Tuesday afternoon,
with the best chance of impacts coming tomorrow morning. Wouldn`t
be surprised to see some accumulations down to around 9-9.5kft,
but impacts there would be minimal. I did think about a Winter
Weather Advisory for COZ033/034 (central/northern mountains above
9,000ft) for quite a while but ultimately will let the day shift
have a full look at things instead.
Beyond this upcoming storm the pattern looks to be relatively
quiet as the upper level ridge returns, along with near/above
normal temperatures.
&&
.DISCUSSION /Through Sunday/...
Issued at 146 PM MDT Sun Sep 21 2025
Current radar shows scattered showers across the higher terrain,
with some storms spilling onto the adjacent plains. With
increasing northwest flow aloft ahead of an incoming system,
expect widely scattered showers and thunderstorms to persist into
the late evening across the Front Range and northern plains.
The severe threat is very low as modeled Skew-T soundings show a
stable environment across our forecast area, with 

NWS BOU Office Area Forecast Discussion