712
FXUS65 KBOU 292038
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
238 PM MDT Tue Sep 29 2026

.KEY MESSAGES...

- Widespread rainfall, heavy at times, remains likely across the
  far southern portions of our forecast area late tonight through
  early Thursday. A sharp gradient in QPF still likely across the
  Denver metro.

- Flood Watch in effect for southern Lincoln and far southeastern
  Elbert counties through Thursday morning.

- Rain chances decrease late Thursday, leading to warmer and drier
  conditions for the weekend and early next week.

&&

.DISCUSSION /Through Tuesday/...
Issued at 158 PM MDT Tue Sep 29 2026

Quite a bit of uncertainty remains with this upcoming storm
system. A few clear trends appear to be emerging, mixed across the
noise of a full suite of 12z CAMs and global/ensemble solutions.

A well defined upper level low continues to spin near the CA/NV/AZ
border this afternoon. Meanwhile, Hurricane Polo made its second
landfall, this time over northwestern Mexico, earlier today and
continues to race northeastward thanks to the steering flow of the
aforementioned closed low. The upper low should continue drifting
eastward over the next 48 hours, with the associated vorticity
from the remnants of Polo slinging around the east/northeastern
periphery of the low on Wednesday. Deep moisture is expected to
lift northward tonight into early Wednesday, with a precipitation
shield developing over the southern half of the state. That
precipitation should crawl northward during the day, before
eventually pushing off to the east as the closed low slowly starts
to shear out by Wednesday night.

Many folks will not be surprised by today`s forecast
developments... with a pronounced drying trend noted across most
deterministic and ensemble guidance since this time yesterday. As
is often the case with closed lows south of the Four Corners
region, it`s rather difficult to get well aligned moisture/upslope
this far north. There remain a handful of holdouts across today`s
guidance... most notably a few MPAS-core CAMS, a few REFS members,
and the(soon to be retired) NAM and 3km NAM, which continue to
suggest at the potential for significant rainfall totals as far
north as the Denver metro. Conversely, there are now more members
of the GEFS and ECMWF ensemble that have zero precipitation for
DEN (11, with several more with 

NWS BOU Office Area Forecast Discussion