330
FXUS65 KBOU 120011
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
611 PM MDT Fri Jul 11 2025

.KEY MESSAGES...

- Scattered afternoon and evening thunderstorms today, producing
  locally heavy rainfall and/or flash flooding, with a few severe
  storms possible conducive to large hail and gusty outflow winds.

- Afternoon showers/thunderstorms to continue most days, albeit
  with slightly lesser coverage Sunday and Monday.

- Hi temperatures to linger in the 90s across the plains from
  Sunday through mid-week.

&&

.DISCUSSION /Through Friday/...
Issued at 259 PM MDT Fri Jul 11 2025

Current satellite and radar imagery shows storms have already
developed along the higher terrain this afternoon. So far, the burn
scars have not been impacted by heavy rainfall, however, with fairly
deep and moist upslope flow in place behind this morning`s cold
front, and a shortwave trough approaching from the west, there is
still a limited threat that some heavier localized rainfall may lead
to some flash flood concerns for the northern most burn scars
through the afternoon today.

As the afternoon/evening progresses, storms are expected to become
efficient rain and wind makers as they make their way across the
northern plains where PWAT values of 1-1.5" are expected. The
latest HREF shows a few bullseye of 2 to 4" of rainfall
accumulations from northeastern Weld County to the KS border, with
the heaviest rainfall expected between 9PM and midnight tonight,
generally along and north of US-34. With the potential for
excessive rainfall leading to flooding concerns tonight (Friday),
we have gone ahead and issued a Flood Watch for northeast Weld
County, as well as Morgan, Washington, Sedgwick, and Phillips
County from 6 PM this evening into Saturday morning. For those of
you expected to be out and about in these locations tonight and
early tomorrow morning, be sure to have ways to monitor road
conditions as some more flood prone roadways and low laying areas
may be unaccessible due to flooding.

The SPC has upgraded their Slight Risk for severe storms to include
portions of the urban corridor this afternoon and evening, with
potential for large hail and strong outflow winds the main hazards.
With the greatest moisture and shear profiles expected to be over
the northeastern portion of the plains, we are thinking the main
threat for more organized convection will remain more towards the
northeast corner.

For tonight, showers and storms are expected to clear from west to
east across the forecast area, with some showers lingering into
early morning and near normal temperatures expected across the
forecast area.

Northwest flow aloft will be in place on Saturday as upper-level
ridging begins to build over the southwest. Scattered afternoon
diurnal showers and storms are expected to develop, mainly over Park
County and the Palmer Divide, with a slight chance a few spill onto
the adjacent plains. Temperatures will be a few degrees cooler than
Friday.

Not many adjustments were made to the forecast past the short-term
as the NBM looks reasonable with afternoon convection developing
over the higher terrain each afternoon. Temperatures are expected
to gradually increase through the weekend and linger in the 90s
for the first half of the week across the lower elevations. A
brief reprieve from the 90s looks to be on track by mid-week,
before 90s return for next weekend.

&&

.AVIATION /00Z TAFS through 00Z Sunday/...
Issued at 605 PM MDT Fri Jul 11 2025

Currently, there are multiple outflow boundaries pushing through
all terminals from surrounding convective storms. As these
boundaries collide with each other, new thunderstorms will develop
through 03Z at the latest. Main threat will be VRB gusty outflows
up to 35 kts.

There is still some uncertainty with how the winds will unfold
behind the convection. Guidance is in general consensus of a NE
flow overnight (more N for BJC and APA). This will allow upslope
flow to generate scattered light showers overnight through 07Z.
Have introduced a PROB30 for this reason.

In addition, upslope flow will likely lower ceilings to MVFR
conditions as early as 06/07Z. There is still a chance (<30%) for
IFR conditions, mainly between 07Z and 10Z. Stratus deck should
slowly erode as winds shift southeast. East/southeast winds are
likely to prevail through the day tomorrow.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for COZ042-044-048>051.

&&

$$

DISCUSSION...Bonner
AVIATION...Ideker