Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
316 AM EST Sat Nov 14 2026

Day 1
Valid 12Z Sat Nov 14 2026 - 12Z Sun Nov 15 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS NORTHWEST
WASHINGTON STATE IN THE AREA OF THE OLYMPIC PENINSULA AS WELL AS
NORTH-CENTRAL TEXAS...

North-Central Texas

Global and CAM models have begun to resolve upper-level trough
phasing and continued to converge on the placement of heavy to
potentially excessive convective rainfall today. A mid-level
trough cutting across the Rockies while phasing with a southern
stream disturbance prior to the start of the Day 1 period will
likely lead to surface cyclogenesis later tonight followed by
convective initiation. Storms will then propagate from eastern
portions of the Texas panhandle through northern-central parts of
the state overnight.

Instability of about 100-400 J/Kg MU/ML CAPE paired with 1-1.25"
precipitable water values through central Texas could yield
efficient rain rates. Relative soil moisture is fairly dry so some
of this rain may be more beneficial. 14/00Z RRFS 40km neighborhood
probability of 24 hr QPF exceeding 1-3" is over 5%, which is
consistent with WPC's marginal risk (at least 5% chance) area.

...Previous Discussion...

00Z guidance continues to show the arrival of another round of
moderate to heavy rainfall across portions of the Pacific Northwest
later today. The two-day rainfall total may be enough to result in
isolated flash- and areal- flooding with the 24-hour rainfall
amount ending 12Z on Sunday generally being 1 inch to 3 inches in
addition to what fell Friday and early this morning. Timing largely
remains consistent with the expectation being that much of the
rainfall is expected to occur later tonight in advance of the
approaching cold front. This could send some of the river banks
overflowing and cause some local flood concerns, some of which
could be flashy.

Bann


Day 2
Valid 12Z Sun Nov 15 2026 - 12Z Mon Nov 16 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
COASTAL TEXAS ON SUNDAY...

Enough ingredients appear to be coming together to warrant a Slight
Risk area on Sunday as convection associated with a mid-level
trough approaches from the west/northwest early Sunday. Even if the
models prove to be correct in keeping the highest rainfall totals
off-shore...the there are an increasing number of signals that
problematic rainfall amounts could develop inland (especially true
in urbanized areas and where there is overlap with areas that
received 1.5 to 4.0 inches of rain within the past week).

Synoptically, low-level flow off the Gulf will be drawn northward
across portions of the Upper and Central Texas coast early in the
period in response to the approach of an upper level trough
(potentially an upper low). The GFS and ECMWF both depict 30 to 45
kt flow with decent directional shear in the 925-700 mb
layer...suggesting potential for organized convection. At the same
time, precipitable water values approach 1.5 inches (or 1.5 to 2.0
standardized anomalies greater than climatology for this time of
year).

The models do show a plume of air with precipitable water values
greater than an inch extending northward. Maintained the Marginal
risk area here over questions about how much instability will be
present.

The upper system approaching from the northwest helps shnut the
heaviest rainfall off the coast with time,

Bann


Day 3
Valid 12Z Mon Nov 16 2026 - 12Z Tue Nov 17 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann


Day 4 and Day 5

Valid 12Z Tue Nov 17 2026 - 12Z Thu Nov 19 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN AND CENTRAL CALIFORNIA WEDNESDAY...

An upper-trough and accompanying cold front will progress eastward
from the West Coast into the Interior West day 4/Tuesday.
Increasing moisture along and with the frontal passage will lead to
scattered showers and thunderstorms across the Desert Southwest
and into the Four Corners Region. However, limited instability and
modest moisture should keep rates low and the progressive nature of
the system passage should limit rain totals overall.

Another Atmospheric River (AR) will quickly follow in the wake of
this previous system bringing heavy precipitation to
northern/central California day 5/Wednesday. Snow levels will
briefly increase with the approach of the warmer, moist Pacific
air, though likely not reach levels seen with more significant ARs,
particularly along the foothills of the Sierra given remnant
colder air still in place from the prior system (~4500 feet). The
AR is also expected to generally be on the weaker side and
progressive overall. However, the forecast IVTs of ~ 500 kg/ms
still should contribute to some heavy rainfall amounts, and the
latest round of 00Z deterministic guidance all support areal
average rainfall in the 1-2" range with locally higher amounts
upwards of 3-4". This would be more than sufficient to raise
isolated flooding concerns, and thus have introduced a Marginal
Risk covering upslope regions of the northern/central Coastal
Ranges and inland through the Bay Area to the Sacramento Valley and
foothills of the Sierra.

Putnam


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt