Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
725 PM EST Sat Nov 14 2026

Day 1
Valid 01Z Sun Nov 15 2026 - 12Z Sun Nov 15 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS NORTHWEST
WASHINGTON & PORTIONS OF TEXAS...

Texas...
A negatively tilted upper level trough is crossing TX at this
time. Moisture and instability are slowly increasing, with both
interior and coastal TX showing pockets of 560+ J/kg of ML CAPE.
Precipitable water values are 1.1-25" across interior TX and closer
to 1.5" near the Middle TX Coast. Both areas are within regions of
850 hPa confluence.  Activity across Northwest TX is expected to
continue to forward propagate to the southeast with time while
storms near the central TX coast continue to bubble overnight as
they slowly shift offshore. A Marginal Risk of excessive rainfall
remains in effect for both areas, with some changes made to account
for radar reflectivity trends and the most recent REFS guidance.
Hourly amounts to 2" with local totals to 4" are possible in both
areas where storms manage to backbuild, train, or merge. Flash
flooding issues are expected to be isolated to widely scattered at
best.

Pacific Northwest...
A low pressure system will focus storms ahead of its attendant
cold front as it arrives over the Pacific Northwest tonight. Some
relatively modest instability (100-250 J/Kg MUCAPE) will work its
way into the region along with moisture (0.5-1.5" precipitable
water values). The REFS guidance indicates that a few hours of
heavy rain (0.5"+) is possible overnight, which could lead to rises
in the Skokomish River. Left the Marginal Risk area as-is, with no
changes from continuity.

Roth


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...

...2030z Update...

The inherited marginal (at least 5% chance) and slight (at least
15% chance) risk areas were expanded south and westward through
Corpus Christie and Matagorda Bay respectively. The synoptic setup
outlined in the previous discussion remain true, with the upper
trough responsible for storms over north-central Texas today
continuing to dig southeastward toward the Gulf Coast. Lobes of
shortwave vorticity propagate through southeast Texas Saturday
afternoon. Convection is expected to reignite tomorrow afternoon
over central Texas as instability builds over the area. The
heaviest rainfall should wrap up by midnight Monday.

The latest/12z guidance has shifted the max QPF axis to between
Houston and Corpus Christie for the 24 hour period ending at 12z on
Sunday. 24 hr 5" 40km RRFS exceedance probabilities are between
20-60%, while 3" EAS probabilities are between 15-30% within the
highlighted slight risk area. GEFS first guess fields have a 15-25%
chance of 1-2 year ARI exceedance, as well as UFVS verified flash
flooding, which is consistent with the marginal and slight risk
areas in effect for Saturday.

Kebede

...Previous Discussion...

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 shunt 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.

Kebede


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
THE FLORIDA EAST COAST TUESDAY-WEDNESDAY & CALIFORNIA WEDNESDAY...

West...
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. Precipitable water values ~1" in
the Lower Deserts combined with a lowering trend in the 1000-500
hPa thickness pattern associated with the system should nearly
saturate the atmosphere. Effective bulk shear won't be lacking.
But, the system is progressive.  Should the atmosphere saturate
much more, a Marginal Risk could prove useful. Whenever cells can
align or merge or mesocyclones manage to form, hourly rain amounts
to 1.25" are possible could lead to issues in dry washes/arroyos
or burn scars. The situation continues to bear watching.

Another Atmospheric River (AR) will quickly follow in the system's
wake, 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 12Z deterministic
guidance all support areal average rainfall in the 2-4" range with
locally higher amounts. This would be more than sufficient to
raise isolated flooding concerns, thus left the 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 as-is.

Eastern Florida...
A situation with nearly antiparallel flow (low-level easterlies and
upper level westerlies) takes hold on Tuesday. Precipitable water
values of 1.25-1.5" are forecast, and the low-level flow should
bring instability off the warmer than average Gulf Stream.
Effective bulk shear should be sufficient for organized convection.
Hourly rain amounts to 1.75" would be possible wherever short,
training bands manage to materialize. By Wednesday, an approaching
upper level system closes off into an upper level low which could
continue the situation for localized heavy rainfall. Marginal Risk
areas were introduced for portions of Eastern FL for Tuesday
through Wednesday night as a few pieces of global guidance
advertised the heavy rain potential.

Roth


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