Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
319 PM EST Thu Nov 12 2026

Day 1
Valid 16Z Thu Nov 12 2026 - 12Z Fri Nov 13 2026

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM EASTERN
PENNSYLVANIA INTO LONG ISLAND...

A Marginal Risk was introduced in this update based off of the 12Z
HRRR and REFS guidance, which both show a narrow stripe of 1-3"
somewhere between Philadelphia and New York. By 18Z this afternoon,
convection is expected to focus along an east-west oriented warm
front lifting into the I-95 corridor. Should storms become surface
based and begin to rotate, forecast hodographs suggest the Bunkers
motion will be favorably aligned with the boundary to support cell
training over urbanized areas. Cell coverage remains in question,
but given the signal in the 12Z guidance along the urban corridor,
opted to upgrade to a Marginal Risk.

Asherman


Day 2
Valid 12Z Fri Nov 13 2026 - 12Z Sat Nov 14 2026

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

Asherman


Day 3
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...

...2030Z Update...
Forecast is on track for the Marginal Risk emanating from a second
atmospheric river Saturday night. Expect additional rainfall of
1-3" atop the Olympic Peninsula between 00Z-12Z Sunday before the
cold front presses eastward, which could lead to isolated flooding
issues as it overlaps with the rainfall from the previous day.

Asherman

...Previous Discussion...

Area of heavy rainfall in the form of a moderate, yet progressive
atmospheric river will send another wave of enhanced precipitation
into the vicinity of the Olympic Peninsula on Saturday leading to a
low-end threat of flash and areal flooding for the weekend. Heavy
precipitation in the periods prior have allowed for local streams
and rivers, mainly the Skokomish in the valley areas around the
Olympics, to swell enough to warrant some extra caution for
flooding around the river itself. Latest USGS gauge data signals
the river running high, into the 75th percentile to date, for
streamflows with some of the gauges running just below action stage
at this juncture. Rainfall forecasts of an additional 1-3",
locally higher, are expected for the D3 time frame with much of the
rain occurring in a 12-hr window before the passage of a cold
front late in the forecast period (Sat night into Sun morning).
This could send some of the river banks overflowing and cause some
local flood concerns, some of which could be flashy given the
nature of the heavier rainfall on top of the hydrologic function of
the river. With the forecast remaining fairly steadfast in its
presentation and with previous coordination with the local Seattle
WFO already okay with the current risk area, felt there was no
necessary changes needed with the latest forecast as everything
remains on track from a synoptic and hydrologic standpoint.

Kleebauer


Day 4 and Day 5

Valid 12Z Sun Nov 15 2026 - 12Z Tue Nov 17 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF EASTERN TEXAS AND WESTERN LOUISIANA SUNDAY...

20Z Update...

With the 12Z guidance not presenting any strong reason to deviate
from the previous forecast, made only minor adjustments to the Day
4 Marginal Risk over eastern Texas and western Louisiana. This
included trimming some of the northern extent of the previous
outlook. Consensus of the preferred guidance indicates the heaviest
amounts are likely to center near the upper Texas and southwestern
Louisiana coasts, with limited instability likely tempering rates
to the north. Some models are showing amounts that would warrant an
upgrade along the coast. However, due to uncertainty regarding
whether the heaviest rainfall will develop offshore, held off from
upgrading to a Slight Risk at this time.

Pereira

Previous Discussion...

...Eastern Texas/Western Louisiana...

Uncertainty remains in the rainfall forecast from the Day 3 into
the Day 4/Sunday period across the southern Plains to Gulf Coast as
a complex split flow pattern evolves. For Sunday, northern stream
energy should merge with/overtake a leading southern stream wave
providing the necessary lift to support scattered to widespread
storms. Southeasterly flow setting up on the southwestern side of
post-frontal high pressure will lead to moist Gulf return flow this
weekend and particularly into Sunday, helping to push a lingering
frontal boundary over the Gulf back north as a warm front into
Texas. The combination of moisture and modest instability as well
as strong lift along the frontal boundary/coastal convergence
should support the potential for some more robust thunderstorms
producing locally heavy downpours. Despite the latest 00Z GFS/AIGFS
remaining outliers on depicting heavier amounts, the rest of the
deterministic guidance are well clustered on the potential for
heavy rainfall across eastern Texas into western Louisiana, with
locally heavy totals of 3-5" possible. This would be more than
sufficient to support a threat for at least isolated flash
flooding, and possibly a higher risk as confidence increases in the
forecast.

...Gulf Coast...

Guidance indicates the upper-energy will translate eastward Day
5/Monday possibly leading to some additional storms along the Gulf
Coast. However, strengthening high pressure to the north and a
reinforcement of colder, dry air along the backside of the wave
look to help push the frontal boundary into the Gulf. This should
keep greater moisture/instability and the focus for storms mostly
offshore. Even if the boundary/storms were to set up a bit further
north along the coast, FFGs are high and would require a much
greater signal for widespread coverage/several inch rainfall totals
to raise a concern for flash flooding. Therefore, the probability
of rainfall exceeding flash flood guidance is less than 5 percent.

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