Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Thu Oct 23 2025
Day 1
Valid 01Z Fri Oct 24 2025 - 12Z Fri Oct 24 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS...
01Z Update...
Made mostly minor adjustments to the Southern Plains area,
primarily to remove the western extent of the previous outlook
area. Ongoing regional radar trends suggest the greater threat for
heavy rainfall and flash flooding concerns will extend from
Northwest Texas to along and south of the Red River in association
with the training cells now developing over the region. The 12Z
RRFS Mean, which appears to have one of the better handles on the
current line of storms, shows high probabilities for overnight
totals of 2 inches or more extending from the eastern extent of
Northwest Texas over toward the DFW Metro.
In the Four Corners Region, with the loss of daytime heating,
instability has notably decreased over the past few hours and
rainfall rates are under a 0.25 in/hr across much of the previously
highlighted area. With the consensus of the hi-res guidance showing
additional amounts remaining under 0.5 inch for most locations
through the overnight, the Marginal Risk was removed.
Pereira
16Z Update...
Elsewhere, the Marginal Risk area currently depicted over the
southern Plains remains largely on track from a forecast
perspective, with only modest tweaks made to it to account for the
12Z HREF/06Z REFS suites of guidance and the 06Z EC-AIFS solution.
Convection is still expected to initiate later today and especially
tonight across areas of the southern Plains and upstream
forcing/divergence aloft begins to overlap with the southerly
return flow of moisture and instability up across the Rio Grande
Valley and toward the Red River Valley.
Orrison
Previous Discussion...
...Southern Plains...
At the start of the forecast period, 23.12z, a southern stream
fairly concentric/symmetric mid-level cyclone continues to advance
across the Four Corners region of the Southwest. The low will
continue to consolidate and deepen slightly throughout the day as a
stronger (90+ kt) jet streak rounds the base toward 24.00z
broadening across the southern High Plains providing strengthening
left exit and diffluent larger scale ascent across the Southern
Plains thereafter.
The low levels were already responding with and open Western Gulf
return stream of enhanced theta-E air northward across central
Texas toward the Big Country and Red River Valley. As the
divergence increases aloft, the LLJ responds with 850mb increase
from 15-20kts toward 30-35kts with broad veering increasing low
level confluence/convergence after dark. Combine this with cross
northern Mexico sub-tropical moisture into the 700-500mb layer and
overall total PWat values increase from 1-1.25" toward 1.5" by late
evening. Modest lapse rates with support MUCAPE 1000-1500 J/kg and
the strong WAA/isentropic ascent across the frontal zone should
allow for scattered elevated convective activity across southern KS
and central OK throughout the evening. Hi-Res CAMs suggest there
may be some back-building potential given the strengthening LLJ
and with deep-layer flow, some short-term training may exist.
As the night progresses, core of highest theta-E, West Gulf
moisture reaches the surface front. Moisture flux convergence
increases and half of the Hi-Res CAM suite breaks out or
intensifies weaker scattered/ongoing convection across the eastern
Cap Rock/western Big Country into larger clusters, in a similar
regime; though with lower bases and greater moisture flux through
deeper cells, rainfall efficiency can increase from 1.25-1.5"/hr
toward isolated 2"/hr rates. 00z HREF continues to show a few
signals of such rates over 20% and localized spots of 3"+ (35-40%)
along/near the front near the Red River with an isolated 4" not
out of the realm of possibility.
This is a split signal within the guidance where a few (anchored
by the NAM/NAMnest) remain stable near the surface front allowing
greater flux toward the elevated WAA convection with higher totals
further north east into north-central OK and points north. However,
this is a minority of the suite but to account for this remaining
plausible solutions, have expanded the Marginal Risk north-
northeastward into southern KS, though rates will be lighter and
still grounds remain dry with higher FFG, no greater risk area
could be highlighted at this time, though highest probabilities
within the Marginal Risk lie with any near surface rooted cells
capable of 2"/hr.
...Northwest...
Elsewhere, the leading Atmospheric River plume approaches late in
the forecast period, likely after 24.06z. Strong onshore flow with
40-50kts of low level flow and PWat moisture values of 1-1.25" will
support IVT values over 600 kg/m/s into the Olympic Range. This
will be a good starter for the AR event, but not likely to rise any
flooding/stream concerns for the Day 1 period. No Excessive
Rainfall category will be necessary for this period, but solid
rains are increasing for the Day 2 period.
Gallina
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri Oct 24 2025
Day 1
Valid 12Z Fri Oct 24 2025 - 12Z Sat Oct 25 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS...
The large scale pattern still favors an active day for convection
later today through early Saturday morning over portions of the southern
Plains as strong height falls associated with an upstream
Southwest U.S. closed low/trough ejects out into the High Plains
along with a cold front. Low level moisture and stability will be
in place across much of central and northern TX as the nose of a
30 to 40+ kts southerly low-level jet rides up into the Red River
Valley region. The expectation is that organized convection should
develop initially across areas of west TX and advance east by
later in the afternoon/evening which will be capable of producing
high rainfall rates upwards of 2 inches/hour with the stronger
cells. However, the organized nature of the convection suggests
some forward propagation potential that could mitigate the overall
storm total amounts. In fact, most of the guidance supports a
fairly well- organized MCS evolution into southeast TX and near the
northwest Gulf Coast region by early Saturday morning. Maintained
the Slight Risk area with only some minor adjustments to the
western and northern periphery of the area to account for where the
axis of better instability should be along with corridors of
convective initiation. This is also in better alignment with the
consensus of the 24/00Z HREF and 23/18Z REFS guidance. Scattered
areas of flash flooding, especially for the more urbanized
locations, will be a concern.
...Pacific Northwest into Northwest California...
Only small localized adjustments were made to the Marginal Risk
area as a modest Atmospheric River (AR) pushes across the coastal
and Cascade ranges of Washington and Oregon. The plume of deepest
moisture and associated rainfall will slide southward with respect
to the coastline into northwest California by early Saturday
morning. Strong height falls and precipitable water values over 1
inch total PWats into the coastal range set up the potential for
rainfall rates of 0.75 inches to 1 inch through the Columbia Valley
into central WA with higher rainfall rates remaining off- shore.
Winds of 45-50kts through 850-700mb will result in peak IVT values
of 700-750 kg/m/s. Still agree that the duration of heaviest
rainfall is going to be very limited given the strength of the
height falls and forward propagation of the cold front. QPF signals
remain at the 2-4" range within the favored southwest facing
orography with an occasional rate up to .5" though fleeting; all in
line with a broad Marginal Risk of excessive rainfall.
Bann
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri Oct 24 2025
Day 2
Valid 12Z Sat Oct 25 2025 - 12Z Sun Oct 26 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS INTO SOUTHERN ARKANSAS AND WESTERN LOUISIANA...
Multiple rounds of heavy showers and thunderstorms are expected to
impact the broader northwest Gulf Coast region this period, with
one initial axis of convection likely ongoing Saturday morning
across areas of southeast to east-central TX and advancing across
western Louisiana and southern Arkansas. This will be the
carryover of organized convection from the day 1 period which
should be interacting at least initially with a 40+ kt southerly
low-level jet off the western Gulf. Precipitable water values at or
above 1.75 inches and MUCAPE values locally of 2000+ J/kg will
support high rainfall rates potentially exceeding 2 inches/hour
with the stronger storms.
The arrival of an upper- level jet streak in the subtropical
stream combined with the interaction with the southern stream
closed low/trough axis crossing the southern Plains will favor a
renewed convective outbreak across areas of eastern Texas through
portions of western and southern Louisiana Saturday afternoon
through early Sunday. Even though antecedent conditions are quite
dry, the concern for multiple rounds of convection which combined
may yield some 3 to 5+ inch totals, will probably be enough to
support a threat for scattered areas of flash flooding. The more
sensitive urbanized locations will be at greatest risk for impacts.
For this update, the Slight Risk area was expanded given the
footprint of 2+ inch rainfall amounts within a broadened region of
instability shown by the models. This is also consistent with the
latest deterministic QPF from WPC.
...Pacific Northwest and Northwest California...
Multiple rounds of moisture transport into the coastal ranges will
continue for the period as atmospheric river activity continues.
Locally a few additional inches of rain will be possible for the
windward slopes of the terrain, but given the early-season and
relatively modest nature of this atmospheric river activity, any
flooding concerns are expected to be isolated at best. Therefore,
the Marginal Risk area is maintained with no changes for this
update cycle.
Bann
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri Oct 24 2025
Day 3
Valid 12Z Sun Oct 26 2025 - 12Z Mon Oct 27 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID- AND LOWER-MISSISSIPPI VALLEY AND ALONG THE PACIFIC
NORTHWEST COAST...
Maintained a Marginal Risk area across portions of the southern and
middle Mississippi Valley. The risk across the southern should
diminish once a cold front passes through the area early in the
period and the deeper moisture/instability get shunted eastward.
Farther north where the moisture is not as deep...concern is more
from mid-level frontogenesis and upper level divergence leading to
locally enhanced rainfall rates where antecedent conditions have
been somewhat wetter than other locations. There is plenty
uncertainty as to whether there will be a second round of storms
capable of producing locally heavy rainfall...so overall confidence
is below average which precludes anything higher than a Marginal
risk.
Bann
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
335 AM EDT Fri Oct 24 2025
With a low pressure system over the Mid-South by Monday, and
another possibly developing offshore, rain chances are forecast to
spread into the Appalachians and Carolinas into the southern Mid-
Atlantic. Continued a Marginal Risk in the Day 4/Monday ERO to
include not just the coastal rain but back into the south- central
Appalachians that can be sensitive to heavy rain causing flash
flooding. As these features interact with additional energy to the
west, more rain looks to overspread the Ohio Valley and
Appalachians to Mid- Atlantic by midweek, with Marginal Risk also
in place on the Day 5/Tuesday ERO for the Mid-Atlantic region.
There remains a lot of uncertainty in amounts and placement of this
rain and forecast details are likely to change given the model
spread at this point. Expect rain to continue tracking up the East
Coast Wednesday-Friday.
Troughing across the Northwest and the tail end of an atmospheric
river will lead to precipitation there, including higher elevation
snow that will likely be heavy in the Cascades and perhaps into the
northern Rockies into Monday, with 1 to 2 feet of snow possible.
Energy from the western trough should push a front through the
north-central U.S. for rain chances in the Dakotas and Upper
Midwest especially on Monday. This rain looks to have low rates
given lack of instability, and since this does not tend to be an
area that is sensitive to flooding, do not have any sort of ERO
risk in the outlook at this time. Gusty winds are possible in the
north- central Rockies to Plains early next week with this system
as well. Additional weaker shortwaves/fronts into the West will
keep rain and mountain snow chances in the forecast for
particularly the Pacific Northwest through much of the week.
Cooler weather will be in place across the West early next week,
especially the Northwest through Monday where highs are forecast to
be 10 to 15 degrees below average. Temperatures should moderate
after Monday back to normal or even a little above normal.
Meanwhile, parts of the Plains will be near to above average early
next week before a cool down midweek as colder high pressure builds
in behind a cold front. Much of the East Coast region should
generally be slightly below average through most of the forecast
period.
Santorelli
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
335 AM EDT Fri Oct 24 2025
With a low pressure system over the Mid-South by Monday, and
another possibly developing offshore, rain chances are forecast to
spread into the Appalachians and Carolinas into the southern Mid-
Atlantic. Continued a Marginal Risk in the Day 4/Monday ERO to
include not just the coastal rain but back into the south- central
Appalachians that can be sensitive to heavy rain causing flash
flooding. As these features interact with additional energy to the
west, more rain looks to overspread the Ohio Valley and
Appalachians to Mid- Atlantic by midweek, with Marginal Risk also
in place on the Day 5/Tuesday ERO for the Mid-Atlantic region.
There remains a lot of uncertainty in amounts and placement of this
rain and forecast details are likely to change given the model
spread at this point. Expect rain to continue tracking up the East
Coast Wednesday-Friday.
Troughing across the Northwest and the tail end of an atmospheric
river will lead to precipitation there, including higher elevation
snow that will likely be heavy in the Cascades and perhaps into the
northern Rockies into Monday, with 1 to 2 feet of snow possible.
Energy from the western trough should push a front through the
north-central U.S. for rain chances in the Dakotas and Upper
Midwest especially on Monday. This rain looks to have low rates
given lack of instability, and since this does not tend to be an
area that is sensitive to flooding, do not have any sort of ERO
risk in the outlook at this time. Gusty winds are possible in the
north- central Rockies to Plains early next week with this system
as well. Additional weaker shortwaves/fronts into the West will
keep rain and mountain snow chances in the forecast for
particularly the Pacific Northwest through much of the week.
Cooler weather will be in place across the West early next week,
especially the Northwest through Monday where highs are forecast to
be 10 to 15 degrees below average. Temperatures should moderate
after Monday back to normal or even a little above normal.
Meanwhile, parts of the Plains will be near to above average early
next week before a cool down midweek as colder high pressure builds
in behind a cold front. Much of the East Coast region should
generally be slightly below average through most of the forecast
period.
Santorelli
