Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
857 PM EDT Sun Jun 8 2025
Day 1
Valid 01Z Mon Jun 09 2025 - 12Z Mon Jun 09 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE SOUTHERN
PLAINS TO THE GULF COAST...AS WELL AS THE MID-ATLANTIC...
01Z Update...
...Southern Plains to the Lower Mississippi Valley...
A cluster of heavy thunderstorms over the TX Panhandle and
Northwest TX this evening will further develop into a forward
propagating bowing line (or lines) that last through the night and
reach the Gulf Coast Monday morning. High shear should allow the
existing supercells to persist and congeal into organized MCSs.
Corridors of heavy rainfall in these MCS cases tend to occur in
the left bookend vortex, along the upshear flank of the cold pool,
and with repeating cells which in this case would be activity
developing ahead of the main organized system.
Recent HRRR and RRFS runs are in decent agreement with widespread
coverage of 2-4" across NW and North TX (upshear flanking side of
the activity), southern OK and Northwest LA (left bookend of
activity) through 12Z. This forward propagating system should
increase forward speed late tonight, allowing it to at least
approach the upper TX coast by 12Z.
Therefore, the Slight Risk was expanded a bit south in TX and LA
with the Marginal extended to the Gulf Coast including the Houston
metro.
For further information on TX flooding potential this evening please
see MPD 405 and further downstream MPDs overnight.
...Central Gulf Coast...
Convection that fired on the outflow from morning heavy
thunderstorms over central MS/AL continues this evening with 30kt
bulk shear helping maintain supercell segments over southern AL. An
approaching impulse from TX should allow westward propagation of
this activity which CAMs have shown all day today. The 23Z HRRR
keys in on central MS to Mobile AL as the greatest heavy rain risk
corridor (2-5") which is a bit farther west than previous runs.
Therefore, the Slight Risk was expanded west through southern MS.
...Mid-Atlantic and Central Appalachians...
Shrank western end of Slight Risk where activity has waned with the
cold frontal passage west of the Appalachian Crest. Maintained the
Slight Risk over the rest of the Mid-Atlantic where activity is
ongoing. Please see MPD 404 for further info.
...Midwest...
Pre-cold frontal activity is progged from recent HRRRs to redevelop
overnight as it shifts east. Given lower FFG over central/eastern
IN and southeast MI, the Marginal Risk is expanded up through the
Detroit area. Robust activity over central MO this evening is
progged to shift over southern IL overnight, so the Marginal Risk
was expanded there too.
Lamers/Jackson
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Mon Jun 9 2025
Day 1
Valid 12Z Mon Jun 09 2025 - 12Z Tue Jun 10 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
NORTHEAST, SOUTHEAST, AND SOUTHERN PLAINS...
...Northeast...
A vertically stacked low over the Great Lakes will track north-
northeast into Ontario through the period. South and east of the
low, upper level divergence and forcing will be maximized as a 100
kt jet streak and enhanced divergence from a shortwave rounding the
southern side of the low will all increase the forcing for showers
and thunderstorms in the Slight Risk area of Pennsylvania and
western New York. At the surface, a potent cold front will be
moving east from the Great Lakes/Midwest and into Pennsylvania and
New York. The front will contribute additional forcing for storms.
Somewhat limited Gulf moisture will stream northward ahead of the
front, raising PWATs to as high as 1.5 inches. Instability will
also increase with daytime heating with MUCAPE values between 500
and 1,500 J/kg, with the greatest instability into Pennsylvania.
CAMs guidance generally agree on multiple lines of showers with
embedded storms moving across PA and NY today into tonight. The
storms will mostly be in the late afternoon and into tonight. Due
to multiple rounds of rain, soils will be primed ahead of the
heaviest storms tonight. Each line of showers and storms will be
quick-moving, which should temper the flash flooding threat
somewhat. However, topographic concerns and well-above-normal
antecedent soil moisture conditions from recent rainfall will both
work to increase the flash flooding threat. The inherited Slight is
largely intact with only some trimming across eastern NY as the
heaviest rain looks to stay further west.
...Southeast...
Multiple rounds of showers and thunderstorms are expected to
traverse across the Southeast today and tonight. The first round of
storms is ongoing from southern Mississippi into southern Alabama
and the western Florida Panhandle. The storms are being supplied
with ample Gulf moisture as PWATs are well above 1.75 inches in
most areas with a southwesterly mid-level flow. Meanwhile, a potent
shortwave at the base of the trough will force additional
convection. Cold pool interactions should cause more storms to
form. As the shortwave crosses the Southeast this evening, the
storms should evolve upscale from random clusters of storms to a
line of storms. The line should clear the storms across the north,
but as the surface cold front begins to stall, backbuilding storms
will become increasingly possible in many of the same areas of
southern Mississippi to the western Florida Panhandle that are
currently seeing convective activity.
Storms from last night as well as the ongoing convection near and
just inland from the Gulf Coast have locally greatly decreased the
FFGs in the area. Additional convection this afternoon and evening
should have no trouble causing widely scattered instances of flash
flooding. Further north, greater potential for repeating storms
into the Birmingham and Atlanta metros led to a small expansion of
the Slight into northeastern Georgia.
...Southern Plains...
For eastern NM and west Texas, Monday will largely be a break day
from most of the convection. The area will be on the back edge of a
stalled out cold front, which will be moving eastward into the
Southeast, as it's back edge gets left behind, resulting in a
stationary boundary across northern Texas. Very limited upper level
forcing will keep most convective activity this afternoon and
evening limited in coverage. Most of the CAMs show a single cluster
of storms that originate in eastern NM during the afternoon and
evening, then track along the stationary front across portions of
west Texas. In isolation, this would normally barely amount to a
Marginal Risk, as the cluster should be fairly isolated, with
limited convection anywhere around it, and will be quick-moving.
However, most of these areas have seen numerous rounds of heavy
rain from storms originating off the dryline almost every single
day, including at present, so soils have been well saturated, and
will struggle to keep up with yet another round of heavy rain, even
if it should be relatively brief in duration. A new Slight Risk
area was introduced with this update, but will be somewhat
dependent on the storms tracking over recently hard hit areas, and
there being some pre-cluster storms that likely form ahead of it,
and then are absorbed into the larger cluster. Thus, this is a
low-confidence and lower-end Slight Risk for this region.
Wegman
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Mon Jun 9 2025
Day 2
Valid 12Z Tue Jun 10 2025 - 12Z Wed Jun 11 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHEASTERN
NEW MEXICO INTO MUCH OF WEST TEXAS...
Yet another round of widespread heavy shower and thunderstorm
activity will impact much of far southeastern New Mexico and west
Texas again Tuesday and Tuesday night. While some lingering storms
will be ongoing at the start of the period in parts of the Hill
Country of central Texas, the bulk of the activity will be during
the late afternoon into the overnight. Maximum daytime heating
across the area will increase the instability across much of west
Texas as abundant Gulf moisture remains over the area south of a
stationary front over northern Texas. Storms will blossom in
coverage towards sunset as the LLJ of additional Gulf moisture
strengthens. The convection will both interact with the stationary
front, a possible dryline in southeastern NM and far west Texas,
and some subtle, but still important upper level impulses that
eject out of the southern Rockies.
There has been little change in the ERO risk areas as the signal
remains consistent targeting west Texas for shower and storm
activity. The Slight remains quite large in part due to the
widespread area of west Texas that has seen heavy rain recently,
resulting in wetter than normal soils, especially north towards the
Panhandle.
The Marginal Risk along the Gulf Coast and eastern seaboard also
remains largely unchanged. Storms will be ongoing into New England
at the start of the period, with some chance for largely
disorganized convection from the Gulf Coast to the Carolinas. While
some of these areas have also been hard hit with heavy rains in
recent days, the lack of confidence in much organization to the
storms favors a continuation of the Marginal Risk. Cell
interactions will likely cause localized Slight Risk impacts along
the Gulf Coast, but where that will happen remains highly
uncertain.
Wegman
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Mon Jun 9 2025
Day 3
Valid 12Z Wed Jun 11 2025 - 12Z Thu Jun 12 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
TEXAS AND OKLAHOMA...
Deep Gulf moisture will advect north across much of Texas (and the
Southeast for that matter) on Wednesday and Wednesday night. Slow-
moving upper level shortwave energy will shift east across Texas
through the period. The stationary front that had been across north
Texas for much of the prior 2 days will begin to lift north as a
warm front, especially Wednesday night as the nocturnal
strengthening of the LLJ overcomes what little southward push of
drier air north of the front is left. Meanwhile across West Texas,
the typical dry line will also advance eastward, which will work to
uplift the moisture and cause more widespread shower and
thunderstorm activity. While the storms may be around in isolated
clusters through the day, the greatest concentration of storms will
initiate in the late afternoon and persist through the overnight.
Many of the same areas of northern Texas will be hit with multiple
rounds of storms once again. A higher-end Slight is in effect from
east of Lubbock through the Metroplex, and from southwestern
Oklahoma to around the Austin metro. It's very possible that a
Moderate Risk upgrade may be needed for a portion of this area with
increasing confidence and CAMs analysis of the convective scenario.
Once again, the storms alone would not quite get the risk to a
Moderate level, but the combination of the storms and antecedent
very wet soil conditions.
Up north towards the MN/IA border and southern WI, a subtle
shortwave in the jet will interact with a weaker portion of the LLJ
which will run into a drier air mass to the north. Showers and
storms may train eastward across this region. However, instability
will be a tremendous limiting factor in the potential for flash
flooding. Soils are at or below normal for moisture in the area,
which also will not help with flash flooding potential. A Marginal
Risk remains in effect with few changes.
The Marginal risk in Montana was also maintained with a small
eastward expansion towards the border of ND. Areas of convection
will cross MT through the period, but will be few and far between.
Low FFGs in this area could allow for isolated instances of flash
flooding where there are favorable cell interactions.
Wegman
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Mon Jun 9 2025
A frontal boundary draped generally west to east across the South
will continue to provide focus for numerous showers and
thunderstorms through most of this week. Guidance continues to
converge on Texas and surrounding states as seeing multiple rounds
of heavy rain, with parts of this area (from northern Texas
northward) already primed for flooding with wet antecedent
conditions from recent rainfall. Thus a slight risk remains in
place across east-central Texas into Oklahoma for the Day
4/Thursday Excessive Rainfall Outlook. An eventual need for a
moderate risk in future updates is not out of the question, but
there remains enough uncertainty to preclude that need now and is
also dependent on short range rainfall over the same area. Some
slight eastward shift of the heaviest rainfall axis on Day
5/Friday, more into the Ark-la-Tex region. A slight risk was
introduced for the Day 5 ERO tonight.
A shortwave interacting with a frontal boundary across the
northern tier will bring showers and storms across parts of the
northern Rockies into the Upper Midwest. Moisture anomalies should
be above the 90th percentile in Montana through Thursday, while
convection rides along the cusp of the instability gradient. This
supports a Marginal Risk on the Thursday ERO, which also stretches
eastward into the Upper Midwest along the front. A marginal risk
was introduced Day 5 for parts of the Upper Great Lakes region. By
late week and next weekend, combining upper level and frontal
features will allow for rainfall spreading into the east- central
and eastern U.S., with a general focus around the middle
Mississippi/Ohio Valleys into the northern Mid- Atlantic, but with
ample spread in the details at this point.
Above normal temperatures will continue across interior parts of
the West through much of the period. Daytime highs generally could
be 10 to 15 degrees above normal and may spread gradually eastward
with time. Otherwise, the rest of the country looks near normal or
within a few degrees of normal depending on quick systems moving
through.
Santorelli
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Mon Jun 9 2025
A frontal boundary draped generally west to east across the South
will continue to provide focus for numerous showers and
thunderstorms through most of this week. Guidance continues to
converge on Texas and surrounding states as seeing multiple rounds
of heavy rain, with parts of this area (from northern Texas
northward) already primed for flooding with wet antecedent
conditions from recent rainfall. Thus a slight risk remains in
place across east-central Texas into Oklahoma for the Day
4/Thursday Excessive Rainfall Outlook. An eventual need for a
moderate risk in future updates is not out of the question, but
there remains enough uncertainty to preclude that need now and is
also dependent on short range rainfall over the same area. Some
slight eastward shift of the heaviest rainfall axis on Day
5/Friday, more into the Ark-la-Tex region. A slight risk was
introduced for the Day 5 ERO tonight.
A shortwave interacting with a frontal boundary across the
northern tier will bring showers and storms across parts of the
northern Rockies into the Upper Midwest. Moisture anomalies should
be above the 90th percentile in Montana through Thursday, while
convection rides along the cusp of the instability gradient. This
supports a Marginal Risk on the Thursday ERO, which also stretches
eastward into the Upper Midwest along the front. A marginal risk
was introduced Day 5 for parts of the Upper Great Lakes region. By
late week and next weekend, combining upper level and frontal
features will allow for rainfall spreading into the east- central
and eastern U.S., with a general focus around the middle
Mississippi/Ohio Valleys into the northern Mid- Atlantic, but with
ample spread in the details at this point.
Above normal temperatures will continue across interior parts of
the West through much of the period. Daytime highs generally could
be 10 to 15 degrees above normal and may spread gradually eastward
with time. Otherwise, the rest of the country looks near normal or
within a few degrees of normal depending on quick systems moving
through.
Santorelli
