Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
842 PM EDT Mon Jun 2 2025
Day 1
Valid 01Z Tue Jun 03 2025 - 12Z Tue Jun 03 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL PLAINS...
...Central Plains...
The Slight Risk area was trimmed southeastward out of the Sand
Hills and behind the line of storms currently bisecting Nebraska.
As expected, the storms across Nebraska are barely moving, and are
producing rain rates to 3 inches per hour in otherwise normally dry
areas. Thus, the Slight remains in place for central and much of
eastern Nebraska. When the storms begin to move, likely as the line
interacts with a second progressive line of storms across west
Kansas, they should propagate eastward, so areas west of the line
should remain with relatively little rainfall.
The surrounding Marginal across Minnesota was trimmed as the storms
in that area are very progressive. While there may be some
redevelopment of shower activity later tonight, it is not expected
to result in any flooding concerns.
The Marginal in west Texas and western Oklahoma remains largely
intact as potential backbuilding of the line could result in
localized training, which may produce an isolated flash flood or
two.
The Slight across south Florida has been downgraded with this
update as the peak rainfall rates from storms have come way down as
the storms have congealed into a larger MCS, but with relatively
low embedded rainfall rates. Most areas seeing rates below an inch
per hour should preclude anything other than isolated flash
flooding through the evening.
Wegman
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
842 PM EDT Mon Jun 2 2025
Day 2
Valid 12Z Tue Jun 03 2025 - 12Z Wed Jun 04 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PARTS OF THE
CENTRAL UNITED STATES AS WELL AS SOUTH FLORIDA AND THE FLORIDA KEYS...
...Texas to the Great Lakes...
An active day of convection is likely on Tuesday as a cold front
sags across the Heartland, providing the focus for widespread
showers and thunderstorms. This front will be pushed southeast in
response to an amplifying northern stream trough which will dig
across the CONUS as far south as Texas. This will drive height
falls across the region, with embedded shortwave impulses racing
northeast, and a poleward arcing jet streak downstream of the
primary trough axis combining to provide additional ascent. This
deep layer lift will work into robust thermodynamics characterized
by an overlap of PWs above the 99th percentile (NAEFS) and a ribbon
of MUCAPE exceeding 2000 J/kg, surging northward on 30-50 kts of
850mb flow emerging on return flow from the Gulf.
The CAMs continue to be in excellent agreement in the coverage of
convection on Tuesday despite some temporal and spatial differences
owing to timing of the front. Despite these modest differences,
there is good agreement among the REFS and HREF ensembles to
suggest widespread 1"/hr rain rates from the northern TX Hill
Country all the way to the eastern Missouri Valley (probabilities
exceeding 50% across this entire area). Although mean 0-6km winds
of 20-30 kts indicate progressive storm motions, this flow aligned
to the front and combined with Corfidi vectors that collapse and
veer to the NE indicate a high potential for redevelopment to the
SW into the more intense thermodynamics and training of cells to
the northeast. Where this occurs, total rainfall exceeding 3" is
likely (>60% chance in HREF/REFS) and 5" is possible (>40% chance),
with even the global ensembles suggesting a 10-30% chance for 3" in
this same region. The inherited SLGT risk was tailored for this new
guidance, with the biggest adjustment being an extension SW into
the Hill Country of TX where convection that develops along the
tail of this front will likely feature slow storm motions and
backbuilding to produce heavy rainfall.
Although heavy rainfall is also likely in convection that develops
northeast into the Upper Midwest and Great Lakes, storms should be
more progressive and the Corfidi vectors suggest less opportunity
for training, so only a MRGL risk is needed north of Iowa.
...South Florida and the Florida Keys...
Shortwave trough over the Gulf may amplify enough to become a weak
closed low Tuesday and then spin nearly in place as it gets
suppressed beneath a Bermuda- type ridge to its northeast. This
will maintain modest synoptic ascent across Florida, but some
enhancement is likely as a jet streak over the Atlantic tails back
to the SW, placing the favorably diffluent RRQ overtop the
peninsula. This forcing will combine with continued, albeit
weakening, low-level convergence along a decayed front/surface
trough, to result in another day of widespread showers and
thunderstorms. PWs in place will again be greater than 2 inches,
above the 90th percentile according to NAEFS, combining with 1000
J/kg of CAPE to produce robust thermodynamics to support rainfall
rates of 2"/hr at times. There continues to be some uncertainty in
the coverage of convection, as well as placement, among the various
CAMs, somewhat lowering the confidence into D2. However, after
heavy rain anticipated D1, any additional rainfall D2 could quickly
become problematic and lead to instances of runoff and flash
flooding, especially in urban areas. The inherited MRGL and SLGT
risks were tailored slightly to encompass the highest probabilities
of 1+" and 3+" on D2.
Although not included in a risk area at this time, some of the
guidance has become a bit more aggressive with a wave of low
pressure developing along an inverted trough aligned to the east
coast of Florida. If this low were to develop a bit more rapidly or
track farther west, some heavy rain could move onshore the
northeast Florida coast before 12Z Wednesday.
...Four Corners...
A MRGL risk was expanded westward from the Central Plains to the
UT/NV/AZ borders with this update. The guidance has become more
aggressive with showers and thunderstorms blossoming during the
aftn/evening as forcing intensifies from broad divergence
downstream of a closed low filling and moving into the Desert
Southwest, producing ascent atop a wavering frontal boundary
positioned over the region. This lift will impinge into favorable
thermodynamics with PWs reaching above 0.75 inches into a bubble of
MUCAPE of 750-1000 J/kg. Mean storm motions will be weak, generally
around 5 kts, so with rainfall rates which have a 5-15% chance of
exceeding 1"/hr, these slow motions could result in locally as much
as 1" of rainfall in a short period of time. If this occurs over
sensitive soils, urban areas, or terrain features, instances of
flash flooding could result.
Weiss
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
842 PM EDT Mon Jun 2 2025
Day 3
Valid 12Z Wed Jun 04 2025 - 12Z Thu Jun 05 2025
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE UPPER MIDWEST, THE FOUR CORNERS, AND THE SOUTHEAST COAST...
...Four Corners...
Another active day of showers and thunderstorms expected as the
upper low over northern Baja fills and ejects northeast atop the
Four Corners. The accompanying ascent will move into continued
anomalous PWs which will exceed the 99th percentile according to
NAEFS. This will fuel widespread convection with rainfall rates of
0.5"/hr, or at times higher, likely., and storms will likely move
slowly beneath the upper trough, leading to a longer duration of
heavy rain. Although total rainfall will be modest in most areas
(24-hr probability from the ECENS/GEFS for 1" peaks around 25%),
where the heavy rain impacts sensitive terrain features or urban
areas, or should heavier rain impact the wetter soils in the CO/NM
high plains, instances of flash flooding could result.
...Mid-Mississippi Valley to Great Lakes...
The cold front from D2 will continue its trek eastward on
Wednesday, but will start to slow and become aligned more west to
east as its tail gets pulled northward by an approaching shortwave
over the Four Corners region. Shortwaves embedded within the flow
will continue to race northeast, especially from Missouri to
Michigan, which is where the greatest concentration of
thunderstorms is expected on D3. Storm motions along the front are
likely to be progressive, lifting off to the northeast on 0-6km
mean winds of 20-30 kts, but weaker Corfidi vectors aligned both to
this mean wind and the front suggests a potential for training. As
rainfall rates peak above 1"/hr within favorable thermodynamics,
this could result in stripes of heavy rainfall for which the
SREF/ECENS/GEFS ensembles indicate have a 20-30% chance of
exceeding 1", with some low-end probabilities (5% or less) of
exceeding 3". The MRGL risk was split, with the Central Plains
removed from the risk on D3 due to a more progressive front and
some NVA behind impulses, but also extended a bit northeast to
reach the Canadian border for isolated flash flood potential.
...Southeast Coast...
Guidance has become more aggressive with a wave of low pressure
potentially developing along an inverted trough shifting northeast
along the FL/GA/SC coasts. While NHC has placed a 10% probability
of tropical or sub-tropical development on this feature, regardless
of whether a circulation forms or not, there is increasing
confidence that heavy rain will spread across the FL Peninsula and
then rotate onshore the GA/SC coasts on Wednesday. With PWs in the
vicinity progged to exceed 2", above the 90th percentile,
supported by warm cloud depths that may exceed 15,000 ft, efficient
rainfall rates of 1-2"/hr will be likely in any showers/thunderstorms.
It is possible that the heaviest rainfall will remain just
offshore, but impressive moisture convergence from Jacksonville, FL
to Charleston, SC should support waves of heavy rainfall
regardless of development of this system, and although EFI is
modest, it does capture the region of greatest potential at this
time range. Additionally, plentiful tropical moisture across the
rest of the FL Peninsula and a shortwave continuing to pivot across
the Gulf could enhance rainfall over much of Florida Wednesday,
and the MRGL risk was expanded from Winyah Bay, along the coastal
plain of GA/SC, and across much of the FL Peninsula.
Weiss
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
302 PM EDT Mon Jun 2 2025
Heavy rainfall may impact portions of the Southeast Coast thanks
to a compact low under a closed weakness aloft. NHC is monitorring
development sub-tropical potential of this feature. Deepest
moisture
may stay offshore and uncertainty is high, but there is a chance
of some heavier rainfall along the coast. Accordingly, a Marginal
Risk of excessive rainfall shifts Thursday into Friday from far
northern Florida up through the coastal Carolinas as the low lifts
slowly up the coast in warm and moist Gulf Stream waters.
Numerous Showers and thunderstorms will focus along a slow-moving
and wavy front that will stretch from the Northeast and Ohio Valley
states down to the southern Plains. Gulf moisture pooling over the
region and shortwave/jet support will help prime the environment
for embedded heavy rain potential. Slow translation and deep
moisture could lead into some locally quite heavy totals, but local
focus details are proving quite varied in guidance from run to
run. Accordingly, a Day4/Thursday and Day 5/Friday WPC Marginal
Risk area for excessive rainfall and flash flooding remains
depicted for this region, with a smaller and less certain Slight
Risk area focused over Oklahoma for Friday. The southern trailing
tail of the elongated boundary will stall over the southern Plains,
eventually with baroclinicity rejuvenated more broadly again over
the central U.S. by ample northern stream system reinforcement that
may also act to spread main heavy rainfall focus across the Mid-
South and Tennessee Valley.
Meanwhile, enhanced rain and thuinderstorms will also spread
across the Northeast late week and the weekend as the northern
portion of the front advances, eventually shifting southward
through the Mid-Atlantic toward the Southeast later weekend into
next Monday.
Initially, below normal temperatures will be in place across the
Rockies and Plains on the backside of the frontal boundary. As the
frontal progresses, temperatures will begin to moderate by the end
of the week and into the weekend. Some of the warmest year to date
temperatures will be across much of the Eastern U.S. With daily
readings climbing into the upper 80s to lower 90s there will be a
Moderate level of HeatRisk. Care should be taken to protect
yourself from the hottest part of the day. Areas of south Texas
will see rising temperatures through the late week into the
weekend, cresting 105F by next weekend along the Rio Grande. This
may push heat index values over 110F.
Heat Safety -- take precautions such as increased water intake and
more time in air conditioned areas to avoid heat exhaustion and
heat stroke. See weather.gov/heat for more information on safety
tips and resources.
Schichtel/Campbell
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
302 PM EDT Mon Jun 2 2025
Heavy rainfall may impact portions of the Southeast Coast thanks
to a compact low under a closed weakness aloft. NHC is monitorring
development sub-tropical potential of this feature. Deepest
moisture
may stay offshore and uncertainty is high, but there is a chance
of some heavier rainfall along the coast. Accordingly, a Marginal
Risk of excessive rainfall shifts Thursday into Friday from far
northern Florida up through the coastal Carolinas as the low lifts
slowly up the coast in warm and moist Gulf Stream waters.
Numerous Showers and thunderstorms will focus along a slow-moving
and wavy front that will stretch from the Northeast and Ohio Valley
states down to the southern Plains. Gulf moisture pooling over the
region and shortwave/jet support will help prime the environment
for embedded heavy rain potential. Slow translation and deep
moisture could lead into some locally quite heavy totals, but local
focus details are proving quite varied in guidance from run to
run. Accordingly, a Day4/Thursday and Day 5/Friday WPC Marginal
Risk area for excessive rainfall and flash flooding remains
depicted for this region, with a smaller and less certain Slight
Risk area focused over Oklahoma for Friday. The southern trailing
tail of the elongated boundary will stall over the southern Plains,
eventually with baroclinicity rejuvenated more broadly again over
the central U.S. by ample northern stream system reinforcement that
may also act to spread main heavy rainfall focus across the Mid-
South and Tennessee Valley.
Meanwhile, enhanced rain and thuinderstorms will also spread
across the Northeast late week and the weekend as the northern
portion of the front advances, eventually shifting southward
through the Mid-Atlantic toward the Southeast later weekend into
next Monday.
Initially, below normal temperatures will be in place across the
Rockies and Plains on the backside of the frontal boundary. As the
frontal progresses, temperatures will begin to moderate by the end
of the week and into the weekend. Some of the warmest year to date
temperatures will be across much of the Eastern U.S. With daily
readings climbing into the upper 80s to lower 90s there will be a
Moderate level of HeatRisk. Care should be taken to protect
yourself from the hottest part of the day. Areas of south Texas
will see rising temperatures through the late week into the
weekend, cresting 105F by next weekend along the Rio Grande. This
may push heat index values over 110F.
Heat Safety -- take precautions such as increased water intake and
more time in air conditioned areas to avoid heat exhaustion and
heat stroke. See weather.gov/heat for more information on safety
tips and resources.
Schichtel/Campbell
