Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
833 PM EDT Thu Jun 5 2025
Day 1
Valid 01Z Fri Jun 06 2025 - 12Z Fri Jun 06 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTH-CENTRAL PLAINS...
...Central to Southern Plains...
A broad area of convection this evening across the High Plains
down into Southwest TX will account for 3 areas of focus for the
remainder of the D1 ERO. The most significant of the heavy rain
prospects is currently in the initial phase with a strong
mesocyclone over Southeast CO likely to propagate downstream and
grow upscale with aid from a budding nocturnal LLJ positioned
across KS/OK and points south. 50+ kt deep layer shear will help
maintain a relevant kinematic environment capable of enhancing and
sustaining an eventual MCS moving southeast from Southwestern KS
down through Northern OK during the overnight period, mainly
following the northern edge of a theta_E gradient situated across
the above zone. Despite forward momentum of the eventual MCS,
embedded convective cores will be capable of locally enhanced
rainfall rates of 1-2"/hr with totals likely reaching 2-3" in the
path of the MCS with some 3-5" totals possible over the upwind side
of the complex. For more information on this threat, please see MPD
#372.
Across the Texas Caprock down into Southwest TX, a few supercells
will eventually grow upscale and migrate slowly to the east leading
a trail of heavy rainfall in their paths over the next 3-6 hrs
before waning overnight. The conglomeration over Southwest TX will
maintain the greatest footprint in heavy rain coverage with the
highest flash flood threat likely over the terrain areas
encompassing the Davis and Glass Mtns, and along the I-10 corridor
situated in the Stockton Plateau. Multiple flash flood warnings are
already in effect for those areas with totals likely breaching 2"
in several areas across the above zones by the end of the event.
These setups can be tricky and prolonged heavy rain threats beyond
current CAMs inference are unfortunately common as cold pool
convergence can maintain cell clustering longer than normal.
The zone across CO/KS/OK maintained the previous SLGT risk with a
minor extension on the western flank of the risk. The MRGL was kept
for much of West TX with the best flash flood risks likely over the
Caprock of TX into Northwest TX near the Red River, and over
Southwest TX within the Davis/Glass Mtn area and adjacent Stockton
Plateau.
...Southern Great Basin into the Central Sierras...
Elongated surface trough and attendant surface low across the
Southern Sierras will maintain a positively buoyant environment
within the confines of the Sierras down into the Southern Great
Basin (See MPD #373 for details on the setup across the Great Basin).
Visible satellite over the West indicates two distinct surface
boundaries bisecting Southern NV into Southern UT and across
Northern AZ to the Colorado River Basin at the CA/AZ border.
Mesoanalysis across the area indicates a relative instability
maximum within that portion of the Desert Southwest with SBCAPE
~500-1000 J/kg aligned over Northwestern AZ into Southern NV, a
stripe over the Central Sierra's where locally heavy rainfall is
already producing some flash flood concerns in the Foothills. The
threat for convection lingering between 01-04z is pretty high when
assessing hourly CAMs, and projects well considering the
environment in place. This is a signature typically seen as one
that can prolong heavy rain potential over the region, an area very
susceptible to flash flooding concerns with stronger convective
cores. A MRGL risk was maintained over the Southern Great Basin
with an extension up through the Central Sierra's given the local
instability maximum situated over the area with ongoing
thunderstorms.
..Ohio Valley into the Northern Mid Atlantic...
Area convection continues to fire within the terrain across WV and
Western PA with a tongue of instability remaining along and ahead
of a cold front analyzed from the Ohio Valley into the Northeast.
Shear remains confined over NY State with less deep layer shear as
you move south leading to the strongest thunderstorm activity
situated across Southern NY state. A quick 1-2" will be plausible
within the environment in place this evening with a trend in less
coverage anticipated after 03z. A shortwave currently analyzed over
the Mid-Mississippi Valley will slide eastward overnight with a
better dynamical input positioned across the Eastern Ohio Valley
early tomorrow morning as CAMs initiate another round of convection
across OH and Western PA after 09z. Despite a weaker surface based
instability prog over the area, there's enough of a combination of
boundary layer buoyancy and mid-level ascent to enhance area
convection capable of isolated flash flood potential during the
early morning hours. As a result, the previous MRGL risk was
maintained within that zone of Southern OH, extending northeast
into Southern NY State with an alignment closely tied to the cold
front progression this evening.
Kleebauer
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
833 PM EDT Thu Jun 5 2025
Day 2
Valid 12Z Fri Jun 06 2025 - 12Z Sat Jun 07 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF
OKLAHOMA INTO THE KANSAS, OKLAHOMA, MISSOURI, ARKANSAS BORDER
REGION...
...2030Z Update...
...Oklahoma into the OK/KS/MO/Ar border area...
Ongoing convection associated with an MCS passing through eastern
Oklahoma during the day 1 period may continue into day 2 Friday
morning, with a continued risk for locally heavy rainfall and
scattered flash flooding. Otherwise, the previous forecast remains
on track, and similar to day 1 in both nature and location, with
the expectation that afternoon/evening thunderstorms developing
ahead of a triple point low located over the central/southern High
Plains will grow upscale into an MCS. This system should track
east-southeastward through Oklahoma late Friday night/early
Saturday with an attendant risk for locally heavy rainfall rates of
1-2" and totals of 2-4" leading to scattered instances of flash
flooding.
...Mid MS, Ohio, and Tennessee Valleys...
A complex forecast is apparent for this region given the potential
for an ongoing and/or influence from an overnight MCS Thursday
night/Friday morning. Hi-res guidance suggests that an MCS
developing over the central/southern High Plains and passing
eastward through the central/southern Plains Thursday night/Friday
morning will continue eastward into the Middle
Mississippi/Ohio/Tennessee Valleys Friday afternoon. Any sustained
convection may also be augmented by redevelopment along associated
outflow boundary(s), which would help to focus what would be a more
nebulous distribution of storms and lead to more widespread,
higher rainfall totals supportive of a greater flash flood threat.
Regardless of the influence of this MCS, the prior forecast remains
on track. The presence of an anomalously moist, unstable airmass
along and ahead of the quasi-stationary frontal boundary will be
enough to trigger scattered to widespread thunderstorms capable of
locally heavy rainfall and at least isolated flash flooding.
...New England...
A frontal wave forming along a cold front draped through southern
New England westward through the Lower Great Lakes will help
encourage a moist, southerly return flow from the Atlantic
northward through New England during the day Friday. Multiple
shortwave passages and a warm conveyer belt setup will lead to
multiple rounds of thunderstorms producing locally heavy rainfall.
An axis with a potentially higher threat was noted from the eastern
Catskills/greater Albany northeastward through northwestern
Massachusetts, southern Vermont, and central New Hampshire,
particularly given the sensitivity of the more complex terrain
through the region. However, with the latest hi-res guidance still
relatively localized on higher totals, have held at a Marginal Risk
for now pending a confirmation/increase in potentially more
widespread, higher totals.
Putnam
...Previous Forecast...
...Oklahoma into the OK/KS/MO/Ar border area...
Another round of shortwave energy forecast to drop east
southeastward from the Central Rockies into the Central to Southern
Plains Friday into Friday night/early Saturday. This will support
potential for another round of organized convection in the vicinity
of the west to east oriented frontal zone. PW values along this
front will remain above average...2+ standard deviations above the
mean, supporting heavy precip potential. There is fairly good model
consensus for an axis of heavy rains along this front across much
of OK into the OK/KS/MO/AR border region. Only some slight changes
to the previous slight risk area to reflect this qpf axis
consensus.
...Southern Great Basin into the Central to Southern Rockies...
Not a lot of changes expected to the large scale flow from day 1
across the southern Great Basin into the Central Rockies. PW values
forecast to remain above average with additional shortwave energy
moving across the region in the west south west flow aloft. This
should support another day of widespread scattered convection and
localized heavy rain and isolated runoff issues. The marginal risk
was extended back across these areas to be more similar to the day
1 period given the similar overall conditions day 2.
...Mid MS Valley, OH Valley into New England...
Similar to the day 1 period, an axis of above average PW values
will stretch along the slow moving front stretching from the Mid MS
Valley, OH Valley into New England. There is good model consensus
on a broad region of moderate to locally heavy precip amounts along
this front. Only some minor changes to reflect the latest model
qpf axis consensus made to the previous broad marginal risk area
across these regions.
Oravec
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
833 PM EDT Thu Jun 5 2025
Day 3
Valid 12Z Sat Jun 07 2025 - 12Z Sun Jun 08 2025
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE LOWER
ARKANSAS VALLEY, LOWER MISSISSIPPI VALLEY INTO THE LOWER TENNESSEE
VALLEY...
...2030Z Update...
The prior forecast remains on track with respect to the Southern
Plains eastward through the Lower Mississippi and Tennessee Valleys
with only minor areal adjustments based on the latest 12Z
guidance. Further north, forecast rainfall totals have come down in
New England, with guidance now suggestive of only some relatively
isolated totals around 1". Have maintained a Marginal Risk for now
but given the lower totals and more progressive nature of the cold
front Saturday, a threat for even isolated flooding may not
ultimately materialize and will be re-evaluatd in subsequent
outlooks.
Putnam
...Previous Forecast...
The second round of height falls moving into the Central to
Southern Plains day 2 will continue to push east southeast toward
the Mid to Lower MS Valley, OH and TN Valleys. Upper difluence is
forecast to be well defined Saturday into Saturday night/early
Sunday in an axis of above average PW values that will remain along
the west to east oriented frontal boundary across these areas.
This should support potential for another round of organized
convection along this front. There is some spread with the qpf
axes, but consensus that heavy amounts are possible along this
front. The previous slight risk area was expanded eastward
considerably from eastern OK, across much of AR, western TN and
northern MS.
...Northern New England...
A sharpening northern stream trof will push surface low pressure
across northern New England on Sunday. There is fairly good model
consensus for moderate to locally heavy precip totals across
northern New England. Only some slight changes to the previous
marginal risk area, extending it into all of northern Maine to
cover the model qpf spread.
Oravec
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
213 AM EDT Fri Jun 6 2025
A trailing frontal boundary draped across the South will provide
focus for numerous showers and thunderstorms through much of next
week. Moderate to locally heavy rainfall is possible and the Days 4
and 5 Excessive Rainfall Outlooks (valid Monday and Tuesday)
highlight this threat with broad marginal risks stretching from the
southern High Plains, across Texas and the lower Mississippi
Valley, and into parts of the Southeast. There remains enough
disagreement in exact placement of heavy rainfall to preclude a
slight risk, but it is possible one will be needed somewhere as
models come more in line, especially for areas that have seen
recent heavy rainfall. The northern portion of this boundary will
be quicker to move through the East, but there could be a heavy
rainfall threat over parts of interior New England and so a
marginal risk area was added to the Day 5/Tuesday ERO tonight.
Elsewhere, precipitation will increase across the Northern Rockies
and into the Northern Plains ahead of a frontal system the second
half of the week.
Much above normal temperatures will continue from the weekend into
early next week for the Northwest, with anomalies of +20-25F
likely. This should equate to a moderate to major heat risk for
parts of this region along with widespread record highs through at
least Monday. Temperatures and heat risk should moderate Tuesday
and Wednesday, but remain slightly above normal. Major to locally
extreme heat risk will continue across South Texas as well into
Monday, becoming much less extreme by Tuesday as an upper level
shortwave moves into the region. By next Thursday and Friday, most
of the country will be near or within a few degrees of normal.
Santorelli
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
213 AM EDT Fri Jun 6 2025
A trailing frontal boundary draped across the South will provide
focus for numerous showers and thunderstorms through much of next
week. Moderate to locally heavy rainfall is possible and the Days 4
and 5 Excessive Rainfall Outlooks (valid Monday and Tuesday)
highlight this threat with broad marginal risks stretching from the
southern High Plains, across Texas and the lower Mississippi
Valley, and into parts of the Southeast. There remains enough
disagreement in exact placement of heavy rainfall to preclude a
slight risk, but it is possible one will be needed somewhere as
models come more in line, especially for areas that have seen
recent heavy rainfall. The northern portion of this boundary will
be quicker to move through the East, but there could be a heavy
rainfall threat over parts of interior New England and so a
marginal risk area was added to the Day 5/Tuesday ERO tonight.
Elsewhere, precipitation will increase across the Northern Rockies
and into the Northern Plains ahead of a frontal system the second
half of the week.
Much above normal temperatures will continue from the weekend into
early next week for the Northwest, with anomalies of +20-25F
likely. This should equate to a moderate to major heat risk for
parts of this region along with widespread record highs through at
least Monday. Temperatures and heat risk should moderate Tuesday
and Wednesday, but remain slightly above normal. Major to locally
extreme heat risk will continue across South Texas as well into
Monday, becoming much less extreme by Tuesday as an upper level
shortwave moves into the region. By next Thursday and Friday, most
of the country will be near or within a few degrees of normal.
Santorelli
