525
FOUS30 KWBC 140015
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
815 PM EDT Fri Jun 13 2025

Day 1
Valid 01Z Sat Jun 14 2025 - 12Z Sat Jun 14 2025

...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE
MID-SOUTH INTO THE TENNESSEE AND OHIO VALLEYS, CENTRAL
APPALACHIANS INTO THE MID-ATLANTIC, AND THE NORTHWEST GULF COAST...

...Mid-Atlantic...
2300 UTC Update -- Pulled the Slight and Marginal Risk areas a
little farther west (from the Atlantic Coast) based on the latest
observational trends along with recent HRRR/RRFS runs and the 18Z
HREF exceedance probabilities.

Hurley

Previous Discussion...Stalled frontal boundary stretching across
the Delmarva Peninsula towards the Upper Ohio Valley will combine
with increasing atmospheric moisture content (1.5-2.0" PWs by this
evening) to create efficient rainfall rates within thunderstorms.
The southerly mid-level flow will be aided by an upper low
currently analyzed over southern MO, but with troughing stretching
from the Midwest to the western Gulf. Convection is most likely to
trigger first across the Carolinas and the elevated terrain of the
Blue Ridge up through the central Appalachians. Mean column wind
speeds of 20 kts out of the west should promote some propagation of
storms, especially once a cold pool is established, but complex
terrain and areas right along the frontal boundary could exhibit
some training potential along with rainfall rates up to 2"/hr. The
inherited Slight Risk was maintained and expanded a bit westward to
encompass more of the sensitive Blue Ridge mountains of
central/northern VA. 12z HREF guidance depicts 30-50% chances for
3" totals within 6 hours this evening across central VA. This along
with the available moisture content and nearby frontal boundary
support the potential for scattered instances of flash flooding and
the potential for localized considerable impacts in the sensitive
terrain near the Blue Ridge as well as urban locations between
southern MD and northeast NC. However, some guidance (including the
12z HRRR and experimental 06z RRFS) are mostly void of excessive
rainfall coverage, which does prompt some uncertainty during the D1
period.


...Mid-Mississippi Valley and Lower Ohio Valley...
2300 UTC Update -- Based on the latest observational and guidance
trends, have nudged the Slight Risk area a bit farther east to
include more of the TN and OH Valleys.

Hurley

Previous discussion...Isolated flash flooding is still possible
across parts of central MO/IL underneath and near the low center,
but coverage of heavy rain does not seem widespread enough to
warrant a Slight Risk. Moisture and effective bulk shear will be
plentiful across much of the Mid-Missippi Valley and lower Ohio
Valley while ML CAPE will be sufficient for organized convection in
a number of areas. PW values of 1.75-2.0" will near the 90th
climatological percentile per the 00z ECENS. The risk percentage
for AR is in decline as the heavy rain signal appears better
elsewhere, but lowish flash flood guidance and the Ozarks should
prove sufficient for widely scattered to scattered flash flood
concerns, especially given the potential for storms to re-ignite
late tonight under the influence of an increasing low-level jet.
Flash flood guidance is many ares appears compromised by recent
rainfall (during the past week). Overall, the expectation is for
isolated to scattered instances of flash flooding and the greatest
concern located within urban and poor drainage locations.


...Northwest Gulf Coast...
Showers and thunderstorms are forecast to retrograde from southwest
LA across sensitive areas of Southeast TX this morning within an
area of low- level convergence and retreating/eroding instability.
This occurring after extreme rainfall amounts (7"+) impacted
south-central LA early this morning. Additional hourly rain
amounts to 2.5" with local totals to 5" are probable along the
northwest Gulf Coast due to sufficient effective bulk shear,
moisture, and instability, which would be most problematic where it
rained heavily on Thursday and within urban areas. 12z HREF
probabilities for greater than 5" in 6 hrs are 15-20% and scattered
throughout the region.


...Texas Panhandle and Caprock Region...
Dryline convection this evening is expected along much of the High
Plains, but also as far south as the Texas Panhandle and western
Texas where 1-1.25" PWs remain. 3-hr FFGs in the region are below
3" and have been somewhat wet as of the last month (100-200% of
normal for some locations). A Marginal Risk was added given the
potential for numerous thunderstorms, while progressing eastward
steadily, could merge and lead to brief periods of training.

...Northern WI/Michigan U.P....
Area of low pressure moving eastward through MN helps drive a
risk for heavy rainfall within narrow bands from MN across
northern WI Friday morning. Instability appears sufficient in spots
(500+ J/kg of MU CAPE) for pockets of organized convection capable
of heavy rainfall, but isentropic lift/low- to mid-level
frontogenesis is expected to aid heavy rainfall production as well.
Hourly amounts to 1.5" with local amounts to 3" are possible where
cells train. The inherited Marginal Risk was shrunk based on radar
and latest CAM trends.


...Northern Rockies/Western High Plains...
The Marginal Risk across Montana maintained along the western
interface of the deeper moisture and instability over much of the
Plains on the leading edge of a quasi-stationary upper level trough.

Snell/Roth


Day 2
Valid 12Z Sat Jun 14 2025 - 12Z Sun Jun 15 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR CENTRAL/EASTERN
VIRGINIA & ACROSS PORTIONS OF EASTERN KANSAS/OKLAHOMA...


...Mid-Atlantic...
Along a stationary front, another day of high moisture, sufficient
instability and effective bulk shear team up for heavy rainfall in
Virginia and specifically focus near southeast Virginia as the
front slides south by the evening hours. Widespread light to
locally moderate rainfall across the northern Mid-Atlantic should
tighten the thermal gradient in the region and potentially provide
a better focus for storms compared to Day 1. PWs are forecast to
remain near 2" and around the 90th climatological percentile. CAMs
depict widespread amounts of 2-4" possible with localized totals
potentially exceeding 5" (12z HREF probs for greater than 5" are
20-40%), with the greatest potential in southeast Virginia. Urban
areas and places with increasing soil saturation due to the
previous day of heavy rainfall would be most at risk for issues.

...Southern Plains, Southeast, and Tennessee/Ohio Valleys...
A deep layer cyclone drops southeast from IL into KY with time.
The system remains quite moist with sufficient effective bulk shear
along and near its associated fronts with greater instability,
particularly across portions of the Plains as mid-level capping is
increasing due to a strengthening 500 hPa ridge across NM, though
the cap is breakable especially near remnant MCVs from overnight
convection ejecting from the High Plains D1. Because of this
greater instability, a few pieces of guidance are quite wet
somewhere in the neighborhood of OK and KS, especially the 12z NAM,
00z CMC, and several CAMs showing maxima of 5-13". Hourly rain
amounts to 2.5" appear likely in this environment. Cell training
due to storms moving south- southeast down the stationary
instability gradient would be problematic if it occurs within a
long enough band over several hours. The inherited Slight Risk was
maintained with only minor adjustments. Should guidance converge
on wet solutions, further upgrades could occur.

Closer to the deep layer cyclone churning over the Ohio Valley,
slow moving convection and brief organized training is possible.
A more cellular convective mode is likely near the cyclone over the
Ohio Valley, where isolated flash flooding could occur. Along the
southern flanking inflow band, mean wind becomes more westerly and
parallel to developing convection across central and northern
AL/MS. This is an area that could warrant an upgrade to a Slight
Risk if more confidence arises in better convective organization
conducive for scattered flash flooding. At the moment, more
isolated and localized flooding is more probable.


...In and near the Iowa/Minnesota border...
A warm advection pattern returns to the region, bringing
precipitable water values up to 1.75" and sufficient effective bulk
shear and instability for organized convection. After rainfall on
Thursday and Friday, soils should be increasingly saturated/
compromised at this point. However, the guidance spread on the
heavy rain signal is quite large...best across southeast SD and
southern MN. While increasing warmth at 700 hPa is seen across the
central High Plains, any mid-level capping should be minimal.
However, the broad reservoir of instability to the southwest could keep
southward shifts in the guidance minimal between now and when the
convection materializes on Saturday. Hourly amounts to 2" and
local totals to 4" are possible, given the available ingredients
and potential lingering MCV to move eastward into the region from
D1. This could be from a combination of cell training and
occasional mesocyclone formation. The degree of the flash flood
threat would depend on whether or not urban centers received this
heavy rainfall or if/where soils were sufficiently compromised over
previous days within impacted areas.

Snell/Roth


Day 3
Valid 12Z Sun Jun 15 2025 - 12Z Mon Jun 16 2025

...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR MUCH OF VIRGINIA
AND INTO PARTS OF THE CENTRAL APPALACHIANS...

...Southern Mid-Atlantic States and Central Appalachians...
Another round of organized convection within a very moist
environment with sufficient effective bulk shear and instability is
expected near a stationary boundary. Like previous days, hourly
rain amounts to 2.5" with local amounts to 5" are possible.
However, by Sunday the influence of a strung-out upper low will
near the region and provide better forcing for greater coverage in
moderate to heavy rainfall. The previous Slight Risk was expanded
westward in order to encompass more of WV and western VA to account
for the heavy rain potential in sensitive terrain of the central
Appalachians on the western slopes given predominantly west-
southwesterly flow. Once again, flooding impacts will be
exacerbated in urban centers and what should be increasingly
saturated soils due to expected rainfall on Friday and Saturday.
Outside the CAM range for this outlook, but most global guidance
suggests at least 2-3" totals are likely to be common within the
Slight Risk. Given the potential soil sensitivity in this region
and the expected coverage of convection by Day 3, further upgrades
may be necessary.


...Northern Plains into the Midwest and Lower Mississippi Valley...
A "ring of fire" type of setup appears to be in the offing for
this region as ridging continues to build across NM, upper
troughing remains stagnant across the Pacific Northwest, and the
deep layer cyclone moves from KY towards WV. Temperatures at 700
hPa continue to warm somewhat across portions of the Rockies and
the central High Plains, strengthening the mid-level capping
inversion and increasing the instability available/forward
propagation odds for any organized convective complex that forms
around the ridge`s periphery. The region with the highest heavy
rain potential appears to be from the southern Plains/Midwest
southeastward near a possible Mesoscale Convective System. There is
significant model spread on location, keeping the risk level as
Marginal at this time. However, higher end potential exists for any
convection that can train along the instability gradient from
roughly eastern KS through AR, as seen in different ways on the
global solutions and experimental RRFS which show local maxima in
the 4-7" range. Should the guidance converge, an increased threat
level could be prudent.

Snell/Roth


Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt