FOUS30 KWBC 131150
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
750 AM EDT Fri Jun 13 2025

Day 1
Valid 12Z Fri Jun 13 2025 - 12Z Sat Jun 14 2025

...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE 
MISSISSIPPI VALLEY, NORTHWEST GULF COAST, & SOUTHERN MID-ATLANTIC STATES...

...12Z Outlook Update...
An expansion of the Slight Risk area was made over south-central 
Louisiana. Recent radar mosaic imagery depicts a slow-moving 
cluster of thunderstorms with very heavy rain rates that may 
persist across that area for several hours. Additional areas of 3-5
inch rainfall totals (with locally higher amounts) are possible. 
Refer to MPD 427 for additional information.

Cook

...Previous Discussion...

...Much of the Eastern half of the country... 
A slow-moving deep layer cyclone moves east across portions of the
Midwest from near the MO/KS/AR/OK broad border junction into IL. 
Moisture and effective bulk shear will be plentiful while ML CAPE 
will be sufficient for organized convection in a number of areas --
in the warm advection pattern just ahead of the low across 
portions of MO/IL and within its inflow bands/fronts across 
AR/Delta Region of MS and Tidewater VA/portions of the Potomac. All
three areas have Slight Risks, with the Midwest and Mid-Atlantic 
portions new for this update. 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. Flash flood
guidance is many ares appears compromised by recent rainfall 
(during the past week). Hourly rain amounts to 2.5" with local 
totals to 5" are most probable within the Slight Risk areas.

...Northwest Gulf Coast...
Showers and thunderstorms are forecast to retrograde from southwest
LA across sensitive areas of Southeast TX during the morning hours
within an area of low-level convergence and retreating/eroding 
instability. This is another area where hourly rain amounts to 2.5"
with local totals to 5" are more probable due to sufficient 
effective bulk shear, moisture, and instability, which would be 
most problematic where it rained heavily on Thursday and within 
urban areas.

...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 2" with local amounts to 4" are possible where 
cells train.

...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.

Roth


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

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN AND NEAR
VIRGINIA & ACROSS PORTIONS OF THE SOUTHERN PLAINS...

...Southern Plains, Southeast, Tennessee & Ohio Valleys, & the
Mid-Atlantic States... 
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. Because of this greater instability, a few 
pieces of guidance are quite wet somewhere in the neighborhood of 
OK and KS, where the 00z GFS, 00z NAM, and especially the 00z 
Canadian are quite wet, 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. An upgrade to a Slight Risk 
was made here at the expense of AR due to the significant/increased
potential to its west. Should guidance converge on wet solutions, 
further upgrades could occur.

Along the system's stationary front to the east, another day of
high moisture, sufficient instability and effective bulk shear team
up for heavy rainfall in and near Virginia. Hourly rain amounts to
2.5" with local amounts to 5" are most probable within the new 
Slight Risk area. Urban areas and places with increasing soil 
saturation due to the previous day of heavy rainfall would be most 
at risk for issues.

...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. Played it cautious and 
introduced a Marginal Risk for the heavy rain potential on 
Saturday. Hourly amounts to 2" and local totals to 4" are possible,
given the available ingredients. 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.

Roth


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

...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS IN AND NEAR THE VIRGINIAS...

...Southern Mid-Atlantic States...
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. A new 
Slight Risk area was added to account for both the heavy rain 
potential in urban centers and what should be increasingly 
saturated soils due to expected rainfall on Friday and Saturday.

...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 
00z NAM, 00z UKMET, and 00z Canadian Regional solutions which show 
local maxima in the 4-7" range. Should the guidance converge, an 
increased threat level could be prudent.

Roth

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