316
AGUS74 KWCO 061508
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT FRI JUN 6 2025

.Synopsis...
Widespread flooding, including locally considerable flash and river
flooding, remains possible across the Central and Southern Plains into the
Ozarks... Isolated flash flooding possible in the Lower Mississippi Valley
into the Southeast... Isolated flash and small stream flooding possible in
the Northeast and the Lower Ohio Valley into Missouri...

.Central and Southern Plains into the Ozarks...
An active weather pattern continues to bring the threat of flash and urban
flooding, along with possible river flooding through the weekend, to the
region, some of which could be locally considerable. Portions of south KS,
OK, TX Panhandle, north TX, and the Ozarks received 1 - 2" of rainfall
yesterday into this morning while some areas received greater than 3"
(MRMS). Rainfall is currently pushing through the Ozarks as the system
traverses eastward. This recent rainfall combined with fairly widespread 2
- 3"+ totals over the past 7 days (RFC QPE) has left the region`s soils
wetter than normal and streamflows running high. Currently, OK, extreme
southern KS, and the MO Ozarks have the greatest relative soil moisture in
the near surface soils at greater than 65% with the remainder of the region
at least near 50% (NASA SPoRT). Rivers and streams are still running above
the 75th percentile for historic flows with many running above the 90th
percentile, keeping the region vulnerable to any new rainfall.

Rainfall will return early tomorrow morning just out of range of the
National Water Model (NWM) Short Range Forecast (SRF). The GFS-forced NWM
Medium Range Forecast (MRF) appears to be the more bullish between the two
NWM MRF services with fairly robust stream/river responses across southeast
OK and portions of TX, suggesting the potential for flash and urban
flooding; however, the NBM-forced version appears to show more modest
responses overall. In addition, the overall variability between global
models in QPF magnitude, placement, and timing appears to vary
significantly which adds a great deal of uncertainty to when and where the
impacts will be. River ensembles are starting to indicate the potential for
river rises across the region including the Trinity, Sabine, and Neches
river basins in TX and tributaries of the Red River in OK/TX including
minor to moderate river flooding over the next 7 days. The bottom line is
that all the models generally have heavy rainfall forecast across most of
north TX, OK, and into the Ozarks which will bring flash, urban, and river
flooding impacts over the next several days.

Considerable river flooding continues across the Lower Middle Arkansas,
Upper Neosho, and Upper Osage basins in KS after recent heavy rainfall.
Most rivers have crested or are currently cresting in moderate flood;
however, flooding is expected to continue through the weekend.

.Lower Mississippi Valley into the Southeast...
Isolated flash flooding may be possible for portions of western TN and
northern MS/AL on day 2 (Sat). Recent rainfall has left upper-layer soils
across the region wet but not saturated, allowing for better absorption of
additional rainfall into the system and reducing the overall flood threat.
However, periods of higher rainfall rate could still lead to some flooding
impacts.

.Northeast...
Isolated flash and small stream flooding will be possible across the
Adirondacks (NY), Green (VT), and White Mountains (NH) through tomorrow due
to locally heavy rainfall, with totals of 2"+ expected (WPC, HRRR). Soil
moisture is near normal; however, many streams are running on the higher
side suggesting some vulnerability to out-of-bank flows on smaller streams
if heavy or repeating rounds of rainfall were to materialize. Signals from
the HRRR-forced NWM SRF high flow magnitude service have been increasing in
coverage and magnitude in recent runs, and now show potential for 20 - 4%
annual exceedance probabilities (AEPs) in the White Mountains of NH.
Rapid-onset-flooding (ROF) probability signals have been creeping up in
recent runs as well, and are expected to continue to strengthen as the
event draws near.

.Lower Ohio Valley into Missouri...
Potential for isolated flash and small stream flooding exists over parts of
the Lower Ohio Valley/Missouri through today. Rainfall totals of 1 - 4"
have fallen in the last 48 hours and an additional 1 - 2"+ is expected
(WPC, HRRR). Upper-layer soils are on the wetter side (60 - 75% RSM, 0 - 10
cm, NASA SPoRT) and streams are running generally above normal, suggesting
some hydrological sensitivity leading into this next round of rainfall. The
HRRR-forced NWM SRF is signalling some scattered stream reaches with AEPs
in the 20 - 4% range, supporting the potential for scattered out-of-bank
rises. Signals from the 12-hour ROF probability service are mostly around
25%, but will likely increase and spread out in areal coverage as the bulk
of the QPF comes into range.

//Smith



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