345
AGUS74 KWCO 051505
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
915 AM CST WED FEB 5 2025

.Synopsis...
Atmospheric river will continue impacting California through late this week...
Potential for isolated flooding across the Ohio River Valley...

.Discussion...

.California...
Minor to isolated major river flooding is ongoing this morning across
portions of Central and Northern CA and is forecast to persist through day
2 (Thu), though the Pit River near Canby, CA should remain in flood through
day 3 (Fri). Showers will linger across portions of Northwest CA through
day 1 (Wed), these are not expected to have any impact hydrologically.
Another round of rainfall and mountain snow is forecast starting on day 2
(Thu) as a colder low pressure system impacts the state. Current QPF totals
from WPC range from 1 - 2", with locally higher totals possible in
favorable upslope areas and lower snow levels forecast. Renewed rises on
area streams and rivers will be possible, along with some renewed flooding.
Topsoils are generally wet, but not saturated across the region (0 - 10 cm,
NASA SPoRT), suggesting some isolated runoff will also be possible,
particularly if any higher rain rates materialize ( 0.5"/hr). Rainfall
will sag southward into coastal south-central CA late on day 2 (Thu) and
into early day 3 (Fri). Another break in the rain is expected starting
around midday on day 3 (Fri) and dry weather will continue through day 6
(Mon), before another low pressure system impacts the region yet again on
day 7 (Tue).

.Tenneesse and Ohio River Valleys...
Rainfall through day 2 (Thu) and again this weekend will bring the
potential for isolated flooding impacts to the region with 7-day QPF totals
of 1 - 4" (WPC). Some of that QPF across the northern portions of the
region will be of the winter variety. Recent snowmelt of 1 - 2" in eastern
WV over the past 48 hours (SNODAS) appears to have had minimal impact on
streamflows based on analysis of many of the USGS streamgages. Additional
melt will occur on day 3 (Fri), with SNODAS indicating 0.5 - 1.5" of
snowmelt will be possible across the Ohio Valley, particularly in eastern
WV. Soils across KY, WV and OH are wet throughout much of the profile (65 -
95% RSM, 10 - 40 cm, NASA SPoRT) and streamflows are above normal to much
above normal (USGS), indicating a hydrologic system primed for quick
responses. Conditions are less conducive across the Tennessee Valley.
Ensemble river forecasts (MMEFS) show widespread minor river flooding will
be possible across the Ohio Valley, with some isolated moderate river
flooding possible across portions of eastern KY and WV. Overall, the threat
for flooding may be minimal with the first round, increasing this weekend,
and again next week with the additional rounds of rainfall.

//JAW

$$