AGUS74 KWCO 150053
AHDNWC

Area Hydrological Discussion #042 - EXPERIMENTAL
NWS National Water Center - Tuscaloosa, AL
745 PM CDT Tue Apr 14 2026

POTENTIAL IMPACTS: Flash, urban, and small stream flooding likely
WHERE: Central Michigan
WHEN: Through early Wednesday morning

FORECAST RAINFALL AND ANTECEDENT CONDITIONS?
QPF: 1 - 2", locally higher (HRRR)
Rain Rates: 1 - 2"/hr (HRRR, Observed)
Relative Soil Moisture: Wet to Saturated (NASA SPoRT)

DISCUSSION...
Heavy rainfall is expected to move into central Michigan through the
evening into the overnight hours, bringing with it the potential for
flash, urban, and small stream flooding. Considerable flood impacts
may be possible in areas with soils near saturation and existing high
streamflows, leaving little to no storage space for new
precipitation. The nocturnal nature of this event will increase the
potential for flood impacts, especially in urban areas and low water
crossings.

The HRRR-forced National Water Model (NWM) has been very consistent
placing widespread probabilities of rapid onset flooding (greater
than 75%) over the area of concern through the night into the early
morning hours. Annual exceedance probabilities (AEPs) on the current
deterministic run of the NWM (22Z HRRR, 23Z NWM) show widespread AEP
values below 10% (with many areas down to 2%), suggesting significant
streamflows are possible. However, much of the region already has
elevated streamflows, and the forecast unit discharge values from the
NWM overall have fairly low responses. This suggests more isolated
flash flood responses (limited to where the heaviest rainfall totals
occur) but overall streamflows will increase significantly though the
overnight hours due to the widespread rainfall.

GRAPHICAL REPRESENTATION: weather.gov/owp/operations-ahd

Additional National Water Center products are available at:
weather.gov/owp/operations

//Fontenot

ATTN...WFO...IWX...GRR...DTX...APX
ATTN...RFC...MSR...WPC