WCO issues Area Hydrological Discussion (AHD) at Sep 27, 4:48 AM CDT353
AGUS74 KWCO 270955
AHDNWC
Area Hydrological Discussion #284 - EXPERIMENTAL
NWS National Water Center - Tuscaloosa, AL
448 AM CDT Fri Sep 27 2024
WHAT: Locally considerable flash, urban, and river flooding
WHERE: Northeastern Alabama, northwestern GA, and central Tennessee
WHEN: Though this afternoon
FORECAST RAINFALL AND ANTECEDENT CONDITIONS...
QPF: 2 - 4", locally higher (HRRR)
Rates: 1 - 2.5"/hr, locally higher (HRRR)
Soils: 75% - 100% (NASA SPoRT)
DISCUSSION...
Rounds of heavy rainfall associated with Helene over the area of
concern may lead to locally considerable flash, urban, and small
stream flooding impacts, particularly in heavily populated
metropolitan areas in central Tennessee through central Georgia
through this afternoon. Top layer soils are at or near saturation and
stream flows are rapidly increasing due to enhanced runoff.
Additionally, significant river flooding is ongoing or forecast in
Atlanta, GA which will further compound the overall flooding threat.
The NWM Short-Range Forecast continues to highlight the potential for
rapid-onset flooding at 50 - 75% probabilities from Nashville, TN
through Atlanta, GA. Annual-exceedance probabilities (AEPs) are 50 -
20% throughout the area of concern, with a pocket of AEPs down to 2%
for Murfreesboro, TN through Chattanooga. Peak flows will occur over
the next 4 - 12 hours and may take quite some time before they
recede. This means even as rainfall moves out of the areas, the
threat for small stream flooding will linger as flows are routed
downstream.
GRAPHICAL REPRESENTATION weather.gov/owp/operations-ahd
Additional National Water Center products are available at
weather.gov/owp/operations
//JAC
ATTN...WFO...PAH...LMK...BMX...HUN...OHX...GSP...RNK...MRX...FFC...CAE...ILM...RAH
ATTN...RFC...ORN...TIR...ALR...WPC
Source:
WCO issues Area Hydrological Discussion (AHD) at Sep 27, 4:48 AM CDT---------------
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