Daily Analysis

PRE-ANALYSIS (per-gauge facts; QPE timestamps converted Z→CDT, −5 h):

• Boxley (height): (a) first 2.45 ft @00:00; (b) max 2.45 ft @00:00; (c) last 2.34 ft @23:30; (d) intraday low 2.32 ft @20:30; (e) low→peak +0.02 ft (2.32→2.34, 20:30→21:45, ~1.25 hr); (f) Boxley zone 1-hr QPE peak 0.455" @22:02 CDT — gauge response pending (only 1.5 hr of post-peak data; pool-fill, no peak yet).
• Ponca (cfs): (a) 159 @00:00; (b) 431 @22:00; (c) 297 @23:30; (d) low 137 @17:30–20:00; (e) +294 cfs (137→431, 20:00→22:00, ~2 hr); (f) Whiteley 1-hr QPE peak 21:02 CDT → Ponca peak 22:00 = 0.97 hr.
• Pruitt (height+cfs): (a) 4.33 ft / 290 cfs @00:00; (b) 10.11 ft / 4150 cfs @23:30 (study-record both); (c) same @23:30; (d) low 4.18 ft / 246 cfs @16:30; (e) +5.93 ft / +3904 cfs (16:30→23:30, 7 hr, still rising); (f) Cove Cr 1-hr QPE peak 18:02 CDT → Pruitt 23:30 = 5.47 hr (peak not yet reached).
• St. Joe (height+cfs): (a) 4.76 ft / 696 cfs @00:00; (b) 5.02 ft / 834 cfs @22:45; (c) same @22:45; (d) low 4.52 ft / 580 cfs @15:30; (e) +0.50 ft / +254 cfs (15:30→22:45, 7.25 hr, still rising); (f) St. Joe zone 1-hr QPE peak 1.221" @22:02 — gauge only just beginning to rise; major Richland/Cave/Big propagation pending overnight.
• Harriet (height+cfs): (a) 4.73 ft / 901 cfs @00:00; (b) 7.19 ft @22:00 / 3500 cfs @22:00; (c) 7.11 ft / 3400 cfs @22:45; (d) low 4.58 ft / 786 cfs @15:30; (e) +2.61 ft / +2714 cfs (15:30→22:00, 6.5 hr); (f) Water Cr 1-hr QPE peak 16:02 CDT → Harriet peak 22:00 = 5.97 hr.
• Richland (height): (a) 1.13 ft @00:00; (b) 8.35 ft @22:30; (c) 7.66 ft @23:00; (d) low 1.08 ft @14:00–16:45; (e) +7.27 ft (1.08→8.35, main surge 16:45→22:30); (f) Headwaters Richland 1-hr QPE peak 22:02 CDT → gauge peak 22:30 = 0.47 hr (anomalously short — see below).
• Bear Creek (height+cfs): (a) 2.15 ft / 21 cfs @00:00; (b) 8.72 ft / 7580 cfs @23:15 (study-record both); (c) same @23:15; (d) low 2.13 ft / 19.8 cfs @14:00; (e) +6.59 ft / +7560 cfs (still rising); (f) Headwaters Bear 1-hr QPE peak 22:02 CDT → peak pending.

1. PRECIPITATION SUMMARY

A major mid- and lower-basin-concentrated convective complex — the spatial inverse of Event 19 (upper-basin-only). Basin-max 24-hr QPE 3.792" (Richland zone). Concentration cores: - Richland zone 3.792" — Headwaters Richland 3.867" (1.269"/hr), Falling Water 3.716" (1.483"/hr), Outlet Richland 3.864". - Bear Creek zone 3.191" — Headwaters Bear 3.766" (1.695"/hr, study-area peak intensity today). - Cave Creek 3.414" (1.071"/hr); Headwaters Big Creek 3.361"; Calf Creek 3.315"; Big Creek-Buffalo 1.789". - Harriet zone 2.532" — Water Cr 3.309" (1.377"/hr), Tomahawk 3.083". - Pruitt zone 2.339" — Cove Cr 2.751" (0.907"/hr) bullseye, Hoskin 1.927". - Ungauged 2.606" — Hickory 3.390", Davis 2.356". - Upper basin much lighter: Boxley 0.753", Ponca 0.729" (Whiteley 1.494" the local max).

Timing migrated SW→NE through the evening: Harriet-zone cells peaked ~16:02 CDT, Cove/Pruitt ~18:02 CDT, Richland/Bear/Cave/Big terminal burst ~22:02 CDT. Antecedent moist-but-not-saturated: Richland 7-day 1.38–1.41", Bear 0.94–0.97" (driest zone), Cave 1.495", Pruitt 2.18–2.68".

2. GAUGE RESPONSES

Six of seven gauges responded; this is a flood-scale event (Event 20), still developing at the 23:30 data cutoff.

• Pruitt — FLOOD, study-record. 4.18→10.11 ft, 246→4150 cfs (>2000 flood threshold). Highest Pruitt height AND discharge of the entire study (exceeds Event 15's 8.55 ft/2610 and Event 19's 7.98 ft/2130). Explosive terminal rise 4.80→10.11 ft in 30 min (23:00–23:30). Source: local Cove Cr 2.751" surface response + modest Ponca-zone routing.
• Richland — far above Upper Richland High (6.0). Peak 8.35 ft (4th Upper-Richland-runnable event of study; near Event 15's 8.89 ft). Source: Headwaters Richland 3.867" / Falling Water 3.716".
• Bear Creek — study-record. 2.13→8.72 ft / 7580 cfs and still rising. Crushes prior Bear high (Event 15, 3090 cfs). Source: independent Headwaters Bear 3.766" — NOT propagation (own-zone rain).
• Harriet — +2.61 ft to 7.19 ft / 3500 cfs (37% of 9370 flood threshold). First pulse from direct Harriet-zone rain (Water/Tomahawk).
• Ponca — +294 cfs to 431 cfs (flashy Whiteley 1.494" response, already receding to 297).
• St. Joe — only +0.50 ft to 5.02 ft / 834 cfs (Optimal). The mainstem trunk has not yet received the Richland/Cave/Big flood pulse — that propagation arrives overnight.
• Boxley — essentially flat (+0.02 ft); 0.753" on a drying-moderate antecedent is in the pool-fill delay window; response pending.

Signal separation: Richland surged hugely (NOT flat) → St. Joe's developing rise will be Richland-sub-basin-driven (HUC12s 0306/0307/0308) plus Cave/Big direct. Bear Creek surged independently while Harriet rose → Harriet response is compound (direct Harriet-zone first pulse + Bear-confluence + upstream propagation to follow). Textbook compound-source signature, like Event 8.

3. RAINFALL-RESPONSE PAIRS

Bear Creek — Headwaters Bear QPE peak 22:02 CDT; gauge still rising at cutoff. Transfer (to 23:15) 6.59 ft / 3.191" = 2.07 ft/in at low pre-event stage (2.13 ft). This CONFIRMS Event 16's 2.08 ft/in (wet + low pre-event stage, study high). Antecedent differs (today moist-low 0.97" 7-day vs Event 16 saturated) — yet ratio is identical, showing stage-on-rating-curve dominates antecedent for Bear when forcing is extreme and stage starts near baseflow. Notably this defeats the Event-11 dry-damping (0.09–0.17 ft/in): 3.77" of forcing on low stage overran the structural absorption. <30% from Event 16 — no refinement needed, strong confirmation.

Richland — Headwaters Richland QPE peak 22:02 → gauge peak 22:30 = 0.47 hr. Transfer 7.27 ft / 3.792" = 1.92 ft/in. The lag is anomalously short vs prior Richland (3–5 hr moist, Events 10/13): the QPE peak-hour bin landed concurrent with the gauge's flashy terminal surge — forcing and response were essentially simultaneous in the final hour. I treat the 0.47 hr as a concurrent-forcing artifact, low confidence; effective onset-to-peak was ~3 hr (rise began ~19:00, surged to 8.35 by 22:30). Transfer 1.92 ft/in sits between Event 13's 0.90 (moist) and Event 15's 2.69 (out-of-bank) — consistent with approaching channel-geometry nonlinearity at 8.35 ft on moist (1.41" 7-day) antecedent.

Harriet — Water Cr QPE peak 16:02 → Harriet peak 22:00 = 5.97 hr. Transfer 2.61 ft / 2.532" = 1.03 ft/in (or 1072 cfs/in). Matches prior Harriet moist range (~0.8–1.4 ft/in). Antecedent moist (Harriet HUCs 0.86–1.42"). In-range, no flag.

Pruitt — Cove QPE peak 18:02 → Pruitt 23:30 (still rising) = ≥5.47 hr. Transfer (height, to cutoff) 5.93 ft / 2.339" = 2.54 ft/in — well above the antecedent-independent ~1.4 ft/in baseline, but this is compound (local Cove surface + Ponca-zone routing) and at out-of-bank flood stage, so per-inch height transfer is inflated by channel geometry, exactly as Bear/Richland show. Flag noted; not directly comparable to the in-bank ~1.4 ft/in regime.

Ponca — Whiteley QPE peak 21:02 → Ponca peak 22:00 = 0.97 hr, +294 cfs from a flashy 1.494" sub-zone burst. Fast small-tributary response.

4. DOWNSTREAM PROPAGATION

No clean mainstem cascade today — this was direct/distributed forcing, like Event 11. Each gauge responded to its own-zone rain near-simultaneously (Pruitt to local Cove; Harriet to local Water/Tomahawk; Bear/Richland to own zones). Pruitt's 4150 cfs cannot be Ponca routing (Ponca only 431 cfs) — it is local Cove Cr. St. Joe→Harriet/St. Joe propagation of the Richland-Cave-Big flood pulse is still in transit at cutoff and will dominate the overnight hydrograph. I will compute mainstem propagation velocities tomorrow once St. Joe peaks.

5. MULTI-DAY EVENTS

This is the onset of Event 20, NOT a continuation — D-1 and D-2 were sub-threshold (0.099" and 0.000" basin-max). The Event-19 recession tail had drained to baseflow (St. Joe 706 cfs, Harriet 917 cfs at start of day). Event 20 lands fresh on that drained, moist-but-not-saturated baseflow. The event is incomplete in today's window: expect overnight St. Joe surge (possibly flood-scale given Richland 8.35 ft + Cave 3.41" + Big 3.36" incoming), a Harriet secondary peak from Bear Creek's 7580 cfs + upstream propagation, and a delayed Boxley pool-fill rise.

6. ANOMALIES OR SURPRISES

1. First mid/lower-basin-concentrated flood-scale event of the study — the spatial complement to Event 19's upper-only flood. Directly addresses Open Q4 (March-2024 Richland signature): a Richland-zone 3.79" event → 8.35 ft / Pruitt 4150 cfs. Still below the 2024 reference (4–8" → ~15 ft St. Joe, Richland 30→17,000 cfs), confirming the lower half of that scaling; a 5–8" Richland bullseye would be needed to reproduce 2024.
2. Bear Creek 2.07 ft/in at low stage CONFIRMS Event 16 (2.08) despite drier antecedent — strongest validation yet that Bear transfer is stage-dominated when forcing is extreme; even Event-11 dry damping is overrun by 3.77" on near-baseflow stage.
3. Three study-record peaks in one day — Pruitt 10.11 ft / 4150 cfs, Bear 8.72 ft / 7580 cfs. CFS values are high-confidence (active-weather field calibration regime).
4. St. Joe lag/decoupling: with tributary forcing concentrated below the gauge's own-zone response time, the trunk barely moved (+0.50 ft) while tributaries went to flood — a vivid demonstration that the mainstem integrates tributary pulses with substantial delay, and that QPE spatial pattern flags developing flood hours before the trunk gauge responds (Q4-tier objective realized).