A substantial broad-area convective event swept the upper/central watershed, centered on the 15:00–18:00 CDT window (peak 1-hr times cluster around 15:02–16:02 UTC ≈ 10:02–11:02 CDT for the upper basin; but most HUC12 peak-1hr timestamps are 15:02–18:02 UTC = 10:02–13:02 CDT — wait, these are listed in UTC; converting: UTC 15:02 = 10:02 CDT, UTC 16:02 = 11:02 CDT, UTC 17:02 = 12:02 CDT, UTC 18:02 = 13:02 CDT). Looking at gauge timing the actual hydrologic response began mid-afternoon, so MRMS timestamps interpret as: peak forcing was 15:00–18:00 UTC = 10:00–13:00 CDT, with secondary cells building into evening (UTC 01:02 = 20:02 CDT shows on the ungauged southern HUC12s).
Zone-averaged 24-hr totals (upper basin emphasis): - Ponca zone 0.942" (peak 1-hr 0.259" Whiteley) — largest zone total. - Boxley zone 0.961" (peak 1-hr 0.185" @ 11:02 CDT; max 6-hr 0.743"). - Pruitt zone 0.812" (peak 1-hr 0.249" Hoskin Cr @ 11:02 CDT). - St. Joe zone 0.678" zone-avg, with Little Buffalo sub-group bullseye (Shop 0.856, Headwaters LB 0.855, Henson 0.848, Outlet LB 0.840) and Big Cr complex strong (Left Fork 0.813, Headwaters Big 0.708, Big Cr-Buffalo 0.774). Cave Cr 0.584; Outlet Richland 0.464. - Richland zone 0.548" (Headwaters 0.585, Falling Water 0.511) — moderate but secondary. - Bear Cr zone 0.331", Harriet zone 0.311", Ungauged 0.278" (with late-cycle Hickory Cr 0.504" peaking @ 20:02 CDT — second pulse).
Antecedent conditions: Moderately dry by the prior-week recovery standard. Boxley zone 7-day 0.45", Pruitt 1.30", St. Joe little-buffalo subgroup 0.5–1.7", Richland 0.41–1.01", Bear Cr 0.82–1.15", Harriet 0.57–1.38". This is the driest antecedent state since early May given Days 95–97 baseline reset.
Spatial pattern: upper-basin-bullseye event, almost mirror-opposite to Event 16's lower-basin/Bear Cr cell. Boxley/Ponca/Pruitt/Little Buffalo/Big Creek complex are the source zones; Bear Cr and Harriet zones largely missed.
Boxley (huge response — first significant Boxley signal of study): 1.92 → 2.52 ft, +0.60 ft in ~16 hr, with the steepest rise after 20:00 CDT (+0.18 ft/hr peak in the 22:30–23:30 window). Still rising at end of day — peak not yet observed. This event onset roughly tracks 4-hr behind peak forcing (peak QPE ~11:00 CDT, response onset visible at gauge ~15:00 CDT, acceleration after 20:00). This is the first time during the study Boxley has produced a recreationally meaningful rise.
Ponca: 91 → 159 cfs (+69.7 cfs, +77%), with surge concentrated 20:30–23:00 CDT. Still rising at EOD. Onset visible mid-afternoon (~10:15 = 91 cfs → 11:30 = 94.3); inflection at 20:30 (101 → 103 → 105 → 111 → 120 → 133 → 143 → 148 → 151 → 156 → 159). Response is in the same time window as Boxley acceleration, consistent with co-routing from Ponca zone (0.942" — the highest zone) plus arriving Boxley headwater pulse.
Pruitt: Only +0.04 ft / +5–9 cfs response despite 0.812" zone QPE. Gauge height oscillates 3.79–3.83 (essentially noise). This is anomalously small — see Anomalies.
St. Joe: No response yet. Continued recession from start-of-day 4.63/632 down to 4.48/561 by 22:15 (intraday low). Daily fall –0.14 ft / –66 cfs.
Harriet: No response yet. Pure recession 4.72 → 4.56 ft / 893 → 771 cfs. Daily fall –0.16 ft / –122 cfs.
Richland Creek: +0.13 ft response (1.43 @ 08:15 → 1.56 @ 19:45), then minor recession to 1.54. First Richland response visible since Event 17. Peaked ~19:45 CDT.
Bear Creek: No meaningful response — recession continues 2.50 → 2.44 ft / 52.2 → 45.3 cfs. Daily fall –0.06 ft / –6.9 cfs. Consistent with only 0.331" zone QPE on moderately-dry channel.
Richland Creek (the only complete-enough pair so far): - Zone QPE: 0.548" averaged, peak 1-hr 0.149" Headwaters Richland @ ~10:02 CDT (UTC 15:02). - Response: 1.43 → 1.56 ft = +0.13 ft peak @ 19:45 CDT. - Lag (peak QPE → peak gauge): ~9.75 hr. - Transfer ratio: 0.13 ft / 0.548" = 0.24 ft/in. - Antecedent: 7-day Richland zone (0.413" + 1.013")/2 ≈ 0.71" — moderately dry.
Comparison with prior Richland data: - Event 13 (Day 87, Richland-bullseye, 0.819" zone, dry-to-moist antecedent): transfer 0.90 ft/in in-channel. - Event 15 (Day 89, watershed-wide major, moist-to-wet): peak 8.89 ft from 5.4" zone QPE ≈ ~1.0+ ft/in. - Today's 0.24 ft/in is ~3.7× lower than Event 13's in-channel ratio.
Hypothesis: Richland transfer ratio collapses sharply when antecedent < ~1" zone-average AND total event QPE < ~0.6". This matches "first rain of a dry-down" behavior — channel is below baseflow, sub-basin storage/initial abstraction absorbs disproportionate fraction. Confidence: medium (n=1 dry-antecedent Richland event; need more low-QPE/dry pairs). Flag this as a deviation >30% from prior — refined estimate for dry-antecedent moderate forcing: 0.20–0.30 ft/in.
Boxley (in progress — peak not reached): - Zone QPE: 0.961" Terrapin Branch-Buffalo, peak 1-hr 0.246" @ ~11:02 CDT. - Response so far: +0.60 ft (1.92 → 2.52) — transfer-so-far 0.62 ft/in, still rising. - Apparent lag-to-acceleration: ~9 hr from peak QPE (11:02 → 20:00 inflection). - Antecedent: 0.45" 7-day — driest Boxley antecedent for any rain event observed in the study.
This is the first Boxley response of meaningful magnitude. Local knowledge: "the first major rain after a prolonged dry spell has to fill the pools." This appears to be exactly that signature — 9-hr lag suggesting pool-fill is happening, with a delayed accelerating rise as channel connectivity is established. Comparison: Event 11 (D80–82, dry-antecedent major event) showed Boxley pool-and-drop minimal response. Today's 0.45" antecedent is comparable. The fact that we're now seeing 0.60+ ft suggests either (a) 0.961" exceeds the pool-fill threshold that prior events did not, or (b) the rate of the rise after 20:00 reflects pool-connectivity completing. Will resolve tomorrow when peak is reached. Flag for Hailstone recreational threshold: 3.7 ft needed; currently 2.52 ft and rising — possible reach if rise continues at 0.18 ft/hr for 7 more hours, but unlikely given pool-and-drop hydrograph behavior.
Ponca (in progress — peak not reached): - Zone QPE: 0.942"; peak 1-hr 0.259" Whiteley @ ~11:02 CDT. - Response: 89.3 → 159 cfs = +70 cfs so far; transfer-so-far ~74 cfs/in. - Lag-to-acceleration: ~9 hr; sharp surge began 20:30, lagging Boxley by minutes (suggesting co-routing not sequential routing in this dry-channel onset). - Still rising. Likely to reach low-floatable threshold (200 cfs) tomorrow.
Pruitt (anomalously suppressed): - Zone QPE: 0.812", peak 1-hr 0.249" Hoskin @ ~11:02 CDT. - Response: +0.04 ft / +5 cfs at most. Transfer ~0.05 ft/in — 30–60× lower than typical wet-antecedent Pruitt ratio of 1.4–1.7 ft/in (Events 8, 10). - Antecedent: Cove 1.41", Hoskin 1.19" — moderately dry but not extreme. - Hypothesis: see Anomalies — Pruitt's upstream contributing area (Boxley + Ponca) is still in pool-fill mode and has not delivered routed water yet. The 0.812" Pruitt-zone QPE on its own contributing 123 km² produced almost no signal. This is strong evidence that Pruitt's response is dominated by upstream-routed flow, not local zone QPE, especially under dry-antecedent conditions. Expect Pruitt to rise sharply tomorrow as Boxley/Ponca pulse arrives.
Mainstem propagation is just beginning at end-of-day with the Boxley→Ponca leading edge. Both gauges show steepening rises in the same window (20:30–23:30 CDT), suggesting co-onset of local Ponca-zone runoff and arriving Boxley contribution. Pruitt has not yet shown the bulge. St. Joe and Harriet are still in pure recession.
I cannot yet compute mainstem propagation velocity because Boxley peak hasn't occurred and Pruitt has barely moved. Tomorrow's data will be critical to determine Boxley→Ponca→Pruitt routing under dry-antecedent first-flush conditions. Hypothesis: routing will be slower than the wet-antecedent baseline (Event 8 Pruitt→St. Joe 5–7 hr) due to channel storage absorption — expect 6–10 hr Boxley→Pruitt under dry conditions.
This is Event 19 (renumbering: Event 18 was the Day 96 sub-threshold pulse that produced no response; today is a new significant event). Onset Day 98 (Jun 6). Forcing dropped on the basin in a single 6–10 hr window 10:00–18:00 CDT. Tomorrow's analysis will capture the full hydrograph for upper-basin gauges.
The event lands on the driest antecedent state observed since early May (post-Day 95/97 dry-down). This makes it a high-value dry-antecedent calibration event for the upper basin gauges (Boxley, Ponca, Pruitt) and a complement to the wet-antecedent Events 8/10/15.
1. Boxley actually responded. Throughout the study Boxley has been the least responsive gauge — Event 11 produced only minimal response under similar dry antecedent. Today, 0.961" zone QPE has produced a clear +0.60 ft rise with acceleration in the final 3 hr. This contradicts the prior hypothesis that "Boxley pool-and-drop minimal response under dry conditions" generalizes for all dry events. Refined hypothesis: 0.961" appears to exceed the pool-fill threshold; ~1" of upper-basin rain on dry antecedent is enough to trigger Boxley response, though with a long (~9-hr) accelerating lag.
2. Pruitt's near-complete non-response (+0.04 ft on 0.812" zone QPE) on dry antecedent. This is the most striking finding of the day. It strongly supports the hypothesis that Pruitt's transfer ratio is dominated by upstream routing under all conditions, and Pruitt's own 123 km² zone QPE contributes little independent rise. The +0.04 ft transfer of 0.05 ft/in is so far below the wet-antecedent 1.4–1.7 ft/in that the difference cannot be explained by antecedent alone — it must reflect missing upstream contribution. This will be confirmed if Pruitt jumps sharply tomorrow as Boxley/Ponca peak.
3. Richland response: surprisingly small but timely. +0.13 ft from 0.548" zone QPE on 0.71" antecedent. Transfer 0.24 ft/in vs Event 13's 0.90 ft/in. Three possible explanations: (a) dry antecedent absorbs initial abstraction, (b) Headwaters Richland (0.585") got most rain while Falling Water (0.511") got less — spatial mismatch with channel position, or (c) sub-1" events on moderately-dry channels are simply in a low-efficiency regime. Likely a combination of (a) and (c).
4. St. Joe/Harriet pure recession into very low flows. St. Joe ended at 561 cfs (down from 632), Harriet at 771 (down from 893). These are now well below the wet-antecedent baseline (Day 92 was 2780/3700). Importantly, both will see arriving pulses tomorrow that — given low base — could produce substantial relative rises even if absolute peaks remain modest.