On what date will the EIA first report U.S. propane and propylene ending stocks at or above 101.0 million barrels?

• My median prediction for the first EIA report of U.S. propane and propylene ending stocks at or above 101.0 million barrels is 4th September 2026.
• As of 26th June 2026, inventory levels stood at 91.3 million barrels, which is seasonally high and roughly 12% above the same period in 2025.
• Recent data shows a steady weekly build of approximately 2.0 million barrels, suggesting the 101.0 million barrel threshold is likely to be reached during the August to September window.
• Record NGL production and increased fractionation capacity at major hubs like Mont Belvieu support continued stock builds through the third quarter.
• Strong export demand remains the primary factor that could delay reaching the threshold, though current inventory momentum makes a 2026 crossing highly probable.
• Historical data shows this threshold is typically crossed in late September, but the elevated 2026 starting point pulls the expected date earlier.

Key figures

Historical context

U.S. propane and propylene ending stocks (EIA series WPRSTUS1) follow a distinct seasonal pattern, building during the warmer months (April to September) and drawing down during the winter heating season (October to March). Historically, the 101.0 million barrel threshold is considered a very high inventory level, achieved only during years of exceptional production. In the last five years, when the threshold was reached, the first crossing date occurred in a tight window: 26th September 2025 (103.4M), 11th October 2024 (103.1M), 22nd September 2023 (101.4M), 25th September 2020 (102.0M), and 30th September 2016 (101.3M). Notably, 2026 is starting from a much higher baseline; as of late March 2026, stocks were 77 million barrels, which was 47% higher than the five-year average for that month. By late June 2026, stocks had already reached 91.3 million barrels, a level usually not attained until mid-August in previous cycles.

Tailwinds

• Sustained record-high U.S. NGL production driven by growth in the Permian Basin and strong associated gas flows.
• Significant recent expansions in fractionation capacity (e.g., EPD Frac 14, Targa Train 11) increase the supply of purity propane for storage.
• A narrowing of the U.S.-to-Asia price arbitrage in June 2026 may reduce the incentive for spot exports, leaving more product in domestic caverns.
• High starting inventory levels (91.3M in late June) provide a much shorter path to the 101M threshold than in typical years.

Headwinds

• Record U.S. LPG export capacity, including the Neches River Terminal expansion, allows surplus inventory to be exported rather than stored.
• High international demand for U.S. NGL feedstocks, particularly from Asian petrochemical plants seeking alternatives to Middle Eastern supply.
• Potential production shut-ins or maintenance at major fractionation hubs like Mont Belvieu that could temporarily slow the rate of inventory accumulation.
• Narrowing price spreads between domestic (Mont Belvieu) and international markets might incentivize domestic use or spot exports over storage.

Detailed reasoning

My analysis suggests that the 101.0 million barrel threshold will be crossed significantly earlier in 2026 than the historical norm of late September or October. As of 26th June 2026, U.S. ending stocks (series WPRSTUS1) stood at 91,306 thousand barrels. This starting position is approximately 10-12% higher than levels observed during the same calendar week in high-inventory years like 2024 and 2025. To reach the 101.0 million barrel target, the market requires an additional build of approximately 9.7 million barrels.

In the four weeks leading up to 26th June, the average weekly build was approximately 2.0 million barrels. If this rate persists, the threshold would be reached in roughly five weeks, pointing toward the report for the week ending 31st July or 7th August. However, several moderating factors must be considered. First, seasonality typically dictates that while builds continue through September, the rate often fluctuates as export demand and petrochemical feedstock requirements shift.

On the supply side, the fundamental environment is extremely robust. U.S. natural gas liquid (NGL) production is at record highs, and new fractionation capacity—such as Enterprise Products Partners’ Frac 14 and Targa’s Train 11—has increased the volume of purity propane available for storage. Earnings calls from major midstream players confirm that these facilities are operating at high utilization.

The primary “brake” on inventory accumulation is the record-level export activity. U.S. LPG exports reached 2.9 million barrels per day (mbd) in May 2026. Although June saw a slight decline to 2.7 mbd following the reopening of the Strait of Hormuz and a narrowing of the price arbitrage to Asia, export capacity remains at an all-time high. The second phase of the Enterprise Neches River Terminal, which added 360,000 barrels per day of propane loading capacity in early 2026, ensures that any surplus production can be quickly diverted to international markets.

My forecast weights the current elevated stock levels (the “inside view”) more heavily than the historical “base rate” of late September. While history suggests a crossing in late September, the 2026 data shows inventories are already at levels typically not seen until mid-August. I have centered the median prediction on 4th September 2026 to account for a potential slight slowing of the build rate in late summer as exports remain competitive, while still acknowledging that the 101.0 million barrel milestone is nearly certain to be reached during this build cycle. I have assigned a high cumulative probability (over 90%) that the event occurs before the end of 2026.

Key uncertainties

• Unplanned outages at major storage or fractionation facilities in Mont Belvieu or Conway could abruptly halt inventory builds.
• Sudden shifts in global energy markets or geopolitical tensions in the Middle East that could reopen the Strait of Hormuz volatility and surge export demand.
• Potential hurricanes or severe weather in the U.S. Gulf Coast that could disrupt both production and export loading operations.
• Significant changes in domestic petrochemical demand (e.g., cracker outages) that could leave more or less propane in storage.

Conclusion

• My median prediction for the first EIA report of U.S. propane and propylene ending stocks at or above 101.0 million barrels is 4th September 2026.
• Strategic focus should remain on the balance between high domestic fractionation capacity and record-level export demand, as these two forces will dictate the exact timing of the inventory peak.
• Decision-makers should monitor the Wednesday EIA releases starting in mid-August, as current above-average inventory levels make an earlier-than-historical crossing highly probable.

Question: will the EIA weekly propane stocks (WPRSTUS1) first-report at or above 101.0 million barrels on a week-ending date on/after 2026-07-03 (eligible weeks through 2026-08-07)? Latest EIA level is 91.306 million bbl (week ending 2026-06-26), leaving a 9.694 million bbl gap; that implies implausibly large builds for Jul 3/Jul 10 and still very large ~3.2 million bbl/week for Jul 17, while July 24–Aug 7 require ~2.4–1.6 million bbl/week. Forecasters agree the recent four-week build pace (~2.0 million bbl/week) makes late‑July/early‑August the most realistic window, and a baseline Monte Carlo produced most first-crossing mass on Jul 31 (~37%) and Aug 7 (~22%) with ~22% no-cross by Aug 7. Countervailing evidence: historical analogues show 101 million is normally a late‑season level (first crossings historically in September–October), and strong, lumpy exports or high product supplied could materially delay the crossing. Practical trigger points for updates are each WPSR release, recalculating the remaining gap, required weekly builds, one-/four‑week builds, and a rough flow balance (production + imports − exports − product supplied). Net: expect most probability concentrated on late July/early August crossings, but retain a substantial upper‑tail probability that exports or demand keep inventories below 101.0 through Aug 7.

Forecast and Reasoning

Forecast: Probability distribution:

• 10.00% chance of value below 2026-07-24 11:17:38 UTC
• 20.00% chance of value below 2026-07-24 13:21:01 UTC
• 40.00% chance of value below 2026-07-31 13:25:33 UTC
• 60.00% chance of value below 2026-08-07 13:20:49 UTC
• 80.00% chance of value below 2026-08-08 07:00:00 UTC
• 90.00% chance of value below 2026-08-08 07:00:00 UTC

Forecast Reasoning

Key facts from the analysts’ research agree on the current baseline: the latest EIA WPRSTUS1 data point available as of 2026-07-02 is for week-ending 2026-06-26 at about 91.306 million barrels. The threshold is 101.0, so the remaining gap is ~9.7 million barrels.

The most decision-relevant variable is the weekly build rate from late June through early August. Using the cited recent momentum (roughly +8.0 MMbbl over the four weeks ending 2026-06-26, i.e. ~2.0 MMbbl/week), a naive extrapolation hits 101 in about 4.5–5.5 weeks, which lines up best with the week-ending 2026-07-31 (about 5 weeks after 6/26) as the modal/median outcome.

I discount the more aggressive “median 7/24” path as requiring a sustained ~2.4 MMbbl/week build from 6/26 to 7/24—plausible but not the central case. Conversely, I discount the very heavy open-after tail (i.e., not reaching by 8/7) because missing by 8/7 would require builds averaging <~1.6 MMbbl/week for six weeks, which is possible but not the base case given current elevated inventories and recent build pace.

So I center the distribution on 2026-07-31, with meaningful mass on 2026-07-24 and 2026-08-07, and a moderate (~20%) open-after tail (>2026-08-08) capturing scenarios where builds slow materially (exports/production/weather/storage dynamics) such that the threshold is not reached by the last in-window week-ending date (2026-08-07). Open-before (<2026-07-11) is kept very small because reaching 101 by week-ending 7/10 would require implausibly large two-week builds from the 6/26 baseline.

An amateur forecast might (a) anchor on historical seasonality (“usually crosses 101 in Sep/Oct”) and put almost all mass in the open-after tail, or (b) extrapolate the most recent strong builds and conclude an overly-early July crossing with too much confidence. This synthesis explicitly uses the reported current level (~91.3 MMbbl), translates the remaining gap into required weekly builds for each eligible week-ending Friday, and keeps a non-trivial but not dominant open-after tail to stay calibrated to build-rate volatility and structural uncertainties.

Forecast rationale (numeric):

— Iteration 1 — Across the forecasts, the reasoning is highly consistent:

• Seasonality is the dominant driver. U.S. propane and propylene stocks typically build from spring through early fall and draw down in winter, so the first chance to reach 101.0 million barrels is during the 2026 build season, not in the near term.
• Starting inventories are not unusually high. The models all rely on the idea that spring 2026 stocks were near the 5-year average, which makes an early crossing unlikely unless the summer build is unusually strong.
• 101.0 million barrels is treated as a high threshold. Because the level is elevated, a crossing requires a meaningful accumulation over the summer; this pushes the expected timing into late summer or fall 2026 rather than July or early August.
• Historical context matters. The fact that the threshold was last reached in autumn 2025 supports the idea that a similar or slightly later crossing is plausible in 2026, with the center of mass around late September to early October 2026.
• Weekly EIA cadence shapes the dates. Probability tends to cluster on Friday report dates, since the EIA publishes weekly ending-stocks data on Fridays.

Consensus view

Most of the probability is concentrated on a late September to October 2026 first crossing, with very little chance before late August.

Main uncertainty

The main disagreement is not about the seasonal logic, but about how strong the 2026 build season will be. If it comes in weaker than expected, the first qualifying report could slip into the next build season in 2027 or later.

— Iteration 2 — The forecasts are broadly aligned around a few core ideas:

• Seasonality is the main driver. U.S. propane and propylene stocks typically build from spring into late summer, so a 101.0 million barrel threshold would most likely be reached near the seasonal peak rather than in early August.
• The threshold is unusually high. All of the rationales treat 101 million barrels as a level that is only reached near the upper end of the normal inventory range, making a late-summer crossing more plausible than an early one.
• Recent supply conditions support a build, but not necessarily a fast one. Strong 2026 production and inventories near or above the five-year average push toward a crossing, but the expected weekly build pace is still viewed as too slow to make early August likely.
• Timing is concentrated in late August to September. The most common expectation is that the first EIA report at or above 101.0 million barrels will come on a Friday report date in late August or September 2026, with medians ranging from late August to mid-September.
• There is meaningful tail risk. One line of reasoning assigns a nontrivial chance that inventories do not reach 101 million barrels this season at all, especially if exports rise or production weakens, pushing the first crossing into a later build season.

Overall, the shared view is that the stock threshold is likely to be reached only after several more weeks of seasonal accumulation, with early August considered unlikely and late August/September the central forecast window.

— Iteration 3 — Across the forecasts, the main drivers are:

• Strong seasonal pattern in propane stocks: Inventories typically build from spring through early fall, with peaks in late summer to October/November. This makes a first cross above 101.0 million barrels more likely in the August–October 2026 window than earlier in the year.
• Reference to recent history: The 2025 stock path is used as a benchmark, with inventories reaching very high levels in late September/October 2025. That precedent supports the idea that a 101 million barrel crossing is plausible again in the fall.
• Production outlook vs. uncertainty: One view assumes higher 2026 production could pull the crossing forward into mid-August. Others are more cautious, arguing that typical early-August stocks remain well below fall peaks, making September or October more likely.
• Weekly reporting cadence: All forecasts align candidate dates to EIA week-ending Fridays, since the series is reported weekly.
• Tail risk of no crossing in 2026: There is some probability that stocks never reach 101 million barrels in 2026 if exports stay strong or production/distribution dynamics are weaker than expected, which would delay the first crossing until 2027 or later.

Overall consensus

The forecasts broadly agree that the first report at or above 101.0 million barrels is most likely to occur on a Friday between mid-August and October 2026, with mid-August viewed as possible but more aggressive, and late September to mid-October seen as the more typical outcome.

Summary of Forecasting Rationales

To reach the EIA’s threshold of 101.0 million barrels, U.S. propane and propylene stocks must accumulate roughly 9.7 million barrels from late June 2026 levels. Forecasters agree that the exact timing of this milestone depends on a structural tug-of-war between record domestic production and aggressive export capacity.

Factors Accelerating Inventory Builds Forecasters highlight that domestic associated gas production—particularly from the Permian Basin—remains at historic highs. This massive supply is met with a seasonal summer trough in domestic demand, which has been further suppressed by scheduled and unscheduled outages at major petrochemical plants. Additionally, forecasters note severe logistical bottlenecks acting to trap propane domestically. Factors such as Panama Canal draft restrictions, elevated ocean freight rates, and terminal force majeures have led to canceled cargoes, forcing artificially accelerated weekly injections into domestic storage.

Factors Throttling Inventory Builds The primary headwind to a rapid build is the U.S.’s record-high export capacity, which acts as a market relief valve. Newly commissioned export infrastructure expansions (such as Enterprise Products’ Neches River Phase 2) are highly incentivized to pull domestic propane into the global market to meet strong Asian petrochemical demand and replace disrupted Middle Eastern supplies. If these terminals operate efficiently, the average weekly domestic build rate will slow considerably. Furthermore, as Gulf Coast salt caverns approach their working capacity limits, physical and geomechanical constraints could force operators to throttle injection rates.

Expected Trajectory If the recent strong summer injection rates hold, forecasters anticipate the threshold will be crossed in late July. However, if new export infrastructure operates at peak capacity or if physical storage limits begin to cap injection speeds, the accumulation pace will slow, delaying the threshold breach into August or later.

Frontier Forecast — Post 582

Modal: Aug 01, 2026 to Aug 08, 2026 (30.0%) • frontier aggregate • 7m44s

Interpret Summary

• Reading: strict
• Type: strict
• Window: EIA Weekly Petroleum Status Reports with week-ending dates on or after 2026-07-03, released on or before 2026-08-12

Resolution sources/checks:

• https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=WPRSTUS1&f=W: https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=WPRSTUS1&f=W - Resolver URL extracted mechanically from resolution criteria

Edge cases:

• The threshold is 101,000 thousand barrels (= 101.0 million barrels); borderline values exactly at 101,000 qualify (‘at or above’).
• Only the first-reported value counts; EIA revisions to historical data are explicitly excluded from changing the outcome.
• Week-ending dates of July 3 or July 10 (both before the 2026-07-11 window start) would resolve as the ‘<’ bin, not annul.

Temporal Support

• Policy

  • explicit_publication_dates / first_passage_scheduled

• Source cadence

  • explicit_release_calendar

• Candidate dates

  • 2026-07-03, 2026-07-08, 2026-07-10, 2026-07-15, 2026-07-17, 2026-07-22, +6 more; residual/no-hit: ?

• Status

  • candidate

• Warnings

  • Derived 12 candidate date(s) from structured source-calendar cadence.; Temporal support is diagnostic only. Verify explicit_release_calendar before concentrating mass on candidate dates.

Frontier Views (5/5)

• frontier_1 - Modal: Aug 01, 2026 to Aug 08, 2026 (46.0%)

  • As of the latest EIA Weekly Petroleum Status Report (week ended 2026-06-26), propane/propylene stocks are about 91.3 million bbl, implying roughly +9.7 million bbl needed to reach 101.0. Recent weekly builds in June ranged around ~1.3–2.6 million bbl, consistent with seasonal summer builds.

• frontier_2 - Modal: Aug 08, 2026 to Sep 07, 2026 (40.0%)

  • The resolving series (WPRSTUS1, propane/propylene excl. terminal) stood at ~91.3 mb as of the week ending 2026-06-26 (verified EIA figures: 06-05=84.46, 06-12=87.43, 06-19=90.05, plus RBN-reported +1.3 build for 06-26).

• frontier_3 - Modal: Jul 18, 2026 to Jul 25, 2026 (28.0%)

  • As of the EIA report for the week ending June 19, 2026, U.S. Propane and Propylene ending stocks (WPRSTUS1) stood at 90.047 million barrels. To reach the threshold of 101.0 million barrels, an additional 10.95 million barrels must be built.

• frontier_4 (revised) - Modal: Aug 01, 2026 to Aug 08, 2026 (35.0%)

  • Revised after adjudication: Adjudicator correctly identified mechanical error: original forecast used wrong series (including-terminal totals) instead of required EIA WPRSTUS1 first-reported values,… The resolving series is strictly WPRSTUS1 (excluding propylene at terminals). Latest first-reported value is 91.3 MBbl (week ending 2026-06-26).

• frontier_5 - Modal: Aug 01, 2026 to Aug 08, 2026 (35.0%)

  • Forecast based on the latest EIA WPRSTUS1 series data (Propane/Propylene Excluding Propylene at Terminal). As of week ending 6/26/2026, stocks stand at ~91.3M barrels.

Adjudication

• Material notes

  • frontier_3: flag_only/warning - Did not clearly use the first-reported WPRSTUS1 value for week ending 2026-06-26; must verify inclusion of that EIA data point (it materially affects the starting gap).
  • frontier_4: discount/material - Agent treated an including-terminal/aggregate series (or ambiguous third-party summaries) as resolving evidence rather than the EIA WPRSTUS1 first-reported series required by the question. That produces a materially incorrect early concentration.

• Guidance

  • frontier_4 materially relied on an incorrect/including-terminal series and/or third-party totals rather than the required EIA WPRSTUS1 first-reported values (producing an implausible early mass).

• Revision

  • Attempted revision for frontier_4; changed frontier_4.

Final Distribution (date ranges)

Sources Checked

• Resolver: Resolver URL extracted mechanically from resolution criteria - https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=WPRSTUS1&f=W
• frontier_1: https://www.eia.gov/petroleum/supply/weekly/pdf/wpsrall.pdf
• frontier_2: EIA LeafHandler WPRSTUS1 / serper snippets
• frontier_2: RBN Energy analyst insight
• frontier_2: EIA historical WPRSTUS1
• frontier_2: level_forecast tool

wooley_rhino • run 48fcf234 • $3.08 • 7m44s

Seasonal storage limits and mid-summer demand patterns constrain rapid inventory swings.

Stocks sit roughly 9.7 million barrels below the 101.0 million-barrel threshold and must be closed by successive weekly builds.

Recent multi-week builds are near historical summer rates, supplying upward momentum that makes an early-August crossing plausible.

Export flows, petrochemical feedstock draws, fractionation output, and logistics operations exert continuous, often lumpy downward pressure.

A crossing by July 17 would require an exceptional two-week build approaching three-plus million barrels per week; July 31 needs about two million per week; August 7 needs about 1.6 million per week.

Timing therefore pivots on whether the current build pace persists for four to six successive reports or whether one or two weak weeks interrupt it.

Key unresolved sensitivities are sudden export surges, weather-driven demand spikes, and terminal-scale operational disruptions that can flip one-week balances.

Weekly reporting noise and first-print revisions affect the observed first passage and widen the upper-tail timing uncertainty.

Forecast: 2026-08-27 (first week-ending report with propane/propylene ending stocks ≥ 101.0 million barrels is most likely in late August; no single median provided.)

• Current inventories are below the threshold (91.306 million vs. 101.0 million), so the timing depends on how fast stocks build week by week.
• The latest trend shows weekly builds slowing (the build size dropped noticeably over the last few weeks), which pushes the crossing later.
• If builds revert back toward a typical July pace, the threshold is likely reached around late July to early August.
• If the slower pace continues, the threshold is more likely to be crossed mid-to-late August, with additional delay possible into September.
• The forecast’s spread reflects uncertainty about whether the recent deceleration is temporary or persistent—this is the key swing factor.