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Project Updates: Probable Maximum Precipitation Estimation Modernization
October 2026 Project Update
From project lead Kelly Mahoney on behalf of the NOAA Modernizing PMP team:
Thank you for your continued interest as we work together to modernize Probable Maximum Precipitation (PMP) estimates for the nation. While it has been a while since our last project email update, it has been great engaging with many of you via recent workshops, conferences, briefings, and meetings. Following the NOAA-hosted August 2026 Virtual PMP Community Workshop ( View workshop slides [PDF, 10.2 MB]), we are pleased to share key project updates, highlight recent technical milestones, and address common questions regarding next steps.
Looking Back to Look Forward: The 1976 Big Thompson Canyon Flood StoryMap
As part of our commitment to blending lessons from past severe weather with current research, we recently released an interactive Big Thompson Canyon Flood StoryMap. Through this feature, you can learn about this devastating flood’s causes, immediate impacts, and importance to research. Re-examining historic extreme storms like this through state-of-the-art modeling reveals forgotten meteorological drivers and highlights the inadequacy of static, decades-old standards, and the need to transition toward modern, non-stationary PMP methodologies.
Expanded Historical Extreme Precipitation Events Database
To support near-term enhancements recommended in the National Academies (NASEM) study, we have expanded our Historical Extreme Precipitation Events Data Library that was launched earlier this year:
- Twenty (20) new storm cases have been digitized and added to the interactive web portal, bringing the catalog to 40 total extreme storm events spanning from 1996 to 2024.
- The database provides spatial grids, synoptic conditions, and recurrence intervals to give practitioners transparent access to the historical storm catalog driving PMP research.
Research Accomplishments and Technical Output
Our interdisciplinary NOAA Physical Sciences Laboratory, Global Systems Laboratory, and Cooperative Institute research teams continue to advance PMP science at a rapid pace. We encourage you to visit our PMP Project Accomplishments page, which has been updated with:
- Seven (7) peer-reviewed recent journal publications detailing advancements in kilometer-scale climate simulations, radar reanalysis, deep learning rainfall mapping, and high-resolution reforecasts
- Nine (9) new major conference presentations across AMS, AGU, and specialized hydrometeorological summits.
Frequently Asked Questions (Post-August 2026 Workshop)
The August 2026 workshop ( View workshop slides [PDF, 10.2 MB]) featured updates on the Model Evaluation Project (MEP), high-resolution dataset generation, as well as updates from our partners at the Association of State Dam Safety Officials and US Army Corps of Engineers. Here are responses to a few of the most frequently asked questions submitted during and after the workshop:
Q1: How will community input be incorporated through the new Scientific and Technical Working Group?
A: The Scientific and Technical Working Group (STWG) is structured around three dedicated subcommittees: Definition Development, Statistical Robustness, and Model Validation. Based on participant feedback from the webinar's interactive Mentimeter session, we are planning to expand “Definition Development” to also include more sub-topics related to community input, e.g., stakeholder engagement, service delivery, and codevelopment. In addition to the STWG, it is important to note that we also have a standalone Partnership and Engagement Strategy and plan, and the efforts planned in that realm will complement some of the more technical engagement within the STWG. We also heard the importance of clarifying how public-facing tools and service delivery will receive structured user review, and also that it would be helpful to establish clearer guidelines on time commitments for various engagement opportunities. When we are able to progress to the next, expanded version of the STWG draft, these changes will be incorporated.
Q2: How are NOAA, USACE, and partner agencies coordinating storm databases and modeling to avoid duplication?
A: NOAA and USACE work in close alignment. While USACE focuses on ingesting historical gridded storm data (~1,190 HMR and 555 gridded events) into the Extreme Storms Database for immediate risk-informed decision making needs, NOAA is leveraging baseline observational datasets within the Model Evaluation Project to validate high-resolution atmospheric model simulations (such as WRF and MPAS downscaling). While the workstreams have historically been separate, we are working on a concept that would (eventually) pull them together in a common framework so that the community can benefit from a vetted, shared collection of complementary, transparent, and built-on-shared ground-truth datasets.
Q3: When will modernized PMP datasets be available, and what is the plan for non-CONUS regions like Alaska?
A: Multi-decadal kilometer-scale simulations (e.g., CONUS-Futures, Nested Replay) and high-resolution reforecast datasets are actively running on cloud computing platforms and are projected to have their first member or generation complete production by early-mid 2027. Our plan is for all of these generated by NOAA to be publicly available and as user-friendly as possible. Regarding regions outside of CONUS, while initial model evaluation has focused on CONUS due to available dataset and observational density, research on applying convection-allowing model frameworks and high-resolution reforecasts in non-contiguous regions (including Alaska and Hawaii) is being planned in parallel.
Special thanks to the SCRPI Team
A heartfelt thank you to the BIL-supported SCRPI (Support for Climate Resilience Planning and Innovation) team whose time on the project ended with the 2026 fiscal year. NOAA’s extreme precipitation modernization effort has benefited tremendously from their energy, expertise, creativity, and dedication. Their contributions (e.g., the Big Thompson StoryMap, the Partnership Engagement Strategy, and the Scientific and Technical Working Group framework) will continue to drive our PMP modernization efforts forward and shape the future of extreme precipitation research.
Stay connected
- Feedback & inquiries: Have additional questions or suggestions for historical storm cases? Contact our team at psl.pmp@noaa.gov.
- Help spread the word about the PMP Estimation Modernization effort by sharing the new PMP information sheet, available as a print PDF (1.3 MB) and an interactive PDF (1.3 MB).
Thank you for your continued partnership as we build a scientifically robust, transparent, and usable PMP framework for the nation!
December 2025 Project Update
From project lead Kelly Mahoney:
As the end of 2025 approaches, we wanted to take an opportunity to thank each of you for your partnership and presence this year, reflect on the accomplishments of our team thus far, and look ahead at the plan for 2026.
Partnership Engagement Planning
Since June, our team has worked to prepare an initial draft of the Partnership Engagement Plan, which will allow us to continue brainstorming and collecting feedback on the best strategies for collaboration and engagement in the future. We have already received valuable feedback from the Association of State Dam Safety Officials (ASDSO) Extreme Precipitation Investigation Committee (EPIC) as well as some stakeholders within the nuclear community, which we have incorporated into this latest draft (PDF, 1.7 MB)
We also are planning for a (virtual) PMP Community-wide Update Meeting in February 2026; we will send out a save-the-date for this once we have it confirmed. One of the goals of this meeting will be to solicit and collect feedback on the draft of the Partnership Engagement Plan.
Accomplishments: June-December 2025
Here are select accomplishments since our last update, with more to be highlighted in the planned February Community Meeting.
- New Historical Storms webpage created: The first cases are now available on our new Historical Extreme Precipitation Events webpage. This resource hosts analyses of extreme precipitation events that currently determine PMP and may be of interest for updating future PMP. This also addresses several of the short-term recommendations from the National Academies' PMP Report. Additional cases will continue to be added, and recommendations from the community are welcome regarding additions or changes to the page.
- Virtual Workshop held: The NOAA Modernizing PMP project sponsored the National Academies of Science, Engineering, and Medicine’s "Extreme Rainfall in Mountainous Terrain: Modeling and observational challenges for warm-season precipitation” workshop held on November 4, 2025. This virtual workshop explored the scientific challenges and opportunities associated with observing, understanding, and modeling extreme warm-season rainfall in mountainous regions. Participants from across academia, government, and operational agencies provided incredibly valuable insights, and a recording of the workshop is available.
- Research progress: Our NOAA PMP team has been prolific in research progress this year; many of these accomplishments are evident in publications, presentations, and growing community connections. A snapshot of some of the exciting advancements can be found among a list of upcoming conference presentations.
Operational updates
We appreciate your ongoing support and patience as we navigate many changes across NOAA and our partner organizations who share our collective goal of modernizing PMP for the nation.
As a reminder, the modernization of PMP was codified in the Bipartisan Infrastructure Law / Infrastructure Investment and Jobs Act (BIL/IIJA) and the Providing Research and Estimates of Changes in Precipitation (PRECIP) Act. Funding was provided through the BIL/IIJA to begin the process of modernization; that funding was anticipated through September 2026; it remains unclear at this time what appropriations may be available to fill the gap when BIL/IIJA funding ends. See PMP Draft Timeline
Communication, Partnering, and Community
As before, we will continue to communicate through this email list and updates to the NOAA PMP project page, and we will send out a February Workshop Save-the-Date once we have it confirmed.
If you know of others that would like to sign up for updates from the NOAA PMP Team, the signup form at the bottom of the NOAA PMP project page. Any questions or feedback on the project can be emailed to psl.pmp@noaa.gov.
Thank you again for your partnership in creating a community dedicated to modernizing PMP!
June 2025 Project Update
From project lead Kelly Mahoney:
The NOAA PMP team has been working hard to bring the vision of a modernized PMP to reality, and we are incredibly grateful for your support and interest in this work. We’re excited to share some of our accomplishments since December 2024, along with a roadmap for the next 3-6 months.
Accomplishments: January-June 2025
- Extreme Precipitation Event Case Study webpages are being developed which will host analyses of many events that determine PMP currently and may be of interest for updating future PMP. These webpages address several of the short-term recommendations from the NASEM Report, and we expect these webpages to go live by September 2025.
- Several papers have been submitted, accepted, and published documenting the representation of extreme precipitation in key NOAA datasets (e.g., James et al. 2025).
- Development and evaluation work remains ongoing for new experimental high-resolution, rapidly updating NOAA models that will also be leveraged for producing extended reforecast datasets to serve both modernizing PMP and the broader extreme precipitation-interested community.
- NOAA approved the use of IIJA PMP funding to support a National Academies of Science, Engineering, and Medicine workshop on orographic extreme precipitation.
- Partnership with US Army Corps of Engineers (USACE) to inventory, preserve, and make accessible historical data, analyses, maps, and records of extreme storm rainfall events used to estimate PMP.
- Partnership with the National Centers of Environmental Information (NCEI) to support user engagement strategy and implementation through summer 2026.
Roadmap: July - December 2025
- Develop a partnership engagement strategy and identify opportunities for co-engagement with other extreme precipitation products (e.g., NOAA Atlas 15).
- Begin implementing partner engagement to inform the early stages of PMP definition and development.
- Begin developing an implementation plan that will guide NOAA’s approach to implementing the recommendations in the NASEM Report.
Operational updates
We appreciate your ongoing support and patience as we navigate many changes across NOAA and our partner organizations who share our collective goal of modernizing PMP for the nation.
As you may know, federal agencies are undergoing a comprehensive review of activities, projects, and personnel to ensure all initiatives align with the current administration’s priorities. This process has resulted in some unexpected changes to the NOAA PMP team to which we are adjusting.
In addition, the modernization of PMP was codified in the Bipartisan Infrastructure Law / Infrastructure Investment and Jobs Act (BIL/IIJA) and the Providing Research and Estimates of Changes in Precipitation (PRECIP) Act. Funding was provided through the BIL/IIJA to begin the process of modernization; that funding is anticipated through September 2026. However, the timeline for developing PMP lasts through 2030, and it is unclear at this time what appropriations may be available to fill the gap when BIL/IIJA funding ends.
Communication, Partnering, and Community
Despite the challenges, the NOAA PMP team remains dedicated to this important work, and will keep you updated with our progress.
- Communication will continue through this email list and updates to the NOAA PMP project page.
- You will hear from us again no later than December 2025 with another update.
- If you know of others that would like to sign up for updates from the NOAA PMP Team, please have them visit the signup form at the bottom of the NOAA PMP project page.
- For questions or feedback on the project, please do not hesitate to reach out via email to psl.pmp@noaa.gov.
Thank you again for your partnership in creating a community dedicated to modernizing PMP! Read the original email update