IEM :: Download SPC Convective/Fire Weather WPC Excessive Rainfall Outlooks Shapefile

The IEM attempts to process and archive the convective and fire weather outlooks issued by the Storm Prediction Center and the excessive rainfall outlooks issued by the Weather Prediction Center. This processing is done by parsing the PTS product via pyIEM decoder.

Recently, the SPC website has added direct single outlook downloads in various GIS formats. Your best data quality will come from scraping their website, but maybe that approach is not for all users of this data! So here it is, a means to bulk download the IEM's SPC/WPC Outlook database.

Backend Documentation

Processing Limit: Due to processing constraints, requests are limited to 10 single outlook type-years at a time.

Related Services

NWS Misc Polygons NWS VTEC Watch Warning Advisory SPC Convective Discussions SPC Watch Polygons WPC Precip Discussions

Time Interval for Outlook Issuance (UTC)

	Year	Month	Day	Hour	Minute	Outlook Type	Outlook Day
Start:						Convective (1987+) Excessive Rainfall (November 2015+) Fire Weather (2006+)	1 2 3 4 5 6 7 8
End:							1 2 3 4 5 6 7 8

Geometry Options

Geometries as 'Cake Layers'

Includes all overlapping risk levels for each location

Geometries as 'Cookie Cutters'

Shows only the highest risk level for each location

Shapefile DBF Schema

Field	Type	Title	Description
0	String	`ISSUE`	Outlook Beginning Valid Time UTC
1	String	`EXPIRE`	Outlook Ending Valid Time UTC
2	String	`PRODISS`	Timestamp of Product Issuance UTC
3	String	`TYPE`	Either C=Convective, E=Excessive Rainfall, F=Fire Weather
4	Double	`DAY`	Day 1 through 8 for the outlook
5	String	`THRESHOLD`	Threshold Label
6	String	`CATEGORY`	Category of Threshold Label, HAIL, CATEGORICAL, etc...
7	Double	`CYCLE`	The generalized forecast issuance hour

Archive / Usage Notes

8 Aug 2025: A date problem was identified with some SPC D3+ convective outlooks that crossed a month boundary prior to April 2019. This issue caused the date to be stored for the previous month. The database was corrected. We apologize for this error.

11 Jul 2023: The archive was reprocessed to allow for specification of returned geometries in either "cake layer" or "cookie cutter" form. This gets complex to explain, but hopefully as a simple example: If you are under a "Moderate Risk", the cake layer form would include polygons with thresholds of general thunderstorm, marginal, slight, and enhanced for your location: the cookie cutter form would just have a moderate polygon covering your location.

1 Apr 2021: An assessment was made of the archive completeness and found 99.9% coverage. Some of the holes are due to lost PTS text products yet to be found and others are due to errors within the PTS product causing it to be generally unusable.

Cycle Handling: A complication with using this dataset is that all outlooks are returned, the CYCLE attribute attempts to define a canonical outlook for a given issuance cycle. For example, the Day 1 20Z convective outlook may get issued three times for various reasons. The download contains all three, but two of them will have a cycle of -1 and the other will have a 20.

Geography Filter: Presently, the service only returns outlooks that had actual geographies associated with the outlook. For example, if there was no Day 5 area in the outlook, no entries are included in the download result.