Precip, and who is dry
GFS, ECMWF, ECMWF AIFS, GEM · Run 00Z 1 Oct · +42 → +66 h · Valid Sat 18Z 3 Oct
Number of models that predict at least 0.1 in of liquid precip over those 24 hours
Region Northern Plains
The readings under the map are for the whole map, not only the part shown.
GFS, ECMWF, ECMWF AIFS, GEM · Run 00Z 1 Oct · +42 → +66 h · Valid Sat 18Z 3 Oct
Number of models that predict at least 0.1 in of liquid precip over those 24 hours
Some model reaches that over 33% of this map · all four agree on 10% of it
Shows how many models put measurable precipitation on each point over the 24 hours ending 18Z 3 Oct — the day you choose.
Methodology
Total precipitation from GFS, ECMWF, ECMWF AIFS, GEM — four models and three centres, named because a roster is a fact about a chart: two of these are ECMWF's, and where those two agree they agree partly for family reasons. Each model's window is the difference between two of its own accumulations from the same run, so this is what fell inside those 24 hours rather than since the run began. Uncorrected model output, unlike the city forecasts elsewhere on this site.
Liquid-equivalent, which is what the models publish: frozen precipitation appears here as the water it would melt to, so a winter field is on this map without being named. A rain-versus-snow split is a later layer rather than a different number — this map's subject is whether anything falls, not what form it takes.
Unshaded ground is where all four keep it under 0.1 in. Most of what is coloured is an argument, which is the reason to draw it: the four models agree closely on how much falls over the map as a whole and disagree about where it lands, so counting who is wet shows a disagreement that mapping the amount would hide.
The threshold matters more than it looks. Against rain gauges these models produce measurable precipitation on 1.8× as many days as actually recorded any, falling to 0.6× at an inch — so a lower bar would fill the map in with the agreement least worth having, and a higher one empties it. At 0.1 in roughly a quarter to a half of the frame carries something, depending on the day.
Valid at 18Z, and the same hour every day so that successive maps compare. The bands are contoured between the counts rather than on them, and shaded ground is a forecast rather than a measurement — for who has actually been right about precipitation, the model leaderboards are the place.
This map is drawn from model output we store ourselves, not from anyone's picture of it, and is based on data and products of NOAA, the European Centre for Medium-Range Weather Forecasts (ECMWF) and Environment and Climate Change Canada. The per-city read of the same day — which cities the models are fighting about, and what the discussion makes of it — is on the national page.
Sources and licences
- NOAA: GFS, from NOAA's NOMADS server. US government data, not subject to copyright (NOAA/NWS terms of use).
- ECMWF: IFS and AIFS Single, from ECMWF's open data. This service is based on data and products of the European Centre for Medium-Range Weather Forecasts (ECMWF). Source: www.ecmwf.int. This ECMWF data is published under a Creative Commons Attribution 4.0 International (CC BY 4.0). ECMWF does not accept any liability whatsoever for any error or omission in the data, their availability, or for any loss or damage arising from their use.
- Environment and Climate Change Canada: GEM, from the MSC Datamart. Data Source: Environment and Climate Change Canada, under its Data Services End-use Licence.
What we change: each field is cropped to the frame these maps share when we download it, and each map then smooths, contours, differences or ranks those numbers as its Methodology says. These are our maps of the providers' numbers, not their products, and none of them has reviewed or endorsed this site.
Coastlines, borders, lakes and place names: Natural Earth, public domain.