Winter is expected to return this weekend with a storm system developing just to our southwest this morning. The weather forecast models have been teasing a significant snowfall for Iowa, but change their mind after sequential runs in time. The featured chart presents Global Forecast System (GFS) model forecasted precipitation for a grid point near Des Moines. The model is run every six hours producing a forecast out for the next two weeks or so. Model runs up until January 30th had this weekend being dry. Subsequent model runs then dumped heavy amounts of rain or snow or some mixture for Des Moines. Two model runs yesterday had Des Moines missing almost all precipitation. The most recent run (top row) now has rain today and snow on Saturday. Model inconsistencies like this make life fun and the folks that forecast the weather for a living lose hair or grey quickly.

Voting:
Good = 21
Bad = 4

Tags:   model  

The featured chart shows the time evolution of the GFS weather model forecast for precipitation for Burlington. The model runs made last week for today had no precipitation for Burlington, but the last three days worth of runs have advertised a significant snowfall event with totals over a foot expected. This is a part of one of the most hyped winter storms over the plains in recent memories. Blizzard warnings are posted for this afternoon as winds will be picking up and blowing whatever does fall around creating a huge mess. Iowa should miss out on the major ice accumulations expected to fall over Missouri and Illinois.

Voting:
Good = 44
Bad = 4

Tags:   model  

The GFS weather forecast model is run by the US government and produces forecasts from the current time out to about two weeks into the future. The model runs for the past week have been advertising a snow storm for today into Christmas Eve. This forecast has evolved over time though as is presented by the featured chart. Each row in the chart represents a successive forecast model run. The area in white is outside the time domain of the given model's run output data (8 days). Model runs made on the 19th dumped a fair amount of snow on Ames for today, but have since backed off on the amounts and delayed the onset by 12 or more hours. Making sense of this changing forecast is one of the reasons why we still have humans diligently creating forecasts each day.

Voting:
Good = 49
Bad = 12

Tags:   model  

The featured chart displays a forecast model's initial analysis along with the latest forecast of precipitable water approximately for Ames. This value can be considered the depth of water in the atmosphere if all of it was squeezed out. When values exceed two inches, slow moving thunderstorms are able to quickly dump lots of rain. The heaviest rains this morning are just north of Ames with a report of 5 inches already around Fort Dodge.

Voting:
Good = 28
Bad = 6

Tags:   model  

The featured map is forecasted precipitation from the NAM weather forecast model from a run yesterday afternoon showing Iowa getting a tremendous amount of rainfall through Thursday afternoon (over 10 inches is the highest amount). These forecast models are run multiple times per day and the latest runs have moved this precipitation bullseye around a lot. Regardless, extremely heavy rainfall is set to fall somewhere in the midwest.

Voting:
Good = 28
Bad = 5

Tags:   model  

The featured map displays the RUC computer weather model forecast of surface based CAPE for yesterday afternoon. CAPE is a measure of the vertical accelerations possible if air is forced upward initially. Typically, values of around 3,000 indicate severe storms are possible. Due to the extreme surface temperatures and dew points yesterday, values were over 10,000 J/Kg. Values this large are extremely rare.

Voting:
Good = 35
Bad = 10

Tags:   cape   model