The following are general statements we can make about the weather for the inauguration as of this date:
* The unseasonably warm conditions we’ve experienced lately will not last (confidence: high)
* Based on long-range forecast models, temperatures seem most likely to be near normal. “Normal” means highs in the low 40s and lows in the upper 20s (confidence: medium).
* The pattern (at least as of today) doesn’t look as cold as January, 2009, around Obama’s first inauguration when highs were sub-freezing (confidence: medium).
* The weather pattern around the inauguration may be drier than normal (confidence: low-medium).
January 21 is still too far away to provide detailed sky conditions, wind speeds, and predict if it will rain or snow.
Here are a series of computer model “ensemble” (a collection of runs from the same model, with tweaks made to initial conditions) simulations which serve as the rationale for the above statements...
The above time series chart shows the forecast temperature difference from normal (or anomaly), covering the period from today through January 27. It is from the GFS model ensemble (or GEFS). The main thing we see is that temperatures are very warm compared to average through early next week but then cool to near average (or perhaps slightly above average) in the middle part of next week. They remain that way through the inauguration.
The above bar chart is basically a simplified version of the chart above it, showing the average high and low temperature from the GFS ensemble members. It indicates a high of 41 and low 34 in Washington, D.C. on January 21.
The above map is a simulation of temperatures at 1 p.m. on January 21 from the European model ensemble. It indicates temperatures should be right around 40 degrees at that time (1 p.m.) in the D.C. area on inauguration day.
For what it’s worth, NOAA’s Climate Prediction Center prediction for the period covering the inauguration is for normal to below normal temperatures and normal to above normal precipitation. NOAA’s outlook is just slightly different from my assessment for near normal temperatures and probably below average precipitation chances.
But note: forecast confidence is just low to moderate overall, and particularly low for precipitation. Tweaks to the forecast are inevitable, and major changes are possible.