Forecast Central

Forecast of the Day • A National Weather Forecasting Contest

Show All Forecasters Together OR Show Divisions Separately

Thursday January 24, 2019

Assignment: Predict the 24 hr minimum temperature (deg F) for Moline, IL (KMLI)

The next big cold front will push into the Midwest from Canada on Thursday, dropping temperatures to 20 F below average over a wide area. Behind the front, the temperatures can drop very quickly in the cold, extremely dry air, but things like cloud cover and wind speed can make a big difference in how fast the temperature can fall at night. For example, Moline, Illinois (part of the "Quad Cities" region, on both sides of the Mississippi River along the Illinois-Iowa border) should drop to below 0 F on Thursday night, and the National Weather Service says "Winds will lose their gustiness Thursday night, allowing temps to plummet to around 10 below to 20 below zero. These readings could be within several degrees of records. Add winds and dangerous chills will intensify into range of 20 below to 35 below zero, and persist through Friday morning, which will also require headlines". The minimum temperature on Thursday will come at the very end of the day (midnight CST), so let's forecast the Tmin for Moline and see if the temperature will have already gone below 0 F by that time.

Question: Why would lighter winds allow the temperature to "plummet" at night?

Forecasts for Moline, IL (KMLI)
Forecaster Tmin, deg F (error) Comment Day Score
OBSERVED -3 Tmin FINAL (minor problem).
GFS-MOS-00-DAY01 -3 (0) 2.8
GFS-MOS-12-DAY02 -3 (0) 2.8
GFS-MOS-06-DAY02 -3 (0) 2.8
GFS-MOS-18-DAY02 -4 (-1) 2.6
GFS-MOS-00-DAY00 -1 (2) 2.4
GFS-MOS-18-DAY01 -5 (-2) 2.4
GFS-MOS-12-DAY01 -5 (-2) 2.4
NAM-MOS-12-DAY01 0 (3) 2.1
GFS-MOS-06-DAY01 -6 (-3) 2.1
NAM-MOS-00-DAY01 0 (3) 2.1
NAM-MOS-00-DAY00 2 (5) 1.6
NAM-MOS-12-DAY02 2 (5) 1.6
CLIMATE 13.9 (16.9) NCDC Climate Normals, 1981-2010 0