The computer forecast is suggesting that a change is imminent, as the latest computer MOS (model output statistics) forecast indicates low temperatures of -24 °F and -27 °F on Thursday and Friday of this week respectively. The computer forecast also shows highs well below zero. However, the National Weather Service forecasters apparently aren't buying it, as the coldest low temperature in the official forecast is -11 °F and the coldest high is 3 °F. Here's the NWS forecast and the last two iterations of the MOS forecast:
The NWS forecast discussion doesn't offer any hints as to why colder conditions aren't expected. The GFS model forecasts of the 500 mb height and the sea-level pressure on Thursday afternoon are shown below; with a surface high retreating to the east and a pressure gradient persisting, the set-up doesn't look ideal for cold, but if winds go calm under clear skies it will undoubtedly get chilly.
The current forecast discrepancy reminds me of the result I showed last month concerning the temperature bias in the winter high temperature forecasts from the NWS. In the past three winters the NWS high temperature forecasts have been too cold on average for Fairbanks, even at shorter lead times; perhaps the forecasters have also recognized this and are now trying to correct for it. The chart below shows the daily error of the day-1 high temperature forecasts from the past 3 winters; the day-1 forecast would be (for example) the forecast issued on Tuesday morning for the high temperature on Wednesday.
The forecast bias was particularly persistent last winter, when 87% of all days ended up warmer than the forecast indicated. It was a warm winter overall, so it's not surprising that the bias was greater than in the previous two winters, which were slightly colder than normal.
Readers should note that none of this discussion should be construed as criticism of the NWS forecasts or personnel; their services are tremendously valuable in a myriad of ways and I applaud their efforts and dedication.
[Update November 29: the NWS forecast ended up closer to the truth than the MOS, as we would hope. The lowest temperature observed at the airport was -18 °F and the lowest "daytime" high temperature was -1 °F. Here are the recent day-1 high temperature forecasts and the observed maximum temperatures from 3am to 9pm AKST:
Readers should note that none of this discussion should be construed as criticism of the NWS forecasts or personnel; their services are tremendously valuable in a myriad of ways and I applaud their efforts and dedication.
[Update November 29: the NWS forecast ended up closer to the truth than the MOS, as we would hope. The lowest temperature observed at the airport was -18 °F and the lowest "daytime" high temperature was -1 °F. Here are the recent day-1 high temperature forecasts and the observed maximum temperatures from 3am to 9pm AKST:
Forecast for Wednesday: +7 °F
Observed: +12 °F
Forecast for Thursday: -2 °F
Observed: -1 °F
Forecast for Friday: -2 °F
Observed: +5 °F
Remarkably we see that the day-1 high temperature forecasts were too cold again.]