03/24/2023, 8:25 am EDT

U.S. Medium-range Forecast: Low confidence springtime forecasts yield warmer medium-range results but chilly weather returns extended-range.

Charts of the day: GFS/ECM are suddenly warmer in the 6-10-day period (and they are correct!). Discussion: The 6-10-day forecast by both the ECM and GFS are quite warm in the South and Southeast U.S., a significant warm change. The warmer change is due to an “atmospheric river” storm moving inland and reconvening in the western Great Plains early in the 6-10-day period which inspires warm southwesterly flow ahead of the storm to warm the southeast quadrant of the U.S. The ensembles have the same forecast but are reluctant to warm the surface held back by persistence (of previous forecasts). The GFS has slightly higher skill in the 6-10-day period of late and is chosen as the operational 6-10-day outlook. This is an example of why changes in the operational models in 10-day forecasts are preferred over the persistence-based ensembles. Medium-range 6-10 Day Forecast Valid March 29-April 2, 2023 (24-hour change) Discussion: GFS is selected as the preferred 6-10-day outlook. There is a possibility that New England/New York could be cooler. The overall trend is somewhat warmer in the Central U.S. The western states stay chilly. Medium-range 11-15 Day Forecast Valid April 3-7, 2023 (24-hour change) Discussion: The 11-15-day forecast utilizes the changeable (and warmer than ensembles) GFS forecast. The Northwest trend is milder while the southern states turn cooler. Most notable is the warmer change across the Great Lakes and Quebec. The chilly bias stays mostly in the west and east of that cool zone, a milder solution is likely. U.S. Medium-range Precipitation Forecast Discussion: The GFS projects a streak of heavy precipitation falling as rain and snow Interior West to Upper Midwest in the 6-10-day period. Showers and thundershowers visit the Tennessee Valley. In the 11-15-day period, the East and California turn drier. The Upper Midwest stays wet. Days 16-20 Extended range Temperature Forecast valid April 8-12, 2023 (previous below) Discussion: NCEP CFS V2 returns the cool pattern to central North America which is supported by a possible return of phase_7 of the Madden Julian oscillation indicated by ECMWF 30-day (MJO) forecasts. The wet weather bias is in the East as the West is finally turning drier.