Highlight: La Nina extremes; warm medium-range forecasts. Winter gas population weight HDD forecast steadily warmer.
Fig. 1: NOAA/NWS weather watch, warning and advisory areas.
Discussion: A classic La Nina-look this Sunday afternoon as Pacific westerlies aloft reach down to ground level causing high wind across the North-central Great Plains, Midwest U.S. and across the Great Lakes to western New York while just north of that high wind stretch a winter storm is unloading heavy snow across the northern Great Plains and Upper Midwest (Fig. 1). A sure sign of mild La Nina climate in the southern states are the nightly fogs likely to regenerate again tonight.
Unseasonably mild temperatures are pushed into the East tomorrow ahead of a cold front. The Mid-Atlantic States reach the 70’s tomorrow with 60’s into southern New England. Tomorrow’s cold front could span thunderstorms from Louisiana to New England. The cold front stalls into midweek from the Southeast U.S. to coastal Northeast Corridor. Rain could end as snow Interior Northeast Wednesday as colder air arrives. Meanwhile a series of cold front with light to moderate precipitation move across the western states this week. Heaviest precipitation will stretch across the Cascades.
In the medium-range, forecast models remain warm Central and East while the West is cool – classic -PNA/+NAO thermal pattern (Fig. 2-3). Expect a wet pattern for Tennessee to Ohio in the 6-10-day period shifting westward to Missouri to Illinois in the 11-15-day period. Forecast models indicate wet weather for California in the 6-10-day period.
Fig. 2-3: The ECM ENS medium-range temperature anomaly forecast.
Fig. 4: Using all models, the U.S. gas population weight HDD forecast for the U.S. through mid-December identifying the consensus forecast, outlook from 24 hours ago and the 30-year/10-year normal.
The U.S. gas population weight HDD forecast edges warmer than 24 hours ago earlier today (Fig. 4). The outlook is considerably warmer than normal. The November gas population weight HDD was 552 compared to the 30-year normal of 589. The rank was 11th warmest of the past 20 years compared to the second warmest on record last year (Fig. 5). The updated HDD ranking forecast for the remainder of winter is trending warmer and now ranks in the too 7 warmest for the past 20 years each of the next 4 months.
Fig. 5: Versus the 30-year normal, the HDD rank for each month of the cold season 2021-22 of the past 20 years.