Hier, la NOAA a publié ses perspectives mensuelles pour décembre 2025. Vous trouverez ci-dessous un résumé pour ceux qui ne connaissent pas la terminologie météorologique, et la discussion complète plus bas pour ceux qui le connaissent.
TL;DR – Décembre 2025 semble prometteur pour les stations balnéaires du nord et de haute altitude, avec des températures plus froides que la moyenne et de bonnes chances de neige dans le nord-ouest du Pacifique, dans les Rocheuses du Nord et dans les Grands Lacs. Les zones du sud et de basse altitude, y compris une grande partie du sud-ouest et du sud-est, devraient rester plus chaudes et plus sèches. Cependant, de courtes vagues de froid pourraient améliorer brièvement les conditions en début de mois.
Perspectives de température de la NOAA pour décembre 2025
Ouest des États-Unis et Rocheuses
Centre et est des États-Unis
Alaska
Précipitations et potentiel de neige de la NOAA en décembre 2025
Montagnes occidentales
Chaînes centrales et orientales
Région des Grands Lacs et nord-est des États-Unis : Les signaux de précipitations supérieurs à la normale suggèrent des trajectoires de tempêtes fréquentes et des éclats de neige potentiels par effet de lac lorsque l’air arctique interagit avec les eaux encore chaudes des lacs.
Vallée de l’Ohio : Plus humide que la moyenne ; le potentiel de neige existe principalement au nord de la rivière Ohio, à mesure que l’air plus froid s’épaissit plus tard dans le mois.
Alaska
Ouest et Nord du continent : Plus humide que la normale, améliorant l’accumulation de neige dans les chaînes du nord.
Sud-est de l’Alaska : Plus sec que la normale sous l’influence de La Niña.
Points clés à retenir pour les domaines skiables
Meilleurs paris pour la neige en début de saison : Cascades, Rocheuses du Nord, Tetons et Grands Lacs du Nord.
Air le plus froid : Probablement dans les États du nord des États-Unis et dans les régions montagneuses si un SSO se développe d’ici le milieu du mois.
Modèle plus variable : Sierra Nevada et Intermountain West, où les changements induits par le MJO pourraient osciller rapidement entre des périodes chaudes et des périodes de neige.
Zones plus douces et plus sèches : Désert du sud-ouest, sud des Rocheuses et sud-est des États-Unis
La discussion complète de la NOAA est ci-dessous :
30-DAY OUTLOOK DISCUSSION FOR DEC 2025 The December 2025 Monthly Outlook was made with ongoing La Niña conditions expected to continue into winter. The most recent weekly Niño 3.4 sea surface temperature (SST) anomaly is about -0.7 degrees Celsius. SST anomalies in the central and east-central equatorial Pacific Ocean remain negative. Outgoing longwave radiation (OLR) anomalies were negative over the far western Pacific Ocean, associated with enhanced convection and precipitation over parts of the Maritime Continent. Positive OLR anomalies, indicating suppressed convection and precipitation, were present near the International Date Line, consistent with La Niña conditions. Low-level (850-hPa) easterly trade winds were enhanced over the western and east-central equatorial Pacific, also consistent with La Niña conditions. Upper-level (200-hPa) wind anomalies were westerly over most of the equatorial Pacific Ocean in recent weeks. Negative subsurface ocean temperature anomalies persisted near the surface in the central and eastern equatorial Pacific Ocean, increasing the likelihood of persistent La Niña conditions. Dynamical model forecasts and the CPC El Niño Southern Oscillation (ENSO) Outlook predict La Niña conditions are most likely to persist for the December-January-February winter season with a probability slightly greater than 50 percent. However, La Niña conditions are most likely to end in the January-February-March season with a probability greater than 60 percent. Although this La Niña is likely to remain weak and be of short duration, predictability of the December climate outlook is largely due to current La Niña conditions. Recently, the upper-level polar vortex has become displaced from the pole and elongated over North America. Recent forecasts from the ECMWF model predict enhanced probabilities of a rare November sudden stratospheric warming (SSW), and propagation of atmospheric temperature anomalies to the surface in polar regions, resulting in a negative Arctic Oscillation (AO). Forecasts of the potential SSW event remain uncertain and change from model run to run. Although there is still substantial uncertainty, an SSW could greatly impact the climate outlook for December over North America. The Madden Julian Oscillation (MJO) has recently been active with enhanced convection currently over the far Western Pacific Ocean. Dynamical models such as the ECMWF predict the potential propagation of the MJO signal eastward into the Western Pacific. The MJO in this phase enhances the chances of cold air intrusion into the north-central contiguous United States (CONUS) in early December extending into the Northeast with time. The combined influence of the MJO, La Niña, and a possible SSW were considered in the December climate outlook. The December temperature and precipitation outlooks were based primarily on dynamical model and statistical model forecasts. Dynamical model forecasts for the month of December are from the North America Multimodel Ensemble (NMME). In addition to the NMME, a consolidation of model forecasts was utilized, which includes the following statistical tools: the Canonical Correlation Analysis (CCA), the Constructed Analog (CA), and an ENSO OCN tool, that combines the impact of ENSO, based on the CPC SST consolidation predicted median Niño 3.4 SST anomaly, with the Optimum Climate Normal (OCN) to represent decadal trends . Daily initialized forecasts from the Climate Forecast System (CFSv2) dynamical model for the month of December and the most recent ECMWF and GEFS dynamical model forecasts for the week 3-4 period that overlaps the beginning of the month of December were also considered. Recent boundary conditions, including coastal SSTs, and soil moisture anomalies, were additional factors considered in the outlook. The December outlook favors above normal temperatures for the eastern Aleutians, western Mainland Alaska, and the North Slope, consistent with dynamical model guidance from the NMME and CFSv2, as well as decadal climate trends. Below normal temperatures are favored for parts of southeastern Mainland Alaska and Southeast Alaska, consistent with dynamical model forecasts from the NMME and CFSv2, as well as the combined impacts of La Niña and the predicted propagation of the MJO into the Western Pacific. The temperature pattern over the CONUS in the December outlook is consistent with the La Niña base state modified by the impacts of MJO and a potential SSW. Above normal temperatures are favored across the southern tier from California, across the Southwest, into the Gulf Coast region and Southeast. Probabilities exceed 50 percent over parts of the Desert Southwest and Rio Grande valley, consistent with recent temperature forecasts from the CFSv2, the consolidation, and decadal trends . Probabilities for above normal temperatures for this region are also enhanced by the correlation between predicted below normal precipitation and above normal temperatures. Probabilities for above normal temperatures over much of California and Nevada are reduced, due to uncertainty related to an active MJO and ECMWF and GEFS forecasts for the first half of the month that show weak signals over much of the West. Probabilities favoring above normal temperatures over the Southeast and parts of the Mid-Atlantic coast are consistent with the impacts of La Niña. Below normal temperatures are favored for the northern CONUS from northern Washington across the Northern Rockies into the northern Great Plains, the Great Lakes region, and along the Canadian border of the Northeast, based on recent forecasts from the CFSv2 model for December, as well as forecasts for the first half of December from the ECMWF model. The predicted temperature pattern is largely consistent with the combined influences of La Niña and MJO propagation into the Western Pacific. Development of an SSW would substantially increase the probabilities of below normal temperatures over the central CONUS. The December outlook favors above normal precipitation for the eastern Aleutians, western Mainland Alaska, and parts of the North Slope, consistent with the consolidation of dynamical and statistical model precipitation forecasts and decadal trends . Below normal precipitation is favored for the southeastern coast of Mainland Alaska including Southeast Alaska, consistent with dynamical model forecasts for December, La Niña, and impacts of a Western Pacific MJO. Above normal precipitation is favored over much of the northwestern CONUS from eastern areas of the Pacific Northwest to the northern High Plains, consistent with the CFSv2 forecast for December and the ECMWF forecast for the first half of the month. Equal Chances (EC) of above and below normal precipitation is indicated closer to the coast of the Pacific Northwest, where the December consolidation forecast and the CPC Week 3-4 Outlook indicate uncertainty in the precipitation signal. Above normal precipitation is also favored for the Ohio Valley, Great Lakes region, and Northeast, consistent with dynamical model forecasts for the first two weeks of December and possible impacts of an active MJO in the Western Pacific and a potential SSW. Below normal precipitation is favored for eastern areas of the Southwest, including parts of Arizona, New Mexico and Texas, and for parts of the Southeast Gulf and Atlantic coasts, consistent with canonical impacts of La Niña and predicted by the NMME and consolidation forecasts. There is greater uncertainty, indicated by EC, in the precipitation outlook for California and western areas of the Southwest. FORECASTER: Dan Collins
