Weather
On Thursday, August 15, the NOAA updated its long-range seasonal forecasts for next winter, giving snow lovers an early glimpse into what 2024/25 might hold.
Based on the outlook discussion, here’s the outlook for early winter 2024-25.
The updated winter outlook suggests that the Pacific Northwest is likely to experience the most snow due to above-normal precipitation, which is consistent with the expected La Niña conditions. This region is anticipated to have a wet winter, making it a prime destination for powderhounds seeking abundant snowfall. On the other hand, the Central Rockies, Southwest, and Southern California are expected to receive below-normal precipitation, which could result in less snow than usual. These areas might not be as favorable for those looking for optimal skiing and snowboarding conditions. The East Coast, particularly the northern parts, may also see increased snowfall due to above-normal precipitation forecasts, offering potential opportunities for winter sports in those regions.
Temperature Outlook
Northeast:
Above-normal temperatures are expected, with a high probability of exceeding 60% for warmer conditions.
Southwest:
Above-normal temperatures are favored, particularly in the early winter months.
Central Rockies:
The Rockies are likely to experience warmer-than-average winter temperatures, although some fluctuations may occur depending on broader climatic influences.
Pacific Northwest:
Initially, there might be equal chances for below, near, or above-normal temperatures, but a shift towards below-normal temperatures is possible later in the winter.
Northern Great Plains and Upper Mississippi Valley:
Above-normal temperatures are slightly favored, but periods of cooler-than-normal temperatures could occur due to the northward tracking of tropical cyclones.
Alaska:
Above-normal temperatures are expected along the North Slope due to low sea ice.
Below-normal temperatures are more likely in southwestern Alaska and the Aleutians.
Precipitation and Snowfall Outlook
Pacific Northwest:
Above-normal precipitation is expected, which could lead to increased snowfall, especially during the peak winter months.
Southwest and Southern California:
Below-normal precipitation is favored, which could result in less snowfall than usual.
Central Rockies:
Similar to the Southwest, below-normal precipitation is likely, potentially reducing snowfall.
East Coast and Southeast:
Above-normal precipitation is expected, which might increase the likelihood of snow events, particularly in the northern parts of these regions.
Alaska:
Western Alaska will likely experience above-normal precipitation, while southern Alaska might see below-normal precipitation. This could affect snowfall patterns accordingly.
These forecasts are influenced by the expected development of La Niña conditions, which typically bring specific weather patterns, such as cooler and wetter conditions in the Pacific Northwest and drier, warmer conditions in the southern U.S. regions.
Here’s the discussion in full from the NOAA, followed by outlook maps for the season:
Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EDT Thu Aug 15 2024 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS El Niño Southern Oscillation (ENSO) conditions are neutral with equatorial sea surface temperatures (SSTs) above average in the western Pacific, near average in the east-central Pacific, and below average in the eastern Pacific. La Niña is favored to develop during September-October-November (66% chance) and persist through the winter 2024-2025 (near 70% chance). The September-October-November (SON) 2024 temperature outlook favors above-normal temperatures across a majority of the contiguous U.S. with the largest probabilities (exceeding 60%) forecast for New England and parts of the Southwest. Increased below-normal temperature probabilities are forecast for southwestern Alaska, while above-normal temperatures are more likely across northern Alaska. The SON 2024 precipitation outlook depicts elevated probabilities for above-normal precipitation along the East Coast, parts of the Pacific Northwest, and western Alaska. Below-normal precipitation is favored for the Central to Southern Great Plains, Central Rockies, Southwest, southern California, and southern Alaska. Areas depicted in white and labeled “Equal-Chances” or “EC” are regions where climate signals are weak, and so there are equal chances for either above-, near- or below-normal seasonal mean temperatures or total precipitation amounts. BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS Note: For Graphical Displays of the Forecast Tools Discussed Below See: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS Equatorial SSTs are above average in the western Pacific, near average in the east-central Pacific, and below average in the eastern Pacific. Weekly observed SST anomalies in the Niño 3.4 region are at 0.0 degrees Celsius. Subsurface temperature anomalies (averaged from 180-100W and 0-300 meters) are near -1.0 degrees Celsius which is a decrease from early July. From July 14 to August 8, OLR anomalies were near average for much of the equatorial Pacific and Maritime Continent. Low-level (850-hPa) wind anomalies were easterly over the east-central and eastern equatorial Pacific. Upper-level (200-hPa) wind anomalies were highly variable east of the Date Line, with easterly anomalies from 160W to 140W and westerly anomalies around 100W. These atmospheric and oceanic conditions reflect a continuation of ENSO-neutral conditions. The Madden-Julian Oscillation (MJO) strengthened during early August with a more coherent wave-1 pattern developing over the global tropics. During the remainder of August, the MJO with anomalous upper-level divergence is forecast to propagate east from Africa to the Indian Ocean and Maritime Continent. This would likely provide a favorable large-scale environment for tropical cyclone development across the main development region of the Atlantic basin through the beginning of September. The MJO is also forecast to result in enhanced trade winds across the equatorial central Pacific which may contribute to negative SST anomalies becoming better established and a transition to La Niña. PROGNOSTIC DISCUSSION OF SST FORECASTS The CPC SST consolidation forecast for Niño 3.4 depicts decreasing negative anomalies during the fall with a -0.6 degree C anomaly persisting from October-November-December 2024 to January-February-March 2025. The CFSv2 has the most negative anomaly (below -1.0 degree C) among the model inputs to the NMME and C3S. The CPC ENSO outlook indicates a likely transition to La Niña during September-October-November with probabilities at or above 70 percent for La Niña conditions to persist during the late fall and early winter 2024-2025. By the spring 2025, ENSO-neutral conditions become more favored. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS The temperature and precipitation outlooks for SON 2024 were based on dynamical model guidance such as the North American Multi-Model Ensemble (NMME) and Copernicus (C3S) along with statistical tools including the global SST-based Constructed Analog and ENSO-OCN. The Calibration, Bridging and Merging (CBaM) tool anchored to the NMME forecasts and "bridged" to the Niño3.4 index was also utilized. The objective, historical skill-weighted consolidation, that combines dynamical and statistical tools, was relied upon in many of the outlooks. La Niña composites were considered for the SON temperature and precipitation outlooks but were used more extensively from OND 2024 to JFM 2025 as its influence on the mid-latitude circulation pattern is expected to increase later this fall and into the winter. Long-term climate trends were considered for all leads, but were relied upon most from the spring 2025 through SON 2025. PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2024 TO SON 2025 TEMPERATURE Above-normal temperatures are favored across a majority of the contiguous U.S. (CONUS) during SON 2024 which is supported by the NMME, C3S, consolidation tool, and decadal trends . Based on the dynamical models and statistical tools, the largest probabilities (above 60 percent) for above-normal temperatures are forecast for New England and parts of the Southwest. Most guidance features a decreasing warm signal closer to the West Coast where equal chances (EC) of below, near, or above-normal temperatures are forecast. The previous seasonal outlook for SON featured EC across the Northern Great Plains and Upper Mississippi Valley. This was shifted to a slight lean for above-normal temperatures due to good agreement among the dynamical models including relatively large probabilities (above 50 percent) in the CBAM + Trend along with the C3S. Although above-normal temperatures are the most likely outcome on the seasonal time scale for the eastern and central CONUS, northward tracking tropical cyclones could alter the mid-latitude circulation pattern and result in periods of cooler-than-normal temperatures for these areas this fall. Above-normal temperatures are favored along the North Slope of Alaska due to low sea ice and decadal trends . Below-normal temperatures are more likely for southwestern Alaska and the Aleutians due to below-normal SSTs along with consistency from the previous month. Minor changes were made to the previous outlooks for OND and NDJ. The slight lean towards below-normal temperatures in parts of the Pacific Northwest (OND and NDJ) and Northern Great Plains (NDJ) was adjusted to EC due to the lack of support from dynamical models and any La Niña cooling influence may be delayed. Also, La Niña cooling is typically most pronounced, beginning in DJF. During OND and NDJ, the latest NMME supports an increase in above-normal temperature probabilities across the Southwest and Central to Southern Great Plains. The major climate driver during the winter and early spring 2024-2025 is expected to be La Niña and the outlooks from DJF 2024-2025 through FMA 2025 reflect this with above-normal temperatures favored for the Southern Great Plains, Lower Mississippi Valley, and Southeast. Elevated below-normal temperature probabilities are forecast for southeastern Alaska and also extend east from the Pacific Northwest to the Northern Great Plains and Upper Mississippi Valley. Later in the spring 2025 and continuing through the summer and fall 2025, decadal trends became the major factor in the temperature outlook. PRECIPITATION The SON precipitation outlook favors below-normal precipitation across the Central to Southern Great Plains, Southwest, and southern California based on the NMME, C3S, and consolidation tool. Given the excellent model agreement and consistency, below-normal precipitation probabilities exceed 50 percent for southern New Mexico and parts of western Texas. Based on the NMME and C3S, elevated below-normal precipitation probabilities extend east to inland areas of the Lower Mississippi Valley. EC were necessary closer to the Gulf Coast due to the potential for heavy precipitation associated with any landfalling tropical cyclones. The likelihood of an active Atlantic hurricane season was the primary factor in favoring above-normal precipitation along the East Coast. In addition, the NMME and C3S support above-normal precipitation for the Southeast and the consolidation tool features a wet signal for both the Southeast and New England. Above-normal precipitation is also favored for the Pacific Northwest and western Alaska based on the NMME and consistent with La Niña composites, while those tools support elevated below-normal precipitation probabilities for southern Alaska. Later in the fall and into the 2024-2025 winter, the three-month precipitation outlooks are based largely on La Niña composites. The spatial coverage for below-normal precipitation probabilities exceeding 50 percent is largest during DJF and JFM across southeastern New Mexico, Texas, and parts of the Southeast where the dry signal is the strongest and occurs most frequently according to La Niña composites. Based on the same reasoning, above-normal precipitation probabilities are at their largest during DJF for the Pacific Northwest. Typically during La Niña, a tight gradient of dry to wet from the Gulf Coast to the Tennessee and Ohio Valleys becomes established during the winter and early spring. The consolidation tool and La Niña composites were relied upon for the Alaska precipitation outlook from OND 2024 to FMA 2025. Similar to the temperature outlook at later lead times, the precipitation outlook during the late spring, summer, and fall 2025 was based largely on decadal trends . FORECASTER: Brad Pugh
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