Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
830 AM EST Thu Dec 19 2024 
 
 
30-DAY OUTLOOK DISCUSSION FOR JANUARY 2025 
 
Following a few months of weakly below normal sea surface temperatures (SSTs), 
SST departures reached -0.6 degrees Celsius in the Niño3.4 region over the past 
week. The current El Niño Southern Oscillation (ENSO) Alert System Status is a 
La Niña watch. The extended period of weakly below normal SSTs and recent drop 
to -0.6 degrees Celsius may lead to some La Niña-like impacts over the 
contiguous United States (CONUS) during January and the upcoming season, 
however, we expect that any impacts may be weak and variability to be high, 
leading to uncertainty in some of the typical impacts. Though the Madden-Julian 
Oscillation (MJO) has been a significant player in the tropics in recent weeks 
and dynamical models  depict continued eastward propagation of the MJO envelope 
with a slowed phase speed, the emerging La Niña has the potential to interfere 
with propagation and amplitude of the MJO. Should the MJO continue into 
January, this may lead to cooler than average temperatures for the northern 
parts of the CONUS and Northeast, but the potential interference from La Niña 
and slow phase speed add to the uncertainty. In addition to the large-scale 
drivers of La Niña and the MJO, coastal or local SSTs, sea ice, and snow cover 
are taken into account for this forecast where appropriate. Monthly forecasts 
of temperature and precipitation by dynamical models  from the North American 
Multi-Model Ensemble (NMME), Copernicus Climate Suite (C3S), and CFSv2 were 
utilized in preparing this Outlook. Week 3-4 predictions for the first part of 
January from GEFSv12, ECMWF, and CFSv2 and the expected transition in the 
atmospheric pattern from the Week 2 period were also considered. 
 
Enhanced ridging is forecast over most of the CONUS toward the end of December, 
leading to the potential for above normal temperatures to end the year. 
However, this strong ridging is expected to moderate by the beginning of 
January, giving way to ridging over the West and neutral to above normal 
heights over the remainder of CONUS. Week 3-4 models forecasting the beginning 
of January favor weak ridging over the West and troughing over the East, though 
the position, exact timing, and strength of the pattern is uncertain. Given the 
atmospheric pattern leading into January and the forecasts for early January, 
we expect a warm start to the month followed by a transient pattern. 
Uncertainty is high due to the potential for this transient pattern, 
particularly for temperatures. 
 
The January 2025 Temperature Outlook features above normal temperatures over 
the southern half of the western CONUS, Southern Plains, and the East Coast. 
This pattern is fairly typical of La Niña, and reflects dynamical model 
predictions that favor a La Niña like response for the month. However, given 
the expected transient height pattern during the month, probabilities are 
overall low for temperatures. Probabilities are enhanced over the Southern 
Plains where there was the best agreement among available tools. Some models 
such as the C3S suite and CFSv2 favored higher probabilities of above normal 
temperatures over the Southwest, however, NMME and statistical tools that 
include decadal trends  which are below normal in parts of the Southwest more 
strongly favor near-normal temperatures. Given this discrepancy, a weak tilt 
toward above normal temperatures is favored despite some of the model results 
showing stronger probabilities in the region, which also aligns with forecast 
below normal precipitation in the region. Similarly, some models indicate 
stronger probabilities for above normal temperatures over the East Coast 
relative to the Outlook, but given Week 3-4 models that tilt toward below 
normal temperatures over the East, probabilities are again weakened. Equal 
chances (EC) of above, near, and below normal temperatures are favored over the 
northern tier of the CONUS and Central Plains where tools had weak or uncertain 
signals, and, moreover, both MJO and La Niña may lead to cold air intrusions 
into the region, though both influences are currently somewhat uncertain. In 
addition, given the forecasted warm start to the month of January, it is 
uncertain if periods of colder temperatures will be strong or long enough to 
tilt the probability to below normal over the northern tier. Over Alaska most 
models favored above normal temperatures, particularly CFSv2, and as such a 
tilt toward above normal temperatures is indicated in the Outlook. 
 
Despite the transient pattern, precipitation signals  were more consistent in 
tools than temperatures. While SSTs in the Niño3.4 region just recently dropped 
below -0.6 Celsius, it is possible that tools are picking up the extended 
period of weakly below normal SSTs and forecasts of a weak La Niña as many of 
the tools are showing a La Niña like precipitation pattern over the CONUS.  For 
example, both NMME and C3S probabilistic multi-model ensemble probabilistic 
forecasts show a general pattern of below normal precipitation over the 
southern tier of CONUS, and above normal precipitation over the Northwest and 
Great Lakes and interior Southeast, which are hallmarks of a La Niña pattern. 
The January 2025 Precipitation Outlook thus resembles a La Niña like pattern, 
featuring enhanced probabilities of above normal precipitation over the 
Intermountain West and parts of the Northern and Central Plains, the Great 
Lakes and interior Southeast, and a tilt toward below normal precipitation from 
the Southwest along the southern CONUS and parts of the coastal Southeast. Over 
Alaska, above normal precipitation is favored for western and northern parts of 
the state, with a small area of below normal precipitation over its southern 
coast. Some uncertainty exists along the West Coast where EC is indicated. NMME 
and C3S favor below normal precipitation over the southern West Coast and above 
normal precipitation over the northern West Coast, while CFSv2 tilts toward 
below normal over the northern West Coast. Given the potential for periods of 
above normal precipitation over the West Coast during winter months, EC is 
favored despite some of the tools leaning toward below normal. Models and tools 
also had mixed signals  along the coastal northeast and New England, and there 
is potential for variability during the month due to uncertainty in storm 
tracks, leading to the favored region of EC. Finally, over Alaska, below normal 
precipitation is favored over its southern coast given La Niña teleconnections, 
and above normal is favored over the western and northern parts of the state 
given La Niña teleconnections, dynamical model agreement, and above normal 
decadal trends  over the northern coast. 
 
 
FORECASTER: Johnna Infanti 
 
The climatic normals are based on conditions between 1991 and 2020, following 
the World Meteorological Organization convention of using the most recent 3 
complete decades as the climate reference period.  The probability anomalies 
for temperature and precipitation based on these new normals better represent 
shorter term climatic anomalies than the forecasts based on older normals. 
 
An updated monthly outlook... for Jan will be issued on Tue December 31 2024 
 
These outlooks are based on departures from the 1991-2020 base period. 
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