Climate Prediction Center - Week 3-4 Outlook

Prognostic Discussion for Week 3-4 Temperature and Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EST Fri Jan 17 2025

Week 3-4 Forecast Discussion Valid Sat Feb 01 2025-Fri Feb 14 2025

The anticipated evolution of the global tropical convective pattern is likely to influence the midlatitude pattern during Weeks 3 and 4. La Niña conditions have emerged across the equatorial Pacific, with the growing negative sea surface temperature anomalies increasingly driving an atmospheric response. Additionally, the subseasonal Madden-Julian Oscillation (MJO) is forecast to become strongly active, with the enhanced convective phase crossing the Indian Ocean and Maritime Continent during the next few weeks. This placement of the MJO enhanced and suppressed convective envelopes would yield constructive interference with the ENSO base state, which could result in a stronger trade wind surge across the central Pacific. Additionally, enhanced convection over the Indian Ocean and Maritime Continent can impact the downstream midlatitude pattern, and is associated with pattern changes favoring positive North Atlantic Oscillation (NAO) structures and increased ridging over eastern North America.

A manual blend of operational dynamical and statistical model guidance was employed, and the resulting 500-mb height anomaly pattern broadly resembles a canonical La Niña response. Strong ridging is favored south of the Aleutians, with above-average height anomalies extending over the Bering Sea. Downstream of this feature, troughing is forecast over the Yukon, with below-average height anomalies extending into the northwestern and north-central CONUS. Ridging is favored along the southern tier of states, with the strongest positive height anomalies over the Southeast. Across the Atlantic, a positive NAO structure is favored, with troughing over Greenland and positive height anomalies to the south over the North Atlantic. Overall this pattern favors enhanced zonal flow, with an increased likelihood of transitory features creating a highly variable pattern during the outlook period.

Cold, arctic airmasses are favored to remain displaced over Canada during the Weeks 3-4 period, making outbreaks of cold airmasses into the CONUS likely. Ridging over the southern tier and Southeast may limit the southward penetration of these airmasses; therefore, above-average temperatures are favored along much of the southern tier, with dynamical model guidance and the manual blend indicating the highest probabilities across the Southeast. Enhanced chances for below-normal temperatures extend across portions of the Northwest and north-central CONUS due to the potential for these cold air outbreaks. While eastward progression of these cold airmasses is likely, the positive NAO structure would promote fairly rapid evacuation of the cold air over the Atlantic. Therefore, a variable pattern is favored for the East. Whether the period ends up above-average or below-average through the entire two-week period is uncertain, and dynamical models offer varying solutions. Continued above-average water temperatures in the Great Lakes may help moderate temperatures as the airmasses progress eastward, and ridging over parts of the Eastern Seaboard may help deflect the colder air. Therefore, equal chances are maintained for the Corn Belt and New England, while a slight tilt towards above-normal temperatures is favored for the central Appalachians and the mid-Atlantic. Across Alaska, enhanced northerly flow with ridging over the Bering Sea and troughing over the Yukon broadly favors below-normal temperatures. Above-average SSTs and ridging north of Hawaii both favor above-normal temperatures during Weeks 3-4.

The Weeks 3-4 precipitation outlook is also broadly consistent with climate anomalies associated with La Niña conditions. Troughing over the Northwest and onshore flow indicates an enhanced likelihood of above-normal precipitation for the Northwest, with dynamical model guidance placing the highest probabilities inland from the Cascades to the northern Rockies. Enhanced probabilities for above-normal precipitation extend eastward to the northern High Plains, where easterly flow from cold high pressure centers pushing southward may induce upslope snow events. There is high uncertainty over California, and climatological precipitation is fairly high this time of year in the absence of a clear signal from the guidance. Below-average precipitation is favored for most of the southern tier, with the highest probabilities extending across southern Arizona and New Mexico. Across the East, transient features may provide sources for multiple storm systems, and dynamical model guidance slightly favors a mean storm track across the Ohio Valley and Great Lakes regions. Therefore, above-average precipitation is favored for much of the eastern third of the CONUS. Across Alaska, northerly flow favors below-average precipitation for the southern tier of the state, while enhanced trades and troughing south of Hawaii both favor above-normal precipitation.

Temperature Precipitation

FCST FCST

Hilo A60 A55

Kahului A60 A55

Honolulu A60 A55

Lihue A60 A55

Forecaster: Adam Allgood

The next week 3-4 outlook will be issued on Friday, Jan 24, 2025

These outlooks are based on departures from the 1991-2020 base period

These are two category outlooks and differ from official current three category outlooks currently used for the monthly and seasonal forecasts.

The shading on the temperature map depicts the most favored category, either above-normal (A) or below-normal (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

The shading on the precipitation map depicts the most favored category, either above-median (A) or below-median (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

In areas where the likelihoods of 2-week mean temperatures and accumulated precipitation amounts are similar to climatological probabilities, equal chances (EC) is indicated.

As of May 19, 2017, the temperature outlook is operational, while the precipitation outlook is still experimental