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 Mar 21 2025

Week 3-4 Forecast Discussion Valid Sat Apr 05 2025-Fri Apr 18 2025

Recent observations across the global tropics indicate a more coherent Madden-Julian Oscillation event evolving through the first half of March, with the enhanced convective phase now over the Maritime Continent and the suppressed envelope over the Pacific, where it is constructively interfering with the La Niña base state. As the intraseasonal signal continues propagating eastward, decreased coherence is anticipated due to interference between the enhanced phase and a weakening La Niña base state. Therefore, tropical teleconnections into the extratropics during the Weeks 3-4 outlook period are likely to be weak. With the ONI (Oceanic Niño Index) weakening rapidly due to a shallow layer of above-normal sea surface temperatures (SSTs) across the eastern Pacific, the statistical multivariate linear regression model based on tropical signals reflects almost entirely the long term trend signal.

A manual blend of the operational model guidance shows a 500hPa height anomaly forecast somewhat similar to the outlook for Days 8-14. Highly anomalous ridging near and west of the Aleutians that builds during Week-2 is favored to persist during Week-3, and deamplify slightly during Week-4. This feature, coupled with troughing favored over Alaska and western Canada, strongly favors anomalous northerly flow over Alaska. Downstream over the contiguous United States (CONUS), a positive Arctic Oscillation structure favors generally above-average 500hPa height anomalies, with the strongest ridging centered over the Four Corners region and the central Plains during Week-3, and a somewhat less amplified signal in Week-4. Weak troughing is possible over the Pacific Northwest, and some of the guidance favors weaker heights over New England.

The temperature outlook for Weeks 3-4 is based on the operational dynamical model guidance, with some consideration given to experimental tools such as the LIM statistical model and the dynamical model subsampling tool, which identifies ensemble members most closely correlated to the Week-2 guidance. Above-average temperatures are favored for much of the CONUS, with the strongest probabilities extending across the southern Four Corners states and western Texas, near where the strongest ridging is placed during Week-3. A small area of favored below-average temperatures exists across Washington State, due to the potential for troughing to dig far enough south. Equal chances are maintained along a line extending from northern California through northern Wyoming. Equal chances are also maintained for the Northeast, due to a potential for periods of “back-door” cold front activity given the proximity of below-average height anomalies in the manual blend guidance. Across Alaska, below-average temperatures are favored due to the anticipated northerly flow, with the highest probabilities (exceeding 70 percent) across the western half of the state.

The bulk of the enhanced probabilities in the Weeks 3-4 precipitation guidance is associated with three regions with consistent precipitation forecasts. A signal favoring below-average precipitation extends across the Southwest and Four Corners region, which is consistent with the anticipated ridging. Confidence is lower across Texas, where some tools show a potential for enhanced moisture extending northward from Mexico into far western Texas. Equal chances are also maintained for the Plains states, as the Spring season can feature active and rapidly changing patterns. Below average precipitation is also favored for the Southeast and mid-Atlantic, though confidence is lower for extreme southern Florida. In contrast, above-average precipitation is forecast for the upper Midwest and Great Lakes regions, where most of the model guidance depicts an active pattern. Equal chances are maintained for Alaska due to weak signals in the model guidance.

Above-average SSTs and dynamical model guidance favor above-normal temperatures across Hawaii during Weeks 3-4. Above-average precipitation is weakly favored across the islands, with most model guidance depicting weak troughing to the west.

Temperature Precipitation

FCST FCST

Hilo A70 A55

Kahului A70 A55

Honolulu A70 A55

Lihue A70 A55

Forecaster: Adam Allgood

The next week 3-4 outlook will be issued on Friday, Mar 28, 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.