Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
300 PM EDT Fri Mar 31 2023 
 
 
30-DAY OUTLOOK DISCUSSION FOR APRIL 2023 
 
The updated temperature and precipitation outlooks for April 2023 reflect 
recent dynamical model guidance from the GEFS and CFSv2, as well as current WPC 
week 1 outlooks and the CPC week 2 and week 3-4 outlooks. The Madden Julian 
Oscillation (MJO) was recently active with convective activity over the 
Maritime Continent, although the Real-time Multivariate MJO (RMM) index now 
indicates a reduced MJO signal, as subseasonal variability interacts with the 
background climate state. Dynamical models , such as the ECMWF and GEFS, 
forecast a possible reemergence of the MJO signal over the tropical Pacific. 
However, there is uncertainty in the timing and phase of a future MJO signal 
and potential impacts to the temperature and precipitation patterns over North 
America. While the recent La Niña event has ended, residual atmospheric 
conditions similar to La Niña continue, such as suppressed convection near the 
date line. 
 
The updated April temperature outlook indicates an expansion of enhanced 
probabilities for below normal temperatures for the western and north-central 
contiguous U.S. (CONUS), due to recent dynamical model guidance and outlooks 
for the beginning of the month. WPC temperature outlooks for the first week of 
April indicate a very similar temperature pattern, as do recent CPC 6-10 day 
period outlooks and dynamical model consolidation tools. The updated April 
temperature outlook shows a reduction in the probabilities favoring above 
normal temperatures for parts of the Southwest, while continuing to indicate 
likely above normal temperatures for the Southern Plains, the Central and Lower 
Mississippi Valley, the Ohio Valley, the Southeast, and the Mid-Atlantic 
region. This pattern of below and above normal temperatures across this CONUS 
is supported by the CFSv2 model guidance for the month, in addition to the WPC 
and CPC outlooks for the beginning of the month. Above normal temperatures are 
favored for a small coastal area of northwestern Alaska, while below normal 
temperatures are favored for the south coast of the Alaska Mainland, supported 
primarily by the most recent CFSv2 model forecasts. A considerable increase in 
uncertainty leads to a forecast of equal chances (EC) of above, near and below 
normal temperatures for much of Alaska, with conflicting signals  among various 
tools. 
 
The updated April precipitation outlook indicates an increased probability of 
above normal precipitation for the Pacific Northwest, supported by recent WPC 
outlooks for the first week of the month, the CFSv2 April precipitation 
forecast, and the CPC Week 3-4 Outlook. The area of enhanced probabilities of 
below normal precipitation over parts of the Southwest has decreased in the 
updated April Outlook, with increased chances of precipitation in both the CPC 
8-14 day outlook and the Week 3-4 Outlook over eastern areas of the Southwest, 
and over parts of Central California in the first week of April. The updated 
April precipitation outlook indicates increased probabilities of above normal 
precipitation from East Texas across the Lower Mississippi Valley into the Ohio 
and Tennessee Valleys, as well as for eastern areas of the Northern Plains, the 
Great Lakes region, and western New York state. Chances of above normal 
precipitation for the month of April are increased over these areas by 
precipitation forecasts for the first week of the month. Probabilities exceed 
50 percent for parts of East Texas northeastward to the Mississippi, where 
predicted precipitation in the first week approaches April climatological 
precipitation amounts. 
 
The April precipitation outlook favors above normal precipitation for 
northwestern Alaska into parts of the Alaska interior and below normal 
precipitation for the Alaska Peninsula and the southwestern coast, supported by 
the most recent CFSv2 model forecasts and consistent with precipitation 
outlooks for the start of the month. An area of enhanced probabilities for 
below normal precipitation over the Alaska Panhandle has been removed in the 
updated outlook, considering recent outlooks for week 2 and weeks 3 and 4. 
 
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***** The previous discussion from mid-March is below ***** 
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The La Niña event has ended as of March, 2023. Sea surface temperature (SST) 
anomalies have tended towards positive across most of the equatorial Pacific 
Ocean in recent weeks, and the most recent Niño 3.4 region anomaly is 
approaching zero degrees Celsius. The East Pacific is particularly warm with an 
anomaly of +1.5 C in the Niño 1+2 region. Easterly equatorial wind anomalies 
over the Pacific Ocean have weakened in the last month and are confined to a 
small area of the central Pacific. Upper-level westerly wind anomalies 
continued over the eastern equatorial Pacific. Positive subsurface temperature 
anomalies observed in the western and central equatorial Pacific Ocean have 
expanded eastward, while extending towards the surface in the eastern Pacific 
Ocean. Negative subsurface temperature anomalies near the surface of the 
central Pacific Ocean have weakened. Although ENSO-neutral conditions are 
predicted in the official ENSO outlook to continue through the Northern 
Hemisphere spring, a rapid warming of the Niño 3.4 region SST anomaly is 
forecast by most statistical and dynamical models , with an increasing chance of 
an El Niño from summer into autumn. Consolidated dynamical model forecasts from 
the North America Multi-Model Ensemble (NMME) predict positive SST anomalies in 
the Niño 3.4 region, bordering on El Niño conditions near the 0.5 degree C 
threshold, from summer through autumn. The Madden-Julian Oscillation (MJO) 
strengthened significantly in the beginning of March with convective activity 
currently over the Western Hemisphere. Dynamical model forecasts of the 
Real-time Multivariate MJO (RMM) index indicate a weakening MJO signal 
propagating eastward into the Indian Ocean towards the end of March. 
 
The ECMWF dynamical model forecasts for the beginning of April indicate likely 
below-normal temperatures for much of the western contiguous U.S. (CONUS) and 
parts of the northern Great Plains. Anomalous snowpack and snow cover over 
parts of the West play a role in the temperature outlook for April. In addition 
to surface boundary conditions, near-coastal sea surface temperature anomalies 
were considered. Linear regression forecasts based on the RMM index indicate a 
potential for below-normal temperatures across much of the CONUS at the 
beginning of April, followed by warming, particularly in the East. The 
temperature and precipitation outlooks for April are based primarily on a 
skill-weighted consolidation of dynamical model forecasts from the North 
America Multi-Model Ensemble (NMME). Statistical tools, such as the Canonical 
Correlation Analysis (CCA), Constructed Analog (CA), and a linear regression 
model based on the CPC SST Consolidation forecast of the Nino 3.4 index and 
decadal trends  were considered, but played a lesser role given the uncertainty 
of ENSO-related signals  given the rapid transition in the ENSO state. In 
addition, skill-based consolidations of statistical and dynamical tools for 
temperature and precipitation were consulted. 
 
The April Monthly Outlook favors below-normal temperatures for southwestern 
Alaska, as indicated by the NMME consolidation tool, with negative SST 
anomalies along the coast contributing to cooler temperatures. Above-normal 
temperatures are favored for northeastern Alaska, supported by the NMME 
consolidation tool, as well as the statistical forecast tool consolidation. The 
probability of below-normal temperatures is enhanced in the Pacific Northwest, 
Northern Rockies, and parts of the Great Basin, supported by recent CFSv2 and 
ECMWF dynamical model forecasts for April, and consistent with areas of 
anomalous snow cover and deep snowpack. Negative SST anomalies near the Pacific 
coast contribute to an increased likelihood of below-normal temperatures for 
the coasts of California, Oregon and Washington. Above-normal temperatures are 
favored from parts of the Southwest eastward across the Southern Plains, and 
from the Gulf Coast region northward across the eastern CONUS, as indicated by 
the NMME model forecasts. Strong positive SST anomalies along the Gulf Coast 
increase the likelihood of above-normal temperatures. Conflicting signals  in 
the temperature forecast tools lead to equal chances of below, near and 
above-normal temperatures in the April outlook over a large area of the 
north-central CONUS. 
 
Above-normal precipitation is favored for parts of the west coast of Alaska, as 
indicated in the precipitation consolidation of dynamical and statistical tools 
and the CFSv2 model forecasts. Below-normal precipitation is slightly favored 
for parts of the south coast of Alaska, as predicted by the NMME precipitation 
anomaly forecast. Below-normal precipitation is favored for a large area of the 
western CONUS from California and southern Oregon to the Central and Southern 
Rockies, as predicted by most dynamical and statistical model forecasts and 
consistent with decadal precipitation trends  for April. Above-normal 
precipitation is favored from the western Gulf Coast region northward into 
parts of Oklahoma and Arkansas, as predicted by the dynamical and statistical 
model forecast consolidation. Above-normal precipitation is also favored for 
parts of the Midwest and Great Lakes region, supported by recent dynamical 
model forecasts such as the CFSv2 and ECMWF, and consistent with decadal 
precipitation trends  for April. 
 
FORECASTER: Dan Collins 
 
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. 
 
The next monthly outlook...for May ... will be issued on Thu Apr 20 2023 
 
These outlooks are based on departures from the 1991-2020 base period. 
$$