760  
FXUS07 KWBC 211231  
PMD30D  
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
830 AM EDT THU MAR 21 2024  
 
30-DAY OUTLOOK DISCUSSION FOR APRIL 2024  
 
THE APRIL 2024 MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON  
VARIOUS CLIMATE FACTORS (SUCH AS ENSO AND TO SOME DEGREE, THE MADDEN-JULIAN  
OSCILLATION (MJO)), BOUNDARY CONDITIONS (SNOW DEPTH AND SOIL MOISTURE),  
DYNAMICAL AND STATISTICAL MODEL GUIDANCE, AND HISTORICAL TEMPERATURE AND  
PRECIPITATION TRENDS.  
 
SEA-SURFACE TEMPERATURE (SST) ANOMALIES ACROSS THE CENTRAL AND EASTERN  
EQUATORIAL PACIFIC HAVE SIGNIFICANTLY DECREASED DURING THE PAST FEW WEEKS, AND  
A RELATIVELY SMALL EXTENT OF ANOMALOUSLY COOL WATER HAS APPEARED OVER THE  
EASTERN PACIFIC RELATED TO THE UPWELLING PHASE OF AN OCEANIC KELVIN WAVE.  
COOLER-THAN-AVERAGE SUBSURFACE TEMPERATURES HAVE DEVELOPED OVER MUCH OF THE  
EASTERN PACIFIC. BY MID-MARCH, ENHANCED TRADE WINDS HAVE RETURNED TO A LARGE  
PORTION OF THE EQUATORIAL PACIFIC. ALL THESE FACTORS ARE CONSISTENT WITH A  
RAPIDLY WEAKENING EL NINO, WHICH HAS BEEN IN PLACE FOR JUST OVER ONE YEAR. EL  
NINO IS FORECAST TO TRANSITION TO ENSO-NEUTRAL DURING THE APRIL-MAY-JUNE (AMJ)  
SEASON. HOWEVER, EL NINO IMPACTS ARE EXPECTED TO LINGER WELL INTO THE MONTH OF  
APRIL ACROSS THE UNITED STATES, AND THESE EXPECTED IMPACTS WERE CONSIDERED IN  
THE CONSTRUCTION OF THE APRIL OUTLOOK. ANOTHER CLIMATE FACTOR TO CONSIDER IS  
THE CURRENTLY ROBUST MJO. THE ENHANCED CONVECTIVE PHASE OF THE MJO IS LOCATED  
OVER THE WESTERN PACIFIC (PHASE 7 IN RMM SPACE), AND THE SUPPRESSED PHASE OF  
THE MJO IS LOCATED OVER THE INDIAN OCEAN (PHASES 2 AND 3 IN RMM SPACE). MODEL  
FORECASTS OF THE MJO INDEX PROPAGATE THE MJO SIGNAL INTO THE WESTERN HEMISPHERE  
OVER THE NEXT TWO WEEKS. WITHIN THE FIRST WEEK OF APRIL, LAGGED MJO COMPOSITES  
FOR PHASE 7 FAVOR ANOMALOUSLY COOL TEMPERATURES OVER AT LEAST THE CENTRAL THIRD  
OF THE CONTIGUOUS U.S. (CONUS).  
 
IN ADDITION TO THE CLIMATE FACTORS NOTED ABOVE, THERE IS AN EXTENSIVE AREA OF  
ANOMALOUSLY LOW SNOW DEPTH FROM MONTANA EASTWARD ACROSS THE NORTHERN GREAT  
PLAINS, GREAT LAKES REGION, AND NORTHEAST. FROM EASTERN MONTANA ACROSS THE  
NORTHERN PLAINS SNOW DEPTH DEPARTURES ARE GENERALLY 8 INCHES OR LESS, THOUGH IN  
THE VICINITY OF GREAT FALLS, MONTANA, SNOW DEPTH DEPARTURES RANGE FROM 2-3 FEET  
(LOCALLY GREATER) BELOW NORMAL. FROM THE UPPER MISSISSIPPI VALLEY EASTWARD  
ACROSS THE GREAT LAKES AND NEW ENGLAND SNOW DEPTH RANGES ANYWHERE FROM 8-30  
INCHES BELOW NORMAL. UNUSUALLY LOW SNOW DEPTH MEANS LESS WATER WILL BE  
AVAILABLE FOR STAGGERED RELEASE INTO SOILS DURING THE BEGINNING WEEKS OF THE  
GROWING SEASON. MUCH OF THIS REGION IS ALSO EXPERIENCING RELATIVELY LOW SOIL  
MOISTURE VALUES. THE EXCEPTION IS THE NORTHEAST, WHERE RECENT PRECIPITATION HAS  
RESULTED IN RANKED SOIL MOISTURE PERCENTILES IN EXCESS OF THE 95TH PERCENTILE.  
 
FOR THE APRIL TEMPERATURE OUTLOOK, THERE ARE ELEVATED CHANCES FOR ABOVE-NORMAL  
TEMPERATURES FROM MOST OF THE WEST COAST STATES EASTWARD AND NORTHEASTWARD INTO  
THE NORTHERN PLAINS, CONTINUING EASTWARD AND NOW SOUTHEASTWARD ACROSS THE UPPER  
AND MIDDLE MISSISSIPPI VALLEY, GREAT LAKES REGION, OHIO VALLEY AND NEIGHBORING  
PORTIONS OF TENNESSEE, MOST OF THE APPALACHIANS, AND THE ATLANTIC COASTAL PLAIN  
FROM MAINE TO NORTHERN NORTH CAROLINA. THE FAVORED ABOVE-NORMAL TEMPERATURES  
ARE GENERALLY SUPPORTED BY THE FINAL CONSOLIDATION TOOL (FINAL-CON) WHICH  
SKILL-WEIGHTS A CONSOLIDATION OF DYNAMICAL MODELS (NMME-CON) AND A  
CONSOLIDATION OF STATISTICAL MODELS (STAT-CON). THESE TEMPERATURES ARE ALSO  
GENERALLY SUPPORTED BY THE CONSTRUCTED ANALOG ON SOIL MOISTURE TOOL (CA-SMT),  
AND TO A LESSER DEGREE THE INTERNATIONAL MULTI-MODEL ENSEMBLE (IMME, ALSO  
REFERRED TO AS C3S OR COPERNICUS), CFS, CALIBRATED NMME (PAC), AND GFDL SPEAR  
MODELS. MOST OF THE FAVORED ABOVE-NORMAL TEMPERATURES WERE DERIVED FROM  
DYNAMICAL MODEL GUIDANCE RATHER THAN STATISTICAL MODEL GUIDANCE. EXPECTED  
LAGGED EL NINO IMPACTS ALSO PLAYED A ROLE IN THIS FORECAST, AS WELL AS  
ABOVE-NORMAL SSTS ALONG THE WEST COAST. THE BOUNDARY CONDITIONS NOTED EARLIER  
PLAYED A SIGNIFICANT ROLE IN THE TEMPERATURE FORECAST FROM MONTANA EASTWARD  
ACROSS THE GREAT LAKES AND NORTHEAST. THE PROBABILITIES FAVORING ABOVE-NORMAL  
TEMPERATURES ACROSS NEW ENGLAND AND EASTERN NEW YORK STATE WERE TEMPERED BY  
ANOMALOUSLY HIGH SOIL MOISTURE VALUES. THE 15-YEAR OPTIMAL CLIMATE NORMALS  
(OCN) TEMPERATURE TOOL, A PROXY TO THE LAST 15 YEARS OF HISTORICAL TEMPERATURE  
TRENDS, FAVORED RELATIVE WARMTH ACROSS PORTIONS OF THE FAR WEST, FOUR CORNERS  
STATES, SOUTHERN TEXAS, AND THE MID-ATLANTIC AND NORTHEAST COASTAL PLAIN. THERE  
ARE INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES OVER THE SOUTHERN ROCKIES  
AND SOUTHERN HIGH PLAINS, ASSOCIATED WITH ANOMALOUSLY DRY SOILS, THE THREE CON  
TOOLS (NOTED ABOVE), AND A HIGH SUN-ANGLE. MOST MODEL GUIDANCE SUPPORTED  
ABOVE-NORMAL TEMPERATURE CHANCES FOR MOST OF ALASKA, WITH THE EXCEPTION OF THE  
ALEUTIANS WHERE EQUAL CHANCES (EC) OF BELOW, NEAR, AND ABOVE-NORMAL MONTHLY  
MEAN TEMPERATURES ARE FAVORED.  
 
THE APRIL PRECIPITATION OUTLOOK IS BASED ON THE SAME CLIMATE FACTORS, BOUNDARY  
CONDITIONS, AND MODEL GUIDANCE AS THE APRIL TEMPERATURE OUTLOOK.  
WETTER-THAN-NORMAL CONDITIONS ARE FAVORED FROM APPROXIMATELY THE SOUTHEASTERN  
QUADRANT OF THE CONUS NORTHWESTWARD INTO THE NORTH-CENTRAL HIGH PLAINS. THIS IS  
GENERALLY CONSISTENT WITH THE FINAL AND NMME CONS, UNCALIBRATED NMME, IMME,  
HISTORICAL PRECIPITATION TRENDS, AND LAGGED EL NINO IMPACTS. WELL BELOW-NORMAL  
SNOW DEPTH, ANOMALOUSLY LOW SOIL MOISTURE, AND EXPECTED LAGGED EL NINO IMPACTS  
FAVOR BELOW-NORMAL PRECIPITATION FOR THE UPPER GREAT LAKES REGION. ANOMALOUSLY  
LOW SOIL MOISTURE, HIGH SUN-ANGLE, AND GUIDANCE FROM THE FINAL AND STAT CONS  
FAVOR BELOW-NORMAL PRECIPITATION ACROSS SOUTHWESTERN COLORADO, NEW MEXICO, AND  
MOST OF WEST TEXAS. BELOW -NORMAL PRECIPITATION IS ALSO FAVORED FOR PARTS OF  
THE NORTHWEST, BASED ON MODEL SUPPORT AND LAGGED EL NINO IMPACTS. IN ALASKA,  
THERE WERE SIGNIFICANT DIFFERENCES IN THE PRECIPITATION FORECASTS, THOUGH THE  
IMME, GFDL SPEAR, AND CANADIAN CANCM4I MODELS SUPPORTED AN ELEVATED CHANCE OF  
ABOVE-NORMAL PRECIPITATION ACROSS THE SOUTHERN PART OF THE STATE, INCLUDING THE  
ALASKA PENINSULA.  
 
FORECASTER: ANTHONY ARTUSA  
 
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 APR WILL BE ISSUED ON SUN MARCH 31 2024  
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.  

 
 
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