PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU MAR 16 2017

30-DAY OUTLOOK DISCUSSION FOR APRIL 2017

OCEANIC AND MOST ATMOSPHERIC SIGNALS ASSOCIATED WITH LA NINA CONDITIONS HAVE 
DIMINISHED, AND ENSO NEUTRAL CONDITIONS HAVE BEEN IN PLACE SINCE LAST MONTH. 
ONE REMNANT OF PRIOR LA NINA CONDITIONS OBSERVED DURING THE MONTH OF MARCH WAS 
ANOMALOUSLY ABOVE NORMAL OUTGOING LONGWAVE RADIATION NEAR THE DATE LINE 
INDICATING SUPPRESSED CONVECTION AND ANOMALOUSLY BELOW NORMAL OUTGOING LONGWAVE 
RADIATION OVER THE NORTHERN MARITIME CONTINENT AND FAR WESTERN PACIFIC, WHERE 
CONVECTION WAS ENHANCED. THIS PATTERN MAY HAVE BEEN SOMEWHAT DUE TO AN ACTIVE 
SUBSEASONAL MADDEN JULIAN OSCILLATION (MJO). CURRENTLY, THE MJO IS INACTIVE, AS 
INDICATED BY THE WHEELER AND HENDON RMM INDEX. IN CONSIDERATION OF THE CURRENT 
MJO AND ENSO INDICES, MJO AND ENSO DO NOT HAVE AN IMPACT ON THE APRIL CLIMATE 
OUTLOOK. 

ANOMALOUSLY ABOVE NORMAL SNOW PACK AND SOIL MOISTURE OVER THE WESTERN CONUS, 
AND BELOW NORMAL SOIL MOISTURE OVER MUCH OF THE EASTERN CONUS, AS WELL AS ABOVE 
NORMAL SEA SURFACE TEMPERATURES NEAR THE GULF COAST, WERE CONSIDERED IN THE 
APRIL CLIMATE OUTLOOK. HOWEVER, THE HALF-MONTH LEAD APRIL 2017 OUTLOOK RELIES 
PRIMARILY ON MONTHLY FORECASTS FROM DYNAMICAL MODELS, INCLUDING THE CFS AND THE 
NMME, ALSO CONSIDERING WEEK 3-4 FORECASTS FROM THE CFS AND ECMWF ENSEMBLE 
PREDICTION SYSTEMS. 

THE APRIL 2017 TEMPERATURE OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE 
NORMAL TEMPERATURES FOR MUCH OF THE CONUS, AS WELL AS ALASKA. DECADAL TIMESCALE 
TEMPERATURE TRENDS PLAY A SIGNIFICANT ROLE IN INCREASING THE PROBABILITIES OF 
ABOVE NORMAL TEMPERATURES FROM THE SOUTHWEST, ACROSS THE SOUTHERN CONUS, AND 
FOR MUCH OF THE EASTERN CONUS, AS WELL AS ALASKA. NMME PROBABILITIES, 
CALIBRATED USING MULTI-DECADAL HINDCASTS, INDICATE THE GREATEST PROBABILITIES 
FOR ABOVE NORMAL TEMPERATURES TO BE ALONG THE GULF COAST FOR APRIL. THE 
PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE ENHANCED IN THIS REGION BY 
OBSERVED AND PREDICTED ABOVE NORMAL SEA SURFACE TEMPERATURES FOR THE GULF OF 
MEXICO. CALIBRATED NMME PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE WEAKLY 
ENHANCED OVER THE SOUTHWEST. BELOW NORMAL SOIL MOISTURE IN MUCH OF THE EASTERN 
CONUS MAY PLAY A ROLE IN INCREASING THE CHANCES THAT ABOVE NORMAL TEMPERATURES 
WILL PERSIST FOR APRIL MEAN TEMPERATURES. ABOVE NORMAL SNOW PACK IN THE WEST, 
AS WELL AS A PREDICTED TROUGH OVER THE WEST IN CFS AND ECMWF WEEK 3-4 
FORECASTS, ALSO INDICATE LOWER PROBABILITIES OF ABOVE NORMAL TEMPERATURES OVER 
MUCH OF THE WEST. FOR THE FOUR CORNERS REGION, WHERE DECADAL TEMPERATURE TRENDS 
ARE A GREATER FRACTION OF INTERANNUAL TEMPERATURE VARIABILITY, A SMALL 
ENHANCEMENT OF ABOVE NORMAL TEMPERATURE PROBABILITIES IS INDICATED. 

THE APRIL 2017 PRECIPITATION OUTLOOK IS BASED PRIMARILY ON THE PRECIPITATION 
FORECASTS FROM THE CFS AND NMME. CALIBRATED PROBABILITIES OF ABOVE MEDIAN 
PRECIPITATION ARE GREATEST ALONG THE WESTERN GULF COAST FROM TEXAS TO THE 
FLORIDA PANHANDLE, AS INDICATED BY THE NMME, WITH PREDICTED SOUTHERLY FLOW FROM 
THE GULF OF MEXICO. RECENT INITIALIZATIONS OF THE CFS PREDICT A PERSISTENT 
POSITIVE MID-LEVEL HEIGHT ANOMALY OVER THE NORTH PACIFIC FOR APRIL. DOWNSTREAM 
OF THIS POSITIVE ANOMALY, A RELATIVE TROUGH IS PREDICTED OVER THE WESTERN 
CONUS, AND A POSITIVE HEIGHT ANOMALY IS PREDICTED OVER THE EASTERN CONUS INTO 
THE NORTH ATLANTIC. THIS CIRCULATION FORECAST IS ALSO SUPPORTED BY WEEK 3-4 
FORECASTS FROM BOTH THE CFS AND ECMWF ENSEMBLES. THE PROBABILITIES OF BELOW 
MEDIAN PRECIPITATION ARE ENHANCED SLIGHTLY FOR COASTAL REGIONS OF THE PACIFIC 
NORTHWEST, TO THE WEST OF THE PREDICTED TROUGH, WHILE PROBABILITIES OF ABOVE 
MEDIAN PRECIPITATION ARE SLIGHTLY INCREASED OVER THE NORTHERN AND CENTRAL 
PLAINS, AHEAD OF THE PREDICTED TROUGH. PROBABILITIES OF BELOW MEDIAN 
PRECIPITATION ARE ALSO SLIGHTLY ENHANCED FOR THE ALEUTIAN ISLANDS, AS INDICATED 
BY THE NMME CONSENSUS FORECAST. 


FORECASTER: DAN COLLINS


THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, 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 FRI MARCH 31 2017


THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD.

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