PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK 
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 
300 PM EDT THU APR 30 2009 
 
30-DAY OUTLOOK DISCUSSION FOR MAY 2009 
 
SEA SURFACE TEMPERATURE (SST) ANOMALIES ALONG THE EQUATOR IN THE CENTRAL 
PACIFIC OCEAN HAVE CONTINUED TO WEAKEN IN LATE APRIL AND CURRENTLY AVERAGE NEAR 
ZERO FROM ABOUT 160E TO THE SOUTH AMERICAN COAST. THE MADDEN-JULIAN OSCILLATION 
(MJO) IS CURRENTLY ACTIVE WITH THE AREA OF ENHANCED CONVECTION IN THE EASTERN 
PACIFIC OCEAN BUT IS NOT EXPECTED TO PLAY A MAJOR ROLE OUTSIDE OF THE TROPICS. 
WITH ENSO NEUTRAL CONDITIONS EXPECTED IN MAY, THIS OUTLOOK PRIMARILY REFLECTS 
THE FORECAST FROM DYNAMICAL WEATHER PREDICTION MODELS IN THE FIRST TWO WEEKS OF 
THE MONTH, THE CFS MONTHLY TEMPERATURE AND PRECIPITATION PREDICTIONS, SOIL 
MOISTURE ANOMALIES, AND LOCAL SSTS ALONG COASTAL AREAS. 
 
 THE MONTHLY OUTLOOK CALLS FOR ENHANCED CHANCES OF ABOVE NORMAL TEMPERATURES 
FROM TEXAS TO THE SOUTHERN GREAT BASIN.  THIS IS FROM SIGNALS FROM THE CFS AND 
SMLR, WITH SOIL MOISTURE PROVIDING THE PREDOMINATE SIGNAL IN THE SMLR FORECAST 
IN TEXAS.  AN AREA OF ELEVATED CHANCES FOR ABOVE NORMAL TEMPERATURES WAS ADDED 
TO THE ORIGINAL OUTLOOK ISSUED IN MID APRIL IN PORTIONS OF THE SOUTHEASTERN 
CONUS, DUE TO AN EXPECTED WARM START TO THE MONTH.  BELOW NORMAL SSTS IN THE 
EASTERN PACIFIC OCEAN FAVOR BELOW NORMAL TEMPERATURES ALONG THE PACIFIC COAST 
FROM ALASKA TO CENTRAL CALIFORNIA.  THE CHANCES FOR BELOW NORMAL TEMPERATURES 
ARE ALSO ENHANCED IN PARTS OF THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI 
VALLEY ACCORDING TO SIGNALS FROM THE CFS AND SMLR, WITH THE SMLR SIGNALS 
PRIMARILY ASSOCIATED WITH WET SOIL MOISTURE CONDITIONS IN THE AREA.  THE SHORT 
TERM WEATHER FORECAST FOR THE FIRST 7 DAYS OF THE MONTH IN THIS REGION IS FOR 
SLIGHTLY BELOW NORMAL TEMPERATURES, AS ARE THE EXTENDED RANGE WEATHER FORECAST 
FOR THE SECOND WEEK OF MAY, SLIGHTLY INCREASING THE CONFIDENCE FOR BELOW NORMAL 
TEMPERATURES IN THE NORTHERN PLAINS WHEN COMPARED TO THE EARLIER PREDICTION 
ISSUED IN MID-APRIL. 
 
AN ACTIVE STORM TRACK IS EXPECTED TO INFLUENCE THE CONUS FROM THE CENTRAL 
CALIFORNIA COAST TO NEW ENGLAND.  THIS SUBSTANTIALLY INFLUENCES THE UPDATED 
PRECIPITATION OUTLOOK FOR MAY OVER LARGE PORTIONS OF THE COUNTRY.  SIGNIFICANT 
PRECIPITATION IS EXPECTED IN THE FIRST WEEK OF MAY ALONG THE WEST COAST FROM 
CENTRAL CALIFORNIA TO COASTAL OREGON, RESULTING IN AN INCREASED CHANCE THAT 
MONTHLY TOTALS WILL BE IN THE ABOVE MEDIAN CATEGORY.  UNSETTLED WEATHER WITH A 
GOOD CHANCE FOR PRECIPITATION IS EXPECTED FOR THE INTERMOUNTAIN WEST AND 
CENTRAL ROCKIES IN THE FIRST WEEK OF MAY, AND THIS WILL MAKE IT LESS LIKELY 
THAT MONTHLY PRECIPITATION TOTALS THERE WILL BE BELOW MEDIAN AS INDICATED ON 
THE ORIGINAL MAY OUTLOOK. THE CFS CONTINUES TO SUGGEST ENHANCED CHANCES OF 
BELOW MEDIAN PRECIPITATION AMOUNTS FOR THE CENTRAL ROCKIES AND INTERMOUNTAIN 
WEST BEYOND THE SHORT TERM, SO THE MONTHLY PRECIPITATION TOTALS FOR THAT REGION 
ARE UNCERTIAN.  CONDITIONS ARE VERY FAVORABLE FOR WET CONDITIONS FROM 
NORTHEASTERN TEXAS TO THE LOWER GREAT LAKES IN THE FIRST TWO WEEKS OF THE 
MONTH, ELEVATING CHANCES FOR ABOVE MEDIAN MONTHLY PRECIPITATION TOTALS IN THOSE 
REGIONS.  ABOVE MEDIAN PRECIPITATION AMOUNTS CONTINUE TO BE SLIGHTLY FAVORED IN 
PARTS OF THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY BY THE CFS AND 
TOOLS BASED ON SOIL MOISTURE. 
 
FORECASTER: DAVID UNGER 
 
NOTES: AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL 
PROBABILITIES) ARE NOW LABELED AS EC (EQUAL CHANCES). 
 
THE NEXT MONTHLY OUTLOOK...FOR JUNE 2009...WILL BE ISSUED ON THU MAY 21 2009 
 
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1971-2000 BASE PERIOD. 
 
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