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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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