PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 300 PM EDT TUE JUL 31 2018 30-DAY OUTLOOK DISCUSSION FOR AUGUST 2018 THE UPDATED MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS FOR AUGUST 2018 ARE BASED ON THE LATEST MODEL GUIDANCE AND RECENT SHORT AND EXTENDED RANGE OUTLOOKS FROM NCEP CENTERS. THE UPDATED TEMPERATURE OUTLOOK FOR AUGUST IS SIMILAR OVERALL TO THE AUGUST TEMPERATURE OUTLOOK RELEASED ON JULY 19, WITH SOME CHANGES. ABOVE NORMAL AVERAGE TEMPERATURES FOR AUGUST ARE INCREASINGLY LIKELY FOR THE WESTERN CONUS, WITH DYNAMICAL MODEL FORECASTS FOR MOST AREAS OF THE WEST AT THE BEGINNING OF THE MONTH INDICATING POSITIVE ANOMALIES, AS WELL AS GUIDANCE FROM THE NCEP CFS FOR THE FULL MONTH. BELOW NORMAL TEMPERATURES ARE MOST LIKELY FOR PARTS OF THE PACIFIC NORTHWEST EARLY IN THE MONTH. HOWEVER, BY THE END OF THE MONTH, ABOVE NORMAL TEMPERATURES ARE MORE LIKELY FOR THE ENTIRE WEST. DYNAMICAL MODEL FORECASTS, INCLUDING THE CFS, INDICATE AN INCREASED POTENTIAL FOR BELOW NORMAL TEMPERATURES OVER THE NORTHERN CENTRAL AND SOUTHEASTERN CONUS DURING THE FIRST HALF OF WEEK 1. GUIDANCE FOR THE AVERAGE TEMPERATURES FOR THE WEEK 3 AND 4 PERIOD, INCLUDING THE CFS, ECMWF, AND SUBSEASONAL EXPERIMENT (SUBX) ENSEMBLES, INDICATE BELOW NORMAL TEMPERATURES MAY RETURN LATE IN THE MONTH. HOWEVER GUIDANCE FOR THE WEEK 2 PERIOD, DECADAL TRENDS, AND SEASONAL CLIMATE SIGNALS INDICATE LOW PROBABILITIES THAT AVERAGE AUGUST TEMPERATURES WILL BE BELOW NORMAL. EQUAL CHANCES OF ABOVE, NEAR AND BELOW NORMAL TEMPERATURES IS INDICATED FOR A LARGE AREA OF THE NORTHERN AND CENTRAL PLAINS, THE UPPER AND CENTRAL MISSISSIPPI VALLEY, THE OHIO VALLEY, AND PARTS OF THE SOUTHEAST TO THE ATLANTIC COAST. ABOVE NORMAL TEMPERATURES CONTINUE TO BE LIKELY FOR THE NORTHEAST, AS INDICATED BY FORECAST GUIDANCE FOR WEEKS 1 THROUGH 4. ABOVE NORMAL TEMPERATURES ARE LIKELY FOR MUCH OF THE SOUTHERN PLAINS, FOLLOWING FORECAST GUIDANCE FOR WEEK 2 FROM THE GEFS AND ECMWF ENSEMBLES, AND FOR WEEKS 2 THROUGH 4 FROM VARIOUS MEMBER MODELS OF SUBX. INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES ARE INDICATED FOR ALL REGIONS OF ALASKA, WHERE MODEL FORECASTS INDICATE BELOW NORMAL TEMPERATURES DURING WEEK 2 AND ABOVE NORMAL TEMPERATURES AT THE BEGINNING AND END OF THE MONTH. THE UPDATED PRECIPITATION OUTLOOK FOR AUGUST IS SIMILAR OVERALL TO THE AUGUST PRECIPITATION OUTLOOK RELEASED ON JULY 19, BUT INDICATES SIGNIFICANT CHANGES IN THE OUTLOOK FOR THE EASTERN CONUS, AS WELL AS SMALLER CHANGES IN OTHER REGIONS. FORECAST GUIDANCE FOR WEEKS 1 THROUGH 4 INDICATE AN INCREASED PROBABILITY OF ABOVE NORMAL PRECIPITATION OVER MUCH OF THE EASTERN CONUS, FROM THE EASTERN GREAT LAKES REGION, SOUTHWARD INTO THE OHIO VALLEY AND MID-ATLANTIC REGION, TO THE SOUTHEAST AND EASTERN GULF COAST STATES. WPC FORECASTS INDICATE A GREATER PROBABILITY OF PRECIPITATION THAN PREVIOUSLY ACROSS PARTS OF THE CENTRAL PLAINS DURING THE END OF WEEK 1. HOWEVER, MODEL GUIDANCE, INCLUDING THE CFS AND SUBX ENSEMBLE MODELS, FOR THE FIRST HALF OF THE MONTH INDICATES BELOW NORMAL PRECIPITATION IS LIKELY FOR MUCH OF THE CENTRAL AND SOUTHERN PLAINS. DYNAMICAL MODEL FORECASTS AND THE CPC EXPERIMENTAL PRECIPITATION OUTLOOK FOR WEEKS 3 AND 4 INDICATE ABOVE NORMAL PRECIPITATION IS MORE LIKELY THAN BELOW NORMAL FOR PARTS OF THE CENTRAL PLAINS, INCLUDING SOUTHERN NEBRASKA, KANSAS, AND NORTHERN OKLAHOMA, LATE IN THE MONTH. THE UPDATED MONTHLY OUTLOOK INDICATES BELOW NORMAL PRECIPITATION FOR AUGUST REMAINS LIKELY FOR A SMALLER AREA OF THE SOUTHERN PLAINS, EXTENDING NORTHWARD INTO CENTRAL OKLAHOMA. ABOVE NORMAL PRECIPITATION CONTINUES TO BE LIKELY FOR MUCH OF THE SOUTHWEST, FROM SOUTHERN CALIFORNIA INTO PARTS OF THE THE FOUR CORNERS STATES, SUPPORTED BY THE LATEST MODEL GUIDANCE FROM THE CFS, AS WELL AS OTHER ENSEMBLE PREDICTION SYSTEMS. ABOVE NORMAL PRECIPITATION CONTINUES TO BE LIKELY FOR WESTERN ALASKA, SUPPORTED BY DYNAMICAL MODEL FORECASTS, INCLUDING THE CFS. THE PREVIOUS DISCUSSION FROM THE HALF-MONTH LEAD MONTHLY FORECAST FOLLOWS. _____________________________________________________________________________ THE AUGUST 2018 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL MODEL GUIDANCE, STATISTICAL FORECASTS, CURRENT SOIL MOISTURE CONDITIONS, AND POTENTIAL INFLUENCES FROM MODES OF TROPICAL VARIABILITY. THE STATE OF ENSO DOES NOT IMPACT THE FORECAST, AS ENSO-NEUTRAL CONDITIONS ARE EXPECTED THROUGH MOST OF SUMMER, WHILE AN EL NINO WATCH HAS BEEN ISSUED INDICATING THAT EL NINO CONDITIONS ARE LIKELY THEREAFTER. THE MADDEN-JULIAN OSCILLATION (MJO) IS ACTIVE WITH CONVECTION LOCATED OVER THE MARITIME CONTINENT AND PREDICTED BY SOME MODELS TO POSSIBLY MOVE INTO THE WESTERN PACIFIC IN THE NEXT WEEK. BECAUSE THERE IS SIGNIFICANT UNCERTAINTY IN THE MJO DYNAMICAL MODEL FORECASTS, AND MJO IMPACTS ON NORTH AMERICAN TEMPERATURE AND PRECIPITATION PATTERNS IS LIMITED AT THIS TIME OF YEAR, MJO DID NOT PLAY A ROLE IN THE AUGUST OUTLOOKS. MODEL FORECASTS FROM THE NMME, MORE RECENT RUNS FROM THE CFS, AND TRENDS FAVOR ABOVE NORMAL TEMPERATURES ACROSS THE WESTERN CONUS, AS WELL AS THE NORTHEAST. ABOVE NORMAL TEMPERATURES ARE MOST LIKELY FOR WESTERN AND SOUTHERN PARTS OF ALASKA, WITH ABOVE AVERAGE SEA SURFACE TEMPERATURES (SSTS) PRESENT IN THE GULF OF ALASKA AND BERING SEA, AND PREDICTED TO PERSIST BY DYNAMICAL MODEL FORECASTS FROM THE NMME. UNCERTAINTY IS GREATER FOR NORTHEASTERN ALASKA AND THE ARCTIC COAST, WHERE SSTS HAVE BEEN BELOW NORMAL AND MODELS SHOW GREATER UNCERTAINTY. RECENT RUNS OF THE CFS CONSISTENTLY PREDICT ABOVE NORMAL TEMPERATURES ARE LIKELY FOR THE SOUTHERN PLAINS, AS WELL AS WESTERN AREAS OF THE CENTRAL AND LOWER MISSISSIPPI VALLEY, AS FAR NORTH AS MISSOURI. CONTINUING DRY SOIL MOISTURE CONDITIONS ALSO SUPPORT ENHANCED CHANCES OF ABOVE NORMAL TEMPERATURES FOR AUGUST IN THIS REGION. PROBABILITIES OF ABOVE NORMAL TEMPERATURES EXCEED 50 PERCENT FOR SOUTHERN AREAS OF TEXAS, LOUISIANA AND FLORIDA, INFLUENCED BY ABOVE AVERAGE SSTS FOR THE GULF OF MEXICO. DYNAMICAL MODEL FORECASTS FOR THE BEGINNING OF AUGUST, INCLUDING THE CFS AND THE ECMWF ENSEMBLE PREDICTION SYSTEM, AS WELL AS RECENT FORECASTS FROM THE SUBSEASONAL EXPERIMENT (SUBX) MODELS, INDICATE LIKELY BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN PLAINS INTO WESTERN AREAS OF THE MIDWEST, WHILE CALIBRATED PROBABILITY FORECASTS FROM THE NMME INDICATE WEAK PROBABILITIES OF ABOVE NORMAL TEMPERATURES OR EQUAL CHANCES OF ABOVE AND BELOW NORMAL. AN AREA OF EQUAL CHANCES IS INDICATED IN THE NORTH-CENTRAL CONUS, WHERE THERE IS GREATER UNCERTAINTY IN THE MEAN AUGUST TEMPERATURES. WEAK PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE INDICATED FOR MUCH OF THE EASTERN CONUS, WHERE SKILL IS LOWER, AND FORECASTS INDICATE BELOW NORMAL TEMPERATURES AT THE BEGINNING OF AUGUST. PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR THE SOUTHWEST MONSOON REGION ARE LOWER, WHERE ENHANCED PRECIPITATION MAY MODERATE TEMPERATURES. MODEL FORECASTS FROM THE NMME AND RECENT RUNS OF THE CFS INDICATE ABOVE NORMAL PRECIPITATION IS LIKELY FOR MUCH OF THE WESTERN CONUS, INCLUDING THE SOUTHWEST MONSOON REGION, EXTENDING NORTHWARD INTO SOUTHERN AREAS OF IDAHO AND WYOMING. ENHANCED PROBABILITIES OF ABOVE NORMAL PRECIPITATION EXTEND INTO SOUTHERN CALIFORNIA, AS CONVECTIVE ACTIVITY OVER THE EAST PACIFIC MAY LEAD TO MOISTURE SURGES INTO THIS REGION. IF THE MJO REMAINS ACTIVE AND ENHANCED CONVECTION DUE TO MJO PROGRESSES EASTWARD, MOISTURE TRANSPORT INTO THE WEST COAST MAY BE FURTHER INCREASED. ABOVE NORMAL PRECIPITATION IS LIKELY FOR WESTERN ALASKA, AS INDICATED BY THE NMME AND CFS FORECASTS. PROBABILITIES OF ABOVE NORMAL PRECIPITATION ARE ALSO SLIGHTLY ENHANCED FOR PARTS OF THE ATLANTIC COAST FROM NORTHERN FLORIDA TO VIRGINIA, SUPPORTED BY NMME MODEL FORECASTS FOR THE ATLANTIC COAST. PROBABILITIES OF BELOW NORMAL PRECIPITATION ARE ENHANCED FOR COASTAL AREAS OF THE PACIFIC NORTHWEST, AS INDICATED BY RECENT DYNAMICAL MODEL GUIDANCE. THE CHANCES OF BELOW NORMAL PRECIPITATION ARE SLIGHTLY ENHANCED FROM PARTS OF THE SOUTHERN PLAINS INTO THE WESTERN MISSISSIPPI VALLEY FROM LOUISIANA TO MISSOURI, SUPPORTED BY ONGOING DRY SOIL MOISTURE CONDITIONS, AS WELL AS SOME MODELS OF THE NMME, INCLUDING THE CFS. IT SHOULD BE NOTED THAT PRECIPITATION FORECASTS FOR THE CONUS IN SUMMER HAVE LOW SKILL, THEREFORE PROBABILITIES ARE WEAK OVER MOST OF THE FORECAST DOMAIN. 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. THE NEXT MONTHLY OUTLOOK...FOR SEP ... WILL BE ISSUED ON THU AUG 16 2018 THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1981-2010 BASE PERIOD. $$