PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD 
300 PM EDT FRI APRIL 20 2018 
 
6-10 DAY OUTLOOK FOR APR 26 - 30 2018 
 
TODAY'S VARIOUS ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE 6-10 DAY  
PATTERN OVER THE FORECAST DOMAIN. TROUGHS ARE PREDICTED OVER THE ALEUTIANS,  
NEAR THE CALIFORNIA COAST, AND OVER THE EASTEARN CONUS, WHILE ANOMALOUS RIDGING  
IS FORECAST OVER THE WESTERN CONUS. TODAY'S MANUAL 500-HPA BLEND IS BASED  
PRIMARILY ON THE ENSEMBLE MEANS FROM THE CANADIAN, EUROPEAN, AND GEFS MODEL  
SUITES. ABOVE NORMAL 500-HPA HEIGHTS ARE FORECAST OVER MOST OF THE WESTERN AND  
CENTRAL CONUS, WHILE NEGATIVE HEIGHT ANOMALIES ARE FORECAST OVER MUCH OF ALASKA  
AND THE EASTERN CONUS.  
 
ABOVE NORMAL TEMPERATURES ARE FAVORED OVER MUCH OF THE WESTERN HALF OF THE  
CONUS, WHERE NEAR TO ABOVE NORMAL HEIGHTS ARE PREDICTED. TROUGHING NEAR THE  
EAST COAST LEADS TO INCREASED CHANCES FOR NEAR TO BELOW NORMAL TEMPERATURES  
ACROSS MUCH OF THE EASTERN CONUS EXCEPT FOR MAINE WHERE ABOVE NORMAL  
TEMPERATURES ARE INDICATED. BELOW NORMAL TEMPERATURES ARE FAVORED OVER PARTS OF  
SOUTHEASTERN MAINLAND ALASKA AND THE ALASKA PANHANDLE, WHILE ABOVE NORMAL  
TEMPERATURES ARE FAVORED OVER MUCH OF WESTERN AND NORTHERN ALASKA, CONSISTENT  
WITH REFORECAST-CALIBRATED GEFS AND ECMWF TOOLS.  
 
BELOW NORMAL PRECIPITATION IS FAVORED FOR MOST OF OF THE NORTHERN AND EASTERN  
CONUS, CONSISTENT WITH DYNAMICAL MODEL GUIDANCE FROM THE GEFS AND ECMWF  
ENSEMBLE MEAN SOLUTIONS. ABOVE NORMAL PRECIPITATION IS FAVORED FOR CALIFORNIA,  
ARIZONA, NEW MEXICO, AND WESTERN TEXAS IN ASSOCIATION WITH A MEAN 500-HPA  
TROUGH PREDICTED TO PROGRESS TOWARDS THE WEST COAST. A PREDICTED MEAN 500-HPA  
TROUGH OVER THE EASTERN COAST ENHANCES PROBABILITIES OF ABOVE NORMAL  
PRECIPITATION FOR PARTS OF THE NORTHEAST. SEVERAL PREDICTED STORM SYSTEMS IN  
THE GULF OF ALASKA INCREASE THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION FOR  
MUCH OF ALASKA.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 15% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 5% OF TODAY'S OPERATIONAL 0Z GFS CENTERED ON DAY 8, 25% OF TODAY'S 0Z  
EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, 5% OF YESTERDAY'S 12Z EUROPEAN  
ENSEMBLE MEAN CENTERED ON DAY 7, 10% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED  
ON DAY 8, 20% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 5% OF  
YESTERDAY'S 12Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 7  
  
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
GOOD AGREEMENT AMONG THE MODELS AND TOOLS. 
 
8-14 DAY OUTLOOK FOR APR 28 - MAY 04, 2018  
 
TODAY'S ENSEMBLE MEAN DYNAMICAL MODEL FORECASTS ARE IN GOOD AGREEMENT ON THE  
PREDICTED 500-HPA CIRCULATION PATTERN OVER NORTH AMERICA FOR THE WEEK-2 PERIOD.  
TROUGHS ARE FORECAST ALONG THE WEST COAST AND OVER THE NORTHEAST. ABOVE NORMAL  
500-HPA HEIGHTS ARE FORECAST OVER MOST OF THE CONUS EXCEPT FOR PARTS OF MAINE  
AND CALIFORNIA WHERE BELOW NORMAL 500-HPA HEIGHTS ARE INDICATED.  
 
ABOVE NORMAL 500-HPA HEIGHTS FAVOR NEAR TO ABOVE NORMAL TEMPERATURES OVER MUCH  
OF THE CONUS, EXCEPT FOR PARTS OF THE SOUTHEAST COAST AND THE NORTHEAST WHERE  
BELOW NORMAL TEMPERATURES ARE INDICATED. THE TEMPERATURE PROBABILITY FORECAST  
FOR ALASKA DURING THE WEEK-2 PERIOD IS GENERALLY SIMILAR TO THE 6-10 DAY PERIOD. 
 
NEAR TO BELOW NORMAL PRECIPITATION IS FORECAST FOR WASHINGTON AND THE EASTERN  
CONUS, CONSISTENT WITH DYNAMICAL MODEL GUIDANCE FROM THE ECMWF ENSEMBLE MEAN  
SOLUTION. ABOVE NORMAL PRECIPITATION IS FAVORED FOR MOST OF THE SOUTHWESTERN  
CONUS IN ASSOCIATION WITH A MEAN 500-HPA TROUGH PREDICTED ALONG THE WEST COAST.  
SEVERAL PREDICTED STORM SYSTEMS IN THE GULF OF ALASKA INCREASE THE LIKELIHOOD  
OF NEAR TO ABOVE NORMAL PRECIPITATION FOR MUCH OF ALASKA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 20% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 5% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 11, 30% OF TODAY'S  
0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, 5% OF YESTERDAY'S 12Z EUROPEAN  
ENSEMBLE MEAN CENTERED ON DAY 10, 20% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN  
CENTERED ON DAY 11, AND 5% OF YESTERDAY'S 12Z CANADIAN ENSEMBLE MEAN CENTERED  
ON DAY 10  
 
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
GOOD AGREEMENT AMONG THE MODELS AND TOOLS. 
 
FORECASTER: LUKE H 
 
NOTES: 
 
 
AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OCCASIONALLY MANUAL  
INTERVENTION IS NECESSARY TO ADDRESS QUALITY CONTROL AND CONSISTENCY ISSUES. IN  
THESE CASES, FORECASTS ARE MANUALLY DRAWN BUT A FULL DISCUSSION IS NOT ISSUED. 
 
 
THE NOTATION FOR THE CATEGORICAL FORECAST INDICATED ON THE MAPS IS THE SAME AS  
THAT IN THE TABLES: A-ABOVE   N-NEAR NORMAL   B-BELOW 
 
 
THE TEMPERATURE MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WARMER (ORANGE,  
"A"), COLDER (BLUE, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL AVERAGE  
VALUES FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "F").  LABELS ON THE  
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).  
 PROBABILITY OF N IS ALWAYS < 40%. 
 
 
THE PRECIPITATION MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WETTER (GREEN,  
"A"), DRIER (TAN, "B"), OR CLOSE TO (UNSHADED, "N"). HISTORICAL MEDIAN VALUES  
FOR THE CALENDAR PERIOD OF THE FORECAST (DASHES, "INCHES").  LABELS ON THE  
SHADED LINES GIVE THE PROBABILITY (> 33%) OF THE MORE LIKELY CATEGORY (B OR A).  
 PROBABILITY OF N IS ALWAYS < 40%. 
 
 
IN THE SOUTHWEST AND OTHER CLIMATOLOGICALLY DRY REGIONS - THERE WILL BE A  
GREATER THAN 33.3% CHANCE OF NO PRECIPITATION AND OCCASIONALLY EVEN A NORMAL  
(I.E. MEDIAN) VALUE OF ZERO - ESPECIALLY DURING THE DRY SEASONS.  IN SUCH CASES  
A FORECAST OF NEAR NORMAL IS EFFECTIVELY A FORECAST OF LITTLE OR NO  
PRECIPITATION. 
 
 
THE CLIMATE PREDICTION CENTER USES 1981-2010 BASE PERIOD MEANS FOR  
TEMPERATURE...PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN THE CLIMATE  
OUTLOOKS. 
 
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON MAY  
17. 
 
ANALOGS TO THE 5 DAY MEAN OBSERVED PATTERN CENTERED 3 DAYS AGO (D-3) 
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE 
INCLUDE THE 5 DAY PERIODS CENTERED ON THE FOLLOWING DATES:  
19990411 - 19750427 - 19790408 - 20090412 - 19910331 
 
 
ANALOGS TO THE 7 DAY MEAN OBSERVED PATTERN CENTERED 4 DAYS AGO (D-4) 
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE 
INCLUDE THE 7 DAY PERIODS CENTERED ON THE FOLLOWING DATES:  
19790409 - 19990411 - 20090412 - 19750427 - 20070501 
 
 
6-10 DAY OUTLOOK TABLE 
OUTLOOK FOR APR 26 - 30 2018 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    B     OREGON      A    N     NRN CALIF   A    A      
SRN CALIF   A    A     IDAHO       A    B     NEVADA      A    N      
W MONTANA   A    B     E MONTANA   A    B     WYOMING     A    B      
UTAH        A    N     ARIZONA     A    A     COLORADO    A    N      
NEW MEXICO  A    A     N DAKOTA    A    B     S DAKOTA    A    B      
NEBRASKA    A    B     KANSAS      A    N     OKLAHOMA    N    N      
N TEXAS     N    N     S TEXAS     B    B     W TEXAS     A    A      
MINNESOTA   N    B     IOWA        N    B     MISSOURI    B    B      
ARKANSAS    B    B     LOUISIANA   B    B     WISCONSIN   B    B      
ILLINOIS    B    B     MISSISSIPPI B    B     MICHIGAN    B    B      
INDIANA     B    B     OHIO        B    B     KENTUCKY    B    B      
TENNESSEE   B    B     ALABAMA     B    B     NEW YORK    N    N      
VERMONT     N    A     NEW HAMP    N    A     MAINE       A    A      
MASS        N    A     CONN        N    N     RHODE IS    N    A      
PENN        B    B     NEW JERSEY  N    N     W VIRGINIA  B    B      
MARYLAND    B    B     DELAWARE    B    N     VIRGINIA    B    B      
N CAROLINA  B    B     S CAROLINA  B    B     GEORGIA     B    B      
FL PNHDL    B    B     FL PENIN    B    B     AK N SLOPE  A    A      
AK ALEUTIAN A    A     AK WESTERN  A    A     AK INT BSN  N    A      
AK S INT    B    A     AK SO COAST B    A     AK PNHDL    B    N      
  
                            
 
8-14 DAY OUTLOOK TABLE 
OUTLOOK FOR APR 28 - MAY 04, 2018 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    B     OREGON      A    N     NRN CALIF   A    A      
SRN CALIF   N    A     IDAHO       A    N     NEVADA      A    A      
W MONTANA   A    N     E MONTANA   A    N     WYOMING     A    N      
UTAH        A    A     ARIZONA     A    A     COLORADO    A    N      
NEW MEXICO  A    A     N DAKOTA    A    N     S DAKOTA    A    N      
NEBRASKA    A    N     KANSAS      A    N     OKLAHOMA    A    N      
N TEXAS     A    N     S TEXAS     N    N     W TEXAS     A    A      
MINNESOTA   A    N     IOWA        A    N     MISSOURI    A    N      
ARKANSAS    A    B     LOUISIANA   N    B     WISCONSIN   N    N      
ILLINOIS    A    N     MISSISSIPPI N    B     MICHIGAN    N    N      
INDIANA     A    N     OHIO        A    B     KENTUCKY    A    B      
TENNESSEE   N    B     ALABAMA     N    B     NEW YORK    B    B      
VERMONT     B    B     NEW HAMP    B    B     MAINE       B    B      
MASS        B    B     CONN        B    B     RHODE IS    B    B      
PENN        N    B     NEW JERSEY  N    B     W VIRGINIA  A    B      
MARYLAND    N    B     DELAWARE    N    B     VIRGINIA    N    B      
N CAROLINA  N    B     S CAROLINA  B    B     GEORGIA     N    B      
FL PNHDL    N    B     FL PENIN    N    B     AK N SLOPE  A    A      
AK ALEUTIAN A    N     AK WESTERN  A    A     AK INT BSN  N    A      
AK S INT    B    N     AK SO COAST B    N     AK PNHDL    B    B      
  
                           LEGEND 
TEMPS WITH RESPECT TO NORMAL     PCPN WITH RESPECT TO MEDIAN 
A - ABOVE   N  - NEAR NORMAL     A - ABOVE   N - NEAR MEDIAN 
B - BELOW                        B - BELOW 
  
THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL 
VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE 
AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE. 
  
FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS 
PMDMRD. 
 
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