622  
FXUS06 KWBC 142013  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST THU DECEMBER 14 2017  
 
6-10 DAY OUTLOOK FOR DEC 20 - 24 2017  
 
TODAY'S MODEL SOLUTIONS GENERALLY DEPICT MODERATELY TO HIGHLY AMPLIFIED 500-HPA  
FLOW OVER MUCH OF THE FORECAST DOMAIN AND A POTENTIAL PATTERN CHANGE DURING THE  
PERIOD. IN THE MEAN, BROAD CYCLONIC FLOW IS INDICATED FROM THE NORTHERN PLAINS  
TO NEW ENGLAND ASSOCIATED WITH A TROUGH CENTERED OVER EAST-CENTRAL CANADA.  
FARTHER TO THE SOUTH, A STRENGTHENING RIDGE IS FORECAST NEAR CUBA AND ABOVE  
NORMAL HEIGHTS ASSOCIATED WITH THIS RIDGE EXTEND NORTHWARD TO THE SOUTHEASTERN  
CONUS. A STRONG RIDGE IS FORECAST OVER THE EASTERN PACIFIC OFF THE WEST COAST  
OF THE CONUS EXTENDING NORTHWARD TO CENTRAL MAINLAND ALASKA. MODELS HAVE COME  
INTO BETTER AGREEMENT IN DEVELOPING A TROUGH OVER THE WESTERN CONUS DOWNSTREAM  
OF THIS RIDGE. THE OFFICIAL MANUAL 500-HPA HEIGHT BLEND IS BASED PRIMARILY ON  
THE ENSEMBLE MEANS FROM THE CANADIAN, ECMWF, AND GEFS ENSEMBLE SYSTEMS.  
 
THE RIDGE EXPECTED OVER MAINLAND ALASKA INCREASES PROBABILITIES FOR ABOVE  
NORMAL TEMPERATURES ACROSS MOST OF THE STATE (WITH THE EXCEPTION OF THE  
SOUTHERN PANHANDLE). CYCLONIC FLOW AND BELOW NORMAL HEIGHTS LEAD TO ENHANCED  
PROBABILITIES FOR BELOW NORMAL TEMPERATURES FOR MUCH OF THE NORTHEAST AND GREAT  
LAKES REGION. BELOW NORMAL TEMPERATURES ARE ALSO FAVORED FOR THE NORTHWESTERN  
CONUS AS A TROUGH DEEPENS ACROSS THE WESTERN U.S. TELECONNECTIONS FROM A  
POSITIVE HEIGHT ANOMALY CENTER WEST OF THE ALASKA PANHANDLE, AND A NEGATIVE  
HEIGHT ANOMALY CENTER NEAR HUDSON BAY SUPPORT COLDER THAN NORMAL TEMPERATURES  
ACROSS MUCH OF THESE REGIONS. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF  
THE SOUTHEASTERN CONUS CORRESPONDING TO RIDGING AND ABOVE NORMAL HEIGHTS.  
WEAKLY ENHANCED PROBABILITIES FOR NEAR OR ABOVE NORMAL TEMPERATURES ARE  
INDICATED FOR THE SOUTHWESTERN CONUS AS WELL AS PARTS OF THE CENTRAL AND  
SOUTHERN PLAINS TO REFLECT A POTENTIAL TRANSITION FROM ABOVE NORMAL  
TEMPERATURES EARLY IN THE PERIOD TO BELOW NORMAL TEMPERATURES LATER IN THE  
PERIOD.  
 
ABOVE NORMAL PRECIPITATION IS LIKELY ACROSS WESTERN AND CENTRAL ALASKA EAST OF  
A TROUGH EXPECTED OVER THE BERING SEA. DRIER THAN NORMAL CONDITIONS ARE FAVORED  
OVER MUCH OF THE WEST COAST OF THE CONUS AND MUCH OF THE ALASKA PANHANDLE IN  
ASSOCIATION WITH THE STRONG RIDGE OFFSHORE OF WESTERN NORTH AMERICA. TROUGH  
DEVELOPMENT OVER THE WESTERN CONUS LEADS TO ENHANCED PROBABILITIES FOR ABOVE  
NORMAL PRECIPITATION FOR THE WEST-CENTRAL CONUS. ABOVE NORMAL PRECIPITATION IS  
MOST LIKELY FOR PARTS OF THE NORTHERN HIGH PLAINS DUE TO THE POTENTIAL FOR  
UPSLOPE FLOW. DRIER THAN NORMAL CONDITIONS ARE LIKELY FOR THE FLORIDA PENINSULA  
IN ASSOCIATION WITH RIDGING OVER THE CARIBBEAN. THE POTENTIAL FOR MOIST FLOW  
AROUND THE WESTERN PERIPHERY OF THIS RIDGE LEADS TO ENHANCED PROBABILITIES FOR  
ABOVE NORMAL PRECIPITATION FROM THE SOUTHERN PLAINS NORTHEASTWARD TO MUCH OF  
THE EASTERN CONUS.  
 
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 6Z GFS CENTERED ON DAY 8, 20% 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, 25% 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: AVERAGE, 3 OUT OF 5, DUE TO FAIRLY  
GOOD MODEL AGREEMENT OFFSET BY A POTENTIAL PATTERN CHANGE DURING THE OUTLOOK  
PERIOD.  
 
8-14 DAY OUTLOOK FOR DEC 22 - 28 2017  
 
DURING THE WEEK TWO PERIOD, MODELS DEPICT AN AMPLIFIED PATTERN AS STRONG  
RIDGING CONTINUES OVER ALASKA AND OFF THE WEST COAST OF THE CONUS. DOWNSTREAM  
OF THIS RIDGE, TROUGHING AND BELOW NORMAL HEIGHTS ARE EXPECTED FROM  
EAST-CENTRAL CANADA TO THE SOUTHWESTERN CONUS, WHILE A RIDGE IS ANTICIPATED TO  
BUILD OVER THE SOUTHEASTERN CONUS. THE WEEK TWO MANUAL 500-HPA HEIGHT BLEND  
REPRESENTS A COMPROMISE OF THE GEFS, ECMWF, AND CANADIAN ENSEMBLE MEAN  
SOLUTIONS.  
 
ABOVE NORMAL TEMPERATURES ARE LIKELY FOR ALASKA DUE TO THE AMPLIFIED RIDGE OVER  
THE STATE. BELOW NORMAL TEMPERATURES ARE FAVORED DOWNSTREAM ACROSS MOST OF THE  
CENTRAL AND WESTERN CONUS AS A TROUGH DEEPENS OVER THESE REGIONS. RIDGING LEADS  
TO ENHANCED ABOVE NORMAL TEMPERATURE PROBABILITIES FOR THE SOUTHEASTERN CONUS  
NORTHWARD TO THE MID-ATLANTIC. BELOW NORMAL TEMPERATURES ARE FAVORED FOR PARTS  
OF THE GREAT LAKES AND NORTHEAST IN ASSOCIATION WITH THE TROUGH OVER  
EAST-CENTRAL CANADA.  
 
MOIST FLOW AHEAD OF A TROUGH OVER THE WESTERN ALEUTIANS FAVORS ABOVE NORMAL  
PRECIPITATION FOR WESTERN AND CENTRAL MAINLAND ALASKA AS WELL AS THE EASTERN  
ALEUTIANS. DRIER THAN NORMAL CONDITIONS ARE LIKELY FOR MUCH OF THE NORTHWESTERN  
CONUS AS WELL AS THE ALASKA PANHANDLE DUE TO THE RIDGE EXPECTED OFF THE COAST.  
ABOVE NORMAL PRECIPITATION IS FAVORED FOR MUCH OF THE REMAINDER OF THE CONUS  
UNDERNEATH CYCLONIC FLOW. ABOVE NORMAL PRECIPITATION PROBABILITIES ARE THE  
HIGHEST FOR PARTS OF THE SOUTHERN PLAINS EXTENDING TO THE LOWER MISSISSIPPI,  
TENNESSEE, AND OHIO VALLEYS NEAR THE WESTERN PERIPHERY OF THE RIDGE OVER THE  
SOUTHEASTERN CONUS. RIDGING AND ABOVE NORMAL HEIGHTS LEAD TO ENHANCED  
PROBABILITIES FOR BELOW NORMAL PRECIPITATION OVER PARTS OF THE FLORIDA  
PENINSULA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 35% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 20% 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  
PREDICTED PATTERN AMPLIFICATION.  
 
FORECASTER: SCOTT 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  
DECEMBER 21.  
 
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:  
19851219 - 19561128 - 20021128 - 19621211 - 19601221  
 
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:  
19561127 - 20021128 - 19851221 - 19621211 - 19601224  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 20 - 24 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON B B NRN CALIF B B  
SRN CALIF N N IDAHO B N NEVADA B N  
W MONTANA B A E MONTANA B A WYOMING B A  
UTAH B A ARIZONA A A COLORADO B A  
NEW MEXICO A A N DAKOTA B A S DAKOTA B A  
NEBRASKA N A KANSAS N A OKLAHOMA N A  
N TEXAS A A S TEXAS A A W TEXAS N A  
MINNESOTA B A IOWA N N MISSOURI N A  
ARKANSAS A A LOUISIANA A A WISCONSIN B N  
ILLINOIS N N MISSISSIPPI A A MICHIGAN B N  
INDIANA A A OHIO N A KENTUCKY A A  
TENNESSEE A A ALABAMA A A NEW YORK N N  
VERMONT B N NEW HAMP B N MAINE B N  
MASS B N CONN N N RHODE IS N N  
PENN N A NEW JERSEY N N W VIRGINIA A A  
MARYLAND A N DELAWARE A N VIRGINIA A A  
N CAROLINA A A S CAROLINA A A GEORGIA A N  
FL PNHDL A B FL PENIN A B AK N SLOPE A A  
AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A  
AK S INT A A AK SO COAST A A AK PNHDL N B  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 22 - 28 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON B B NRN CALIF B B  
SRN CALIF B N IDAHO B B NEVADA B B  
W MONTANA B A E MONTANA B A WYOMING B A  
UTAH B A ARIZONA B A COLORADO B A  
NEW MEXICO B A N DAKOTA B N S DAKOTA B A  
NEBRASKA B A KANSAS B A OKLAHOMA B A  
N TEXAS B A S TEXAS B A W TEXAS B A  
MINNESOTA B N IOWA B A MISSOURI B A  
ARKANSAS B A LOUISIANA N A WISCONSIN B N  
ILLINOIS B A MISSISSIPPI A A MICHIGAN B A  
INDIANA N A OHIO N A KENTUCKY N A  
TENNESSEE A A ALABAMA A A NEW YORK B A  
VERMONT B A NEW HAMP B A MAINE B A  
MASS N A CONN N A RHODE IS N A  
PENN N A NEW JERSEY A A W VIRGINIA A A  
MARYLAND A A DELAWARE A A VIRGINIA A A  
N CAROLINA A A S CAROLINA A A GEORGIA A A  
FL PNHDL A N FL PENIN A B AK N SLOPE A A  
AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A  
AK S INT A A AK SO COAST A A AK PNHDL A 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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