218  
FXUS06 KWBC 012045  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST MON JANUARY 01 2018  
 
6-10 DAY OUTLOOK FOR JAN 07 - 11 2018  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE 500-HPA PATTERN  
FORECAST OVER THE DOMAIN. AN AMPLIFIED RIDGE IS FORECAST OVER ALASKA,  
ASSOCIATED WITH SIGNIFICANTLY POSITIVE HEIGHT ANOMALIES. THIS RIDGE IS FORECAST  
TO EXTEND SOUTH TO NEAR THE PACIFIC NORTHWEST. AN ANOMALOUS TROUGH IS PREDICTED  
OFF THE WEST COAST OF THE CONUS. A LARGE LONGWAVE TROUGH IS FORECAST OVER MUCH  
OF THE EASTERN TWO THIRDS OF THE CONUS. HOWEVER THERE'S A GOOD DEAL OF  
UNCERTAINTY REGARDING HOW DEEP THIS TROUGH WILL BE. OVER THE PAST COUPLE OF  
DAYS THE ENSEMBLE MEAN SOLUTIONS HAVE TRENDED TOWARDS BUILDING POSITIVE HEIGHT  
ANOMALIES IN THE EASTERN U.S., WHILE TODAY'S DETERMINISTIC GFS AND ECMWF RUNS  
PREDICT A DEEP TROUGH AND LARGE NEGATIVE HEIGHT ANOMALIES IN THE EASTERN U.S.  
DURING THE 6-10 DAY PERIOD. A COMPROMISE WAS CHOSEN BETWEEN THESE TWO POTENTIAL  
SOLUTIONS FOR TODAY'S MANUAL 500-HPA HEIGHT BLEND, THOUGH THE 0Z ECMWF ENSEMBLE  
MEAN SOLUTION, FORECASTING POSITIVE HEIGHT ANOMALIES IN THE EASTERN U.S., WAS  
SLIGHTLY FAVORED BECAUSE OF ITS HIGHER 500-HPA ANOMALY CORRELATIONS IN THE PAST  
60 DAYS. THE BLEND CONSISTS OF LARGE POSITIVE HEIGHT ANOMALIES FORECAST OVER  
ALASKA, NEAR-ZERO TO SLIGHTLY NEGATIVE HEIGHT ANOMALIES FOR MOST OF THE EASTERN  
HALF OF THE CONUS AND PARTS OF THE WEST COAST, AND NEAR-ZERO TO SLIGHTLY  
POSITIVE HEIGHT ANOMALIES ELSEWHERE.  
 
LARGE POSITIVE HEIGHT ANOMALIES OVER ALASKA STRONGLY FAVOR ABOVE NORMAL  
TEMPERATURES FOR ALASKA, EXCEPT FOR PARTS OF SOUTHEAST MAINLAND ALASKA AND THE  
PANHANDLE, WHERE A SHORTWAVE TROUGH IS PREDICTED TO FAVOR NEAR TO BELOW NORMAL  
TEMPERATURES. A RIDGE FORECAST IN THE WESTERN CONUS INCREASES THE LIKELIHOOD OF  
ABOVE NORMAL TEMPERATURES FOR PARTS OF THE WESTERN CONUS, THE SOUTHWEST, AND  
THE SOUTHERN PLAINS. COLD AIR, SLIDING SOUTH FROM CANADA INTO THE TROUGH  
PREDICTED IN THE EASTERN HALF OF THE U.S., ENHANCES THE CHANCES FOR BELOW  
NORMAL TEMPERATURES FOR NORTHERN PORTIONS OF THE PACIFIC NORTHWEST, THE  
NORTHERN PLAINS, AND INTO MOST OF THE EASTERN U.S.  
 
A STORM SYSTEM FORECAST TO COME ONSHORE IN ALASKA NEAR THE END OF THE 6-10 DAY  
PERIOD FAVORS ABOVE NORMAL PRECIPITATION FOR MUCH OF ALASKA, DUE TO THE FACT  
THAT ALASKA IS RELATIVELY DRY THIS TIME OF THE YEAR. THE EXCEPTION IS IN  
PORTIONS OF SOUTHEAST MAINLAND ALASKA AND THE PANHANDLE, WHERE CONDITIONS ARE  
EXPECTED TO REMAIN DRIER THAN NORMAL. STORM SYSTEM ACTIVITY, ASSOCIATED WITH AN  
ANOMALOUS TROUGH FORECAST OFF THE WEST COAST, IS EXPECTED TO COME ONSHORE  
DURING THE FORECAST PERIOD, HIGHLY FAVORING ABOVE NORMAL PRECIPITATION FOR MUCH  
OF THE WESTERN CONUS. THE TROUGH IN THE EASTERN U.S. FAVORS ABOVE NORMAL  
PRECIPITATION FOR THE MAJORITY OF THE EASTERN U.S.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 40% OF TODAY'S  
OPERATIONAL 6Z GFS CENTERED ON DAY 8, AND 60% OF TODAY'S 0Z EUROPEAN ENSEMBLE  
MEAN CENTERED ON DAY 8  
 
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
GOOD MODEL AGREEMENT AND AGREEMENT AMONG THE TOOLS, OFFSET BY SOME UNCERTAINTY  
IN THE STRENGTH OF THE EASTERN TROUGH.  
 
8-14 DAY OUTLOOK FOR JAN 09 - 15 2018  
 
BY THE WEEK-2 PERIOD, MODELS ARE IN FAIRLY GOOD AGREEMENT THAT RIDGING WILL  
STRENGTHEN OVER ALASKA AND ALONG THE EAST COAST, WITH RELATIVELY SMALL HEIGHT  
ANOMALIES ELSEWHERE IN THE CONUS. THE TEMPERATURE PROBABILITY FORECAST DURING  
THE WEEK-2 PERIOD IS SIMILAR TO THE 6-10 DAY PERIOD, WITH A FEW EXCEPTIONS. A  
FEW MORE PREDICTED COLD FRONT PASSAGES THROUGH THE SOUTHERN PLAINS FAVORS BELOW  
NORMAL TEMPERATURES THERE DURING WEEK-2. WITH POSITIVE HEIGHT ANOMALIES  
FORECAST TO BUILD IN THE EASTERN CONUS, NEAR TO ABOVE NORMAL TEMPERATURES ARE  
FAVORED FOR THE EAST COAST. THE PRECIPITATION PROBABILITY FORECAST DURING  
WEEK-2 IS VERY SIMILAR TO THE 6-10 DAY PERIOD, EXCEPT BELOW NORMAL  
PRECIPITATION IS FAVORED TO BECOME A BIT MORE WIDESPREAD IN PARTS OF EASTERN  
ALASKA AS THE RIDGING IS EXPECTED TO INCREASE OVER ALASKA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 60% OF TODAY'S GFS  
SUPERENSEMBLE MEAN CENTERED ON DAY 11, AND 40% OF TODAY'S OPERATIONAL 6Z GFS  
CENTERED ON DAY 11  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
GOOD MODEL AGREEMENT AND AGREEMENT AMONG THE TOOLS, OFFSET BY SOME UNCERTAINTY  
IN THE STRENGTH OF THE EASTERN TROUGH.  
 
FORECASTER: MIKE C  
 
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  
JANUARY 18.  
 
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:  
19581212 - 19851227 - 19851217 - 19631217 - 19561230  
 
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:  
19851227 - 19631217 - 19581211 - 19931226 - 19851219  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 07 - 11 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N N OREGON A A NRN CALIF A A  
SRN CALIF A A IDAHO A A NEVADA A A  
W MONTANA B A E MONTANA B A WYOMING A A  
UTAH A A ARIZONA A A COLORADO A A  
NEW MEXICO A A N DAKOTA B A S DAKOTA B A  
NEBRASKA B A KANSAS N A OKLAHOMA A A  
N TEXAS A A S TEXAS A N W TEXAS A N  
MINNESOTA B A IOWA B A MISSOURI B A  
ARKANSAS N A LOUISIANA A A WISCONSIN B A  
ILLINOIS B A MISSISSIPPI N A MICHIGAN B A  
INDIANA B A OHIO B A KENTUCKY B A  
TENNESSEE B A ALABAMA N A NEW YORK B A  
VERMONT B A NEW HAMP B A MAINE B A  
MASS B A CONN B A RHODE IS B A  
PENN B A NEW JERSEY B A W VIRGINIA B A  
MARYLAND B A DELAWARE B A VIRGINIA B A  
N CAROLINA B A S CAROLINA B A GEORGIA B A  
FL PNHDL N N FL PENIN N N 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 N A AK PNHDL B B  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 09 - 15 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B N OREGON A A NRN CALIF A A  
SRN CALIF A A IDAHO A A NEVADA A A  
W MONTANA B A E MONTANA B A WYOMING B A  
UTAH A A ARIZONA A A COLORADO A A  
NEW MEXICO A A N DAKOTA B A S DAKOTA B A  
NEBRASKA B A KANSAS B A OKLAHOMA B A  
N TEXAS B A S TEXAS B A W TEXAS A A  
MINNESOTA B A IOWA B A MISSOURI B A  
ARKANSAS B A LOUISIANA N A WISCONSIN B A  
ILLINOIS B A MISSISSIPPI N A MICHIGAN B A  
INDIANA B A OHIO B A KENTUCKY B A  
TENNESSEE B A ALABAMA N A NEW YORK N A  
VERMONT N A NEW HAMP N A MAINE N A  
MASS N A CONN N A RHODE IS N A  
PENN B A NEW JERSEY N A W VIRGINIA B A  
MARYLAND N A DELAWARE N A VIRGINIA N A  
N CAROLINA N A S CAROLINA N A GEORGIA A A  
FL PNHDL A A FL PENIN A A AK N SLOPE A A  
AK ALEUTIAN A A AK WESTERN A A AK INT BSN A B  
AK S INT A A AK SO COAST A A 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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