011  
FXUS06 KWBC 112010  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST MON DECEMBER 11 2017  
 
6-10 DAY OUTLOOK FOR DEC 17 - 21 2017  
 
TODAY'S MODEL SOLUTIONS GENERALLY DEPICT A LOW TO MODERATELY AMPLIFIED 500-HPA  
PATTERN OVER MUCH OF THE FORECAST DOMAIN REFLECTIVE OF A POTENTIAL PERIOD OF  
TRANSITION. IN THE MEAN, BROAD CYCLONIC FLOW IS INDICATED OVER THE EASTERN  
TWO-THIRDS OF THE CONUS ASSOCIATED WITH A TROUGH CENTERED OVER EASTERN CANADA.  
A WEAK RIDGE IS FORECAST OVER THE EASTERN PACIFIC OFF THE WEST COAST OF THE  
CONUS EXTENDING NORTHWARD TO CENTRAL MAINLAND ALASKA. FARTHER TO THE SOUTH,  
RIDGING IS FORECAST NEAR CUBA AND ABOVE NORMAL HEIGHTS ASSOCIATED WITH THIS  
RIDGE EXTEND NORTHWARD TO PARTS OF THE SOUTHEASTERN CONUS. ENSEMBLE SPREAD IS  
HIGH OVER THE WESTERN CONUS IN ASSOCIATION WITH POTENTIAL TROUGH DEVELOPMENT  
OVER THE INTERMOUNTAIN WEST NEAR THE END OF THE 6 TO 10 DAY PERIOD. THE  
OFFICIAL MANUAL 500-HPA HEIGHT BLEND IS BASED PRIMARILY ON THE ENSEMBLE MEANS  
FROM THE CANADIAN, GEFS, AND ECMWF ENSEMBLE SYSTEMS.  
 
ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE WESTERN AND CENTRAL CONUS  
(PARTICULARLY EARLY IN THE PERIOD) CORRESPONDING TO AN EXPECTED MEAN LOW  
AMPLITUDE FLOW PATTERN AND ABOVE NORMAL HEIGHTS. CYCLONIC FLOW AND BELOW NORMAL  
HEIGHTS LEAD TO ENHANCED PROBABILITIES FOR BELOW NORMAL TEMPERATURES FOR PARTS  
OF THE NORTHEAST. THE RIDGE EXPECTED OVER MAINLAND ALASKA INCREASES  
PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ACROSS MUCH OF CENTRAL AND WESTERN  
ALASKA.  
 
ABOVE NORMAL PRECIPITATION IS LIKELY ACROSS WESTERN AND CENTRAL ALASKA AHEAD OF  
A TROUGH EXPECTED OVER THE BERING SEA. DRIER THAN NORMAL CONDITIONS ARE FAVORED  
OVER THE SOUTHERN TWO-THIRDS OF THE CONUS FROM THE PLAINS WESTWARD UNDERNEATH  
ABOVE NORMAL HEIGHTS. CYCLONIC FLOW LEADS TO ENHANCED PROBABILITIES FOR ABOVE  
NORMAL PRECIPITATION ACROSS MUCH OF THE NORTHERN TIER OF THE CONUS. DRIER THAN  
NORMAL CONDITIONS ARE LIKELY FOR THE FLORIDA PENINSULA IN ASSOCIATION WITH MEAN  
SURFACE HIGH PRESSURE. THE POTENTIAL FOR MOIST RETURN FLOW AROUND THIS SURFACE  
HIGH LEADS TO ENHANCED PROBABILITIES FOR ABOVE NORMAL PRECIPITATION FOR PARTS  
OF THE SOUTHEASTERN CONUS. BELOW NORMAL PRECIPITATION IS FAVORED FOR PARTS OF  
THE MID-ATLANTIC STATES UNDERNEATH FAST WESTERLY FLOW.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 15% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN 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, 5% OF TODAY'S  
OPERATIONAL 0Z ECMWF CENTERED ON DAY 8, AND 30% OF TODAY'S 0Z CANADIAN ENSEMBLE  
MEAN CENTERED ON DAY 8  
 
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO FAIR  
MODEL AGREEMENT.  
 
8-14 DAY OUTLOOK FOR DEC 19 - 25 2017  
 
DURING THE WEEK TWO PERIOD, MODELS DEPICT A TRANSITION TO A MORE AMPLIFIED  
PATTERN AS A RIDGE STRENGTHENS OVER ALASKA AND OFF THE WEST COAST OF THE CONUS.  
DOWNSTREAM OF THIS RIDGE, A TROUGH IS EXPECTED TO AMPLIFY OVER EAST-CENTRAL  
NORTH AMERICA. THE AMPLIFICATION OF THE PATTERN IS EXPECTED TO RESULT IN RISING  
HEIGHTS OVER ALASKA AND FALLING HEIGHTS OVER MUCH OF THE CONUS (PARTICULARLY  
FOR PARTS OF THE NORTH-CENTRAL CONUS). MODELS DISAGREE ON HOW DEEP THE TROUGH  
OVER CENTRAL AND EASTERN NORTH AMERICA WILL BE AS THE GEFS MAINTAINS ABOVE  
NORMAL HEIGHTS ACROSS THE SOUTHEAST WHILE THE CANADIAN AND ECMWF ENSEMBLE MEANS  
LOWER HEIGHTS TO NEAR NORMAL THERE. THE WEEK TWO MANUAL 500-HPA HEIGHT BLEND  
REPRESENTS A COMPROMISE OF THE CANADIAN, ECMWF, AND GEFS ENSEMBLE MEAN  
SOLUTIONS.  
 
ABOVE NORMAL TEMPERATURES ARE LIKELY FOR ALASKA AS A RIDGE AMPLIFIES OVER THE  
STATE. NEAR TO BELOW NORMAL TEMPERATURES ARE FAVORED DOWNSTREAM ACROSS THE  
NORTHERN THIRD OF THE CONUS AS A TROUGH BUILDS OVER EAST-CENTRAL NORTH AMERICA.  
CATEGORICAL TEMPERATURE PROBABILITIES ACROSS THE NORTHERN CONUS WERE GENERALLY  
SHIFTED COLDER RELATIVE TO AUTOMATED GUIDANCE AS TELECONNECTIONS FROM THE RIDGE  
CENTERED NEAR THE ALASKA PANHANDLE AND THE TROUGH CENTERED OVER EAST-CENTRAL  
CANADA BOTH SUPPORT COLDER THAN NORMAL TEMPERATURES ACROSS MUCH OF THE NORTHERN  
CONUS. ELSEWHERE, ABOVE NORMAL TEMPERATURES ARE FAVORED ACROSS MUCH OF THE  
SOUTHERN CONUS UNDERNEATH NEAR TO ABOVE NORMAL HEIGHTS.  
 
MOIST FLOW AHEAD OF A TROUGH OVER THE BERING SEA FAVORS ABOVE NORMAL  
PRECIPITATION FOR WESTERN AND CENTRAL ALASKA. DRIER THAN NORMAL CONDITIONS ARE  
LIKELY FOR MUCH OF THE WESTERN CONUS DUE TO THE RIDGE EXPECTED OFF THE COAST.  
ABOVE NORMAL PRECIPITATION IS SLIGHTLY FAVORED FOR PARTS OF THE SOUTHERN  
PLAINS, GULF COAST, AND SOUTHEAST NEAR THE BASE OF THE TROUGH FORECAST OVER  
EAST-CENTRAL NORTH AMERICA. MEAN SURFACE HIGH PRESSURE LEADS TO FAVORED BELOW  
NORMAL PRECIPITATION PROBABILITIES FOR PARTS OF THE CENTRAL PLAINS AND MIDDLE  
MISSISSIPPI VALLEY. PRECIPITATION ESTIMATES FROM THE GEFS AND ECMWF ENSEMBLE  
MEMBERS SUPPORT ELEVATED CHANCES FOR NEAR TO ABOVE NORMAL PRECIPITATION ACROSS  
THE NORTHERN TIER OF THE CONUS EAST OF THE ROCKIES.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 20% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 15% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, 5% OF  
YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10, 35% 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: AVERAGE, 3 OUT OF 5, DUE TO  
PREDICTED PATTERN AMPLIFICATION OFFSET BY LARGE DISAGREEMENTS BETWEEN  
STATISTICAL AND DYNAMICAL MODEL GUIDANCE ON THE TEMPERATURE OUTLOOK ACROSS MUCH  
OF THE CONUS.  
 
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 - 19561127 - 20021128 - 19601222 - 19631201  
 
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:  
19601224 - 19851218 - 19621211 - 19561127 - 20021125  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 17 - 21 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A N OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA A A E MONTANA A A WYOMING A N  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA A A S DAKOTA A N  
NEBRASKA A B KANSAS A B OKLAHOMA A B  
N TEXAS A B S TEXAS A B W TEXAS A B  
MINNESOTA A A IOWA A B MISSOURI A B  
ARKANSAS A B LOUISIANA A N WISCONSIN A A  
ILLINOIS A B MISSISSIPPI A A MICHIGAN N A  
INDIANA A B OHIO N N KENTUCKY A B  
TENNESSEE A N ALABAMA A A NEW YORK N N  
VERMONT B N NEW HAMP B N MAINE B N  
MASS B B CONN N B RHODE IS N B  
PENN N N NEW JERSEY N B W VIRGINIA N B  
MARYLAND N B DELAWARE N B VIRGINIA N B  
N CAROLINA N B S CAROLINA A N GEORGIA A A  
FL PNHDL A N FL PENIN A B AK N SLOPE N N  
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 N N  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 19 - 25 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N B OREGON N B NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA N N E MONTANA N A WYOMING A A  
UTAH A B ARIZONA A B COLORADO A N  
NEW MEXICO A B N DAKOTA N A S DAKOTA N A  
NEBRASKA A B KANSAS A B OKLAHOMA A B  
N TEXAS A N S TEXAS A A W TEXAS A N  
MINNESOTA B A IOWA N B MISSOURI N B  
ARKANSAS A N LOUISIANA A A WISCONSIN B N  
ILLINOIS N B MISSISSIPPI A A MICHIGAN B A  
INDIANA B B OHIO B N KENTUCKY N N  
TENNESSEE N N ALABAMA A A NEW YORK B A  
VERMONT B A NEW HAMP B N MAINE B A  
MASS B N CONN B N RHODE IS B N  
PENN B N NEW JERSEY B N W VIRGINIA B N  
MARYLAND B N DELAWARE B N VIRGINIA B N  
N CAROLINA N N S CAROLINA N N GEORGIA A A  
FL PNHDL A N FL PENIN A 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 A A AK PNHDL A N  
 
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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