957  
FXUS06 KWBC 262001  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST TUE DECEMBER 26 2017  
 
6-10 DAY OUTLOOK FOR JAN 01 - 05 2018  
 
TODAY'S ENSEMBLE MEAN FORECASTS ARE IN FAIR AGREEMENT ON A PREDICTED AMPLIFIED  
500-HPA CIRCULATION PATTERN FOR THE 6-10 DAY PERIOD OVER THE FORECAST DOMAIN.  
TROUGHS ARE ANTICIPATED OVER THE EASTERN CONUS, AND THE BERING SEA, WHILE A  
RIDGE IS EXPECTED OVER THE PACIFIC NORTHWEST EXTENDING NORTH/NORTHWESTWARD TO  
ALASKA. COMPARED TO THE ECMWF AND CANADIAN ENSEMBLE MEANS, RECENT GFS ENSEMBLE  
MEANS ARE LESS PROGRESSIVE AND MORE AMPLIFIED WITH THE EASTERN TROUGH, AND  
INDICATE A TROUGH APPROACHING CALIFORNIA FROM THE EAST PACIFIC. THESE MODEL  
DIFFERENCES SUGGEST THAT A PATTERN CHANGE IS LIKELY DURING THE PERIOD. THE  
ENSEMBLE SPAGHETTI CHARTS ALSO POINT TO A POSSIBLE PATTERN CHANGE AS LARGE  
ENSEMBLE SPREAD IS INDICATED OVER THE WESTERN CONUS AND EASTERN PACIFIC, WHILE  
MEMBER SPREAD BECOMES MODERATE OVER THE EASTERN CONUS. ACCORDING TO THE GFS,  
THE PNA INDEX WHICH RECENTLY HAS BEEN VERY WEAKLY POSITIVE IS FORECAST TO BE  
POSITIVE AT DAY 7 AND DAY 10, AND BE CLOSE TO ZERO BY DAY 14. THE AO INDEX  
WHICH HAS RECENTLY BEEN POSITIVE IS EXPECTED TO BE WEAKLY NEGATIVE AT DAY 7, BE  
CLOSE TO ZERO AT DAY 10, AND REMAIN CLOSE TO ZERO AT DAY 14. THERE IS  
RELATIVELY LARGE SPREAD OF THE FORECAST AO INDEX AMONG GFS ENSEMBLE MEMBERS.  
TODAY'S 500-HPA BLEND CHART DEPICTS BELOW NORMAL HEIGHTS FOR THE EASTERN  
TWO-THIRDS OF THE CONUS, THE ALEUTIANS, AND WESTERN MAINLAND ALASKA, WHILE  
ABOVE NORMAL HEIGHTS ARE ANTICIPATED FOR THE WESTERN THIRD OF THE CONUS, THE  
ALASKA PANHANDLE, AND EASTERN MAINLAND ALASKA.  
 
BELOW NORMAL HEIGHTS AND/OR ANOMALOUS NORTHERLY FLOW TILT THE ODDS TO NEAR TO  
BELOW NORMAL TEMPERATURES FOR MUCH OF THE THE EASTERN TWO-THIRDS OF THE CONUS,  
WHILE ABOVE NORMAL HEIGHTS FAVOR NEAR TO ABOVE NORMAL TEMPERATURES FOR THE  
WESTERN THIRD OF THE NATION. DUE TO THE EXPECTATION OF AN AMPLIFIED CIRCULATION  
PATTERN, THERE ARE HIGH PROBABILITIES FOR BELOW NORMAL TEMPERATURES FOR THE  
NORTHEASTERN PART OF THE NATION. ABOVE NORMAL HEIGHTS AND/OR ANOMALOUS  
SOUTHERLY FLOW ENHANCE PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR MOST OF  
ALASKA.  
 
ABOVE NORMAL HEIGHTS AND/OR ANOMALOUS NORTHERLY FLOW FAVOR NEAR TO BELOW NORMAL  
PRECIPITATION FOR MUCH OF THE CONUS. THE EXCEPTIONS ARE ACROSS THE SOUTHERN  
TIER OF THE CONUS FROM TEXAS TO FLORIDA WHERE MOISTURE RETURN NEAR A FRONTAL  
SYSTEM ENHANCE PROBABILITIES FOR ABOVE NORMAL PRECIPITATION, AND OVER PARTS OF  
THE NORTHWEST AS JET ENERGY APPROACHES FROM THE EAST PACIFIC. THE TROUGH  
FORECAST OVER THE BERING SEA TILTS THE ODDS TO ABOVE NORMAL PRECIPITATION FOR  
THE ALEUTIANS, ALASKA PANHANDLE, AND WESTERN AND SOUTHERN MAINLAND ALASKA.  
ABOVE NORMAL HEIGHTS FAVOR BELOW NORMAL PRECIPITATION FOR PARTS OF NORTHEASTERN  
MAINLAND ALASKA.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 20% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8, 10% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, 30% OF YESTERDAY'S 12Z  
EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 7, 5% OF TODAY'S 0Z CANADIAN ENSEMBLE  
MEAN CENTERED ON DAY 8, AND 15% 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 MODEL AGREEMENT ON AN AMPLIFIED CIRCULATION PATTERN, PARTIALLY OFFSET BY  
WEAK PRECIPITATION ANOMALY SIGNALS.  
 
8-14 DAY OUTLOOK FOR JAN 03 - 09 2018  
 
DURING WEEK-2, ENSEMBLE MODEL FORECASTS PREDICT A SOMEWHAT LESS AMPLIFIED AND  
PROGRESSIVE 500-HPA CIRCULATION PATTERN RELATIVE TO THE 6-10 DAY PERIOD. THE  
GFS-BASED ENSEMBLE MEANS CONTINUE TO BE THE SLOWEST TO INDICATE THESE PATTERN  
CHANGES. ENSEMBLE SPREAD IS MODERATE OVER MOST OF THE CENTRAL AND EASTERN  
CONUS, AND IS RELATIVELY LARGE OVER THE WESTERN CONUS AND EASTERN PACIFIC. THE  
EXPECTED 500-HPA HEIGHT ANOMALY PATTERN FOR WEEK-2 IS OF VERY LOW AMPLITUDE  
WHICH IS NOT SURPRISING GIVEN THE TIMING DIFFERENCES APPARENT IN THE VARIOUS  
ENSEMBLE MEAN SOLUTIONS AND THE ANTICIPATION THAT THE OVERALL CIRCULATION  
PATTERN WILL UNDERGO A DEAMPLIFICATION DURING THE PERIOD. 500-HPA HEIGHT  
ANOMALIES ARE FORECAST TO BE BELOW 30 METERS ACROSS THE ENTIRE CONUS, WITH WEAK  
NEGATIVE HEIGHT ANOMALIES FORECAST FOR THE WESTERN CONUS AND PARTS OF THE EAST,  
AND WEAK POSITIVE ANOMALIES NEAR THE GREAT LAKES AND THE SOUTHEAST. NEGATIVE  
ANOMALIES ARE ANTICIPATED FOR MUCH OF ALASKA WHILE HEIGHTS ARE PREDICTED TO BE  
ABOVE NORMAL FOR THE ALASKA PANHANDLE.  
 
NEAR TO BELOW NORMAL TEMPERATURES REMAIN LIKELY FOR MUCH OF THE CENTRAL AND  
EASTERN CONUS DUE TO WEAKLY BELOW NORMAL HEIGHTS AND THE EXPECTATION THAT EARLY  
IN THE PERIOD TEMPERATURES WILL BE SIGNIFICANTLY BELOW NORMAL FOR THE  
NORTHEAST. NEAR NORMAL HEIGHTS AND THE EXPECTATION OF AIR MASSES OF PACIFIC  
ORIGIN ENHANCE PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR MOST OF THE  
WESTERN THIRD OF THE CONUS AND MUCH OF ALASKA.  
 
THE BROAD TROUGH OVER THE EAST/CENTRAL CONUS AND THE EXPECTATION OF A STALLED  
FRONTAL SYSTEM OVER THE SOUTHERN CONUS ENHANCE PROBABILITIES FOR ABOVE NORMAL  
PRECIPITATION FOR THE GULF COAST REGION AND PARTS OF THE SOUTHEAST. WEAK  
SURFACE LOW PRESSURE AND THE LIKELIHOOD OF UPSLOPE FLOW FAVORS ABOVE NORMAL  
PRECIPITATION FOR PARTS OF THE ROCKIES. SURFACE HIGH PRESSURE OVER THE EASTERN  
PACIFIC TILT THE ODDS TO BELOW NORMAL PRECIPITATION FOR MUCH OF CALIFORNIA.  
ELSEWHERE OVER THE CONUS, POOR AGREEMENT AMONG THE PRECIPITATION TOOLS LEADS TO  
A FORECAST OF NEAR NORMAL PRECIPITATION. THE TROUGH FORECAST OVER THE BERING  
SEA FAVORS ABOVE NORMAL PRECIPITATION FOR MUCH OF WESTERN AND CENTRAL MAINLAND  
ALASKA, THE ALASKA PANHANDLE, AND THE ALEUTIANS.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 10% 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 GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11, 15% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, 25% OF YESTERDAY'S 12Z  
EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10, 5% OF TODAY'S 0Z CANADIAN ENSEMBLE  
MEAN CENTERED ON DAY 11, AND 10% OF YESTERDAY'S 12Z CANADIAN ENSEMBLE MEAN  
CENTERED ON DAY 10  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO  
TIMING DIFFERENCES AMONG THE FORECAST MODELS AND THE EXPECTATION OF A  
DEAMPLIFYING CIRCULATION PATTERN.  
 
FORECASTER: RANDY S  
 
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:  
19581206 - 19790104 - 19880103 - 19831217 - 19790109  
 
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:  
19581205 - 19831220 - 19790108 - 19790103 - 19880105  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 01 - 05 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A A OREGON A N NRN CALIF A N  
SRN CALIF A N IDAHO A N NEVADA A N  
W MONTANA N N E MONTANA B N WYOMING N N  
UTAH A N ARIZONA A N COLORADO N N  
NEW MEXICO A N N DAKOTA B B S DAKOTA B B  
NEBRASKA B B KANSAS B B OKLAHOMA B N  
N TEXAS B N S TEXAS B A W TEXAS B N  
MINNESOTA B B IOWA B B MISSOURI B B  
ARKANSAS B N LOUISIANA B A WISCONSIN B B  
ILLINOIS B B MISSISSIPPI B N MICHIGAN B B  
INDIANA B B OHIO B B KENTUCKY B B  
TENNESSEE B B ALABAMA B N NEW YORK B B  
VERMONT B B NEW HAMP B N MAINE B B  
MASS B N CONN B N RHODE IS B N  
PENN B B NEW JERSEY B N W VIRGINIA B B  
MARYLAND B B DELAWARE B N VIRGINIA B B  
N CAROLINA B N S CAROLINA B N GEORGIA B A  
FL PNHDL B A FL PENIN B A AK N SLOPE A B  
AK ALEUTIAN A A AK WESTERN A A AK INT BSN A B  
AK S INT A N AK SO COAST A A AK PNHDL A A  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 03 - 09 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A N OREGON A N NRN CALIF A B  
SRN CALIF A B IDAHO A N NEVADA A N  
W MONTANA A N E MONTANA A N WYOMING A A  
UTAH A N ARIZONA A N COLORADO A A  
NEW MEXICO A A N DAKOTA A N S DAKOTA N N  
NEBRASKA N A KANSAS N A OKLAHOMA N A  
N TEXAS B A S TEXAS N A W TEXAS N A  
MINNESOTA N N IOWA N N MISSOURI B A  
ARKANSAS B A LOUISIANA B A WISCONSIN B N  
ILLINOIS B N MISSISSIPPI B A MICHIGAN B N  
INDIANA B N OHIO B N KENTUCKY B A  
TENNESSEE B A ALABAMA B A NEW YORK B N  
VERMONT B N NEW HAMP B N MAINE B N  
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 B A S CAROLINA B A GEORGIA B A  
FL PNHDL N A FL PENIN N N AK N SLOPE A N  
AK ALEUTIAN A A AK WESTERN A A AK INT BSN A N  
AK S INT A A AK SO COAST A A AK PNHDL A A  
 
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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