626  
FXUS06 KWBC 272001  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST WED DECEMBER 27 2017  
 
6-10 DAY OUTLOOK FOR JAN 02 - 06 2018  
 
TODAY'S ENSEMBLE MEAN FORECASTS ARE IN FAIRLY GOOD 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 THEIR SOLUTIONS FROM YESTERDAY, THE  
CANADIAN AND ECMWF ENSEMBLE MEANS FROM TODAY ARE LESS PROGRESSIVE WITH THE  
TROUGH FORECAST OVER THE EASTERN U.S. AND MORE CLOSELY RESEMBLE THE MORE  
CONSISTENT GFS ENSEMBLE MEAN SOLUTIONS. THE ENSEMBLE SPAGHETTI CHARTS INDICATE  
MODERATE TO LARGE SPREAD OVER THE EASTERN CONUS, AND LARGE SPREAD OVER THE  
WESTERN CONUS AND EASTERN PACIFIC. ACCORDING TO THE GFS, THE PNA INDEX WHICH  
RECENTLY HAS BEEN CLOSE TO ZERO 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 NEAR ZERO AT DAY 7, BE WEAKLY POSITIVE AT DAY 10, AND BE  
CLOSE TO ZERO AT DAY 14. THERE IS RELATIVELY LARGE SPREAD AMONG GFS ENSEMBLE  
MEMBERS FOR THE FORECAST AO INDEX AT DAY 10 AND BEYOND. TODAY'S 500-HPA BLEND  
CHART DEPICTS BELOW NORMAL HEIGHTS FOR THE EASTERN TWO-THIRDS OF THE CONUS AND  
THE ALEUTIANS, WHILE ABOVE NORMAL HEIGHTS ARE ANTICIPATED FOR THE WESTERN THIRD  
OF THE CONUS, THE ALASKA PANHANDLE, AND MAINLAND ALASKA.  
 
BELOW NORMAL HEIGHTS AND OR ANOMALOUS NORTHERLY FLOW FAVOR BELOW NORMAL  
TEMPERATURES FOR MUCH OF THE EASTERN TWO-THIRDS OF THE CONUS, AND PARTS OF THE  
NORTHERN ROCKIES AND EXTREME NORTHERN INTERMOUNTAIN WEST. ABOVE NORMAL HEIGHTS  
TILT THE ODDS TO ABOVE NORMAL TEMPERATURES FOR THE REMAINDER OF THE CONUS AND  
ALASKA.  
 
ABOVE NORMAL HEIGHTS (WESTERN CONUS) AND ANOMALOUS NORTHERLY FLOW (CENTRAL AND  
EASTERN CONUS) ENHANCE PROBABILITIES FOR NEAR TO BELOW NORMAL PRECIPITATION FOR  
MOST OF THE CONUS. THE EXCEPTION IS ALONG THE GULF COAST AND FLORIDA WHERE  
MOISTURE OVERRUNNING A FRONTAL SYSTEM FAVORS ABOVE NORMAL PRECIPITATION. THE  
TROUGH OVER THE BERING SEA TILTS THE ODDS TO NEAR TO ABOVE NORMAL PRECIPITATION  
FOR 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, 5% OF  
TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 8, 30% OF TODAY'S 0Z EUROPEAN  
ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED  
ON DAY 8, AND 15% OF TODAY'S 0Z CANADIAN 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 ON AN AMPLIFIED CIRCULATION PATTERN, PARTIALLY OFFSET BY  
WEAK PRECIPITATION ANOMALY SIGNALS.  
 
8-14 DAY OUTLOOK FOR JAN 04 - 10 2018  
 
DURING WEEK-2, ENSEMBLE MODEL FORECASTS PREDICT A SOMEWHAT LESS AMPLIFIED  
CIRCULATION PATTERN, RELATIVE TO THE 6-10 DAY PERIOD, AS HEIGHTS ARE EXPECTED  
TO RISE OVER THE EASTERN U.S. AND FALL OVER THE WEST. THE CANADIAN ENSEMBLE  
MEAN SOLUTIONS INDICATE LOWER HEIGHTS OVER THE NORTHEASTERN CONUS, COMPARED TO  
THE GFS AND ECMWF ENSEMBLE MEANS, SO THAT THE CANADIAN SOLUTIONS WERE NOT  
INCLUDED IN THE BLENDED 500-HPA HEIGHT FIELD. ENSEMBLE SPREAD IS RELATIVELY LOW  
OVER MOST OF THE CENTRAL AND EASTERN CONUS, AND MODERATE TO LARGE OVER THE  
WESTERN CONUS AND EASTERN PACIFIC. THE EXPECTED 500-HPA HEIGHT ANOMALY PATTERN  
FOR WEEK-2 IS OF LOW AMPLITUDE, WHICH IS NOT SURPRISING GIVEN THE ANTICIPATION  
THAT THE OVERALL CIRCULATION PATTERN WILL UNDERGO A DEAMPLIFICATION DURING THE  
PERIOD. 500-HPA HEIGHTS ARE FORECAST TO BE BELOW NORMAL OVER THE WESTERN HALF  
OF THE CONUS AND THE ALEUTIANS, AND ABOVE NORMAL OVER THE EASTERN HALF OF THE  
CONUS, MAINLAND ALASKA, AND THE ALASKA PANHANDLE.  
 
THE TEMPERATURE ANOMALY PATTERN EXPECTED FOR WEEK-2 IS QUITE SIMILAR TO THAT  
FORECAST FOR THE 6-10 DAY PERIOD. WITH HEIGHTS ANTICIPATED TO RISE OVER THE  
EASTERN U.S. DURING THE PERIOD, THE AREAL COVERAGE AND HIGH PROBABILITIES OF  
BELOW NORMAL TEMPERATURES ARE DECREASED FROM THAT DEPICTED FOR THE 6-10 DAY  
PERIOD.  
 
THE BROAD TROUGH FORECAST OVER THE CONUS TILTS THE ODDS TO NEAR TO ABOVE NORMAL  
PRECIPITATION FOR MUCH OF THE NATION. ANOMALOUS NORTHEASTERLY FLOW FAVORS BELOW  
NORMAL PRECIPITATION FOR PARTS OF THE NORTHWEST. THE TROUGH NEAR THE BERING SEA  
ENHANCES PROBABILITIES FOR ABOVE NORMAL PRECIPITATION FOR MOST OF ALASKA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 15% 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 GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11, 40% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 10% OF YESTERDAY'S  
12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO  
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:  
19790110 - 19581207 - 19910103 - 19831221 - 20040105  
 
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:  
19940103 - 19790109 - 19581206 - 19831225 - 19831220  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 02 - 06 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N B OREGON A B NRN CALIF A B  
SRN CALIF A N IDAHO N B NEVADA A B  
W MONTANA B N E MONTANA B N WYOMING N N  
UTAH A N ARIZONA A N COLORADO N N  
NEW MEXICO N N N DAKOTA B N S DAKOTA B B  
NEBRASKA B B KANSAS B B OKLAHOMA B B  
N TEXAS B B S TEXAS B N W TEXAS B N  
MINNESOTA B B IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B N WISCONSIN B B  
ILLINOIS B B MISSISSIPPI B B MICHIGAN B N  
INDIANA B B OHIO B B KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK B B  
VERMONT B B NEW HAMP B B MAINE B B  
MASS B N CONN B B RHODE IS B N  
PENN B B NEW JERSEY B B W VIRGINIA B B  
MARYLAND B B DELAWARE B N VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B A  
FL PNHDL B A FL PENIN B A 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 A  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 04 - 10 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N B OREGON A B NRN CALIF A B  
SRN CALIF A N IDAHO B N NEVADA A N  
W MONTANA B A E MONTANA B A WYOMING N A  
UTAH A A ARIZONA A A COLORADO A A  
NEW MEXICO A A N DAKOTA N A S DAKOTA N A  
NEBRASKA B A KANSAS B A OKLAHOMA B A  
N TEXAS B A S TEXAS B A W TEXAS N A  
MINNESOTA N N IOWA B A MISSOURI B A  
ARKANSAS B A LOUISIANA B A WISCONSIN B N  
ILLINOIS B A MISSISSIPPI B A MICHIGAN B A  
INDIANA B A OHIO B A KENTUCKY B A  
TENNESSEE B A ALABAMA B A NEW YORK B N  
VERMONT B N NEW HAMP B A MAINE B A  
MASS B A CONN B A RHODE IS B A  
PENN B A NEW JERSEY B N W VIRGINIA B A  
MARYLAND B N DELAWARE B N VIRGINIA B N  
N CAROLINA B N S CAROLINA B A GEORGIA B A  
FL PNHDL B A FL PENIN B A 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 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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