807  
FXUS06 KWBC 012015  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST FRI DECEMBER 01 2017  
 
6-10 DAY OUTLOOK FOR DEC 07 - 11 2017  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED BROAD  
SCALE 500-HPA CIRCULATION PATTERN WITH A HIGH AMPLITUDE RIDGE ESTABLISHED ALONG  
THE WEST COAST AND AN AMPLIFYING TROUGH OVER EAST-CENTRAL NORTH AMERICA. ABOVE  
NORMAL 500-HPA HEIGHTS ARE PREDICTED OVER ALASKA AND THE WESTERN HALF OF THE  
CONUS. BELOW NORMAL 500-HPA HEIGHTS ARE FORECAST FOR MOST PARTS OF THE  
REMAINDER OF THE CONUS. THE GREATEST WEIGHT FOR THE BLENDED HEIGHT FORECAST WAS  
GIVEN TO TODAY'S 00Z ECMWF ENSEMBLE MEAN, BASED ON CONSIDERATION OF RECENT  
SKILL.  
 
BELOW NORMAL TEMPERATURES ARE FAVORED FOR THE NORTHERN PARTS OF THE NORTHERN  
INTERMOUNTAIN WEST, DUE TO ANOMALOUS NORTHERLY FLOW AHEAD OF A PREDICTED STRONG  
RIDGE OVER THE ALASKA PANHANDLE AREA. BELOW NORMAL TEMPERATURES ARE LIKELY FOR  
MUCH OF THE EASTERN HALF OF THE CONUS, UNDERNEATH A PREDICTED STRONG ANOMALOUS  
TROUGH THERE. FORECAST ABOVE NORMAL HEIGHTS OVER THE WESTERN HALF OF THE CONUS  
AND SOUTHEASTERLY SURFACE FLOW OVER THE SOUTHWEST AND SOUTHERN CALIFORNIA LEAD  
TO INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES THERE. THE PREDICTED  
ANOMALOUS TROUGH OVER THE SOUTHERN ALEUTIANS AND THE NORTH PACIFIC ENHANCES  
CHANCES OF ABOVE NORMAL TEMPERATURES FOR MAINLAND ALASKA AND THE ALASKA  
PANHANDLE.  
 
ABOVE NORMAL PRECIPITATION IS FAVORED FOR THE FLORIDA PENINSULA, PARTS OF THE  
UPPER MISSISSIPPI VALLEY, THE WESTERN GREAT LAKES AND NORTHERN PARTS OF THE  
NORTHEAST, DUE TO FRONTAL ACTIVITY. BELOW NORMAL PRECIPITATION IS MOST LIKELY  
FOR MOST OF THE CONUS, WITH HIGH PROBABILITIES OF BELOW NORMAL PRECIPITATION  
ACROSS NORTHERN CALIFORNIA, THE PACIFIC NORTHWEST, THE MIDDLE AND LOWER  
MISSISSIPPI VALLEYS, SUPPORTED BY THE STRONG ANOMALOUS RIDGE FORECAST ALONG THE  
WEST COAST AND VARIOUS PRECIPITATION TOOLS. AN UPPER-LEVEL TROUGH PREDICTED  
OVER THE ALEUTIANS AND SOUTHWESTERLY FLOW AT THE SURFACE INCREASE CHANCES OF  
ABOVE NORMAL PRECIPITATION OVER MUCH OF ALASKA.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 20% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 10% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8, 40% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF TODAY'S OPERATIONAL  
0Z ECMWF CENTERED ON DAY 8, AND 10% 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 AGREEMENT AMONG THE PREDICTION TOOLS, OFFSET BY MODERATE TO HIGH SPREAD  
AMONG THE COMPONENT ENSEMBLE MEMBERS.  
 
8-14 DAY OUTLOOK FOR DEC 09 - 15 2017  
 
DURING THE WEEK-2 PERIOD, THE FORECAST CIRCULATION PATTERN IS VERY SIMILAR TO  
THE FORECAST FOR THE 6-10 DAY PERIOD. THE GFS ENSEMBLE MEMBERS CONTINUE TO  
INDICATE THAT THE ARCTIC OSCILLATION (AO) INDEX WILL BECOME MORE NEGATIVE WITH  
TIME AS FORECAST POSITIVE 500-HPA HEIGHT ANOMALIES ARE PROMINENT OVER THE  
HIGHER LATITUDES OF THE NORTHERN HEMISPHERE DURING EARLY DECEMBER.  
 
THE TEMPERATURE OUTLOOK DURING WEEK-2 IS BASED ON TELECONNECTIONS UPON THIS  
LARGE 500-HPA HEIGHT ANOMALY CENTER CENTERED OVER THE ALASKA PANHANDLE, ALONG  
WITH GUIDANCE FROM THE DYNAMICAL AND STATISTICAL TOOLS. BELOW NORMAL  
TEMPERATURES ARE FAVORED FOR MUCH OF THE CENTRAL AND EASTERN CONUS. THE HIGHEST  
PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE FORECAST ACROSS THE OHIO VALLEY  
WHERE STATISTICAL TOOLS HAVE A STRONG SIGNAL. TEMPERATURE FORECAST TOOLS VARY  
ACROSS THE WESTERN U.S., BUT IN GENERAL A WARMING TREND IS EXPECTED UNDERNEATH  
FORECAST ABOVE NORMAL HEIGHTS OVER THE REGION. FORECAST SOUTHEASTERLY FLOW  
CONTINUES TO FAVOR ABOVE NORMAL TEMPERATURES ACROSS CALIFORNIA AND THE  
SOUTHWEST.  
 
ABOVE NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE NORTHERN PLAINS, THE  
WESTERN GREAT LAKES AND THE NORTHERN NORTHEAST, DUE TO FRONTAL ACTIVITY. BELOW  
NORMAL PRECIPITATION IS MOST LIKELY FOR MOST OF THE CONUS, WITH HIGH  
PROBABILITIES OF BELOW NORMAL PRECIPITATION ACROSS NORTHERN CALIFORNIA AND THE  
CENTRAL GREAT BASIN, BASED ON THE HIGH AMPLITUDE RIDGE ALOFT AND STRONG SUPPORT  
FROM STATISTICAL AND DYNAMICAL PRECIPITATION TOOLS. THE LONGWAVE PATTERN ALOFT  
AND THE SURFACE FLOW ARE EXPECTED TO CHANGE LITTLE FOR ALASKA DURING WEEK-2.  
THEREFORE, ENHANCED ODDS FOR ABOVE NORMAL TEMPERATURES AND PRECIPITATION ARE  
LIKELY TO CONTINUE THROUGH WEEK-2 OVER MUCH OF ALASKA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 10% OF TODAY'S 6Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 10% OF TODAY'S GFS SUPERENSEMBLE MEAN  
CENTERED ON DAY 11, 10% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 11, 50%  
OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 20% OF TODAY'S 0Z  
CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE  
TO GOOD AGREEMENT AMONG THE ENSEMBLE MEANS.  
 
FORECASTER: Y. FAN  
 
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:  
19621124 - 19511128 - 19981122 - 19861127 - 19971215  
 
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:  
19621123 - 19511127 - 19861126 - 19631125 - 19901206  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 07 - 11 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N B OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA A B E MONTANA A B WYOMING A B  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA A N S DAKOTA A B  
NEBRASKA A B KANSAS N B OKLAHOMA B B  
N TEXAS B B S TEXAS B B W TEXAS B B  
MINNESOTA B B IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN B B  
ILLINOIS B B MISSISSIPPI B B MICHIGAN B A  
INDIANA B B OHIO B B KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK B N  
VERMONT N N NEW HAMP N N MAINE A N  
MASS N N CONN B N RHODE IS B N  
PENN B B NEW JERSEY B B W VIRGINIA B B  
MARYLAND B B DELAWARE B B VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B B FL PENIN B A AK N SLOPE A A  
AK ALEUTIAN A N 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 DEC 09 - 15 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A B OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA A B E MONTANA A A WYOMING A N  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA B A S DAKOTA A A  
NEBRASKA A N KANSAS A B OKLAHOMA B B  
N TEXAS B B S TEXAS B B W TEXAS A B  
MINNESOTA B A IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN B N  
ILLINOIS B B MISSISSIPPI B B MICHIGAN B A  
INDIANA B B OHIO B B KENTUCKY B B  
TENNESSEE B B ALABAMA B B 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 B NEW JERSEY B B W VIRGINIA B B  
MARYLAND B B DELAWARE B B VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B N FL PENIN B N AK N SLOPE A A  
AK ALEUTIAN A N 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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