331  
FXUS06 KWBC 292051  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST WED NOVEMBER 29 2017  
 
6-10 DAY OUTLOOK FOR DEC 05 - 09 2017  
 
THE ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED BROAD SCALE  
500-HPA CIRCULATION PATTERN WITH A HIGH AMPLITUDE RIDGE DEVELOPING ALONG THE  
WEST COAST AND AN AMPLIFYING TROUGH OVER EAST-CENTRAL NORTH AMERICA. 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 PARTS OF THE PACIFIC NORTHWEST  
AND THE NORTHERN INTERMOUNTAIN REGION, DUE TO ANOMALOUS NORTHERLY FLOW AHEAD OF  
A PREDICTED STRONG RIDGE OVER THE ALASKA PANHANDLE AREA. BELOW NORMAL  
TEMPERATURES ARE LIKELY FOR LARGE PARTS OF EASTERN TWO THIRD OF THE CONUS,  
UNDERNEATH A FORECAST STRONG ANOMALOUS TROUGH THERE. SOUTHEASTERLY FLOW LEADS  
TO INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES ACROSS SOUTHERN CALIFORNIA,  
WHILE SURFACE HIGH PRESSURE AND ASSOCIATED LOW-LEVEL INVERSIONS MAY SLOW ANY  
WARMING TREND ACROSS THE INTERIOR WEST. THE PREDICTED ANOMALOUS TROUGH OVER THE  
SOUTHERN ALEUTIANS AND THE NORTH PACIFIC ENHANCES CHANCE FOR ABOVE NORMAL  
TEMPERATURES FOR MAINLAND ALASKA AND THE ALASKA PANHANDLE.  
 
EARLY IN THE PERIOD, AN UPPER-LEVEL TROUGH ALONG WITH EXPECTED UPSLOPE FLOW  
ENHANCE ODDS FOR ABOVE NORMAL PRECIPITATION ACROSS THE SOUTHERN GREAT PLAINS.  
ABOVE NORMAL PRECIPITATION IS FAVORED FOR THE EASTERN CONUS ALONG AN EASTWARD  
ADVANCING COLD FRONT. VERY HIGH PROBABILITIES FOR BELOW NORMAL PRECIPITATION  
ACROSS NORTHERN CALIFORNIA AND THE PACIFIC NORTHWEST, AND BLOW NORMAL  
PRECIPITATION OVER THE MIDDLE MIDDLE MISSISSIPPI VALLEY, ARE SUPPORTED BY THE  
AMPLIFYING RIDGE ALONG THE WEST COAST AND VARIOUS PRECIPITATION TOOLS. AN  
UPPER-LEVEL TROUGH OVER THE ALEUTIANS AND SOUTHWESTERLY FLOW AT THE SURFACE  
INCREASE CHANCES FOR ABOVE NORMAL PRECIPITATION THROUGHOUT MUCH OF 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, 10% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8, 5% OF  
TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 8, 40% OF TODAY'S 0Z EUROPEAN  
ENSEMBLE MEAN CENTERED ON DAY 8, 5% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON  
DAY 8, AND 20% 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 07 - 13 2017  
 
DURING THE WEEK-2 PERIOD, THE FORECAST CIRCULATION PATTERN IS VERY SIMILAR TO  
THE FORECAST FOR THE 6-10 DAY PERIOD. DUE TO LOW SPREAD AMONG THE GFS AND ECMWF  
ENSEMBLE MEMBERS AND GOOD MODEL CONTINUITY, FORECAST CONFIDENCE REMAINS HIGH  
THAT THIS PATTERN BECOMES ESTABLISHED AND RESULTS IN MUCH COLDER TEMPERATURES  
FOR THE CENTRAL AND EASTERN U.S. DURING WEEK-2. THE GFS ENSEMBLE MEMBERS  
CONTINUE TO INDICATE THAT THE ARCTIC OSCILLATION (AO) INDEX BECOMES MORE  
NEGATIVE WITH TIME AS POSITIVE 500-HPA HEIGHT ANOMALIES ARE PROMINENT OVER THE  
HIGHER LATITUDES OF THE NORTHERN HEMISPHERE DURING EARLY DECEMBER.  
 
THE ENSEMBLE MEANS ARE IN EXCELLENT AGREEMENT WITH A HIGHLY AMPLIFIED RIDGE  
ALONG THE WEST COAST WITH A LARGE POSITIVE 500-HPA HEIGHT ANOMALY CENTER OF  
MORE THAN 240 METERS OVER THE ALASKA PANHANDLE. THE TEMPERATURE OUTLOOK DURING  
WEEK-2 IS BASED ON TELECONNECTIONS UPON THIS LARGE 500-HPA HEIGHT ANOMALY  
CENTER ALONG WITH GUIDANCE FROM THE DYNAMICAL AND STATISTICAL TOOLS. A LARGE  
INCREASE IN THE SPATIAL COVERAGE OF BELOW NORMAL TEMPERATURES IS LIKELY TO  
OCCUR EARLY IN WEEK-2. THEREFORE, BELOW NORMAL TEMPERATURES ARE FAVORED FOR  
MUCH OF THE CENTRAL AND EASTERN CONUS. THE HIGHEST PROBABILITIES FOR BELOW  
NORMAL TEMPERATURES ARE FORECAST ACROSS THE TENNESSEAN VALLEY AND OHIO VALLEY  
WHERE STATISTICAL TOOLS HAVE A STRONG SIGNAL. TEMPERATURE TOOLS VARY ACROSS THE  
WESTERN U.S. BUT IN GENERAL A GRADUAL WARMING TREND IS EXPECTED AS THE  
UPPER-LEVEL TROUGH EXITS THIS REGION. SOUTHEASTERLY FLOW CONTINUES TO FAVOR  
ABOVE NORMAL TEMPERATURES ACROSS SOUTHERN CALIFORNIA.  
 
ELEVATED ODDS FOR ABOVE NORMAL PRECIPITATION ARE EXPECTED TO BE LIMITED TO  
PARTS OF THE SOUTHERN PLAINS AND FLORIDA DUE TO THE PRESENCE OF A FRONT AND  
WAVE OF LOW PRESSURE EARLY IN WEEK-2. STRONG COLD AIR ADVECTION IS EXPECTED TO  
PROMOTE LAKE-EFFECT SNOW WITH ABOVE NORMAL PRECIPITATION FAVORED DOWNWIND OF  
THE WESTERN GREAT LAKES. THE HIGHEST PROBABILITIES FOR BELOW NORMAL  
PRECIPITATION ARE INDICATED ACROSS NORTHERN CALIFORNIA AND THE PACIFIC  
NORTHWEST, BASED ON THE HIGH AMPLITUDE RIDGE ALOFT AND STRONG SUPPORT FROM  
STATISTICAL AND DYNAMICAL PRECIPITATION TOOLS.  
 
THE LONGWAVE PATTERN ALOFT AND THE FLOW AT 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  
ACROSS ALASKA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 10% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 10% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 10% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11, 5% OF  
TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 11, 50% OF TODAY'S 0Z EUROPEAN  
ENSEMBLE MEAN CENTERED ON DAY 11, AND 15% 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 - 19861126 - 19981122 - 19741123  
 
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 - 19861125 - 19981119 - 19981124 - 19511129  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 05 - 09 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON B B NRN CALIF A B  
SRN CALIF A B IDAHO B B NEVADA A B  
W MONTANA N B E MONTANA A B WYOMING N B  
UTAH N B ARIZONA A B COLORADO B B  
NEW MEXICO B N N DAKOTA N A S DAKOTA N N  
NEBRASKA N B KANSAS B B OKLAHOMA B B  
N TEXAS B N S TEXAS B A W TEXAS B A  
MINNESOTA B A IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B A WISCONSIN B N  
ILLINOIS B B MISSISSIPPI B A MICHIGAN B A  
INDIANA B A OHIO B A KENTUCKY B A  
TENNESSEE B A ALABAMA B A NEW YORK A A  
VERMONT A A NEW HAMP A A MAINE A A  
MASS A A CONN A A RHODE IS A A  
PENN N A NEW JERSEY N A W VIRGINIA B A  
MARYLAND N A DELAWARE N A VIRGINIA B A  
N CAROLINA B A S CAROLINA B A GEORGIA B A  
FL PNHDL B A FL PENIN N 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 07 - 13 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 N B E MONTANA A B WYOMING A B  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA N N S DAKOTA N B  
NEBRASKA N B KANSAS B B OKLAHOMA B B  
N TEXAS B B S TEXAS B N 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 N  
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 N N  
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 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 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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