587  
FXUS06 KWBC 292002  
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 29 2017  
 
6-10 DAY OUTLOOK FOR JAN 04 - 08 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, OVER THE EAST PACIFIC  
APPROACHING THE U.S. WEST COAST, AND WEST OF THE BERING SEA, WHILE A RIDGE IS  
EXPECTED OVER THE PACIFIC NORTHWEST EXTENDING NORTH/NORTHWESTWARD TO ALASKA.  
THE LARGEST MODEL DISAGREEMENT CONCERNS THE HANDLING OF TROUGH ENERGY  
APPROACHING THE U.S. WEST COAST AND THE DEVELOPMENT OF A SOUTHERN JET STREAM  
UNDERCUTTING THE RIDGE OVER WESTERN NORTH AMERICA. THE GFS BASED ENSEMBLE MEAN  
SOLUTIONS DEPICT THE WEST COAST RIDGE EXTENDING DOWN TO THE SOUTHWEST CONUS AND  
SOUTHERN STREAM ENERGY UNDERCUTTING IT OVER NORTHERN MEXICO, WHILE THE ECMWF  
AND CANADIAN ENSEMBLES SHOW LESS RIDGING IN THIS AREA AND SOUTHERN JET STREAM  
ENERGY FURTHER NORTH. THIS MODEL DISAGREEMENT IS ALSO EVIDENT IN THE ENSEMBLE  
SPAGHETTI CHARTS WHICH GENERALLY INDICATE LOW TO MODERATE SPREAD OVER THE  
CENTRAL AND 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, WEAKLY POSITIVE AT 10, AND BE CLOSE  
TO ZERO BY DAY 14. THE AO INDEX WHICH HAS RECENTLY BEEN CLOSE TO ZERO IS  
EXPECTED TO BE VERY WEAKLY POSITIVE AT DAY 7, BE WEAKLY NEGATIVE 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 HALF OF THE CONUS, PARTS OF  
CALIFORNIA, AND THE ALEUTIANS, WHILE ABOVE NORMAL HEIGHTS ARE ANTICIPATED FOR  
MOST OF THE WESTERN HALF 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 HALF OF THE CONUS AND PARTS OF THE HIGH  
PLAINS. ANOMALOUS EASTERLY FLOW TILTS THE ODDS TO BELOW NORMAL TEMPERATURES FOR  
PARTS OF THE NORTHERN ROCKIES, NORTHERN PACIFIC NORTHWEST, AND NORTHERN  
INTERMOUNTAIN WEST. ABOVE NORMAL HEIGHTS TILT THE ODDS TO NEAR TO ABOVE NORMAL  
TEMPERATURES FOR THE REMAINDER OF THE CONUS AND ALASKA.  
 
ARCTIC HIGH PRESSURE IS EXPECTED TO DOMINATE MOST OF THE EASTERN AND CENTRAL  
CONUS, WHICH FAVORS NEAR TO BELOW NORMAL PRECIPITATION FOR MUCH OF THE REGION.  
ABOVE NORMAL HEIGHTS ENHANCE PROBABILITIES OF BELOW NORMAL PRECIPITATION FOR  
THE NORTHWESTERN CONUS. THE FORECAST TROUGH APPROACHING CALIFORNIA FROM THE  
EAST PACIFIC FAVORS ABOVE NORMAL PRECIPITATION FOR CALIFORNIA, PARTS OF THE  
SOUTHWEST CONUS, SOUTHERN ROCKIES, AND SOUTHERN HIGH PLAINS. THE TROUGH WEST OF  
THE BERING SEA ENHANCES PROBABILITIES OF ABOVE NORMAL PRECIPITATION FOR MOST OF  
WESTERN AND CENTRAL ALASKA.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 25% 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 0Z GFS CENTERED ON DAY 8, 25% OF TODAY'S 0Z EUROPEAN  
ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN  
CENTERED ON DAY 7, AND 5% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8  
 
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
VERY GOOD MODEL AGREEMENT ON AN AMPLIFIED CIRCULATION PATTERN OFFSET BY LARGE  
SPREAD AMONG ENSEMBLE MEMBERS FOR THE WESTERN CONUS.  
 
8-14 DAY OUTLOOK FOR JAN 06 - 12 2018  
 
DURING WEEK-2, ENSEMBLE MODEL FORECASTS PREDICT A DEAMPLIFICATION AND  
PROGRESSION OF THE 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.  
ENSEMBLE SPREAD IS GENERALLY LOW TO MODERATE OVER MOST OF THE CENTRAL AND  
EASTERN CONUS, AND MODERATE TO LARGE OVER THE WESTERN CONUS AND EASTERN  
PACIFIC. 500-HPA HEIGHTS ARE FORECAST TO BE NEAR TO BELOW NORMAL OVER THE  
SOUTHWESTERN CONUS, AND NEAR TO ABOVE NORMAL OVER THE REMAINDER OF THE CONUS  
AND ALASKA.  
 
THE TEMPERATURE ANOMALY PATTERN EXPECTED FOR WEEK-2 IS QUITE SIMILAR TO THAT  
FORECAST FOR THE 6-10 DAY PERIOD. THE ONLY NOTABLE DIFFERENCE IS OVER SOUTHERN  
FLORIDA WHERE RISING HEIGHTS ENHANCE PROBABILITIES FOR ABOVE NORMAL  
TEMPERATURES. WITH HEIGHTS ANTICIPATED TO RISE OVER THE EASTERN U.S. DURING THE  
PERIOD, THE 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 WESTERN AND CENTRAL PORTIONS OF THE NATION.  
ANOMALOUS NORTHEASTERLY FLOW FAVORS BELOW NORMAL PRECIPITATION FOR PARTS OF THE  
NORTHWEST. ABOVE NORMAL HEIGHTS TILT THE ODDS TO BELOW NORMAL PRECIPITATION FOR  
PARTS OF THE NORTHEAST AND FLORIDA. THE TROUGH NEAR THE BERING SEA ENHANCES  
PROBABILITIES OF ABOVE NORMAL PRECIPITATION FOR MOST OF ALASKA WHILE THE RIDGE  
OVER THE NORTHWEST TILT THE ODDS TO BELOW NORMAL PRECIPITATION FOR PARTS OF THE  
PACIFIC NORTHWEST AND THE ALASKA PANHANDLE.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 25% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 5% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 25% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11, 15% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 30% OF YESTERDAY'S  
12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOUT AVERAGE, 3 OUT OF 5, DUE TO  
GOOD MODEL AGREEMENT OFFSET BY 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:  
20040105 - 19940104 - 19680106 - 19891218 - 19581209  
 
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:  
19940104 - 19581208 - 20040105 - 19831224 - 19551216  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 04 - 08 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON N N NRN CALIF A A  
SRN CALIF A A IDAHO N B NEVADA A A  
W MONTANA B B E MONTANA N N WYOMING N B  
UTAH A A ARIZONA A A COLORADO A N  
NEW MEXICO A A N DAKOTA N B S DAKOTA B B  
NEBRASKA B B KANSAS B B OKLAHOMA B B  
N TEXAS B B S TEXAS B B W TEXAS B N  
MINNESOTA B B IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN B N  
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 B CONN B B RHODE IS B B  
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 B 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 N N  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 06 - 12 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N B OREGON A N NRN CALIF A A  
SRN CALIF A A IDAHO A A NEVADA A A  
W MONTANA B A E MONTANA B N WYOMING N A  
UTAH A A ARIZONA A A COLORADO A A  
NEW MEXICO A A N DAKOTA N N S DAKOTA B N  
NEBRASKA B A KANSAS B A OKLAHOMA B A  
N TEXAS B A S TEXAS B A W TEXAS N A  
MINNESOTA B N IOWA B A MISSOURI B A  
ARKANSAS B A LOUISIANA B A WISCONSIN B N  
ILLINOIS B A MISSISSIPPI B A MICHIGAN B N  
INDIANA B A OHIO B N KENTUCKY B A  
TENNESSEE B A ALABAMA B A NEW YORK B N  
VERMONT B B NEW HAMP B B MAINE B N  
MASS B B CONN B B 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 N S CAROLINA B N GEORGIA B N  
FL PNHDL B N FL PENIN N B 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 N B  
 
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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