701  
FXUS06 KWBC 222001  
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 22 2017  
 
6-10 DAY OUTLOOK FOR DEC 28, 2017 - JAN 01, 2018  
 
TODAY'S MODEL FORECASTS ARE IN GOOD AGREEMENT ON A PREDICTED AMPLIFIED 500-HPA  
CIRCULATION PATTERN FOR THE 6-10 DAY PERIOD OVER THE FORECAST DOMAIN. ENSEMBLE  
MEANS FROM THE NCEP GEFS, ECMWF, AND ENVIRONMENT CANADA PREDICT A RIDGE OVER  
THE NORTH PACIFIC AND ALASKA, A DOWNSTREAM TROUGH EXTENDING FROM NORTHERN  
QUEBEC INTO THE NORTH-CENTRAL CONUS, AND ABOVE NORMAL 500-HPA HEIGHTS OVER THE  
WESTERN AND SOUTHWESTERN CONUS.  
 
BELOW NORMAL TEMPERATURES ARE FAVORED FOR SOUTHERN MAINLAND ALASKA AND THE  
ALASKA PANHANDLE, UNDER NORTHEASTERLY FLOW AHEAD OF THE PREDICTED RIDGE. BELOW  
NORMAL TEMPERATURES ARE LIKELY FOR A LARGE AREA OF THE CONUS, UNDER A PREDICTED  
AMPLIFIED TROUGH AND AN INFLUX OF ARCTIC AIR. PROBABILITIES EXCEED 80 PERCENT  
OVER A LARGE AREA OF THE NORTHERN CONUS FROM THE NORTHERN PLAINS ACROSS THE  
GREAT LAKES AND NEW ENGLAND. UNDER PREDICTED SOUTHEASTERLY FLOW, ABOVE NORMAL  
TEMPERATURES ARE FAVORED FOR THE SOUTHERN FLORIDA PENINSULA. ABOVE NORMAL  
TEMPERATURES ARE MOST LIKELY FOR LARGE PARTS OF CALIFORNIA INTO THE GREAT BASIN  
AND SOUTHWEST, UNDER PREDICTED ABOVE NORMAL HEIGHTS.  
 
BELOW NORMAL PRECIPITATION IS LIKELY FOR MOST OF ALASKA UNDER A PREDICTED  
RIDGE. THE PREDICTED TROUGH OVER THE CENTRAL EASTERN CONUS ENHANCES THE  
PROBABILITY OF ABOVE NORMAL PRECIPITATION FROM PARTS OF THE PACIFIC NORTHWEST,  
INTO THE NORTHERN AND CENTRAL GREAT PLAINS, AND ACROSS THE EAST HALF CONUS,  
FOLLOWING THE PREDICTED MEAN FRONTAL BOUNDARY. BELOW NORMAL PRECIPITATION IS  
FAVORED FOR CALIFORNIA, NEVADA AND PARTS OF THE SOUTHWEST UNDER PREDICTED ABOVE  
NORMAL HEIGHTS.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 15% OF TODAY'S GFS SUPERENSEMBLE MEAN 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 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 MODEL AGREEMENT ON A HIGHLY AMPLIFIED FLOW PATTERN, WITH SOME AREAS OF  
DISAGREEMENT IN THE PRECIPITATION FORECAST.  
 
8-14 DAY OUTLOOK FOR DEC 30, 2017 - JAN 05, 2018  
 
IN THE WEEK 2 PERIOD, MODEL FORECASTS PREDICT A SLIGHTLY LESS AMPLIFIED 500-HPA  
TROUGH, RELATIVE TO THE 6-10 DAY PERIOD, ALONG WITH SOME EASTWARD PROGRESSION  
OVER THE CONUS. THE ECMWF ENSEMBLE MEAN MAINTAINS A MORE AMPLIFIED TROUGH INTO  
THE WEEK 2 PERIOD, RELATIVE TO THE NCEP GEFS AND ENVIRONMENT CANADA ENSEMBLE  
MEANS.  
 
ABOVE NORMAL TEMPERATURES REMAIN LIKELY FOR PARTS OF WESTERN MAINLAND ALASKA  
AND THE ALEUTIANS, AHEAD OF A PREDICTED TROUGH. BELOW NORMAL TEMPERATURES  
CONTINUE TO BE FAVORED FOR A LARGE AREA OF THE CONUS, UNDER THE PREDICTED  
TROUGH. ABOVE NORMAL TEMPERATURES ARE LIKELY OVER THE SOUTHWEST CONUS WITH AN  
INFLUX OF RELATIVELY WARM PACIFIC AIR PREDICTED FOR THE REGION.  
 
ABOVE NORMAL PRECIPITATION IS LIKELY OVER PARTS OF WESTERN MAINLAND ALASKA AND  
THE ALEUTIANS, AHEAD OF A PREDICTED TROUGH. THE PRECIPITATION FORECAST OVER THE  
CONUS FOR WEEK 2 IS VERY SIMILAR TO THE 6-10 DAY PERIOD FORECAST. ABOVE NORMAL  
PRECIPITATION IS LIKELY FROM PARTS OF THE PACIFIC NORTHWEST REGION EASTWARD  
ACROSS THE CENTRAL AND EASTERN CONUS. BELOW NORMAL PRECIPITATION IS FAVORED FOR  
PARTS OF CALIFORNIA, NEVADA AND THE SOUTHWEST AHEAD OF A PREDICTED RIDGE.  
 
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, 30% 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: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
AN AMPLIFIED PREDICTED CIRCULATION PATTERN, OFFSET BY INCREASING ENSEMBLE  
SPREAD.  
 
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  
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:  
19621222 - 20071207 - 19721202 - 19981217 - 19921223  
 
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:  
20071207 - 19621222 - 19721201 - 19981217 - 19911202  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 28, 2017 - JAN 01, 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B A OREGON A A NRN CALIF A B  
SRN CALIF A B IDAHO A A NEVADA A B  
W MONTANA B A E MONTANA B A WYOMING B A  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA B A S DAKOTA B A  
NEBRASKA B A KANSAS B N OKLAHOMA B A  
N TEXAS B A S TEXAS B A W TEXAS B N  
MINNESOTA B A IOWA B A MISSOURI B A  
ARKANSAS B A LOUISIANA B A WISCONSIN B A  
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 A  
VERMONT B A NEW HAMP B A MAINE B A  
MASS B A CONN B A RHODE IS B A  
PENN B A NEW JERSEY B A W VIRGINIA B A  
MARYLAND B A DELAWARE B A VIRGINIA B A  
N CAROLINA B A S CAROLINA B A GEORGIA B A  
FL PNHDL B A FL PENIN A A AK N SLOPE N N  
AK ALEUTIAN N N AK WESTERN N B AK INT BSN N B  
AK S INT B B AK SO COAST N N AK PNHDL B N  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 30, 2017 - JAN 05, 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N A OREGON A A NRN CALIF A B  
SRN CALIF A B IDAHO A A NEVADA A B  
W MONTANA N A E MONTANA B A WYOMING N A  
UTAH A B ARIZONA A B COLORADO A N  
NEW MEXICO A B N DAKOTA B A S DAKOTA B A  
NEBRASKA B A KANSAS B A OKLAHOMA B A  
N TEXAS B A S TEXAS B A W TEXAS B N  
MINNESOTA B A 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 A KENTUCKY B A  
TENNESSEE B A ALABAMA B A NEW YORK B A  
VERMONT B A NEW HAMP B A MAINE B A  
MASS B A CONN B A RHODE IS B A  
PENN B A NEW JERSEY B A W VIRGINIA B A  
MARYLAND B A DELAWARE B 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 N B  
AK ALEUTIAN A A AK WESTERN N N AK INT BSN N B  
AK S INT N N AK SO COAST N A AK PNHDL N 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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