784  
FXUS06 KWBC 282002  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST THU DECEMBER 28 2017  
 
6-10 DAY OUTLOOK FOR JAN 03 - 07 2018  
 
TODAY'S ENSEMBLE MEAN FORECASTS ARE IN 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 THE BERING SEA, WHILE A RIDGE IS EXPECTED  
OVER THE PACIFIC NORTHWEST EXTENDING NORTH/NORTHWESTWARD TO ALASKA. THE  
ENSEMBLE SPAGHETTI CHARTS INDICATE LOW TO MODERATE SPREAD OVER THE CENTRAL AND  
EASTERN CONUS, AND MODERATE TO 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 WEAKLY POSITIVE IS EXPECTED TO BE  
NEAR ZERO AT DAY 7, BE VERY 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 AND THE ALEUTIANS, WHILE  
ABOVE NORMAL HEIGHTS ARE ANTICIPATED FOR THE WESTERN HALF OF THE CONUS, THE  
ALASKA PANHANDLE, AND MAINLAND ALASKA.  
 
BELOW NORMAL HEIGHTS AND OR ANOMALOUS NORTHEASTERLY FLOW FAVOR BELOW NORMAL  
TEMPERATURES FOR MUCH OF THE EASTERN HALF OF THE CONUS, AND 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 CONUS, WHICH  
FAVORS NEAR TO BELOW NORMAL PRECIPITATION FOR MUCH OF THE REGION. THE EXCEPTION  
IS OVER PARTS OF FLORIDA WHERE A FRONTAL SYSTEM TILTS THE ODDS TO ABOVE NORMAL  
PRECIPITATION. 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 PARTS OF  
THE SOUTHWEST CONUS. UPSLOPE FLOW TILTS THE ODDS TO ABOVE NORMAL PRECIPITATION  
FOR PARTS OF THE ROCKIES. THE TROUGH OVER 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 20% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 5% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8, 25% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, 5% OF YESTERDAY'S 12Z  
EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 7, 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: MUCH ABOVE AVERAGE, 5 OUT OF 5,  
DUE TO VERY GOOD MODEL AGREEMENT ON AN AMPLIFIED CIRCULATION PATTERN.  
 
8-14 DAY OUTLOOK FOR JAN 05 - 11 2018  
 
DURING WEEK-2, ENSEMBLE MODEL FORECASTS PREDICT A MAJOR DEAMPLIFICATION AND  
MODERATE 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 MODERATE 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  
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 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 OF ABOVE NORMAL PRECIPITATION FOR MOST OF 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, 20% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11, 35% OF  
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, 10% OF YESTERDAY'S 12Z  
EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10, 10% OF TODAY'S 0Z CANADIAN ENSEMBLE  
MEAN CENTERED ON DAY 11, AND 5% OF YESTERDAY'S 12Z CANADIAN 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 - 19790110 - 19680105 - 19910102  
 
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 - 19581207 - 19831224 - 20040105 - 19910103  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 03 - 07 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON A B NRN CALIF A N  
SRN CALIF A A IDAHO N B NEVADA A A  
W MONTANA B N E MONTANA B A WYOMING N A  
UTAH A A ARIZONA A A COLORADO N A  
NEW MEXICO A A N DAKOTA N B S DAKOTA B B  
NEBRASKA B B KANSAS B N OKLAHOMA B N  
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 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 B VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B N 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 05 - 11 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON N N NRN CALIF A N  
SRN CALIF A A IDAHO B N NEVADA A A  
W MONTANA B B E MONTANA B A 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 N W TEXAS B A  
MINNESOTA N N IOWA B N MISSOURI B A  
ARKANSAS B A LOUISIANA B A WISCONSIN B N  
ILLINOIS B N MISSISSIPPI B A MICHIGAN B A  
INDIANA B N OHIO B N KENTUCKY B N  
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 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 A  
FL PNHDL B A FL PENIN N 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 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.  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page