927  
FXUS06 KWBC 052032  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST FRI JANUARY 05 2018  
 
6-10 DAY OUTLOOK FOR JAN 11 - 15 2018  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE PREDICTED 500-HPA  
FLOW PATTERN OVER THE FORECAST DOMAIN. THE HIGHLY AMPLIFIED RIDGE THAT HAS BEEN  
PREDICTED NEAR THE WEST COAST OF NORTH AMERICA THIS WEEK IS EXPECTED TO WEAKEN  
SIGNIFICANTLY IN THE VICINITY OF NORTHWESTERN CANADA. THIS ALLOWS FOR THE  
POTENTIAL CONNECTION OF THE POLAR VORTEX OVER NORTHEASTERN CANADA WITH AN  
ANOMALOUS TROUGH EXPECTED OVER THE BERING SEA AND WESTERN GULF OF ALASKA.  
SHOULD THIS CONNECTION OCCUR AND STRENGTHEN, IT SUGGESTS THE PRIMARY SOURCE  
REGION FOR ARCTIC AIR MASSES (WESTERN CANADA) WILL BE OVERRUN WITH MILDER  
PACIFIC AIR. THIS SCENARIO SUPPORTS THE IDEA OF A WARMING TREND ACROSS THE  
LOWER 48 STATES. FOR ALASKA, HOWEVER, A COOLDOWN CAN BE EXPECTED AS THE RIDGE  
DEPARTS THE REGION, AND EASTERLY ANOMALOUS FLOW SETS IN. DURING THE PAST 60  
DAYS, ALL ENSEMBLE MEANS CONTINUE TO OUTPERFORM THE DETERMINISTIC RUNS, AS  
INDICATED BY ANOMALY CORRELATION SCORES. ACCORDINGLY, 80 PERCENT OF THE  
OFFICIAL HEIGHT BLEND WAS COMPOSED OF ENSEMBLE MEAN SOLUTIONS, WITH THE  
REMAINING 20 PERCENT COMPOSED OF DETERMINISTIC RUNS. ENSEMBLE SPREAD (AT 5760  
M) IS MODERATE TO LARGE OVER THE CONUS, AND MODERATE OVER THE UPSTREAM REGION  
OF THE EASTERN PACIFIC.  
 
THE TEMPERATURE OUTLOOK FOR THE 6-10 DAY PERIOD IS LARGELY BASED ON THE  
AUTOMATED TEMPERATURE FORECAST, THE GEFS AND ECMWF CALIBRATED REFORECAST TOOLS,  
AND DYNAMICAL MODEL TEMPERATURE FORECASTS. THE RIDGE PREDICTED OVER WESTERN  
NORTH AMERICA AND ASSOCIATED POSITIVE HEIGHT ANOMALIES FAVOR ABOVE NORMAL  
TEMPERATURES FOR MOST OF THIS AREA (INCLUDING ALL AREAS WEST OF THE CONTINENTAL  
DIVIDE IN THE LOWER 48 STATES). THE EXCEPTION IS BETWEEN THE ALASKA RANGE AND  
THE BROOKS RANGE, WHERE NEAR NORMAL TEMPERATURES ARE FAVORED, DUE TO THE  
EARLIER MENTION OF MUCH WEAKER RIDGING IN THIS AREA. ODDS OF BELOW NORMAL  
TEMPERATURES ARE SLIGHTLY ELEVATED OVER THE VICINITY OF THE MISSISSIPPI VALLEY  
AND THE LOWER SOUTHERN PLAINS OF TEXAS AND OKLAHOMA. THIS AREA REPRESENTS THE  
FINAL STAGE OF THE VERY COLD SPELL THAT DOMINATED THE NATION EAST OF THE  
ROCKIES DURING THE PAST FEW WEEKS. ODDS OF ABOVE NORMAL TEMPERATURES ARE  
ENHANCED FROM ABOUT THE APPALACHIANS EASTWARD TO THE ATLANTIC COAST, IN ADVANCE  
OF AN APPROACHING TROUGH.  
 
LOW PRESSURE NEAR THE ALEUTIAN ARCHIPELAGO FAVORS ABOVE NORMAL PRECIPITATION  
FOR THE SOUTHERN COAST OF ALASKA DURING THE 6-10 DAY PERIOD. DRIER THAN NORMAL  
CONDITIONS ARE FAVORED OVER THE CENTRAL INTERIOR OF ALASKA WITH ENHANCED  
DOWNSLOPE WINDS EXPECTED OFF THE ALASKA RANGE, AND CLIMATOLOGICALLY DRY  
CONDITIONS (I.E., NEAR NORMAL PRECIPITATION) ARE FORECAST FOR THE NORTH SLOPE.  
ABOVE NORMAL PRECIPITATION IS EXPECTED FOR THE NORTH-CENTRAL PLAINS, THE UPPER  
MISSISSIPPI VALLEY, AND PRACTICALLY ALL AREAS EAST OF THE MISSISSIPPI RIVER,  
ASSOCIATED WITH A MEAN 500-HPA TROUGH IN THIS AREA. ABOVE NORMAL PRECIPITATION  
IS ALSO ANTICIPATED TO MOVE INTO THE PACIFIC NORTHWEST, AS A TROUGH APPROACHES  
FROM THE WEST. AREAS OF BELOW NORMAL PRECIPITATION ARE FAVORED ACROSS  
CALIFORNIA, NORTHERN NEVADA, AND MOST OF THE ROCKY MOUNTAIN REGION, AS WELL AS  
FROM SOUTHERN TEXAS TO WESTERN ARKANSAS. THE PRECIPITATION OUTLOOK FOR THE 6-10  
DAY PERIOD IS LARGELY BASED ON THE AUTOMATED PRECIPITATION FORECAST, THE GEFS  
AND ECMWF CALIBRATED REFORECAST TOOLS, DYNAMICAL MODEL PRECIPITATION FORECASTS,  
AND INSPECTION OF STORM TRACKS AS DEPICTED BY TODAY'S 12Z DETERMINISTIC GFS RUN.  
 
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 OPERATIONAL 0Z GFS CENTERED ON DAY 8, 5% OF TODAY'S  
OPERATIONAL 6Z GFS CENTERED ON DAY 8, 20% 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  
REASONABLY GOOD AGREEMENT AMONG MOST MODELS AND TOOLS.  
 
8-14 DAY OUTLOOK FOR JAN 13 - 19 2018  
 
DURING WEEK-2, MODELS ARE IN FAIRLY GOOD AGREEMENT, AND THEY PREDICT A SIMILAR  
CIRCULATION PATTERN TO THAT EXPECTED DURING THE 6-10 DAY PERIOD. THE MANUAL  
HEIGHT BLEND DEPICTS CONTINUED PROPAGATION OF THE LARGE ANOMALOUS TROUGH WHICH  
EXTENDS FROM THE BERING SEA AND ALEUTIANS TO THE CENTRAL GULF OF ALASKA. STORM  
SYSTEMS ON THE ADVANCING (EASTERN) FLANK OF THIS TROUGH ARE EXPECTED TO MOVE  
ACROSS THE WEST COAST STATES, INCLUDING NORTHERN AND CENTRAL CALIFORNIA. THE  
TROUGH PREDICTED OVER THE EAST-CENTRAL CONUS DURING THE 6-10 DAY PERIOD IS  
FORECAST TO DEAMPLIFY DURING WEEK-2, WITH RAPIDLY RISING MID-TROPOSPHERIC  
HEIGHTS OVER THIS REGION.  
 
ABOVE NORMAL TEMPERATURES ARE STILL FAVORED IN SOUTHERN ALASKA, BUT AREAS NORTH  
OF THE ALASKA RANGE ARE FORECAST TO COOL DOWN TO MORE SEASONABLE LEVELS. WARMER  
THAN NORMAL CONDITIONS ARE ANTICIPATED TO SPREAD RAPIDLY EASTWARD ACROSS MOST  
OF THE CONUS DURING THE WEEK-2 PERIOD, WITH THE EXCEPTION OF THE GULF COAST  
STATES AND CAROLINAS. THIS RAPID WARMUP IS ATTRIBUTED TO THE FORECAST OF  
RAPIDLY RISING HEIGHTS ACROSS THE CENTRAL AND EAST-CENTRAL CONUS. THE ECMWF  
ENSEMBLE MEAN CALIBRATED REFORECAST TEMPERATURE TOOL IS FASTER THAN ITS GEFS  
COUNTERPART TO WARM UP THE EASTERN CONUS.  
 
FOR THE WEEK-2 PRECIPITATION OUTLOOK, A DRIER PATTERN IS PREDICTED OVER  
SOUTHERN ALASKA AS THE NEARBY ANOMALOUS TROUGH PROGRESSES DOWNSTREAM OF THIS  
AREA. MOISTURE ASSOCIATED WITH THE LEADING PORTION OF THIS ANOMALOUS TROUGH IS  
FORECAST TO OVERSPREAD THE PACIFIC NORTHWEST, NORTHERN AND CENTRAL CALIFORNIA,  
THE NORTHERN AND CENTRAL INTERMOUNTAIN REGION, AND THE NORTHERN ROCKIES. FOR  
THE REMAINDER OF THE CONUS, A RAPID TRANSITION TO A DRIER PATTERN IS  
ANTICIPATED. THE FORECAST FOR THE ATLANTIC COASTAL PLAIN IS FAIRLY UNCERTAIN.  
THE GFS AND ECMWF REFORECAST TOOLS, AND THE CONSOLIDATION AND AUTOMATED  
PRECIPITATION TOOLS PREDICT BELOW NORMAL PRECIPITATION FOR THE WEEK-2 PERIOD  
(ALBEIT WITH LOW PROBABILITIES). THIS CONFLICTS WITH RECENT RUNS OF THE  
DETERMINISTIC GFS THAT SHOW TWO LOW PRESSURE AREAS MOVING ACROSS THE  
MID-ATLANTIC AND NORTHEAST REGIONS IN PARTICULAR. THEREFORE, A FORECAST OF NEAR  
NORMAL PRECIPITATION SEEMS TO BE THE BEST CHOICE.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 25% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 25% OF TODAY'S 6Z GFS ENSEMBLE 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: NEAR AVERAGE, 3 OUT OF 5, DUE TO  
REASONABLE OVERALL MODEL AND TOOL AGREEMENT, BUT OFFSET BY THE UNCERTAINTY  
INHERENT IN A TRANSITIONING CIRCULATION PATTERN.  
 
FORECASTER: ANTHONY A  
 
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:  
19561231 - 19851227 - 19881216 - 20090119 - 19810106  
 
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:  
19561231 - 19851227 - 20090118 - 19810109 - 19881215  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 11 - 15 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A A OREGON A N NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA A B E MONTANA N B WYOMING A B  
UTAH A B ARIZONA A B COLORADO A N  
NEW MEXICO A B N DAKOTA N N S DAKOTA N A  
NEBRASKA N A KANSAS N N OKLAHOMA B N  
N TEXAS B B S TEXAS B B W TEXAS N N  
MINNESOTA B A IOWA B A MISSOURI B N  
ARKANSAS B N LOUISIANA B N WISCONSIN B A  
ILLINOIS B A MISSISSIPPI B N MICHIGAN N A  
INDIANA N A OHIO N A KENTUCKY N A  
TENNESSEE N A ALABAMA N 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 A A NEW JERSEY A A W VIRGINIA A A  
MARYLAND A A DELAWARE A A VIRGINIA A A  
N CAROLINA A A S CAROLINA A A GEORGIA A A  
FL PNHDL A A FL PENIN A A AK N SLOPE A N  
AK ALEUTIAN A A AK WESTERN N A AK INT BSN N B  
AK S INT N A AK SO COAST A A AK PNHDL A A  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR JAN 13 - 19 2018  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A A OREGON A A NRN CALIF A A  
SRN CALIF A N IDAHO A A NEVADA A A  
W MONTANA A A E MONTANA A N WYOMING A N  
UTAH A N ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA A N S DAKOTA A B  
NEBRASKA A B KANSAS A B OKLAHOMA A B  
N TEXAS A B S TEXAS N B W TEXAS A B  
MINNESOTA A N IOWA A N MISSOURI A B  
ARKANSAS A B LOUISIANA N B WISCONSIN A N  
ILLINOIS A B MISSISSIPPI N B MICHIGAN A B  
INDIANA A B OHIO A B KENTUCKY A B  
TENNESSEE A B ALABAMA N B NEW YORK A B  
VERMONT A B NEW HAMP A N MAINE A N  
MASS A N CONN A N RHODE IS A N  
PENN A B NEW JERSEY A N W VIRGINIA A B  
MARYLAND A N DELAWARE N N VIRGINIA A B  
N CAROLINA N N S CAROLINA N B GEORGIA N B  
FL PNHDL N B FL PENIN N N AK N SLOPE N N  
AK ALEUTIAN A B AK WESTERN N B AK INT BSN N B  
AK S INT A N AK SO COAST A N 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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