035  
FXUS06 KWBC 272001  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST MON NOVEMBER 27 2017  
 
6-10 DAY OUTLOOK FOR DEC 03 - 07 2017  
 
THE 0Z/6Z GFS AND 0Z ECMWF ENSEMBLE MEANS AND THEIR RESPECTIVE DETERMINISTIC  
SOLUTIONS ARE IN EXCELLENT AGREEMENT ON THE 500-HPA LONGWAVE PATTERN. THESE  
MODEL SOLUTIONS FEATURE A PAIR OF HIGHLY AMPLIFIED RIDGES OVER THE SOUTHEASTERN  
U.S. AND OFFSHORE OF THE WEST COAST. DETERMINISTIC MODEL SOLUTIONS CONTINUE TO  
INDICATE AN AMPLIFYING UPPER-LEVEL TROUGH ENTERING THE WESTERN U.S. BY DAY 6  
AND THEN THE HIGHLY ANOMALOUS TROUGH BECOMING CENTERED OVER THE FOUR CORNERS  
REGION BY DAY 8. DUE TO EXCELLENT CONTINUITY SINCE LATE LAST WEEK, A RELATIVELY  
HIGH WEIGHTING OF THE DETERMINISTIC 0Z ECMWF WAS USED IN CREATING THE MANUAL  
500-HPA BLEND.  
 
THE AMPLIFYING UPPER-LEVEL TROUGH INCREASES CHANCES FOR BELOW NORMAL  
TEMPERATURES ACROSS THE WESTERN U.S. THE HIGHEST CHANCES FOR BELOW NORMAL  
TEMPERATURES ARE FORECAST ACROSS THE GREAT BASIN AND THE DESERT SOUTHWEST DUE  
TO THE LIKELIHOOD OF WIDESPREAD PRECIPITATION. INCREASING SOUTHERLY FLOW AT THE  
SURFACE, AHEAD OF THE UPPER-LEVEL TROUGH, ENHANCES ODDS FOR ABOVE NORMAL  
TEMPERATURES ACROSS THE EASTERN TWO-THIRDS OF THE CONUS WITH THE HIGHEST ODDS  
FORECAST ACROSS THE MIDWEST WHERE DAILY TEMPERATURE DEPARTURES OF +10 TO 20  
DEGREES F ARE FORECAST EARLY IN THE PERIOD.  
 
THE AMPLIFIED TROUGH ALOFT INCREASES CHANCES FOR ABOVE NORMAL PRECIPITATION  
ACROSS THE SOUTHWESTERN U.S. ALONG WITH THE CENTRAL AND SOUTHERN ROCKIES. THE  
DETERMINISTIC 0Z ECMWF INDICATES MORE THAN 2 INCHES, LIQUID EQUIVALENT, ON DAYS  
6 AND 7 ACROSS NORTHERN ARIZONA. SURFACE CYCLOGENESIS ON THE LEE SIDE OF THE  
ROCKIES IS LIKELY DURING THIS PERIOD WITH A SUBSEQUENT NORTHEAST TRACK.  
THEREFORE, A BROAD AREA WITH ELEVATED CHANCES OF ABOVE NORMAL PRECIPITATION IS  
FORECAST FROM THE GREAT PLAINS EAST TO THE MISSISSIPPI VALLEY. THE EVOLVING  
LONGWAVE PATTERN SIGNALS AN INCREASING RISK OF HEAVY, CONVECTIVE RAINFALL  
ACROSS PARTS OF THE SOUTHERN GREAT PLAINS AND MIDDLE MISSISSIPPI VALLEY. BELOW  
NORMAL PRECIPITATION IS FAVORED ALONG THE EAST COAST TO THE EAST OF THE 500-HPA  
RIDGE AXIS, WHILE MEAN OFFSHORE FLOW DURING THE 5-DAY PERIOD STRONGLY INCREASES  
CHANCES FOR BELOW NORMAL PRECIPITATION ACROSS NORTHERN CALIFORNIA AND THE  
PACIFIC NORTHWEST.  
 
AN UPPER-LEVEL TROUGH OVER THE ALEUTIANS AND SOUTHWESTERLY FLOW AT THE SURFACE  
INCREASE CHANCES FOR ABOVE NORMAL TEMPERATURES AND PRECIPITATION THROUGHOUT  
MUCH OF ALASKA.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 15% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 40% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 30%  
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  
EXCELLENT AGREEMENT AMONG THE ECMWF AND GFS ENSEMBLE MEANS AND THEIR RESPECTIVE  
DETERMINISTIC SOLUTIONS BUT CONFIDENCE IS REDUCED SLIGHTLY DUE TO AN EXPECTED  
PATTERN CHANGE BY THE END OF THE PERIOD.  
 
8-14 DAY OUTLOOK FOR DEC 05 - 11 2017  
 
THE ENSEMBLE MEANS HAVE TRENDED TOWARD A MORE AMPLIFIED UPPER-LEVEL RIDGE  
BECOMING ESTABLISHED ALONG THE WEST COAST DURING WEEK-2. TELECONNECTIONS UPON A  
LARGE POSITIVE 500-HPA HEIGHT ANOMALY CENTER NEAR VANCOUVER ISLAND AND NEAR THE  
SOUTHERN TIP OF GREENLAND FAVOR THE DEVELOPMENT OF AN AMPLIFIED TROUGH OVER THE  
EAST-CENTRAL U.S. SINCE THE 0Z CANADIAN ENSEMBLE MEAN HAS MORE TROUGHING IN  
THIS REGION, ITS SOLUTION WAS USED IN CREATING THE MANUAL 500-HPA BLEND FOR THE  
WEEK-2 PERIOD. THE GFS ENSEMBLE MEMBERS INDICATE THE ARCTIC OSCILLATION INDEX  
BECOMING MORE NEGATIVE WITH TIME AS POSITIVE 500-HPA HEIGHT ANOMALIES ARE  
PROMINENT OVER THE HIGHER LATITUDES OF THE NORTHERN HEMISPHERE DURING EARLY  
DECEMBER.  
 
THE MADDEN-JULIAN OSCILLATION (MJO) IS BECOMING MORE COHERENT WITH ITS ENHANCED  
PHASE ACROSS THE EASTERN INDIAN OCEAN AND WESTERN MARITIME CONTINENT. DYNAMICAL  
MODEL FORECASTS ARE IN GOOD AGREEMENT AND FEATURE AN EASTWARD PROPAGATION OF A  
MJO TO THE WEST PACIFIC LATER IN WEEK-2. AN INCREASING CHANCE OF BELOW TO MUCH  
BELOW NORMAL TEMPERATURES ACROSS THE LOWER 48 DURING MID-DECEMBER WOULD BE  
CONSISTENT WITH THE MJO EVOLUTION. HOWEVER, THE EXACT TIMING IS UNCERTAIN AND  
MAY NOT OCCUR UNTIL LATE IN WEEK-2. GIVEN THE PREDICTED LARGE POSITIVE  
TEMPERATURE ANOMALIES EARLY IN WEEK-2, NEAR TO ABOVE NORMAL TEMPERATURES ARE  
FAVORED FOR PARTS OF THE CENTRAL AND EASTERN U.S. BUT BELOW NORMAL TEMPERATURES  
ARE LIKELY TO DEVELOP ACROSS THESE AREAS BY THE END OF WEEK-2. AN AMPLIFIED  
TROUGH AT LEAST EARLY IN WEEK-2 FAVORS BELOW NORMAL TEMPERATURES ACROSS PARTS  
OF THE SOUTHWESTERN U.S. A STRONG SURFACE HIGH IS LIKELY TO PROMOTE LOW-LEVEL  
INVERSIONS AND FAVORS BELOW NORMAL TEMPERATURES ACROSS THE GREAT BASIN, WHILE  
INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES ACROSS CALIFORNIA IS ASSOCIATED  
WITH OFFSHORE FLOW.  
 
THE DETERMINISTIC 0Z ECMWF MODEL INDICATES SURFACE CYCLOGENESIS ACROSS THE  
CENTRAL OR SOUTHERN HIGH PLAINS BY DAY 8 WHICH IS CONSISTENT WITH THE AMPLIFIED  
UPPER-LEVEL TROUGH OVER THE FOUR CORNERS REGION. HIGH ODDS FOR ABOVE NORMAL  
PRECIPITATION ARE FORECAST ACROSS THE GREAT PLAINS AND MISSISSIPPI VALLEY,  
ALONG THE EXPECTED TRACK OF THIS LOW PRESSURE SYSTEM AND ITS ASSOCIATED COLD  
FRONT. NEAR TO BELOW NORMAL PRECIPITATION IS FAVORED EAST OF THE APPALACHIANS  
AS THE FRONT IS EXPECTED TO SLOW AS IT NEARS THE EAST COAST. A HIGH AMPLITUDE  
RIDGE IS LIKELY TO MAINTAIN BELOW NORMAL PRECIPITATION ACROSS NORTHERN  
CALIFORNIA AND THE PACIFIC NORTHWEST.  
 
THE LONGWAVEV PATTERN ALOFT AND THE SURFACE FLOW ARE EXPECTED TO CHANGE LITTLE  
FROM THE DAY 6-10 PERIOD TO WEEK-2 ACROSS ALASKA. THEREFORE, INCREASED CHANCES  
OF ABOVE NORMAL TEMPERATURES AND ABOVE NORMAL PRECIPITATION ARE FORECAST TO  
CONTINUE INTO WEEK-2 FOR ALASKA.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 30% OF TODAY'S 6Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 40% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN  
CENTERED ON DAY 11, AND 30% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON  
DAY 11  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: AVERAGE, 3 OUT OF 5, DUE TO  
GOOD AGREEMENT AMONG THE PRECIPITATION TOOLS OFFSET BY THE UNCERTAINTY ON THE  
TIMING OF A LIKELY TRANSITION TO BELOW-NORMAL TEMPERATURES ACROSS THE CENTRAL  
AND EASTERN U.S.  
 
FORECASTER: BRAD PUGH  
 
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:  
19991128 - 19711109 - 19651206 - 19971123 - 19901209  
 
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:  
19651205 - 19711108 - 20031202 - 19971122 - 19991127  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 03 - 07 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B B OREGON B B NRN CALIF B B  
SRN CALIF B A IDAHO B B NEVADA B A  
W MONTANA B B E MONTANA A N WYOMING B A  
UTAH B A ARIZONA B A COLORADO A A  
NEW MEXICO N A N DAKOTA A A S DAKOTA A A  
NEBRASKA A A KANSAS A A OKLAHOMA A A  
N TEXAS A A S TEXAS A A W TEXAS A A  
MINNESOTA A A IOWA A A MISSOURI A A  
ARKANSAS A A LOUISIANA A A WISCONSIN A A  
ILLINOIS A A MISSISSIPPI A A MICHIGAN A A  
INDIANA A A OHIO A A KENTUCKY A A  
TENNESSEE A A ALABAMA A N NEW YORK A N  
VERMONT A B NEW HAMP A B MAINE A B  
MASS A B CONN A B RHODE IS A B  
PENN A N NEW JERSEY A B W VIRGINIA A N  
MARYLAND A B DELAWARE A B VIRGINIA A B  
N CAROLINA A B S CAROLINA A B GEORGIA A B  
FL PNHDL A B FL PENIN A B AK N SLOPE A N  
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 DEC 05 - 11 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 B B  
W MONTANA B B E MONTANA N B WYOMING B B  
UTAH B B ARIZONA B A COLORADO B A  
NEW MEXICO B A N DAKOTA A A S DAKOTA A A  
NEBRASKA N A KANSAS N A OKLAHOMA B A  
N TEXAS B A S TEXAS B A W TEXAS B A  
MINNESOTA A A IOWA A A MISSOURI N A  
ARKANSAS N A LOUISIANA B A WISCONSIN A A  
ILLINOIS N A MISSISSIPPI N A MICHIGAN A A  
INDIANA N A OHIO A A KENTUCKY N A  
TENNESSEE N A ALABAMA N A NEW YORK A A  
VERMONT A N NEW HAMP A N MAINE A N  
MASS A N CONN A N RHODE IS A N  
PENN A A NEW JERSEY A N W VIRGINIA A A  
MARYLAND A B DELAWARE A B VIRGINIA A N  
N CAROLINA A B S CAROLINA A B GEORGIA N N  
FL PNHDL N N FL PENIN N B AK N SLOPE A N  
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  
 
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