070  
FXUS06 KWBC 052035  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST TUE DECEMBER 05 2017  
 
6-10 DAY OUTLOOK FOR DEC 11 - 15 2017  
 
TODAYS ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED BROAD  
SCALE 500-HPA CIRCULATION PATTERN DURING THE 6-10 DAY PERIOD. A HIGH AMPLITUDE  
TROUGH IS PREDICTED FROM THE ALEUTIANS SOUTHWARD ACROSS THE EAST-CENTRAL  
PACIFIC. DOWNSTREAM A STRONG RIDGE IS LIKELY TO BUILD ALONG THE WEST COAST WITH  
AN AMPLIFYING TROUGH OVER EAST-CENTRAL NORTH AMERICA. ABOVE NORMAL 500-HPA  
HEIGHTS ARE PREDICTED OVER ALASKA AND THE WESTERN CONUS. BELOW NORMAL 500-HPA  
HEIGHTS ARE FORECAST FOR THE CENTRAL AND EASTERN CONUS.  
 
BELOW NORMAL TEMPERATURES ARE FAVORED FROM NEAR THE MISSISSIPPI RIVER EASTWARD  
TO THE ATLANTIC COAST, UNDERNEATH THE PREDICTED DEEP TROUGH AND ACCOMPANYING  
WELL BELOW NORMAL HEIGHTS. ABOVE NORMAL HEIGHTS FORECAST OVER THE WESTERN  
CONUS AND SOUTHEASTERLY SURFACE FLOW OVER THE SOUTHWEST CONUS LEAD TO INCREASED  
CHANCES OF ABOVE NORMAL TEMPERATURES THERE. THE PREDICTED ANOMALOUS TROUGH OVER  
THE SOUTHERN ALEUTIANS AND THE NORTH PACIFIC LEADS TO SOUTH-SOUTHWESTERLY FLOW  
NEAR THE SURFACE OVER MUCH OF ALASKA ENHANCES CHANCES OF ABOVE NORMAL  
TEMPERATURES.  
 
EAST OF THE MID-LEVEL TROUGH PREDICTED OVER THE ALEUTIANS, SOUTHWESTERLY FLOW  
AT THE SURFACE INCREASES CHANCES OF ABOVE NORMAL PRECIPITATION OVER MOST OF  
ALASKA. ABOVE NORMAL PRECIPITATION IS FAVORED FROM THE UPPER MISSISSIPPI VALLEY  
EASTWARD ACROSS THE GREAT LAKES AND NORTHERN NEW ENGLAND, DUE TO FRONTAL  
ACTIVITY. BELOW NORMAL PRECIPITATION IS LIKELY FOR MOST OF THE CONUS, WITH HIGH  
PROBABILITIES OF BELOW NORMAL PRECIPITATION FROM NORTHERN CALIFORNIA AND MUCH  
OF THE PACIFIC NORTHWEST TO IDAHO; CONTINUING SOUTHEASTWARD FROM THERE INTO  
UTAH. HIGH PROBABILITIES OF BELOW NORMAL PRECIPITATION ARE ALSO INDICATED  
ACROSS MOST OF THE SOUTHEASTERN QUARTER OF THE CONUS. THESE TWO REGIONS OF  
HIGHER PROBABILITIES FOR BELOW NORMAL PRECIPITATION ARE ATTRIBUTED TO THE  
EXPECTED PRESENCE OF A HIGHLY AMPLIFIED RIDGE OVER THE WEST AND BROAD  
NORTHWESTERLY FLOW DOWNSTREAM OVER MOST OF THE REMAINDER OF THE CONUS.  
 
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, 10% OF TODAY'S OPERATIONAL 0Z GFS CENTERED ON DAY 8, 10% OF TODAY'S  
OPERATIONAL 6Z GFS CENTERED ON DAY 8, 20% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN  
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: FORECAST CONFIDENCE FOR THE 6-10  
DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GENERALLY GOOD AGREEMENT AMONG  
THE PREDICTION TOOLS, BUT OFFSET BY MODERATE SPREAD AMONG THE COMPONENT  
ENSEMBLE MEMBERS. THE TWO AREAS WITH GREATEST SPREAD ARE NORTHERN ALASKA DUE TO  
DIFFERENCES IN PREDICTED AMPLITUDE OF THE RIDGE, AND OVER THE SOUTHWEST,  
ASSOCIATED WITH POTENTIAL UNDERCUTTING OF THE WESTERN RIDGE.  
 
8-14 DAY OUTLOOK FOR DEC 13 - 19 2017  
 
THE 500-HPA PATTERN DURING THE 8-14 DAY PERIOD IS PREDICTED TO BE SIMILAR TO  
THAT OF THE 6-10 DAY PERIOD. THE PATTERN IS PREDICTED TO BE HIGHLY AMPLIFIED  
OVER THE NORTH AMERICAN SECTOR, WITH PERHAPS A SLIGHT WESTWARD SHIFT OF THE  
RIDGE PREDICTED NEAR THE WEST COAST. TROUGHING CENTERED OVER THE OHIO VALLEY IS  
PREDICTED TO CONTINUE. INTRAMODEL SPREAD, ASSESSED VIA THE SPAGHETTI PLOTS, IS  
LOW OVER THE EASTERN CONUS. THE ONLY AREAS OF SUBSTANTIAL UNCERTAINTY ARE OVER  
NORTHERN ALASKA DUE TO DIFFERING PREDICTIONS OF RIDGE AMPLITUDE, AND OVER THE  
SOUTHWEST, ASSOCIATED WITH POTENTIAL UNDERCUTTING OF THE WESTERN RIDGE.  
 
THE TROUGHING OVER THE EASTERN CONUS IS EXPECTED TO SUPPORT ANOMALOUSLY COLD  
AIR FROM THE UPPER AND MIDDLE MISSISSIPPI VALLEY EASTWARD TO THE ATLANTIC  
SEABOARD AS FAR SOUTH AS CENTRAL GEORGIA. ABOVE NORMAL TEMPERATURES ARE FAVORED  
FROM THE HIGH PLAINS WESTWARD TO THE PACIFIC COAST, AND OVER ALASKA. THE 6Z AND  
12Z OPERATIONAL GFS RUNS INDICATE SOME MODERATION IN TEMPERATURES ACROSS THE  
DEEP SOUTH DURING THE SECOND HALF OF THE WEEK-2 PERIOD. IT MAY ALSO BE  
NECESSARY TOMORROW TO INTRODUCE NEAR OR ABOVE NORMAL PRECIPITATION TO THIS SAME  
AREA, AS HINTED AT BY TODAY'S GFS FORECASTS AND POTENTIAL INTRUSION OF MARITIME  
TROPICAL AIR INTO THIS REGION.  
 
STRONG RIDGING OVER THE WESTERN CONUS FAVORS BELOW NORMAL PRECIPITATION FOR  
MOST AREAS WEST OF THE CONTINENTAL DIVIDE; AND FOR APPROXIMATELY THE SOUTHERN  
ONE-HALF OF THE CONUS EAST OF THE DIVIDE IN DRIER NORTHWESTERLY FLOW. THE  
EXCEPTION MAY BE THE GULF COAST REGION, THOUGH AS MENTIONED ABOVE, THIS  
POSSIBILITY WILL BE LOOKED AT IN MORE DETAIL TOMORROW. THE RIDGING IS ALSO  
LIKELY TO STEER STORMS INTO ALASKA. TROUGHING OVER SOUTHEAST CANADA IMPLIES  
STORM ACTIVITY FROM THE NORTHERN PLAINS TO THE NORTHEAST, WHERE NEAR TO ABOVE  
NORMAL PRECIPITATION IS FAVORED, ESPECIALLY DOWN WIND OF THE GREAT LAKES.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 20% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 10% OF TODAY'S OPERATIONAL 0Z GFS CENTERED ON DAY 11, 10% OF TODAY'S  
OPERATIONAL 6Z GFS CENTERED ON DAY 11, 20% 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 IS: FORECAST CONFIDENCE FOR THE  
8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE  
ENSEMBLE MEANS AND LOW TO MODERATE SPREAD AMONG THE ENSEMBLE MEMBERS.  
 
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  
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:  
19601204 - 20041118 - 19711117 - 19821121 - 19691124  
 
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:  
20041120 - 19601204 - 19711116 - 19521119 - 19621116  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 11 - 15 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A B OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA A B E MONTANA A B WYOMING A B  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA A N S DAKOTA A N  
NEBRASKA A N KANSAS A B OKLAHOMA N B  
N TEXAS N B S TEXAS N B W TEXAS A B  
MINNESOTA B A IOWA N B MISSOURI N B  
ARKANSAS N B LOUISIANA B B WISCONSIN B A  
ILLINOIS B B MISSISSIPPI B B MICHIGAN B A  
INDIANA B B OHIO B N KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK B A  
VERMONT B A NEW HAMP B N MAINE B A  
MASS B N CONN B N RHODE IS B N  
PENN B N 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 A N  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 13 - 19 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A B OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO A B NEVADA A B  
W MONTANA A B E MONTANA A A WYOMING A N  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA N A S DAKOTA N A  
NEBRASKA A N KANSAS N B OKLAHOMA N B  
N TEXAS N B S TEXAS N B W TEXAS A B  
MINNESOTA B A IOWA B N MISSOURI B B  
ARKANSAS N B LOUISIANA N B WISCONSIN B N  
ILLINOIS B B MISSISSIPPI N B MICHIGAN B A  
INDIANA B N OHIO B N KENTUCKY B B  
TENNESSEE B B ALABAMA N B NEW YORK B A  
VERMONT B N NEW HAMP B N MAINE B N  
MASS B N CONN B N RHODE IS B N  
PENN B N 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 N B  
FL PNHDL N B FL PENIN N 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 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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