815  
FXUS06 KWBC 121903  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EDT THU OCTOBER 12 2017  
 
6-10 DAY OUTLOOK FOR OCT 18 - 22 2017  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE 500-HPA FLOW  
PATTERN OVER THE FORECAST DOMAIN. A TROUGH IS FORECAST OVER ALASKA EXTENDING  
SOUTHEASTWARD ALONG THE WEST COAST, WHILE AN ANOMALOUS RIDGE IS EXPECTED OVER  
THE EASTERN CONUS. TODAY'S 500-HPA HEIGHT BLEND CHART DEPICTS BELOW NORMAL  
HEIGHTS OVER MOST OF THE NORTHWESTERN CONUS AND ALASKA, WHILE NEAR TO ABOVE  
NORMAL HEIGHTS ARE FORECAST ACROSS THE REMAINDER OF THE CONUS. THE ENSEMBLE  
SPAGHETTI DIAGRAMS INDICATE SMALL TO MODERATE SPREAD ACROSS THE MAJORITY OF THE  
FORECAST DOMAIN. THE GREATEST WEIGHT FOR THE BLENDED HEIGHT FORECAST WAS GIVEN  
TO TODAY'S 00Z ECMWF ENSEMBLE MEAN BASED ON CONSIDERATIONS OF RECENT SKILL.  
 
THE FORECAST TROUGH NEAR THE PACIFIC NORTHWEST TILTS THE ODDS TO NEAR OR BELOW  
NORMAL TEMPERATURES FOR MOST OF THE NORTHWESTERN CONUS. ABOVE NORMAL  
TEMPERATURES ARE FAVORED FOR MUCH OF THE REMAINDER OF THE CONUS UNDERNEATH  
ABOVE NORMAL HEIGHTS. THE PREDICTED TROUGH AND BELOW NORMAL HEIGHTS OVER ALASKA  
INCREASE PROBABILITIES OF BELOW NORMAL TEMPERATURES FOR MUCH OF THE STATE.  
 
THE TROUGH ALONG THE WEST COAST AND ENHANCED ONSHORE FLOW LEAD TO INCREASED  
CHANCES OF ABOVE NORMAL PRECIPITATION FOR THE SOUTHERN ALASKA PANHANDLE, AND  
MUCH OF THE WESTERN CONUS, WEST OF THE CONTINENTAL DIVIDE. BELOW NORMAL  
PRECIPITATION IS FAVORED FOR PARTS OF THE SOUTHWEST, THE GREAT PLAINS, THE  
LOWER MISSISSIPPI VALLEY, THE TENNESSEE VALLEY, THE OHIO VALLEY, THE LOWER  
GREAT LAKES, THE MIDDLE ATLANTIC, AND THE NORTHEASTERN CONUS, UNDERNEATH ABOVE  
NORMAL HEIGHTS. ABOVE MEDIAN PRECIPITATION IS FAVORED FOR PORTIONS OF THE UPPER  
MISSISSIPPI VALLEY, UPPER GREAT LAKES, AND FLORIDA, WHICH IS CONSISTENT WITH  
PRECIPITATION ESTIMATES FROM THE GEFS ENSEMBLE MEMBERS. THE PREDICTED MEAN  
NORTHEASTERLY FLOW OVER MUCH OF ALASKA ELEVATES THE PROBABILITIES OF BELOW  
NORMAL PRECIPITATION FOR PARTS OF MAINLAND ALASKA AND THE ALEUTIANS.  
 
TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS ENSEMBLE MEAN  
CENTERED ON DAY 8, 10% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 8, 10%  
OF TODAY'S GFS SUPERENSEMBLE 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,  
40% 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: AVERAGE, 3 OUT OF 5, DUE TO GOOD  
AGREEMENT AMONG ENSEMBLE MEANS, OFFSET BY CONTINUING DISAGREEMENT BETWEEN  
PRECIPITATION TOOLS OVER THE CENTRAL AND EASTERN CONUS.  
 
8-14 DAY OUTLOOK FOR OCT 20 - 26 2017  
 
DURING THE WEEK-2 PERIOD, THE ENSEMBLE MEAN SOLUTIONS MAINTAIN A TROUGH OVER  
ALASKA AND INDICATE A LONGWAVE TROUGH SHIFTING EAST SOMEWHERE INTO THE CONUS.  
HOWEVER, ENSEMBLE MEANS DIFFER ON THE LOCATION OF THIS UPPER-LEVEL TROUGH.  
LARGE SPREAD EXITS AMONG THE 0Z ECMWF ENSEMBLE MEMBERS, ESPECIALLY ACROSS THE  
CONUS. TODAY'S 500-HPA HEIGHT BLEND INDICATES BELOW NORMAL HEIGHTS OVER ALASKA,  
WHILE ABOVE NORMAL HEIGHTS ARE FORECAST OVER MOST OF THE CONUS. TODAY'S WEEK-2  
MANUAL 500-HPA HEIGHT BLEND IS WEIGHTED MOST HEAVILY TOWARD THE ENSEMBLE MEAN  
SOLUTION FROM THE 0Z ECMWF DUE TO BETTER SKILL OVER THE PAST 60 DAYS.  
 
THERE ARE INCREASED ODDS FOR BELOW NORMAL TEMPERATURES FOR ALASKA DUE TO A  
PREDICTED TROUGH AND BELOW NORMAL HEIGHTS. ENHANCED PRECIPITATION OVER THE  
NORTHWESTERN CONUS TILTS THE ODDS TO NEAR OR BELOW NORMAL TEMPERATURES OVER THE  
REGION. ABOVE NORMAL TEMPERATURES ARE GENERALLY FAVORED FOR MUCH OF THE  
REMAINDER OF THE CONUS UNDERNEATH PREDICTED ABOVE NORMAL HEIGHTS.  
 
ENHANCED ONSHORE FLOW AT LEAST EARLY IN THE PERIOD FAVORS ABOVE NORMAL  
PRECIPITATION FOR THE NORTHWESTERN CONUS. BELOW NORMAL PRECIPITATION IS FAVORED  
FOR PARTS OF THE SOUTHWEST, THE CENTRAL AND SOUTHERN ROCKIES, AND THE HIGH  
PLAINS, ASSOCIATED WITH ABOVE NORMAL 500-HPA HEIGHTS. THERE ARE INCREASED ODDS  
FOR ABOVE NORMAL PRECIPITATION FOR THE EASTERN CONUS, CONSISTENT WITH  
CALIBRATED PRECIPITATION FORECAST ESTIMATES FROM THE GEFS ENSEMBLE MEMBERS AND  
AN EXPECTED FRONTAL PASSAGE. A TROUGH OVER ALASKA ENHANCES PROBABILITIES FOR  
ABOVE NORMAL PRECIPITATION OVER EASTERN ALASKA, WHILE ENHANCED PROBABILITIES  
FOR BELOW NORMAL PRECIPITATION ARE INDICATED FOR WESTERN ALASKA UNDERNEATH MEAN  
EASTERLY FLOW.  
 
THE OFFICIAL 8-14 DAY HEIGHT PROG 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, 10% OF TODAY'S GFS SUPERENSEMBLE 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  
FAIR MODEL AGREEMENT, OFFSET BY POOR AGREEMENT AMONG PRECIPITATION TOOLS ALONG  
AND EAST OF THE ROCKIES.  
 
FORECASTER: LUKE H  
 
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  
OCTOBER 19  
 
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:  
19911023 - 19610925 - 20050923 - 19710923 - 19561024  
 
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:  
20050923 - 19710926 - 19911023 - 19831003 - 19561024  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 18 - 22 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B A OREGON B A NRN CALIF B A  
SRN CALIF N N IDAHO B A NEVADA B A  
W MONTANA B A E MONTANA N N WYOMING N A  
UTAH N A ARIZONA A N COLORADO A B  
NEW MEXICO A B N DAKOTA A B S DAKOTA A B  
NEBRASKA A B KANSAS A B OKLAHOMA A B  
N TEXAS A B S TEXAS A B W TEXAS A B  
MINNESOTA A N IOWA A N MISSOURI A N  
ARKANSAS A B LOUISIANA A N WISCONSIN A A  
ILLINOIS A A MISSISSIPPI A B MICHIGAN A N  
INDIANA A B OHIO A B KENTUCKY A B  
TENNESSEE A B ALABAMA A B NEW YORK A B  
VERMONT A B NEW HAMP A B MAINE A B  
MASS A B CONN A B RHODE IS A B  
PENN A B NEW JERSEY A B W VIRGINIA A B  
MARYLAND A B DELAWARE A B VIRGINIA A B  
N CAROLINA A B S CAROLINA A B GEORGIA A N  
FL PNHDL A N FL PENIN A A AK N SLOPE B N  
AK ALEUTIAN B B AK WESTERN B B AK INT BSN B N  
AK S INT B B AK SO COAST B B AK PNHDL B N  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 20 - 26 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON B A OREGON N A NRN CALIF A N  
SRN CALIF A N IDAHO B A NEVADA N N  
W MONTANA B A E MONTANA N N WYOMING N A  
UTAH N N ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA A N S DAKOTA A N  
NEBRASKA A B KANSAS A N OKLAHOMA A N  
N TEXAS A N S TEXAS A N W TEXAS A B  
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 A NEW YORK A N  
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 A DELAWARE A N 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 B N  
AK ALEUTIAN B N AK WESTERN B B AK INT BSN B N  
AK S INT B A AK SO COAST B N AK PNHDL B 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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