541  
FXUS06 KWBC 191916  
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 19 2017  
 
6-10 DAY OUTLOOK FOR OCT 25 - 29 2017  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE GENERALLY IN GOOD AGREEMENT ON AN AMPLIFIED  
FLOW PATTERN OVER MOST OF THE FORECAST DOMAIN. A 500-HPA TROUGH IS FORECAST  
OVER WESTERN ALASKA. DOWNSTREAM A STRONG RIDGE IS PREDICTED OVER THE WESTERN  
HALF OF THE CONUS. A TROUGH IS FORECAST OVER THE EASTERN CONUS. TODAY'S 500-HPA  
MANUAL BLEND FEATURES NEGATIVE HEIGHT ANOMALIES OVER MOST OF ALASKA (WITH THE  
EXCEPTION OF THE PANHANDLE), POSITIVE HEIGHT ANOMALIES OVER THE WESTERN HALF OF  
THE CONUS AS WELL AS PARTS OF THE NORTHEASTERN CONUS, AND NEGATIVE HEIGHT  
ANOMALIES OVER THE REMAINDER OF THE CONUS.  
 
A STRONG RIDGE PREDICTED OVER THE WESTERN CONUS HIGHLY FAVORS ABOVE NORMAL  
TEMPERATURES FOR THE WESTERN HALF OF THE CONUS, ESPECIALLY FOR SOUTHERN  
CALIFORNIA AND PARTS OF THE SOUTHWEST. THIS RIDGE IS FORECAST TO EXTEND INTO  
PARTS OF EASTERN ALASKA, FAVORING ABOVE NORMAL TEMPERATURES FOR PARTS OF  
EASTERN ALASKA AND THE ALASKA PANHANDLE. A FORECAST TROUGH AND COLD AIR  
ADVECTION BEHIND FRONTAL PASSAGES INCREASE THE LIKELIHOOD OF BELOW NORMAL  
TEMPERATURES FOR MUCH OF THE EASTERN U.S. HOWEVER, IN PARTS OF THE NORTHEAST,  
POSITIVE HEIGHT ANOMALIES AHEAD OF THE TROUGH AXIS FAVOR ABOVE NORMAL  
TEMPERATURES THERE.  
 
STORM SYSTEM ACTIVITY IS FORECAST TO TRAVEL AROUND THE CLOSED LOW, CENTERED  
OVER PARTS OF ALASKA, INCREASING THE LIKELIHOOD FOR ABOVE NORMAL PRECIPITATION  
FOR MUCH OF ALASKA AND EXTREME NORTHERN PORTIONS OF THE PACIFIC NORTHWEST. THE  
WESTERN RIDGE IS FORECAST TO PREVENT STORM SYSTEMS FROM COMING INTO THE WESTERN  
CONUS, STRONGLY FAVORING BELOW NORMAL PRECIPITATION OVER MUCH OF THE CONUS.  
HOWEVER, ABOVE NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE NORTHEAST AHEAD  
OF THE TROUGH OVER THE EASTERN CONUS.  
 
TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 20% OF TODAY'S OPERATIONAL 6Z GFS  
CENTERED ON DAY 8, AND 80% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY  
8  
 
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
GOOD AGREEMENT AMONG THE MODELS ON AN AMPLIFIED FLOW PATTERN.  
 
8-14 DAY OUTLOOK FOR OCT 27 - NOV 02, 2017  
 
DURING THE WEEK-2 PERIOD, MODEL AGREEMENT IS RELATIVELY POOR AND THERE IS LARGE  
SPREAD AMONG THE ENSEMBLE MEMBERS OVER MUCH OF THE OF THE FORECAST DOMAIN. AT  
THE BEGINNING OF THE PERIOD, A TROUGH IS EXPECTED OVER THE EASTERN U.S. WHILE  
RIDGING IS FORECAST OVER THE WESTERN CONUS. THEREAFTER, THE ENSEMBLE MEAN  
SOLUTIONS DE-AMPLIFY THE OVERALL PATTERN DUE, IN PART, TO INCREASED UNCERTAINTY  
AND SPREAD AMONG THE COMPONENT ENSEMBLE MEMBERS. THE ENSEMBLE MEAN SOLUTIONS  
GENERALLY AGREE IN FORECASTING A MEAN TROUGH AND ASSOCIATED BELOW NORMAL  
HEIGHTS OVER MUCH OF ALASKA. HOWEVER, MODEL SPREAD IS HIGH AND CONSISTENCY  
AMONG THE DETERMINISTIC GFS RUNS IS POOR FOR THE REGION. DUE TO LARGE MODEL  
UNCERTAINTIES, TODAY'S WEEK-2 500-HPA BLEND RELIES HEAVILY ON THE ENSEMBLE MEAN  
SOLUTIONS.  
 
BELOW NORMAL TEMPERATURES ARE FAVORED FOR THE SOUTHEASTERN CONUS DUE TO A  
TROUGH EXPECTED OVER THE EASTERN CONUS (PARTICULARLY EARLY IN THE PERIOD).  
ABOVE NORMAL TEMPERATURE PROBABILITIES ARE ENHANCED FOR PARTS OF THE  
NORTHEASTERN CONUS AHEAD OF THE EXPECTED TROUGH AXIS. ABOVE NORMAL HEIGHTS LEAD  
TO ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR MOST OF THE WESTERN  
AND NORTH-CENTRAL CONUS. THERE ARE INCREASED ODDS OF ABOVE NORMAL TEMPERATURES  
FOR PARTS OF EASTERN MAINLAND ALASKA AND THE ALASKA PANHANDLE AHEAD OF A  
TROUGH. BELOW NORMAL TEMPERATURES ARE FAVORED BEHIND THE TROUGH AXIS FOR PARTS  
OF SOUTHWESTERN ALASKA.  
 
MEAN SURFACE HIGH PRESSURE LEADS TO ENHANCED PROBABILITIES FOR BELOW NORMAL  
PRECIPITATION OVER MUCH OF THE CONUS. HOWEVER, NEAR TO ABOVE NORMAL  
PRECIPITATION IS FAVORED FOR PARTS OF THE GREAT LAKES AND NORTHEAST IN  
ASSOCIATION WITH A MEAN 500-HPA TROUGH. THERE ARE INCREASED ODDS OF NEAR TO  
ABOVE NORMAL PRECIPITATION FOR THE SOUTHERN FLORIDA PENINSULA UNDERNEATH MEAN  
EASTERLY FLOW. PROBABILITIES OF NEAR TO ABOVE NORMAL PRECIPITATION ARE ALSO  
ELEVATED FOR PARTS OF THE NORTHWESTERN CONUS AS THE RIDGE OVER THE WESTERN  
CONUS POTENTIALLY DE-AMPLIFIES DURING THE WEEK-2 PERIOD. THE TROUGH FORECAST  
OVER ALASKA LEADS TO INCREASED ODDS OF ABOVE NORMAL PRECIPITATION FOR MUCH OF  
THE STATE.  
 
THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 30% OF YESTERDAY'S OPERATIONAL  
18Z GFS CENTERED ON DAY 10, AND 70% OF YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN  
CENTERED ON DAY 10  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: BELOW AVERAGE, 2 OUT OF 5, DUE  
TO LARGE SPREAD AMONG THE ENSEMBLE MEMBERS OVER MOST OF THE FORECAST DOMAIN.  
 
FORECASTER: MIKE C  
 
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  
NOVEMBER 16  
 
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:  
20050929 - 20011030 - 19531101 - 19751102 - 19640929  
 
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:  
20050928 - 20011030 - 19751101 - 19991007 - 19541008  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 25 - 29 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A B OREGON A B NRN CALIF A B  
SRN CALIF A N 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 B S DAKOTA A B  
NEBRASKA A B KANSAS A B OKLAHOMA B B  
N TEXAS B B S TEXAS B B W TEXAS A B  
MINNESOTA A B IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN B B  
ILLINOIS B B MISSISSIPPI B B MICHIGAN B N  
INDIANA B B OHIO B N KENTUCKY B B  
TENNESSEE B B ALABAMA B B 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 B N NEW JERSEY A A W VIRGINIA B N  
MARYLAND B N DELAWARE B N VIRGINIA B N  
N CAROLINA B N S CAROLINA B B GEORGIA B B  
FL PNHDL B B FL PENIN B N AK N SLOPE A A  
AK ALEUTIAN N A AK WESTERN N 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 OCT 27 - NOV 02, 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON N N OREGON A N NRN CALIF A B  
SRN CALIF A B IDAHO A N NEVADA A B  
W MONTANA A N E MONTANA A B WYOMING A B  
UTAH A B ARIZONA A B 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 N B S TEXAS N B W TEXAS A B  
MINNESOTA A B IOWA A B MISSOURI A B  
ARKANSAS N B LOUISIANA B B WISCONSIN A B  
ILLINOIS A B MISSISSIPPI B B MICHIGAN A N  
INDIANA N B OHIO N B KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK A N  
VERMONT A N NEW HAMP A N MAINE A A  
MASS A N CONN A B RHODE IS A N  
PENN A B NEW JERSEY A B W VIRGINIA N B  
MARYLAND N B DELAWARE A B VIRGINIA N B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B B FL PENIN B N AK N SLOPE N A  
AK ALEUTIAN N N AK WESTERN N A AK INT BSN N A  
AK S INT N A AK SO COAST N 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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