989  
FXUS06 KWBC 171925  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EDT TUE OCTOBER 17 2017  
 
6-10 DAY OUTLOOK FOR OCT 23 - 27 2017  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON AN AMPLIFIED FLOW  
PATTERN OVER MOST OF THE FORECAST DOMAIN. A DEEP, CLOSED 500-HPA TROUGH IS  
FORECAST OVER PARTS OF WESTERN ALASKA, WITH NEGATIVE HEIGHT ANOMALIES EXTENDING  
SOUTHWARD TO NEAR HAWAII. DOWNSTREAM A STRONG RIDGE IS PREDICTED OVER THE  
WESTERN HALF OF THE CONUS. A TROUGH IS FORECAST OVER THE EASTERN HALF OF THE  
CONUS. TODAY'S 500-HPA MANUAL BLEND FEATURES NEGATIVE HEIGHT ANOMALIES OVER ALL  
OF ALASKA, POSITIVE HEIGHT ANOMALIES OVER THE WESTERN HALF OF THE CONUS, AND  
NEGATIVE HEIGHT ANOMALIES OVER THE EASTERN HALF OF THE CONUS.  
 
BELOW NORMAL TEMPERATURES ARE FAVORED FOR PARTS OF WESTERN ALASKA DUE TO A DEEP  
TROUGH PREDICTED OVER PARTS OF WESTERN ALASKA. 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,  
WHERE THE PREDICTED RIDGE IS CENTERED. A FORECAST DEEPENING TROUGH AND A  
FRONTAL PASSAGE INCREASE THE LIKELIHOOD OF BELOW NORMAL TEMPERATURES FOR PARTS  
OF THE SOUTHERN PLAINS, THE SOUTHERN AND CENTRAL MISSISSIPPI VALLEYS, AND THE  
SOUTHEAST. THIS IS IN CONTRAST TO YESTERDAY'S OFFICIAL 6-10 DAY OUTLOOK WHICH  
FAVORED ABOVE NORMAL TEMPERATURES IN THE SOUTHEAST, AS TODAY'S MODELS HAVE  
SIGNIFICANTLY INCREASED THE STRENGTH OF THE TROUGH FORECAST IN THE EASTERN U.S.  
IN PARTS OF THE MID-ATLANTIC AND NORTHEAST, LARGE POSITIVE TEMPERATURE  
ANOMALIES FORECAST IN THE BEGINNING OF THE PERIOD FAVOR ABOVE NORMAL  
TEMPERATURES IN THOSE REGIONS.  
 
STORM SYSTEM ACTIVITY IS FORECAST TO TRAVEL AROUND THE CLOSED LOW OVER PARTS OF  
ALASKA, INCREASING THE LIKELIHOOD FOR ABOVE NORMAL PRECIPITATION FOR THE  
ALEUTIANS, THE SOUTHERN ALASKA COAST, THE ALASKA PANHANDLE, AND EXTREME  
NORTHERN PORTIONS OF THE PACIFIC NORTHWEST. THE WESTERN RIDGE IS FORECAST TO  
STORM SYSTEMS FROM COMING INTO THE WESTERN CONUS, STRONGLY FAVORING BELOW  
NORMAL PRECIPITATION OVER MUCH OF THE WESTERN HALF OF THE CONUS. THOUGH  
YESTERDAY'S OFFICIAL 6-10 DAY OUTLOOK FEATURED ABOVE NORMAL PRECIPITATION FOR  
PARTS OF THE SOUTHERN PLAINS, THE PREDICTED FRONT RESPONSIBLE FOR THIS IS  
FORECAST TO BE EAST OF THE MISSISSIPPI BY TODAY'S MODELS, FAVORING ABOVE NORMAL  
PRECIPITATION EAST OF THE MISSISSIPPI.  
 
TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 50% OF TODAY'S 6Z GFS ENSEMBLE MEAN  
CENTERED ON DAY 8, AND 50% OF TODAY'S OPERATIONAL 12Z GFS CENTERED ON DAY 8  
 
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO GOOD  
AGREEMENT AMONG THE MODELS, OFFSET BY SOME LARGE-SCALE DIFFERENCES AMONG THE  
TEMPERATURE AND PRECIPITATION TOOLS.  
 
8-14 DAY OUTLOOK FOR OCT 25 - 31 2017  
 
DURING THE WEEK-2 PERIOD, THE OVERALL 500-HPA FLOW PATTERN IS EXPECTED TO  
RETROGRADE SLIGHTLY, AND BE SLIGHTLY LESS AMPLIFIED, WHICH IS EXPECTED GIVEN  
THE INCREASED ENSEMBLE SPREAD REDUCING THE AMPLITUDE OF THE ENSEMBLE MEANS.  
 
THE TEMPERATURE PROBABILITIES FORECAST DURING THE 6-10 DAY PERIOD ARE VERY  
SIMILAR TO THOSE FORECAST DURING THE WEEK-2 PERIOD, WITH A COUPLE OF  
EXCEPTIONS. SOME RIDGING IS EXPECTED TO BUILD WESTWARD INTO EASTERN PORTIONS OF  
ALASKA, FAVORING ABOVE NORMAL TEMPERATURES THERE. AS THE EASTERN TROUGH IS  
FORECAST TO BECOME MORE ESTABLISHED DURING THE WEEK-2 PERIOD, THE FAVORED AREA  
OF BELOW NORMAL TEMPERATURES IS LARGER DURING THE WEEK-2 PERIOD.  
 
THE PRECIPITATION PROBABILITIES FORECAST DURING THE 6-10 DAY PERIOD ARE SIMILAR  
TO THE WEEK-2 PERIOD, EXCEPT THAT THE FRONTAL SYSTEM FORECAST TO FAVOR ABOVE  
NORMAL PRECIPITATION IN THE EASTERN U.S. DURING THE 6-10 DAY PERIOD IS  
PREDICTED TO MOVE OFFSHORE DURING THE BEGINNING OF THE WEEK-2 PERIOD, LEAVING  
ONLY THE NORTHEAST IN THE REGION OF FAVORED ABOVE NORMAL PRECIPITATION.  
 
THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 60% OF TODAY'S 0Z GFS ENSEMBLE  
MEAN CENTERED ON DAY 11, AND 40% OF TODAY'S OPERATIONAL 0Z GFS CENTERED ON DAY  
11  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: AVERAGE, 3 OUT OF 5, DUE TO  
GOOD AGREEMENT AMONG THE MODELS, OFFSET BY SOME LARGE-SCALE DIFFERENCES AMONG  
THE TEMPERATURE AND PRECIPITATION TOOLS.  
 
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  
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:  
20071031 - 19891012 - 20050927 - 19781028 - 19640928  
 
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:  
20071030 - 20050927 - 19581005 - 19781029 - 19891012  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 23 - 27 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 N B  
N TEXAS B B S TEXAS B B W TEXAS A B  
MINNESOTA N B IOWA N B MISSOURI B B  
ARKANSAS B N LOUISIANA B N WISCONSIN N B  
ILLINOIS B N MISSISSIPPI B N MICHIGAN N A  
INDIANA N A OHIO N A KENTUCKY B A  
TENNESSEE B A ALABAMA B 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 N A NEW JERSEY A A W VIRGINIA N A  
MARYLAND A A DELAWARE A A VIRGINIA N A  
N CAROLINA N A S CAROLINA N A GEORGIA B A  
FL PNHDL B A FL PENIN B A AK N SLOPE N N  
AK ALEUTIAN B A AK WESTERN B N AK INT BSN N N  
AK S INT N A AK SO COAST N A AK PNHDL N A  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 25 - 31 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A N OREGON A B NRN CALIF A B  
SRN CALIF A B IDAHO A B 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 B B  
N TEXAS B B S TEXAS B B W TEXAS A B  
MINNESOTA N B IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN N B  
ILLINOIS B B MISSISSIPPI B B MICHIGAN N 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 N N NEW JERSEY A A W VIRGINIA B N  
MARYLAND N N DELAWARE A N VIRGINIA B N  
N CAROLINA B N S CAROLINA B N GEORGIA B B  
FL PNHDL B B FL PENIN B N AK N SLOPE N A  
AK ALEUTIAN N A AK WESTERN N N 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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