501  
FXUS06 KWBC 181901  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EDT WED OCTOBER 18 2017  
 
6-10 DAY OUTLOOK FOR OCT 24 - 28 2017  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN VERY 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. 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 MOST 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. 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 DEEPENING TROUGH AND COLD  
AIR ADVECTION BEHIND A FRONTAL PASSAGE INCREASE THE LIKELIHOOD OF BELOW NORMAL  
TEMPERATURES FOR PARTS OF THE EASTERN U.S. IN PARTS OF THE NORTHEAST, LARGE  
POSITIVE TEMPERATURE ANOMALIES FORECAST DURING THE FIRST HALF OF THE PERIOD  
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 THE ALEUTIANS, THE SOUTHERN ALASKA COAST, THE ALASKA PANHANDLE, 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 COUNTRY NEAR AND WEST OF THE  
MISSISSIPPI RIVER. A FRONTAL PASSAGE PREDICTED NEAR THE BEGINNING OF THE 6-10  
DAY PERIOD INCREASES THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION FOR PARTS OF  
EASTERN U.S.  
 
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 0Z ECMWF 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 AND FAIRLY GOOD AGREEMENT AMONG THE TEMPERATURE  
AND PRECIPITATION TOOLS.  
 
8-14 DAY OUTLOOK FOR OCT 26 - NOV 01, 2017  
 
DURING THE WEEK-2 PERIOD, THE OVERALL 500-HPA FLOW PATTERN IS EXPECTED SHIFT  
SLIGHTLY EASTWARD, AND BE LESS AMPLIFIED. TODAY'S MODELS SIGNIFICANTLY WEAKEN  
THE EASTERN TROUGH DURING THE WEEK-2 PERIOD, PREDICTING A MORE PROGRESSIVE  
PATTERN ACROSS MUCH OF THE CONUS.  
 
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. PROBABILITIES ARE SOMEWHAT LOWER ACROSS THE COUNTRY DUE TO THE  
INCREASED UNCERTAINTY DURING THE WEEK-2 PERIOD, A MORE PROGRESSIVE PATTERN, AND  
SMALLER FORECAST 500-HPA HEIGHT ANOMALIES. THE TEMPERATURE PROBABILITIES ARE  
ALSO SHIFTED SLIGHTLY EASTWARD, COINCIDING WITH THE EXPECTED EASTWARD SHIFT IN  
THE LARGE-SCALE PATTERN.  
 
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 BEFORE THE WEEK-2 PERIOD BEGINS, EXPANDING THE  
FAVORED NEAR TO BELOW NORMAL PRECIPITATION INTO THE EASTERN U.S. THE EXCEPTION  
TO THIS IS THE FLORIDA PENINSULA, WHERE A FORECAST PERSISTENT SURFACE FRONT  
INCREASES THE CHANCES FOR ABOVE NORMAL PRECIPITATION THERE.  
 
THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 50% OF TODAY'S OPERATIONAL 6Z  
GFS CENTERED ON DAY 11, AND 50% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED  
ON DAY 11  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE  
TO GOOD AGREEMENT AMONG THE MODELS AND FAIRLY GOOD AGREEMENT 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:  
20071030 - 20050928 - 19781029 - 20011030 - 19541009  
 
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:  
20050927 - 19781030 - 20011030 - 20071031 - 19541008  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 24 - 28 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 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 B LOUISIANA B B WISCONSIN N B  
ILLINOIS B B MISSISSIPPI B B MICHIGAN N A  
INDIANA B B OHIO B A KENTUCKY B A  
TENNESSEE B B ALABAMA B N 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 A A NEW JERSEY A A W VIRGINIA B A  
MARYLAND N A DELAWARE A A VIRGINIA B A  
N CAROLINA B A S CAROLINA B 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 A N  
AK S INT A A AK SO COAST A A AK PNHDL A A  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 26 - NOV 01, 2017  
 
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN  
WASHINGTON A N OREGON A N 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 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 B IOWA A B MISSOURI A B  
ARKANSAS N B LOUISIANA N B WISCONSIN A B  
ILLINOIS N B MISSISSIPPI B B MICHIGAN A B  
INDIANA B B OHIO B B KENTUCKY B B  
TENNESSEE B B ALABAMA B B 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 N B NEW JERSEY A N W VIRGINIA B B  
MARYLAND N B DELAWARE N B VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B B FL PENIN B A AK N SLOPE N N  
AK ALEUTIAN B A AK WESTERN B N AK INT BSN A A  
AK S INT N 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