907  
FXUS06 KWBC 201919  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EDT FRI OCTOBER 20 2017  
 
6-10 DAY OUTLOOK FOR OCT 26 - 30 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  
WEST OF ALASKA. DOWNSTREAM A STRONG RIDGE IS PREDICTED OVER THE WESTERN HALF OF  
THE CONUS AND INTO EASTERN ALASKA AND THE ALASKA PANHANDLE. A TROUGH IS  
FORECAST OVER THE EASTERN CONUS. TODAY'S 500-HPA MANUAL BLEND FEATURES POSITIVE  
HEIGHT ANOMALIES OVER MOST OF ALASKA, POSITIVE HEIGHT ANOMALIES OVER THE  
WESTERN THIRD 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 PARTS OF THE WESTERN CONUS, ESPECIALLY FOR SOUTHERN CALIFORNIA  
AND PARTS OF THE SOUTHWEST. THIS RIDGE IS FORECAST TO EXTEND INTO ALASKA,  
FAVORING ABOVE NORMAL TEMPERATURES FOR ALASKA. 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.  
 
AHEAD OF THE TROUGH FORECAST WEST OF ALASKA, STORM SYSTEM ACTIVITY IS EXPECTED  
TO ENHANCE THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION FOR ALASKA. THE WESTERN  
RIDGE IS FORECAST TO PREVENT STORM SYSTEMS FROM COMING INTO THE WESTERN CONUS,  
STRONGLY FAVORING NEAR TO BELOW NORMAL PRECIPITATION OVER MUCH OF THE CONUS.  
HOWEVER, ABOVE NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE GREAT LAKES  
REGION AND NORTHEAST ASSOCIATED WITH A FEW STORM SYSTEMS FORECAST TO DEVELOP  
AHEAD OF THE TROUGH.  
 
TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 40% OF TODAY'S OPERATIONAL 6Z GFS  
CENTERED ON DAY 8, AND 60% 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, FAIRLY  
GOOD AGREEMENT AMONG THE MODELS ON AN AMPLIFIED FLOW PATTERN, AND FAIRLY GOOD  
AGREEMENT AMONG THE TEMPERATURE AND PRECIPITATION TOOLS.  
 
8-14 DAY OUTLOOK FOR OCT 28 - NOV 03, 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.  
TODAY'S DETERMINISTIC GFS VARIES GREATLY BETWEEN CYCLES, SUGGESTING THAT THE  
PATTERN WILL BECOME A LOT MORE PROGRESSIVE DURING THE WEEK-2 PERIOD. THIS ALSO  
GREATLY INCREASES THE UNCERTAINTY, AND WEAKENS THE AVERAGE 500-HPA ANOMALIES  
DURING THE PERIOD. EVEN THE LATEST GFS AND ECMWF ENSEMBLE MEANS ARE COMPLETELY  
OUT OF PHASE OVER THE CONUS, WHICH IS RELATIVELY UNCOMMON FOR TWO ENSEMBLE  
MEANS DURING THIS PERIOD. TODAY'S 500-HPA MANUAL BLEND DEPICTS POSITIVE HEIGHT  
ANOMALIES OVER ALASKA, THE WESTERN HALF OF THE CONUS AND OVER THE NORTHEAST,  
AND NEGATIVE HEIGHT ANOMALIES ELSEWHERE.  
 
THE TEMPERATURE PROBABILITIES FORECAST DURING THE WEEK-2 PERIOD ARE SIMILAR TO  
THE 6-10 DAY PERIOD, EXCEPT PROBABILITIES ARE MUCH LOWER, DUE TO SIGNIFICANTLY  
INCREASED UNCERTAINTY AND A DEAMPLIFICATION OF THE LARGE-SCALE PATTERN.  
 
THE PRECIPITATION PROBABILITIES FORECAST DURING THE WEEK-2 PERIOD ARE SIMILAR  
TO THE 6-10 DAY PERIOD, WITH A FEW EXCEPTIONS. AS THE RIDGE OVER PARTS OF  
ALASKA IS EXPECTED TO BECOME MORE ESTABLISHED DURING THE WEEK-2 PERIOD, THE  
STORM TRACK OVER ALASKA IS FORECAST TO SHIFT NORTHWARD, FAVORING ABOVE NORMAL  
PRECIPITATION FOR MUCH OF ALASKA, ESPECIALLY FARTHER NORTH, AND FAVORING NEAR  
NORMAL PRECIPITATION FOR THE ALEUTIANS, THE SOUTHERN COAST, AND THE PANHANDLE.  
SINCE THE PATTERN OVER THE CONUS IS EXPECTED TO SHIFT A BIT EASTWARD BY THE  
WEEK-2 PERIOD, THE PROBABILITIES OF BELOW NORMAL PRECIPITATION ARE FAVORED A  
BIT FARTHER EAST IN THE EASTERN U.S. A FEW FRONTAL SYSTEMS POSSIBLY DEVELOPING  
OFFSHORE FAVOR ABOVE NORMAL PRECIPITATION FOR PARTS OF THE NORTHEAST. THERE ARE  
INCREASED ODDS OF NEAR TO ABOVE NORMAL PRECIPITATION FOR THE SOUTHERN FLORIDA  
PENINSULA UNDERNEATH MEAN EASTERLY FLOW. PROBABILITIES OF ABOVE NORMAL  
PRECIPITATION ARE ALSO ELEVATED FOR PARTS OF THE GREAT LAKES REGION WITH A FEW  
STORM SYSTEMS EXPECTED THERE.  
 
THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF:  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: WELL BELOW AVERAGE, 1 OUT OF 5,  
DUE TO LARGE SPREAD AMONG THE ENSEMBLE MEMBERS OVER MOST OF THE FORECAST  
DOMAIN, VERY SIGNIFICANT DIFFERENCES BETWEEN THE ENSEMBLE MEANS, AND RELATIVELY  
POOR AGREEMENT AMONG SOME OF 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  
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:  
20011030 - 19751102 - 19531101 - 19541009 - 20050930  
 
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:  
20011030 - 19751101 - 20050929 - 19651015 - 19541009  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 26 - 30 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 N B E MONTANA N N WYOMING N N  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA B N S DAKOTA B B  
NEBRASKA B B KANSAS B B OKLAHOMA B B  
N TEXAS B B S TEXAS B B W TEXAS N B  
MINNESOTA B N IOWA B B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN B N  
ILLINOIS B B MISSISSIPPI B B MICHIGAN B A  
INDIANA B N OHIO B A KENTUCKY B N  
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 A NEW JERSEY A A W VIRGINIA B A  
MARYLAND A A DELAWARE A A VIRGINIA B A  
N CAROLINA B A S CAROLINA B N GEORGIA B B  
FL PNHDL B B FL PENIN B N 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  
 
 
 
8-14 DAY OUTLOOK TABLE  
OUTLOOK FOR OCT 28 - NOV 03, 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 N WYOMING A B  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA N N S DAKOTA N N  
NEBRASKA N B KANSAS N B OKLAHOMA N B  
N TEXAS N B S TEXAS N B W TEXAS A B  
MINNESOTA N N IOWA N B MISSOURI B B  
ARKANSAS B B LOUISIANA B B WISCONSIN N A  
ILLINOIS B B MISSISSIPPI B B MICHIGAN N A  
INDIANA B B OHIO B N KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK A N  
VERMONT A N NEW HAMP A A MAINE A A  
MASS A A CONN A A RHODE IS A A  
PENN N N NEW JERSEY A N W VIRGINIA B N  
MARYLAND N N DELAWARE A N VIRGINIA N N  
N CAROLINA B N S CAROLINA B N GEORGIA B B  
FL PNHDL B N FL PENIN N A AK N SLOPE A A  
AK ALEUTIAN A N AK WESTERN A A AK INT BSN A A  
AK S INT A N AK SO COAST A N AK PNHDL A N  
 
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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