422  
FXUS06 KWBC 042022  
PMDMRD  
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD  
300 PM EST MON DECEMBER 04 2017  
 
6-10 DAY OUTLOOK FOR DEC 10 - 14 2017  
 
TODAY'S ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT ON THE EXPECTED BROAD  
SCALE 500-HPA CIRCULATION PATTERN IN 6-10 DAY PERIOD. A HIGH AMPLITUDE TROUGH  
IS PREDICTED OVER THE ALEUTIANS, EXTENDING TO THE NORTHERN PACIFIC. DOWNSTREAM  
A STRONG RIDGE IS LIKELY TO BUILD ALONG THE WEST COAST WITH AN AMPLIFYING  
TROUGH OVER EAST-CENTRAL NORTH AMERICA. ABOVE NORMAL 500-HPA HEIGHTS ARE  
PREDICTED OVER ALASKA AND THE WESTERN CONUS. BELOW NORMAL 500-HPA HEIGHTS ARE  
FORECAST FOR THE CENTRAL AND EASTERN CONUS.  
 
BELOW NORMAL TEMPERATURES ARE LIKELY FOR THE MISSISSIPPI VALLEY AND SOUTHEAST  
TEXAS, AND THE EASTERN CONUS, UNDERNEATH THE PREDICTED DEEP TROUGH. ABOVE  
NORMAL HEIGHTS FORECAST OVER THE WESTERN CONUS AND SOUTHEASTERLY SURFACE FLOW  
OVER THE SOUTHWEST CONUS LEAD TO INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES  
THERE. THE PREDICTED ANOMALOUS TROUGH OVER THE SOUTHERN ALEUTIANS AND THE NORTH  
PACIFIC ENHANCES CHANCES OF ABOVE NORMAL TEMPERATURES FOR ALASKA SOUTHERLY FLOW  
IS LIKELY IN THE LOWER LEVELS OVER MUCH OF THE STATE.  
 
EAST OF THE UPPER-LEVEL TROUGH PREDICTED OVER THE ALEUTIANS, SOUTHWESTERLY FLOW  
AT THE SURFACE INCREASES CHANCES OF ABOVE NORMAL PRECIPITATION OVER ALASKA AND  
THE ALASKA PANHANDLE. ABOVE NORMAL PRECIPITATION IS FAVORED FOR THE UPPER  
MISSISSIPPI VALLEY, THE WESTERN GREAT LAKES, AND NORTHERN PARTS OF THE  
NORTHEAST, DUE TO FRONTAL ACTIVITY. BELOW NORMAL PRECIPITATION IS LIKELY FOR  
MOST OF THE CONUS, WITH HIGH PROBABILITIES OF BELOW NORMAL PRECIPITATION ACROSS  
NORTHERN CALIFORNIA, THE PACIFIC NORTHWEST, THE MIDDLE AND LOWER MISSISSIPPI  
VALLEYS, SUPPORTED BY THE STRONG ANOMALOUS RIDGE FORECAST ALONG THE WEST COAST  
AND THE NORTHWESTERLY SURFACE FLOW OVER THE SOUTHEASTERN CONUS. THAT PATTERN IS  
CONSISTENT WITH ESTIMATES FROM THE ECMWF AND GEFS REFORECAST TOOLS.  
 
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 20% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 8, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 8, 20% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8, 20% 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: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  
GOOD AGREEMENT AMONG THE PREDICTION TOOLS, OFFSET BY MODERATE SPREAD AMONG THE  
COMPONENT ENSEMBLE MEMBERS.  
 
8-14 DAY OUTLOOK FOR DEC 12 - 18 2017  
 
THE 500-HPA PATTERN DURING THE 8-14 DAY PERIOD IS PREDICTED TO BE SIMILAR TO  
THAT OF THE 6-10 DAY PERIOD. THE PATTERN IS PREDICTED TO BE HIGHLY AMPLIFIED  
OVER THE NORTH AMERICAN SECTOR. ANOMALOUS RIDGING ALONG THE WEST COAST AND  
TROUGHING CENTERED OVER THE OHIO VALLEY IS PREDICTED TO CONTINUE. MODEL  
AGREEMENT ON THAT OVERALL PATTERN IS QUITE HIGH WITH ONLY MINOR DIFFERENCES  
OVER NORTHERN MEXICO IN THE IDEA OF SOME TROUGHING UNDERCUTTING THE RIDGE OUT  
WEST. INTRAMODEL SPREAD, ASSESSED VIA THE SPAGHETTI PLOTS, IS LOW OVER THE  
EASTERN CONUS. THE ONLY AREAS OF SUBSTANTIAL UNCERTAINTY ARE OVER NORTHERN  
ALASKA DUE TO DIFFERING AMPLITUDE OF THE RIDGE, AND OVER THE SOUTHWEST,  
ASSOCIATED WITH POTENTIAL UNDERCUTTING OF THE WESTERN RIDGE.  
 
THE TROUGHING OVER THE EASTERN CONUS IS EXPECTED TO SUPPORT ANOMALOUSLY COLD  
AIR FROM THE GREAT PLAINS TO THE EAST COAST; WHILE ABOVE NORMAL TEMPERATURES  
ARE FAVORED FROM THE GREAT PLAINS TO THE WEST COAST, AND OVER ALASKA. THE  
HIGHEST ODDS FOR BELOW NORMAL TEMPERATURES ARE OVER THE OHIO VALLEY, CENTRAL  
APPALACHIANS AND LOWER GREAT LAKES REGION.  
 
STRONG RIDGING OVER THE WESTERN CONUS FAVORS BELOW NORMAL PRECIPITATION FOR THE  
PACIFIC NORTHWEST, GREAT BASIN, AND SOUTHWEST. THE RIDGING IS ALSO LIKELY TO  
STEER STORMS INTO SOUTHERN ALASKA. TROUGHING OVER SOUTHEAST CANADA IMPLIES  
STORM ACTIVITY FROM THE NORTHERN PLAINS TO THE NORTHEAST, WHERE NEAR TO ABOVE  
NORMAL PRECIPITATION IS FAVORED, ESPECIALLY DOWN WIND OF THE GREAT LAKES. BELOW  
NORMAL PRECIPITATION IS FAVORED FOR THE SOUTHERN GREAT PLAINS, AS ANY FRONTS  
THAT MOVE ACROSS THE REGION ARE LIKELY TO BE MOISTURE STARVED, THOUGH THOSE  
SAME FRONT MAY SETTLED ACROSS FLORIDA, SO UNCERTAINTY IN THE PRECIPITATION  
OUTLOOK IS HIGHER OVER FLORIDA THAN OTHER PLACES IN THE SOUTHEAST.  
 
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 25% OF TODAY'S 0Z GFS  
ENSEMBLE MEAN CENTERED ON DAY 11, 25% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED  
ON DAY 11, 30% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 20%  
OF YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10  
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: MUCH ABOVE AVERAGE, 5 OUT OF 5,  
DUE TO GOOD AGREEMENT AMONG THE ENSEMBLE MEANS AND LOW SPREAD EVEN AMONG THE  
ENSEMBLE MEMBERS.  
 
FORECASTER: MATT ROSENCRANS  
 
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  
DECEMBER 21  
 
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:  
20041117 - 19691123 - 19861216 - 19661123 - 19531115  
 
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:  
19621114 - 19711113 - 20041120 - 19601113 - 19861216  
 
6-10 DAY OUTLOOK TABLE  
OUTLOOK FOR DEC 10 - 14 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 A S DAKOTA A A  
NEBRASKA A N KANSAS A B OKLAHOMA N B  
N TEXAS N B S TEXAS B B W TEXAS A B  
MINNESOTA B A 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 B OHIO B B KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK B N  
VERMONT B N NEW HAMP B N MAINE B N  
MASS B N CONN B N RHODE IS B N  
PENN B B NEW JERSEY B B W VIRGINIA B B  
MARYLAND B B DELAWARE B B VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B B FL PENIN B B AK N SLOPE A A  
AK ALEUTIAN A B 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 DEC 12 - 18 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 A WYOMING A B  
UTAH A B ARIZONA A B COLORADO A B  
NEW MEXICO A B N DAKOTA N A S DAKOTA N A  
NEBRASKA A N KANSAS A B OKLAHOMA N B  
N TEXAS N B S TEXAS A B W TEXAS A B  
MINNESOTA B A 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 N KENTUCKY B B  
TENNESSEE B B ALABAMA B B NEW YORK B N  
VERMONT B N NEW HAMP B N MAINE B N  
MASS B N CONN B N RHODE IS B N  
PENN B N NEW JERSEY B B W VIRGINIA B N  
MARYLAND B B DELAWARE B B VIRGINIA B B  
N CAROLINA B B S CAROLINA B B GEORGIA B B  
FL PNHDL B B FL PENIN B B AK N SLOPE A N  
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  
 
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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