6-10 Day Narrative

811 
FXUS06 KWBC 161909
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 16 2018
6-10 DAY OUTLOOK FOR OCT 22 - 26 2018
THE ENSEMBLE MEANS AND THEIR DETERMINISTIC MODEL RUNS REMAIN CONSISTENT THAT AN 
AMPLIFIED UPPER-LEVEL TROUGH SHIFTS EAST TOWARDS THE WEST COAST DURING LATE 
OCTOBER. DOWNSTREAM, A RIDGE (TROUGH) IS ALSO FORECAST TO PROGRESS EAST OVER 
THE CENTRAL (EASTERN) CONUS. THE 6Z GFS AND 0Z ECMWF ENSEMBLE MEANS ARE IN GOOD 
AGREEMENT THAT A HIGHLY ANOMALOUS 500-HPA RIDGE DEVELOPS TO THE SOUTHEAST OF 
GREENLAND. THESE ENSEMBLE MEANS INDICATE A 500-HPA HEIGHT ANOMALY CENTER OF 
+300 METERS WITH THIS RIDGE. FOR THE SECOND CONSECUTIVE DAY, THE DETERMINISTIC 
6Z GFS AND 0Z ECMWF MODEL RUNS ARE INCLUDED IN CREATING THE 500-HPA BLEND, 
GIVEN THEIR GOOD AGREEMENT WITH THEIR RESPECTIVE ENSEMBLE MEANS. 
LARGE NEGATIVE TEMPERATURE ANOMALIES (AROUND -10 DEGREES F) ON DAYS 6 AND 7 
ACROSS THE EASTERN CONUS CONTINUE TO INCREASE CHANCES THAT TEMPERATURES WILL 
AVERAGE BELOW NORMAL DURING THIS 5-DAY PERIOD. A SHORTWAVE TROUGH IN THE 
SOUTHERN STREAM AND LIKELIHOOD FOR WIDESPREAD RAINFALL FAVOR BELOW NORMAL 
TEMPERATURES ACROSS MUCH OF TEXAS AND THE LOWER MISSISSIPPI VALLEY. AN INCREASE 
IN PACIFIC FLOW INCREASES CHANCES FOR ABOVE NORMAL TEMPERATURES ACROSS THE 
WESTERN CONUS ALONG WITH THE NORTHERN AND CENTRAL GREAT PLAINS.
ENHANCED ODDS FOR ABOVE NORMAL PRECIPITATION FORECAST ACROSS THE SOUTHWESTERN 
CONUS ARE DUE TO A SHORTWAVE TROUGH IN THE SOUTHERN STREAM. THIS SHORTWAVE 
TROUGH IS FORECAST TO CAUSE SURFACE CYCLOGENESIS IN THE WESTERN GULF OF MEXICO 
BY DAY 8. DURING THIS 5-DAY PERIOD, THE 6Z GFS AND 0Z ECMWF ENSEMBLE MEANS 
INDICATE A WIDESPREAD AREA OF MORE THAN 1 INCH OF PRECIPITATION FROM TEXAS EAST 
TO THE LOWER MISSISSIPPI VALLEY AND ALONG THE GULF COAST. THEREFORE, RELATIVELY 
HIGH PROBABILITIES FOR ABOVE NORMAL PRECIPITATION COINCIDE WITH THIS > 1 INCH 
AREA. THE DETERMINISTIC 0Z ECMWF MODEL FEATURES 2 TO 4 INCHES (LOCALLY MORE) OF 
RAINFALL ALONG THE TEXAS GULF COAST, SUPPORTING A GREATER THAN 70 PERCENT 
CHANCE OF ABOVE NORMAL PRECIPITATION. BELOW-NORMAL PRECIPITATION IS FAVORED 
ACROSS THE MIDWEST DUE TO RIDGING ALOFT, WHILE THE ONSET OF PACIFIC FLOW 
INCREASES CHANCES FOR ABOVE NORMAL PRECIPITATION ACROSS THE PACIFIC NORTHWEST 
AND NORTHERN CALIFORNIA.
THE MODEL SOLUTIONS DEPICT A LARGE SURFACE CYCLONE CENTERED SOUTH OF THE KENAI 
PENINSULA OF ALASKA. SOUTHERLY SURFACE FLOW, ASSOCIATED WITH THIS LOW PRESSURE 
SYSTEM, FAVORS ABOVE NORMAL TEMPERATURES ACROSS ALASKA AND ABOVE NORMAL 
PRECIPITATION ACROSS SOUTHEAST MAINLAND ALASKA AND THE ALASKA PANHANDLE. BEHIND 
THIS LOW PRESSURE SYSTEM, AN INCREASED CHANCE FOR BELOW NORMAL PRECIPITATION IS 
FORECAST ACROSS THE ALEUTIANS AND SOUTHWEST MAINLAND ALASKA.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 30% OF TODAY'S 6Z GFS 
ENSEMBLE MEAN CENTERED ON DAY 8, 20% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON 
DAY 8, 30% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 20% OF 
TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8 
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO GOOD 
AGREEMENT BETWEEN THE GFS AND ECMWF ENSEMBLE MEANS AND THEIR DETERMINISTIC 
MODEL RUNS IN AN AMPLIFIED LONGWAVE PATTERN. HOWEVER, FORECAST CONFIDENCE IS 
REDUCED DUE TO UNCERTAINTY ON THE TRACKS OF PREDICTED LOW PRESSURE SYSTEMS OVER 
THE GULF OF MEXICO AND NEAR THE EAST COAST. 
8-14 DAY OUTLOOK FOR OCT 24 - 30 2018 
THE STRENGTHENING RIDGE OVER THE NORTH ATLANTIC COUPLED WITH BELOW NORMAL 
HEIGHTS AT 500-HPA ACROSS THE EASTERN TROPICAL ATLANTIC IS FORECAST TO RESULT 
IN A NEGATIVE NORTH ATLANTIC OSCILLATION (NAO) INDEX LATER IN WEEK-2. THIS 
EVOLVING LONGWAVE PATTERN IS LIKELY TO MAINTAIN BELOW NORMAL TEMPERATURES 
ACROSS MUCH OF THE EASTERN CONUS DURING WEEK-2. WIDESPREAD PRECIPITATION, 
ASSOCIATED WITH A LOW PRESSURE SYSTEM EARLY IN WEEK-2, TILTS THE ODDS TOWARDS 
BELOW NORMAL TEMPERATURES ACROSS THE WESTERN GULF COAST. ENHANCED PACIFIC FLOW 
FAVORS ABOVE NORMAL TEMPERATURES ACROSS THE WESTERN AND NORTH-CENTRAL CONUS. 
INCREASED CHANCES FOR ABOVE NORMAL TEMPERATURES ACROSS ALASKA ARE BASED ON: 
PREDICTED SOUTHERLY SURFACE FLOW, LACK OF SNOW COVER IN SOUTHEAST MAINLAND 
ALASKA, AND ABOVE NORMAL SEA SURFACE TEMPERATURES CURRENTLY OBSERVED IN THE 
BERING SEA.
ABOVE NORMAL PRECIPITATION IS LIKELY TO ACCOMPANY THE LOW PRESSURE SYSTEM THAT 
IS FORECAST TO TRACK ACROSS THE NORTHERN GULF OF MEXICO EARLY IN WEEK-2. 
THEREFORE, THE HIGHEST PROBABILITIES FOR ABOVE NORMAL PRECIPITATION ARE 
FORECAST FROM SOUTHEAST TEXAS EAST TO THE FLORIDA PANHANDLE. TROPICAL STORM 
TARA IS CURRENTLY LOCATED NEAR THE SOUTHWEST COAST OF MEXICO AND A SECOND 
TROPICAL CYCLONE IS LIKELY TO FORM IN THE EAST PACIFIC PRIOR TO WEEK-2. DEEP 
MOISTURE ASSOCIATED WITH THESE TROPICAL CYCLONES MAY SPREAD NORTH AND INTERACT 
WITH THE SHORTWAVE TROUGH IN THE SOUTHERN STREAM, FURTHER ENHANCING RAINFALL 
AMOUNTS ACROSS THE SOUTHERN TIER OF THE CONUS.
THE DETERMINISTIC 6Z GFS AND 0Z ECMWF MODELS FEATURE A STRENGTHENING LOW 
PRESSURE SYSTEM NEAR COASTAL NEW ENGLAND ON DAY 8. ITS PROXIMITY TO THE EAST 
COAST IS UNCERTAIN, BUT THE STRENGTHENING RIDGE DOWNSTREAM OVER THE NORTH 
ATLANTIC SUPPORTS THIS LOW PRESSURE SYSTEM. ABOVE-NORMAL PRECIPITATION, ALBEIT 
WITH LOW PROBABILITIES, IS FORECAST ACROSS THE PACIFIC NORTHWEST, NORTHERN 
ROCKIES, AND MUCH OF THE CENTRAL U.S. GIVEN ENHANCED PACIFIC FLOW. BASED ON THE 
PREDICTED STORM TRACK ACROSS THE NORTH PACIFIC, BELOW NORMAL PRECIPITATION IS 
FAVORED FOR A MAJORITY OF CALIFORNIA AND THE GREAT BASIN. NEAR NORMAL 
PRECIPITATION IS MOST LIKELY ACROSS SOUTHEAST MAINLAND ALASKA AND THE ALASKA 
PANHANDLE AS A WET START TO WEEK-2 BECOMES INCREASINGLY DRIER AS THE STORM 
TRACK SHIFTS SOUTH FROM ALASKA.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 50% OF TODAY'S 6Z GFS 
ENSEMBLE MEAN 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: AVERAGE, 3 OUT OF 5, DUE TO GOOD 
AGREEMENT BETWEEN THE GFS AND ECMWF ENSEMBLE MEANS OFFSET BY UNCERTAINTY ON THE 
TRACK OF A LOW PRESSURE SYSTEM THAT IS LIKELY TO DEVELOP ACROSS THE GULF OF 
MEXICO AND THE POTENTIAL FOR A STRONG LOW PRESSURE SYSTEM NEAR COASTAL NEW 
ENGLAND. 
FORECASTER: BRAD PUGH
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 18.
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: 
19861009 - 19511030 - 20011004 - 19811019 - 19541028
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: 
19861010 - 19511029 - 19811018 - 19541028 - 19861005
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 22 - 26 2018
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN   
WASHINGTON  A    A     OREGON      A    A     NRN CALIF   A    A     
SRN CALIF   A    N     IDAHO       A    A     NEVADA      A    A     
W MONTANA   A    A     E MONTANA   A    N     WYOMING     A    A     
UTAH        A    A     ARIZONA     A    A     COLORADO    A    A     
NEW MEXICO  A    A     N DAKOTA    A    B     S DAKOTA    A    B     
NEBRASKA    A    A     KANSAS      A    A     OKLAHOMA    B    A     
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A     
MINNESOTA   A    B     IOWA        B    B     MISSOURI    B    B     
ARKANSAS    B    A     LOUISIANA   B    A     WISCONSIN   B    B     
ILLINOIS    B    B     MISSISSIPPI B    A     MICHIGAN    B    B     
INDIANA     B    B     OHIO        B    B     KENTUCKY    B    B     
TENNESSEE   B    B     ALABAMA     B    A     NEW YORK    B    B     
VERMONT     B    B     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    N     GEORGIA     B    A     
FL PNHDL    N    A     FL PENIN    A    A     AK N SLOPE  A    A     
AK ALEUTIAN A    N     AK WESTERN  A    N     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 24 - 30 2018
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN   
WASHINGTON  A    A     OREGON      A    A     NRN CALIF   A    B     
SRN CALIF   A    B     IDAHO       A    A     NEVADA      A    B     
W MONTANA   A    A     E MONTANA   A    N     WYOMING     A    A     
UTAH        A    N     ARIZONA     A    B     COLORADO    A    A     
NEW MEXICO  N    A     N DAKOTA    A    N     S DAKOTA    A    A     
NEBRASKA    A    A     KANSAS      B    A     OKLAHOMA    B    A     
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A     
MINNESOTA   A    A     IOWA        N    A     MISSOURI    B    A     
ARKANSAS    B    A     LOUISIANA   B    A     WISCONSIN   N    A     
ILLINOIS    B    A     MISSISSIPPI B    A     MICHIGAN    N    A     
INDIANA     B    A     OHIO        B    A     KENTUCKY    B    A     
TENNESSEE   B    A     ALABAMA     B    A     NEW YORK    B    A     
VERMONT     B    A     NEW HAMP    B    A     MAINE       B    N     
MASS        B    A     CONN        B    A     RHODE IS    B    A     
PENN        B    A     NEW JERSEY  B    A     W VIRGINIA  B    A     
MARYLAND    B    A     DELAWARE    B    A     VIRGINIA    B    A     
N CAROLINA  B    A     S CAROLINA  B    A     GEORGIA     B    A     
FL PNHDL    N    A     FL PENIN    N    A     AK N SLOPE  A    N     
AK ALEUTIAN A    B     AK WESTERN  A    B     AK INT BSN  A    N     
AK S INT    A    B     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.
$$