PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST TUE DECEMBER 11 2018
6-10 DAY OUTLOOK FOR DEC 17 - 21 2018
TODAY'S ENSEMBLE MODELS ARE IN GOOD AGREEMENT ON THE PREDICTED 500-HPA
CIRCULATION PATTERN OVER NORTH AMERICA FOR THE 6-10 DAY PERIOD. AN AMPLIFIED
TROUGH IS ANTICIPATED OVER WESTERN MAINLAND ALASKA EXTENDING SOUTHEASTWARD OFF
THE COAST OF NORTHWESTERN NORTH AMERICA. RIDGING IS FORECAST DOWNSTREAM OF THIS
TROUGH OVER MUCH OF THE INTERIOR WESTERN CONUS EXTENDING TO THE NORTHERN
PLAINS. TODAY'S MANUAL 500-HPA HEIGHT BLEND IS BASED PRIMARILY ON THE ENSEMBLE
MEAN SOLUTIONS FROM THE GEFS AND ECMWF. BELOW NORMAL HEIGHTS ARE FORECAST
ACROSS ALASKA AND THE PACIFIC NORTHWEST COAST. ABOVE NORMAL HEIGHTS ARE
GENERALLY FORECAST ACROSS MUCH OF THE CONUS. NEAR TO SLIGHTLY BELOW NORMAL
HEIGHTS ARE FORECAST ACROSS THE SOUTHEASTERN CONUS.
BELOW NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF MAINLAND ALASKA AND THE
ALEUTIANS IN ASSOCIATION WITH THE TROUGH PREDICTED IN THE VICINITY. THERE ARE
ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES AHEAD OF THIS TROUGH FOR
THE ALASKA PANHANDLE EXTENDING SOUTH TO PARTS OF THE PACIFIC NORTHWEST. ABOVE
NORMAL TEMPERATURES ARE FAVORED FARTHER TO THE EAST ACROSS MUCH OF THE CONUS
UNDERNEATH ABOVE NORMAL HEIGHTS AND PACIFIC FLOW. NEAR NORMAL TEMPERATURES ARE
FAVORED FOR MUCH OF THE FLORIDA PENINSULA, CONSISTENT WITH DYNAMICAL FORECAST
TOOLS.
ABOVE NORMAL PRECIPITATION IS LIKELY FOR THE PACIFIC NORTHWEST AHEAD OF A MEAN
TROUGH PREDICTED OFFSHORE OF NORTHWESTERN NORTH AMERICA. NEAR TO BELOW NORMAL
PRECIPITATION IS FAVORED FOR PARTS OF THE SOUTHWEST, THE CENTRAL GREAT PLAINS
AND THE CENTRAL ROCKIES DUE TO RIDGING AND ABOVE NORMAL HEIGHTS. THE POTENTIAL
FOR SOUTHERN STREAM ENERGY LEADS TO SLIGHTLY ENHANCED PROBABILITIES OF ABOVE
NORMAL PRECIPITATION FOR PARTS OF THE SOUTHWEST AND THE SOUTHERN PLAINS IN
ASSOCIATION WITH MEAN CYCLONIC FLOW. BELOW NORMAL PRECIPITATION IS LIKELY FOR
PARTS OF THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHEAST EXTENDING NORTHEASTWARD
TO PARTS OF THE MID_ATLANTIC AND THE NORTHEAST, CONSISTENT WITH CONSOLIDATION
FORECAST TOOLS. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED ACROSS MUCH OF
ALASKA, ASSOCIATED WITH A TROUGH PREDICTED OVER WESTERN PARTS OF THE STATE.
BELOW NORMAL PRECIPITATION IS FAVORED FOR PARTS OF WESTERN MAINLAND ALASKA DUE
TO PREDICTED MEAN LOW-LEVEL OFFSHORE FLOW.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 8, 15% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 8, 10% OF
TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 8, 40% OF TODAY'S 0Z EUROPEAN
ENSEMBLE MEAN CENTERED ON DAY 8, AND 10% 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 MODEL SOLUTIONS AND ASSOCIATED SURFACE TOOLS
8-14 DAY OUTLOOK FOR DEC 19 - 25 2018
TODAY'S MODEL ENSEMBLE MEANS ARE IN FAIR AGREEMENT ON THE PREDICTED 500-HPA
CIRCULATION PATTERN DURING THE 8-14 DAY PERIOD. A TROUGH IS FORECAST TO
DEAMPLIFY ACROSS THE WESTERN BERING SEA. DOWNSTREAM RIDGING IS FORECAST TO
DEVELOP OVER CALIFORNIA. A LOW AMPLITUDE TROUGH IS GENERALLY FORECAST FARTHER
TO THE EAST OVER THE EASTERN AND CENTRAL CONUS. THE MANUAL 500-HPA HEIGHT
BLEND, BASED PRIMARILY ON THE ENSEMBLE MEANS FROM THE GEFS AND ECMWF, FEATURES
BELOW NORMAL HEIGHTS FOR ALASKA, AND NEAR TO ABOVE NORMAL HEIGHTS FOR A
MAJORITY OF THE CONUS.
ABOVE NORMAL TEMPERATURES ARE FAVORED ACROSS MUCH OF THE CONUS UNDERNEATH
PREDICTED NEAR TO ABOVE NORMAL HEIGHTS. ABOVE NORMAL TEMPERATURES ARE FAVORED
AHEAD OF THE TROUGH AXIS FOR THE ALASKA PANHANDLE AND PARTS OF SOUTHEASTERN
MAINLAND ALASKA. ABOVE NORMAL TEMPERATURES ARE LIKELY FOR THE COASTAL AREAS OF
SOUTHERN AND WESTERN MAINLAND ALASKA AND THE ALEUTIANS DUE TO ABOVE NORMAL SEA
SURFACE TEMPERATURES NEARBY WITH BELOW NORMAL TEMPERATURES FAVORED FOR PARTS OF
NORTHERN MAINLAND ALASKA, CONSISTENT WITH CONSOLIDATION FORECAST TOOLS.
ABOVE NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE NORTHWESTERN CONUS DUE
TO PERSISTENT UPSTREAM TROUGHING. DOWNSTREAM RIDGING ACROSS THE WESTERN CONUS
LEADS TO ENHANCED PROBABILITIES OF BELOW NORMAL PRECIPITATION FOR MUCH OF
CALIFORNIA, THE CENTRAL GREAT BASIN, PARTS OF THE DESERT SOUTHWEST AND THE
SOUTHERN ROCKIES. ABOVE NORMAL PRECIPITATION IS FAVORED FOR THE REMINDER OF THE
CONUS UNDERNEATH PREDICTED CYCLONIC FLOW. ABOVE NORMAL PRECIPITATION IS FAVORED
FOR MUCH OF ALASKA AHEAD OF FORECAST TROUGHING OVER THE WESTERN BERING SEA.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 11, 15% OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 11, 40% OF
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 20% OF TODAY'S 0Z
CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO FAIR
AGREEMENT ON THE PREDICTED 500-HPA HEIGHT PATTERN, OFFSET BY DIFFERENCES AMONG
THE SURFACE TOOLS ACROSS MUCH OF THE FORECAST DOMAIN.
FORECASTER: Y. FAN
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 20.
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:
19591221 - 19861129 - 20081123 - 19841121 - 19981211
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:
19591220 - 19861128 - 19841120 - 19981211 - 19991202
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 17 - 21 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 A WYOMING A N
UTAH A B ARIZONA A N COLORADO A B
NEW MEXICO A A N DAKOTA A N S DAKOTA A N
NEBRASKA A N KANSAS A N OKLAHOMA A N
N TEXAS A N S TEXAS A A W TEXAS A A
MINNESOTA A N IOWA A N MISSOURI A B
ARKANSAS A B LOUISIANA A B WISCONSIN A N
ILLINOIS A B MISSISSIPPI A B MICHIGAN A N
INDIANA A B OHIO A N KENTUCKY A B
TENNESSEE A B ALABAMA A B NEW YORK A N
VERMONT A N NEW HAMP A B MAINE A N
MASS A B CONN A B RHODE IS A B
PENN A N NEW JERSEY A B W VIRGINIA A B
MARYLAND A B DELAWARE A B VIRGINIA A B
N CAROLINA A B S CAROLINA A B GEORGIA A B
FL PNHDL A B FL PENIN N N AK N SLOPE B A
AK ALEUTIAN B A AK WESTERN B N AK INT BSN B A
AK S INT B A AK SO COAST B A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 19 - 25 2018
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON N A OREGON A A NRN CALIF A B
SRN CALIF A B IDAHO N A NEVADA A B
W MONTANA N A E MONTANA A A WYOMING A A
UTAH A B ARIZONA A B COLORADO A A
NEW MEXICO A A N DAKOTA A A S DAKOTA A A
NEBRASKA A A KANSAS A A OKLAHOMA A A
N TEXAS A A S TEXAS A A W TEXAS A A
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A A LOUISIANA A N WISCONSIN A A
ILLINOIS A A MISSISSIPPI A A MICHIGAN A A
INDIANA A A OHIO A A KENTUCKY A A
TENNESSEE A A ALABAMA A 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 A A NEW JERSEY A A W VIRGINIA A A
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA A A GEORGIA A A
FL PNHDL A A FL PENIN A A AK N SLOPE N A
AK ALEUTIAN A A AK WESTERN N A AK INT BSN N A
AK S INT N A AK SO COAST A A 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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