399
FXUS06 KWBC 112001
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST WED DECEMBER 11 2024
6-10 DAY OUTLOOK FOR DEC 17 - 21 2024
POSITIVE MID-LEVEL HEIGHT ANOMALIES ARE GENERALLY FAVORED ACROSS THE CONTIGUOUS
UNITED STATES (CONUS) DURING THE 6-10 DAY PERIOD. THE STRONGEST ANOMALIES
DURING THE PERIOD ARE FORECAST FOR THE WESTERN CONUS WITH AN ASSOCIATED STRONG
MID-LEVEL RIDGE. THE AXIS OF THIS RIDGE IS FORECAST TO BE JUST INLAND BRINGING
ONSHORE MID-LEVEL FLOW TO THE WEST COAST OF NORTH AMERICA. IN THE EAST, HEIGHT
ANOMALIES ARE REDUCED IN MAGNITUDE RELATIVE TO YESTERDAY’S FORECAST WITH A
SHORTWAVE TROUGH PROGRESSING EASTWARD ACROSS THE CONUS. THIS LEADS TO A WEAK
TROUGH BEGINNING TO DEVELOP ACROSS THE REGION. AN AREA OF STRONGLY BELOW-NORMAL
MID-LEVEL HEIGHTS IS FORECAST ACROSS THE NORTH PACIFIC LEADING TO ONSHORE,
SOUTHERLY FLOW INTO MUCH OF ALASKA. POSITIVE 500-HPA HEIGHTS ARE FORECAST FOR
HAWAII.
ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS MOST OF THE COUNTRY TODAY. THE
STRONGEST CHANCES ARE IN HAWAII WHERE ABOVE-NORMAL CHANCES EXCEED 80% WITH
STRONG AGREEMENT AMONG REFORECAST AND SHORT-TERM BIAS-CORRECTED TOOLS BENEATH
POSITIVE MID-LEVEL HEIGHT ANOMALIES. IN THE CONUS, POSITIVE MID-LEVEL HEIGHT
ANOMALIES FORECAST ACROSS THE WESTERN CONUS RESULT IN ABOVE-NORMAL TEMPERATURES
TO BE FAVORED. THE STRONGEST PROBABILITIES FOR ABOVE-NORMAL (>60%) ARE FORECAST
FOR PARTS OF THE NORTHERN AND CENTRAL ROCKIES. A SHORTWAVE TROUGH PROGRESSING
THROUGH THE CONUS DURING THE PERIOD BRINGS REDUCED CHANCES FOR ABOVE-NORMAL TO
NEAR-NORMAL TEMPERATURES TO BE FAVORED ACROSS THE MISSISSIPPI VALLEY REGION.
PROBABILITIES THEN INCREASE ALONG THE IMMEDIATE EAST COAST AHEAD OF THE FAST
MOVING SHORTWAVE TROUGH. IN ALASKA, SOUTHERLY FLOW BRINGS STRONG CHANCES FOR
ABOVE-NORMAL TEMPERATURES WITH PROBABILITIES EXCEEDING 70% IN THE SOUTHWESTERN
MAINLAND IN GOOD AGREEMENT WITH MOST MODEL GUIDANCE.
A STRONG TROUGH OVER THE NORTHERN PACIFIC OCEAN AND RIDGE ACROSS WESTERN NORTH
AMERICA ARE LIKELY TO BRING ONSHORE MID-LEVEL FLOW INTO THE WEST COAST OF NORTH
AMERICA. THERE REMAINS SOME UNCERTAINTY IN REGARDS TO THE PLACEMENT OF THE
MID-LEVEL RIDGE AXIS IN THE WESTERN CONUS. A FURTHER INLAND RIDGE WOULD LIKELY
RESULT IN MORE PRECIPITATION FOR THE NORTHWEST AND NORTHERN CALIFORNIA RELATIVE
TO THE AXIS REMAINING NEAR THE IMMEDIATE WEST COAST. TODAY, THE FORECAST RIDGE
AXIS HAS SHIFTED FURTHER WEST, REDUCING CHANCES FOR ABOVE-NORMAL PRECIPITATION
ACROSS THE WEST COAST RELATIVE TO YESTERDAY. THEREFORE, ONLY A SLIGHT TILT
TOWARDS ABOVE-NORMAL IS FAVORED ALONG THE IMMEDIATE PACIFIC NORTHWEST COASTLINE
WITH NEAR-NORMAL FAVORED FURTHER SOUTH. ABOVE-NORMAL PRECIPITATION IS STRONGLY
FAVORED IN MUCH OF SOUTHERN ALASKA. BELOW-NORMAL PRECIPITATION IS FAVORED
ACROSS THE NORTHERN MAINLAND. ACROSS THE SOUTHWEST AND INTERIOR WEST,
BELOW-NORMAL PRECIPITATION IS FORECAST WITH LITTLE OF THE MOISTURE LIKELY TO
REACH THESE AREAS. IN THE EAST, THE PRECIPITATION FORECAST IS QUITE UNCERTAIN.
THE GEFS MAINTAINS A WETTER PATTERN FOR PORTIONS OF THE SOUTHERN PLAINS THROUGH
THE MIDDLE MISSISSIPPI VALLEY ASSOCIATED WITH A CLIPPER SYSTEM EARLY IN THE
PERIOD. TOOLS CONTINUE TO SHOW ADDITIONAL ABOVE-NORMAL PRECIPITATION CHANCES
FOR PORTIONS OF THE EAST COAST. BENEATH A MID-LEVEL RIDGE, HAWAII IS FAVORED TO
HAVE BELOW-NORMAL PRECIPITATION.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 25% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 8, 35% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 30%
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. GOOD
AGREEMENT AMONG THE DYNAMICAL AND STATISTICAL TOOLS IS OFFSET BY A PROGRESSIVE
AND SHIFTING PATTERN AND WEAK PRECIPITATION SIGNALS.
8-14 DAY OUTLOOK FOR DEC 19 - 25 2024
MID-LEVEL RIDGING REMAINS FORECAST ACROSS MUCH OF THE WESTERN CONUS. THE
MID-LEVEL RIDGE AXIS IS FORECAST TO BE JUST INLAND BRINGING ONSHORE
SOUTHWESTERLY FLOW ACROSS THE PACIFIC NORTHWEST INTO NORTHERN CALIFORNIA.
ACROSS THE EASTERN CONUS, ABOVE-NORMAL HEIGHTS REMAIN FORECAST IN THE NORTHEAST
BUT REDUCED IN MAGNITUDE RELATIVE TO THE 6-10 DAY PERIOD AS THE PATTERN
PROGRESSES EAST. NEAR TO BELOW-NORMAL MID-LEVEL HEIGHTS ARE FORECAST ACROSS
PORTIONS OF FLORIDA AND THE SURROUNDING AREA. IN ALASKA AND THE NORTH PACIFIC A
DEEP TROUGH REMAINS FORECAST BRINGING SOUTHERLY FLOW INTO MUCH OF ALASKA.
POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST FOR HAWAII.
ABOVE-NORMAL TEMPERATURES REMAIN FAVORED ACROSS MOST OF THE WESTERN CONUS
DURING THE WEEK-2 PERIOD. THE STRONGEST PROBABILITIES ARE FORECAST ACROSS THE
WEST INTO THE PLAINS WITH PROBABILITIES EXCEEDING 60% ACROSS MOST OF THE REGION
AND PARTS OF THE NORTHERN AND CENTRAL ROCKIES EXCEEDING 70%. EAST OF THE
MISSISSIPPI VALLEY, PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES DECLINE WITH A
BROADER AREA OF NEAR-NORMAL TEMPERATURES FAVORED FOR MUCH OF THE EAST WITH MORE
UNCERTAINTY AMONG THE REFORECAST AND SHORT-TERM BIAS-CORRECTED TOOLS. A
SHORTWAVE TROUGH PROGRESSING EASTWARD IN THE 6-10 DAY PERIOD MAY BECOME MORE
ESTABLISHED ACROSS THE EAST DURING THE WEEK-2 PERIOD. THIS WOULD BRING COOLER
TEMPERATURES TO THE EAST RELATIVE TO THE 6-10 DAY PERIOD. IN ALASKA,
ABOVE-NORMAL TEMPERATURES ARE STRONGLY FAVORED WITH SOUTHERLY FLOW INTO THE
STATE. ABOVE-NORMAL TEMPERATURES ARE ALSO STRONGLY FAVORED IN HAWAII, AS IN THE
6-10 DAY PERIOD.
THE WEEK-2 PRECIPITATION FORECAST FAVORS BELOW-NORMAL PRECIPITATION ACROSS MUCH
OF THE CONUS. SURFACE HIGH PRESSURE IS FORECAST ACROSS MUCH OF THE PLAINS,
MISSISSIPPI VALLEY, AND SOUTHEAST, REDUCING CHANCES FOR PRECIPITATION ACROSS
THESE REGIONS. AN EXCEPTION IS IN PARTS OF SOUTHERN TEXAS WHERE WEAK ONSHORE
FLOW OFF THE GULF OF MEXICO INCREASES CHANCES FOR PRECIPITATION. TOOLS HAVE
SHIFTED TOWARDS A DRIER SOLUTION ACROSS THE WEST COAST RELATIVE TO PRIOR
FORECASTS WITH THE MOST RECENT GEFS RUNS INDICATING BELOW-NORMAL PRECIPITATION
IS MOST LIKELY. THE ECENS CONTINUES TO FORECAST SLIGHT CHANCES FOR ABOVE-NORMAL
PRECIPITATION PARTICULARLY ACROSS THE PACIFIC NORTHWEST. THEREFORE,
ABOVE-NORMAL PRECIPITATION CHANCES ARE REDUCED ACROSS THE WEST COAST IN TODAY’S
FORECAST RELATIVE TO YESTERDAY, BUT THERE REMAINS CONSIDERABLE UNCERTAINTY IN
THE PRECIPITATION FORECAST OVER THESE AREAS. THERE IS BETTER AGREEMENT BETWEEN
THE GEFS AND ECENS FOR A SLOWER PROGRESSION OF THE RIDGE EASTWARD RELATIVE TO
YESTERDAY BRINGING DRIER CONDITIONS TO THE SOUTHWEST AND CENTRAL AND SOUTHERN
ROCKIES. IN ALASKA, ABOVE-NORMAL PRECIPITATION REMAINS FORECAST ACROSS THE
SOUTHERN PORTIONS OF ALASKA, WITH NEAR-NORMAL PRECIPITATION FAVORED ACROSS
NORTHERN ALASKA. BELOW-NORMAL PRECIPITATION IS FAVORED IN HAWAII, CONSISTENT
WITH THE DYNAMICAL MODEL GUIDANCE.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 5% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 30% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 11, 35% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 30%
OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: AVERAGE, 3 OUT OF 5, WITH
DIVERGENT SOLUTIONS AMONG THE MODEL GUIDANCE FOR PRECIPITATION REDUCING
CONFIDENCE OFFSET BY VERY GOOD AGREEMENT AMONG TEMPERATURE SOLUTIONS.
FORECASTER: RYAN BOLT
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 1991-2020 BASE PERIOD MEANS AS REFERENCE IN
THE CLIMATE OUTLOOKS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON
DECEMBER 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:
20071122 - 20061202 - 19991221 - 19861210 - 19521125
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:
20061203 - 19521124 - 19851211 - 20071122 - 19861207
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 17 - 21 2024
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 N
N TEXAS A N S TEXAS A A W TEXAS A B
MINNESOTA N B IOWA N B MISSOURI N B
ARKANSAS A N LOUISIANA A N WISCONSIN N B
ILLINOIS N N MISSISSIPPI A N MICHIGAN N N
INDIANA N N OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A 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 A N
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA A N GEORGIA A N
FL PNHDL A N FL PENIN A A AK N SLOPE A B
AK ALEUTIAN A N AK WESTERN A A AK INT BSN A B
AK S INT A A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 19 - 25 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A N NRN CALIF A N
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 N S TEXAS A N W TEXAS A B
MINNESOTA A B IOWA A B MISSOURI A B
ARKANSAS A B LOUISIANA N B WISCONSIN A B
ILLINOIS A B MISSISSIPPI N B MICHIGAN A B
INDIANA A B OHIO N B KENTUCKY N B
TENNESSEE N B ALABAMA N B NEW YORK N N
VERMONT N N NEW HAMP N N MAINE A N
MASS N N CONN N N RHODE IS N N
PENN N N NEW JERSEY N N W VIRGINIA N N
MARYLAND N N DELAWARE N N VIRGINIA N N
N CAROLINA N N S CAROLINA N N GEORGIA N N
FL PNHDL N N FL PENIN B N AK N SLOPE A N
AK ALEUTIAN A N AK WESTERN A N AK INT BSN A N
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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