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FXUS06 KWBC 122002
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST THU DECEMBER 12 2024
6-10 DAY OUTLOOK FOR DEC 18 - 22 2024
AN AREA OF STRONGLY BELOW-NORMAL MID-LEVEL HEIGHTS IS FORECAST ACROSS THE NORTH
PACIFIC UPSTREAM OF A STRONG RIDGE AND POSITIVE MID-LEVEL HEIGHT ANOMALIES
ACROSS THE WESTERN CONTIGUOUS UNITED STATES (CONUS) DURING THE 6-10 DAY PERIOD.
THE STRONGEST POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST OVER THE NORTHERN
ROCKIES WITH AN ASSOCIATED STRONG MID-LEVEL RIDGE. THE AXIS OF THIS RIDGE IS
FORECAST TO BE JUST INLAND OF THE WEST COAST RESULTING IN ONSHORE MID-LEVEL
FLOW TO MUCH OF ALASKA. TODAY’S FORECAST HAS REDUCED CHANCES FOR ENHANCED
ONSHORE FLOW INTO MUCH OF THE WESTERN CONUS RELATIVE TO PRIOR FORECASTS. IN THE
EAST, MID-LEVEL HEIGHTS ARE FORECAST TO BE NEAR-NORMAL FOR THE PERIOD AS A
SHORTWAVE MID-LEVEL TROUGH DEVELOPS INTO A BROAD TROUGH ACROSS THE EAST
DISPLACING POSITIVE 500-HPA HEIGHTS ANOMALIES AT THE ONSET OF THE PERIOD.
POSITIVE 500-HPA HEIGHTS ARE FORECAST FOR HAWAII.
ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS THE WESTERN HALF OF THE CONUS
BENEATH A STRONG MID-LEVEL RIDGE WITH PROBABILITIES EXCEEDING 70% ACROSS THE
NORTHWEST INTO THE NORTHERN AND CENTRAL ROCKIES. A SHORTWAVE TROUGH PROGRESSING
INTO THE EASTERN CONUS EARLY IN THE PERIOD DEVELOPS INTO A FULL LATITUDE TROUGH
BY END OF THE 6-10 DAY. THE RAPID PROGRESSION OF THE PATTERN BRINGS CHANCES FOR
NEAR-NORMAL TEMPERATURES AS MODEL GUIDANCE DEVELOPS CHANCES FOR BELOW-NORMAL
TEMPERATURES TO DISPLACE POSITIVE TEMPERATURE ANOMALIES BY THE SECOND HALF OF
THE PERIOD. IN ALASKA, SOUTHERLY FLOW BRINGS STRONG CHANCES FOR ABOVE-NORMAL
TEMPERATURES WITH PROBABILITIES EXCEEDING 80% IN SOUTHEAST ALASKA IN GOOD
AGREEMENT WITH MOST MODEL GUIDANCE. THERE ARE STRONG CHANCES FOR ABOVE-NORMAL
TEMPERATURES IN HAWAII WHERE PROBABILITIES EXCEED 80% WITH STRONG AGREEMENT
AMONG REFORECAST AND SHORT-TERM BIAS-CORRECTED TOOLS BENEATH POSITIVE MID-LEVEL
HEIGHT ANOMALIES.
THE RIDGE ACROSS THE WESTERN CONUS CONTINUES TO AMPLIFY IN MOST MODEL TOOLS
TODAY REDUCING CHANCES FOR PRECIPITATION INTO MOST OF THE WESTERN CONUS. THE
GREATEST UNCERTAINTY IS ALONG THE IMMEDIATE WEST COAST WHERE NEAR-NORMAL IS
FAVORED. EAST OF THE CASCADES AND SIERRA NEVADA, STRONG CHANCES FOR
BELOW-NORMAL PRECIPITATION IS FAVORED EXPANDING EAST INTO THE PLAINS AND UPPER
MISSISSIPPI VALLEY BENEATH THE EXPANDING RIDGE. ABOVE-NORMAL IS FAVORED ALONG
THE IMMEDIATE EAST COAST AHEAD OF THE DEVELOPING MID-LEVEL TROUGH. IN ALASKA,
ABOVE-NORMAL PRECIPITATION IS FAVORED ACROSS THE SOUTHERN HALF OF THE STATE
WITH STRONG AGREEMENT AMONG THE GUIDANCE AND WITH THE OVERALL MID-LEVEL
PATTERN. IN HAWAII, BELOW-NORMAL PRECIPITATION IS FORECAST BENEATH A MID-LEVEL
RIDGE AND IN GOOD AGREEMENT WITH DYNAMICAL MODEL GUIDANCE.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 35% 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 20 - 26 2024
MID-LEVEL RIDGING AND STRONG POSITIVE 500-HPA HEIGHT ANOMALIES REMAIN FORECAST
ACROSS MUCH OF THE WESTERN CONUS WITH A DEEP TROUGH UPSTREAM OVER THE NORTH
PACIFIC. ACROSS THE EASTERN CONUS, ABOVE-NORMAL HEIGHTS ARE EXPANDING FROM THE
RIDGE ACROSS THE WEST INTO THE EAST. HOWEVER, NEAR- TO BELOW-NORMAL 500-HPA
HEIGHTS ARE FORECAST ACROSS PORTIONS OF THE SOUTHEAST AND FLORIDA. 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 70% ACROSS MOST OF THE
REGION. NEAR-NORMAL TEMPERATURES ARE FAVORED IN THE NORTHEAST WITH A QUICK
TRANSITION BETWEEN FORECAST BELOW-NORMAL TEMPERATURES, ASSOCIATED WITH A
DEVELOPING MID-LEVEL TROUGH, EARLY IN THE PERIOD GIVING WAY TO ABOVE-NORMAL
TEMPERATURES IN THE SECOND HALF OF WEEK-2 AS POSITIVE MID-LEVEL HEIGHT
ANOMALIES DEVELOP. IN THE SOUTHEAST, THE MID-LEVEL TROUGH AT THE ONSET OF THE
PERIOD LINGERS LONGER THAN IN THE NORTHEAST MAINTAINING INCREASED CHANCES FOR
BELOW-NORMAL TEMPERATURES THROUGH THE END OF WEEK-2. 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. TOOLS CONTINUE TO HAVE MIXED SIGNALS ALONG THE WEST COAST AND
NEAR-NORMAL PRECIPITATION IS FORECAST. THE ECENS BASED FORECASTS INDICATE MORE
PRECIPITATION RELATIVE TO THE DRIER GEFS BASED TOOLS. WE ARE NEAR THE
CLIMATOLOGICAL PEAK OF PRECIPITATION ALONG THE WEST COAST SO NEAR-NORMAL
PRECIPITATION MAY STILL BRING CHANCES FOR ROUNDS OF PRECIPITATION INTO THE
REGION. 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: 35% 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:
19521125 - 20001220 - 20061202 - 19851226 - 19591126
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:
19521125 - 20001219 - 19831127 - 20061204 - 19851225
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 18 - 22 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N OREGON A B 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 N B
N TEXAS N N S TEXAS N N W TEXAS A B
MINNESOTA N B IOWA N B MISSOURI N B
ARKANSAS N N LOUISIANA N N WISCONSIN N B
ILLINOIS N B MISSISSIPPI N N MICHIGAN N N
INDIANA N B OHIO N N KENTUCKY N N
TENNESSEE N N ALABAMA N N NEW YORK N A
VERMONT N A NEW HAMP N A MAINE A A
MASS N A CONN N A RHODE IS N A
PENN N N NEW JERSEY N A W VIRGINIA N N
MARYLAND N A DELAWARE N A VIRGINIA N A
N CAROLINA N A S CAROLINA N A GEORGIA N N
FL PNHDL N N FL PENIN N A AK N SLOPE A B
AK ALEUTIAN A A AK WESTERN A N 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 20 - 26 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 B 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 B B MICHIGAN A B
INDIANA N B OHIO N B KENTUCKY N B
TENNESSEE N B ALABAMA B B NEW YORK N N
VERMONT N N NEW HAMP N N MAINE N N
MASS N N CONN N N RHODE IS N N
PENN N B NEW JERSEY N N W VIRGINIA N B
MARYLAND B N DELAWARE B N VIRGINIA B B
N CAROLINA B N S CAROLINA B B GEORGIA B B
FL PNHDL B B FL PENIN B B AK N SLOPE A N
AK ALEUTIAN A N 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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