922
FXUS06 KWBC 282002
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST THU NOVEMBER 28 2024
6-10 DAY OUTLOOK FOR DEC 04 - 08 2024
THE GEFS, ECENS, AND CMCE ARE IN GOOD AGREEMENT AND CONSISTENT THAT A HIGHLY
AMPLIFIED LONGWAVE PATTERN PERSISTS OVER NORTH AMERICA THROUGH AT LEAST EARLY
DECEMBER. THESE ENSEMBLE MEAN SOLUTIONS FEATURE ANOMALOUS 500-HPA RIDGING WITH
LARGE POSITIVE HEIGHT ANOMALIES OVER THE WESTERN CONTIGUOUS U.S. (CONUS),
SUPPORTING AN INCREASED CHANCE OF ABOVE-NORMAL TEMPERATURES FROM THE WEST COAST
TO THE GREAT PLAINS. THE ABOVE-NORMAL TEMPERATURE PROBABILITIES ARE SLIGHTLY
REDUCED ACROSS THE GREAT BASIN AS SURFACE HIGH PRESSURE MAY LEAD TO LOW-LEVEL
INVERSIONS WITH A COOLING EFFECT ON THE OVERALL WARMER PATTERN. DOWNSTREAM OF
THE FULL-LATITUDE RIDGE ACROSS WESTERN NORTH AMERICA, A COUPLE OF ARCTIC
SURFACE HIGHS ARE FORECAST TO SHIFT SOUTH FROM CANADA INTO THE EASTERN CONUS
DURING THE FIRST WEEK OF DECEMBER. THESE SURFACE HIGHS FAVOR BELOW-NORMAL
TEMPERATURES ACROSS THE EASTERN CONUS AND GREAT LAKES. THE LARGEST BELOW-NORMAL
TEMPERATURE PROBABILITIES (EXCEEDING 70%) ARE FORECAST ACROSS THE NORTHEAST
WHERE THE ANOMALOUS COLD IS EXPECTED TO BE THE STRONGEST.
THE AMPLIFIED LONGWAVE RIDGE ALONG THE WEST COAST FAVORS BELOW-NORMAL
PRECIPITATION FROM SOUTHERN OREGON AND CALIFORNIA EASTWARD TO THE MIDDLE
MISSISSIPPI VALLEY. THE MOST LIKELY AREA TO HAVE BELOW-NORMAL PRECIPITATION
INCLUDES MUCH OF CALIFORNIA AND NEVADA, AS THE HIGH AMPLITUDE RIDGE KEEPS THE
NORTH PACIFIC STORM TRACK DISPLACED NORTHWARD OVER BRITISH COLUMBIA AND ALASKA.
DESPITE THE FULL-LATITUDE RIDGE OVER WESTERN NORTH AMERICA, THE GEFS AND ECENS
REFORECAST TOOLS ALONG WITH THEIR UNCALIBRATED MODEL OUTPUT CONTINUE TO DEPICT
ELEVATED ABOVE-NORMAL PRECIPITATION PROBABILITIES FOR PORTIONS OF THE PACIFIC
NORTHWEST, NORTHERN ROCKIES, AND NORTHERN GREAT PLAINS. THIS IS RELATED TO
NORTHERN STREAM SHORTWAVE TROUGHS MOVING OVER THE LONGWAVE RIDGE. A SOUTHERN
STREAM SHORTWAVE TROUGH ELEVATES CHANCES OF ABOVE-NORMAL PRECIPITATION FOR MUCH
OF TEXAS AND THE LOWER MISSISSIPPI VALLEY. ADDITIONAL LAKE-EFFECT SNOW IS
FAVORED TO OCCUR DURING THIS 5-DAY PERIOD, TILTING THE OUTLOOK TOWARDS
ABOVE-NORMAL PRECIPITATION DOWNWIND OF LAKES ERIE, ONTARIO, AND SUPERIOR. NEAR
NORMAL PRECIPITATION IS FAVORED FOR MOST OF THE EASTERN CONUS DUE TO
CONFLICTING SIGNALS AMONG THE PRECIPITATION TOOLS. THE PLACEMENT OF THE
LONGWAVE TROUGH AXIS NEAR THE EAST COAST WILL BE CRITICAL ON WHERE ANY SURFACE
LOWS DEVELOP AND TRACK.
ANOMALOUS SOUTHERLY, ONSHORE FLOW SUPPORTS AN INCREASED CHANCE OF ABOVE-NORMAL
TEMPERATURES AND PRECIPITATION ACROSS THE SOUTHERN TWO-THIRDS OF ALASKA. CLOSER
TO THE NORTH SLOPE, THE CONSOLIDATION (SKILL-WEIGHTED GEFS AND ECENS REFORECAST
TOOLS) FAVORS BELOW-NORMAL PRECIPITATION ALONG WITH NEAR TO BELOW-NORMAL
TEMPERATURES.
BASED ON THE GEFS AND ECENS, ABOVE-NORMAL TEMPERATURES ARE STRONGLY FAVORED FOR
HAWAII. THE CONSOLIDATION SUPPORTS ELEVATED ABOVE-NORMAL PRECIPITATION
PROBABILITIES FOR MUCH OF THE STATE EXCEPT THE SOUTHEASTERN BIG ISLAND.
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, DUE TO
GOOD MODEL AGREEMENT ON A PERSISTENT, HIGHLY AMPLIFIED LONGWAVE PATTERN.
8-14 DAY OUTLOOK FOR DEC 06 - 12 2024
THE HIGHLY AMPLIFIED LONGWAVE PATTERN WITH A FULL-LATITUDE RIDGE OVER WESTERN
NORTH AMERICA AND A DOWNSTREAM TROUGH NEAR THE EAST COAST IS FORECAST TO
PERSIST INTO THE SECOND WEEK OF DECEMBER. THE ECENS AND CMCE ARE MORE AMPLIFIED
WITH THE LONGWAVE TROUGH THAN THE GEFS. GIVEN THE STABLE AND AMPLIFIED LONGWAVE
PATTERN, THE 6-10 AND 8-14 DAY TEMPERATURE OUTLOOKS ARE VERY SIMILAR AND
FORECAST CONFIDENCE IS HIGH FOR ABOVE (BELOW)-NORMAL TEMPERATURES ACROSS THE
WESTERN (NORTHEASTERN) CONUS. THE LARGEST UNCERTAINTY IN THE 8-14 DAY
TEMPERATURE OUTLOOK IS ACROSS THE SOUTHEAST WHERE THE GEFS AND ECENS REFORECAST
TOOLS ARE GENERALLY WARMER THAN THEIR UNCALIBRATED OUTPUT. THE AMPLITUDE OF THE
LONGWAVE TROUGH NEAR THE EAST COAST WILL BE THE KEY FACTOR IN THE DURATION OF
ANOMALOUS COLD FOR THIS REGION. ABOVE-NORMAL TEMPERATURES ARE MORE LIKELY
ACROSS THE LOWER MISSISSIPPI VALLEY, WHILE CHANCES FOR BELOW-NORMAL
TEMPERATURES INCREASE FARTHER TO THE EAST ACROSS THE SOUTHERN APPALACHIANS AND
CAROLINAS.
THE HIGHEST FORECAST CONFIDENCE IN THE 8-14 DAY PRECIPITATION OUTLOOK EXISTS
FOR NORTHERN CALIFORNIA SINCE THE STORM TRACK ACROSS THE NORTH PACIFIC IS
PREDICTED TO BE DISPLACED NORTH OF ITS TYPICAL LOCATION DURING EARLY DECEMBER.
NORTHERN STREAM SHORTWAVE TROUGHS LEAD TO ELEVATED ABOVE-NORMAL PRECIPITATION
PROBABILITIES ACROSS NORTHERN PORTIONS OF THE ROCKIES AND GREAT PLAINS. A
SOUTHERN STREAM SHORTWAVE TROUGH ALONG WITH RETURN FLOW FROM THE GULF OF MEXICO
SLIGHTLY FAVORS ABOVE-NORMAL PRECIPITATION ACROSS THE SOUTH-CENTRAL CONUS. FOR
THE SECOND CONSECUTIVE DAY, THE GEFS MODEL IS WETTER THAN THE ECENS, ESPECIALLY
ACROSS THE EASTERN AND CENTRAL CONUS. THIS IS DUE TO A PREDICTED SLIGHT
RETROGRESSION OF THE LONGWAVE PATTERN ALONG WITH A LESS AMPLIFIED TROUGH OVER
THE EASTERN CONUS, WHICH LEADS TO AN INCREASED CHANCE OF SURFACE LOWS TRACKING
THROUGH THESE AREAS. FOR THE EASTERN AND CENTRAL CONUS, THE 8-14 DAY OUTLOOK
LEANED AWAY FROM THE GEFS REFORECAST TOOL WHICH FAVORS ABOVE-NORMAL
PRECIPITATION FROM THE ROCKIES TO THE EAST COAST. THE ANALOG TOOL DERIVED FROM
THE 500-HPA HEIGHT BLEND SUPPORTS HEDGING AWAY FROM THE WETTER GEFS SOLUTION.
THE 7-DAY MEAN SURFACE FLOW FAVORS A CONTINUATION OF LAKE-EFFECT SNOW AND
ABOVE-NORMAL PRECIPITATION IS SLIGHTLY FAVORED DOWNWIND OF LAKES ERIE AND
ONTARIO.
DOWNSTREAM OF A BROAD TROUGH, ENHANCED SOUTHERLY FLOW FAVORS ABOVE-NORMAL
TEMPERATURES AND ABOVE-NORMAL PRECIPITATION FOR NEARLY ALL OF ALASKA. BASED ON
THE STRENGTH AND PERSISTENCE OF THE ONSHORE FLOW, ABOVE-NORMAL TEMPERATURE
PROBABILITIES EXCEED 60 PERCENT ACROSS SOUTHERN MAINLAND ALASKA.
BASED ON THE GEFS AND ECENS, INCREASED CHANCES OF ABOVE-NORMAL TEMPERATURES ARE
FORECAST FOR HAWAII WITH ABOVE-NORMAL PRECIPITATION FAVORED EXCEPT FOR THE
WESTERN ISLANDS.
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, DUE TO
CONTINUED GOOD AGREEMENT AMONG THE TEMPERATURE TOOLS OFFSET BY CONFLICTING GEFS
(WETTER) AND ECENS (DRIER) REFORECAST TOOLS FOR THE CENTRAL AND EASTERN CONUS.
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 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:
19551212 - 19631114 - 20051203 - 19611208 - 19561203
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:
20051203 - 19631114 - 19611208 - 19551211 - 19801202
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 04 - 08 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A B NRN CALIF A B
SRN CALIF A B IDAHO A B NEVADA A B
W MONTANA A A E MONTANA A A 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 B KANSAS A B OKLAHOMA A B
N TEXAS A A S TEXAS A A W TEXAS A A
MINNESOTA N A IOWA N B MISSOURI N B
ARKANSAS A N LOUISIANA A A WISCONSIN B N
ILLINOIS B B MISSISSIPPI A N MICHIGAN B A
INDIANA B N OHIO B N KENTUCKY B N
TENNESSEE B N ALABAMA N N 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 N W VIRGINIA B N
MARYLAND B N DELAWARE B N VIRGINIA B N
N CAROLINA B N S CAROLINA B N GEORGIA B N
FL PNHDL B N FL PENIN B N AK N SLOPE B B
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
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 06 - 12 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N OREGON A B NRN CALIF A B
SRN CALIF A B IDAHO A N NEVADA A B
W MONTANA A N E MONTANA A A WYOMING A N
UTAH A B ARIZONA A B COLORADO A N
NEW MEXICO A N N DAKOTA A A S DAKOTA A A
NEBRASKA A N KANSAS A N OKLAHOMA A N
N TEXAS A A S TEXAS A A W TEXAS A A
MINNESOTA N N IOWA N N MISSOURI N B
ARKANSAS A N LOUISIANA A A WISCONSIN B N
ILLINOIS B B MISSISSIPPI A N MICHIGAN B N
INDIANA B B OHIO B N KENTUCKY B B
TENNESSEE B B ALABAMA N N 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 N W VIRGINIA B N
MARYLAND B N DELAWARE B N VIRGINIA B N
N CAROLINA B N S CAROLINA B N GEORGIA N N
FL PNHDL N N FL PENIN N N AK N SLOPE A B
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.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page