601
FXUS06 KWBC 022101
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST MON DECEMBER 02 2024
6-10 DAY OUTLOOK FOR DEC 08 - 12 2024
MOST MODEL GUIDANCE INDICATES THAT A CHANGE IN THE 500-HPA PATTERN WILL START
TO EVOLVE DURING THIS PERIOD. BEYOND THAT, THE SITUATION IS HIGHLY UNCERTAIN,
WITH MODELS VERY INCONSISTENT FROM EACH OTHER AND FROM RUN-TO-RUN. THIS RESULTS
IN A LOW-CONFIDENCE FORECAST, WITH THE OFFICIAL TEMPERATURE AND PRECIPITATION
MAPS INCORPORATING THIS UNCERTAINTY, AND AREN’T MERELY REFLECTIONS OF THE
OFFICIAL MANUAL 500-HPA HEIGHT BLEND.
MODELS START THE 6-10 DAY PERIOD IN DECENT AGREEMENT ON THE LARGE-SCALE
PATTERN. A MODERATE TO STRONG MID-LEVEL RIDGE IS ALONG OR NEAR WESTERN NORTH
AMERICA. THERE IS A WEAK POSITIVELY-TILTED TROUGH DOWNSTREAM, WITH THE ANOMALY
CENTER OVER THE NORTHERN HIGH PLAINS. FARTHER EAST, A WEAK RIDGE IS FORECAST
OVER MOST OF THE EASTERN CONTIGUOUS UNITED STATES (CONUS) WHILE SUB-NORMAL
500-HPA HEIGHTS LINGER ACROSS NEW ENGLAND. MEANWHILE, A VERY STRONG MID-LEVEL
RIDGE IS FORECAST IN THE NORTH ATLANTIC OCEAN SOUTHEAST OF GREENLAND. THIS
FEATURE IS ABOUT THE ONLY ONE HANDLED FAIRLY CONSISTENTLY BY MOST GUIDANCE. BY
THE END OF THE 6-10 DAY PERIOD, THE MODELS HAVE DIVERGED SIGNIFICANTLY, AND
THERE IS POOR CONSENSUS ON THE PATTERN THAT BECOMES ESTABLISHED. IN THE
EUROPEAN ENSEMBLE (ECENS) MEAN, THE MID-LEVEL RIDGE NEAR WESTERN NORTH AMERICA
AND RETROGRADES INTO THE EAST-CENTRAL NORTH PACIFIC, WITH 500-HPA HEIGHT
ANOMALIES ABOVE 30 DM REACHING ONLY AS FAR EAST AS THE IMMEDIATE WEST COAST. IN
THE CANADIAN ENSEMBLE (CMCE) MEAN, THIS MID-LEVEL RIDGE IS CONSIDERABLY FARTHER
EAST AND SLIGHTLY WEAKER. THE LARGEST POSITIVE 500-HPA HEIGHT ANOMALIES ARE
JUST OFF THE PACIFIC NORTHWEST COAST, AND POSITIVE 500-HPA ANOMALIES REACH AS
FAR EAST AS THE GREAT PLAINS. THE ECENS MEAN, BEING FARTHER WEST WITH THE
MID-LEVEL RIDGE, ACTUALLY SHOWS A DOWNSTREAM TROUGH WITH AN AXIS THROUGH THE
PLAINS. THE CMCE MEAN PLACES THIS TROUGH IN THE NORTHEAST CONUS WITH A
CONSIDERABLY SMALLER WAVELENGTH, AS BOTH MODELS GENERALLY AGREE THAT THE STRONG
DOWNSTREAM MID-LEVEL RIDGE SOUTHEAST OF GREENLAND REMAINS APPROXIMATELY IN
PLACE, ALTHOUGH THE CMCE MEAN DEPICTS A SLIGHTLY WEAKER MID-LEVEL HEIGHT
ANOMALY CENTER THAT IS A LITTLE FARTHER SOUTHEAST COMPARED TO THE ECENS MEAN.
MEANWHILE, THE GEFS SOLUTION DIFFERS SIGNIFICANTLY FROM THE OTHER TWO ENSEMBLE
MEANS. IT SHOWS A MID-LEVEL RIDGE THAT IS MUCH WEAKER AND HAS RETROGRADED SINCE
DAY 6 INTO THE CENTRAL NORTH PACIFIC. IT SHOWS POSITIVE MID-LEVEL HEIGHT
ANOMALIES EXTENDING EASTWARD ACROSS THE SOUTHWESTERN QUARTER OF THE CONUS, WITH
A SECOND MAXIMUM ANOMALY CENTER OVER SOUTHERN CALIFORNIA. BUT INSTEAD OF A
RIDGE AXIS EXTENDING NORTHWARD, THE GEFS MEAN SHOWS A WEAK TROUGH AND NEGATIVE
500-HPA HEIGHT ANOMALIES NEAR SOUTHWESTERN CANADA. FARTHER EAST, THE GEFS MEAN
PLACES A VERY WEAK AND BROAD TROUGH ACROSS THE EASTERN HALF OF THE CONUS WHICH
LEADS INTO A DOWNSTREAM RIDGE SIMILAR TO THE OTHER TWO ENSEMBLE MEANS. LOOKING
AT TELECONNECTIONS ISN’T HELPFUL, AS THE PACIFIC MID-LEVEL RIDGE FAVORS A
CONSIDERABLY DIFFERENT REGIME THAN TELECONNECTIONS ON THE RIDGE SOUTHEAST OF
GREENLAND.
THE TEMPERATURE AND PRECIPITATION FORECASTS ARE BASED ON A GENERAL CONSENSUS OF
THE RAW, RE-FORECAST, BIAS-CORRECTED, AND CALIBRATED TEMPERATURE AND
PRECIPITATION OUTPUTS, AT LEAST WHERE THERE ARE AREAS OF AGREEMENT DESPITE THE
UNCERTAINTY OF THE MID-LEVEL FEATURES. COMPARED TO YESTERDAY, IT APPEARS THAT
SUBNORMAL TEMPERATURES IN THE EASTERN CONUS WILL BE PUSHED EASTWARD AWAY FROM
THE REGION MORE QUICKLY THAN FORECAST YESTERDAY. OTHER THAN THAT, THERE IS POOR
AGREEMENT AMONG THE GUIDANCE, AND SINCE THE PATTERN SHOULD BE TRANSITIONAL IN
ANY CASE, NEAR-NORMAL TEMPERATURES IN THE MEAN ARE ANTICIPATED. TEMPERATURE
GUIDANCE IS IN SLIGHTLY BETTER AGREEMENT OVER THE WESTERN CONUS. SLIGHTLY
ENHANCED ODDS FOR WARMER THAN NORMAL WEATHER ENCOMPASSES MOST OF THE AREA, WITH
SOMEWHAT BETTER ODDS FOR WARMTH IN THE FAR WEST AND IN THE CENTRAL AND NORTHERN
HIGH PLAINS JUST EAST OF THE ROCKIES, WHERE THE POTENTIAL FOR HIGH SURFACE
PRESSURE IN THE NORTHERN INTERMOUNTAIN WEST WOULD LEAD TO DOWNSLOPING SURFACE
FLOW AND POSSIBLE CHINOOK WINDS, WHICH WOULD INCREASE CHANCES FOR WARMTH THERE
CONSIDERABLY. NEAR THE WESTERN NORTH AMERICA RIDGE, MOST TOOLS STRONGLY FAVOR
WARMTH IN ALASKA, ESPECIALLY IN THE EASTERN MAINLAND AND SOUTHEASTERN SECTIONS.
FROM THE HIGH PLAINS TO THE EAST COAST, MOST GUIDANCE SHOWS THE POTENTIAL FOR
ONE OR MORE SURFACE STORMS TO DEVELOP. THE TRACKS, STRENGTH, AND TIMING OF ANY
STORMS THAT DEVELOP ARE HIGHLY UNCERTAIN, BUT THE OVERALL POTENTIAL FAVORS
ABOVE-NORMAL PRECIPITATION OVER THE NORTHERN, EASTERN, AND WESTERN TIERS OF
THIS REGION, WITH LESSER CHANCES FOR WETNESS ACROSS INTERIOR SECTIONS OF THE
CENTRAL AND EASTERN CONUS. FARTHER WEST, MOST GUIDANCE FAVORS SUBNORMAL
PRECIPITATION, BUT PRECIPITATION ANOMALY FORECASTS ARE HIGHLY INCONSISTENT,
RANGING FROM NEAR-NORMAL TO STRONGLY FAVORING DRYNESS. THE OFFICIAL FORECAST IS
A COMPROMISE, LEANING TOWARD DRYNESS IN THE WEST, BUT WITH CONSIDERABLY LOWER
ODDS THAN MANY TOOLS IMPLY. STRONG ZONAL TO SOUTHWESTERLY FLOW ENHANCES THE
LIKELIHOOD OF ABOVE-NORMAL PRECIPITATION OVER MOST OF THE STATE, WITH THE BEST
CHANCES ALONG THE SOUTHERN AND EASTERN TIERS SOUTH OF ALASKA RANGE.
HAWAII IS EXPECTED TO BE WARMER AND WETTER THAN NORMAL, PERHAPS SIGNIFICANTLY
SO, AS DEPICTED IN THE CONSOLIDATION.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 28% OF TODAY'S GFS
SUPERENSEMBLE MEAN CENTERED ON DAY 8, 28% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 8, 16% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8, AND
28% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: MUCH BELOW NORMAL, 1 OUT OF 5,
WITH A BROAD ARRAY OF GUIDANCE SOLUTIONS TEMPERED SLIGHTLY BY SOME AREAS OF
AGREEMENT IN THE TOOLS DERIVED FROM THE ENSEMBLES.
8-14 DAY OUTLOOK FOR DEC 10 - 16 2024
THE DIVERGENT MODEL SOLUTIONS NOTED DURING THE 6-10 DAY PERIOD CONTINUE THROUGH
WEEK-2. BY THE END OF THE PERIOD, THE ECENS FURTHER RETROGRADES A SIGNIFICANT
MID-LEVEL RIDGE AXIS TO THE SOUTHWEST OF ALASKA, DEPICTS A MODERATE MID-LEVEL
TROUGH OVER THE WESTERN CONUS, AND WEAK POSITIVE HEIGHT ANOMALIES DOWNSTREAM
ALONG THE EAST COAST WHICH EXTEND INTO A SIGNIFICANT MID-LEVEL RIDGE STILL
SOUTHEAST OF GREENLAND. THE CMCE MEAN PLACES A SIMILAR-LOOKING RIDGE FARTHER
EAST OFFSHORE FROM THE WESTERN CONUS, A WEAK DOWNSTREAM TROUGH EXTENDING FROM
HUDSON BAY SOUTHWESTWARD INTO THE PLAINS AND SOUTHWESTERN CONUS, AND
ABOVE-NORMAL 500-HPA HEIGHTS OVER THE NORTHEAST LEADING INTO A FLATTER RIDGE
EAST OF ATLANTIC CANADA. THE GEFS ALMOST ENTIRELY BREAKS DOWN THE RIDGE OVER
THE NORTH PACIFIC, WITH ABOVE-NORMAL 500-HPA HEIGHTS OVER SOUTHERN AND
ESPECIALLY EASTERN PORTIONS OF THE CONUS WHICH EXTEND INTO A FLAT RIDGE WITH
MODERATE ANOMALIES WELL SOUTH OF GREENLAND. TELECONNECTIONS REMAIN UNHELPFUL IN
DETERMINING A FAVORED SOLUTION, AS THE ANOMALIES MOST CONSISTENT IN THE
GUIDANCE IMPLY SIGNIFICANTLY DIFFERENT TEMPERATURE AND PRECIPITATION REGIMES.
ONCE AGAIN, A COMPROMISE IN THE HEIGHT FIELD IS FORECAST, WITH THE OFFICIAL
TEMPERATURE AND PRECIPITATION OUTLOOKS REFLECTING AREAS OF AGREEMENT AMONG THE
TOOLS DERIVED FROM THE ENSEMBLES.
ABOVE-NORMAL TEMPERATURES ARE AT LEAST SLIGHTLY FAVORED THROUGH ALMOST ALL OF
THE 50 STATES. THE BEST ODDS FOR ABOVE-NORMAL TEMPERATURES ONCE AGAIN COVER
EASTERN AND SOUTHEASTERN ALASKA. ENHANCED ODDS FOR WARMTH ARE MUCH LESS ROBUST
OVER THE CONUS, BASED ON THE LACK OF ANY APPARENT MECHANISM TO BRING COLD
CANADIAN AIR SOUTHWARD INTO THE CONUS. WET WEATHER IS EXPECTED TO CONTINUE
ACROSS MOST OF ALASKA, PARTICULARLY SOUTH OF THE ALASKAN RANGE. FARTHER SOUTH,
MARGINALLY INCREASED ODDS FOR ABOVE-NORMAL PRECIPITATION EXTEND ALONG MOST OF
THE NORTHERN, EASTERN, AND SOUTHERN TIERS OF THE CONUS, WITH SLIGHTLY INCREASED
CHANCES FOR SUBNORMAL PRECIPITATION EXTENDING FROM THE SOUTHWEST THROUGH THE
CENTRAL PLAINS AND INTO THE MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS. THE
CONSOLIDATION CONTINUES TO FAVOR ABOVE-NORMAL PRECIPITATION IN HAWAII.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 22% OF TODAY'S GFS
SUPERENSEMBLE MEAN CENTERED ON DAY 11, 56% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 11, AND 22% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON
DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: MUCH BELOW NORMAL, 1 OUT OF 5, DUE
TO INCONSISTENT MODEL GUIDANCE, INCLUDING RUN-TO-RUN DIFFERENCES IN INDIVIDUAL
MODELS.
FORECASTER: RICH TINKER
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:
19581211 - 19551127 - 19621209 - 19631216 - 20021130
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:
19581211 - 19551127 - 19621210 - 19631215 - 19761123
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 08 - 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 N
MINNESOTA A A IOWA A N MISSOURI A N
ARKANSAS A A LOUISIANA A A WISCONSIN N A
ILLINOIS N N MISSISSIPPI N A MICHIGAN N A
INDIANA N A OHIO N A KENTUCKY N A
TENNESSEE N A ALABAMA N A NEW YORK N A
VERMONT N A NEW HAMP N A MAINE N A
MASS N A CONN N A RHODE IS N A
PENN N A NEW JERSEY N A W VIRGINIA N A
MARYLAND N A DELAWARE N A VIRGINIA N A
N CAROLINA N A S CAROLINA N A GEORGIA N A
FL PNHDL N A FL PENIN A A AK N SLOPE A A
AK ALEUTIAN A A 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 10 - 16 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A N
SRN CALIF A B IDAHO A A NEVADA A N
W MONTANA A A E MONTANA A A WYOMING A A
UTAH A N ARIZONA A B COLORADO A N
NEW MEXICO A B N DAKOTA A A S DAKOTA A A
NEBRASKA A N KANSAS A N OKLAHOMA A B
N TEXAS A N S TEXAS A A W TEXAS A B
MINNESOTA N A IOWA A N MISSOURI A B
ARKANSAS A B LOUISIANA A A WISCONSIN N A
ILLINOIS A B MISSISSIPPI A N MICHIGAN A A
INDIANA A B OHIO A N KENTUCKY A B
TENNESSEE A B 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 A GEORGIA A N
FL PNHDL A A FL PENIN A A AK N SLOPE A N
AK ALEUTIAN A A 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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