045
FXUS06 KWBC 131932
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT FRI SEPTEMBER 13 2024
6-10 DAY OUTLOOK FOR SEP 19 - 23 2024
THERE IS GOOD AGREEMENT BETWEEN THE ECMWF, GEFS AND CANADIAN ENSEMBLE MEAN
500-HPA HEIGHT FORECASTS ON AN AMPLIFIED CIRCULATION PATTERN ACROSS NORTH
AMERICA, VERY SIMILAR TO YESTERDAY. DYNAMICAL MODELS PREDICT A MID-LEVEL TROUGH
OVER THE BERING SEA AND MAINLAND ALASKA, EXTENDING SOUTHEASTWARD THROUGH
WESTERN CANADA AND THE WESTERN CONTIGUOUS U.S. (CONUS). DYNAMICAL MODELS
PREDICT WEAKENING ANOMALIES ASSOCIATED WITH THE TROUGH OVER THE WESTERN CONUS
TOWARDS THE END OF THE PERIOD. MEANWHILE, A HIGHLY AMPLIFIED RIDGE IS PREDICTED
OVER EASTERN CANADA AND THE NORTHEASTERN CONUS, WITH 500-HPA HEIGHT ANOMALIES
EXCEEDING +270 DM JUST EAST OF HUDSON BAY. SLIGHTLY NEGATIVE 500-HPA HEIGHT
ANOMALIES AND A TROUGH ARE PREDICTED OVER THE SOUTHEASTERN CONUS. THERE IS THE
POTENTIAL FOR SOME SORT OF TROPICAL OR SUBTROPICAL STORM TO DEVELOP OFF THE
SOUTHEAST COAST, BUT EXTENDED-RANGE MODELS (ESPECIALLY ENSEMBLE MEANS) ARE
INHERENTLY POOR IN HANDLING SUCH SYSTEMS, SO THERE IS A LOT OF UNCERTAINTY
REGARDING THIS POTENTIAL FEATURE. DYNAMICAL MODELS PREDICT WEAKENING ANOMALIES
ASSOCIATED WITH THE TROUGH OVER THE WESTERN CONUS TOWARDS THE END OF THE
PERIOD.
BELOW NORMAL TEMPERATURES ARE FAVORED FOR PARTS OF THE WESTERN TIER OF ALASKA
AND THE SOUTHWESTERN ALASKA MAINLAND, UNDER A PREDICTED TROUGH. NEAR NORMAL
TEMPERATURES ARE FAVORED FOR MOST OTHER PARTS OF THE STATE, EXCEPT
NORTH-CENTRAL AND NORTHEASTERN SECTIONS OF THE ALASKA MAINLAND, WHERE
ADOVE-NORMAL TEMPERATURES ARE EXPECTED UNDER ANOMALOUS SOUTHERLY FLOW. BELOW
NORMAL TEMPERATURES ARE LIKELY ACROSS MUCH OF THE WESTERN CONUS FROM CALIFORNIA
THROUGH THE INTERMOUNTAIN WEST AND MOST OF THE ROCKIES UNDER A PREDICTED
TROUGH, WITH SOME REDUCTION IN PROBABILITIES FROM YESTERDAY DUE THE
DEAMPLIFICATION OF THE TROUGH EXPECTED LATE IN THE PERIOD. ABOVE NORMAL
TEMPERATURES ARE LIKELY FOR MOST OF THE REMAINDER OF THE CONUS BENEATH A
MID-LEVEL RIDGE STRETCHING SOUTHWARD FROM THE LARGE POSITIVE 500-HPA ANOMALY IN
EASTERN CANADA. PROBABILITIES FOR ABOVE NORMAL TEMPERATURES EXCEED 80 PERCENT
FOR MUCH OF THE WESTERN GREAT LAKES REGION. TEMPERATURES ARE FORECAST TO
AVERAGE NEAR NORMAL IN PARTS OF THE SOUTHEAST. 500-HPA HEIGHTS ARE EXPECTED TO
BE NEAR OR SLIGHTLY BELOW NORMAL IN THIS REGION, AND EXPECTED ABOVE-NORMAL
PRECIPITATION (POSSIBLY ASSOCIATED WITH A TROPICAL OR SUBTROPICAL STORM SYSTEM)
SHOULD HELP KEEP TEMPERATURES DOWN AS WELL. ABOVE-NORMAL TEMPERATURES ARE
MARGINALLY FAVORED FOR THE HAWAIIAN ISLANDS, CONSISTENT WITH THE TEMPERATURE
CONSOLIDATION. 500-HPA ARE EXPECTED TO BE ABOVE NORMAL AT THE START OF THE
PERIOD OVER AND NEAR THE ISLAND CHAIN, DROPPING CLOSER TO NORMAL BY DAY 10.
ABOVE NORMAL PRECIPITATION IS SLIGHTLY FAVORED FOR MOST OF ALASKA, EXCLUDING
PARTS OF NORTHWESTERN MAINLAND ALASKA, CONSISTENT WITH DYNAMICAL MODEL
PRECIPITATION FORECASTS. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED FROM THE
UPPER MISSISSIPPI VALLEY AND GREAT PLAINS WESTWARD INTO THE INTERMOUNTAIN WEST,
IN ASSOCIATION WITH THE SLOWLY DEAMPLIFYING MID-LEVEL TROUGH OVER THE WESTERN
CONUS. BELOW NORMAL PRECIPITATION IS FAVORED FOR PARTS OF THE SOUTHWEST AND
NEAR THE COAST IN THE PACIFIC NORTHWEST UNDER CYCLONICALLY-CURVED MID-LEVEL
FLOW UPSTREAM FROM THE TROUGH. FARTHER EAST, DERIVED PRECIPITATION TOOLS ARE
CONSISTENT IN FAVORING SUBNORMAL PRECIPITATION IN THE NORTHEAST AND IN A BAND
FROM THE GREAT LAKES REGION SOUTHWARD THROUGH THE WESTERN GULF COAST REGION,
ESPECIALLY OVER NEW ENGLAND AND UPSTATE NEW YORK. ABOVE NORMAL PRECIPITATION IS
LIKELY FOR PARTS OF THE SOUTHEAST AND MID-ATLANTIC REGIONS, WITH SHOWERS AND
THUNDERSTORMS EXPECTED UNDER A WEAK MID-LEVEL TROUGH. TROPICAL OR SUBTROPICAL
STORM DEVELOPMENT IS POSSIBLE IN THIS REGION, WHICH WOULD ENHANCE RAINFALL,
ESPECIALLY NEAR THE COAST. THE CONSOLIDATION TOOL SLIGHTLY FAVORS WETTER THAN
NORMAL WEATHER ACROSS HAWAII, BUT RAW ENSEMBLE MEAN OUTPUT FROM THE ENSEMBLES
FAVOR SUBNORMAL RAINFALL IN THE WESTERN HALF OF THE BIG ISLAND. THE OUTLOOK IS
CONSISTENT WITH THESE TOOLS, FAVORING WETTER THAN NORMAL WEATHER EVERYWHERE
OUTSIDE THE WESTERN HALF OF THE BIG ISLAND, WHERE CONFLICTING TOOLS RESULTED IN
A FORECAST FOR NEAR NORMAL PRECIPITATION.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 25% OF TODAY'S GFS
SUPERENSEMBLE MEAN CENTERED ON DAY 8, 55% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 8, AND 20% 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 THE DYNAMICAL MODEL HEIGHT FORECASTS IN AN AMPLIFIED
PATTERN, OFFSET BY SOME DIFFERENCES IN THE TEMPERATURE AND PRECIPITATION TOOLS
AND UNCERTAINTIES ASSOCIATED WITH THE DEAMPLIFYING TROUGH IN THE WESTERN CONUS.
8-14 DAY OUTLOOK FOR SEP 21 - 27 2024
DYNAMICAL MODEL FORECASTS FROM THE ECMWF, GEFS AND CANADIAN ENSEMBLE MEANS ARE
IN DECENT AGREEMENT ON THE AVERAGE LARGE SCALE 500-HPA HEIGHT PATTERN IN THE
WEEK-2 PERIOD. GUIDANCE IS INCONSISTENT HANDLING THE EVOLUTION OF THE
DEAMPLIFYING MID-LEVEL TROUGH IN THE WESTERN CONUS, AND IN THE STRENGTH OF THE
MID-LEVEL TROUGHING EXPECTED TO SET UP OVER OR NEAR ALASKA. THERE ARE NO
COMPELLING REASONS TO FAVOR ONE MODEL OVER THE OTHERS REGARDING THE EVOLUTION
OF THE WESTERN CONUS TROUGH DEAMPLIFICATION, SO A COMPROMISE OF THE ENSEMBLE
MEANS IS FORECAST. FARTHER NORTHWEST, TELECONNECTIONS FAVOR A WEAKER TROUGH
NEAR ALASKA, WHICH IS CONSISTENT WITH FORECASTS FROM THE GEFS AND THE CANADIAN
ENSEMBLE MEANS. EVOLUTION OF THE UNSETTLED WEATHER PATTERN AND POTENTIAL
TROPICAL OR SUBTROPICAL STORM DEVELOPMENT IS UNCERTAIN, BUT SLOW WEAKENING IS
EXPECTED. OTHERWISE, BROADLY, THE MEAN PATTERN IS SIMILAR TO THE 6-10 DAY
PERIOD FORECASTS, WITH LITTLE CHANGE IN THE AMPLITUDE AND LOCATION OF THE LARGE
POSITIVE 500-HPA HEIGHT ANOMALIES CENTERED IN EASTERN CANADA AND EXTENDING
SOUTHWARD INTO THE EASTERN CONUS. ACROSS HAWAII, THE EUROPEAN AND CANADIAN
ENSEMBLE MEANS DEPICT 500-HPA HEIGHTS SLOWLY INCREASING, RETURNING TO THE
SLIGHTLY ABOVE NORMAL HEIGHTS BY THE END OF WEEK-2 SIMILAR TO THE EXPECTED
PATTERN ON DAY 6, WITH TEMPORARILY LOWERING HEIGHTS IN BETWEEN. THE GEFS IS NOT
IN AGREEMENT WITH THE OTHER TWO ENSEMBLE MEANS, KEEPING 500-HPA HEIGHTS CLOSER
TO NORMAL THROUGHOUT WEEK-2. THE SLOWLY-INCREASING HEIGHT PATTERN IS FAVORED,
GIVEN THE PREPONDERANCE OF THE GUIDANCE DEPICTING THIS EVOLUTION.
BELOW NORMAL TEMPERATURES ARE FAVORED FOR THE WEST COAST OF MAINLAND ALASKA AS
A PREDICTED TROUGH SETTLES OVER OR NEAR THE STATE. ABOVE NORMAL TEMPERATURES
ARE FAVORED FOR PARTS OF NORTHEASTERN MAINLAND ALASKA, UNDER ANOMALOUS
SOUTHERLY FLOW SIMILAR TO CONDITIONS PRIOR TO WEEK-2. WITH THE WESTERN CONUS
500-HPA TROUGH WEAKENING, TEMPERATURES ARE EXPECTED TO REBOUND TO NEAR OR ABOVE
NORMAL LEVELS FROM THE ROCKIES WESTWARD WHILE ABOVE-NORMAL TEMPERATURES PERSIST
ACROSS MOST OF THE EASTERN CONUS, WITH ODDS EXCEEDING 70 PERCENT ACROSS THE
GREAT LAKES REGION. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED MORE WEAKLY IN
THE SOUTHEAST AS UNSETTLED WEATHER BEGINS TO LOOSEN ITS GRIP ON THE REGION, BUT
MID-LEVEL HEIGHTS REMAIN NEAR OR SLIGHTLY BELOW NORMAL. ABOVE NORMAL
TEMPERATURES ARE ALSO FAVORED FOR THE HAWAIIAN ISLANDS OUTSIDE THE BIG ISLAND,
WHERE TEMPERATURES SHOULD AVERAGE CLOSER TO NORMAL. THIS IS CONSISTENT WITH THE
TEMPERATURE CONSOLIDATION AND A PREPONDERANCE OF THE ENSEMBLE MEANS.
ABOVE NORMAL PRECIPITATION IS SLIGHTLY FAVORED FOR MOST OF MAINLAND ALASKA IN
WEEK-2, UNDER AND AHEAD OF THE TROUGH EXPECTED TO DEVELOP. THE BEST CHANCES FOR
WETTER THAN NORMAL WEATHER ARE IN SOUTHEASTERN PARTS OF THE STATE, WHERE A
MOISTURE-RICH FETCH OF SURFACE AIR IS EXPECTED TO COINCIDE WITH
CYCLONICALLY-CURVED MID-LEVEL FLOW. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED
IN THE PACIFIC NORTHWEST, BUT THE DEAMPLIFYING TROUGH FARTHER EAST FAVORS NEAR
OR BELOW NORMAL PRECIPITATION THROUGH THE INTERMOUNTAIN WEST AND MOST OF THE
ROCKIES. WET CONDITIONS ARE FORECAST FOR CENTRAL AND SOUTHERN SECTIONS OF THE
PLAINS AND MISSISSIPPI VALLEY UPSTREAM FROM THE FADING MID-LEVEL TROUGH WITH
PREVAILING CONVERGENT SURFACE WINDS. BELOW NORMAL PRECIPITATION IS SLIGHTLY
FAVORED FOR SOUTHEASTERN TEXAS, AND IN THE NORTHEAST AND ADJACENT GREAT LAKES
REGION, BOTH CONSISTENT WITH THE CONSOLIDATION. OVER THE SOUTHEAST AND ADJACENT
MID-ATLANTIC REGIONS, ABOVE NORMAL PRECIPITATION CONTINUES TO BE FAVORED UNDER
A WEAK, MEANDERING MID-LEVEL LOW AND THE POSSIBILITY OF TROPICAL OR SUBTROPICAL
STORM DEVELOPMENT. ABOVE NORMAL PRECIPITATION IS SLIGHTLY FAVORED ACROSS MOST
OF HAWAII EXCEPT FOR PORTIONS OF THE BIG ISLAND, CONSISTENT WITH THE
CONSOLIDATION INFORMED BY THE RAW OUTPUT FROM THE ENSEMBLE MEANS.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 30% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 35% OF TODAY'S GFS SUPERENSEMBLE MEAN
CENTERED ON DAY 11, 15% 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: ABOUT-AVERAGE, 3 OUT OF 5, DUE TO
GOOD AGREEMENT AMONG THE DYNAMICAL MODEL HEIGHT FORECASTS AND GENERALLY
CONSISTENT TEMPERATURE AND PRECIPITATION TOOLS, OFFSET BY DIFFERENCES IN THE
EVOLUTION OF MID-LEVEL FEATURES NEAR ALASKA, OVER THE WESTERN CONUS, AND IN THE
SOUTHEAST.
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
SEPTEMBER 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:
20060828 - 20050824 - 20050903 - 20040919 - 20050829
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:
20050826 - 20040920 - 20050902 - 20060829 - 19680919
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 19 - 23 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON N N OREGON N N NRN CALIF B N
SRN CALIF B N IDAHO B A NEVADA B N
W MONTANA N A E MONTANA N A WYOMING B A
UTAH B A ARIZONA B B COLORADO B A
NEW MEXICO N 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 N W TEXAS A A
MINNESOTA A A IOWA A A MISSOURI A N
ARKANSAS A N LOUISIANA A B WISCONSIN A N
ILLINOIS A B MISSISSIPPI A B MICHIGAN A B
INDIANA A B OHIO A B KENTUCKY A N
TENNESSEE A N ALABAMA A N NEW YORK A B
VERMONT A B NEW HAMP A B MAINE A B
MASS A B CONN A B RHODE IS A B
PENN A N NEW JERSEY A N W VIRGINIA A A
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA N A GEORGIA N A
FL PNHDL N A FL PENIN A A AK N SLOPE A A
AK ALEUTIAN B N AK WESTERN B N AK INT BSN N A
AK S INT B A AK SO COAST B A AK PNHDL B A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 21 - 27 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A N
SRN CALIF N N IDAHO N N NEVADA N N
W MONTANA A N E MONTANA A N WYOMING A N
UTAH N B ARIZONA A B COLORADO A N
NEW MEXICO A N N DAKOTA A A S DAKOTA A A
NEBRASKA A A KANSAS A A OKLAHOMA A A
N TEXAS A N S TEXAS A B W TEXAS A N
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A N LOUISIANA A N WISCONSIN A N
ILLINOIS A N MISSISSIPPI A N MICHIGAN A N
INDIANA A N OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A A NEW YORK A B
VERMONT A B NEW HAMP A B MAINE A B
MASS A B CONN A B RHODE IS A B
PENN A N NEW JERSEY A N 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 A A
AK ALEUTIAN B N AK WESTERN N N AK INT BSN N A
AK S INT N A AK SO COAST N A AK PNHDL N 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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