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FXUS06 KWBC 181911
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT MON SEPTEMBER 18 2023
6-10 DAY OUTLOOK FOR SEP 24 - 28 2023
TODAY’S GFS, ECMWF, AND CANADIAN ENSEMBLE MEAN 500-HPA HEIGHT FORECASTS ARE IN
GOOD AGREEMENT OVER THE FORECAST DOMAIN DURING THE 6-10 DAY FORECAST PERIOD.
THE MANUAL 500-HPA HEIGHT BLEND DEPICTS A TROUGH EXTENDING FROM THE BERING SEA
AND WESTERN ALASKA SOUTHEASTWARD OVER THE GULF OF ALASKA, WITH WELL
BELOW-AVERAGE HEIGHTS (AT LEAST -150 METERS) INDICATED OVER THE GULF OF ALASKA.
A LOW-AMPLITUDE RIDGE IS FORECAST SOUTH OF THE WESTERN ALEUTIANS. THE FLOW
PATTERN SPLITS OVER THE INTERIOR OF WESTERN NORTH AMERICA, WITH THE NORTHERN
BRANCH OF THE WESTERLIES MOVING UP AND OVER AN AMPLIFIED MID-LEVEL RIDGE OVER
MOST OF CANADA, AND THE SOUTHERN BRANCH OF THE WESTERLIES EVOLVING INTO A
WESTERN RIDGE/EASTERN TROUGH PATTERN ACROSS THE LOWER 48 STATES. EARLY AUTUMN
IS THE TIME OF YEAR WHEN THE ATMOSPHERIC CIRCULATION TYPICALLY BECOMES MORE
ENERGETIC, AND FASTER-MOVING SHORTWAVE TROUGHS EMBEDDED IN THE MEAN FLOW BECOME
MORE CHALLENGING TO FORECAST.
THE CALIBRATED-REFORECAST TEMPERATURE TOOLS FROM THE THREE ENSEMBLE MEANS SHOW
CONSIDERABLE DIFFERENCES TODAY, SO THE CONSOLIDATED AND AUTOMATED TEMPERATURE
TOOLS WERE SUBJECTIVELY CONSIDERED MORE HEAVILY IN THE 6-10 DAY MANUAL
TEMPERATURE OUTLOOK. OVER THE CONUS, ODDS FAVOR ABOVE NORMAL TEMPERATURES FOR
MOST AREAS WEST OF THE CONTINENTAL DIVIDE, IN ADVANCE OF A MID-LEVEL TROUGH
NEARING THE WEST COAST. THE EXCEPTION INCLUDES SOUTHEASTERN CALIFORNIA, AND
NEIGHBORING PARTS OF NEVADA AND ARIZONA WHERE PREDICTED 500-HPA HEIGHT
ANOMALIES CLOSE TO NORMAL TILT THE ODDS TOWARDS NEAR NORMAL TEMPERATURES. ABOVE
NORMAL TEMPERATURES ARE ALSO FAVORED ACROSS MOST AREAS EAST OF THE CONTINENTAL
DIVIDE, WITH THE EXCEPTION OF PORTIONS OF KANSAS AND OKLAHOMA, WHERE NEAR
NORMAL TEMPERATURES ARE FAVORED. PROBABILITIES FAVORING ABOVE NORMAL
TEMPERATURES EXCEED 60% OVER PORTIONS OF THE NORTHERN TIER OF STATES,
ASSOCIATED WITH THE LARGE CANADIAN RIDGE AND SIGNIFICANTLY ABOVE NORMAL 500-HPA
HEIGHTS. WEAKER PROBABILITIES FAVORING ABOVE NORMAL TEMPERATURES ARE INDICATED
ACROSS THE SOUTHEAST WHERE MID-LEVEL HEIGHT ANOMALIES ARE FORECAST TO BE CLOSE
TO NORMAL. FOR ALASKA, BELOW NORMAL TEMPERATURE CHANCES ARE ELEVATED OVER
SOUTHWESTERN PORTIONS OF THE STATE, IN PROXIMITY TO A MID-LEVEL TROUGH AND
ANOMALOUSLY COOL SEA SURFACE TEMPERATURES.
THERE ARE ELEVATED CHANCES OF ABOVE NORMAL PRECIPITATION OVER WASHINGTON,
OREGON, NORTHERN CALIFORNIA, AND NORTHWESTERN NEVADA, IN ADVANCE OF AN
APPROACHING MID-LEVEL TROUGH. WITH THE RIDGE FORECAST OVER THE WEST-CENTRAL
CONUS DURING THE 6-10 DAY PERIOD, BELOW NORMAL PRECIPITATION CHANCES ARE
ENHANCED, EXTENDING EASTWARD ALONG THE NORTHERN TIER STATES INTO THE UPPER
GREAT LAKES REGION. ABOVE NORMAL PRECIPITATION CHANCES ARE ENHANCED ACROSS MOST
OF THE REMAINDER OF THE EASTERN HALF OF THE CONUS. A SUBTROPICAL LOW PRESSURE
SYSTEM IS PREDICTED TO DEVELOP OFF THE EAST COAST OF FLORIDA DURING THE NEXT
FEW DAYS. THIS SYSTEM IS EXPECTED TO BRING HEAVY RAIN AND GUSTY, ONSHORE WINDS
TO THE CAROLINAS AND MID-ATLANTIC COAST. CHANCES FOR ABOVE NORMAL PRECIPITATION
EXCEED 50% OVER THIS REGION. IN ALASKA, ODDS FAVOR ABOVE NORMAL PRECIPITATION
OVER SOUTHEASTERN PORTIONS OF THE STATE, IN PROXIMITY TO THE DEEP ANOMALOUS
TROUGH PREDICTED OVER THE GULF OF ALASKA. BELOW NORMAL PRECIPITATION CHANCES
ARE ENHANCED OVER WESTERN AND NORTHERN PORTIONS OF ALASKA, WELL ENOUGH REMOVED
FROM THE STORMINESS FOCUSED OVER THE SOUTHEASTERN PORTION OF THE STATE.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 33% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 34% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 8, AND 33% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY
8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: NEAR AVERAGE, 3 OUT OF 5, DUE TO
SIGNIFICANT DIFFERENCES AMONG TEMPERATURE AND PRECIPITATION TOOLS, ASSOCIATED
WITH AN ENERGETIC CIRCULATION PATTERN.
8-14 DAY OUTLOOK FOR SEP 26 - OCT 02, 2023
THE PREDICTED WEEK-2 500-HPA CIRCULATION PATTERN IS SIMILAR TO THAT ANTICIPATED
DURING THE EARLIER 6-10 DAY PERIOD, THOUGH MORE DE-AMPLIFIED. A MID-LEVEL
TROUGH IS FORECAST OVER THE BERING SEA AND WESTERN ALASKA, WITH FAST WESTERLY
FLOW ACROSS MUCH OF THE NORTH PACIFIC OCEAN. TROUGHING IS EXPECTED JUST OFF THE
WEST COASTS OF CANADA AND THE LOWER 48 STATES, WITH THE FLOW BEGINNING TO
DIVERGE OVER THE INTERIOR PORTION OF WESTERN NORTH AMERICA. THE NORTHERN BRANCH
HEADS UP INTO CANADA, WHILE THE SOUTHERN BRANCH EVOLVES DOWNSTREAM INTO A
TROUGH-RIDGE-TROUGH PATTERN ACROSS THE CONTIGUOUS U.S. (CONUS). ACROSS THE
SOUTHWESTERN CONUS, THE CLIMATOLOGICAL MONSOON SEASON IS DRAWING TO A CLOSE. A
MAJOR CONTRIBUTOR TO THE MONSOON IS THE SUBTROPICAL RIDGE, WHICH IS NOW SHIFTED
WELL SOUTHWARD OVER MEXICO AND ADJACENT PORTIONS OF THE EASTERN PACIFIC.
ABOVE NORMAL TEMPERATURE CHANCES ARE FAVORED FOR MOST OF THE LOWER 48 STATES,
CONSISTENT WITH THE CALIBRATED-REFORECAST TEMPERATURE TOOLS FROM THE THREE
ENSEMBLE MEANS. BELOW NORMAL TEMPERATURES ARE FAVORED OVER SOUTHEASTERN
CALIFORNIA AND ADJACENT PARTS OF NEVADA, WHERE PREDICTED 500-HPA HEIGHT
ANOMALIES ARE EXPECTED TO BE CLOSE TO AVERAGE. BELOW NORMAL TEMPERATURES ARE
ALSO ANTICIPATED OVER SOUTHWESTERN ALASKA, IN PROXIMITY TO RELATIVELY COOL
SEA-SURFACE TEMPERATURES AND A NEARBY MID-LEVEL TROUGH. WEAK RIDGING AND ABOVE
NORMAL 500-HPA HEIGHTS LEAD TO ABOVE NORMAL TEMPERATURES BEING FAVORED OVER
NORTHEASTERN ALASKA.
ABOVE NORMAL PRECIPITATION CHANCES ARE INDICATED OVER SOUTHEAST ALASKA,
WASHINGTON, OREGON, NORTHERN AND CENTRAL CALIFORNIA, AND NORTHWESTERN NEVADA,
IN ADVANCE OF A MID-LEVEL TROUGH APPROACHING FROM THE PACIFIC. PROBABILITIES
FAVORING ABOVE NORMAL PRECIPITATION EXCEED 50% OVER SOUTHWESTERN OREGON AND
PORTIONS OF NORTHERN CALIFORNIA. THERE ARE SLIGHTLY TILTED ODDS FOR ABOVE
NORMAL PRECIPITATION CONTINUING EASTWARD OVER THE NORTHERN AND CENTRAL ROCKIES,
MUCH OF THE GREAT PLAINS, SOUTH-CENTRAL MISSISSIPPI VALLEY, TENNESSEE VALLEY,
SOUTHEAST, MID-ATLANTIC REGION, SOUTHEASTERN NEW YORK STATE, AND PARTS OF
SOUTHERN NEW ENGLAND. THIS IS CONSISTENT WITH THE AUTOMATED AND CONSOLIDATED
PRECIPITATION TOOLS. BELOW NORMAL PRECIPITATION CHANCES ARE DEPICTED OVER PARTS
OF THE NORTHERN PLAINS, UPPER MISSISSIPPI VALLEY, AND UPPER GREAT LAKES REGION,
IN PROXIMITY TO THE LARGE ANOMALOUS RIDGE OVER CANADA. BELOW NORMAL
PRECIPITATION CHANCES ARE ALSO ELEVATED OVER MUCH OF THE WESTERN HALF OF
ALASKA, FAR ENOUGH REMOVED FROM THE STORMY CONDITIONS EXPECTED OVER THE
PANHANDLE REGION.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 33% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 34% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 11, AND 33% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON
DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: NEAR AVERAGE, 3 OUT OF 5, DUE TO
CONTINUING DIFFERENCES AMONG THE SURFACE TEMPERATURE AND PRECIPITATION GUIDANCE.
FORECASTER: ANTHONY A
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 21.
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:
19870916 - 20010924 - 19620926 - 19870911 - 19960912
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:
19870914 - 20010923 - 19870919 - 20010902 - 20090927
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 24 - 28 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A A
SRN CALIF N N IDAHO A N NEVADA A N
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A B ARIZONA A N COLORADO A B
NEW MEXICO A B N DAKOTA A B S DAKOTA A N
NEBRASKA A N KANSAS N A OKLAHOMA N A
N TEXAS A A S TEXAS A A W TEXAS A A
MINNESOTA A B IOWA A A MISSOURI A A
ARKANSAS A A LOUISIANA A A WISCONSIN A N
ILLINOIS A A MISSISSIPPI A A MICHIGAN A N
INDIANA A A OHIO A A KENTUCKY A A
TENNESSEE A A ALABAMA A A 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 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 N AK N SLOPE N N
AK ALEUTIAN B N AK WESTERN B B AK INT BSN N B
AK S INT N N AK SO COAST N N AK PNHDL N A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 26 - OCT 02, 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF N A
SRN CALIF B N IDAHO A A NEVADA N A
W MONTANA A N E MONTANA A N WYOMING A N
UTAH A N ARIZONA A N COLORADO A N
NEW MEXICO A N N DAKOTA A N S DAKOTA A N
NEBRASKA A A KANSAS A N OKLAHOMA A N
N TEXAS A N S TEXAS A N W TEXAS A N
MINNESOTA A B IOWA A N MISSOURI A N
ARKANSAS A N LOUISIANA A N WISCONSIN A B
ILLINOIS A B MISSISSIPPI A N MICHIGAN A B
INDIANA A N OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A N NEW YORK A N
VERMONT A N NEW HAMP A N MAINE A N
MASS A N CONN A N RHODE IS A N
PENN A N NEW JERSEY A N W VIRGINIA A N
MARYLAND A N DELAWARE A N VIRGINIA A N
N CAROLINA A A S CAROLINA A A GEORGIA A A
FL PNHDL A N FL PENIN A N AK N SLOPE N N
AK ALEUTIAN B N AK WESTERN B B AK INT BSN N N
AK S INT N N AK SO COAST N N 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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