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FXUS06 KWBC 141903
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT THU SEPTEMBER 14 2023
6-10 DAY OUTLOOK FOR SEP 20 - 24 2023
THE 6 TO 10 DAY HEIGHT FORECAST MAINTAINS TWO STRONG POSITIVE HEIGHT ANOMALY
CENTERS OVER AND NEAR NORTH AMERICA. THE FIRST, A RELATIVELY FLAT RIDGE,
CENTERED NEAR THE ALEUTIANS AND STRETCHING ACROSS MUCH OF THE NORTH PACIFIC.
THE SECOND, MORE MERIDIONAL, OVER THE HUDSON BAY EXTENDING SOUTH INTO THE GREAT
LAKES AND NORTHEAST. IN THE WESTERN CONTIGUOUS U.S. (CONUS) WEAKLY NEGATIVE
500-HPA HEIGHT ANOMALIES LEAD TO SLIGHT TROUGHING IN THE REGION. NEAR TO
NEGATIVE 500-HPA HEIGHT ANOMALIES STRETCH INTO PARTS OF THE SOUTH-CENTRAL AND
SOUTHEASTERN CONUS. SIMILARLY, NEAR TO NEGATIVE 500-HPA HEIGHT ANOMALIES ARE
FORECAST ACROSS MUCH OF MAINLAND ALASKA.
THE TEMPERATURE OUTLOOK FOR THE PERIOD IS VERY SIMILAR TO PREVIOUS FORECASTS.
THE BIGGEST CHANGE IS THE EXPANSION OF STRONGER PROBABILITIES FOR ABOVE-NORMAL
TEMPERATURES ALONG THE EASTERN SEABOARD. ABOVE-NORMAL TEMPERATURES NOW COVER
MUCH OF EASTERN CONUS EXCLUDING PARTS OF SOUTH CAROLINA AND GEORGIA. IN THE
WESTERN CONUS, BELOW-NORMAL TEMPERATURES REMAIN FAVORED WEST OF THE CONTINENTAL
DIVIDE. HOWEVER, AS THE NEGATIVE 500-HPA HEIGHT ANOMALIES ARE SLIGHTLY WEAKER,
PROBABILITIES ARE NOT QUITE AS STRONG AS YESTERDAY. RAW AND BIAS CORRECTED
TOOLS ARE GENERALLY SLIGHTLY WARMER RELATIVE TO PRIOR FORECASTS. IN ALASKA,
BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS MUCH OF THE STATE SOUTH OF THE
BROOKS RANGE.
ABOVE-NORMAL PRECIPITATION IS FAVORED ACROSS MUCH OF THE WESTERN CONUS INTO THE
ROCKY MOUNTAINS, PLAINS AND MISSISSIPPI VALLEY DURING THE 6 TO 10 DAY PERIOD
AHEAD OF THE 500-HPA TROUGH ACROSS THE WESTERN CONUS. ENSEMBLE TOOLS INDICATE
THAT AN AREA OF LOW-PRESSURE MAY EJECT OUT OF THE ROCKY MOUNTAINS AND TRACK
NORTHEAST THROUGH THE PLAINS BRINGING ENHANCED CHANCES FOR ABOVE-NORMAL
PRECIPITATION. BENEATH THE STRONG POSITIVE 500-HPA HEIGHT ANOMALIES ACROSS THE
GREAT LAKES AND NORTHEAST, BELOW-NORMAL PRECIPITATION IS FAVORED. ENSEMBLES
CONTINUE TO INDICATE ABOVE-NORMAL PRECIPITATION ACROSS THE SOUTHERN ATLANTIC
STATES. IN THE SOUTHWEST, BELOW-NORMAL PRECIPITATION IS FAVORED WITH FEW
CHANCES FOR ANY GULF OF CALIFORNIA SURGE EVENTS AND A SUBTROPICAL RIDGE TO THE
SOUTH LIMITING MOISTURE INTO THE REGION. IN ALASKA, ONSHORE FLOW INTO ALASKA
BRINGS CHANCES FOR ABOVE-NORMAL PRECIPITATION TO MUCH OF THE STATE. THE
STRONGEST PROBABILITIES ARE ACROSS PARTS OF THE COPPER RIVER BASIN INTO
SOUTHEAST ALASKA WITH NEAR-NORMAL FAVORED NORTH OF THE BROOKS RANGE.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 25% 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
CONFIDENCE IN THE HEIGHT ANOMALY CENTERS ACROSS THE HUDSON BAY AND NORTH
PACIFIC IS OFFSET BY CONCERN OVER THE PATTERN IN THE WESTERN CONUS.
8-14 DAY OUTLOOK FOR SEP 22 - 28 2023
THE WEEK-2 HEIGHT FORECAST IS SIMILAR TO THE 6 TO 10 DAY PATTERN. TWO POSITIVE
500-HPA HEIGHT ANOMALIES REMAIN CENTERED NEAR THE ALEUTIAN ISLANDS AND THE
HUDSON BAY. THE POSITIVE 500-HPA HEIGHT ANOMALY CENTERED ACROSS THE HUDSON BAY
IS STRONGER RELATIVE TO THE EARLIER PERIOD AND EXTENDS ACROSS MUCH OF THE
EASTERN CONUS. MEANWHILE, THE 500-HPA HEIGHT ANOMALY AREA CENTERED ON THE
ALEUTIAN ISLANDS IS SLIGHTLY WEAKER RELATIVE TO PRIOR FORECASTS AND THE 6 TO 10
DAY PERIOD. THE WEAK TROUGH ACROSS THE WESTERN CONUS IS FORECAST TO BE SLIGHTLY
MORE AMPLIFIED RELATIVE TO PRIOR FORECASTS AND HAS RETROGRADED SLIGHTLY TO BE
CENTERED OVER COASTAL BRITISH COLUMBIA. NEAR-NORMAL 500-HPA HEIGHTS ARE FAVORED
ACROSS MOST OF ALASKA.
BELOW-NORMAL TEMPERATURES REMAIN FAVORED ACROSS THE WESTERN CONUS DURING THE
WEEK-2 PERIOD BENEATH A NEGATIVE 500-HPA HEIGHT ANOMALY. ACROSS MUCH OF THE
EASTERN CONUS, ABOVE-NORMAL TEMPERATURES ARE FAVORED. THE STRONGEST
PROBABILITIES ARE CENTERED ACROSS THE GREAT LAKES NEAREST STRONG POSITIVE
500-HPA HEIGHT ANOMALIES OVER THE HUDSON BAY. WEAKER PROBABILITIES REMAIN ALONG
PORTIONS OF THE SOUTHERN ATLANTIC STATES WHERE LINGERING COOLER AIR AT THE
ONSET OF THE PERIOD REDUCES CHANCES FOR ABOVE-NORMAL TEMPERATURES. MEANWHILE,
IN ALASKA, MUCH OF THE STATE REMAINS FAVORED FOR BELOW-NORMAL TEMPERATURES
SUPPORTED BY MOST OF THE TOOLS.
DUE TO THE PRIOR MENTIONED TROUGH OVER MUCH OF THE WESTERN CONUS RETROGRADING
SLIGHTLY NORTHWEST, STRONGER ONSHORE FLOW IS FORECAST ACROSS THE PACIFIC
NORTHWEST, INCREASING CHANCES FOR ABOVE-NORMAL PRECIPITATION INTO THE REGION.
THIS ENHANCED MOIST PACIFIC FLOW MAY ALSO HELP TO ENHANCE MOISTURE AND
PRECIPITATION ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS. BELOW-NORMAL
PRECIPITATION REMAINS FAVORED ACROSS PARTS OF THE NORTHEAST AHEAD OF THE
500-HPA RIDGE AXIS. IN THE SOUTHWEST, NEAR TO THE SUBTROPICAL HIGH,
BELOW-NORMAL PRECIPITATION IS FAVORED. IN ALASKA, DUE TO THE RETROGRADING
TROUGH, ENHANCED ONSHORE FLOW MAY RELAX SLIGHTLY ACROSS THE SOUTHEAST, LEADING
TO NEAR-NORMAL PRECIPITATION BEING FAVORED. HOWEVER, THIS IS AMONG THE WETTEST
TIMES OF THE YEAR FOR SOUTHEAST ALASKA AND PRECIPITATION IS STILL LIKELY.
ABOVE-NORMAL IS SLIGHTLY FAVORED FOR PORTIONS OF THE SOUTHWESTERN MAINLAND.
NEAR-NORMAL IS FAVORED ELSEWHERE ACROSS THE STATE.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 15% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 20% 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: ABOVE AVERAGE, 4 OUT OF 5, GOOD
CONFIDENCE IN THE HEIGHT ANOMALY CENTERS ACROSS THE HUDSON BAY AND NORTH
PACIFIC IS OFFSET BY CONCERN OVER THE PATTERN IN THE WESTERN CONUS AND HOW THAT
MAY IMPACT TEMPERATURE AND PRECIPITATION.
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
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:
20060908 - 20010923 - 19620924 - 20090912 - 20090827
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:
20060906 - 20090826 - 20010921 - 19620924 - 19530910
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 20 - 24 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B N OREGON B A NRN CALIF B N
SRN CALIF B N IDAHO B A NEVADA B A
W MONTANA B A E MONTANA N A WYOMING B A
UTAH B A ARIZONA B B COLORADO N A
NEW MEXICO A B 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 A
ARKANSAS A A LOUISIANA A N WISCONSIN A A
ILLINOIS A N MISSISSIPPI A N MICHIGAN A N
INDIANA A N OHIO A B KENTUCKY A B
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 B NEW JERSEY A B W VIRGINIA A B
MARYLAND A N DELAWARE A N VIRGINIA A N
N CAROLINA A N S CAROLINA N A GEORGIA N A
FL PNHDL N A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN N N AK WESTERN B A AK INT BSN B A
AK S INT B A AK SO COAST B A AK PNHDL B A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 22 - 28 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B A OREGON B A NRN CALIF B A
SRN CALIF B N IDAHO B A NEVADA B A
W MONTANA B A E MONTANA N A WYOMING B A
UTAH B A ARIZONA B N COLORADO A A
NEW MEXICO A N 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 N
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A A LOUISIANA A N WISCONSIN A A
ILLINOIS A A MISSISSIPPI A N MICHIGAN A A
INDIANA A A OHIO A N KENTUCKY A N
TENNESSEE A A 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 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 N N AK WESTERN B N AK INT BSN B N
AK S INT B N AK SO COAST B N AK PNHDL B N
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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