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FXUS06 KWBC 271902
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT WED SEPTEMBER 27 2023
6-10 DAY OUTLOOK FOR OCT 03 - 07 2023
AN AMPLIFIED PATTERN REMAINS FORECAST ACROSS NORTH AMERICA TODAY, SIMILAR TO
PREVIOUS FORECASTS. STRONG POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST TO BE
CENTERED OVER SOUTHWEST ALASKA SPREADING ACROSS MUCH OF THE STATE. A SECOND
AREA OF STRONG POSITIVE 500-HPA HEIGHTS IS FORECAST IN EASTERN CANADA COVERING
MUCH OF EASTERN NORTH AMERICA. NEGATIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST
ACROSS WESTERN CANADA AND THE PACIFIC NORTHWEST. NEAR NORMAL 500-HPA HEIGHTS
ARE FORECAST ACROSS THE SOUTHERN TIER OF THE CONUS. THERE IS CONSIDERABLE
DISAGREEMENT IN THE ENSEMBLE MODELS IN THE EASTERN PACIFIC REGARDING THE
STRENGTH AND EVOLUTION OF THE TROUGH DURING THE FORECAST PERIOD.
STRONG CHANCES FOR ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS MOST OF THE
CONTIGUOUS U.S. (CONUS) EAST OF THE CONTINENTAL DIVIDE. THE LOWEST CHANCES ARE
ACROSS PORTIONS OF THE FLORIDA PENINSULA WHERE WEAK TROUGHING JUST OFF THE
COAST MAY REDUCE TEMPERATURES DURING THE PERIOD. ACROSS THE WESTERN CONUS,
BELOW-NORMAL TEMPERATURES ARE FAVORED WITH TROUGHING REMAINING ESTABLISHED
DURING THE 6-10 DAY PERIOD. THE STRONGEST CHANCES FOR BELOW-NORMAL TEMPERATURES
ARE IN THE PACIFIC NORTHWEST STRETCHING BACK INTO MUCH OF ALASKA. A SLIGHT TILT
TOWARDS ABOVE-NORMAL REMAINS FAVORED ACROSS THE WEST COAST OF ALASKA.
BELOW NORMAL PRECIPITATION IS FAVORED FOR THE NORTHEAST, MID-ATLANTIC AND
INTERIOR SOUTHEAST BENEATH STRONG POSITIVE 500-HPA HEIGHT ANOMALIES. ALONG THE
SOUTHEAST ATLANTIC COAST, NEAR-NORMAL IS FAVORED WHERE WEAK MID-LEVEL TROUGHING
MAY BRING MORE PRECIPITATION TO COASTAL REGIONS COMPARED TO THE INTERIOR
SOUTHEAST. ACROSS THE PLAINS, ABOVE-NORMAL PRECIPITATION IS FAVORED ALONG A
STATIONARY BOUNDARY AHEAD OF THE MID-LEVEL TROUGH ACROSS THE WESTERN CONUS.
LIKEWISE, ABOVE-NORMAL PRECIPITATION IS FAVORED IN THE NORTHWEST WHERE ONSHORE
FLOW MAY HELP TO MAINTAIN A WETTER WEATHER PATTERN. IN ALASKA, ABOVE-NORMAL
PRECIPITATION IS FAVORED ACROSS MUCH OF THE STATE, EXCLUDING SOUTH-CENTRAL AND
SOUTHEAST ALASKA WHERE BELOW-NORMAL IS SLIGHTLY FAVORED DUE MORE NORTHERLY FLOW
AS A RESULT OF THE STRONG POSITIVE HEIGHT ANOMALIES CENTERED OVER SOUTHWEST
ALASKA.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 30% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 8, 40% 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 5, GOOD
AGREEMENT AMONG THE ENSEMBLE GUIDANCE ON THE HEIGHT PATTERN INCREASES
CONFIDENCE OFFSET BY SOME DISAGREEMENT IN THE PACIFIC THAT COULD IMPACT THE
FORECAST.
8-14 DAY OUTLOOK FOR OCT 05 - 11 2023
THE MANUAL HEIGHT BLEND FOR THE 8 TO 14 DAY FORECAST PERIOD IS LESS AMPLIFIED
RELATIVE TO THE 6 TO 10 DAY PERIOD. HOWEVER, THIS IS LARGELY THE RESULT OF
DECREASED AGREEMENT AMONG THE ENSEMBLE GUIDANCE. SOME OF THE ENSEMBLE MEMBERS
ARE INDICATING CHANCES FOR A PATTERN CHANGE ACROSS THE DOMAIN HOWEVER, THE
MAJORITY FAVOR A CONTINUATION OF THE ONGOING PATTERN. DESPITE THE INCREASED
UNCERTAINTY, POSITIVE 500-HPA HEIGHT ANOMALIES REMAIN FORECAST ACROSS EASTERN
NORTH AMERICA AND ACROSS ALASKA AND THE NORTHEAST PACIFIC SIMILAR TO THE 6 TO
10 DAY PERIOD. SLIGHT NEGATIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST ACROSS THE
WESTERN CONUS LEADING TO FORECAST TROUGHING CONTINUING ACROSS THE REGION.
THE TEMPERATURE PATTERN REMAINS CONSISTENT WITH PRIOR FORECASTS AND THE 6 TO 10
DAY PERIOD, WITH STRONG CHANCES FOR ABOVE-NORMAL TEMPERATURE FORECAST ACROSS
THE EASTERN CONUS. PROBABILITIES ARE REDUCED IN THE FLORIDA PENINSULA DUE TO
CONTINUED CONCERNS OF A WEAK MID-LEVEL TROUGH DEVELOPING OFF THE SOUTHEAST
ATLANTIC COAST. IN THE WESTERN CONUS, PROBABILITIES ARE REDUCED RELATIVE TO THE
6 TO 10 DAY PERIOD AS UNCERTAINTY INCREASES IN THE EVOLUTION OF THE PATTERN BUT
BELOW-NORMAL TEMPERATURES REMAIN FAVORED IN THE REGION. IN ALASKA, BELOW-NORMAL
TEMPERATURES ARE FAVORED IN SOUTHEAST ALASKA AND THE EASTERN MAINLAND.
ABOVE-NORMAL IS FAVORED ACROSS THE WESTERN ALASKA COAST WHERE ONSHORE FLOW IS
FAVORED.
NEAR TO BELOW-NORMAL PRECIPITATION IS FAVORED ACROSS THE EASTERN THIRD OF THE
CONUS BENEATH POSITIVE 500-HPA HEIGHT ANOMALIES. THE STRONGEST PROBABILITIES
FOR BELOW-NORMAL PRECIPITATION ARE FAVORED ACROSS THE NORTHEAST. THERE IS
CONSIDERABLE UNCERTAINTY REGARDING A POTENTIAL MID-LEVEL TROUGH OFF THE
SOUTHEAST ATLANTIC COAST THAT MAY BRING PRECIPITATION TO THE REGION, THEREFORE,
NEAR-NORMAL IS FAVORED IN THE SOUTHEAST. ACROSS THE PLAINS AND WESTERN CONUS,
ABOVE-NORMAL PRECIPITATION IS GENERALLY FAVORED WITH WEAK TROUGHING PERSISTING
ACROSS THE WEST BRINGING INCREASED CHANCES FOR A STORM SYSTEM TO DEVELOP IN THE
LEE OF THE ROCKIES. MEANWHILE, IN THE NORTHWEST, ONSHORE FLOW IS LIKELY TO
DEVELOP BRINGING CONTINUED MOISTURE TO THE REGION. IN THE SOUTHWEST,
PRECIPITATION IS GENERALLY LIMITED AT THIS TIME OF YEAR AND MANY OF THE TOOLS
ARE CONFLICTED ON SLIGHTLY ABOVE OR BELOW PRECIPITATION, THEREFORE NEAR-NORMAL
IS FAVORED. IN ALASKA, WITH WEAKER POSITIVE 500-HPA HEIGHT ANOMALIES IN THE
NORTH PACIFIC, THIS COULD BRING MORE PRECIPITATION INTO PORTIONS OF SOUTHERN
ALASKA, RELATIVE TO THE 6 TO 10 DAY PERIOD. THEREFORE, A SLIGHT TILT TOWARDS
ABOVE-NORMAL IS FAVORED FOR MUCH OF MAINLAND ALASKA INCLUDING THE SOUTH-CENTRAL
COASTAL REGIONS. IN SOUTHEAST ALASKA, THE PATTERN GENERALLY CONTINUES TO FAVOR
DRIER THAN NORMAL CONDITIONS AND BELOW-NORMAL PRECIPITATION IS FAVORED EVEN AS
PRECIPITATION IS LIKELY TO OCCUR.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 11, 10% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 11, 40% 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: BELOW AVERAGE, 2 OUT OF 5,
INCREASED UNCERTAINTY IN THE EVOLUTION OF THE PATTERN DECREASES CONFIDENCE
DURING THE PERIOD. HOWEVER, GOOD AGREEMENT EARLY IN WEEK-2 HELPS TO OFFSET
THESE CONCERNS.
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
OCTOBER 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:
20010927 - 19620930 - 20071009 - 19841011 - 20081006
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:
20010927 - 20071010 - 19621002 - 19841010 - 20081005
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 03 - 07 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B A OREGON B A NRN CALIF N N
SRN CALIF B N IDAHO B A NEVADA B N
W MONTANA B A E MONTANA N A WYOMING N A
UTAH B N ARIZONA B N COLORADO A A
NEW MEXICO A 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 A W TEXAS A A
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A A LOUISIANA A N WISCONSIN A A
ILLINOIS A A MISSISSIPPI A B MICHIGAN A N
INDIANA A B OHIO A B KENTUCKY A B
TENNESSEE A B ALABAMA A B 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 B DELAWARE A B VIRGINIA A B
N CAROLINA A B S CAROLINA A B GEORGIA A B
FL PNHDL A B FL PENIN A N AK N SLOPE N A
AK ALEUTIAN N A AK WESTERN N A AK INT BSN B A
AK S INT B N AK SO COAST B N AK PNHDL B B
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 05 - 11 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 B A WYOMING B A
UTAH B N ARIZONA B N COLORADO A N
NEW MEXICO A 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 A W TEXAS A A
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A N LOUISIANA A N WISCONSIN A A
ILLINOIS A A MISSISSIPPI A N MICHIGAN A N
INDIANA A N OHIO A N 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 B NEW JERSEY A B W VIRGINIA A B
MARYLAND A N DELAWARE A N VIRGINIA A N
N CAROLINA A N S CAROLINA A N GEORGIA A N
FL PNHDL A N FL PENIN A N AK N SLOPE N A
AK ALEUTIAN A A AK WESTERN N A AK INT BSN B A
AK S INT B A AK SO COAST B A AK PNHDL B B
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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