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FXUS06 KWBC 061902
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 06 2023
6-10 DAY OUTLOOK FOR SEP 12 - 16 2023
TODAY’S MODEL SOLUTIONS REMAIN IN GOOD AGREEMENT REGARDING AN AMPLIFIED 500-HPA
GEOPOTENTIAL HEIGHT PATTERN ACROSS NORTH AMERICA DURING DAYS 6 THROUGH 10.
TROUGHING IS FORECAST ACROSS MUCH OF MAINLAND ALASKA AND THE ALEUTIANS WITH
RIDGING PREDICTED TO BUILD ACROSS THE NORTHWESTERN CONUS. DOWNSTREAM, TROUGHING
IS FORECAST ACROSS THE EASTERN CONUS, WITH SOME POTENTIAL INTERACTION WITH
TROPICAL STORM LEE, CURRENTLY OVER THE CENTRAL ATLANTIC. TODAY’S MANUAL 500-HPA
HEIGHT BLEND FOR THE 6-10 DAY PERIOD DEPICTS BELOW-NORMAL HEIGHTS ACROSS MUCH
OF ALASKA, WITH THE EXCEPTIONS OF THE FAR WESTERN ALEUTIANS AND THE EXTREME
NORTHERN MAINLAND WHERE ABOVE-NORMAL HEIGHTS ARE FAVORED DUE TO MID-LEVEL
RIDGING PREDICTED OVER THE NORTH-CENTRAL PACIFIC AND THE ARCTIC OCEAN. OVER THE
CONUS, NEAR- TO ABOVE (BELOW) NORMAL HEIGHTS ARE GENERALLY PREDICTED ACROSS THE
WEST (EAST) DUE TO THE DEVELOPING RIDGE-TROUGH PATTERN.
THE UNCALIBRATED 00Z GEFS, ECMWF, AND CANADIAN ENSEMBLES INITIALLY DEPICT BELOW
NORMAL TEMPERATURES OVER THE GREAT PLAINS AND MIDWEST, WITH THE WEATHER
PREDICTION CENTER FORECASTING MAXIMUM TEMPERATURE ANOMALIES OF -5 TO -10 DEG F
OVER PARTS OF THESE AREAS ON DAYS 6 AND 7. THESE COOLER TEMPERATURES ARE
FORECAST TO REACH PORTIONS OF THE MID-ATLANTIC AND NORTHEAST BY THE END OF THE
PERIOD, WITH A WARMING TREND FAVORED UPSTREAM OVER THE NORTHERN PLAINS AND
UPPER MISSISSIPPI VALLEY. AS A RESULT, A LARGE REGION OF INCREASED BELOW-NORMAL
TEMPERATURE PROBABILITIES IS INDICATED OVER MUCH OF THE EASTERN CONUS. THE
LARGEST PROBABILITIES (GREATER THAN 50 PERCENT) ARE OVER THE CENTRAL PLAINS,
MIDDLE MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS, AND THE SOUTHERN GREAT LAKES.
INCREASED PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES REMAIN FAVORED ACROSS
SOUTH TEXAS, ALONG THE GULF OF MEXICO COAST, AND THE SOUTHEAST, CONSISTENT WITH
THE GEFS AND ECMWF REFORECAST TOOLS. PROBABILITIES FOR ABOVE-NORMAL
TEMPERATURES ARE ELEVATED OVER MUCH OF THE WESTERN CONUS AND EXTENDING INTO THE
NORTHERN PLAINS UNDERNEATH INCREASING RIDGING. FOR ALASKA, INCREASED TROUGHING
FAVORS NEAR- TO BELOW-NORMAL TEMPERATURES OVER THE SOUTHERN HALF OF THE STATE,
WITH POSITIVE HEIGHT ANOMALIES OVER THE ARCTIC OCEAN LEADING TO INCREASED
CHANCES FOR ABOVE-NORMAL TEMPERATURES ACROSS THE NORTHERN AND EASTERN MAINLAND.
A FRONTAL SYSTEM IS FORECAST TO MOVE ACROSS THE EASTERN AND SOUTHERN TIERS OF
THE CONUS EARLY IN THE PERIOD FAVORING INCREASED CHANCES FOR ABOVE-NORMAL
PRECIPITATION OVER PARTS OF THE ROCKIES AND GREAT PLAINS, AND EXTENDING THROUGH
THE ATLANTIC COASTAL REGION. FURTHER ENHANCEMENT OF PRECIPITATION IS POSSIBLE
ACROSS PORTIONS OF THE NORTHEAST AND NEW ENGLAND DEPENDING ON THE EVENTUAL
TRACK OF TROPICAL STORM LEE. BELOW-NORMAL PRECIPITATION PROBABILITIES ARE
INCREASED ACROSS PORTIONS OF THE NORTHERN PLAINS, UPPER MISSISSIPPI VALLEY, AND
GREAT LAKES, ON THE BACKSIDE OF TROUGHING AND UNDERNEATH NORTHERLY MID-LEVEL
FLOW. PROBABILITIES FOR BELOW-NORMAL PRECIPITATION ARE ALSO INCREASED ACROSS
THE FLORIDA PENINSULA, FAR ENOUGH DISPLACED FROM THE MEAN TROUGHING, AND ACROSS
THE NORTHWEST, DUE TO EXPANDING RIDGING. SOME INCREASED ONSHORE FLOW, COMBINED
WITH VERY LOW PRECIPITATION CLIMATOLOGY, FAVORS A SLIGHT TILT TOWARD ELEVATED
PROBABILITIES OF ABOVE-NORMAL PRECIPITATION ACROSS THE CENTRAL CALIFORNIA
COAST, SUPPORTED BY THE GEFS AND ECMWF REFORECAST TOOLS. TROUGHING FORECAST
ACROSS ALASKA, ALONG WITH SURFACE LOW PRESSURE, FAVOR INCREASED SOUTHERLY FLOW
AND ELEVATED NEAR- TO ABOVE-NORMAL PRECIPITATION PROBABILITIES ACROSS THE
STATE, WITH THE LARGEST PROBABILITIES FOR ABOVE-NORMAL PRECIPITATION FORECAST
ACROSS SOUTHEAST ALASKA.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 30% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 5% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON
DAY 8, 30% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, 5% OF
TODAY'S OPERATIONAL 0Z ECMWF 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, DUE TO
A PERSISTENT SYNOPTIC PATTERN AND GOOD AGREEMENT AMONG FORECAST MODELS, OFFSET
BY WEAKENING OF THE HIGH AMPLITUDE PATTERN LATE IN THE FORECAST PERIOD AND
UNCERTAINTY REGARDING THE TRACK OF TROPICAL STORM LEE.
8-14 DAY OUTLOOK FOR SEP 14 - 20 2023
ENSEMBLE MEAN SOLUTIONS FOR THE 8-14 DAY PERIOD PREDICT A FAIRLY PERSISTENT
500-HPA GEOPOTENTIAL HEIGHT PATTERN ACROSS NORTH AMERICA AND SURROUNDING
REGIONS. THE WEEK-2 MANUAL 500-HPA HEIGHT BLEND DEPICTS RIDGING AND POSITIVE
500-HPA HEIGHT ANOMALIES ACROSS THE WESTERN AND NORTH-CENTRAL CONUS, AND A WEAK
TROUGH AND SLIGHTLY BELOW-NORMAL 500-HPA HEIGHTS ACROSS MUCH OF THE EASTERN
CONUS. STRONGER RIDGING IS DEPICTED OVER PORTIONS OF NORTHEASTERN CANADA,
INDICATIVE OF A DEVELOPING NEGATIVE NORTH ATLANTIC OSCILLATION (NAO). TROUGHING
AND NEGATIVE 500-HPA HEIGHT ANOMALIES ARE FAVORED ACROSS MOST OF ALASKA, WITH
THE EXCEPTIONS OF THE FAR WESTERN ALEUTIANS AND EXTREME NORTHERN MAINLAND WHERE
ABOVE-NORMAL HEIGHTS REMAIN FAVORED.
THE TEMPERATURE PATTERN FORECAST FOR THE WEEK 2 PERIOD IS SIMILAR TO THE 6-10
DAY OUTLOOK PERIOD. THERE ARE ENHANCED PROBABILITIES OF ABOVE NORMAL
TEMPERATURES ACROSS MUCH OF THE WESTERN AND NORTH-CENTRAL CONUS, ASSOCIATED
WITH RIDGING. THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES (GREATER
THAN 60 PERCENT) ARE INDICATED OVER EASTERN OREGON. ABOVE-NORMAL TEMPERATURES
ARE ALSO FORECAST OVER MOST OF CENTRAL AND SOUTHERN TEXAS, ALONG THE GULF OF
MEXICO COAST, AND THE SOUTHEAST, CONSISTENT WITH THE GEFS AND ECMWF REFORECAST
TOOLS. CONVERSELY, CHANCES FOR BELOW-NORMAL TEMPERATURES REMAIN ELEVATED FOR
PORTIONS OF THE CENTRAL AND EASTERN CONUS UNDERNEATH WEAK TROUGHING AND
CONSISTENT WITH A DEVELOPING NEGATIVE NAO. THE EXCEPTION IS OVER PARTS OF NEW
ENGLAND WHERE INCREASED MID-LEVEL SOUTHERLY FLOW AHEAD OF MEAN TROUGHING
COMBINED WITH INCREASING POSITIVE 500-HPA HEIGHT ANOMALIES COULD RESULT IN A
SLIGHT WARMING TREND, FAVORING A TILT TOWARD INCREASED ABOVE-NORMAL TEMPERATURE
PROBABILITIES. IN ALASKA, CHANCES FOR ABOVE-NORMAL TEMPERATURES ARE INCREASED
ACROSS MUCH OF THE MAINLAND, WHILE INCREASED PROBABILITIES FOR NEAR- TO
BELOW-NORMAL TEMPERATURES ARE FORECAST OVER PORTIONS OF THE ALEUTIANS AND
SOUTHEAST ALASKA, SUPPORTED BY MOST DYNAMICAL MODELS AND FORECAST TOOLS.
NEAR- TO BELOW-NORMAL PRECIPITATION PROBABILITIES ARE INCREASED FOR MOST OF THE
WESTERN CONUS, UNDER POSITIVE 500-HPA HEIGHT ANOMALIES AND RIDGING FORECAST
OVER THE REGION. SOME INCREASED ONSHORE FLOW ACROSS COASTAL CENTRAL CALIFORNIA
TILTS THE ODDS IN FAVOR OF ABOVE-NORMAL PRECIPITATION DUE TO THE VERY DRY
CLIMATOLOGY IN THAT REGION. AS IN THE 6-10 DAY PERIOD, INCREASED PROBABILITIES
OF BELOW-NORMAL PRECIPITATION REMAIN FAVORED ACROSS PORTIONS OF THE UPPER
MIDWEST, WITH INCREASED CHANCES FOR ABOVE-NORMAL PRECIPITATION OVER PARTS OF
THE CENTRAL AND SOUTHERN ROCKIES AND PLAINS, AND ALONG THE EASTERN SEABOARD.
ANY IMPACTS FROM TROPICAL STORM LEE OR ITS INTERACTION WITH A FRONTAL SYSTEM
ARE FORECAST TO OCCUR EARLY IN THE WEEK-2 PERIOD, WITH A TREND TOWARD DRIER
WEATHER ON THE BACKSIDE OF THE SYSTEM.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 30% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 40% 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: AVERAGE, 3 OUT OF 5, DUE TO GOOD
AGREEMENT AMONG MODEL ENSEMBLES ON THE PERSISTENT SYNOPTIC PATTERN, OFFSET BY
WEAKER ANOMALIES REDUCING FORECAST CONFIDENCE, ALONG WITH CONTINUED UNCERTAINTY
RELATED TO TROPICAL STORM LEE.
FORECASTER: THOMAS COLLOW
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:
19610919 - 19590827 - 20050914 - 19900826 - 19850917
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:
20050916 - 19590828 - 19610919 - 19900828 - 19850917
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 12 - 16 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A B
SRN CALIF N N IDAHO A B NEVADA A N
W MONTANA A B E MONTANA A B WYOMING A A
UTAH A A ARIZONA A A COLORADO B A
NEW MEXICO A A N DAKOTA A B S DAKOTA N N
NEBRASKA B A KANSAS B A OKLAHOMA B A
N TEXAS B A S TEXAS A A W TEXAS B A
MINNESOTA N B IOWA B B MISSOURI B N
ARKANSAS B A LOUISIANA A A WISCONSIN B B
ILLINOIS B N MISSISSIPPI A A MICHIGAN B N
INDIANA B N OHIO B A KENTUCKY B N
TENNESSEE B A ALABAMA A A NEW YORK B A
VERMONT N A NEW HAMP N A MAINE N A
MASS N A CONN N A RHODE IS N A
PENN B A NEW JERSEY B A W VIRGINIA B A
MARYLAND B A DELAWARE B A VIRGINIA B A
N CAROLINA B A S CAROLINA N A GEORGIA A N
FL PNHDL A N FL PENIN A B AK N SLOPE A N
AK ALEUTIAN B N AK WESTERN N N AK INT BSN A A
AK S INT N A AK SO COAST N A AK PNHDL B A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 14 - 20 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A N
SRN CALIF N N IDAHO A B NEVADA A B
W MONTANA A B E MONTANA A B WYOMING A N
UTAH A N ARIZONA A N COLORADO A A
NEW MEXICO A A N DAKOTA A N S DAKOTA A N
NEBRASKA A N KANSAS N A OKLAHOMA B A
N TEXAS A A S TEXAS A N W TEXAS A A
MINNESOTA A B IOWA A B MISSOURI B N
ARKANSAS B N LOUISIANA A N WISCONSIN A B
ILLINOIS B B MISSISSIPPI A N MICHIGAN N B
INDIANA B B OHIO B B KENTUCKY B N
TENNESSEE B N ALABAMA B N NEW YORK N A
VERMONT N A NEW HAMP N A MAINE A A
MASS N A CONN N A RHODE IS N A
PENN B N NEW JERSEY B A W VIRGINIA B N
MARYLAND B A DELAWARE B A VIRGINIA B N
N CAROLINA B N S CAROLINA B N GEORGIA B N
FL PNHDL A N FL PENIN A N AK N SLOPE A N
AK ALEUTIAN B N AK WESTERN A N AK INT BSN A N
AK S INT A 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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