840
FXUS06 KWBC 071902
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 07 2023
6-10 DAY OUTLOOK FOR SEP 13 - 17 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 ALASKA WITH RIDGING PREDICTED ACROSS THE
NORTHWESTERN CONUS. DOWNSTREAM, TROUGHING IS FORECAST ACROSS THE EASTERN CONUS,
WITH SOME POTENTIAL INTERACTION WITH HURRICANE 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 EXCEPTION OF THE FAR
WESTERN ALEUTIANS WHERE ABOVE-NORMAL HEIGHTS ARE FAVORED DUE TO MID-LEVEL
RIDGING PREDICTED OVER THE NORTH-CENTRAL PACIFIC. 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 DEPICT BELOW NORMAL
TEMPERATURES OVER PARTS OF THE EASTERN AND CENTRAL CONUS, WITH THE WEATHER
PREDICTION CENTER GENERALLY FORECASTING MAXIMUM TEMPERATURE ANOMALIES OF -5 TO
-10 DEG F ON DAYS 6 AND 7. A WARMING TREND IS FAVORED OVER THE NORTHERN AND
CENTRAL PLAINS AND UPPER MIDWEST AS THE LARGEST NEGATIVE TEMPERATURE ANOMALIES
SHIFT MORE INTO THE MID-ATLANTIC AND NORTHEAST BY THE SECOND HALF OF THE
PERIOD. 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 60 PERCENT) ARE OVER THE MIDDLE MISSISSIPPI,
TENNESSEE, AND OHIO VALLEYS. 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 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 HURRICANE LEE. THE 00Z ECMWF ENSEMBLE REMAINS THE MOST CONCERNING WITH
A CLUSTER OF MEMBERS SHOWING LEE IMPACTING EASTERN NEW ENGLAND, WHILE THE 00Z
GEFS AND CANADIAN ENSEMBLES LARGELY DEPICT TRACKS REMAINING OUT TO SEA.
BELOW-NORMAL PRECIPITATION PROBABILITIES ARE INCREASED ACROSS PORTIONS OF THE
UPPER MISSISSIPPI VALLEY, GREAT LAKES, TENNESSEE VALLEY, AND OHIO VALLEY ON THE
BACKSIDE OF TROUGHING AND UNDERNEATH NORTHERLY MID-LEVEL FLOW. PROBABILITIES
FOR BELOW-NORMAL PRECIPITATION ARE ALSO INCREASED ACROSS THE SOUTHERN FLORIDA
PENINSULA, FAR ENOUGH DISPLACED FROM THE MEAN TROUGHING, AND ACROSS THE
NORTHWEST, INTERIOR CALIFORNIA, WESTERN NEVADA, AND SOUTHWESTERN ARIZONA 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 HURRICANE LEE.
8-14 DAY OUTLOOK FOR SEP 15 - 21 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. TROUGHING
AND BELOW-NORMAL 500-HPA HEIGHTS ARE INDICATED ACROSS MUCH OF THE EASTERN
CONUS, WITH POSITIVE HEIGHT ANOMALIES FORECAST OVER EASTERN CANADA. THE
ORIENTATION OF THE TROUGH IN THE EAST FAVORS HURRICANE LEE TURNING NORTH, BUT
THE STRENGTH OF THE RIDGING ACROSS EASTERN CANADA WILL PLAY A ROLE INTO WHETHER
OR NOT THE TRACK BENDS MORE WESTWARD TOWARD EASTERN NEW ENGLAND AND ATLANTIC
CANADA (ECMWF) OR REMAINS FURTHER OUT TO SEA (GEFS AND CANADIAN). TROUGHING AND
NEGATIVE 500-HPA HEIGHT ANOMALIES ARE FAVORED ACROSS MOST OF ALASKA, WITH THE
EXCEPTIONS OF THE FAR WESTERN ALEUTIANS 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. ABOVE-NORMAL TEMPERATURES ARE ALSO FORECAST OVER MOST OF TEXAS,
ALONG THE GULF OF MEXICO COAST, AND FLORIDA, CONSISTENT WITH THE GEFS AND ECMWF
REFORECAST TOOLS. CONVERSELY, CHANCES FOR BELOW-NORMAL TEMPERATURES REMAIN
ELEVATED FOR PORTIONS OF THE EASTERN CONUS UNDERNEATH WEAK TROUGHING. THE GEFS
REFORECAST TOOL DEPICTS HIGHER PROBABILITIES OF ABOVE NORMAL TEMPERATURES
SPREADING INTO PORTIONS OF THE EAST-CENTRAL CONUS, BUT TILTED NEAR- TO
BELOW-NORMAL GIVEN THE RELATIVELY COOLER ECMWF REFORECAST TOOL AND UNCALIBRATED
GUIDANCE. ELEVATED ABOVE-NORMAL TEMPERATURE PROBABILITIES ACROSS NEW ENGLAND
ARE MAINLY RELATED TO ABOVE-NORMAL OVERNIGHT TEMPERATURES DUE TO THE ENHANCED
POTENTIAL FOR INCREASED CLOUD COVER AND PRECIPITATION. IN ALASKA, CHANCES FOR
ABOVE-NORMAL TEMPERATURES ARE INCREASED ACROSS MUCH OF THE MAINLAND, WHILE
INCREASED PROBABILITIES FOR NEAR-NORMAL TEMPERATURES ARE FORECAST OVER PORTIONS
OF SOUTHWEST 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 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 HURRICANE 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. TROUGHING CONTINUES TO FAVOR ELEVATED PROBABILITIES FOR
NEAR- TO ABOVE-NORMAL PRECIPITATION ACROSS ALASKA.
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 HURRICANE 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:
20050918 - 19590827 - 20000908 - 19900828 - 19610919
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:
19590829 - 20050916 - 19750829 - 19900828 - 20000908
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 13 - 17 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 N
W MONTANA A B E MONTANA A B WYOMING A A
UTAH A A ARIZONA A N COLORADO N A
NEW MEXICO A A N DAKOTA A N S DAKOTA A N
NEBRASKA N A KANSAS B A OKLAHOMA B A
N TEXAS B A S TEXAS A A W TEXAS A A
MINNESOTA A B IOWA B B MISSOURI B B
ARKANSAS B N LOUISIANA A N WISCONSIN B B
ILLINOIS B B MISSISSIPPI B N MICHIGAN B B
INDIANA B B OHIO B B KENTUCKY B B
TENNESSEE B N ALABAMA B N NEW YORK B A
VERMONT N A NEW HAMP N A MAINE N A
MASS N A CONN B 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 B A GEORGIA B 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 N
AK S INT N A AK SO COAST N A AK PNHDL B A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 15 - 21 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A N
SRN CALIF B N IDAHO A B NEVADA A N
W MONTANA A B E MONTANA A B WYOMING A N
UTAH A N ARIZONA A B COLORADO A A
NEW MEXICO A A N DAKOTA A B S DAKOTA A N
NEBRASKA A N KANSAS N A OKLAHOMA N A
N TEXAS A A S TEXAS A N W TEXAS A A
MINNESOTA A N IOWA A N MISSOURI N N
ARKANSAS N N LOUISIANA A N WISCONSIN A B
ILLINOIS N B MISSISSIPPI A N MICHIGAN N B
INDIANA B B OHIO B B KENTUCKY B B
TENNESSEE B N ALABAMA B N NEW YORK N N
VERMONT A A NEW HAMP A A MAINE A A
MASS N A CONN N A RHODE IS N A
PENN B B NEW JERSEY N A W VIRGINIA B B
MARYLAND B N 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 N N AK WESTERN N A AK INT BSN A A
AK S INT A A AK SO COAST A 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.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page