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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 TUE AUGUST 27 2024
6-10 DAY OUTLOOK FOR SEP 02 - 06 2024
BY LABOR DAY, AN AMPLIFIED 500-HPA TROUGH IS FORECAST TO BRING A BRIEF PERIOD
OF BELOW-NORMAL TEMPERATURES TO MUCH OF THE EASTERN AND SOUTH-CENTRAL
CONTIGUOUS U.S. (CONUS). THE 6-10 DAY TEMPERATURE OUTLOOK REFLECTS THIS WITH
BELOW-NORMAL TEMPERATURES MOST LIKELY ACROSS THE CENTRAL TO SOUTHERN GREAT
PLAINS, MIDWEST, MID-ATLANTIC, AND NORTHEAST. FARTHER TO THE SOUTH ALONG THE
GULF COAST AND ACROSS FLORIDA, ABOVE-NORMAL TEMPERATURES ARE FAVORED AS COLD
AIR ADVECTION IS NOT EXPECTED TO REACH THESE AREAS. AN AMPLIFIED 500-HPA RIDGE
FAVORS ABOVE-NORMAL TEMPERATURES THROUGHOUT THE WESTERN CONUS ALONG WITH THE
NORTHERN GREAT PLAINS. BY DAY 10, SEPTEMBER 6, THE GEFS, ECENS, AND CMCE AGREE
THAT A WARMING TREND BEGINS TO OVERSPREAD THE MIDWEST AS THE MID-LEVEL TROUGH
SHIFTS WELL TO THE EAST AND IS REPLACED BY A BUILDING RIDGE ALOFT.
ON DAYS 6 AND 7 (SEPTEMBER 2 AND 3), A COLD FRONT IS FORECAST TO PROGRESS
SLOWLY SOUTHWARD AND PROVIDE THE FOCUS FOR DAILY CONVECTION. ALTHOUGH THERE ARE
MINOR DIFFERENCES ON HOW QUICKLY THE COLD FRONT PUSHES SOUTHWARD IN TIME, THE
6-10 DAY OUTLOOK FAVORS ABOVE-NORMAL PRECIPITATION ACROSS THE SOUTHERN GREAT
PLAINS, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST. SOUTHEASTERLY FLOW, ALONG AND
TO THE NORTH OF A FRONT, RESULTS IN ELEVATED ABOVE-NORMAL PRECIPITATION
PROBABILITIES FOR THE UPPER RIO GRANDE VALLEY, MUCH OF NEW MEXICO, AND SOUTHERN
COLORADO. TO THE NORTH OF THE FRONT AND WITH AN EXPANDING MID-LEVEL RIDGE
PREDICTED, BELOW-NORMAL PRECIPITATION IS FAVORED FOR THE NORTHERN AND CENTRAL
GREAT PLAINS, MIDDLE AND UPPER MISSISSIPPI VALLEY, GREAT LAKES, AND NORTHEAST.
MULTI-MODEL ENSEMBLE MEANS DEPICT A 500-HPA TROUGH OVER THE GULF OF ALASKA
WHICH IS EXPECTED TO PROMOTE PERIODS OF ONSHORE FLOW AND FAVORS ABOVE-NORMAL
PRECIPITATION IN THE RELATIVELY DRY CLIMATOLOGICAL AREAS OF THE PACIFIC
NORTHWEST.
THE GEFS, ECENS, AND CMCE AGREE THAT A 500-HPA TROUGH PERSISTS OVER MAINLAND
ALASKA WHICH FAVORS NEAR TO ABOVE-NORMAL PRECIPITATION FOR THE STATE. BASED ON
GOOD AGREEMENT BETWEEN THE GEFS AND ECMWF REFORECAST TOOLS, A 2-CATEGORY CHANGE
(BELOW TO ABOVE) WAS NECESSARY FROM YESTERDAY. THE 6-10 DAY TEMPERATURE OUTLOOK
GENERALLY FOLLOWS THE GEFS AND ECMWF REFORECAST TOOLS AND DEPICTS INCREASED
CHANCES FOR BELOW (ABOVE)-NORMAL PROBABILITIES ACROSS COASTAL WESTERN ALASKA
AND THE ALEUTIANS (EASTERN MAINLAND ALASKA AND SOUTHEASTERN ALASKA).
BASED ON THE GEFS AND ECENS, ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR HAWAII.
AS OF AUGUST 27, THREE TROPICAL CYCLONES (HONE, GILMA, AND HECTOR) ARE ONGOING
ACROSS THE CENTRAL PACIFIC. ALL THREE ARE EXPECTED TO MOVE AWAY FROM HAWAII OR
DISSIPATE BY DAY 6, SEPTEMBER 2. THEREFORE, ELEVATED BELOW-NORMAL PRECIPITATION
PROBABILITIES ARE FORECAST FOR HAWAII.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 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 30% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY
8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: FORECAST CONFIDENCE: ABOVE
AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT ON THE DAILY EVOLUTION OF THE
500-HPA HEIGHT PATTERN AND TEMPERATURE/PRECIPITATION TOOLS.
8-14 DAY OUTLOOK FOR SEP 04 - 10 2024
THE GEFS, ECENS, AND CMCE ARE IN EXCELLENT AGREEMENT AND DEPICT A BROAD,
AMPLIFIED 500-HPA RIDGE OVER WESTERN AND CENTRAL NORTH AMERICA. THE RIDGE AXIS
EXTENDS FROM THE DESERT SOUTHWEST NORTHEASTWARD TO THE NORTHERN GREAT PLAINS.
THE GEFS AND ECENS FEATURE 500-HPA HEIGHTS OF 588 DAM AS FAR NORTH AS NEBRASKA
AND 582 DAM HEIGHTS TO THE U.S.-CANADA BORDER WHICH IS HIGHLY ANOMALOUS FOR
EARLY SEPTEMBER. GIVEN THE UNUSUALLY STRONG 500-HPA RIDGE, ENHANCED
ABOVE-NORMAL TEMPERATURE PROBABILITIES ARE FORECAST FOR THE WESTERN AND
NORTH-CENTRAL CONUS. A TWO-CATEGORY CHANGE (BELOW TO ABOVE-NORMAL TEMPERATURES)
FROM THE 6-10 TO 8-14 DAY OUTLOOK WAS MADE TO THE MIDWEST, AS
COOLER-THAN-NORMAL TEMPERATURES TIME OFF EARLY IN WEEK-2. BASED ON THE
REFORECAST TOOLS ALONG WITH PREDICTED EASTERLY SURFACE FLOW, BELOW-NORMAL
TEMPERATURES ARE MOST LIKELY FROM MID-ATLANTIC AND SOUTHERN APPALACHIANS NORTH
TO SOUTHERN NEW ENGLAND.
THE WEEK-2 PRECIPITATION OUTLOOK IS BASED ON THE CONSOLIDATION (SKILL-WEIGHTED
COMBINATION OF GEFS AND ECMWF REFORECASTS) AND UNCALIBRATED MODEL OUTPUT. A
STATIONARY FRONT MAY LINGER NEAR THE GULF COAST AND OVER THE SOUTHEAST THROUGH
THE BEGINNING OF WEEK-2. ALSO, THE TAIL END OF A MID-LEVEL TROUGH IS EXPECTED
TO EXTEND SOUTHWEST INTO THE SOUTHEASTERN CONUS. THESE TWO FACTORS ALONG WITH
THE CONSOLIDATION SUPPORT ELEVATED ABOVE-NORMAL PRECIPITATION PROBABILITIES
ACROSS PARTS OF TEXAS, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST. DUE TO THE
EXPANSIVE MID-LEVEL RIDGE ALOFT, BELOW-NORMAL PRECIPITATION IS FAVORED FOR A
MAJORITY OF THE CONUS, INCLUDING THE NORTHEAST, MIDWEST, NORTHERN TO CENTRAL
GREAT PLAINS, AND INTERIOR WEST. ALTHOUGH PERIODS OF ONSHORE FLOW FAVOR
ABOVE-NORMAL PRECIPITATION ACROSS THE PACIFIC NORTHWEST, THE GEFS AND ECENS
DEPICT 7-DAY PRECIPITATION AMOUNTS OF 0.5 INCH OR LESS.
SINCE THE LONGWAVE PATTERN REMAINS QUITE STABLE WITH A 500-HPA AXIS OVER
MAINLAND ALASKA, THE 6-10 AND 8-14 DAY TEMPERATURE AND PRECIPITATION OUTLOOKS
ARE SIMILAR.
BASED ON THE GEFS AND ECENS, NEAR TO ABOVE-NORMAL TEMPERATURES AND BELOW-NORMAL
PRECIPITATION ARE FAVORED FOR HAWAII.
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: FORECAST CONFIDENCE: ABOVE
AVERAGE, 4 OUT OF 5, DUE TO GOOD MODEL AGREEMENT AND CONSISTENCY.
FORECASTER: BRAD PUGH
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 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:
20050905 - 20050823 - 19980818 - 19980807 - 19520825
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:
20050904 - 20050826 - 19980806 - 19830813 - 20020902
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 02 - 06 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A N
SRN CALIF A B IDAHO A A NEVADA A B
W MONTANA A N E MONTANA A B WYOMING A N
UTAH A N ARIZONA A B COLORADO A A
NEW MEXICO B A N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS B B OKLAHOMA B A
N TEXAS B A S TEXAS B A W TEXAS B A
MINNESOTA A B IOWA B B MISSOURI B B
ARKANSAS B A LOUISIANA A A WISCONSIN B B
ILLINOIS B B MISSISSIPPI N A MICHIGAN B B
INDIANA B B OHIO B B KENTUCKY B B
TENNESSEE B A ALABAMA A A NEW YORK B B
VERMONT B B NEW HAMP B B MAINE B B
MASS B B CONN B B RHODE IS B B
PENN B B NEW JERSEY B B W VIRGINIA B B
MARYLAND B B DELAWARE B N VIRGINIA B A
N CAROLINA B A S CAROLINA B A GEORGIA A A
FL PNHDL A A FL PENIN A A AK N SLOPE A N
AK ALEUTIAN B N AK WESTERN N N AK INT BSN A N
AK S INT A A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 04 - 10 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A N NRN CALIF A N
SRN CALIF A N IDAHO A B NEVADA A B
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A B ARIZONA A B COLORADO A N
NEW MEXICO A N N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS A B OKLAHOMA N B
N TEXAS N N S TEXAS A A W TEXAS N N
MINNESOTA A B IOWA A B MISSOURI N B
ARKANSAS N N LOUISIANA A A WISCONSIN A B
ILLINOIS N B MISSISSIPPI N A MICHIGAN A B
INDIANA N B OHIO N B KENTUCKY N N
TENNESSEE N N ALABAMA N A NEW YORK N B
VERMONT A B NEW HAMP N B MAINE A B
MASS B B CONN B B RHODE IS B B
PENN B B NEW JERSEY B B W VIRGINIA B B
MARYLAND B B DELAWARE B B VIRGINIA B N
N CAROLINA B A S CAROLINA B A GEORGIA B A
FL PNHDL A A FL PENIN A A AK N SLOPE A N
AK ALEUTIAN B N AK WESTERN N N AK INT BSN A N
AK S INT A A AK SO COAST A A AK PNHDL A 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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