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FXUS06 KWBC 281902
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT WED AUGUST 28 2024
6-10 DAY OUTLOOK FOR SEP 03 - 07 2024
DURING EARLY SEPTEMBER, THE GEFS AND ECENS SEEM TO BE CONVERGING ON A 500-HPA
HEIGHT PATTERN WITH A TROUGH OVER ALASKA, RIDGE CENTERED ACROSS THE ROCKIES,
AND A TROUGH OF VARYING AMPLITUDE OVER THE EASTERN CONTIGUOUS U.S. (CONUS).
GIVEN THE TIME OF YEAR, THE WAVELENGTHS ARE PREDICTED TO BE RELATIVELY SHORT
WHICH COULD MAKE THE PATTERN LESS STABLE. THE AMPLIFIED MID-LEVEL RIDGE WITH
POSITIVE HEIGHT DEPARTURES SUPPORTS INCREASED ABOVE-NORMAL TEMPERATURE
PROBABILITIES THROUGHOUT THE WESTERN CONUS, NORTHERN TO CENTRAL GREAT PLAINS,
AND UPPER MISSISSIPPI VALLEY. FORECAST CONFIDENCE IN THE 6-10 DAY TEMPERATURE
OUTLOOK IS LOWER ACROSS THE SOUTHERN GREAT PLAINS AND MIDWEST WHERE
TEMPERATURES ARE EXPECTED TO BE MORE VARIABLE DURING THIS 5-DAY PERIOD.
BELOW-NORMAL TEMPERATURES ARE MOST LIKELY ACROSS THE MID-ATLANTIC AND NORTHEAST
DUE IN PART TO PREVALENT EASTERLY SURFACE FLOW. TO THE SOUTH OF A PREDICTED
FRONT, ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR THE GULF COAST AND FLORIDA.
A RESIDUAL FRONT AND AN INCREASED CHANCE FOR SURFACE LOW DEVELOPMENT ANYWHERE
ALONG OR NEAR THIS FRONT FAVORS ABOVE-NORMAL PRECIPITATION ACROSS MUCH OF
TEXAS, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST. BELOW-NORMAL PRECIPITATION IS
MORE LIKELY FOR THE NORTHEAST AS THE MODEL SOLUTIONS DEPICT SURFACE HIGH
PRESSURE PERSISTING. THE AMPLIFIED 500-HPA RIDGE CENTERED OVER THE ROCKIES
SUPPORTS ELEVATED BELOW-NORMAL PRECIPITATION PROBABILITIES FOR MUCH OF THE
NORTH-CENTRAL AND WESTERN CONUS. A TWO-CATEGORY CHANGE (ABOVE TO BELOW) FROM
YESTERDAY'S 6-10 PRECIPITATION OUTLOOK WAS WARRANTED FOR THE PACIFIC NORTHWEST
SINCE MODEL SOLUTIONS HAVE TRENDED TOWARDS A MORE AMPLIFIED RIDGE CLOSER TO THE
WEST COAST AND LITTLE IF ANY ONSHORE FLOW. MODEL GUIDANCE GENERALLY FAVORS A
LACK OF LATE SEASON MONSOON RAINFALL FOR THE DESERT SOUTHWEST.
THE GEFS AND ECENS AGREE THAT A 500-HPA TROUGH PERSISTS OVER MAINLAND ALASKA
WHICH FAVORS NEAR TO ABOVE-NORMAL PRECIPITATION FOR THE STATE. PROBABILITIES
FOR ABOVE-NORMAL PRECIPITATION WERE INCREASED TO ABOVE 50 PERCENT FOR
SOUTHEASTERN ALASKA SINCE THE GEFS AND ECENS HAVE TRENDED STRONGER TODAY WITH
ONSHORE FLOW. 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, NEAR OR ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR
HAWAII. AS OF AUGUST 28, 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 3. THEREFORE, ELEVATED BELOW-NORMAL
PRECIPITATION PROBABILITIES ARE FORECAST FOR HAWAII.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 35% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 45% 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: AVERAGE, 3 OUT OF 5, DUE TO
REASONABLY GOOD AGREEMENT IN THE TEMPERATURE AND PRECIPITATION TOOLS OFFSET BY
UNCERTAINTY ON THE EXACT POSITION OF A RIDGE AXIS OVER THE WESTERN CONUS AND
WHETHER A TROUGH REAMPLIFIES ACROSS THE EASTERN CONUS BY DAY 10.
8-14 DAY OUTLOOK FOR SEP 05 - 11 2024
THE GEFS AND ECENS ARE IN GOOD AGREEMENT AND DEPICT AN AMPLIFIED 500-HPA RIDGE
OVER THE WESTERN CONUS AND DOWNSTREAM TROUGH OF VARYING AMPLITUDE CENTERED OVER
THE OHIO AND TENNESSEE VALLEYS. A NOTABLE CHANGE FROM YESTERDAY IN THE MANUAL
500-HPA HEIGHT BLEND IS A WESTWARD SHIFT OF THE MID-LEVEL RIDGE AXIS CLOSER TO
THE ROCKIES WITH THE LARGEST HEIGHT DEPARTURES OVER THE NORTHERN INTERMOUNTAIN
WEST. DUE TO THE AMPLIFIED 500-HPA RIDGE, ABOVE-NORMAL TEMPERATURES ARE FAVORED
THROUGHOUT THE WESTERN CONUS WITH THE LARGEST PROBABILITIES (ABOVE 80 PERCENT)
FORECAST ACROSS THE GREAT BASIN. ALTHOUGH ABOVE-NORMAL TEMPERATURES ARE ALSO
FAVORED FOR PARTS OF THE GREAT PLAINS, FORECAST CONFIDENCE IS LOWER TODAY DUE
TO THE WESTWARD SHIFT IN THE RIDGE AXIS. EASTERLY SURFACE FLOW, AT LEAST EARLY
IN WEEK-2, AND THE POTENTIAL FOR A TROUGH TO REAMPLIFY TILTS THE 8-14 DAY
TEMPERATURE OUTLOOK TOWARDS BELOW ACROSS SOUTHERN NEW ENGLAND, THE
MID-ATLANTIC, AND SOUTHERN APPALACHIANS. CLOSER TO THE GULF COAST, ABOVE-NORMAL
TEMPERATURES REMAIN MORE LIKELY.
THE WEEK-2 PRECIPITATION OUTLOOK IS BASED ON THE GEFS AND ECMWF REFORECAST
TOOLS, UNCALIBRATED MODEL OUTPUT, AND THE ANALOG TOOL DERIVED FROM THE MANUAL
500-HPA HEIGHT BLEND. ALONG AND DOWNSTREAM OF THE MID-LEVEL RIDGE ALOFT, A
LARGE AREA WITH FAVORED DRYNESS IS FORECAST FOR THE INTERIOR WEST, NORTHERN
ROCKIES, MUCH OF THE GREAT PLAINS, MIDDLE TO UPPER MISSISSIPPI VALLEY, AND
GREAT LAKES. THE TROUGH OVER THE OHIO AND TENNESSEE VALLEYS SUPPORTS ELEVATED
ABOVE-NORMAL PRECIPITATION PROBABILITIES ACROSS THE GULF COAST, SOUTHEAST, AND
MID-ATLANTIC. IN ADDITION AT THE BEGINNING OF WEEK-2, A WAVE OF LOW PRESSURE
MAY DEVELOP ALONG A STALLED FRONT EITHER ACROSS OR OFFSHORE OF THE SOUTHEAST
AND MID-ATLANTIC. NEAR NORMAL PRECIPITATION IS FAVORED FOR THE NORTHEAST, BUT
PRECIPITATION TOOLS HAVE TRENDED SLIGHTLY WETTER TODAY DUE TO THE AMPLIFYING
TROUGH UPSTREAM OVER THE OHIO VALLEY.
AN AMPLIFIED 500-HPA TROUGH AND ENHANCED ONSHORE FLOW FAVOR ABOVE-NORMAL
PRECIPITATION ACROSS EASTERN MAINLAND ALASKA AND SOUTHEASTERN ALASKA. MODEL
GUIDANCE REMAINS CONSISTENT AND IN GOOD AGREEMENT WITH INCREASED BELOW
(ABOVE)-NORMAL TEMPERATURE PROBABILITIES FOR COASTAL WESTERN ALASKA AND THE
ALEUTIANS (EASTERN MAINLAND ALASKA AND SOUTHEASTERN ALASKA).
BASED ON THE GEFS AND ECENS, NEAR NORMAL TEMPERATURES AND BELOW-NORMAL
PRECIPITATION ARE FAVORED FOR HAWAII.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 35% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 45% 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: AVERAGE, 3 OUT OF 5, DUE TO GOOD
AGREEMENT AMONG THE TEMPERATURE AND PRECIPITATION TOOLS OFFSET BY A LONGWAVE
PATTERN WITH SHORT WAVELENGTHS.
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 - 20050824 - 20020830 - 19980819 - 19830901
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:
20050906 - 20050826 - 20030817 - 19980807 - 20020902
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 03 - 07 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A N
SRN CALIF A B IDAHO A N NEVADA A B
W MONTANA A B E MONTANA A B WYOMING A N
UTAH A N ARIZONA A B COLORADO A N
NEW MEXICO A N N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS N B OKLAHOMA B N
N TEXAS B A S TEXAS B A W TEXAS B A
MINNESOTA A B IOWA N B MISSOURI B B
ARKANSAS N A LOUISIANA A A WISCONSIN N B
ILLINOIS B B MISSISSIPPI N A MICHIGAN N B
INDIANA B B OHIO B B KENTUCKY B A
TENNESSEE B A ALABAMA N 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 N
MARYLAND B B DELAWARE B B VIRGINIA B A
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 A
AK S INT A A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 05 - 11 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N 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 N B OKLAHOMA N B
N TEXAS N N S TEXAS A A W TEXAS A N
MINNESOTA A B IOWA N B MISSOURI N B
ARKANSAS N N LOUISIANA A A WISCONSIN A B
ILLINOIS N B MISSISSIPPI N N MICHIGAN A B
INDIANA N N OHIO N N KENTUCKY N N
TENNESSEE N N ALABAMA N N NEW YORK N N
VERMONT N N NEW HAMP N N MAINE A N
MASS B N CONN B N RHODE IS B N
PENN N N NEW JERSEY B N W VIRGINIA N N
MARYLAND B N DELAWARE B A VIRGINIA B A
N CAROLINA N A S CAROLINA N A GEORGIA N 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 A
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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