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FXUS06 KWBC 081902
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT FRI SEPTEMBER 08 2023
6-10 DAY OUTLOOK FOR SEP 14 - 18 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. NEAR- TO ABOVE-NORMAL HEIGHTS
ARE GENERALLY PREDICTED ACROSS THE WESTERN AND NORTH-CENTRAL CONUS, WITH
BELOW-NORMAL HEIGHTS FAVORED ACROSS MUCH OF THE EAST.
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
BECOME MORE FOCUSED OVER THE MID-ATLANTIC AND TENNESSEE VALLEY 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 AND
EXTENDING INTO PARTS OF THE CENTRAL AND SOUTHERN PLAINS. 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 IMMEDIATE GULF OF
MEXICO COAST, AND THE FLORIDA PENINSULA, CONSISTENT WITH THE GEFS AND ECMWF
REFORECAST TOOLS. PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE ELEVATED OVER
MUCH OF THE WESTERN CONUS, NORTHERN PLAINS, AND UPPER MISSISSIPPI VALLEY
UNDERNEATH RIDGING AND ASSOCIATED POSITIVE MID-LEVEL HEIGHT ANOMALIES. 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 MAINLAND.
A FRONTAL SYSTEM FAVORS INCREASED CHANCES FOR ABOVE-NORMAL PRECIPITATION OVER
THE NORTHEAST EARLY IN THE PERIOD. INTERACTION WITH HURRICANE LEE REMAINS
POSSIBLE, WHICH COULD LEAD TO A FURTHER ENHANCEMENT OF PRECIPITATION ACROSS NEW
ENGLAND, HOWEVER, UNCERTAINTY REMAINS HIGH. THE GEFS HAS GENERALLY TRENDED A
BIT WEST COMPARED TO YESTERDAY, WITH THE 00Z DETERMINISTIC ECMWF SHIFTING TO
THE EAST, ALTHOUGH SEVERAL INDIVIDUAL ECMWF ENSEMBLE MEMBERS STILL SHOW THE
HURRICANE POTENTIALLY IMPACTING NEW ENGLAND. EVEN IF THE HURRICANE DOES NOT
MAKE A DIRECT HIT, IT IS LOOKING MORE PLAUSIBLE THAT TROPICAL MOISTURE WILL BE
DRAWN INTO THE FRONTAL SYSTEM UPSTREAM, AND SOME OUTER RAIN BANDS FROM THE
HURRICANE COULD STILL REACH EASTERN NEW ENGLAND. THEREFORE, PROBABILITIES OF
ABOVE-NORMAL PRECIPITATION ARE INCREASED ACROSS NEW ENGLAND COMPARED TO
YESTERDAY, WITH THE HIGHEST PROBABILITIES (GREATER THAN 50 PERCENT) HIGHLIGHTED
ACROSS SOUTHEAST MAINE.
BELOW-NORMAL PRECIPITATION PROBABILITIES ARE INCREASED FROM THE APPALACHIANS
WEST TO THE MISSISSIPPI VALLEY WHERE ENHANCED NORTHERLY MID-LEVEL FLOW AND
SINKING AIR ON THE BACKSIDE OF THE TROUGH AND HURRICANE FAVORS RELATIVELY DRY
CONDITIONS. A STATIONARY FRONT FORECAST ACROSS THE HIGH PLAINS FAVORS INCREASED
PROBABILITIES OF ABOVE-NORMAL PRECIPITATION ACROSS THE CENTRAL AND SOUTHERN
ROCKIES AND PLAINS, SUPPORTED BY THE GEFS AND ECMWF REFORECAST TOOLS.
PROBABILITIES FOR BELOW-NORMAL PRECIPITATION ARE ALSO INCREASED ACROSS
NORTHWEST, AND PARTS OF CALIFORNIA, NEVADA, UTAH, AND ARIZONA DUE TO EXPANDING
RIDGING. SOME INCREASED ONSHORE FLOW, COMBINED WITH VERY LOW PRECIPITATION
CLIMATOLOGY, FAVORS A SLIGHT TILT TOWARD ELEVATED PROBABILITIES OF NEAR- TO
ABOVE-NORMAL PRECIPITATION ACROSS CALIFORNIA. 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 UNCERTAINTY REGARDING THE TRACK OF HURRICANE LEE.
8-14 DAY OUTLOOK FOR SEP 16 - 22 2023
ENSEMBLE MEAN SOLUTIONS FOR THE 8-14 DAY PERIOD PREDICT A FAIRLY PERSISTENT
500-HPA GEOPOTENTIAL HEIGHT PATTERN ACROSS NORTH AMERICA. THE WEEK-2 MANUAL
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 AND THE NORTHWEST ATLANTIC WILL PLAY A ROLE INTO WHETHER OR NOT THE
TRACK BENDS MORE WESTWARD TOWARD EASTERN NEW ENGLAND AND ATLANTIC CANADA OR
REMAINS FURTHER OUT TO SEA. TROUGHING AND BELOW-NORMAL 500-HPA HEIGHTS 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 THROUGH THE
GREAT LAKES AND NORTHEAST, ASSOCIATED WITH RIDGING AND INCREASING MID-LEVEL
HEIGHTS. 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 TENNESSEE AND OHIO VALLEYS, APPALACHIANS, AND
INTERIOR MID-ATLANTIC, UNDERNEATH TROUGHING. THE GEFS REFORECAST TOOL DEPICTS
HIGHER PROBABILITIES OF ABOVE NORMAL TEMPERATURES SPREADING INTO PORTIONS OF
THE EAST-CENTRAL CONUS, BUT TILTED TOWARD HIGHER NEAR- TO BELOW-NORMAL
TEMPERATURE PROBABILITIES GIVEN THE RELATIVELY COOLER ECMWF REFORECAST TOOL AND
UNCALIBRATED GUIDANCE. 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 SOUTHERN ALASKA,
SUPPORTED BY MOST DYNAMICAL MODELS AND FORECAST TOOLS.
NEAR- TO SLIGHTLY BELOW-NORMAL PRECIPITATION PROBABILITIES ARE INCREASED FOR
MOST OF THE WESTERN CONUS, UNDER POSITIVE 500-HPA HEIGHT ANOMALIES AND RIDGING
FORECAST OVER THE REGION, ALTHOUGH THERE IS A BIT MORE UNCERTAINTY GIVEN THE
GEFS AND ECMWF REFORECAST TOOLS DEPICT ENHANCED PROBABILITIES OF ABOVE-NORMAL
PRECIPITATION COMPARED TO THE RELATIVELY DRIER UNCALIBRATED GUIDANCE. 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 AND SPREADING EAST
AND SOUTH INTO PORTIONS OF THE SOUTHEAST, TENNESSEE VALLEY, MID-ATLANTIC, AND
NORTHEAST AS HURRICANE LEE EXITS AND SURFACE HIGH PRESSURE EXPANDS ACROSS THE
OHIO VALLEY. INCREASED CHANCES OF ABOVE-NORMAL PRECIPITATION REMAIN FAVORED
ACROSS PORTIONS OF EASTERN NEW ENGLAND DUE TO ANY POTENTIAL LINGERING IMPACTS
FROM LEE, AND ALSO ACROSS THE CENTRAL AND SOUTHERN ROCKIES AND PLAINS DUE TO A
STATIONARY FRONT. 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
CONTINUED UNCERTAINTY RELATED TO HURRICANE LEE, AS WELL AS DISCREPANCY IN THE
TOOLS REGARDING THE PRECIPITATION FORECAST IN THE WESTERN CONUS.
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:
19590830 - 20050918 - 19910827 - 19750830 - 19770916
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:
19590830 - 20040920 - 19750901 - 20020907 - 20010822
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 14 - 18 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 B COLORADO N A
NEW MEXICO N A N DAKOTA A B S DAKOTA A N
NEBRASKA N A KANSAS B A OKLAHOMA B A
N TEXAS B A S TEXAS A A W TEXAS B A
MINNESOTA A B IOWA N B MISSOURI B B
ARKANSAS B B LOUISIANA B N WISCONSIN N B
ILLINOIS B B MISSISSIPPI B B MICHIGAN B B
INDIANA B B OHIO B B KENTUCKY B B
TENNESSEE B B ALABAMA B B NEW YORK B N
VERMONT N A NEW HAMP A A MAINE A A
MASS A A CONN N A RHODE IS N A
PENN B B NEW JERSEY B N W VIRGINIA B B
MARYLAND B N DELAWARE B N VIRGINIA B B
N CAROLINA B B S CAROLINA B B GEORGIA B N
FL PNHDL N N FL PENIN A N AK N SLOPE A N
AK ALEUTIAN B A 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 16 - 22 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N OREGON A N NRN CALIF A N
SRN CALIF B N IDAHO A N 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 N S DAKOTA A N
NEBRASKA A A 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 B LOUISIANA A N WISCONSIN A B
ILLINOIS N B MISSISSIPPI A B MICHIGAN A B
INDIANA N B OHIO B B KENTUCKY B B
TENNESSEE B B ALABAMA N N NEW YORK N N
VERMONT A N NEW HAMP A N MAINE A A
MASS A N CONN N N RHODE IS A N
PENN N B NEW JERSEY N N W VIRGINIA B B
MARYLAND N B DELAWARE N N VIRGINIA N B
N CAROLINA N 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 A N AK INT BSN A A
AK S INT N A AK SO COAST N 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.
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