967
FXUS06 KWBC 121910
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT TUE SEPTEMBER 12 2023
6-10 DAY OUTLOOK FOR SEP 18 - 22 2023
TODAY’S MODEL SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT REGARDING AN AMPLIFIED
500-HPA GEOPOTENTIAL HEIGHT PATTERN ACROSS NORTH AMERICA DURING DAYS 6 THROUGH
10, WITH THE GFS AND CANADIAN ENSEMBLES BEING SLIGHTLY MORE PROGRESSIVE ON ITS
LONGWAVE FEATURES THAN THE ECMWF ENSEMBLE. THE MANUAL 500-HPA HEIGHT BLEND
PREDICTS MID-LEVEL TROUGHING AND NEGATIVE HEIGHT DEPARTURES OVER MOST OF ALASKA
AND WESTERN CANADA, WITH THE EXCEPTION OF POSITIVE HEIGHT DEPARTURES ACROSS THE
ALEUTIANS. MID-LEVEL TROUGHS AND NEAR NORMAL 500-HPA HEIGHTS ARE DEPICTED NEAR
THE WEST AND EAST COASTS OF THE LOWER 48 STATES, WITH WEAK RIDGING OVER THE
CENTRAL CONUS. COMPARED TO YESTERDAY’S MANUAL BLEND, THIS REPRESENTS A RAPID
FALL IN MID-LEVEL HEIGHTS ACROSS WESTERN AND CENTRAL CANADA AND ADJACENT
PORTIONS OF THE NORTHWESTERN AND NORTH-CENTRAL CONUS, WHERE A SIGNIFICANT RIDGE
WAS ANTICIPATED. THE CHANGE IN THE 0Z ECMWF ENSEMBLE SOLUTION FROM YESTERDAY
ACROSS THIS REGION IS NOT QUITE AS ABRUPT AS THE OTHER ENSEMBLE MEANS, AND WAS
THEREFORE SUBJECTIVELY GIVEN MORE WEIGHT IN TODAY’S MANUAL HEIGHT BLEND, AND
THE SURFACE TEMPERATURE AND PRECIPITATION PATTERNS.
THE LATEST TRACK PROJECTIONS (AS OF 11AM AST) FROM THE NATIONAL HURRICANE
CENTER HAVE HURRICANE LEE’S EYE LOCATED ANYWHERE BETWEEN CAPE COD AND EASTERN
NOVA SCOTIA JUST PRIOR TO THE START OF THE 6-10 DAY FORECAST PERIOD. EVEN IF
THE HURRICANE’S CORE PASSES OVER THE GULF OF MAINE OR NOVA SCOTIA, HEAVY
RAINFALL AND GUSTY WINDS ARE STILL A GOOD BET ACROSS MUCH OF NEW ENGLAND. WITH
AN ANTICIPATED RAPID NORTHWARD ACCELERATION OF LEE DURING THE DAYS 4-5 TIME
FRAME, IT IS POSSIBLE THAT THE HURRICANE MAY PASS THROUGH THIS REGION EVEN
BEFORE THE START OF THE 6-10 DAY PERIOD. HOWEVER, GIVEN UNCERTAINTIES INHERENT
IN FORECASTING TROPICAL CYCLONES, IT WAS DECIDED TO KEEP ELEVATED CHANCES OF
ABOVE NORMAL PRECIPITATION IN NEW ENGLAND FOR THE FIRST DAY OF THE 6-10 DAY
PERIOD. MARINERS AND RESIDENTS ARE ADVISED TO MONITOR THE LATEST DEVELOPMENTS
ON HURRICANE LEE, AND TAKE WHATEVER STEPS ARE NECESSARY TO PROTECT LIFE AND
PROPERTY.
TODAY’S 00Z REFORECAST-CALIBRATED GEFS, ECMWF, AND CANADIAN ENSEMBLES SHOW
SIGNIFICANT DIFFERENCES IN THE EXPECTED SURFACE TEMPERATURE PATTERN ACROSS THE
LOWER 48 STATES. AS WAS THE CASE YESTERDAY, TODAY’S GEFS ANTICIPATES A
PREDOMINANTLY WARM SOLUTION (RELATIVE TO NORMAL) ACROSS THE CONUS, WHILE
CANADIAN REFORECAST-CALIBRATED TEMPERATURES DEPICT A PREDOMINANTLY COOL
SOLUTION ACROSS THE CONUS. THE ECMWF REFORECAST-CALIBRATED TEMPERATURES SPLIT
THE DIFFERENCE, WITH A MIX OF NEAR TO ABOVE NORMAL TEMPERATURES FAVORED. THE
6-10 DAY ERF TEMPERATURE CONSOLIDATION, WHICH IS A SKILL-WEIGHTED AVERAGE OF
GEFS AND ECMWF REFORECAST TEMPERATURES, FAVORS ABOVE NORMAL TEMPERATURE CHANCES
OVER MOST OF THE CONUS, AND A RELATIVELY SMALL AREA OF BELOW NORMAL TEMPERATURE
CHANCES FAVORED OVER FAR SOUTHERN CALIFORNIA. THE OFFICIAL TEMPERATURE OUTLOOK
OVER THE CONUS IS LARGELY BASED ON THE TEMPERATURE CONSOLIDATION FORECAST
TODAY. BELOW NORMAL TEMPERATURE CHANCES ARE SLIGHTLY INCREASED OVER WASHINGTON
STATE, CONSISTENT WITH THE STATISTICAL TEMPERATURE ANALOG PROBABILITIES BASED
ON THE MANUAL HEIGHT BLEND, AND THE AUTO-TEMPERATURE FORECAST. BASED ON THE
CONSOLIDATED TOOL AND TEMPERATURES FROM THE AUTOBLEND, A SWATH OF BELOW NORMAL
TEMPERATURES IS FAVORED OVER SOUTHERN ALASKA, AND ABOVE NORMAL TEMPERATURES IS
FAVORED OVER NORTHEASTERN ALASKA.
THE MID-LEVEL TROUGH PREDICTED TO BE NEAR THE WEST COAST IN THE 6-10 DAY PERIOD
SLIGHTLY ENHANCES THE ODDS FOR ABOVE NORMAL PRECIPITATION OVER MUCH OF
CALIFORNIA, NEVADA, THE NORTHERN AND CENTRAL ROCKIES, GREAT PLAINS, AND THE
UPPER AND MIDDLE MISSISSIPPI VALLEY, CONSISTENT WITH THE PRECIPITATION
CONSOLIDATION FORECAST. BELOW NORMAL PRECIPITATION CHANCES ARE SLIGHTLY
ELEVATED OVER SOUTHERN AND EASTERN TEXAS, THE LOWER MISSISSIPPI VALLEY,
PORTIONS OF THE GREAT LAKES REGION, OHIO AND TENNESSEE VALLEYS, AND MUCH OF THE
APPALACHIANS. ABOVE NORMAL PRECIPITATION CHANCES ARE SLIGHTLY ENHANCED OVER THE
FLORIDA PENINSULA NEAR A MID-LEVEL TROUGH. PROBABILITIES FAVORING ABOVE NORMAL
PRECIPITATION EXCEED 50% OVER PORTIONS OF NEW ENGLAND, BASED ON THE LATEST
PREDICTIONS OF HURRICANE LEE, WITH THE CAVEAT THAT LEE MAY ACCELERATE THROUGH
THIS REGION JUST PRIOR TO THE START OF THE 6-10 DAY FORECAST PERIOD. BELOW
NORMAL PRECIPITATION IS MODESTLY FAVORED OVER SECTIONS OF WASHINGTON AND
OREGON, FAR ENOUGH REMOVED FROM THE ONSHORE FLOW TO THE SOUTH RELATED TO A
MID-LEVEL TROUGH. IN ALASKA, WIDESPREAD ONSHORE FLOW ASSOCIATED WITH BROAD
CYCLONIC CURVATURE, MID-LEVEL TROUGHING, AND SLIGHTLY BELOW NORMAL 500-HPA
HEIGHTS FAVORS ABOVE NORMAL PRECIPITATION ACROSS MOST OF THE STATE.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 30% OF TODAY'S 0Z 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: NEAR AVERAGE, 3 OUT OF 5, DUE TO
FAIRLY GOOD AGREEMENT AMONG THE 500-HPA HEIGHT FORECASTS, BUT SIGNIFICANT
DISAGREEMENTS AMONG THE TEMPERATURE AND PRECIPITATION TOOLS, AND CONTINUED
UNCERTAINTY REGARDING THE FUTURE TRACK AND TIMING OF HURRICANE LEE.
8-14 DAY OUTLOOK FOR SEP 20 - 26 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 ANOMALOUS RIDGING OVER THE ALEUTIANS, AND TROUGHING ACROSS
MOST OF DOWNSTREAM ALASKA. OVER THE LOWER 48 STATES, THERE ARE SLIGHT
VARIATIONS ON THE EXACT PLACEMENT OF THE TROUGH-RIDGE-TROUGH WAVETRAIN. BY THE
START OF WEEK-2, LEE IS EXPECTED TO HAVE ALREADY TRANSITIONED INTO AN
EXTRATROPICAL CYCLONE AND DEPARTED THE NORTHEAST CONUS REGION.
THE TEMPERATURE PATTERN FORECAST FOR THE WEEK 2 PERIOD IS GENERALLY SIMILAR TO
THE 6-10 DAY TEMPERATURE OUTLOOK. THERE ARE ENHANCED ODDS OF ABOVE NORMAL
TEMPERATURES OVER PRACTICALLY ALL AREAS EAST OF THE CONTINENTAL DIVIDE,
CONSISTENT WITH GFS AND ECMWF ENSEMBLE MEAN REFORECAST-CALIBRATED TEMPERATURES.
WEST OF THE CONTINENTAL DIVIDE, NEAR TO BELOW NORMAL TEMPERATURE CHANCES ARE
FAVORED, CLOSER TO THE WEST COAST TROUGH AND ASSOCIATED CLOUDINESS AND
PRECIPITATION. IN ALASKA, MID-LEVEL TROUGHING FAVORS BELOW NORMAL TEMPERATURE
CHANCES OVER SOUTHERN ALASKA. THERE ARE SLIGHTLY TILTED ODDS FOR
WARMER-THAN-NORMAL MEAN TEMPERATURES OVER PARTS OF NORTHEASTERN ALASKA.
THE MID-LEVEL TROUGH PREDICTED NEAR THE WEST COAST FAVORS SLIGHTLY INCREASED
ODDS FOR ABOVE NORMAL PRECIPITATION ACROSS MUCH OF THE WESTERN AND CENTRAL
CONUS. CHANCES FOR ABOVE NORMAL PRECIPITATION EXCEED 40% OVER PARTS OF THE
NORTH-CENTRAL CONUS, WHERE INFLOWING GULF MOISTURE IS MOST LIKELY TO INTERACT
WITH BAROCLINIC ZONES. NEAR THE COAST OF THE CAROLINAS, ABOVE NORMAL
PRECIPITATION IS ALSO FAVORED DUE TO THE PROXIMITY OF A MID-LEVEL TROUGH. A
RELATIVELY NARROW STRIPE OF FAVORED BELOW NORMAL PRECIPITATION CHANCES IS
DEPICTED FROM THE EASTERN GREAT LAKES REGION AND PARTS OF THE NORTHEAST
SOUTHWESTWARD ACROSS THE OHIO, TENNESSEE, AND LOWER MISSISSIPPI VALLEYS, AND
CONTINUING ACROSS SOUTHEASTERN TEXAS. THIS IS ASSOCIATED WITH THE REAR-SIDE OF
THE MID-LEVEL TROUGH NEAR THE EAST COAST. IN ALASKA, WIDESPREAD ONSHORE FLOW
ASSOCIATED WITH BROAD CYCLONIC CURVATURE, MID-LEVEL TROUGHING, AND SLIGHTLY
BELOW NORMAL 500-HPA HEIGHTS FAVORS ABOVE NORMAL PRECIPITATION ACROSS MOST OF
THE STATE.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 33% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 34% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 11, AND 33% 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
REASONABLY GOOD AGREEMENT AMONG MODEL ENSEMBLES ON THE PERSISTENT SYNOPTIC
PATTERN, OFFSET BY SOME DIFFERENCES AMONG THE TEMPERATURE AND PRECIPITATION
TOOLS.
FORECASTER: ANTHONY A
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:
20010924 - 19620925 - 20090912 - 20060903 - 19870921
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:
20010923 - 20090823 - 20090914 - 20060905 - 19870921
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 18 - 22 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON N N OREGON N N NRN CALIF N N
SRN CALIF B N IDAHO A N NEVADA N N
W MONTANA A N E MONTANA A N WYOMING A N
UTAH A N ARIZONA N N COLORADO A N
NEW MEXICO A N N DAKOTA A N S DAKOTA A N
NEBRASKA A N KANSAS A N OKLAHOMA A N
N TEXAS A N S TEXAS A N W TEXAS A N
MINNESOTA A N IOWA A N MISSOURI A N
ARKANSAS A N LOUISIANA A N WISCONSIN A N
ILLINOIS A N MISSISSIPPI A N MICHIGAN A N
INDIANA A N OHIO N N KENTUCKY N N
TENNESSEE N N ALABAMA A N NEW YORK A N
VERMONT A N NEW HAMP A A MAINE A A
MASS A A CONN A N RHODE IS A N
PENN N N NEW JERSEY A N W VIRGINIA N N
MARYLAND A N DELAWARE A N VIRGINIA N N
N CAROLINA N N S CAROLINA N N GEORGIA N N
FL PNHDL A N FL PENIN A N AK N SLOPE N A
AK ALEUTIAN N A AK WESTERN N A AK INT BSN N A
AK S INT B A AK SO COAST B A AK PNHDL B A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 20 - 26 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B A OREGON N A NRN CALIF B A
SRN CALIF B N IDAHO N A NEVADA B A
W MONTANA N A E MONTANA A A WYOMING A A
UTAH N N ARIZONA B N COLORADO A A
NEW MEXICO A N N DAKOTA A A S DAKOTA A A
NEBRASKA A A KANSAS A A OKLAHOMA A A
N TEXAS A N S TEXAS A N W TEXAS A N
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A N LOUISIANA A N WISCONSIN A A
ILLINOIS A N MISSISSIPPI A N MICHIGAN A N
INDIANA A N OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A N NEW YORK A N
VERMONT A N NEW HAMP A N MAINE A N
MASS A N CONN A N RHODE IS A N
PENN A N NEW JERSEY A N W VIRGINIA A N
MARYLAND A N DELAWARE A N VIRGINIA A N
N CAROLINA A A S CAROLINA A A GEORGIA A N
FL PNHDL A N FL PENIN A N AK N SLOPE N A
AK ALEUTIAN N N AK WESTERN N A AK INT BSN N A
AK S INT B A AK SO COAST B A AK PNHDL B 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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