079
FXUS06 KWBC 201905
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT WED SEPTEMBER 20 2023
6-10 DAY OUTLOOK FOR SEP 26 - 30 2023
TODAY’S GFS, ECMWF, AND CANADIAN ENSEMBLE MEAN 500-HPA HEIGHT FORECASTS ARE IN
GOOD AGREEMENT OVER THE FORECAST DOMAIN DURING THE 6-10 DAY PERIOD. THE MANUAL
500-HPA HEIGHT BLEND DEPICTS A TROUGH EXTENDING FROM THE BERING SEA AND WESTERN
ALASKA SOUTHEASTWARD OVER THE GULF OF ALASKA INTO THE NORTHWESTERN CONTIGUOUS
U.S. (CONUS). WELL BELOW-AVERAGE HEIGHTS (AT LEAST -100 METERS) ARE INDICATED
IN THE VICINITY OF VANCOUVER ISLAND, BRITISH COLUMBIA. A FAIRLY FLAT,
LOW-AMPLITUDE RIDGE IS FORECAST SOUTH OF THE ALEUTIANS. THE 0Z ECMWF AND 0Z
CANADIAN ENSEMBLE MEANS PREDICT A DIVERGENCE OF THE WESTERLIES IN THE VICINITY
OF THE DAKOTAS AND UPPER MISSISSIPPI VALLEY. THE NORTHERN BRANCH OF THE
WESTERLIES MOVES UP AND OVER AN AMPLIFIED MID- LEVEL RIDGE OVER EASTERN CANADA,
AND THE SOUTHERN BRANCH OF THE WESTERLIES MOVES DOWN AND UNDER A TROUGH ACROSS
THE SOUTHEAST. THE 0Z GEFS DIFFERS IN THAT IT DOES NOT SHOW A CLEAR SEPARATION
OF THE WESTERLIES, BUT RATHER A RIDGE THAT EXTENDS FROM THE RIO GRANDE VALLEY
NORTHEASTWARD ACROSS THE GREAT LAKES INTO SOUTHEASTERN CANADA, AND A DOWNSTREAM
TROUGH NEAR THE ATLANTIC COAST OF THE LOWER 48 STATES. EARLY AUTUMN IS THE TIME
OF YEAR WHEN THE ATMOSPHERIC CIRCULATION TYPICALLY BECOMES MORE ENERGETIC, AND
FASTER-MOVING SHORTWAVE TROUGHS EMBEDDED IN THE MEAN FLOW BECOME MORE
CHALLENGING TO FORECAST.
PROBABILITIES FAVORING BELOW NORMAL TEMPERATURES ARE INDICATED OVER MUCH OF THE
CONUS WEST OF THE CONTINENTAL DIVIDE. THIS IS CONSISTENT WITH THE
CALIBRATED-REFORECAST TEMPERATURE TOOLS FROM THE ECMWF ENSEMBLE MEAN AND THE
GEFS, AND THE PREDICTED MID-LEVEL TROUGH AND BELOW NORMAL 500-HPA HEIGHTS OVER
THIS REGION. FROM THE SOUTHERN INTERMOUNTAIN REGION AND THE ROCKY MOUNTAINS
EASTWARD TO NEAR THE APPALACHIANS, THERE ARE ELEVATED ODDS OF ABOVE NORMAL
TEMPERATURES. THIS AREA OF FAVORED ABOVE NORMAL TEMPERATURES CONTINUES EASTWARD
OVER NORTHERN PORTIONS OF NEW YORK AND NEW ENGLAND, AND ALSO OVER FLORIDA AND
MUCH OF GEORGIA. IN CONTRAST, REFORECAST TEMPERATURES FROM THE CANADIAN
ENSEMBLE MEAN SHOW A MIX OF FAVORED BELOW, NEAR, AND ABOVE NORMAL TEMPERATURES
FROM THE ROCKIES TO THE APPALACHIANS. IN ALASKA, BELOW NORMAL TEMPERATURE
CHANCES ARE ENHANCED OVER SOUTHWESTERN PORTIONS OF THE STATE, IN PROXIMITY TO A
500-HPA TROUGH, CYCLONIC CURVATURE, AND NEGATIVE SEA SURFACE TEMPERATURE
ANOMALIES. THIS IS ALSO SUPPORTED BY BIAS-CORRECTED TEMPERATURES FROM THE THREE
ENSEMBLE MEANS. A RELATIVELY SMALL AREA OF FAVORED ABOVE NORMAL TEMPERATURES IS
INDICATED OVER NORTHEASTERN ALASKA DUE TO NEARBY MID-LEVEL RIDGING AND ABOVE
NORMAL HEIGHTS.
THERE ARE ELEVATED CHANCES OF ABOVE NORMAL PRECIPITATION OVER THE PACIFIC
NORTHWEST, THE NORTHERN INTERMOUNTAIN REGION, THE NORTHERN ROCKIES, THE
NORTHERN GREAT PLAINS, AND OVER APPROXIMATELY THE NORTHWESTERN HALVES OF
CALIFORNIA AND NEVADA, IN PROXIMITY TO A MID-LEVEL TROUGH, BELOW NORMAL 500-HPA
HEIGHTS, AND CYCLONIC CURVATURE. PROBABILITIES FAVORING ABOVE NORMAL
PRECIPITATION EXCEED 60% OVER THE PACIFIC NORTHWEST AND NEARBY PARTS OF
NORTHERN CALIFORNIA. BELOW NORMAL PRECIPITATION CHANCES ARE ENHANCED OVER
COLORADO AND PARTS OF ADJACENT STATES, FAR ENOUGH REMOVED FROM ANY EXPECTED
STORM TRACKS. THE LARGE ANOMALOUS RIDGE OVER CANADA AND ASSOCIATED POSITIVE
500-HPA HEIGHT ANOMALIES FAVOR BELOW NORMAL PRECIPITATION CHANCES ACROSS THE
GREAT LAKES REGION, NORTHEAST, AND NORTHERN MID-ATLANTIC, WITH AN EXTENSION
OVER UPPER AND MIDDLE PORTIONS OF THE MISSISSIPPI VALLEY, WHERE MID-LEVEL
RIDGING IS ALSO FORECAST. THE COMBINED EFFECTS OF TWO FRONTAL SYSTEMS, ONE
ADVANCING INTO THE SOUTHEAST AND ANOTHER OFF THE SOUTHEAST COAST, SLIGHTLY
FAVOR ABOVE NORMAL PRECIPITATION CHANCES FOR MUCH OF THE SOUTHEAST AND ADJACENT
PORTIONS OF THE MID-ATLANTIC REGION. IN ALASKA, ODDS FAVOR ABOVE NORMAL
PRECIPITATION ACROSS THE ALEUTIANS AND WESTERN ALASKA PENINSULA DUE TO AN
APPROACHING MID-LEVEL TROUGH.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 33% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 34% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 8, AND 33% 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
GOOD AGREEMENT IN THE ENSEMBLE MEAN 500-HPA HEIGHT FIELDS AND TEMPERATURE
TOOLS, BUT OFFSET BY NOTABLE DISCREPANCIES AMONG THE PRECIPITATION TOOLS.
8-14 DAY OUTLOOK FOR SEP 28 - OCT 04, 2023
TODAY’S GFS, ECMWF, AND CANADIAN ENSEMBLE MEAN 500-HPA HEIGHT FORECASTS ARE IN
FAIRLY GOOD AGREEMENT OVER THE FORECAST DOMAIN DURING THE 8-14 DAY PERIOD. A
NEW TROUGH DIGGING OVER THE WESTERN BERING SEA IS HELPING TO REFOCUS MID-LEVEL
TROUGHING BACK TO THIS GENERAL REGION, AND AWAY FROM THE EASTERN GULF OF
ALASKA. FAST WESTERLY FLOW IS ANTICIPATED ACROSS THE NORTH-CENTRAL AND
NORTHEASTERN PACIFIC OCEAN. A MID-LEVEL TROUGH IS PREDICTED OVER THE INTERIOR
WESTERN CONUS, AND A MID-LEVEL RIDGE IS DEPICTED DOWNSTREAM FROM THE
SOUTH-CENTRAL CONUS TO THE GREAT LAKES REGION. RESIDUAL TROUGHING IS INDICATED
NEAR THE MIDDLE AND SOUTHERN ATLANTIC COAST, THOUGH THERE ARE DIFFERENCES AMONG
THE ENSEMBLE MEANS AS TO ITS EXACT LOCATION, WITH THE GEFS BEING SLIGHTLY
FASTER AND FARTHER EAST THAN THE OTHER MODEL RUNS. ACROSS THE SOUTHWESTERN
CONUS, THE CLIMATOLOGICAL MONSOON SEASON IS DRAWING TO A CLOSE. A MAJOR
CONTRIBUTOR TO THE MONSOON IS THE SUBTROPICAL RIDGE, WHICH IS NOW SHIFTED WELL
SOUTHWARD OVER MEXICO AND ADJACENT PORTIONS OF THE EASTERN PACIFIC.
BELOW NORMAL TEMPERATURES ARE FAVORED FOR MOST AREAS WEST OF THE CONTINENTAL
DIVIDE AND OVER SOUTHWESTERN ALASKA, GENERALLY CONSISTENT WITH THE WEEK-2
CALIBRATED-REFORECAST TEMPERATURE TOOLS, AND THE PROXIMITY OF MID-LEVEL TROUGHS
AND CYCLONIC CURVATURE. ALONG THE SOUTHEAST COAST, THE REFORECAST TEMPERATURE
TOOLS ALL DIFFER, WITH THE CANADIAN REFORECAST TOOL FAVORING BELOW NORMAL
TEMPERATURES, THE GEFS REFORECAST TOOL FAVORING NEAR NORMAL TEMPERATURES, AND
THE ECMWF REFORECAST TOOL FAVORING ABOVE NORMAL TEMPERATURES. THIS IS LARGELY
DUE TO THE UNCERTAINTY REGARDING POTENTIAL DEVELOPMENT AND FUTURE TRACK OF A
SIGNIFICANT STORM SYSTEM OFF THE SOUTHEAST COAST EARLY IN THE WEEK-2 PERIOD.
THE WEEK-2 MANUAL TEMPERATURE FORECAST IS HEAVILY INFLUENCED BY THE AUTOMATED
AND CONSOLIDATED TEMPERATURE TOOLS, WHICH FAVOR A SLIGHT TILT IN THE ODDS
TOWARDS ABOVE NORMAL TEMPERATURES OVER THE SOUTHEAST. FROM THE SOUTHERN
INTERMOUNTAIN REGION AND ROCKIES EASTWARD TO THE APPALACHIANS AND ATLANTIC
SEABOARD, ABOVE NORMAL TEMPERATURES ARE FAVORED PRIMARILY DUE TO MID-LEVEL
RIDGING, NEAR TO ABOVE NORMAL 500-HPA HEIGHTS, AND/OR ANTICYCLONIC CURVATURE.
THIS IS ALSO CONSISTENT WITH ECMWF AND GEFS REFORECAST TEMPERATURES. FAVORED
ABOVE NORMAL TEMPERATURES ARE INDICATED OVER THE EASTERN MAINLAND OF ALASKA,
AHEAD OF A MID-LEVEL TROUGH PREDICTED OVER THE WESTERN PART OF THE STATE.
THE CALIBRATED-REFORECAST PRECIPITATION TOOLS FROM THE ECMWF, CANADIAN, AND GFS
ENSEMBLES DEPICT A TILT IN THE ODDS FAVORING ABOVE NORMAL PRECIPITATION FOR
MUCH OF THE COUNTRY WEST OF THE ROCKIES. THIS IS ATTRIBUTED TO A MID-LEVEL
TROUGH AND NEAR TO BELOW-NORMAL 500-HPA HEIGHTS PREDICTED ACROSS THIS REGION.
THE CONSOLIDATED AND AUTOMATED PRECIPITATION TOOLS FAVOR ABOVE NORMAL
PRECIPITATION OVER THE NORTHERN AND CENTRAL ROCKIES, MOST OF THE GREAT PLAINS,
AND A LARGE FRACTION OF THE UPPER MISSISSIPPI VALLEY. THE MID-LEVEL RIDGE
PREDICTED FROM THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY NORTHEASTWARD
ACROSS THE GREAT LAKES, NORTHEAST, AND EASTERN CANADA, FAVORS BELOW NORMAL
PRECIPITATION CHANCES OVER MUCH OF THE EASTERN CONUS. THE POTENTIAL DEVELOPMENT
OF ANOTHER LOW PRESSURE SYSTEM OFF THE SOUTHEAST COAST DURING WEEK-2 TILTS THE
ODDS TOWARDS ABOVE NORMAL PRECIPITATION FOR EASTERN PORTIONS OF THE CAROLINAS
AND THE NEIGHBORING TIDEWATER AREA OF SOUTHEASTERN VIRGINIA. ABOVE NORMAL
PRECIPITATION CHANCES ARE ALSO ELEVATED OVER MOST OF ALASKA, ASSOCIATED WITH A
BROAD MID-LEVEL TROUGH AND CYCLONIC CURVATURE.
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: NEAR AVERAGE, 3 OUT OF 5, DUE TO
GENERALLY GOOD AGREEMENT AMONG THE VARIOUS 500-HPA HEIGHT FORECASTS AND SURFACE
TEMPERATURE GUIDANCE, BUT OFFSET BY SIGNIFICANT DISCREPANCIES IN THE
PRECIPITATION TOOLS, AND LARGE UNCERTAINTY REGARDING POTENTIAL STORM
DEVELOPMENT ALONG A STATIONARY FRONT DRAPED ACROSS THE SOUTHEAST COAST.
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:
20090929 - 19870915 - 19830902 - 19960920 - 19870910
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:
20090928 - 19870914 - 19960922 - 19830902 - 19960917
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 26 - 30 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B A OREGON B A NRN CALIF B A
SRN CALIF B N IDAHO B A NEVADA B A
W MONTANA A A E MONTANA A A WYOMING A N
UTAH A N ARIZONA A N COLORADO A B
NEW MEXICO A N N DAKOTA A A 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 B
ARKANSAS A B LOUISIANA A N WISCONSIN A B
ILLINOIS A B MISSISSIPPI A N MICHIGAN A B
INDIANA A B OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A N NEW YORK A B
VERMONT A B NEW HAMP A B MAINE A B
MASS N B CONN N B RHODE IS N B
PENN N B NEW JERSEY N B W VIRGINIA N N
MARYLAND N N DELAWARE N N VIRGINIA N A
N CAROLINA N A S CAROLINA N A GEORGIA N A
FL PNHDL A N FL PENIN A A AK N SLOPE N N
AK ALEUTIAN B A AK WESTERN B N AK INT BSN N N
AK S INT N N AK SO COAST N N AK PNHDL N N
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 28 - OCT 04, 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B A OREGON B A NRN CALIF B A
SRN CALIF B N IDAHO B A NEVADA B A
W MONTANA B A E MONTANA A A WYOMING N A
UTAH B 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 N
N TEXAS A A S TEXAS A N W TEXAS A A
MINNESOTA A A IOWA A A MISSOURI A N
ARKANSAS A B LOUISIANA A N WISCONSIN A B
ILLINOIS A B MISSISSIPPI A B MICHIGAN A B
INDIANA A B OHIO A B KENTUCKY A B
TENNESSEE A B ALABAMA A B NEW YORK A B
VERMONT A B NEW HAMP A B MAINE A B
MASS A B CONN A B RHODE IS A B
PENN A B NEW JERSEY A N W VIRGINIA A B
MARYLAND A N DELAWARE A N VIRGINIA A B
N CAROLINA A A S CAROLINA A N GEORGIA A N
FL PNHDL A N FL PENIN A N AK N SLOPE N A
AK ALEUTIAN B A AK WESTERN N A AK INT BSN N A
AK S INT N A AK SO COAST B A AK PNHDL N N
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