364
FXUS06 KWBC 291913
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 29 2023
6-10 DAY OUTLOOK FOR OCT 05 - 09 2023
THERE IS INCREASED UNCERTAINTY WITH RESPECT TO THE OVERALL MID-LEVEL HEIGHT
PATTERN ACROSS NORTH AMERICA DURING THE NEXT 6-10 DAYS, PARTICULARLY ACROSS
PARTS OF ALASKA AND EASTERN CONTIGUOUS U.S. (CONUS). THE GEFS FAVORS INCREASED
NEGATIVE 500-HPA HEIGHT ANOMALIES ACROSS MUCH OF THE EASTERN HALF OF THE CONUS
AND WESTERN ALASKA, WHEREAS THE ECMWF ENSEMBLE INDICATES WEAKER AND LESS
EXPANSIVE NEGATIVE MID-LEVEL HEIGHT ANOMALIES ACROSS THE EASTERN CONUS AND
FAVORS POSITIVE HEIGHT ANOMALIES ACROSS WESTERN ALASKA. OTHERWISE, THE MODELS
GENERALLY AGREE IN DEPICTING STRONG MID-LEVEL RIDGING AND ABOVE-NORMAL
MID-LEVEL HEIGHTS ACROSS MOST OF WESTERN NORTH AMERICA. HOWEVER, THE
DIFFERENCES IN THE INTENSITIES OF THESE MID-LEVEL FEATURES, PARTICULARLY IN THE
EASTERN CONUS, IS INDICATIVE OF UNCERTAINTY WITH RESPECT TO THE EVOLUTION OF
THE PATTERN DURING THE 6-10 DAY PERIOD.
ACROSS THE WESTERN THIRD OF THE CONUS, ABOVE-NORMAL TEMPERATURES ARE FAVORED
UNDERNEATH STRONG MID-LEVEL RIDGING OVER MUCH OF WESTERN NORTH AMERICA. DURING
THE 6-10 DAY PERIOD, AN AREA OF SURFACE LOW PRESSURE WITH A TRAILING FRONTAL
BOUNDARY IS FORECAST TO MOVE EASTWARD FROM THE GREAT PLAINS TO THE EAST COAST.
BEHIND THIS SYSTEM, COLDER AIR IS FORECAST TO BE DRAWN SOUTHWARD FROM CANADA
ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS TOWARD THE MIDDLE AND LATTER HALF
OF THE PERIOD. THE TIMING AND INTENSITY OF THIS EVENT INCREASES UNCERTAINTY IN
THE RESULTING TEMPERATURE OUTLOOK. DESPITE THIS UNCERTAINTY, NEAR- TO
BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS MUCH OF THE CENTRAL CONUS.
ABOVE-NORMAL TEMPERATURE PROBABILITIES ARE FAVORED ALONG THE EAST COAST AND IN
THE EASTERN GREAT LAKES DUE TO ABOVE-NORMAL TEMPERATURES FORECAST IN THE FIRST
HALF OF THE PERIOD. IN ALASKA, STRONG MID-LEVEL TROUGHING OVER THE NORTH
PACIFIC EXTENDS NORTHWARD OVER THE MAINLAND. ALONG AND BEHIND THE MEAN TROUGH
AXIS, BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS MOST OF THE MAINLAND AND THE
ALEUTIANS. CONVERSELY, AHEAD OF THE TROUGH AXIS, SOUTHWESTERLY FLOW ALOFT
FAVORS A TILT IN THE ODDS TOWARD ABOVE-NORMAL TEMPERATURES ACROSS THE ALASKA
PANHANDLE.
BELOW-NORMAL PRECIPITATION ODDS ARE ENHANCED ACROSS MUCH OF THE NORTH-CENTRAL
AND NORTHWESTERN CONUS, UNDERNEATH STRONG MID-LEVEL RIDGING OVER WESTERN NORTH
AMERICA. ABOVE-NORMAL PRECIPITATION IS FAVORED ACROSS MUCH OF THE EASTERN AND
SOUTH-CENTRAL CONUS, ASSOCIATED WITH AN AREA OF SURFACE LOW PRESSURE WITH A
TRAILING FRONTAL BOUNDARY PROGRESSING EASTWARD FROM THE GREAT PLAINS TO THE
EAST COAST LATER IN THE PERIOD. THERE IS SOME UNCERTAINTY REGARDING A POTENTIAL
TROPICAL CYCLONE DEVELOPING IN THE TROPICAL EAST PACIFIC AND MOVING INTO
NORTHERN MEXICO TOWARD THE END OF THE PERIOD, WHICH COULD LEAD TO ENHANCED
PRECIPITATION ACROSS PORTIONS OF THE DESERT SOUTHWEST AND SOUTH-CENTRAL CONUS.
IN ALASKA, BELOW-NORMAL (ABOVE-NORMAL) PRECIPITATION IS FAVORED ACROSS THE
WESTERN (CENTRAL AND EASTERN) MAINLAND, BEHIND (AHEAD) OF A MEAN MID-LEVEL
TROUGH.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 50% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, AND 50% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO
UNCERTAINTY IN THE EVOLUTION OF THE MID-LEVEL HEIGHT PATTERN TOWARD THE LATTER
HALF OF THE PERIOD, ESPECIALLY IN THE EASTERN CONUS, AND MODEL UNCERTAINTY IN
THE PREDICTED MID-LEVEL HEIGHT ANOMALIES OVER ALASKA.
8-14 DAY OUTLOOK FOR OCT 07 - 13 2023
THERE IS DECENT OVERALL AGREEMENT BETWEEN DYNAMICAL MODEL GUIDANCE WITH RESPECT
TO THE GENERAL LOCATION OF 500-HPA FEATURES OVER NORTH AMERICA DURING THE 8-14
DAY (WEEK-2) PERIOD. HOWEVER, THERE IS DISAGREEMENT AMONG THE MODELS WITH
RESPECT TO THE STRENGTH OF THESE FEATURES, LEADING TO INCREASED UNCERTAINTY,
PARTICULARLY ACROSS THE EASTERN HALF OF THE CONUS. DESPITE THE UNCERTAINTY IN
THE STRENGTH OF THE MID-LEVEL FEATURES, AN AMPLIFIED PATTERN IS FAVORED OVER
THE FORECAST DOMAIN DURING THE NEXT 8-14 DAYS. STRONG MID-LEVEL TROUGHING IS
FAVORED OVER THE NORTH PACIFIC, EXTENDING NORTHWARD ACROSS WESTERN ALASKA.
DOWNSTREAM, AMPLIFIED MID-LEVEL RIDGING (TROUGHING) IS PREDICTED ACROSS WESTERN
(EASTERN) NORTH AMERICA.
ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ARE FAVORED OVER MUCH OF
THE WESTERN HALF OF THE CONUS DURING WEEK-2, UNDERNEATH STRONG MID-LEVEL
RIDGING OVER WESTERN NORTH AMERICA. CONVERSELY, ENHANCED PROBABILITIES OF
BELOW-NORMAL TEMPERATURES ARE FAVORED OVER MUCH OF THE EASTERN CONUS, ALONG AND
BEHIND AN AMPLIFIED MEAN TROUGH. BELOW-NORMAL TEMPERATURE PROBABILITIES EXTEND
WESTWARD ACROSS THE SOUTHERN PLAINS, BEHIND THE MEAN FRONTAL BOUNDARY.
BELOW-NORMAL TEMPERATURE CHANCES ARE SLIGHTLY INCREASED IN THE RIO GRANDE
VALLEY DUE TO INCREASED CHANCES OF ABOVE-NORMAL PRECIPITATION IN THIS REGION.
ALONG AND AHEAD OF A MEAN FRONTAL BOUNDARY, ABOVE-NORMAL TEMPERATURES ARE
FAVORED IN THE SOUTHERN FLORIDA PENINSULA AND NORTHERN NEW ENGLAND. SIMILAR TO
THE 6-10 DAY PERIOD, MID-LEVEL TROUGHING IS FAVORED ACROSS ALASKA, WITH
NORTHERLY (SOUTHERLY) FLOW ALOFT FAVORING BELOW-NORMAL (ABOVE-NORMAL)
TEMPERATURES ACROSS WESTERN (SOUTHEASTERN) PARTS OF THE STATE.
SURFACE HIGH PRESSURE BEHIND A FORECAST STORM SYSTEM EXITING OFF THE EAST COAST
IS FAVORED TO BRING ELEVATED ODDS OF BELOW-NORMAL PRECIPITATION ACROSS MUCH OF
THE INTERIOR AND NORTHERN CONUS. ALONG AND AHEAD OF A MEAN FRONTAL BOUNDARY,
NEAR- TO ABOVE-NORMAL PRECIPITATION ODDS ARE FAVORED FOR THE NORTHEAST AND
MID-ATLANTIC, FLORIDA PENINSULA, AND PORTIONS OF THE RIO GRANDE VALLEY.
ABOVE-NORMAL PRECIPITATION ODDS ACROSS PORTIONS OF THE DESERT SOUTHWEST AND RIO
GRANDE VALLEY ARE ALSO ASSOCIATED WITH THE POSSIBILITY OF A POTENTIAL TROPICAL
CYCLONE TRANSITIONING INTO THE MID-LATITUDES FROM THE EAST PACIFIC. A FORECAST
EASTWARD PROGRESSION OF THE MID-LEVEL RIDGING ACROSS NORTH AMERICA FAVORS
INCREASED ONSHORE FLOW INTO THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA,
LEADING TO A TILT IN THE ODDS TOWARD ABOVE-NORMAL PRECIPITATION. IN ALASKA,
PREDICTED MID-LEVEL TROUGHING OVER THE WESTERN MAINLAND FAVORS BELOW-NORMAL
PRECIPITATION ACROSS THE WEST COAST OF THE MAINLAND AND PORTIONS OF THE
ALEUTIANS, WITH NEAR- TO ABOVE-NORMAL PRECIPITATION FAVORED ELSEWHERE,
ASSOCIATED WITH STRONG ONSHORE FLOW.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 40% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, AND 60% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO
UNCERTAINTY IN THE EVOLUTION OF THE OVERALL PATTERN AND THE POSSIBILITY OF A
POTENTIAL TROPICAL CYCLONE MOVING NORTHWARD FROM THE NORTH PACIFIC.
FORECASTER: ADAM HARTMAN
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
OCTOBER 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:
19841012 - 20071009 - 19680920 - 20081006 - 20010928
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:
19680921 - 19841012 - 20071009 - 19981012 - 19680916
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 05 - 09 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A B
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 N COLORADO N B
NEW MEXICO B A N DAKOTA N B S DAKOTA N B
NEBRASKA B B KANSAS B B OKLAHOMA B B
N TEXAS B A S TEXAS B A W TEXAS B A
MINNESOTA N N IOWA B N MISSOURI B N
ARKANSAS B N LOUISIANA N A WISCONSIN N N
ILLINOIS B N MISSISSIPPI N A MICHIGAN N A
INDIANA N A OHIO N A KENTUCKY N A
TENNESSEE N A ALABAMA N N NEW YORK A A
VERMONT A A NEW HAMP A A MAINE A A
MASS A A CONN A A RHODE IS A A
PENN A A NEW JERSEY A A W VIRGINIA N A
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA N A GEORGIA N N
FL PNHDL A N FL PENIN A N AK N SLOPE B A
AK ALEUTIAN B N AK WESTERN B N AK INT BSN B A
AK S INT B A AK SO COAST B A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 07 - 13 2023
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 N COLORADO A B
NEW MEXICO A N N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS N B OKLAHOMA N B
N TEXAS B B S TEXAS B N W TEXAS B N
MINNESOTA N B IOWA N B MISSOURI B B
ARKANSAS B B LOUISIANA N B WISCONSIN B 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 N NEW HAMP N A MAINE A A
MASS N A CONN B A RHODE IS B A
PENN B N NEW JERSEY B N W VIRGINIA B B
MARYLAND B N DELAWARE B N VIRGINIA B N
N CAROLINA B B S CAROLINA B B GEORGIA B B
FL PNHDL B B FL PENIN N N AK N SLOPE N A
AK ALEUTIAN B B AK WESTERN B N AK INT BSN N A
AK S INT N A AK SO COAST N 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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