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FXUS06 KWBC 271902
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 27 2024
6-10 DAY OUTLOOK FOR OCT 03 - 07 2024
AFTER SEVERAL DAYS OF A FAIRLY STABLE 500-HPA HEIGHT PATTERN AND GOOD AGREEMENT
AMONG THE MODEL GUIDANCE, THERE IS MORE DISAGREEMENT AMONG THE TOOLS TODAY.
GENERALLY, MODEL GUIDANCE IS NOW INDICATING A MORE AMPLIFIED MID-LEVEL PATTERN
ACROSS NORTH AMERICA. THE 6-10 DAY MEAN MID-LEVEL HEIGHT PATTERN FROM THE 0Z
GEFS, 0Z ECENS, AND 0Z CANADIAN ENSEMBLE FORECAST POSITIVE MID-LEVEL HEIGHT
ANOMALIES AND FULL LATITUDE MID-LEVEL RIDGING OVER WESTERN NORTH AMERICA, WITH
BELOW-NORMAL MID-LEVEL HEIGHTS AND TROUGHING ACROSS EASTERN CANADA AND THE
NORTHEAST. HOWEVER, YESTERDAY’S 18Z AND TODAY’S 6Z GEFS ENSEMBLE ARE
SIGNIFICANTLY DIFFERENT FROM PRIOR MODEL RUNS AND TODAY’S 0Z GUIDANCE, WITH
POSITIVE 500-HPA HEIGHT ANOMALIES FORECAST ACROSS THE CONTIGUOUS U.S. (CONUS)
AND NEGATIVE ANOMALIES FORECAST ACROSS WESTERN CANADA. THE CHANGES MAY ACTUALLY
BE DRIVEN BY THE EVENTUAL TRACK OF HURRICANE ISSAC, CURRENTLY IN THE NORTH
ATLANTIC. THE GEFS HAS BEEN FORECASTING TWO SCENARIOS FOR THE ISSAC, THE FIRST
TO MOVE NORTH, TO THE EAST OF ICELAND. THAT WOULD SLOW THE PROGRESSION OF
POSITIVE 500-HPA HEIGHT ANOMALIES OVER EASTERN CANADA AND GREENLAND. THE SECOND
WOULD CONTINUE TO PROGRESS ISSAC EAST TOWARDS EUROPE. THIS GREATLY ENHANCES THE
UNCERTAINTY OF THE MID-LEVEL FORECAST. NEAR-NORMAL HEIGHTS REMAIN FORECAST
ACROSS THE SOUTHEASTERN CONUS IN THE 0Z GEFS, ECENS AND CANADIAN ENSEMBLES. IN
ALASKA, A MID-LEVEL TROUGH REMAINS FORECAST BUT IS FURTHER WEST RELATIVE TO
PRIOR FORECASTS, WITH THE TROUGH AXIS ACROSS THE ALEUTIAN ISLANDS, ALLOWING
ABOVE-NORMAL HEIGHTS TO DEVELOP ACROSS PORTIONS OF THE EASTERN MAINLAND. IN
HAWAII, NEAR-NORMAL 500-HPA HEIGHTS ARE FORECAST.
THE CHANGING AND UNCERTAIN MID-LEVEL HEIGHT PATTERN INCREASES UNCERTAINTY IN
THE TEMPERATURE OUTLOOK ACROSS THE EASTERN CONUS. THE 0Z MODEL RUNS FROM THE
GEFS, ECENS, AND CANADIAN ENSEMBLE ALL TREND TOWARDS COOLER CONDITIONS ACROSS
THE EASTERN CONUS RELATIVE TO PRIOR FORECASTS. HOWEVER, THE 6Z GEFS DECREASES
CONFIDENCE IN THE PATTERN, AND A LARGE AREA OF NEAR-NORMAL IS FAVORED ACROSS
THE EAST TODAY. IF THE PATTERN BECOMES MORE CERTAIN TOMORROW, BELOW-NORMAL
TEMPERATURES MAY BE FAVORED. HOWEVER, ACROSS THE WEST, ALL TOOLS CONTINUE TO
FORECAST STRONG CHANCES FOR ABOVE-NORMAL TEMPERATURES AND PROBABILITIES EXCEED
80% ACROSS THE FOUR CORNERS. IN ALASKA, WITH THE TROUGH AXIS FURTHER WEST,
ABOVE-NORMAL TEMPERATURES ARE GENERALLY FAVORED ACROSS MUCH OF THE MAINLAND,
EXCLUDING THE SOUTHERN COASTAL REGIONS. NEAR-NORMAL TEMPERATURES FAVORED FOR
SOUTHERN ALASKA WITH CONTINUED ONSHORE FLOW FORECAST. NEAR TO ABOVE-NORMAL
TEMPERATURES ARE FAVORED FOR HAWAII CONSISTENT WITH THE AUTOBLEND AND
CONSOLIDATION TOOLS.
THE 6-10 DAY PRECIPITATION FORECAST FAVORS ABOVE-NORMAL PRECIPITATION FOR
PORTIONS OF FLORIDA AND THE GULF COAST ASSOCIATED WITH A FRONTAL BOUNDARY
DRAPED ACROSS THE SOUTHEAST. ADDITIONAL MOISTURE FROM THE TROPICS MAY INCREASE
PRECIPITATION ACROSS THIS REGION. MANY ENSEMBLE MEMBERS FROM THE GEFS AND ECENS
CONTINUE TO INDICATE INCREASED POTENTIAL FOR A TROPICAL CYCLONE TO DEVELOP IN
THE WESTERN CARIBBEAN OR GULF OF MEXICO. THE NATIONAL HURRICANE CENTER IS
MONITORING THIS AREA AND HAS A 30% CHANCE OF DEVELOPMENT DURING THE WEEK-1 TIME
PERIOD. ABOVE-NORMAL PRECIPITATION IS ALSO FAVORED ACROSS PORTIONS OF THE
NORTHEAST ASSOCIATED WITH A SURFACE LOW-PRESSURE SYSTEM EXITING THE REGION.
STRONG HIGH PRESSURE REMAINS FORECAST TO BUILD IN BEHIND THE EXITING SYSTEM,
DESPITE THE DIFFERENCES IN THE MID-LEVEL HEIGHT PATTERN, ACROSS THE EASTERN
CONUS. HOWEVER, PRECIPITATION TOOLS TODAY ARE MORE MIXED AND NEAR-NORMAL
PRECIPITATION IS FAVORED ACROSS MUCH OF THE EASTERN CONUS. BENEATH THE FORECAST
MID-LEVEL RIDGE ACROSS THE CENTRAL AND WESTERN CONUS BELOW-NORMAL PRECIPITATION
CHANCES REMAIN STRONGLY FAVORED. IN ALASKA, ABOVE-NORMAL PRECIPITATION IS
FAVORED ACROSS THE SOUTHERN HALF OF THE STATE ASSOCIATED WITH ONSHORE FLOW
FORECAST DOWNSTREAM FROM THE MID-LEVEL TROUGH OVER WESTERN ALASKA. IN HAWAII,
NEAR-NORMAL PRECIPITATION IS FAVORED, CONSISTENT WITH THE AVAILABLE TOOLS OVER
MUCH OF THE STATE; HOWEVER, BELOW-NORMAL PRECIPITATION IS FORECAST FOR THE BIG
ISLAND.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 15% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 15% OF TODAY'S 6Z 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: BELOW-AVERAGE, 2 OUT OF 5.
INCREASED DISAGREEMENT BETWEEN TODAY AND YESTERDAY’S HEIGHT FORECASTS OFFSET BY
SLIGHTLY BETTER CONTINUITY BETWEEN TEMPERATURE AND PRECIPITATION TOOLS ACROSS
THE WESTERN CONUS.
8-14 DAY OUTLOOK FOR OCT 05 - 11 2024
THE WEEK-2 FORECAST IS ALSO MORE CHALLENGING THAN PRIOR FORECASTS WITH MORE
DISAGREEMENT AMONG THE MODEL TOOLS. THERE ARE SIGNIFICANT DIFFERENCES BETWEEN
YESTERDAY’S GEFS, ECENS, AND CANADIAN ENSEMBLE MEANS’ WEEK-2 HEIGHT PATTERN
FORECASTS, AND TODAY’S. FURTHER INCREASING UNCERTAINTY IS THE 6Z GEFS WHICH
SIGNIFICANTLY CHANGED FROM THE 0Z GEFS AS IN THE 6-10 DAY PERIOD. AS SUCH THERE
ARE FAIRLY LARGE CHANGES IN THE FORECAST HEIGHTS AND TEMPERATURES RELATIVE TO
YESTERDAY. TODAY’S WEEK-2 MID-LEVEL HEIGHT FORECAST FOR NORTH AMERICA FEATURES
A MORE AMPLIFIED PATTERN RELATIVE TO YESTERDAY, WITH A TROUGH ACROSS PORTIONS
OF ALASKA, A FULL LATITUDE RIDGE FORECAST ACROSS WESTERN NORTH AMERICA, A
DEEPER AND BROADER TROUGH ACROSS THE EASTERN CONUS, AND A STRONG RIDGE CENTERED
NEAR GREENLAND. IN HAWAII, NEAR-NORMAL HEIGHTS ARE FORECAST.
DURING WEEK-2, ABOVE-NORMAL TEMPERATURES REMAIN FAVORED ACROSS THE WESTERN
CONUS WITH GOOD AGREEMENT AMONG THE TOOLS. HOWEVER, ACROSS THE EAST NEAR- TO
BELOW-NORMAL TEMPERATURES ARE FAVORED. THIS IS A SIGNIFICANT ADJUSTMENT FROM
PRIOR FORECASTS WHEN TOOLS FAVORED WARMER CONDITIONS, WHEREAS TODAY’S ARE
GENERALLY MUCH COOLER. THIS IS CONSISTENT WITH THE DEEPER TROUGH FORECAST IN
500-HPA HEIGHT BLEND. THIS IS ALSO CONSISTENT WITH TELECONNECTIONS OF THE
500-HPA HEIGHT CENTER OFF OF GREENLAND. IN ALASKA, ABOVE-NORMAL TEMPERATURES
REMAIN FORECAST IN THE NORTHERN AND EASTERN MAINLAND WITH NEAR-NORMAL
TEMPERATURES FAVORED ALONG THE SOUTHERN COASTAL REGIONS AND SOUTHEAST ALASKA.
IN HAWAII, ABOVE-NORMAL TEMPERATURES ARE FAVORED CONSISTENT WITH A BLEND OF
TOOLS AND FORECAST CONSOLIDATION.
DURING THE WEEK-2 PERIOD, BELOW-NORMAL PRECIPITATION IS FAVORED ACROSS MUCH OF
THE WESTERN CONUS BENEATH A STRONG MID-LEVEL RIDGE AND SURFACE HIGH PRESSURE.
IN THE EASTERN NORTHEAST AND MID-ATLANTIC, NEAR-NORMAL PRECIPITATION IS FAVORED
WITH MIXED SIGNALS AMONG THE TOOLS. IN THE SOUTHEAST, ABOVE-NORMAL
PRECIPITATION IS FAVORED WITH INCREASED CHANCES FOR CONTINUED TROPICAL MOISTURE
TO WORK INTO THE REGION. MANY ENSEMBLE MEMBERS FROM THE GEFS AND ECENS DEPICT
CHANCES FOR A TROPICAL SYSTEM TO DEVELOP IN THE WESTERN CARIBBEAN OR GULF OF
MEXICO. THERE IS A LOT OF UNCERTAINTY BUT ENHANCED TROPICAL MOISTURE INFLUX IS
FAVORED AND ABOVE-NORMAL PRECIPITATION IS FORECAST FOR MUCH OF THE GULF COAST.
THE TROUGH ACROSS WESTERN ALASKA IS FORECAST TO BRING ABOVE-NORMAL
PRECIPITATION TO MUCH OF SOUTHERN ALASKA. IN HAWAII, NEAR-NORMAL PRECIPITATION
IS FORECAST CONSISTENT WITH THE MAJORITY OF AVAILABLE TOOLS.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 15% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 15% 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: BELOW-AVERAGE, 2 OUT OF 5.
INCREASED DISAGREEMENT BETWEEN TODAY AND YESTERDAY’S HEIGHT FORECASTS OFFSET BY
SLIGHTLY BETTER CONTINUITY BETWEEN TEMPERATURE AND PRECIPITATION TOOLS ACROSS
THE WESTERN CONUS.
FORECASTER: RYAN BOLT
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 17.
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:
19870916 - 20081006 - 20010927 - 19551006 - 20051010
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:
19870916 - 20071010 - 20010926 - 19551010 - 19680914
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 03 - 07 2024
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 B COLORADO A B
NEW MEXICO A B N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS A B OKLAHOMA A B
N TEXAS A B S TEXAS A A W TEXAS A B
MINNESOTA N B IOWA A B MISSOURI A B
ARKANSAS A B LOUISIANA A A WISCONSIN N B
ILLINOIS N B MISSISSIPPI A N MICHIGAN N N
INDIANA N N OHIO N N KENTUCKY N N
TENNESSEE N N ALABAMA A N NEW YORK N N
VERMONT N A NEW HAMP N A MAINE A A
MASS N A CONN N N RHODE IS N N
PENN N N NEW JERSEY N N W VIRGINIA N N
MARYLAND N N DELAWARE N N VIRGINIA N N
N CAROLINA N N S CAROLINA N N GEORGIA A A
FL PNHDL A A FL PENIN A A AK N SLOPE A N
AK ALEUTIAN B A AK WESTERN A A AK INT BSN A N
AK S INT N A AK SO COAST N A AK PNHDL N A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR OCT 05 - 11 2024
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 B COLORADO A B
NEW MEXICO A B N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS A B OKLAHOMA A B
N TEXAS A B S TEXAS A N W TEXAS A B
MINNESOTA A B IOWA A B MISSOURI N B
ARKANSAS N B LOUISIANA A N WISCONSIN N N
ILLINOIS N B MISSISSIPPI N N MICHIGAN N N
INDIANA N N OHIO B N KENTUCKY B N
TENNESSEE N N ALABAMA N N NEW YORK B N
VERMONT B N NEW HAMP N N MAINE N A
MASS N N CONN B N RHODE IS N N
PENN B N NEW JERSEY B N W VIRGINIA B N
MARYLAND B N DELAWARE B N VIRGINIA B N
N CAROLINA B N 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 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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