340
FXUS06 KWBC 011902
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT MON MAY 01 2023
6-10 DAY OUTLOOK FOR MAY 07 - 11 2023
AN AMPLIFIED 500-HPA LONGWAVE PATTERN IS FORECAST ACROSS THE NORTHERN WESTERN
HEMISPHERE DURING THE 6-10 DAY PERIOD, WITH DEEP TROUGHING OVER THE NORTHERN
ATLANTIC AND CANADIAN MARITIMES, RIDGING ACROSS MUCH OF NORTHERN NORTH AMERICA,
TROUGHING ALONG THE WEST COAST AND EAST PACIFIC, AND RIDGING IN THE NORTH
PACIFIC SOUTH OF THE ALEUTIAN ISLANDS. AS THE MAJOR LONGWAVE FEATURES ARE
LIKELY TO BE DISPLACED SLIGHTLY NORTH, A SHORTWAVE TROUGH MAY DEVELOP AND
PROGRESS ACROSS PARTS OF THE SOUTHERN CONTIGUOUS UNITED STATES (CONUS) DURING
THE PERIOD, BRINGING ELEVATED CHANCES FOR UNSETTLED WEATHER TO THE SOUTHERN
PLAINS AND SOUTHEAST.
WITH MEAN, LONGWAVE RIDGING DEVELOPING ACROSS THE NORTHEASTERN TWO-THIRDS OF
THE CONUS, ABOVE-NORMAL TEMPERATURES ARE FAVORED AS THE PATTERN TRANSITIONS TO
BE MORE SUMMER-LIKE. THE STRONGEST CHANCES FOR ABOVE-NORMAL TEMPERATURES ARE
FOCUSED ACROSS THE GREAT PLAINS AND NORTHEAST WITH LOWER CHANCES ACROSS THE
SOUTHEAST AND OHIO VALLEY WHERE SOME BELOW-NORMAL TEMPERATURES MAY LINGER AT
THE BEGINNING OF THE PERIOD AND SHORTWAVE TROUGHING MAY BRING ENHANCED CLOUD
COVER THAT MAY INHIBIT WARMER TEMPERATURES LATER IN THE PERIOD. ACROSS THE
WESTERN CONUS, A TROUGH IS FORECAST TO LINGER NEAR THE COAST FOR MUCH OF THE
PERIOD, BRINGING CONTINUED CHANCES FOR BELOW-NORMAL TEMPERATURES DURING THE
FORECAST PERIOD. IN ALASKA, THE REFORECAST GUIDANCE INDICATES INCREASED CHANCES
FOR NEAR-NORMAL TEMPERATURES FOR SOUTHERN PORTIONS OF THE STATE COMPARED TO THE
RAW-UNCALIBRATED GUIDANCE WHICH BRINGS STRONG CHANCES FOR BELOW-NORMAL
TEMPERATURES TO THIS SAME REGION. IN LIGHT OF THE STRONGER UNCALIBRATED
GUIDANCE, SLIGHTLY INCREASED CHANCES FOR BELOW-NORMAL TEMPERATURES REMAIN
FORECAST FOR SOUTHERN ALASKA. ACROSS THE NORTH SLOPE, THERE IS GOOD AGREEMENT
FOR ABOVE-NORMAL TEMPERATURES.
WITH LONGWAVE TROUGHING PERSISTING ALONG THE WEST COAST, ABOVE-NORMAL
PRECIPITATION IS FAVORED FROM CENTRAL CALIFORNIA THROUGH MUCH OF THE PACIFIC
NORTHWEST AND NORTHERN ROCKIES. ABOVE-NORMAL PRECIPITATION IS ALSO SLIGHTLY
FAVORED FOR MUCH OF THE GREAT PLAINS AND SOUTHEAST WHERE SOUTHERLY FLOW AND A
SHORTWAVE TROUGH MAY BRING ENHANCED PRECIPITATION. IN THE NORTHEAST,
BELOW-NORMAL PRECIPITATION IS FAVORED WITH DRIER AIR BENEATH A 500-HPA RIDGE
AND SLIGHT NORTHERLY FLOW ALOFT. MEANWHILE, IN ALASKA, BELOW-NORMAL
PRECIPITATION IS FAVORED ACROSS MUCH OF NORTHERN ALASKA AND SLIGHTLY INCREASED
CHANCES FOR ABOVE-NORMAL PRECIPITATION ARE FAVORED ACROSS SOUTHERN PARTS OF THE
STATE.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 30% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 8, 40% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 20%
OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE NORMAL, 4 OUT OF 5, DUE TO
GOOD AGREEMENT AMONG THE DYNAMICAL TOOLS ACROSS THE CONUS OFFSET BY DIFFERENCES
ALONG THE SOUTH COAST OF ALASKA.
8-14 DAY OUTLOOK FOR MAY 09 - 15 2023
THE 500-HPA HEIGHT PATTERN IS FORECAST TO BE LESS AMPLIFIED RELATIVE TO THE
6-10 DAY PERIOD BUT WITH A VERY SIMILAR LONGWAVE PATTERN. A WEAK AREA OF
NEGATIVE 500-HPA HEIGHT ANOMALIES PERSISTS IN THE NORTHERN ATLANTIC NEAR THE
CANADIAN MARITIME PROVINCES. POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST
ACROSS MUCH OF NORTHERN NORTH AMERICA STRETCHING FROM THE NORTHERN TIER OF THE
CONUS INTO NORTHEAST ALASKA. THE NEGATIVE 500-HPA HEIGHT ANOMALIES ALONG THE
WEST COAST IN THE 6-10 DAY PERIOD ARE FORECAST TO RETROGRADE SLIGHTLY INTO THE
GULF OF ALASKA AND SOUTHWEST ALASKA.
ACROSS MUCH OF THE UNITED STATES ABOVE-NORMAL TEMPERATURES ARE FAVORED DURING
THE WEEK-2 PERIOD. ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS THE EASTERN
TWO-THIRDS OF THE CONUS DUE TO SLIGHTLY POSITIVE 500-HPA HEIGHT ANOMALIES
ACROSS THE REGION. ACROSS THE WESTERN THIRD OF THE CONUS, TROUGHING REMAINS
NEAR ENOUGH TO THE COAST THAT NEAR TO SLIGHTLY BELOW-NORMAL TEMPERATURES ARE
FAVORED. IN ALASKA, ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS THE NORTHERN
PORTIONS OF THE STATE, WHILE NEAR TO SLIGHTLY BELOW-NORMAL TEMPERATURES ARE
FAVORED IN THE SOUTHERN PORTIONS OF ALASKA WHERE THERE IS CONTINUED
DISAGREEMENT BETWEEN THE REFORECAST TOOLS, WHICH SHOW NEAR-NORMAL TEMPERATURE
CHANCES, AND THE UNCALIBRATED GUIDANCE, WHICH STRONGLY FAVOR BELOW-NORMAL
TEMPERATURES.
THERE ARE LOW CHANCES FOR ABOVE OR BELOW-NORMAL PRECIPITATION ACROSS MUCH OF
THE CONUS DURING THE WEEK-2 PERIOD. THE BEST CHANCES OF ABOVE-NORMAL
PRECIPITATION ARE LIKELY TO BE FOCUSED ACROSS THE SOUTHERN PLAINS AND FLORIDA
WHERE THERE ARE HIGHER CHANCES FOR SHORTWAVE TROUGHS TO DEVELOP AND PROGRESS
ALONG WITH ENHANCED MOISTURE FROM RETURN FLOW OFF THE GULF OF MEXICO. WITH THE
TROUGH ACROSS THE PACIFIC NORTHWEST, FURTHER OFFSHORE RELATIVE TO THE 6-10 DAY
PERIOD, CHANCES FOR ABOVE-NORMAL PRECIPITATION ARE REDUCED. IN THE NORTHEAST,
NEAR-NORMAL PRECIPITATION CHANCES ARE FAVORED BENEATH POSITIVE 500-HPA HEIGHT
ANOMALIES AND SLIGHT NORTHERLY FLOW ALOFT. IN ALASKA, BELOW-NORMAL
PRECIPITATION IS FAVORED ACROSS THE NORTH SLOPE UNDERNEATH POSITIVE 500-HPA
HEIGHT ANOMALIES. SLIGHTLY ABOVE-NORMAL PRECIPITATION IS FAVORED IN SOUTHEAST
AND SOUTH-CENTRAL ALASKA BENEATH NEGATIVE 500-HPA HEIGHT ANOMALIES.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 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 20%
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
FAIR AGREEMENT IN THE MID-LEVEL HEIGHT PATTERN AND TEMPERATURE TOOLS, OFFSET BY
LOW PROBABILITIES FOR PRECIPITATION CHANCES ACROSS THE UNITED STATES.
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 MAY
18.
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:
19540505 - 19710503 - 20060504 - 19880412 - 19510412
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:
19730430 - 19510410 - 19540505 - 20060504 - 19560413
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR MAY 07 - 11 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 N A E MONTANA A A WYOMING N A
UTAH B B ARIZONA B N COLORADO A B
NEW MEXICO A B N DAKOTA A A S DAKOTA A A
NEBRASKA A A KANSAS A A OKLAHOMA A A
N TEXAS A A S TEXAS A A W TEXAS A A
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A A LOUISIANA A A WISCONSIN A A
ILLINOIS A A MISSISSIPPI A A MICHIGAN A N
INDIANA A A OHIO A N KENTUCKY A A
TENNESSEE A A ALABAMA A A 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 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 A
FL PNHDL A A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN N N AK WESTERN N N AK INT BSN N N
AK S INT B N AK SO COAST B N AK PNHDL N N
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR MAY 09 - 15 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON N N OREGON B N NRN CALIF B N
SRN CALIF B N IDAHO N N NEVADA B N
W MONTANA N N E MONTANA A A WYOMING N N
UTAH N N ARIZONA N N COLORADO A N
NEW MEXICO N A N DAKOTA A A S DAKOTA A A
NEBRASKA A A KANSAS A A OKLAHOMA A A
N TEXAS A A S TEXAS N A W TEXAS A A
MINNESOTA A N IOWA A N MISSOURI A N
ARKANSAS A A LOUISIANA A A WISCONSIN A N
ILLINOIS A N MISSISSIPPI A A MICHIGAN A N
INDIANA A N OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A A 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 A
FL PNHDL A A FL PENIN A A AK N SLOPE A B
AK ALEUTIAN N N AK WESTERN N N AK INT BSN N N
AK S INT B 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.
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