521
FXUS06 KWBC 082031
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST FRI DECEMBER 08 2023
6-10 DAY OUTLOOK FOR DEC 14 - 18 2023
THE GEFS, ECMWF, AND CANADIAN ENSEMBLE MEANS ARE IN GOOD AGREEMENT DEPICTING A
BROAD 500-HPA RIDGE OVER THE NORTHERN THREE-QUARTERS OF THE CONTIGUOUS U.S.
(CONUS). THIS BROAD RIDGE WITH POSITIVE 500-HPA HEIGHT ANOMALIES ALONG WITH
STRONG WEST-TO-EAST SURFACE FLOW ACROSS SOUTHERN CANADA FAVORS ABOVE NORMAL
TEMPERATURES FOR THE WEST, MOST OF THE GREAT PLAINS AND MISSISSIPPI VALLEY,
GREAT LAKES, OHIO AND TENNESSEE VALLEYS, AND SOUTHERN FLORIDA. DOWNSLOPE
SURFACE FLOW AND LACK OF SNOW COVER ENHANCES THE ABOVE NORMAL TEMPERATURE
PROBABILITIES ACROSS THE NORTHERN GREAT PLAINS. PROBABILITIES FAVORING ABOVE
NORMAL TEMPERATURES EXCEED 70% OVER THE GENERAL VICINITY OF THE UPPER
MISSISSIPPI VALLEY. ACROSS PORTIONS OF THE SOUTH-CENTRAL AND SOUTHEASTERN
CONUS, SURFACE TEMPERATURES ARE FAVORED TO TRANSITION FROM SLIGHTLY BELOW OR
NEAR NORMAL EARLIER IN THE PERIOD TO ABOVE NORMAL LATER IN THE PERIOD,
AVERAGING OUT TO NEAR NORMAL.
EXPANSIVE SURFACE HIGH PRESSURE FAVORS BELOW NORMAL PRECIPITATION THROUGHOUT
MUCH OF THE WESTERN AND NORTHERN CONUS. ONE OR MORE SOUTHERN STREAM SHORTWAVES
LEAD TO INCREASED ABOVE NORMAL PRECIPITATION PROBABILITIES ACROSS NEW MEXICO,
THE SOUTHERN HALF OF THE GREAT PLAINS, AND NEAR THE GULF COAST AND SOUTHERN
ATLANTIC COAST (INCLUDING FLORIDA). THE 12Z DETERMINISTIC GFS PREDICTS MULTIPLE
OPPORTUNITIES FOR SOUTHERN STREAM SHORTWAVES TO INDUCE SURFACE CYCLOGENESIS
NEAR THE SOUTHERN ATLANTIC COAST DURING THIS PERIOD. A MID-LEVEL DISTURBANCE
FROM THE EASTERN PACIFIC IS EXPECTED TO MOVE INTO CALIFORNIA, UNDERCUTTING THE
BROAD MID-LEVEL RIDGE PREDICTED OVER MOST OF THE CONUS. THIS TILTS THE ODDS
TOWARDS ABOVE NORMAL PRECIPITATION FOR NORTHERN AND CENTRAL CALIFORNIA.
MODEL SOLUTIONS CONTINUE TO BE IN VERY GOOD AGREEMENT ON AN AMPLIFIED 500-HPA
RIDGE WEST OF THE BERING STRAIT WITH A DOWNSTREAM TROUGH OVER ALASKA. THIS LONG
WAVE PATTERN SUPPORTS BELOW NORMAL TEMPERATURES AND BELOW NORMAL PRECIPITATION
OVER WESTERN PORTIONS OF ALASKA. AHEAD OF THE MID-LEVEL TROUGH ONSHORE FLOW
FAVORS ABOVE NORMAL TEMPERATURES OVER SOUTHEASTERN ALASKA, AND ABOVE NORMAL
PRECIPITATION OVER SOUTHERN AND EASTERN ALASKA.
BASED ON THE CONSOLIDATION TOOL (SKILL-WEIGHTED GEFS AND ECMWF REFORECASTS),
THERE ARE INCREASED CHANCES FAVORING ABOVE NORMAL TEMPERATURES AND NEAR NORMAL
PRECIPITATION ACROSS THE HAWAIIAN ISLANDS.
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 ON THE LONGWAVE PATTERN ALONG WITH THE TEMPERATURE AND
PRECIPITATION TOOLS.
8-14 DAY OUTLOOK FOR DEC 16 - 22 2023
THE GEFS, ECMWF, AND CANADIAN ENSEMBLE MEANS MAINTAIN POSITIVE 500-HPA HEIGHT
ANOMALIES ACROSS MOST OF THE CONUS, WITH NEAR NORMAL HEIGHTS FORECAST NEAR THE
GULF COAST. THIS PERSISTENT PATTERN AND ABSENCE OF ANY NORTHERLY FLOW LEADS TO
CONTINUED HIGH FORECAST CONFIDENCE FOR MILD MID-LATE DECEMBER TEMPERATURES. THE
WEEK-2 TEMPERATURE OUTLOOK DEPICTS INCREASED COVERAGE OF FAVORED ABOVE NORMAL
TEMPERATURES FROM THE 6-10 DAY PERIOD. THE LARGEST PROBABILITIES (MORE THAN 70
PERCENT) OF ABOVE NORMAL TEMPERATURES ARE FORECAST ACROSS THE GENERAL VICINITY
OF THE UPPER MISSISSIPPI VALLEY. NEAR NORMAL TEMPERATURES ARE LIMITED TO
SOUTHERN TEXAS.
THE WEEK-2 PRECIPITATION OUTLOOK DEPICTS NEAR NORMAL PRECIPITATION FOR MOST OF
THE WEST COAST STATES, AS THERE IS MORE UNCERTAINTY REGARDING EXTENT AND
DURATION OF ONSHORE FLOW ESPECIALLY OVER THE NORTHWEST COMPARED TO YESTERDAY.
BELOW NORMAL PRECIPITATION IS SLIGHTLY FAVORED OVER THE INTERIOR WEST,
CONTINUING ACROSS THE NORTHERN PLAINS, PORTIONS OF THE CENTRAL PLAINS, UPPER
MISSISSIPPI VALLEY, AND MOST OF THE GREAT LAKES REGION. THIS IS ASSOCIATED WITH
THE SPRAWLING MID-LEVEL RIDGE AND ABOVE AVERAGE 500-HPA HEIGHTS PREDICTED OVER
MOST OF THE CONUS.
SOUTHERN STREAM DISTURBANCES FAVOR ABOVE NORMAL PRECIPITATION CHANCES OVER
PARTS OF CALIFORNIA, SOUTH-CENTRAL PORTIONS OF THE CONUS, THE GULF COAST, AND
FROM FLORIDA NORTHEASTWARD ACROSS THE ATLANTIC COAST STATES AS FAR NORTH AS NEW
JERSEY AND LONG ISLAND, NY. THIS LARGE AREA OF FAVORED ABOVE NORMAL
PRECIPITATION IS CONSISTENT WITH GEFS AND ECMWF REFORECAST-CALIBRATED
PRECIPITATION GUIDANCE. PRELIMINARY INDICATIONS FAVOR AN ACTIVE STORM TRACK FOR
THE GULF AND EAST COAST STATES DURING WEEK-2, WHICH COULD COMPLICATE TRAVEL
PLANS FOR COMMUTERS DURING THE VERY BUSY PRE-CHRISTMAS PERIOD.
DOWNSTREAM OF THE TROUGH AXIS OVER WESTERN ALASKA, ONSHORE FLOW AND ABOVE
NORMAL PRECIPITATION IS FAVORED FOR SOUTHERN AND EASTERN ALASKA WITH NEAR TO
BELOW NORMAL PRECIPITATION MORE LIKELY FOR THE REMAINDER OF THE STATE.
CONSISTENT WITH THE 500-HPA AND SURFACE PATTERNS ALONG WITH GOOD MODEL
CONSISTENCY, BELOW NORMAL TEMPERATURES ARE FAVORED FOR WESTERN ALASKA, AND
ABOVE NORMAL TEMPERATURES ARE FAVORED FOR LARGE PORTIONS OF CENTRAL AND EASTERN
ALASKA.
THE WEEK-2 TEMPERATURE OUTLOOK FOR HAWAII IS BASED ON THE CONSOLIDATION TOOL
AND FAVORS WARMER THAN NORMAL CONDITIONS FOR MOST AREAS. NEAR NORMAL
PRECIPITATION IS MOST LIKELY FOR ALL THE HAWAIIAN ISLANDS.
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 GOOD
AGREEMENT AMONG THE TEMPERATURE TOOLS OFFSET BY MORE UNCERTAINTY IN THE
PRECIPITATION OUTLOOK DUE TO WEAK OR CONFLICTING SIGNALS AMONG THE 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
DECEMBER 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:
20011220 - 19971129 - 19871204 - 19811205 - 20091217
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:
20031204 - 19971128 - 19811207 - 20011219 - 19681213
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 14 - 18 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A N
SRN CALIF A B IDAHO N B NEVADA A B
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A B ARIZONA A B COLORADO A A
NEW MEXICO A A N DAKOTA A B S DAKOTA A B
NEBRASKA A N KANSAS A A OKLAHOMA A A
N TEXAS N A S TEXAS N A W TEXAS N A
MINNESOTA A B IOWA A B MISSOURI A N
ARKANSAS A N LOUISIANA N A WISCONSIN A B
ILLINOIS A B MISSISSIPPI A N MICHIGAN A B
INDIANA A B OHIO A B KENTUCKY A B
TENNESSEE A N ALABAMA N N NEW YORK A B
VERMONT N B NEW HAMP N N MAINE N B
MASS N N CONN N N RHODE IS N N
PENN A B NEW JERSEY N N W VIRGINIA A N
MARYLAND N N DELAWARE N N VIRGINIA N N
N CAROLINA N N S CAROLINA N N GEORGIA N N
FL PNHDL N A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN B N AK WESTERN B N AK INT BSN N A
AK S INT N A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 16 - 22 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N OREGON A N NRN CALIF A N
SRN CALIF A B 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 N OKLAHOMA A A
N TEXAS A A S TEXAS A A W TEXAS A A
MINNESOTA A B IOWA A N MISSOURI A N
ARKANSAS A N LOUISIANA A A WISCONSIN A B
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 A W VIRGINIA A N
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA A A GEORGIA A A
FL PNHDL A A FL PENIN A A AK N SLOPE B N
AK ALEUTIAN B N AK WESTERN B B AK INT BSN A A
AK S INT A A AK SO COAST A 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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