548
FXUS06 KWBC 012102
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 01 2023
6-10 DAY OUTLOOK FOR DEC 07 - 11 2023
THE FORECAST MEAN PATTERN IS SIMILAR TO YESTERDAY, BUT THERE IS SIGNIFICANTLY
MORE SPREAD IN THE GUIDANCE, AND THIS INCONSISTENCY LOWERS CONFIDENCE. THE
GEFS, CANADIAN, AND ECMWF ENSEMBLE MEANS START OFF IN GOOD AGREEMENT, SHOWING
THAT THE 6 TO 10 DAY PERIOD STARTS WITH AN AMPLIFIED 500-HPA TROUGH OVER ALASKA
WHICH EXTENDS SOUTHWARD IN THE EASTERN NORTH PACIFIC JUST WEST OF THE WESTERN
CONTIGUOUS U.S. (CONUS). GUIDANCE TODAY SHOWS A SHARPER TROUGH OVER ALASKA THAN
YESTERDAY DUE TO A STRONG, SHARP MID-LEVEL RIDGE BEGINNING TO BUILD FROM THE
NORTH PACIFIC INTO EASTERN RUSSIA AND THE WESTERN ALEUTIANS. DOWNSTREAM, A
MODERATELY AMPLIFIED MID-LEVEL RIDGE IS EXPECTED TO BE CENTERED OVER THE PLAINS
OR EASTERN ROCKIES, WITH A LARGE AREA OF ABOVE-NORMAL 500-HPA HEIGHTS EXTENDING
FROM THE DESERT SOUTHWEST EASTWARD TO THE APPALACHIANS. IN THE WESTERN NORTH
ATLANTIC, A STRONG TROUGH SHOULD BE HEADING EASTWARD AWAY FROM THE EASTERN
CONUS, WITH BELOW-NORMAL 500-HPA HEIGHTS LINGERING OVER NEW ENGLAND. GUIDANCE
GENERALLY SHOWS THESE FEATURES TO BE PROGRESSIVE AT THE MID-LATITUDES, BUT
DIFFERENCES IN THE EVOLUTION OF THE 500-HPA ANOMALY PATTERN BEGIN TO SHOW UP IN
THE MODELS AROUND THE MIDDLE OF THE PERIOD, AND GUIDANCE CONTINUES TO DIVERGE
WITH TIME.
A PROGRESSIVE PATTERN OF WEAKLY- TO MODERATELY-AMPLIFIED 500-HPA FEATURES
SHOULD TRACK STEADILY ACROSS THE CONUS, RESULTING IN A RELATIVELY ZONAL MEAN
PATTERN AT THE MID-LATITUDES. MORE PERSISTENT MID-LEVEL FEATURES ARE PRESENT AT
HIGHER LATITUDES, BUT THE TOOLS ARE NOT IN GOOD AGREEMENT ON THE EVOLUTION OF
THESE FEATURES. DESPITE THESE DIFFERENCES, MOST OF THE TOOLS IMPLY A SLIGHTLY
MORE PROGRESSIVE PATTERN THAN EXPECTED YESTERDAY AT HIGHER LATITUDES, WITH THE
AMPLITUDE OF 500-HPA ANOMALIES DECLINING WITH TIME. BY DAY 10, THE ENSEMBLE
MEANS ARE IN POOR AGREEMENT, BUT GENERALLY SHOW POSITIVE 500-HPA HEIGHT
ANOMALIES FROM EASTERN RUSSIA INTO WESTERN ALASKA, SOME DEGREE OF MID-LEVEL
TROUGHING DOWNSTREAM OVER OR NEAR EASTERN ALASKA, A WEAK TO MODERATE TROUGH
CENTERED SOMEWHERE CLOSE TO THE CENTRAL CONUS, AND ABOVE-NORMAL 500-HPA HEIGHTS
ACROSS NORTHEASTERN CANADA AND GREENLAND.
THE NORTH PACIFIC EXTENSION OF THE TROUGH CENTERED OVER ALASKA TRACKS EASTWARD
INTO THE PACIFIC NORTHWEST EARLY IN THE PERIOD, RESULTING IN AN ENHANCED FLOW
OF MOIST, MILD PACIFIC AIR ACROSS A LARGE PART OF THE CONUS. GUIDANCE IS IN
POOR AGREEMENT ON THE EVOLUTION OF THE MID-LEVEL TROUGH. A RANGE OF POTENTIAL
SOLUTIONS IS SHOWN IN THE GUIDANCE, BUT MOST WOULD WEAKLY FAVOR ABOVE-NORMAL
PRECIPITATION ACROSS A LARGE PART OF THE CONUS, EXCEPTING ONLY PARTS OF THE
SOUTHWEST AND THE EASTERN SEABOARD. DESPITE THE SIZE OF THE REGION WHERE
ABOVE-NORMAL PRECIPITATION IS FAVORED, ODDS EXCEEDING 40 PERCENT ARE RESTRICTED
TO PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS AND DEEP SOUTH TEXAS. THE
GUIDANCE DOES NOT STRONGLY FAVOR ABNORMAL WETNESS IN THE PACIFIC NORTHWEST AS
IT DID YESTERDAY, IN PART BECAUSE SOME OF THE HEAVIER PRECIPITATION SHOULD FALL
BEFORE DAY 6.
WITH MILD PACIFIC AIR COVERING MUCH OF THE NATION, ABOVE-NORMAL TEMPERATURES
ARE FAVORED OVER MOST OF THE CONUS FROM PARTS OF THE EASTERN SEABOARD THROUGH
THE CENTRAL AND SOUTHERN ROCKIES AND INTO THE SOUTHWEST. THE BEST CHANCES FOR
ABOVE-NORMAL TEMPERATURES (OVER 70 PERCENT) WILL BE AREAS UNDER OR NEAR THE
CENTRAL CONUS MID-LEVEL RIDGE AXIS, COVERING MOST OF THE GREAT PLAINS,
MISSISSIPPI VALLEY, UPPER MIDWEST, GREAT LAKES, AND LOWER OHIO VALLEY. FARTHER
EAST, AHEAD OF THE ADVANCING MID-LEVEL RIDGE, ENHANCED CHANCES FOR WARMER THAN
NORMAL WEATHER EXTEND INTO THE MIDDLE ATLANTIC STATES, BUT REMAIN OUTSIDE NEW
ENGLAND, THE IMMEDIATE SOUTHEAST COAST, AND THE FLORIDA PENINSULA. IN THE
WESTERN CONUS, THE RAW AND BIAS-CORRECTED TOOLS DERIVED FROM THE ENSEMBLES
DEPICT CONSIDERABLY COLDER WEATHER THAN MOST OTHER GUIDANCE, RESULTING IN
FAVORED NEAR-NORMAL TEMPERATURES FROM THE GREAT BASIN NORTHWARD TO THE CANADIAN
BORDER AND WESTWARD TO THE PACIFIC COAST.
THE STRENGTHENING RIDGE CENTERED NEAR THE BERING STRAIT IS LIKELY TO RESULT IN
BELOW-NORMAL TEMPERATURES ACROSS MUCH OF SOUTHERN AND CENTRAL ALASKA, WITH
NEAR- OR ABOVE-NORMAL TEMPERATURES FAVORED ELSEWHERE ASSOCIATED WITH MODEST
ONSHORE FLOW. DOWNSTREAM, THE MID-LEVEL TROUGH LOOKS TO BE DEEPER AND CENTERED
FARTHER WEST THAN YESTERDAY, RESULTING IN ENHANCED CHANCES FOR ABOVE NORMAL
PRECIPITATION OVER MUCH OF THE STATE, ESPECIALLY IN SOUTHEASTERN AREAS NEAR A
MEAN SURFACE LOW PRESSURE CENTER.
THE 6-10 DAY TEMPERATURE AND PRECIPITATION OUTLOOKS FOR HAWAII ARE BASED ON THE
CONSOLIDATION TOOL AND SEA SURFACE TEMPERATURES. ABOVE-NORMAL TEMPERATURES ARE
FAVORED FOR THE ENTIRE HAWAIIAN ISLAND CHAIN, AND WITH A WEAK MID-LEVEL RIDGE
CENTERED WEST OF THE STATE, ODDS SLIGHTLY FAVOR ABOVE-NORMAL PRECIPITATION IN
WESTERN AREAS, AND BELOW-NORMAL PRECIPITATION FARTHER EAST ON THE BIG ISLAND,
CLOSER TO ABOVE-NORMAL 500-HPA HEIGHTS.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 55% OF TODAY'S GFS
SUPERENSEMBLE MEAN CENTERED ON DAY 8, 7% OF TODAY'S OPERATIONAL 6Z GFS CENTERED
ON DAY 8, 15% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, 8% OF
TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8, AND 15% 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, DUE TO
INCONSISTENCIES AMONG THE TOOLS ON THE EVOLVING 500-HPA PATTERN WHICH GETS
WORSE AS THE PERIOD PROGRESSES.
8-14 DAY OUTLOOK FOR DEC 09 - 15 2023
THE GEFS, ECMWF, AND CANADIAN ENSEMBLE MEANS ARE IN POOR AGREEMENT ON THE
EVOLUTION OF FEATURES DURING WEEK-2, CONTINUING THE TREND THAT STARTED DURING
THE 6- TO 10-DAY PERIOD. AT LOWER LATITUDES, GUIDANCE SHOWS THE LONGWAVE
PATTERN REMAINING PROGRESSIVE. THE RIDGE UPSTREAM OVER THE ALEUTIANS COULD
EVENTUALLY LEAD TO STRENGTHENING ARCTIC HIGH PRESSURE AT THE HIGH LATITUDES OF
WESTERN NORTH AMERICA. THIS EVOLVING PATTERN WILL HAVE TO BE CLOSELY MONITORED
FOR A POTENTIAL PATTERN CHANGE BEYOND THE WEEK-2 PERIOD. THE TEMPERATURE
OUTLOOK, VALID FOR DECEMBER 9 TO 15, CONTINUES TO FAVOR ABOVE-NORMAL
TEMPERATURES FOR THE CENTRAL AND EASTERN CONUS DUE TO THE EXPECTED DOMINANCE OF
MILD PACIFIC AIR, BUT THE ODDS ARE REDUCED COMPARED TO YESTERDAY DUE TO POOR
MODEL AGREEMENT. WITH THE MID-LEVEL RIDGE AXIS MOVING EASTWARD, 500-HPA HEIGHTS
SHOULD BE DROPPING ACROSS THE WESTERN CONUS. SO DESPITE THE BROAD DIFFERENCES
DEPICTED BY THE TOOLS, TEMPERATURES ARE EXPECTED TO AVERAGE CLOSER TO NORMAL
FROM THE ROCKIES WESTWARD.
SLIGHTLY-INCREASED ABOVE-NORMAL PRECIPITATION PROBABILITIES ARE FORECAST ACROSS
A LARGE PART OF THE NATION, BUT ODDS EXCEED 40 PERCENT ONLY IN PARTS OF THE
CENTRAL HIGH PLAINS AND THE MIDDLE MISSISSIPPI VALLEY. DETERMINISTIC MODELS
SHOW INCREASED ODDS FOR A STORM SYSTEM AND FRONTAL BOUNDARY TO ENHANCE
PRECIPITATION IN THE LATTER AREA, ALONG WITH THE CANADIAN ENSEMBLE MEAN. IN THE
CONUS, ONLY THE DESERT SOUTHWEST DOES NOT HAVE ENHANCED ODDS FOR ABOVE-NORMAL
PRECIPITATION.
DOWNSTREAM OF THE AMPLIFIED RIDGE AXIS, BELOW-NORMAL PRECIPITATION IS FAVORED
FOR SOUTHWESTERN ALASKALA. BASED ON A CONSENSUS OF THE TOOLS, SLIGHTLY ELEVATED
ABOVE-NORMAL PRECIPITATION PROBABILITIES ARE FORECAST THROUGHOUT CENTRAL AND
EASTERN ALASKA UNDER SUBNORMAL 500-HPA HEIGHT DOWNSTREAM FROM THE AMPLIFIED
ALEUTIAN RIDGE. NORTH TO NORTHEAST SURFACE FLOW SUPPORTS INCREASED BELOW-NORMAL
TEMPERATURE PROBABILITIES ACROSS MOST OF THE MAINLAND EXCEPT THE FAR NORTHERN
TIER, WITH ODDS TOPPING 50 PERCENT IN SOUTH-CENTRAL AND SOUTHWESTERN PARTS OF
THE MAINLAND.
THE WEEK-2 TEMPERATURE OUTLOOK FOR HAWAII IS BASED ON THE CONSOLIDATION TOOL
AND SEA SURFACE TEMPERATURES AND FAVORS WARMER THAN NORMAL CONDITIONS ACROSS
THE STATE. WITH A WEAK MID-LEVEL TROUGH REMAINING TO THE WEST OF THE ISLANDS,
ODDS SLIGHTLY FAVOR WETNESS IN WESTERN AREAS, AND SUBNORMAL RAINFALL ON THE
EAST SIDE OF THE STATE.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 15% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 55% OF TODAY'S GFS SUPERENSEMBLE MEAN
CENTERED ON DAY 11, 8% OF TODAY'S OPERATIONAL 6Z GFS CENTERED ON DAY 11, 14% OF
TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 8% OF TODAY'S 0Z
CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: BELOW AVERAGE, 1 OUT OF 5, DUE TO
INCONSISTENCIES IN GUIDANCE LEADING TO AN UNCERTAIN FORECAST.
FORECASTER: RICH TINKER
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:
19571202 - 19921204 - 19891123 - 20001117 - 19781129
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:
19571202 - 19891123 - 19921203 - 19511122 - 20001119
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 07 - 11 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON N A OREGON N A NRN CALIF N N
SRN CALIF A B IDAHO N A NEVADA N A
W MONTANA N A E MONTANA A A WYOMING A A
UTAH A A ARIZONA A B COLORADO A A
NEW MEXICO A N 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 A
INDIANA A A OHIO A A KENTUCKY A A
TENNESSEE A N ALABAMA A N NEW YORK A A
VERMONT N N NEW HAMP N N MAINE N N
MASS N N CONN N N RHODE IS N N
PENN A N NEW JERSEY A N W VIRGINIA A N
MARYLAND A N DELAWARE A B VIRGINIA A N
N CAROLINA A B S CAROLINA A B GEORGIA A N
FL PNHDL N N FL PENIN B N AK N SLOPE N A
AK ALEUTIAN B B AK WESTERN B N AK INT BSN N A
AK S INT B A AK SO COAST B A AK PNHDL N A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 09 - 15 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON N A OREGON N A NRN CALIF N A
SRN CALIF A N IDAHO N A NEVADA N N
W MONTANA N A E MONTANA A A WYOMING N A
UTAH N A ARIZONA N N COLORADO N A
NEW MEXICO A A 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 A
INDIANA A A OHIO A A KENTUCKY A A
TENNESSEE A A ALABAMA A A NEW YORK A N
VERMONT A N NEW HAMP A N MAINE A N
MASS A N CONN A A RHODE IS A A
PENN A A NEW JERSEY A A W VIRGINIA A A
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 N A
AK ALEUTIAN B B AK WESTERN B N AK INT BSN B N
AK S INT B N AK SO COAST B A AK PNHDL B 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.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page