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FXUS06 KWBC 302002
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST MON DECEMBER 30 2024
6-10 DAY OUTLOOK FOR JAN 05 - 09 2025
A PATTERN CHANGE IS FORECAST DURING EARLY JANUARY AS A FULL-LATITUDE 500-HPA
RIDGE EXTENDS NORTH FROM THE WEST COAST TO ALASKA AND HIGH LATITUDE BLOCKING
BECOMES ESTABLISHED. THE GEFS DEPICTS A HIGHLY NEGATIVE ARCTIC OSCILLATION
(AO), CLOSE TO -4 STANDARD DEVIATIONS, BY THE SECOND WEEK OF JANUARY. THE GEFS,
ECENS, AND CMCE ARE IN EXCELLENT AGREEMENT AND REMAIN CONSISTENT THAT ARCTIC
HIGH PRESSURE BEGINS TO SHIFT SOUTH FROM CANADA BY DAY 6, JANUARY 5. THE
ANOMALOUS MID-LEVEL TROUGH, CROSS POLAR FLOW, AND ARCTIC HIGH PRESSURE SHIFTING
SOUTHWARD STRONGLY SUPPORT BELOW-NORMAL TEMPERATURES ACROSS THE EASTERN
TWO-THIRDS OF THE CONTIGUOUS U.S. (CONUS). LARGE BELOW-NORMAL TEMPERATURE
PROBABILITIES (MORE THAN 70 PERCENT) ARE FORECAST FROM THE NORTHERN AND CENTRAL
GREAT PLAINS EASTWARD TO THE OHIO VALLEY AND MID-ATLANTIC WHERE THE ENSEMBLE
MEAN SOLUTIONS HAVE 5-DAY TEMPERATURES AVERAGING NEAR OR MORE THAN 10 DEGREES F
BELOW NORMAL. A TWO-CATEGORY CHANGE FROM YESTERDAY WITH FAVORED ABOVE TO
BELOW-NORMAL TEMPERATURES FOR PARTS OF TEXAS WAS NECESSARY AS ANOMALOUS WARMTH
TIMES OFF EARLIER TODAY. AN AMPLIFIED 500-HPA RIDGE AND POSITIVE HEIGHT
DEPARTURES SUPPORT INCREASED ABOVE-NORMAL TEMPERATURES ACROSS THE PACIFIC
NORTHWEST, GREAT BASIN, CALIFORNIA, AND SOUTHWEST.
MODEL GUIDANCE HAS BEEN CONSISTENT SINCE LAST WEEK DEPICTING A SHORTWAVE TROUGH
EJECTING FROM THE WEST AND LEADING TO SURFACE LOW DEVELOPMENT ACROSS THE GREAT
PLAINS ON JANUARY 4 OR 5. THIS SURFACE LOW IS FORECAST TO TRACK QUICKLY
EASTWARD TO THE OHIO VALLEY AND MAY REDEVELOP NEAR THE MID-ATLANTIC COAST BY
JANUARY 6. THIS SHORTWAVE TROUGH AND SURFACE LOW PRESSURE SYSTEM FAVOR
ABOVE-NORMAL PRECIPITATION ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS. BY DAY
8 (JANUARY 7), THE SURFACE LOW IS FORECAST TO MOVE AWAY FROM THE EAST COAST. AN
AMPLIFYING 500-HPA RIDGE NEAR THE WEST COAST LEADS TO AN INCREASED CHANCE OF
BELOW-NORMAL PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST,
CALIFORNIA, AND THE SOUTHWEST.
ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT FEATURING AN AMPLIFIED 500-HPA
TROUGH (RIDGE) OVER THE WESTERN ALEUTIANS (EASTERN MAINLAND ALASKA). THIS
LONGWAVE PATTERN YIELDS INCREASED ABOVE-NORMAL TEMPERATURES PROBABILITIES FOR
MUCH OF ALASKA. ENHANCED ONSHORE FLOW FAVORS ABOVE-NORMAL PRECIPITATION FOR THE
MAJORITY OF ALASKA EXCEPT FOR THE NORTH SLOPE WHERE NEAR- TO BELOW-NORMAL
PRECIPITATION IS MORE LIKELY.
BASED ON THE GEFS AND ECENS, ABOVE-NORMAL TEMPERATURES ARE STRONGLY FAVORED FOR
HAWAII. THE CONSOLIDATION SUPPORTS ELEVATED ABOVE-NORMAL PRECIPITATION
PROBABILITIES FOR MUCH OF THE STATE EXCEPT THE SOUTHEASTERN BIG ISLAND.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 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 30% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY
8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: FORECAST CONFIDENCE: ABOVE
AVERAGE, 4 OUT OF 5, DUE TO A HIGHLY AMPLIFIED LONGWAVE PATTERN AND GOOD
AGREEMENT AMONG THE TEMPERATURE AND PRECIPITATION TOOLS.
8-14 DAY OUTLOOK FOR JAN 07 - 13 2025
THE HIGHLY AMPLIFIED LONGWAVE PATTERN, WITH A FULL-LATITUDE RIDGE EXTENDING
FROM THE WEST COAST NORTH TO THE BEAUFORT SEA AND A VERY ANOMALOUS TROUGH OVER
THE EASTERN HALF OF THE CONUS, IS FORECAST TO PERSIST THROUGH MID-JANUARY. THE
GEFS AND ECENS FEATURE NEGATIVE 500-HPA HEIGHT DEPARTURES OF -180 METERS OVER
THE MID-ATLANTIC FOR THE 7-DAY PERIOD. ALSO, SUBSTANTIAL 500-HPA HEIGHT
ANOMALIES OF -30 METERS EXTEND AS FAR SOUTH AS THE FLORIDA KEYS. THESE ENSEMBLE
MEANS DEPICT THE MID-LEVEL TROUGH PEAKING ON DAYS 11 AND 12 (JANUARY 10-11)
WHEN 500-HPA HEIGHT ANOMALIES EXCEED -240 METERS CENTERED ACROSS THE
MID-ATLANTIC. ANOTHER REMARKABLE FEATURE IN THE 500-HPA HEIGHT ANOMALY FIELD IS
THE PREDICTED +240 METER DEPARTURE OVER SOUTHERN GREENLAND WHICH IS ASSOCIATED
WITH THE STRONG HIGH LATITUDE BLOCK. EARLY IN WEEK-2, ARCTIC HIGH PRESSURE IS
FORECAST TO EXPAND SOUTHWARD AND OVERSPREAD NEARLY ALL OF THE CENTRAL AND
EASTERN CONUS WHERE BELOW-NORMAL TEMPERATURES ARE FAVORED. BASED ON EXCELLENT
MODEL AGREEMENT AND CONSISTENCY, THE GEFS AND ECENS REFORECAST TOOLS, AND THE
ANALOG TOOL DERIVED FROM THE MANUAL 500-HPA HEIGHT BLEND, A LARGE AREA WITH
BELOW-NORMAL TEMPERATURE PROBABILITIES EXCEEDING 80 PERCENT EXTENDS FROM THE
OHIO VALLEY SOUTH TO THE GULF COAST. A GREATER THAN 90 PERCENT CHANCE OF
BELOW-NORMAL TEMPERATURES IS CENTERED OVER THE SOUTHERN APPALACHIANS AND
TENNESSEE VALLEY WITH THE GEFS AND ECENS PREDICTING 7-DAY TEMPERATURES
AVERAGING MORE THAN 15 DEGREES F BELOW NORMAL FOR THOSE AREAS. THE INCREASED
CHANCE OF BELOW-NORMAL TEMPERATURES EXTENDS WEST TO THE CONTINENTAL DIVIDE, BUT
FORECAST CONFIDENCE IS LOWEST FOR THE HIGH PLAINS SINCE THE ENSEMBLE MEAN
SOLUTIONS DEPICT A WARMING TREND LATER IN WEEK-2. FARTHER TO THE WEST,
ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR THE GREAT BASIN, PACIFIC NORTHWEST,
CALIFORNIA, AND THE SOUTHWEST DUE TO POSITIVE 500-HPA HEIGHT DEPARTURES.
ONCE A LOW PRESSURE SYSTEM EXITS THE EASTERN CONUS ON DAY 7, A DRIER FORECAST
IS LIKELY FOR A MAJORITY OF THIS REGION AS ANOMALOUS NORTHERLY FLOW BECOMES
ESTABLISHED. A TWO-CATEGORY CHANGE FROM ABOVE-NORMAL PRECIPITATION IN THE 6-10
DAY OUTLOOK TO BELOW-NORMAL PRECIPITATION IN THE 8-14 DAY OUTLOOK IS NECESSARY
FOR PORTIONS OF THE EASTERN AND CENTRAL CONUS DUE TO THE TIMING OFF OF
PRECIPITATION BY DAY 8. NEAR-NORMAL PRECIPITATION IS FAVORED DOWNWIND OF THE
GREAT LAKES AND ALONG THE CENTRAL APPALACHIANS DUE TO THE POTENTIAL FOR
LAKE-EFFECT SNOW AND UPSLOPE FLOW, RESPECTIVELY. UPSLOPE FLOW AT THE BEGINNING
OF WEEK-2 ALONG WITH AN INCREASED CHANCE OF SHORTWAVE TROUGHS TO TRACK
SOUTHEASTWARD SLIGHTLY FAVOR ABOVE-NORMAL PRECIPITATION ACROSS THE NORTHERN TO
CENTRAL GREAT PLAINS. AT THE BASE OF THE HIGH AMPLITUDE TROUGH OVER EASTERN
NORTH AMERICA, THE GEFS AND ECENS DEPICT ONE OR MORE LOW PRESSURE SYSTEM
TRACKING ACROSS SOUTHERN TEXAS AND THE FLORIDA PENINSULA WHICH ELEVATES
ABOVE-NORMAL PRECIPITATION PROBABILITIES FOR THESE AREAS. ALONG AND TO THE EAST
OF THE HIGH AMPLITUDE RIDGE AXIS, BELOW-NORMAL PRECIPITATION IS FAVORED FOR THE
PACIFIC NORTHWEST, GREAT BASIN, CALIFORNIA, AND THE SOUTHWEST.
DOWNSTREAM OF THE AMPLIFIED TROUGH OVER THE ALEUTIANS, ENHANCED SOUTHERLY FLOW
FAVORS ABOVE-NORMAL TEMPERATURES AND ABOVE-NORMAL PRECIPITATION FOR ALL OF
ALASKA. THE LARGEST ABOVE-NORMAL PRECIPITATION PROBABILITIES (MORE THAN 50
PERCENT) ARE FORECAST FOR SOUTHEASTERN ALASKA WHICH IS SUPPORTED BY THE
PREDICTED SURFACE FLOW AND PRECIPITATION TOOLS.
BASED ON THE GEFS AND ECENS, INCREASED CHANCES OF ABOVE-NORMAL TEMPERATURES AND
ABOVE-NORMAL PRECIPITATION ARE FORECAST FOR HAWAII.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 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 30% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON
DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: FORECAST CONFIDENCE: ABOVE
AVERAGE, 4 OUT OF 5, DUE TO A HIGHLY AMPLIFIED LONGWAVE PATTERN AND EXCELLENT
AGREEMENT AMONG THE TEMPERATURE TOOLS. HOWEVER, THERE IS UNCERTAINTY IN THE
PRECIPITATION OUTLOOK FOR THE GULF COAST STATES AND EASTERN CONUS DUE TO THE
POTENTIAL FOR LOW PRESSURE DEVELOPMENT.
FORECASTER: BRAD PUGH
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
JANUARY 16.
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:
19591226 - 20061212 - 20031224 - 19521210 - 20080109
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:
20031225 - 19871209 - 19521209 - 19691209 - 19591225
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR JAN 05 - 09 2025
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A B
SRN CALIF A B IDAHO N N NEVADA A B
W MONTANA N A E MONTANA B A WYOMING B A
UTAH N N ARIZONA A B COLORADO B A
NEW MEXICO N A N DAKOTA B A S DAKOTA B A
NEBRASKA B A KANSAS B A OKLAHOMA B A
N TEXAS B A S TEXAS B A W TEXAS B A
MINNESOTA B N IOWA B A MISSOURI B A
ARKANSAS B A LOUISIANA B A WISCONSIN B A
ILLINOIS B A MISSISSIPPI B A MICHIGAN B A
INDIANA B A OHIO B A KENTUCKY B A
TENNESSEE B A ALABAMA B A NEW YORK B A
VERMONT B B NEW HAMP B B MAINE B B
MASS B N CONN B A RHODE IS B A
PENN B A NEW JERSEY B A W VIRGINIA B A
MARYLAND B A DELAWARE B A VIRGINIA B A
N CAROLINA B A S CAROLINA B A GEORGIA B A
FL PNHDL B A FL PENIN B A AK N SLOPE N N
AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A
AK S INT A A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR JAN 07 - 13 2025
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A B
SRN CALIF A B IDAHO A B NEVADA A B
W MONTANA N B E MONTANA B A WYOMING N A
UTAH A B ARIZONA A B COLORADO B A
NEW MEXICO B B N DAKOTA B A S DAKOTA B A
NEBRASKA B A KANSAS B N OKLAHOMA B B
N TEXAS B B S TEXAS B B W TEXAS B B
MINNESOTA B N IOWA B B MISSOURI B B
ARKANSAS B B LOUISIANA B B WISCONSIN B B
ILLINOIS B B MISSISSIPPI B B MICHIGAN B N
INDIANA B B OHIO B B KENTUCKY B B
TENNESSEE B B ALABAMA B B NEW YORK B N
VERMONT B N NEW HAMP B N MAINE B N
MASS B N CONN B N RHODE IS B N
PENN B N NEW JERSEY B N W VIRGINIA B N
MARYLAND B N DELAWARE B N VIRGINIA B N
N CAROLINA B B S CAROLINA B B GEORGIA B B
FL PNHDL B N FL PENIN B A AK N SLOPE A A
AK ALEUTIAN A A AK WESTERN A A 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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