839
FXUS06 KWBC 182010
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 18 2023
6-10 DAY OUTLOOK FOR DEC 24 - 28 2023
TODAY’S 6-10 DAY DYNAMICAL MODEL HEIGHT FORECASTS ARE IN FAIRLY GOOD AGREEMENT
ACROSS THE FORECAST DOMAIN. A VERY DEEP MID-LEVEL TROUGH IS PREDICTED OVER THE
EASTERN PACIFIC, BERING SEA, AND ALASKA, WITH ONE LOBE OF THIS TROUGH FORECAST
ACROSS MOST OF THE ARCTIC OCEAN. THE MANUAL HEIGHT BLEND DEPICTS 500-HPA HEIGHT
DEPARTURES IN EXCESS OF -240 METERS OVER THE EASTERN PACIFIC, CENTERED IN THE
GENERAL VICINITY OF 45N-50N/150W. IN CONTRAST, LARGE POSITIVE 500-HPA HEIGHT
DEPARTURES ARE FORECAST FROM MOST OF CANADA ACROSS A LARGE PORTION OF THE
NORTHERN AND EASTERN CONUS, WITH PREDICTED HEIGHTS IN EXCESS OF +210 METERS
OVER ONTARIO AND WESTERN QUEBEC. AS IS OFTEN THE CASE, THE DYNAMICAL MODELS
HAVE DIFFICULTY TIMING INDIVIDUAL MID-LEVEL TROUGHS PROGRESSING THROUGH THE
SOUTHERN STREAM, AND TODAY IS NO EXCEPTION WITH SOLUTIONS PREDICTING A 5-DAY
MEAN TROUGH FROM THE SOUTHWEST TO THE LOWER MISSISSIPPI VALLEY. ENSEMBLE MEANS
PREDICT ABOVE-NORMAL 500-HPA HEIGHTS ACROSS THE HAWAIIAN ISLANDS.
THE PERSISTENT PACIFIC FLOW ACROSS THE CONUS LEADS TO A CONTINUATION OF MILD
TEMPERATURES FOR MUCH OF THE CONUS. THE LARGEST PROBABILITIES, MORE THAN 90%,
FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS THE UPPER GREAT LAKES REGION,
WITH THE GEFS FORECASTING 2-METER AVERAGE TEMPERATURES AT LEAST 15 DEGREES
ABOVE NORMAL FOR THE 6-10 DAY PERIOD. BELOW-NORMAL MEAN TEMPERATURES ARE
SLIGHTLY FAVORED ACROSS PART OF THE SOUTHWEST IN THE WAKE OF A MID-LEVEL TROUGH
AXIS, WITH MODEST SUPPORT FROM THE GEFS AND ECMWF REFORECAST TEMPERATURE TOOLS.
ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS EASTERN ALASKA AS SOUTHERLY FLOW
CONTINUES TO BRING WARM MOIST AIR FROM THE PACIFIC INTO THE REGION WHILE
BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS WESTERN ALASKA, CLOSER TO THE
TROUGH AXIS. IN HAWAII, ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR THE ENTIRE
ARCHIPELAGO, BASED ON THE TEMPERATURE CONSOLIDATION TOOL.
ABOVE-NORMAL PRECIPITATION IS FAVORED ACROSS THE PACIFIC NORTHWEST AND
CALIFORNIA INTO WESTERN NEVADA IN ADVANCE OF A DEEP MID-LEVEL TROUGH FORECAST
OVER THE EASTERN PACIFIC OCEAN. PROBABILITIES FAVORING ABOVE-NORMAL
PRECIPITATION EXCEED 50% FOR THE NORTHERN COAST OF CALIFORNIA. THIS IS BASED ON
THE CONSOLIDATED AND AUTOMATED PRECIPITATION TOOLS, AND THE ECMWF AND CANADIAN
REFORECAST PRECIPITATION TOOLS. BELOW-NORMAL PRECIPITATION CHANCES ARE ENHANCED
OVER THE INTERIOR NORTHWESTERN CONUS, FOR THE NORTHERN INTERMOUNTAIN REGION AND
NORTHERN ROCKIES TO THE NORTHERN HIGH PLAINS, WELL REMOVED FROM THE PRIMARY
STORM TRACK. SURFACE LOW PRESSURE INITIALLY OVER THE CENTRAL PORTION OF THE
LOWER 48 STATES IS PREDICTED TO TAP INTO ABUNDANT LOW-LEVEL GULF MOISTURE AS IT
PROGRESSES EASTWARD TOWARDS THE ATLANTIC COAST. THIS RESULTS IN SIGNIFICANTLY
INCREASED CHANCES OF ABOVE-NORMAL PRECIPITATION FOR THIS WIDESPREAD REGION,
WITH PROBABILITIES IN EXCESS OF 60% FOR THE SOUTHEAST COAST. MOST TOOLS SUPPORT
THIS BROAD EXTENT OF FAVORED ABOVE-NORMAL PRECIPITATION. BELOW-NORMAL
PRECIPITATION CHANCES ARE SLIGHTLY INCREASED OVER MAINE BASED ON THE
CONSOLIDATED PRECIPITATION TOOL. IN ALASKA, ABOVE-NORMAL PRECIPITATION IS
FAVORED FOR MOST OF THE STATE AS SOUTHERLY FLOW AROUND A MID-LEVEL TROUGH AND
SURFACE LOW-PRESSURE BRING INCREASED MOISTURE INTO THE STATE. BELOW-NORMAL
PRECIPITATION IS FAVORED OVER THE HAWAIIAN ISLANDS DURING THE 6-10 DAY FORECAST
PERIOD, BASED ON THE PRECIPITATION CONSOLIDATION TOOL.
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
FAIRLY GOOD AGREEMENT AMONG THE MID-LEVEL HEIGHT FORECASTS, OFFSET BY
DIFFERENCES AMONG THE PRECIPITATION TOOLS.
8-14 DAY OUTLOOK FOR DEC 26, 2023 - JAN 01, 2024
THE WEEK-2 500-HPA HEIGHT FORECASTS ARE IN GOOD AGREEMENT TODAY OVER THE
FORECAST DOMAIN. RELATIVE TO THE 6-10 DAY PERIOD, THE MEAN TROUGH PREDICTED
ACROSS ALASKA, THE BERING SEA, AND THE EASTERN PACIFIC IS PREDICTED TO WEAKEN
CONSIDERABLY DURING WEEK-2, WITH THE LARGEST NEGATIVE HEIGHT ANOMALIES NEAR
-180 METERS. A BROAD MID-LEVEL ANOMALOUS RIDGE PERSISTS OVER CANADA, THOUGH A
POLEWARD SHIFT IN THIS FEATURE IS INDICATED ON THE MANUAL HEIGHT BLEND. A
BROADER AND SOMEWHAT STRONGER MID-LEVEL TROUGH IS PREDICTED OVER THE
SOUTHEASTERN QUARTER OF THE CONUS, WITH MAXIMUM HEIGHT DEPARTURES IN EXCESS OF
-60 METERS. AS WAS THE CASE WITH THE EARLIER 6-10 DAY PERIOD, POSITIVE 500-HPA
HEIGHT ANOMALIES CONTINUE TO BE FORECAST ACROSS THE HAWAIIAN ISLANDS IN WEEK-2.
ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR APPROXIMATELY THE NORTHERN AND
CENTRAL THIRDS OF THE CONUS DURING THE WEEK-2 PERIOD. THE GREATEST CHANCES FOR
ABOVE-NORMAL TEMPERATURES, EXCEEDING 70%, IS OVER THE UPPER MISSISSIPPI VALLEY.
THIS IS WELL SUPPORTED BY MOST OF THE TEMPERATURE TOOLS. NEAR-NORMAL
TEMPERATURES ARE FAVORED OVER APPROXIMATELY THE SOUTHERN THIRD OF THE CONUS,
WITH SMALL PATCHES OF FAVORED BELOW-NORMAL TEMPERATURES POSSIBLE OVER FAR
SOUTHERN TEXAS AND SOUTHERN FLORIDA. IN ALASKA, SOUTHERLY FLOW IS FORECAST FOR
APPROXIMATELY THE EASTERN HALF OF THE STATE BRINGING ENHANCED ABOVE-NORMAL
TEMPERATURES CHANCES. CLOSER TO THE MEAN TROUGH AXIS JUST OFF THE WEST COAST OF
ALASKA, NEAR- TO BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS THE WESTERN HALF
OF ALASKA. MEANWHILE, THE CONSOLIDATION TOOL PREDICTS A MIX OF BELOW-, NEAR-,
AND ABOVE-NORMAL TEMPERATURES FOR HAWAII.
THE DEEP 500-HPA TROUGH PREDICTED OVER THE EASTERN PACIFIC ACCOMPANIED BY BROAD
ONSHORE FLOW LEADS TO INCREASED PRECIPITATION CHANCES OVER THE WEST COAST
STATES AND WESTERN NEVADA DURING WEEK-2. PROBABILITIES FAVORING ABOVE-NORMAL
PRECIPITATION EXCEED 60% OVER MUCH OF NORTHERN AND CENTRAL CALIFORNIA.
ABOVE-NORMAL PRECIPITATION IS ALSO FAVORED OVER THE EASTERN CONUS, WITH ODDS IN
EXCESS OF 50% NEAR THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND COASTS. MOST
PRECIPITATION TOOLS FAVOR THE IDEA OF AN EAST COAST STORM TRACK DURING THIS
PERIOD. ABOVE-NORMAL PRECIPITATION IS ALSO FAVORED OVER SOUTHERN TEXAS,
SUPPORTED BY THE CONSOLIDATION AND AUTOMATED PRECIPITATION TOOLS. BELOW-NORMAL
PRECIPITATION CHANCES ARE SLIGHTLY INCREASED FROM EASTERN PORTIONS OF THE
INTERMOUNTAIN REGION EASTWARD ACROSS THE ROCKIES, WITH ONE LOBE OF FAVORED
DRYNESS EXTENDING ACROSS THE NORTHERN PLAINS AND NORTHERN MINNESOTA, WHILE
ANOTHER LOBE OF FAVORED DRYNESS EXTENDS ACROSS THE SOUTH-CENTRAL PLAINS AND
LOWER MISSISSIPPI VALLEY. THIS HAS THE GENERAL SUPPORT OF MOST PRECIPITATION
TOOLS, BUT THE ODDS FAVORING BELOW-NORMAL PRECIPITATION ARE SLIGHT. FOR ALASKA,
ABOVE-NORMAL PRECIPITATION REMAINS FAVORED FOR MOST OF THE STATE IN ADVANCE OF
A DEEP MID-LEVEL TROUGH WITH THE GREATEST CHANCES IN SOUTH-CENTRAL AND
SOUTHEAST ALASKA. THE PRECIPITATION CONSOLIDATION TOOL FAVORS BELOW-NORMAL
PRECIPITATION FOR ALL THE HAWAIIAN ISLANDS DURING WEEK-2.
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: NEAR AVERAGE, 3 OUT OF 5 DUE TO
GENERALLY GOOD AGREEMENT AMONG THE 500-HPA HEIGHT FORECASTS, OFFSET BY GREATER
DIFFERENCES AMONG THE PRECIPITATION 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:
19901210 - 19571214 - 19861130 - 19841207 - 19791202
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:
19901210 - 19861203 - 19931127 - 19571212 - 19911212
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 24 - 28 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N OREGON A N NRN CALIF A A
SRN CALIF N A IDAHO A B NEVADA A N
W MONTANA A B E MONTANA A B WYOMING A A
UTAH N N ARIZONA N A COLORADO N A
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 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 A
VERMONT A N NEW HAMP A N MAINE A B
MASS A N CONN A A RHODE IS A N
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 N AK WESTERN B 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 DEC 26, 2023 - JAN 01, 2024
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A A
SRN CALIF A A IDAHO A B NEVADA A A
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A B ARIZONA A B COLORADO A B
NEW MEXICO N B N DAKOTA A B S DAKOTA A N
NEBRASKA A N KANSAS A N OKLAHOMA A B
N TEXAS N B S TEXAS N A W TEXAS N N
MINNESOTA A B IOWA A N MISSOURI A B
ARKANSAS N B LOUISIANA N B WISCONSIN A N
ILLINOIS A N MISSISSIPPI N B MICHIGAN A N
INDIANA A N OHIO A A KENTUCKY A N
TENNESSEE A N ALABAMA N N NEW YORK A A
VERMONT A A NEW HAMP A A MAINE A A
MASS A A 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 N A
FL PNHDL N A FL PENIN N A AK N SLOPE N A
AK ALEUTIAN B N AK WESTERN B N 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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