765
FXUS06 KWBC 122002
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST TUE DECEMBER 12 2023
6-10 DAY OUTLOOK FOR DEC 18 - 22 2023
THE FORECASTED MID-LEVEL HEIGHT PATTERN LOOKS SIMILAR TO YESTERDAY. POSITIVE
500-HPA HEIGHT ANOMALIES ARE FORECAST ACROSS MUCH OF THE CONTIGUOUS U.S.
(CONUS) CENTERED ACROSS THE UPPER-MISSISSIPPI AND GREAT LAKES REGION. A WEAK
AREA OF NEGATIVE 500-HPA HEIGHT ANOMALIES IS FORECAST ACROSS FLORIDA AND PARTS
OF THE SOUTHEAST AS A SHORTWAVE TROUGH PROGRESSES ALONG THE GULF COAST. A
STRONGER AREA OF NEGATIVE MID-LEVEL HEIGHT ANOMALIES IS FORECAST NEAR THE WEST
COAST. THERE ARE SOME DISAGREEMENTS BETWEEN THE GEFS AND ECMWF ENSEMBLE MEANS
AS THE ECMWF DEVELOPS MORE OF A CUT-OFF LOW ALONG THE CALIFORNIA COAST WHILE
THE GEFS HAS A DEEPER FULL LATITUDE TROUGH STRETCHING BACK THROUGH ALASKA. DUE
TO RECENT MODEL SKILL, THE MANUAL 500-HPA HEIGHT BLEND LEANS A LITTLE MORE
TOWARDS THE GEFS. IN ALASKA, STRONG NEGATIVE 500-HPA HEIGHT ANOMALIES ARE
FORECAST ACROSS MUCH OF THE STATE CENTERED ACROSS THE BERING SEA BRINGING
SOUTHERLY FLOW INTO EASTERN ALASKA. IN HAWAII, NEAR-NORMAL 500-HPA HEIGHTS ARE
FAVORED.
THE PERSISTENT PACIFIC FLOW ACROSS THE CONUS LEADS TO A CONTINUATION OF MILD
TEMPERATURES FOR MUCH OF THE CONUS. THE LARGEST PROBABILITIES, MORE THAN 80%,
FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS THE NORTHERN AND CENTRAL
PLAINS AND UPPER-MISSISSIPPI VALLEY WHERE DAILY TEMPERATURES ARE LIKELY TO
AVERAGE MORE THAN 10 DEG. F ABOVE NORMAL. AN EXCEPTION OF THE FAVORED
ABOVE-NORMAL TEMPERATURES IS FOR PARTS OF THE SOUTHEAST AND FLORIDA WHERE A
SHORTWAVE TROUGH IS FORECAST TO PROVIDE A SLIGHT COOLING EFFECT. NEAR-NORMAL
TEMPERATURES ARE FAVORED ACROSS THIS AREA WITH A SLIGHT TILT TOWARDS
BELOW-NORMAL ACROSS THE SOUTHERN FLORIDA PENINSULA. ABOVE-NORMAL TEMPERATURES
ARE FAVORED ACROSS EASTERN ALASKA AS SOUTHERLY FLOW CONTINUES TO BRING WARM
MOIST AIR FROM THE PACIFIC INTO THE REGION WHILE NEAR-NORMAL IS FAVORED ACROSS
WESTERN ALASKA BEHIND THE TROUGH AXIS. IN HAWAII, NEAR-NORMAL IS FAVORED FOR
MOST OF THE ISLANDS AS THE MODEL CONSOLIDATION TOOLS SHIFTED TOWARDS A WARMER
SOLUTION RELATIVE TO PREVIOUS FORECASTS.
THE MOST LIKELY AREAS TO EXPERIENCE ABOVE NORMAL PRECIPITATION ARE CALIFORNIA
AND THE SOUTHWEST. MODEL SOLUTIONS ARE IN GOOD AGREEMENT THAT AN AMPLIFIED
MID-LEVEL TROUGH SHIFTS EASTWARD TOWARDS THE WEST COAST DURING THE 6 TO 10 DAY
PERIOD. REFORECAST TOOLS FROM THE GEFS AND ECMWF STRONGLY SUPPORT ABOVE-NORMAL
PRECIPITATION ACROSS THE CENTRAL CALIFORNIA COAST WITH ABOVE-NORMAL
PRECIPITATION BEING FAVORED FURTHER NORTH, INTO SOUTHERN WASHINGTON, AND EAST,
INTO COLORADO AND NEW MEXICO, RELATIVE TO YESTERDAY’S FORECAST AS ENHANCED
PACIFIC MOISTURE PUSHES FURTHER INTO NORTH AMERICA. ACROSS THE EAST,
BELOW-NORMAL PRECIPITATION IS FAVORED FOR MUCH OF THE COUNTRY EAST OF THE ROCKY
MOUNTAINS AS STRONG MID-LEVEL RIDGING AND SURFACE HIGH PRESSURE LIMIT CHANCES
FOR PRECIPITATION. THE SIGNAL FOR ABOVE-NORMAL PRECIPITATION IN FLORIDA HAS
TIMED OFF BUT MODELS ARE FORECASTING THE SHORTWAVE TROUGH TO TURN NORTHEAST UP
THE EAST COAST. THEREFORE, NEAR- TO SLIGHTLY ABOVE-NORMAL PRECIPITATION IS
FAVORED FOR PARTS OF THE IMMEDIATE EAST COAST. IN ALASKA, ABOVE-NORMAL
PRECIPITATION IS FAVORED FOR SOUTHERN PARTS OF THE STATE. NEAR-NORMAL IS
FAVORED ACROSS THE NORTH SLOPE. ABOVE-NORMAL PRECIPITATION IS FAVORED ACROSS
THE WESTERN HAWAIIAN ISLANDS WITH NEAR-NORMAL PRECIPITATION FAVORED FOR THE
EASTERN ISLANDS.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 25% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 8, 35% 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: ABOVE-AVERAGE, 4 OUT 5, GOOD
AGREEMENT AMONG THE MODEL TOOLS IS OFFSET SLIGHTLY BY DISAGREEMENTS WITH THE
STRENGTH OF THE TROUGH ALONG THE WEST COAST.
8-14 DAY OUTLOOK FOR DEC 20 - 26 2023
AS WITH THE 6 TO 10 DAY PERIOD, THE FORECASTED 500-HPA HEIGHT PATTERN REMAINS
IN GOOD AGREEMENT WITH THE EARLIER PERIOD AND YESTERDAY’S FORECAST. POSITIVE
500-HPA HEIGHT ANOMALIES REMAIN ACROSS THE EASTERN TWO-THIRDS OF THE CONUS WITH
THE PATTERN PROGRESSING EASTWARD RELATIVE TO YESTERDAY. NEGATIVE 500-HPA
HEIGHTS ARE FORECAST ACROSS MORE OF THE WEST COAST. HOWEVER, THE ECMWF
MAINTAINS A CUT-OFF LOW AS WITH THE 6 TO 10 DAY PERIOD WHILE THE GEFS CONTINUES
TO FORECAST A FULL LATITUDE TROUGH ACROSS THE WEST AND INTO ALASKA. STRONG
NEGATIVE 500-HPA HEIGHT ANOMALIES CONTINUE TO BE FORECAST ACROSS ALASKA.
POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST ACROSS THE HAWAIIAN ISLANDS.
ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR NEARLY THE ENTIRE UNITED STATES FOR
THE WEEK LEADING UP TO CHRISTMAS. THE STRONGEST CHANCES FOR ABOVE-NORMAL
TEMPERATURES, EXCEEDING 80%, IS ACROSS THE NORTHERN AND CENTRAL PLAINS, UPPER
AND MIDDLE-MISSISSIPPI VALLEY, AND THE GREAT LAKES. THE REMNANTS OF A SHORTWAVE
TROUGH EARLY IN THE PERIOD LINGER ACROSS PARTS OF FLORIDA, BRINGING CHANCES FOR
NEAR-NORMAL TO SOUTHERN FLORIDA. IN PARTS OF CALIFORNIA, THERE ARE REDUCED
CHANCES FOR ABOVE-NORMAL TEMPERATURES, BUT STILL FAVORED, WHERE ABOVE-NORMAL
PRECIPITATION MAY BRING MORE CLOUDS AND REDUCED DAYTIME TEMPERATURES. IN
ALASKA, SOUTHERLY FLOW IS FORECAST FOR EASTERN PORTIONS OF THE STATE BRINGING
ABOVE-NORMAL TEMPERATURES CHANCES. SOME NEAR TO BELOW-NORMAL IS FAVORED FOR
PARTS OF WESTERN ALASKA AND THE ALEUTIAN ISLANDS NEAR AND BEHIND THE TROUGH
AXIS. MEANWHILE, ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR HAWAII AS TOOLS
INDICATE A CONTINUED WARMING TREND RELATIVE TO PREVIOUS FORECASTS.
A SHORTWAVE TROUGH MOVING INLAND FROM THE EASTERN PACIFIC EARLY IN WEEK-2
FOLLOWED BY THE DEVELOPMENT OF A FULL LATITUDE TROUGH OVER THE NORTHEASTERN
PACIFIC LEADS TO INCREASED ABOVE-NORMAL PRECIPITATION PROBABILITIES ACROSS
CALIFORNIA ALONG WITH THE GREAT BASIN AND SOUTHWEST. IN THE CLIMATOLOGICALLY
WETTER AREAS OF THE PACIFIC NORTHWEST, REDUCED CHANCES FOR ABOVE-NORMAL
PRECIPITATION IS FORECAST. ABOVE-NORMAL PRECIPITATION IS SLIGHTLY FAVORED
ACROSS THE CENTRAL AND SOUTHERN PLAINS INTO THE MIDDLE AND LOWER-MISSISSIPPI
VALLEY AS ENSEMBLE MEANS SHOW AN INCREASING WET SIGNAL LATE IN WEEK-2,
DOWNSTREAM OF THE AMPLIFIED TROUGH NEAR THE WEST COAST. A BROAD RIDGE WAS
FORECAST TO BE CENTERED ACROSS THE GREAT LAKES YESTERDAY, IS FORECAST FURTHER
NORTH, CENTERED NEAR THE SOUTHERN HUDSON BAY, TODAY. THIS REDUCES CHANCES FOR
BELOW-NORMAL PRECIPITATION ACROSS PARTS OF THE NORTHERN PLAINS AND GREAT LAKES
RELATIVE TO YESTERDAY. ABOVE-NORMAL PRECIPITATION REMAINS FAVORED FOR MUCH OF
ALASKA WITH THE STRONGEST CHANCES IN SOUTHEAST ALASKA. NEAR-NORMAL IS FAVORED
ACROSS WESTERN ALASKA AND THE NORTH SLOPE. NEAR TO BELOW-NORMAL PRECIPITATION
IS FAVORED IN HAWAII WITH CONSOLIDATION TOOLS INDICATING BELOW-NORMAL AND THE
AUTOBLEND FAVORING NEAR-NORMAL PRECIPITATION.
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, 30% 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: 3 OUT 5, AVERAGE, FAIR AGREEMENT
AMONG THE MODEL TOOLS IS OFFSET BY A FAIRLY PROGRESSIVE PATTERN THAT PROVIDES A
MORE CHALLENGING ENVIRONMENT TO FORECAST.
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
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:
19991214 - 19991219 - 20041221 - 19591205 - 19961217
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:
19991217 - 20041220 - 19961216 - 19991212 - 19591204
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 18 - 22 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N 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 A ARIZONA A A COLORADO A N
NEW MEXICO A A N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS A B OKLAHOMA A B
N TEXAS A B S TEXAS A B W TEXAS A N
MINNESOTA A B IOWA A B MISSOURI A B
ARKANSAS A B LOUISIANA A B WISCONSIN A B
ILLINOIS A B MISSISSIPPI N B MICHIGAN A B
INDIANA A B OHIO A B KENTUCKY A B
TENNESSEE A B ALABAMA N B NEW YORK A N
VERMONT A N NEW HAMP A N MAINE A A
MASS A A CONN A A RHODE IS A A
PENN A B NEW JERSEY A N W VIRGINIA A B
MARYLAND A N DELAWARE A N VIRGINIA A B
N CAROLINA N B S CAROLINA N B GEORGIA N B
FL PNHDL N B FL PENIN B N AK N SLOPE N N
AK ALEUTIAN N A AK WESTERN N A AK INT BSN A A
AK S INT N A AK SO COAST N A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR DEC 20 - 26 2023
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 A NEVADA A A
W MONTANA A B E MONTANA A B WYOMING A A
UTAH A A ARIZONA A A COLORADO A A
NEW MEXICO A A N DAKOTA A B 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 B
INDIANA A A OHIO A B 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 B NEW JERSEY A B W VIRGINIA A B
MARYLAND A B DELAWARE A B VIRGINIA A B
N CAROLINA A B S CAROLINA A B GEORGIA A A
FL PNHDL A A FL PENIN N A AK N SLOPE N N
AK ALEUTIAN N A AK WESTERN N 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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