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FXUS06 KWBC 241916
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT TUE APRIL 24 2018
6-10 DAY OUTLOOK FOR APR 30 - MAY 04, 2018
TODAY'S ENSEMBLE MEAN FORECASTS ARE IN GOOD AGREEMENT ON THE PREDICTED
CIRCULATION PATTERN DURING THE 6-10 DAY PERIOD. HIGH RESOLUTION RUNS AND
ENSEMBLE MODELS PREDICT A RIDGE OVER THE EASTERN CONUS AND A TROUGH OVER THE
WESTERN CONUS DURING THE 6-10 DAY PERIOD. RECENT ECMWF ENSEMBLE MEANS AND HIGH
RESOLUTION ECMWF MODEL RUNS PREDICT WEAKER POSITIVE 500-HPA ANOMALIES OVER THE
EASTERN CONUS COMPARED TO RECENT GEFS ENSEMBLE MEANS AND HIGH RESOLUTION MODEL
RUNS. PREDICTED 500-HPA ANOMALIES OVER THE GREAT PLAINS ARE NEAR ZERO IN THE
ECMWF AND POSITIVE IN THE GEFS. THE 0Z ECMWF AND THE 6Z GEFS ENSEMBLE MEANS ARE
EQUALLY WEIGHTED, WHILE THE CANADIAN ENSEMBLE IS GIVEN LESS WEIGHT, IN THE
MANUAL 500-HPA HEIGHT BLEND, CONSISTENT WITH RECENT ANOMALY CORRELATION SKILL.
ALL RECENT ENSEMBLE MEANS PREDICT RIDGING OVER ALASKA AND THE GULF OF ALASKA,
WITH THE ECMWF ENSEMBLE MEAN INDICATING GREATER POSITIVE 500-HPA HEIGHT
ANOMALIES THAN THE GEFS AND CANADIAN ENSEMBLE MEANS.
UNDER A PREDICTED RIDGE AND POSITIVE 500-HPA HEIGHT ANOMALIES, ABOVE NORMAL
TEMPERATURES ARE MOST LIKELY FROM THE CENTRAL AND SOUTHERN PLAINS ACROSS THE
CENTRAL AND UPPER MISSISSIPPI VALLEY INTO THE MID-ATLANTIC AND NORTHEAST. BELOW
NORMAL TEMPERATURES ARE MOST LIKELY FOR PARTS OF THE WESTERN CONUS, INCLUDING
THE CENTRAL AND SOUTHERN ROCKY MOUNTAINS AND WESTERN AREAS OF THE NORTHERN
PLAINS. PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE SLIGHTLY ENHANCED OVER
PARTS OF THE SOUTHEAST AS INDICATED BY A CONSOLIDATION OF REFORECAST-CALIBRATED
TEMPERATURES FROM THE ECMWF AND GEFS ENSEMBLES. ABOVE NORMAL TEMPERATURES ARE
MOST LIKELY FOR WESTERN AND NORTHERN ALASKA, AS WELL AS THE ALASKA PANHANDLE,
UNDER A PREDICTED RIDGE.
REFORECAST-CALIBRATED PRECIPITATION FORECASTS FROM THE ECMWF AND GEFS ENSEMBLES
ARE IN GENERAL AGREEMENT ON AREAS OF ENHANCED PROBABILITIES OF ABOVE NORMAL
PRECIPITATION. IN ASSOCIATION WITH A PREDICTED TROUGH, MODELS PREDICT ENHANCED
PROBABILITIES OF ABOVE NORMAL PRECIPITATION OVER MUCH OF THE INTERMOUNTAIN
WEST, AS WELL AS SOME AREAS OF SOUTHERN CALIFORNIA. PROBABILITIES OF ABOVE
NORMAL PRECIPITATION ARE ENHANCED FOR PARTS OF THE SOUTHERN PLAINS AND THE
MISSISSIPPI VALLEY, WITH NORTHWARD MOISTURE FLOW AROUND SURFACE HIGH PRESSURE.
THE GEFS ENSEMBLE PREDICTS ENHANCED PROBABILITIES OF ABOVE NORMAL PRECIPITATION
IN AREAS OF THE SOUTHERN AND CENTRAL PLAINS FURTHER WEST THAN THE ECMWF
ENSEMBLE, CONSISTENT WITH A STRONGER RIDGE OVER THE EASTERN CONUS IN THE GEFS.
NEAR NORMAL PRECIPITATION WAS INDICATED IN THE 6-10 DAY OUTLOOK FOR THESE
REGIONS OF DISAGREEMENT. BELOW NORMAL PRECIPITATION IS MOST LIKELY ALONG MOST
OF THE EASTERN SEABOARD. ABOVE NORMAL PRECIPITATION IS MOST LIKELY FOR WESTERN
AND NORTHERN ALASKA, AHEAD OF A PREDICTED TROUGH. BELOW NORMAL PRECIPITATION IS
MOST LIKELY FOR THE ALASKA PANHANDLE, UNDER A PREDICTED RIDGE.
THE OFFICIAL 6-10 DAY 500-HPA HEIGHT BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 8, 30% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED
ON DAY 8, 30% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8, 10% OF
TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8, AND 20% OF TODAY'S 0Z CANADIAN
ENSEMBLE MEAN CENTERED ON DAY 8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOUT AVERAGE, 3 OUT OF 5, DUE TO
GOOD AGREEMENT AMONG MODEL CIRCULATION FORECASTS, OFFSET BY SOME DISAGREEMENT
IN THE TEMPERATURE AND PRECIPITATION TOOLS.
8-14 DAY OUTLOOK FOR MAY 02 - 08 2018
TODAY'S WEEK 2 DYNAMICAL MODEL FORECASTS SHOW GREATER DISAGREEMENT THAN
FORECASTS FOR THE 6-10 DAY PERIOD. THE ECMWF ENSEMBLE MEAN PREDICTS WEAKER
POSITIVE 500-HPA ANOMALIES OVER THE EASTERN CONUS AND ELIMINATION OF NEGATIVE
500-HPA ANOMALIES OVER THE SOUTHWEST IN WEEK 2, RELATIVE TO THE 6-10 DAY
PERIOD. THE GEFS ENSEMBLE MEAN RAISES 500-HPA HEIGHTS OVER MUCH OF THE CONUS IN
THE 8-14 DAY PERIOD. THE ECMWF ENSEMBLE MODEL FORECASTS WERE GIVEN SLIGHTLY
GREATER WEIGHT IN THE MANUAL 500-HPA HEIGHT BLEND THAN THE GEFS OR CANADIAN,
DUE TO RECENT ANOMALY CORRELATION SKILL.
ABOVE NORMAL TEMPERATURES ARE MORE LIKELY OVER THE WESTERN CONUS IN WEEK 2,
COMPARED TO THE 6-10 DAY OUTLOOK, WITH DECREASING MODEL SUPPORT FOR A TROUGH
OVER THE REGION AND PREDICTED ZONAL FLOW. BELOW NORMAL TEMPERATURES ARE MOST
LIKELY FOR MUCH OF THE GREAT PLAINS IN WEEK 2, AS INDICATED BY THE
CONSOLIDATION OF REFORECAST-CALIBRATED TEMPERATURE FORECASTS FROM THE ECMWF AND
GEFS ENSEMBLES, AND CONSISTENT WITH EASTWARD PROGRESSION OF THE PREDICTED
TROUGH OVER THE CENTRAL CONUS. THE PROBABILITIES OF ABOVE NORMAL TEMPERATURES
HAVE INCREASED FOR THE SOUTHEAST IN WEEK 2 WITH PREDICTED LOCATION OF SOUTHERLY
FLOW AROUND SURFACE HIGH PRESSURE OVER THE REGION DURING THE FORECAST PERIOD.
ABOVE NORMAL TEMPERATURES ARE MOST LIKELY FOR ALASKA, WITH A FORECAST OF
RIDGING OVER THE STATE.
THE WEEK 2 PRECIPITATION OUTLOOK IS SIMILAR TO THE 6-10 DAY OUTLOOK, ALTHOUGH
AREAS OF ENHANCED PROBABILITIES OF ABOVE NORMAL PRECIPITATION IN THE WESTERN
CONUS HAVE DECREASED AS UNCERTAINTY IN THE PREDICTED CIRCULATION PATTERN HAS
INCREASED. ABOVE NORMAL PRECIPITATION REMAINS MOST LIKELY OVER PARTS OF THE
CENTRAL ROCKIES, AND THE AREA OF ENHANCED PROBABILITIES OF ABOVE NORMAL
PRECIPITATION OVER THE MISSISSIPPI VALLEY HAS SHIFTED SLIGHTLY EASTWARD, ALONG
WITH THE PREDICTED ENHANCED MOISTURE TRANSPORT.
THE OFFICIAL 8-14 DAY 500-HPA HEIGHT BLEND CONSISTS OF: 40% OF TODAY'S 6Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11, 40% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 11, AND 20% OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON
DAY 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO
A CHANGING CIRCULATION PATTERN AND GREATER UNCERTAINTY IN THE ENSEMBLE
FORECASTS, ALONG WITH SOME DISAGREEMENT IN THE TEMPERATURE AND PRECIPITATION
TOOLS.
FORECASTER: D COLLINS
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 1981-2010 BASE PERIOD MEANS FOR
TEMPERATURE...PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN THE CLIMATE
OUTLOOKS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON MAY
17.
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:
19590506 - 20070427 - 19570427 - 19770410 - 20060503
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:
20060502 - 19570427 - 19640406 - 19590506 - 20070425
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR APR 30 - MAY 04, 2018
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON N B NRN CALIF N N
SRN CALIF B A IDAHO N A NEVADA B A
W MONTANA B A E MONTANA B A WYOMING B A
UTAH B A ARIZONA B A COLORADO N A
NEW MEXICO N N N DAKOTA N A S DAKOTA N A
NEBRASKA A N KANSAS A N OKLAHOMA A A
N TEXAS A A S TEXAS A A W TEXAS A N
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A A LOUISIANA N A WISCONSIN A A
ILLINOIS A A MISSISSIPPI N A MICHIGAN A A
INDIANA A A OHIO A B KENTUCKY A B
TENNESSEE A B ALABAMA N B 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 N B S CAROLINA N B GEORGIA N B
FL PNHDL N B FL PENIN B B AK N SLOPE A A
AK ALEUTIAN A A AK WESTERN A A AK INT BSN N A
AK S INT N A AK SO COAST A N AK PNHDL A B
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR MAY 02 - 08 2018
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A N
SRN CALIF A N IDAHO A N NEVADA A N
W MONTANA A N E MONTANA B B WYOMING B N
UTAH A A ARIZONA A N COLORADO N N
NEW MEXICO A N N DAKOTA B B S DAKOTA B N
NEBRASKA B N KANSAS B N OKLAHOMA B A
N TEXAS B A S TEXAS N A W TEXAS N N
MINNESOTA B N IOWA B A MISSOURI B A
ARKANSAS N A LOUISIANA N A WISCONSIN B A
ILLINOIS N A MISSISSIPPI N A MICHIGAN N A
INDIANA N 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 B CONN A B RHODE IS A B
PENN A N NEW JERSEY A B W VIRGINIA A N
MARYLAND A B DELAWARE A B VIRGINIA A B
N CAROLINA A B S CAROLINA A B GEORGIA A B
FL PNHDL A B FL PENIN A B 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 B
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.
$$