909
FXUS06 KWBC 301900
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS, MD
300 PM EDT MON APRIL 30 2012
6-10 DAY OUTLOOK FOR MAY 06 - 10 2012
THE LATEST ENSEMBLE MEAN FORECASTS ARE IN FAIR AGREEMENT ON THE EXPECTED
500-HPA HEIGHT PATTERN FOR THE 6-10 DAY PERIOD OVER NORTH AMERICA. TROUGHS ARE
FORECAST OVER EASTERN CANADA, THE SOUTHWEST CONUS AND ALASKA, WHILE RIDGES ARE
ANTICIPATED OVER THE SOUTH-CENTRAL CONUS AND WESTERN CANADA. THE ECMWF
ENSEMBLES ARE QUICKER TO RAISE HEIGHTS OVER THE EAST-CENTRAL CONUS AND DEPICT A
DEEPER TROUGH OVER THE SOUTHWEST U.S.. RECENT OPERATIONAL SOLUTIONS OF THE GFS
AND ECMWF ARE IN FAIR AGREEMENT WITH THEIR RESPECTIVE ENSEMBLE MEANS BUT
DIFFERENCES ARISE IN THE HANDLING OF INDIVIDUAL SHORT WAVES.
THE GFS AND CANADIAN ENSEMBLE SPAGHETTI DIAGRAMS GENERALLY INDICATE MODERATE TO
LARGE SPREAD OVER MOST OF THE FORECAST DOMAIN WHILE THE ECMWF ENSEMBLE
SPAGHETTI DIAGRAMS DISPLAY LOW TO MODERATE SPREAD. THE PNA INDEX WHICH RECENTLY
HAS BEEN NEGATIVE IS FORECAST TO REMAIN NEGATIVE THROUGH DAY 7, BE CLOSE TO
ZERO AT DAY 10, AND BE WEAKLY POSITIVE AT DAY 14. THE AO INDEX WHICH RECENTLY
HAS TRANSFORMED FROM NEGATIVE TO WEAKLY POSITIVE IS FORECAST TO BE NEGATIVE AT
DAY 7 AND REMAIN NEGATIVE THROUGH DAY 14. TODAYS BLEND CHART INDICATES NEAR TO
BELOW NORMAL HEIGHTS OVER THE NORTHEAST AND SOUTHEAST CONUS, ALONG THE SOUTHERN
TIER OF THE COUNTRY, AND MOST OF ALASKA WHILE NEAR TO ABOVE NORMAL HEIGHTS ARE
ANTICIPATED ELSEWHERE.
THE RIDGE EXPECTED OVER THE SOUTH-CENTRAL CONUS LEADS TO ENHANCED PROBABILITIES
FOR ABOVE NORMAL TEMPERATURES OVER PARTS OF THE SOUTHEAST CONUS WHILE THE
TROUGH FORECAST OVER THE SOUTHWEST TILTS THE ODDS TO BELOW NORMAL TEMPERATURES
FOR THAT REGION. A RIDGE FORECAST TO BUILD OVER THE PACIFIC NORTHWEST FAVORS
ABOVE NORMAL TEMPERATURES THERE, WHILE ANOMALOUS SOUTHERLY FLOW LEADS TO
ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES OVER PARTS OF EASTERN
ALASKA. ANOMALOUS NORTHERLY FLOW FAVORS BELOW NORMAL TEMPERATURES OVER THE
ALEUTIANS AND PARTS OF NORTHWESTERN ALASKA.
THE TROUGH FORECAST OVER THE SOUTHWEST CONUS LEADS TO ENHANCED PROBABILITIES
FOR ABOVE MEDIAN PRECIPITATION OVER PARTS OF THE SOUTHWEST, SOUTHERN ROCKIES,
AND CENTRAL AND SOUTHERN PLAINS. BELOW NORMAL HEIGHTS LEAD TO ENHANCED
PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHEAST. RIDGES
OVER THE SOUTH-CENTRAL CONUS AND BUILDING ALONG THE WEST COAST TILTS THE ODDS
TO BELOW MEDIAN PRECIPITATION FOR PARTS OF THE MISSISSIPPI AND OHIO VALLEYS,
THE GREAT LAKES, AND THE WESTERN CONUS. ANOMALOUS SOUTHERLY FLOW LEADS TO
ENHANCED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION OVER SOUTHEAST ALASKA AND
THE ALASKA PANHANDLE. FLOW ON THE REAR SIDE OF A TROUGH LEADS TO ENHANCED
PROBABILITIES FOR BELOW MEDIAN PRECIPITATION OVER NORTHWESTERN ALASKA AND THE
ALEUTIANS.
TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 5 PERCENT OF TODAY'S OPERATIONAL 6Z
GFS CENTERED ON DAY 8...15 PERCENT OF TODAY'S 0Z GFS ENSEMBLE MEAN CENTERED ON
DAY 8...15 PERCENT OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 8...20
PERCENT OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8...5 PERCENT OF
TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 8...5 PERCENT OF YESTERDAY'S
OPERATIONAL 12Z ECMWF CENTERED ON DAY 7...25 PERCENT OF YESTERDAY'S 12Z
EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 7...AND 10 PERCENT OF YESTERDAY'S 12Z
CANADIAN ENSEMBLE MEAN CENTERED ON DAY 7.
MODEL OF THE DAY: YESTERDAYS 12Z ECMWF ENSEMBLE MEAN
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: BELOW AVERAGE, 2 ON A SCALE FROM 1
TO 5, DUE TO ONLY FAIR AGREEMENT AMONG THE ENSEMBLE MEANS AND THE FORECAST
TOOLS DERIVED FROM THEM.
8-14 DAY OUTLOOK FOR MAY 08 - 14 2012
DURING WEEK 2, THE ENSEMBLE MEAN SOLUTIONS GENERALLY LOWER HEIGHTS OVER THE
EASTERN CONUS AND RAISE HEIGHTS OVER THE SOUTHWEST. THE GFS-BASED ENSEMBLES ARE
THE MOST AMPLIFIED WITH THE RESULTING TROUGH OVER THE EASTERN PART OF THE
COUNTRY. THE 0Z AND 6Z OPERATIONAL GFS ARE EVEN MORE AMPLIFIED WITH THIS
TROUGH. THE ENSEMBLE SPAGHETTI DIAGRAMS GENERALLY INDICATE LOW TO MODERATE
SPREAD OVER THE EASTERN CONUS, AND MODERATE TO LARGE SPREAD OVER THE WESTERN
CONUS AND EASTERN PACIFIC.
TODAYS WEEK 2 BLEND CHART INDICATES NEAR TO BELOW NORMAL HEIGHTS OVER THE
EASTERN HALF OF THE CONUS, PARTS OF THE SOUTHERN PLAINS AND SOUTHWEST, AND
ALASKA, AND NEAR TO ABOVE NORMAL HEIGHTS OVER THE REMAINDER OF THE CONUS AND
THE WESTERN ALEUTIANS. AS HEIGHTS FALL OVER THE EASTERN CONUS, A COOLER PATTERN
IS EXPECTED THERE FOR WEEK 2. LIKEWISE RISING HEIGHTS OVER THE SOUTHWEST LEADS
TO A WARMER PATTERN FOR THAT PART OF THE COUNTRY. THE PRECIPITATION ANOMALIES
EXPECTED FOR WEEK 2 ARE NOT SUBSTANTIALLY DIFFERENT FROM THOSE EXPECTED FOR THE
6-10 DAY PERIOD, ALTHOUGH A DRIER PATTERN IS ANTICIPATED ACROSS THE NORTHERN
PLAINS AND UPPER MISSISSIPPI VALLEY DURING WEEK 2.
THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 10 PERCENT OF TODAY'S 0Z GFS
ENSEMBLE MEAN CENTERED ON DAY 11...10 PERCENT OF TODAY'S 6Z GFS ENSEMBLE MEAN
CENTERED ON DAY 11...20 PERCENT OF TODAY'S GFS SUPERENSEMBLE MEAN CENTERED ON
DAY 11...20 PERCENT OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY
11...10 PERCENT OF TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11...25
PERCENT OF YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10...AND 5
PERCENT OF YESTERDAY'S 12Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 10.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOUT AVERAGE, 3 ON A SCALE
FROM 1 TO 5, DUE TO FAIRLY GOOD AGREEMENT AMONG THE ENSEMBLE SOLUTIONS AND FAIR
AGREEMENT AMONG THE FORECAST TOOLS.
FORECASTER: RANDY SCHECHTER
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:
19990424 - 19640509 - 19540412 - 20070504 - 19900422
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:
19990423 - 20070504 - 19640509 - 19540412 - 19900421
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR MAY 06 - 10 2012
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A B
SRN CALIF N B IDAHO A B NEVADA A B
W MONTANA A B E MONTANA N N WYOMING N N
UTAH N B ARIZONA B B COLORADO N A
NEW MEXICO B A N DAKOTA N N S DAKOTA N N
NEBRASKA N A KANSAS N A OKLAHOMA N A
N TEXAS N N S TEXAS B N W TEXAS B A
MINNESOTA N N IOWA N N MISSOURI N N
ARKANSAS A B LOUISIANA A N WISCONSIN N N
ILLINOIS N B MISSISSIPPI A N MICHIGAN N B
INDIANA N B OHIO N B KENTUCKY A B
TENNESSEE A N ALABAMA A A NEW YORK N N
VERMONT N N NEW HAMP N N MAINE N N
MASS N N CONN N N RHODE IS N N
PENN N N NEW JERSEY N N W VIRGINIA N N
MARYLAND N N DELAWARE N N VIRGINIA N N
N CAROLINA A N S CAROLINA A A GEORGIA A A
FL PNHDL A A FL PENIN N N AK N SLOPE B N
AK ALEUTIAN B B AK WESTERN B N AK INT BSN A N
AK S INT N A AK SO COAST N A AK PNHDL N A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR MAY 08 - 14 2012
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 A B E MONTANA A B WYOMING A N
UTAH A N ARIZONA A B COLORADO A A
NEW MEXICO N A N DAKOTA A B S DAKOTA N B
NEBRASKA N N KANSAS N N OKLAHOMA B B
N TEXAS B B S TEXAS B N W TEXAS B A
MINNESOTA N B IOWA N B MISSOURI N B
ARKANSAS N B LOUISIANA N N WISCONSIN B B
ILLINOIS N B MISSISSIPPI N N MICHIGAN B B
INDIANA N B OHIO B B KENTUCKY N B
TENNESSEE N N ALABAMA N N NEW YORK B N
VERMONT B N NEW HAMP B N MAINE N N
MASS B N CONN B N RHODE IS B N
PENN B N NEW JERSEY B N W VIRGINIA N N
MARYLAND B N DELAWARE B N VIRGINIA N N
N CAROLINA N A S CAROLINA N A GEORGIA N A
FL PNHDL B A FL PENIN B A AK N SLOPE N N
AK ALEUTIAN B B AK WESTERN B N AK INT BSN N N
AK S INT N 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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